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Identifying and managing the possible effects of CO2 storage on the
environment
Master Thesis (30EC)
Linda H. Hoekstra
10345051
May 16, 2014
Master: Earth Sciences – Environmental Management
Examiner: B. Jansen
Co-assessor: M.J.C. Visser
Daily supervisors: H. Gaasbeek (TNO) and T. Wildenborg (TNO)
Period: November 2013 - May 2014
Research institute: University of Amsterdam & TNO
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Abstract The implementation of the geological storage of CO2 as a climate mitigation measure raises
questions on possible safety aspects for the environment. This study resulted in the identification of
possible effects when CO2 leaks from a storage reservoir and migrates into the environment.
Subsequently, possible monitoring and mitigation measures for the effects to the environment were
described. To show the relations between the different subjects of this study, the results are placed
in a bow-tie framework. A bow-tie framework (see below) is a graphical tool to illustrate an accident
scenario, starting from accident causes and ending with the effects of the accident.
This study focused on the identification of the different aspects of the right side of the bow-tie
framework, i.e. the consequences of migration of CO2 out of a storage reservoir.
As part of the permitting process, operators are required to develop, amongst others, an
Environmental Impact Assessment, a Monitoring Plan, and a Corrective Measure Plan.
With regard to the Environmental Impact Assessment, four main physical consequences have been
identified: accumulation of gaseous CO2 in the atmosphere at the surface, accumulations of liquid,
hydrated or dissolved CO2 in the water column, accumulations of gaseous CO2 in the soil, or
dissolution of CO2 in the groundwater or in seabed pore fluids. These four physical consequences
can lead to numerous environmental impacts.
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To prevent the migration of CO2 from causing the physical consequences to occur, a shallow
monitoring plan has to be developed. This study resulted in some recommended approaches for
monitoring measures:
Early detection of CO2 leakage is a priority and since the most realistic leakage pathway is
identified as around the wells, monitoring plans should focus on these locations
All the identified physical consequences can be detected with the use of ecosystem
monitoring, so this should be part of the shallow monitoring plan
Monitoring techniques should be applied in combination with complementing techniques
(ecosystem monitoring in combination with a technique that verifies the cause of the
detected ecosystem irregularities)
Shallow monitoring should be applied to detect migration of CO2, physical consequences,
and environmental impacts
When migration of CO2 is detected by monitoring techniques, action should be taken to prevent the
consequences from occurring:
1. The first step of the developed mitigation procedure aims to stop further leakage of CO2 from the storage reservoir.
2. The first step has been unsuccessful and physical consequences do take place, then the mitigation measures as described in the second step will aim at being successful in removing the physical consequences before they can cause the environment to be affected.
3. If the environment does experience impact a last mitigation measure step is described which aims at restoring the environment to its original state.
The developed bow-tie provides a useful framework for risk assessments of effects from CO2
storage. For example, it could be used to develop a tool where all physical consequences,
environmental impacts, monitoring techniques and mitigation measures for the environment are
implemented. Input could be a selected environmental impact. The output of this tool could then
result in recommendations for monitoring techniques and mitigation measures that are linked to the
physical consequence that causes this environmental impact.
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Table of content Abstract ................................................................................................................................................... 3
Table of content ...................................................................................................................................... 5
Definitions & abbreviations .................................................................................................................... 7
Preface .................................................................................................................................................... 9
Chapter 1 Introduction ......................................................................................................................... 10
1.1 Climate change ............................................................................................................................ 10
1.2 Carbon Capture and Storage ....................................................................................................... 11
1.3 CO2 storage ................................................................................................................................. 13
1.4 Current CO2 storage projects ...................................................................................................... 14
1.5 CO2 leakage ................................................................................................................................. 15
1.6 Research aim and questions ....................................................................................................... 15
1.7 Research approach...................................................................................................................... 16
1.8 Outline of the report ................................................................................................................... 18
Chapter 2 Consequences ...................................................................................................................... 20
2.1 Consequences of CO2 leakage to the shallow subsurface and atmosphere ............................... 21
2.2 Environmental impacts ............................................................................................................... 23
Chapter 3 Monitoring techniques ......................................................................................................... 32
3.1 Monitoring CO2 for the shallow subsurface and atmosphere .................................................... 32
3.2 Monitoring Techniques as described in CCS Projects ................................................................. 33
3.3 Proposed monitoring requirements ........................................................................................... 35
3.4 Proposed monitoring techniques ............................................................................................... 35
Chapter 4 Mitigation measures ............................................................................................................ 37
4.1 Mitigation procedure .................................................................................................................. 37
4.2 Step 1. Preventing further leakage of CO2 .................................................................................. 37
4.3 Step 2. Removal of the physical consequences .......................................................................... 40
4.4 Step 3. Restoring the impacted environments ........................................................................... 44
Chapter 5 Synthesis............................................................................................................................... 47
5.1 The bow-tie framework .............................................................................................................. 47
5.2 Evaluation of the TNO tools for risk evaluation and monitoring of CO2 leakage ....................... 50
Chapter 6 Discussion ............................................................................................................................. 53
6.1 Overall ......................................................................................................................................... 53
6.2 Synthesis ..................................................................................................................................... 53
6.3 Consequences ............................................................................................................................. 54
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6.4 Reactive barriers ......................................................................................................................... 54
6.5 Legal Aspects ............................................................................................................................... 55
Chapter 7 Conclusions and recommendations for further research .................................................... 56
7.1 Conclusions ................................................................................................................................. 56
7.2 Recommendations for further research ..................................................................................... 56
References ............................................................................................................................................ 58
Appendices ............................................................................................................................................ 67
Appendix 1 Legal aspects .................................................................................................................. 67
Appendix 1B ...................................................................................................................................... 75
Appendix 2 ........................................................................................................................................ 76
Appendix 3A ...................................................................................................................................... 77
Appendix 3B ...................................................................................................................................... 79
Appendix 3C ...................................................................................................................................... 80
Appendix 5 ........................................................................................................................................ 82
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Definitions & abbreviations All-in-one permit for physical aspects = Omgevingsvergunning
Atmosphere = the area where the living environment comes into contact with the atmosphere
Background CO2 = CO2 naturally derived from the atmosphere and biologically mediated oxidation of
organic carbon (respiration)
Bow-tie = a graphical manner to illustrate an accident scenario, starting from accident causes and
ending with its consequences
CCS = Carbon Capture and Storage
CO2 = Carbon Dioxide
Consequences = direct effects as a result of CO2 migration into the shallow subsurface and
atmosphere
EIA = Environmental Impact Assessment
Environmental damage = damage to protected species or natural habitats; damage and pollution of
the groundwater; any form of soil contamination
Environmental Impact = Impacts to onshore and offshore receptors caused by the consequences of
the shallow subsurface and the atmosphere
Environmental Management Act = Wet Milieubeheer
FEPs = Features, Events and Processes
General Environmental Conditions Act = Wabo; Wet algemene bepalingen omgevingsrecht;
Groundwater = this refers to the groundwater close to the surface, seabed pore fluids or to deeper
groundwater aquifers potentially used for drinking water withdrawal
Impact = consequences of CO2 leakage with tangible effects on plants, animals, humans, and marine
biota
IPCC = Intergovernmental Panel on Climate Change
Mitigation = measures taken to avoid, minimize or remedy adverse consequences of CO2 leakage
and migration into the shallow subsurface and atmosphere or impacts on the environment
OSPAR Convention = Convention for the Protection of the Marine Environment of the North-East
Atlantic
Receptor = an environmental unit that is potentially impacted by consequences
ROAD = Rotterdam Opslag en Afvang Demonstratieproject; Rotterdam Storage and Capture
Demonstration project
Shallow subsurface and atmosphere = combined compartments of soil, groundwater, surface water,
and atmosphere
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Time-lapse mode = a number of repeated monitoring surveys, enabling to map changes through
time
TNO = Netherlands Organization for Applied Scientific Research
UNFCCC = United Nations Framework Convention on Climate Change
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Preface This study is carried out by Linda H. Hoekstra in the context of a Master Thesis Project of the master
Earth Sciences (track: Environmental Management) at the University of Amsterdam. The study is
examined by dr. B. Jansen and co-assessed by mr. M.J.C. Visser, and carried out for the period
November 2013 to May 2014 at TNO (Netherlands Organization for Applied Scientific Research). The
supervisors within TNO are dr. T. Wildenborg and H. Gaasbeek.
The topic of this study evolved from a combination of personal interest and suggestions from TNO.
The personal interest is derived from the debate about the climate change induced by the oil- and
gas industry, and the ambition to find the connection of this debate with environmental and societal
significance. Since the oil- and gas industry is one of the main causes in the anthropogenic increase
in greenhouse gases a solution in reducing the greenhouse gas emissions can also be found there.
Carbon capture and storage is a technology that is acknowledged to be a key measure in realizing
deep cuts in CO2 emissions. Because of personal interest, human concern and permitting
requirements this study will look into the effects of CO2 leakage and migration from storage sites
into the living environment and into the management of these effects.
TNO created a tool that supports the risk evaluation and monitoring of CO2 leakage. This tool
includes a database of features, events and processes (so called FEPs) that take place in the different
release scenarios (CO2 leakage through the seal, along a fault, or along a well). So far, this tool
concentrates on the possible causes of CO2 leakage and does not take into account what happens to
the surrounding environment when CO2 release scenarios take place. Amongst others, the outcome
of this thesis aims at providing suggestions for the functionality of the TNO tool based on the
consequences of CO2 leakage to the environment.
In the spring of 2014 a study funded by the European Union commences and will be coordinated by
TNO. The study is called Mitigation and Remediation of CO2 Leakage (MiReCOL) and aims to develop
new mitigation and remediation techniques. This thesis could be a useful addition for a part of the
MiReCOL Project.
I would like to thank in particular dr. B. Jansen, mr. M.J.C. Visser, dr. T. Wildenborg, and H. Gaasbeek
(and others from within TNO) for their guidance and constructive reviews to previous draft versions
of this study.
Utrecht,
May 16, 2014
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Chapter 1 Introduction
1.1 Climate change Numerous observations strengthen the evidence of abnormal changes in the climate system over
the past centuries with potentially devastating effects on the human environment. The monitoring
of average air and surface temperatures has shown global increases of 0.6 ± 0.2°C over the 20th
century. Other observed changes are global increases in average sea levels (between 10 and 20
centimeters in the 20th century), acidification of the oceans, decrease of snow cover of about 10%
since the late 1960s, and a retreat of the mountain glaciers in the non-polar regions (AMESCO, 2007;
IPCC, 2013). Climate change is also reflected in unprecedented changes in the frequency, intensity,
spatial extent, duration and timing of extreme weather events (IPCC, 2012).
In table 1.1 a comparison of observed effects of climate change globally and for the Dutch situation
is given. In the Netherlands, the observed temperature increase is 0.2°C higher than the global
average temperature. Furthermore an increase in average winter precipitation has been observed
(Mooij et al., 2005). Since 1900, the sea level in the Netherlands has increased by 20 cm caused by
the melting of ice, expansion of seawater and subsidence (Bresser et al., 2005).
TABLE 1.1 COMPARISON OF THE GLOBAL TEMPERATURE AND SEA LEVEL INCREASES TO THE NETHERLANDS
Global The Netherlands
Temperature rise since 1900 0.6 ± 0.2°C 0.8°C
Sea level rise since 1900 10-20 cm 20 cm
The Intergovernmental Panel on Climate Change of the United Nations (IPCC) has announced in their
latest Assessment Report (September 2013) that it is extremely likely (95% certain) that the warming
is caused by anthropogenic increases in greenhouse gas concentrations combined with other
anthropogenic forcings (IPCC, 2013).
Carbon dioxide (CO2) is one of those greenhouse gases. Figure 1.1 shows the concentration of CO2 in
the atmosphere over the past millennium. It has increased rapidly since the industrial revolution of
FIGURE 1.1 ATMOSPHERIC CONCENTRATIONS OF CO2 (BASED ON IPCC, 2007)
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the nineteenth century (IPCC, 2007). Fossil fuel combustion (with a small contribution from cement
manufacture) is responsible for more than 75% of the anthropogenic increase of CO2 emissions since
the industrial revolution (Denman et al., 2007).
A general concern on climate change emerged due to the coincidence of the observed climate
changes together with the increase of CO2 concentrations in the atmosphere. Limiting the severity of
potential impacts of climate change requires stabilization of atmospheric CO2 concentrations (IPCC,
2007).
The United Nations Framework Convention on Climate Change (UNFCCC) used the first IPCC report
(IPCC, 1990) as a framework that led to a global climate treaty in 1992 with the aim to limit average
global temperature increases and the resulting climate change (UNFCCC, 2014). This treaty extended
to the Kyoto protocol in 1997 with more concrete agreements between industrialized countries on
the reduction of greenhouse gas emissions with 5.2% (AMESCO, 2007; Harmelink, 2013). The Kyoto
protocol again led to the development of the 2020 climate and energy package from the European
Union which is a binding legislation with the aim to drastically reduce the amount of greenhouse
gases emitted into the atmosphere. A long-term goal of the European Union is to switch to a fossil
fuel independent energy sector (IEA, 2008; ec.europe.eu, 2014).
It is recognized that this transition in the energy system comes with great challenges. Possibly the
best way is to bridge the transition by means of emission mitigation options including energy
conservation, application of renewable energy, a switch to low carbon fuels, and nuclear power. For
the midterm Carbon Capture and Storage (CCS) is considered to be the key technology to realize
deep cuts in greenhouse gas emissions. All climate mitigation options will probably have to be
implemented as a combined effort (AMESCO, 2007).
1.2 Carbon Capture and Storage
CCS as a climate mitigation option is a technique where CO2 is captured at an emission point, and is
separated from the combustion flue gas. The CO2 is transported to a storage location where it is
injected into stable deep geological formations (e.g. IPCC, 2005). Figure 1.2 shows a simplified
overview of a CCS chain.
CO2 capture is most effective at large emission sources, like for example fossil fuel power plants, fuel
processing plants and other industrial plants. The four basic systems to capture CO2 are: Capture
from industrial process streams, post-combustion capture, oxy-fuel combustion capture, and pre-
combustion capture. The systems are briefly explained in table 1.2.
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FIGURE 1.2 SCHEMATIC OVERVIEW OF A STANDARD CCS CHAIN (FROM CO2CRC.COM.AU, 2011).
TABLE 1.2 CO2 CAPTURE SYSTEMS (IPCC, 2005)
Capture from industrial process streams
Capturing CO2 from industrial process streams is done in more ways. Examples are by the purification of natural gas and production of hydrogen-containing synthesis gas for the manufacture of ammonia, alcohol, and synthetic liquid fuels.
Post-combustion capture
Flue gases are formed by combustion of fossil fuels. These flue gases are subsequently transported through equipment which separates most of the CO2. The remainder of the flue gases is discharged to the atmosphere.
Oxy-fuel combustion capture
When nearly pure oxygen is used for combustion of fossil fuels, the flue gas that will result consists mainly of CO2 and H2O. By cooling, the CO2 can be separated from the H2O.
Pre-combustion capture
Pre-combustion capture is done before the combustion of a fuel. The fuel will first react with oxygen or air and steam to become a flue gas composed of carbon monoxide and hydrogen. Subsequently this composition will react with steam in a catalytic reactor to produce CO2 and more hydrogen. The CO2 is then separated by a physical or chemical absorption process.
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After the capture of CO2 it can be transported as a gas, liquid, or solid. The more compressed the CO2
is the larger quantities can be transported. The solidification of CO2 requires a lot of energy and is
therefore not yet a desirable large-scale option. Transport of CO2 as a compressed dense gas is a
more realistic solution for pipeline systems. In the pipelines CO2 will be transported under a pressure
above 8 MPa. When it has to be transported over large overseas distances, transport by ship is
another option. In this case CO2 will be compressed to a liquefied gas at a typical pressure of 0.7
MPa and at low temperature (-55 to -50°C) (IPCC, 2005). Before CO2 will be injected into a storage
field it will preferably be pressurized to a so-called supercritical condition. The supercritical condition
for CO2 is at pressures above 7.39 MPa and temperatures above 31.1°C (IPCC, 2005).
1.3 CO2 storage The geological storage of CO2 as a greenhouse gas mitigation option can be done in a variety of
subsurface reservoirs, e.g.; oil fields, depleted gas fields, deep coal seams, saline formations, and
other options as is shown in figure 1.3 (IPCC, 2005). Studies of oil and gas fields indicate that
hydrocarbons and other gases, including CO2, can remain trapped for millions of years (e.g.
Bradshaw et al., 2005).
FIGURE 1.3 DEEP UNDERGROUND GEOLOGICAL STORAGE OPTIONS (IPCC, 2005)
Possible storage sites have to meet the following criteria: there has to be an adequate porosity and
thickness for sufficient storage capacity, adequate permeability for injectivity, a suitable sealing
caprock, and a stable geological environment in order to ensure the reliability of the storage site.
The injection of CO2 in the subsurface has been done for many years on a relative small-scale in
order to dispose unwanted chemicals or by-products from petroleum production, or to enhance
and/or recharge production of oil and gas. CO2 injection for enhanced oil and gas recovery can
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increase the exploitation life time of a gas field with several years (IPCC, 2005). For example, the
production of one of the biggest natural gas fields in the world (which is located in the North of the
Netherlands at Slochteren) can be extended with a few years by applying CO2 injection. Model
calculations by the NAM have estimated a total extra natural gas production of 35 billion Nm3,
thanks to CO2 injection in depleted gas fields in Slochteren (AMESCO, 2007; Whaley, 2009).
Thanks to natural gas and oil production in the past forty years, there is good knowledge of the
Dutch subsurface. Once gas fields are depleted, they could be used for CO2 storage with a total
storage capacity of 10,100 Mton. Deep aquifers, depleted oil fields and deep coal fields provide
additional potential storage capacity of roughly 1,150 Mton CO2 (Ecofys, 2007). The potential of CCS
in the Netherlands is sufficient to reduce its CO2 emissions by 60% to 80% by 2050 (AMESCO, 2007).
1.4 Current CO2 storage projects Currently a number of pilot and commercial CCS projects exist, which are in the preparation or
operation phase. Four CCS projects are selected, which will be further described and used in this
thesis: the Barendrecht project, the In Salah project, the ROAD project, and the Sleipner project. An
overview of these four projects is shown in table 1.3.
TABLE 1.3 FOUR SELECTED CCS PROJECTS. THERE ARE TWO ONSHORE PROJECTS SELECTED OF WHICH ONE IN
IN PRODUCTION AND TWO OFFSHORE PROJECTS, ALSO OF WHICH ONE IS IN PRODUCTION.
Onshore Offshore
Netherlands – not (yet) in production Barendrecht ROAD
International – in production In Salah Sleipner
Barendrecht project, the Netherlands
The Barendrecht project was a national project to realize a CO2 storage pilot for storing about 10
million tonnes of CO2 onshore over a period of 25 years (Kuijper, 2009). The organization was
executed by Shell, but on November 2010 definitely canceled by the government. The reason was a
complete lack of local support and the idea that other pilot projects outside the Netherlands already
provide much of the technical aspects, so no further demonstration of the technique is required
(Spence, 2012).
In Salah project, Algeria
The In Salah project is an industrial-scale CO2 storage project in Algeria. It has been in operation
since 2004 and captures CO2 from the production stream. Up to 2010 over 3 million tonnes of CO2
have been securely injected into a saline formation at about 1,850 meters of depth (Mathieson et
al., 2010).
ROAD project, the Netherlands
The ‘ROAD-project’ (‘Rotterdam Opslag en Afvang Demonstratieproject’) is a project to demonstrate
the technical and economic feasibility of a large-scale integrated CCS chain. CO2 is planned to be
captured at a coal-fired power plant in the port of Rotterdam and will be transported to and injected
in a depleted gas field 20 kilometers off the coast. The operation of this CCS-chain is planned to start
operating in 2015/2016 (Jonker, 2013), provided that the project can be completely financed.
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Sleipner project, Norway
At the Sleipner gas field in the Norwegian offshore region, CO2 from natural gas production is stored
in an aquifer, the Utsira Formation, 800 meters below the North Sea seabed. The decision to store
the CO2 was based on willingness to try out a new technology and the CO2 tax incentive (Solomon,
2007; Hagen, 2012). The injection started in 1996, and is operated by Statoil and the Sleipner
partners (Chadwick et al., 2006).
1.5 CO2 leakage All CO2 storage sites are carefully selected and characterized in order to minimize the possibility of
leakage. Leakage of CO2 is unwanted for a number of reasons. For example, it could nullify the
greenhouse gas reduction goals once leakage leads to migration into the atmosphere, but it could
potentially also lead to adverse effects on the environment. Because public concerns and because of
permitting needs, which require for example an Environmental Impact Assessment, an overview of
consequences and impacts of CO2 leakage is desirable. To understand where consequences and
environmental impacts are likely to occur, it is important to identify the most realistic leakage
pathways.
Previous research has identified three main potential leakage pathways. According to a study by
Yavuz et al. (2008) leakage can occur through the seal, along a fault or along a well, as indicated in
figure 1.4 (i.e. IPCC, 2005; Yavuz et al., 2008; Paulley et al., 2013). Firstly, leakage through the seal
can occur by high pressure of CO2 that fractures the seal (figure 1.4A) or via a possible gap in the seal
(figure 1.4B). Secondly CO2 could escape from the reservoir along a permeable fault (figure 1.4C), or
it can induce/reactivate a fault (figure 1.4D). Finally CO2 can also escape through a poorly installed or
abandoned well (figure 1.4E).
FIGURE 1.4 POTENTIAL LEAKAGE PATHWAYS FROM A STORAGE RESERVOIR (BASED ON CO2CRC.COM.AU,
2011)
In the most extreme circumstances, releases of the order of 100 tonnes a day could occur if a closed
well completely fails, but it is more likely that, if CO2 leakage occurs, releases will be a few hundred
tonnes a year (Paulley et al., 2013). It is estimated that the affected area with significant effects on
the environment will not be bigger than between the 1.000 m2 and 30.000m2 (Wildenborg et al.,
2003). Since the estimated affected area is significant, CO2 leakage is an important topic to perform
further research on.
1.6 Research aim and questions The research questions which will be addressed in this master thesis research relate to the
consequences of CO2 leakage for the environment.
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The main research aim is to identify possible effects from CO2 storage to the shallow subsurface and
atmosphere and to describe the management options for preventing or reducing the effects.
To successfully reach this aim the following research questions have been formulated:
What can be the physical consequences of CO2 leakage from a storage reservoir for the shallow subsurface and atmosphere?
Which environmental impacts can be caused by the physical consequences that occurred due to CO2 leakage?
What monitoring techniques have been developed to detect CO2 migration and accumulation in the shallow subsurface and atmosphere?
Which monitoring techniques can be recommended for the monitoring of the consequences to the shallow subsurface and atmosphere?
What mitigation measures are developed to stop the leakage of CO2? What mitigation measures are developed to reduce or remove the consequences of CO2
leakage? What mitigation measures are applicable to restore the impacted environment?
How can all the information together be compiled in a bow-tie framework? How can the bow-tie contribute to future work on risks of CO2 leakage? How can the TNO tool be improved with the results from this research?
A special Appendix will go into some legal aspects that are relevant when dealing with the threat of
CO2 migration from a storage reservoir entering the environment.
What are the regulatory requirements for the treatment of threats to the environment caused by CO2 storage?
1.7 Research approach The methodology of this research is mainly based on an extensive scientific literature review. The
results of this research are placed in a schematic framework that links the different subjects. The
framework that will be used is based on the bow-tie concept.
Bow-tie concept
The bow-tie concept represents the main guiding risk management principle in this research. The
bow-tie is a graphical representation of threats and consequences related to a main hazardous
event, the so called head event. It starts with identifying the threats and hazards of an event and
ends with the consequences (Khakzad et al., 2012). As schematically shown in figure 1.5 different
hazards and threats can lead to the main hazardous event or the head event. The head event can
lead to consequences. The head event can be prevented by implementing proactive barriers and by
implementing reactive barriers the Head event can be mitigated (Rausand, 2011).
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FIGURE 1.5 SCHEMATIC REPRESENTATION OF A BOW-TIE MODEL. HAZARDS AND THREATS LEADING TO THE
HEAD EVENT, WHICH LEADS TO CONSEQUENCES (BASED ON RAUSAND, 2011)
To produce a bow-tie, a head event has to be identified, and the related threats and consequences
have to be chosen. The bow-tie approach is nicely illustrated with the example of a tiger in a cage
(Bowtiepro.com, 2014). The Head event is when the tiger would escape from the cage. The threats
causing the tiger to escape are for example that the cage is not strong enough or that the gate is left
open. The consequences resulting from the escaping tiger could be that it kills a member of the
public or the tiger will be killed.
Pro-active measures preventing the tiger to escape could be that the gate is designed to
international standards and inspected. To prevent the tiger to escape while the gate is left open
could be done by installing a self-closing gate or install a gate alarm.
Reactive measures to mitigate the tiger to kill a member of public a search plan should be
established and a dart gun has to be present. Mitigating the loss of the tiger can be done by being
properly insured.
Figure 1.6 gives the schematic overview of the bow-tie for the risk of an escaping tiger.
FIGURE 1.6 BOW-TIE MODEL FOR THE ESCAPING TIGER EVENT (BOWTIEPRO.COM, 2014)
Key assumptions and definitions
A study by Van Eijs et al. (2011) used the bow-tie diagram to visualize the head event ‘migration of
CO2 out of the containment of the target storage reservoir’ (figure 1.7). The FEP database from TNO
served to analyze the threats which formed the basis of the threat assessment (Van Eijs et al., 2011).
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FIGURE 1.7 BOW-TIE FRAMEWORK FOR THE HEAD EVENT: MIGRATION OF CO2 OUT OF CONTAINMENT (BASED
ON VAN EIJS ET AL., 2011)
The focus for this research is the consequences site of the bow-tie diagram by the study from Van
Eijs et al. (2011). For the identification of the separate bow-tie parts it is assumed that leakage of
CO2 from the storage reservoir does occur and that the CO2 will migrate into the soil, groundwater,
surface water, or atmosphere. With groundwater this research will refer to the groundwater close to
the surface, seabed pore fluids or to deeper fresh groundwater aquifers potentially used for drinking
water withdrawal. With atmosphere this research will refer to the area where the living
environment comes into contact with the atmosphere. From now on in this report the combination
of soil, groundwater, surface water, and atmosphere will be defined as the shallow subsurface and
atmosphere.
This research will identify physical consequences that result from CO2 ending up in the shallow
subsurface and atmosphere. These physical consequences subsequently result in tangible
environmental impacts. The physical consequences and environmental impacts together are within
the scope of consequences as identified in a general bow-tie framework. The reactive barriers will be
identified in this study as the monitoring techniques and mitigation measures.
The bow-tie framework from figure 1.7 has a guiding role for presenting and discussing the results
from the literature research that will be carried out in this research.
1.8 Outline of the report Chapter 2 ‘Consequences’ starts with identifying the physical consequences that can occur to the
shallow subsurface and atmosphere when CO2 leaks from an underlying storage reservoir. The
chapter will subsequently give an overview of resulting environmental impacts.
Chapter 3 ‘Monitoring techniques’ describes monitoring techniques that will be needed to detect
the consequences to the shallow subsurface and atmosphere.
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Chapter 4 ‘Mitigation measures’ will describe measures that will mitigate the consequences and aim
at preventing and/or mitigating the environmental impacts.
Chapter 5 ‘Synthesis’ will illustrate and describe the relations between the different chapters of this
study in a bow-tie framework. It will subsequently explain how this study can contribute to further
research into managing the effects of CO2 storage.
Chapter 6 ‘Discussion’ critically evaluates where the knowledge gaps of this study are and where
more research is needed.
In Chapter 7 ‘Conclusions & Recommendations’ the main conclusions from this thesis will be drawn.
Subsequently recommendations will be given on the aspects where more research is needed.
Appendix 1 ‘Legal Considerations’ will give a sneak peek into some legal regulations that are
relevant when dealing with the threat of CO2 migration from a storage reservoir entering the shallow
subsurface and atmosphere. A framework will be presented with the main important European
Directive and some national regulations that should be taken into account when considering the
permitting requirements for CO2 storage.
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Chapter 2 Consequences This chapter aims to define the consequences of CO2 leakage from a geological storage reservoir. An
overview of consequences of CO2 leakage is desirable because of public concerns and because a
legal requirement which requires the development of an Environmental Impact Assessment (see
Appendix 1). In particular this chapter will describe potential physical consequences and resulting
environmental impacts that can be the result leakage of CO2 from a storage site and subsequent
migration of CO2 into the shallow subsurface and atmosphere.
Research Questions:
What can be the physical consequences of CO2 leakage from a storage reservoir for the shallow subsurface and atmosphere?
Which environmental impacts can be caused by the physical consequences that occurred due to CO2 leakage?
In this chapter direct physical effects as a consequence of CO2 leakage in the shallow subsurface and
atmosphere will be defined as ‘Physical consequences’. These physical consequences are highly
dependent on site-specific characteristics like the chemical composition of the subsurface. For the
physical consequences no distinction will be made between onshore and offshore.
The identified physical consequences can cause effects to onshore and offshore impact receptors
living in the environment. These effects are defined as ‘Environmental impacts’.
Properties of CO2
CO2 naturally occurs in the atmosphere in a low and harmless concentration (currently about
400ppm). In this concentration the substance poses no harm to humans, animals or vegetation. It is
even essential for plants for photosynthesis. The gas is non-flammable, colorless, tasteless, and
generally considered odorless in low concentrations (IPCC, 2005).
There are several processes by which naturally occurring CO2 can be emitted into the atmosphere,
especially in volcanic environments (Holloway et al., 2005). Research into these areas will help in
defining impacts of elevated CO2 concentrations to the environment. There have been serious
incidents in the past in volcanic areas, with rapid emissions of large masses of CO2 with major losses
of life. Appendix 2 will go into an example of such an incident. These incidents from natural sources
have occurred under very exceptional circumstances, but due to these events, serious concerns have
been expressed about the possible deployment of CO2 storage (Holloway et al., 2005).
A study by Oldenburg et al. (2004) demonstrated different release scenarios from the vadose zone
into the atmosphere. It showed that large releases of CO2 are easily diluted by atmospheric mixing
rates before they can build up to hazardous concentrations at the surface. If such large amount of
CO2 into the environment can be released from CO2 storage sites really depends on the size and rate
of the release. Nevertheless, this study also showed that for the same high release scenario from the
vadose zone high concentrations of CO2 can build up in the soil exceeding concentrations that can
pose stress on vegetation (Oldenburg et al., 2004; Benson, 2005). Therefore, it could also be
imagined that when CO2 is released into a confined space like a basement, the concentration can
also build up to hazardous concentrations for humans.
21
2.1 Consequences of CO2 leakage to the shallow subsurface and atmosphere If CO2 leaks out of the storage reservoir it can end up in the shallow subsurface or atmosphere. The
flux of CO2 will probably vary with coarseness of soil particles and will probably be higher for sandy
soils and lower for clay due to differences in permeability of the different soil types (AMESCO, 2007;
Paulley et al., 2013). Figure 2.1 shows the identified consequences of CO2 leakage.
Two main modes of CO2 leakage can be discerned: a sudden, large release of CO2 or a gradual low
concentration release of CO2. Both can have a different environmental impact on organisms as will
be described in paragraph 2.2.
FIGURE 2.1 THE PHYSICAL CONSEQUENCES OF CO2 LEAKAGE LEADING TO ENVIRONMENTAL IMPACTS. THE
ENVIRONMENTAL IMPACTS WILL BE FURTHER DESCRIBED IN PARAGRAPH 2.2
The following physical consequences of CO2 leakage can occur:
Accumulations of gaseous CO2 in the atmosphere
When CO2 leaks straight into the atmosphere it can accumulate at the surface where it can cause a
threat for the environment, especially when it accumulates in a confined space and thereby is not
able to diffuse into higher atmospheric layers (Pearce et al., 2004).
Accumulations of liquid, hydrated or dissolved CO2 in the water column
CO2 leaking out of a reservoir may accumulate in the water column of a lake or sea in a liquid,
hydrated or dissolved condition. Appendix 2 gives an example of a naturally occurring gaseous CO2
accumulation at the bottom of a lake in Cameroon.
Accumulations of gaseous CO2 in the soil
It is also possible that the CO2 leaked from the storage reservoir will accumulate in a gaseous phase
in the soil below fine-grained seals that are able to trap migrated CO2 (Pearce et al., 2004).
Dissolution of CO2 in the groundwater or in seabed pore fluids
The fourth physical consequence of CO2 leakage is the dissolution of CO2 in the groundwater or in
seabed pore fluids. Potable water aquifers are also taken into account, since effects of the potable
water can have an impact on humans. The possible processes of CO2 dissolving in water will be
further explained.
22
Water-CO2 interaction
When CO2 comes in contact with water it can cause changes in the chemistry of the water which
potentially leads to environmental impacts. Different mechanisms can occur caused by the
dissolution of CO2 in water which are summarized in figure 2.2. When a CCS project is planned to be
carried out, in-depth research must be done on the variations in the environment of the area and
the sediment types and associated compounds, since potential consequences really depend on site-
specific characteristics. In this paragraph some examples of possible effects are described based on a
few case studies.
FIGURE 2.2 CONSEQUENCES OF DISSOLUTION OF CO2 IN GROUNDWATER. THE ENVIRONMENTAL IMPACTS
WILL BE FURTHER DESCRIBED IN PARAGRAPH 2.2
Decreased pH: The dissolution of CO2 in water involves chemical reactions between gaseous and
dissolved CO2, carbonic acid, bicarbonate ions and carbonate ions. When CO2 comes in contact with
water, it possibly will form carbonic acid as is indicated by the following chemical reaction:
CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3
-
Carbonic acid is not easily isolated, because it is an unstable compound. The more CO2 is dissolved,
the more carbonic acid will be present in the water, which leads to acidified environments.
The amount of acidification also really depends on the buffering capacity of the soils and
groundwater. In many aquifers minerals (for example calcite) are present which have the capacity to
buffer pH changes (Kharaka et al., 2006; IEAGHG, 2011).
Carbonic acid can trigger chemical degradation of both the cement as well as the casing, which can
lead to more carbonic acid ending up in the surrounding environment (IPCC, 2005; Kharaka et al.,
2006; AMESCO, 2007; IEAGHG, 2011).
23
Increase and mobilization of toxic metals: Research has been done by Kharaka et al. (2006) where
amounts of CO2 were injected in the subsurface. Changes were measured in situ and in the
laboratory. In situ measurements of the groundwater showed distinct decreases in pH (from 6.5 to
5.7) and increases in alkalinity (100 mg to 3000 mg/L as bicarbonate). Laboratory tests indicated
large increases in dissolved iron (from 30 mg to 1100 mg/L), manganese, and increases in the
concentration of calcium (Kharaka et al., 2006). The study of Kharaka et al. (2006) also showed a
profound shift in the isotopic composition of water and in the isotopic composition of dissolved
inorganic carbon, but only a subtle change in isotopic composition of methane. This indicates that
the injected CO2 (and not the residual methane) is the dominant carbon source. Changes in electrical
conductance were also measured but were only small (Kharaka et al., 2006).
More studies have identified the increases and possible mobilization of toxic trace metals as a
potential consequence of migration of CO2 from a storage site. Due to a decreased pH, carbonate,
sulfide and iron oxyhydroxide minerals could dissolve. As a result of this dissolution of minerals, toxic
trace metals could be mobilized, and migrate into the environment. Thereby toxic metals like iron,
lead, uranium, arsenic, or cadmium could end up in the groundwater (Pearce, 2004; Kharaka et al.,
2006; Kharaka et al., 2010; IEAGHG, 2011; IEAGHG, 2013/08). The toxic trace metals are most likely
to be mobilized by iron oxyhydroxides (Kharaka et al., 2006). If the potential storage reservoir would
contain residual oil or other organics the injected CO2 could mobilize toxic organic compounds as
well (CO2GeoNet Open Forum, 2009; Paulley et al., 2013).
The CO2 that migrates out of the storage reservoir may also act as a carrier gas transporting other
present gases, such as radon and hydrogen sulfide, towards the environment (Koornneef et al.,
2012).
Changes in biogeochemical cycles: Changes in seawater pH could impact the nutrient cycling in
coastal sediment ecosystems. Changes in the cycling of nitrogen, phosphorous and silicon have
potentially large ecosystem effects, but very little quantitative data exists to determine the precise
impact of the acidification of seawater on the transport of these nutrients (Widdicombe et al., 2009).
The water quality can become more complex, promoting the solubility of organic compounds,
bicarbonate complexes and chloride. Microbes could contribute to the biogeochemical processes
that depend on the physicochemical conditions (e.g. mineralogy, temperature, pH, Eh) (IEAGHG,
2011; Paulley et al., 2013). These processes depend very much on the site-specific geochemical
conditions.
2.2 Environmental impacts In this paragraph a distinction is made between the onshore and offshore environmental impacts,
since the associated ecosystems differ fundamentally. A living organism which is exposed to the
potentially adverse physical consequence is called an ‘impact receptor’, the adverse effect is named
‘environmental impact’. The severity of the impact depends on the quantity of the physical
consequence and the time of exposure to the physical consequence.
Onshore
When CO2 storage is implemented in an onshore location the possibility of leakage will potentially
cause changes in the groundwater quality, soil quality and/or atmosphere. Subsequently ecosystems
and even humans can be impacted by these changes induced by increased CO2 concentrations in the
environment.
24
The onshore environmental impact receptors will be divided into:
Plants: these can be plants within the agricultural system and plants within the natural system.
Animals: including invertebrates, vertebrates, and microbiota.
Humans: might be exposed to impacts as a result of CO2 migration into their environment.
Within human impact, the impact on potable water aquifers is classified.
Impacts will be described for each receptor below, and are summarized in the tree diagram of figure
2.3. Figure 2.3 starts with the impact receptor, the following column shows what physical
consequence is causing an impact. The next column describes what the impact is, and the last
column (Specification) specifies how the physical consequence impacted the receptor.
Plants
It should be kept in mind that the actual exact impact of increased CO2 concentrations on the plants
highly depend on site-specific characteristics, such as soil material composition, soil density,
vegetation density, vegetation types, density of animal population and weather conditions. Some
vegetation types will be more resistant and experience less stress than others, for example
dicotyledonous species appear more tolerant to high CO2 concentrations than monocotyledonous
plant species (IPCC, 2005; Ziogou et al., 2013).
The type of environmental impact on plants as a consequence of CO2 leakage also depends on
whether the impact is caused by a high concentration of CO2 in the soil or atmosphere, or by soil
degradation caused by dissolution of CO2 in the groundwater. The different sort of impacts are
described below.
Accumulation of gaseous CO2 in the atmosphere: Small increases in atmospheric CO2
concentrations resulting from the anthropogenic CO2 emissions promote plant growth (Saripalli,
2002; IEAGHG, 2007/3). Only when atmospheric CO2 concentrations build up to concentrations
above 5% plants can experience stress or death as a result of CO2 ponding and impacts on the
canopy (Saripalli et al., 2003). There are also plant species that have showed long-term adaption to
anoxic conditions in naturally CO2 enriched environments (Ziogou et al., 2013).
Accumulation of gaseous CO2 in the soil: Plants can be seriously affected by increased gaseous CO2
concentrations in the soil. Soil CO2 concentrations exceeding 5% can cause deleterious effects on
plant health. These deleterious effects are a consequence of root asphyxiation (Saripalli et al., 2003;
IPCC, 2005; Damen et al., 2006). Of plant species, trees are the most resilient, since the roots of
trees will be asphyxiated at concentrations exceeding 20% (Damen et al., 2006; Ziogou et al., 2013).
Some plant species are known to be able to adapt to the long-term anoxic conditions (Ziogou et al.,
2013).
Dissolution of CO2 in the groundwater: An indirect impact on plants will come from soil
degradation. A possible result of CO2 reacting with groundwater is a decreased pH. This decreased
pH can result in impacts on the chemistry of nutrients, redox sensitive elements and trace metals in
the soil. These can cause stress on plants growth and eventually possible death (Saripalli et al.,
2003).
25
FIGURE 2.3 ENVIRONMENTAL IMPACTS OF ONSHORE RECEPTORS.
* INDIRECT: IT IS NOT POSSIBLE TO SUBDIVIDE THIS IMPACT CAUSE UNDER ONE OF THE ‘CONSEQUENCES’ SINCE THE IMPACT CAUSE IS THE DEGRADATION OF THE ECOSYSTEM (FOR EXAMPLE
CAUSED BY PLANT DEATH)
26
Animals
Environmental impact on animals living in the atmosphere or soil can vary according to the following
causes: accumulation of gaseous CO2 in the atmosphere, accumulation of gaseous CO2 in the soil,
and by an indirect cause. The exact impact on an animal species is also very dependent on the type
of animal species. Where possible, quantitative information about the potential impact is provided.
Accumulation of gaseous CO2 in the atmosphere: If animals are exposed to high concentrations of
CO2 for a short period of time, effects can be as severe as mortality (Holloway et al., 2005). Impacts
on animals will vary between the different species and depends on the amount of CO2 which they
are exposed to. According to a study by Saripalli et al. (2002) on average animals will die by
asphyxiation at atmospheric CO2 concentrations above 10% (Saripalli et al., 2002).
Gradual low concentration release of CO2 into the atmosphere will result in similar asphyxiation
effects for animals if the CO2 is not diffused into higher atmospheric layers, but is able to build up to
hazardous concentrations. Animals that are incapable of quickly moving away from a surface
ponding event will experience asphyxiation sooner than, for example, birds (Paulley et al., 2013).
Accumulation of gaseous CO2 in the soil: Some species of burrowing animals can experience
asphyxiation by gaseous CO2 concentrations above 8% in the soil. Species of burrowing animals can
also be affected by a chronic disorder in their skeletal growth once they experience long-term
exposure to elevated soil CO2 concentrations. Also reduced sensitivity can be an effect of exposure
to CO2 (Paulley et al., 2013).
Indirect: Animals will be affected indirectly as a consequence of habitat damage caused by elevated
CO2 concentrations. This can lead to a reduction in the feed quality and availability, for example due
to impact on plants (Paulley et al., 2013). Thereby, animal populations can either experience stress
or will be able to adapt to the new ecosystem and food availability.
In the deeper subsurface, where different species of microbes can be found, acidification of their
habitat will cause stress on some communities. However, some other species of microbes may
benefit from more acidified surroundings (IPCC, 2005).
Humans
Impacts on humans are divided between impact as a consequence of accumulation of CO2 in the
atmosphere and dissolution of CO2 in the groundwater.
Accumulation of gaseous CO2 in the atmosphere: the impact on humans caused by accumulation of
gaseous CO2 in the atmosphere is divided between impact resulting from a sudden, large release of
CO2 and impact resulting from a gradual low concentration release of CO2.
Sudden, large release of CO2
Of all organisms, humans are the most sensitive to acute exposure of CO2. In figure 2.4 the
concentration and the time of exposure for humans is shown. Sudden exposure to concentrations
above 4% can cause health stress, for example small hearing loss, fast breathing, headaches and
dizziness. If the atmospheric concentration is above 6%, and humans will not get out of the area,
impacts can lead to unconsciousness or even death when there is longer exposure. Sudden
concentrations above 10% will lead to instant unconsciousness (see figure 2.4). Elevated CO2 can
27
also lead to frostbite because of the cooling effect of evaporating CO2 (IPCC, 2005; Benson et al.,
2005).
Gradual low concentration release of CO2
Figure 2.4 shows that if humans are exposed to concentrations exceeding 1.8% for a longer period of
time small health effects will be noticed. Concentration between 2% and 6% can lead to mental
depressions, headaches, dizziness and nausea (Flemming et al., 1997). If releases of CO2 do not
accumulate and flux into the air, there are no concerns for humans since the concentrations of CO2
will be diluted (AMESCO, 2007).
Dissolution of CO2 in the groundwater: CO2 dissolving in potable groundwater can impact humans in
various ways, positive and negative.
First, a positive impact of CO2 entering potable groundwater is that it could pressurize the aquifer
and thereby support groundwater abstraction rates in aquifers that have previously been over-
exploited or affected by drought (IEAGHG, 2013/08).
A negative impact of dissolution of CO2 in freshwater aquifers is that it can result in a decreased pH
and thereby can affect the chemistry of nutrients, redox sensitive elements and trace metals. These
changes can result in a serious hazard to human health. Freshwater aquifers that potentially occur
between a CO2 storage site and the surface can be used for drinking water or irrigation water.
Impacts on the water quality are important to know because, if unnoticed, they can pose a threat on
human health (IEAGHG, 2011; IEAGHG, 2013/08). Humans could also be impacted indirectly if their
agricultural fields are irrigated with CO2 dissolved groundwater.
FIGURE 2.4 EXPOSURE OF CO2 CONCENTRATIONS TO HUMANS
(FLEMMING ET AL., 1997; IPCC, 2005)
28
Offshore
When CO2 storage is implemented at an offshore location the possibility of leakage of CO2 will
potentially cause changes to the seabed or water quality. Subsequently ecosystems can be impacted
by these changes induced by increased CO2 concentrations in these environments.
The offshore environmental impact receptors are divided into:
Benthic biota: All organisms in and on the marine sediments are benthic organisms. 98% of all
marine species are benthic species (Widdicombe et al., 2009). These biota can be micro-biota or
multi-cellular flora and fauna.
Pelagic biota: All organisms living in the water column. These biota include larval forms of
benthic organisms, fish larvae, fish or phytoplankton.
The impact on populations depends on the spatial range of the community with respect to the
extent of the CO2 plume. This also depends on the habitat and sediment type. If a community of
sensitive organisms is bound to a specific habitat in a restricted area, they will off course be
impacted more than less specialized organisms living in a larger area (Paulley et al., 2013).
Impacts will be described per receptor and all impacts are summarized in the tree diagram in figure
2.5.
Benthic biota
Benthic biota can be impacted by CO2 leakage by accumulation of CO2 in the water column on the
seabed and by dissolution of CO2 in the seabed pore fluids.
The exact impact on benthic biota is very species-dependent. Where possible quantitative
information will be provided about the exact potential impact.
Accumulation of liquid, hydrated or dissolved CO2 in the water column: A very direct effect of
elevated CO2 concentrations in the water is that it can hypercapnia (elevated concentration of CO2 in
the blood) for some organisms (CO2GeoNet Open Forum, 2009). CO2 concentration ranging from 1%
to 6.3% in water will induce progressively stress to marine biota (IEAGHG, 2007/3).
Very susceptible benthic biota species are the sessile species that are incapable of moving away
from the ponding event (Paulley et al., 2013).
Dissolution of CO2 in the seabed pore fluids -> decreased pH: Increased CO2 concentrations can
influence benthic biota by changes in the pH, pCO2, bicarbonate and carbonate concentrations.
A pH decrease has two different impacts on benthic biota. Some benthic species can experience
extra stress seen in skeletal structure effects and some benthic species will benefit from decreased
pH and thereby dominate.
Stress/skeletal structure effects:
Exposure to acidified sea water disrupts growth and development in a number intertidal organisms
(Riebesell et al., 2000; Ishimatsu et al., 2004; Kikkawa et al., 2004; Pörtner et al., 2004; Bibby et al.,
2007). Examples of vulnerable intertidal organisms are corals, maerl beds, mussel beds, sea urchins
and scallops. They will be influenced by decreased pH since they are calcifying communities.
Decreased pH can eventually exhaust available carbonate. This will have implications for skeletal
29
strength, calcification, and growth (Widdicombe et al., 2008; Widdicombe et al., 2009). A study
measured 100% mortality for scallops at a pH of 7 or lower (CO2GeNet Open Forum, 2009).
It is likely that effects for skeletal organisms remain local to the leakage site, since most skeletal
organisms are not capable of spreading fast. The spreading of the organisms that are affected will
determine the domain over which leakage effects occur (Paulley et al., 2013).
Specific species will potentially be able to stabilize their community at a lowered pH after a period of
time. For example sea urchins manage to stabilize after a few months as long as the pH remains
above 6 (CO2GeoNet Open Forum, 2009).
Stress on skeletal species will also impact other sorts of organisms since they provide habitats for,
for example, fish (Bibby et al., 2008; Paulley et al., 2013).
Species domination
The most resistant animals to decreased seawater pH are the soft bodied animals (i.e. sea grasses,
nematodes) because they have a high capacity to regulate their chemical environment and do not
have calcified structures (Caldeira et al., 2003; Feely et al., 2004). In acidified oceans sea grasses and
invasive species are likely to dominate the seabed (Harrould-Kolieb et al., 2010).
Dissolution of CO2 in the seabed pore fluids -> changes in biogeochemical cycles: The impacts on
benthic biota caused by changes in the biogeochemical cycles are divided between three different
impacts: communities can get out of balance, changes can occur in micro-biota and some species
can experience stress.
The impact on the communities that will get out of balance is restricted to impacted bacteria. Since
the impact on bacteria is described in the same way for pelagic biota, the impact will be explained in
text box 2.
An indirect impact on some benthic species caused by some biogeochemical cycles is when CO2
changes micro-biota within the sediment. Micro-biota can impact cycling of other chemicals as well.
Some species of bioturbating organisms could be impacted by changes in the biogeochemical cycles
and thereby change the sediment habitat. If the sediment habitat is changed, this could cause stress
for benthic-pelagic coupling (Paulley et al., 2013).
Text box 2. Impacted bacteria
Bacteria decrease in cell number with higher CO2 concentrations. Archaea first are stimulated with a
small addition of CO2 but die with high CO2 concentrations (CO2GeoNet Open Forum, 2009).
Meiobenthos, nanobenthos and bacteria interact as a community. To better understand their
behavior to increased CO2 concentration, better understanding to their group interaction is required
(CO2GeoNet Open Forum, 2009). Various groups of bacteria are involved in the nitrogen cycle; these
will get out of balance and thereby affect the nitrogen cycle as well. The nitrogen cycle is sensitive to
high CO2 concentrations and especially the nitrification aspect will be affected.
30
FIGURE 2.5 OFFSHORE ENVIRONMENTAL IMPACTS
31
Pelagic biota
Pelagic biota can be impacted by CO2 leakage in three ways: impacts caused by CO2 accumulation in
the water column near the seabed, impacts caused by dissolution of CO2 in the water which causes
the pH to decrease, and by dissolution of CO2 which causes changes in the biogeochemical cycles.
Exact impact on pelagic biota by the physical consequences is species dependent. Where possible
quantitative information will be provided about the potential impact.
Accumulation of liquid, hydrated or dissolved CO2 in the water column: A very direct effect of
elevated CO2 concentrations in the water is that it can cause hypercapnia for some organisms
(CO2GeoNet Open Forum, 2009).
CO2 concentration ranging from 1% to 6.3% in water will induce gradual stress to marine biota.
Especially fish are vulnerable to high CO2 levels, which may damage respiration of fish. CO2
concentrations above the 2% can be lethal for fish (Saripalli 2003; IEAGHG, 2007/3).
Dissolution of CO2 in the water -> decreased pH: CO2 leakage can influence pelagic organisms by
changes in pH, pCO2, bicarbonate and carbonate concentrations, just like benthic organisms.
Possible impacts on pelagic biota can be stress or death for biota with exoskeletons. Since
calcification is inhibited under increased CO2 concentrations it is expected that organisms with
calcified skeletons will be most affected (Caldeira et al., 2003; Feely et al., 2004). The development
of the main pelagic calcifying organisms, foraminifera and coccolithophorids, will be repressed
(Riebesell, 2004).
Other than the impacts on benthic biota, impacts on pelagic biota will not remain local. The oceanic
current rates, coupled with the spreading potential of organisms that are affected, and their
recovery rates will determine the domain of the impacts (Paulley et al., 2013).
Species that will dominate with acidified oceans are algal species, jellies and some invasive species.
Since algal species rely on CO2 utilization, these species will be favored (Riebesell, 2004). Some
invasive species and jellies are likely to dominate, because they have a high capacity to regulate their
chemical environment and have no calcified structures (Harrould-Kolieb et al., 2010).
Dissolution of CO2 in the water -> changes in biogeochemical cycles: The impact on pelagic biota
that is caused by changes in the biogeochemical cycles can bring communities out of balance.
Impacts occurring to bacteria communities are described in text box 2.
An example of a pelagic community that is sensitive to changes in biogeochemical cycles is the
phytoplankton community. A slight increase of CO2 will favor some phytoplankton groups by
enabling photosynthetic carbon fixation. Some other phytoplankton communities are at current
oceanic CO2 levels already very close to CO2 saturation (Riebesell, 2004).
32
Chapter 3 Monitoring techniques To make sure worst-case scenarios will not take place, potential leakage has to be detected as soon
as possible. Therefore, (and because of permitting requirements, see page Appendix 1) monitoring
techniques have been developed that are able to detect possible migration of CO2.
Research Questions:
What monitoring techniques have been developed to detect CO2 migration and accumulation in the shallow subsurface and atmosphere?
Which monitoring techniques can be recommended for the monitoring of the consequences to the shallow subsurface and atmosphere?
A large number of monitoring techniques can be found in literature which are partly summarized in
the Monitoring Selection Tool (Oldenburg et al., 2003; Chadwick et al., 2006; Arts et al., 2008;
Haskoning Nederland B.V., 2008; Mathieson et al., 2010; Hagen, 2012; Hofstee et al., 2013; IEAGHG,
2013). In this chapter, monitoring techniques that are relevant for the consequences of CO2 leakage
in the shallow subsurface and atmosphere are selected from all monitoring techniques found in the
literature. These monitoring techniques are described in Appendices 3A to C. Subsequently, the
monitoring techniques that are used for the monitoring of the shallow subsurface and atmosphere
in the four selected CCS projects will be given. Based on whether monitoring techniques are
identified as applicable in literature and in real projects, some recommendations will be given in the
final paragraph on suitable monitoring techniques for the shallow subsurface and atmosphere.
3.1 Monitoring CO2 for the shallow subsurface and atmosphere
Natural background variability
Before monitoring of the shallow subsurface and atmosphere can take place, it is essential to
establish a representative set of baseline data in initial monitoring surveys. Data from repeat
monitoring surveys are compared with the baseline data (IPCC, 2005). For the monitoring of CO2
concentrations in the shallow subsurface and atmosphere, a baseline survey is essential. Natural
concentrations of CO2 in the soil are highly variable, both diurnally and seasonally (Oldenburg et al.,
2003; Smid et al., 2012). These natural concentrations of CO2 will be termed background CO2, which
is defined as CO2 derived primarily from the atmosphere and biologically mediated oxidation of
organic carbon, named respiration (Oldenburg et al., 2003). CO2 is produced in soils by root
respiration and decay of organic matter. CO2 may also enter soils from sub-soil sources; for example,
the CO2 which is dissolved in the groundwater (once derived by respiration or by atmospheric CO2)
and moved through the vadose zone, can enter the soil again by groundwater degassing. Where soil
parent material contains ancient organic carbon, oxidation of this carbon in the vadose zone can be
a source of CO2 (Oldenburg et al., 2003). Good baseline knowledge of the natural variations in geo-
and hydrochemistry prior to the injection of CO2 in storage sites is essential to understand possible
anomalies in repeat monitoring data. Preferably data on background CO2 concentrations will have to
be collected and measured for a few years prior to the use of the CO2 storage site in order to have a
complete dataset that captures all the natural variations over the seasons.
The monitoring techniques
A number of monitoring techniques relevant for the shallow subsurface and atmosphere is found in
literature and listed in the table 3.1; the techniques are divided according to their applicability
onshore, offshore or both. Each technique is briefly explained in Appendices 3A to C. If a monitoring
33
technique so far only has been used in onshore case studies, but could also be potentially applicable
in offshore monitoring projects it is still listed under the onshore techniques. Different literature
sources (IEAGHG, 2012; IEAGHG, 2013) provided information on the usage of monitoring techniques
in CCS projects. The monitoring techniques that are used and described in CCS projects monitoring
plans are marked green. The monitoring techniques that are not (yet) used in CCS projects are
marked red.
TABLE 3.1 SHALLOW SUBSURFACE AND ATMOSPHERE MONITORING TECHNIQUES; THE TECHNIQUES THAT ARE
DISPLAYED IN GREEN ARE MONITORING TECHNIQUES THAT ARE ALREADY USED OR DESCRIBED IN EXISTING CCS
PROJECT MONITORING PLANS. THE TECHNIQUES DISPLAYED IN RED ARE NOT (YET) APPLIED IN EXISTING CCS
PROJECTS
Except for three of the selected monitoring techniques (electric spontaneous potential, trained
animals and surface electro magnetics), all of the selected techniques in table 3.1 are well
established. This means that they are already used and tested on CCS projects or tested and used in
natural analogues of CO2 leakage.
3.2 Monitoring Techniques as described in CCS Projects Information from the monitoring plans from the four existing CCS projects (see paragraph 1.4
Current CO2 storage projects) is used to find out more about the experience with the techniques
and which techniques are considered essential. A monitoring plan has as main goal to detect any
problems affecting the storage integrity of the site and the potential impacts on the surrounding
environment (Henry et al., 2011). The monitoring techniques described in the monitoring plans of
the projects are listed below per project.
34
Barendrecht project monitoring techniques
Although the onshore storage project was abandoned, an extensive monitoring plan for the
Barendrecht was set out. In the Barendrecht project leakage along the well was identified as the
most likely leakage path. Therefore, the biggest part of the monitoring plan is scheduled around the
wells (Haskoning Nederland B.V., 2008). The monitoring techniques for the shallow subsurface and
atmosphere from the monitoring plan:
Atmospheric measurements (IR gas analyzer) Fluid geochemistry Downhole fluid chemistry Downhole pressure/temperature High resolution acoustic imaging Soil gas sampling Surface gravimetry
In Salah project monitoring techniques
The onshore In Salah project is almost 10 years in operation, and until now no leakage has been
detected by the monitoring techniques. Information on the applied monitoring techniques was
collected from: Mathieson et al., 2010; Hofstee et al., 2013.
Airborne spectral imaging Downhole fluid chemistry Downhole pressure/temperature Eddy Covariance Fluid geochemistry Soil gas sampling Time-lapse 3D/4D surface seismic
ROAD project monitoring techniques
The ‘ROAD-project’ with offshore CO2 storage is planned to start in 2015/2016. The monitoring
techniques for the shallow subsurface and atmosphere are collected from the report by Jonker, 2013
where they are described as part of the permitting process:
Boomer/sparkler profiling Downhole fluid chemistry Downhole pressure/temperature High resolution acoustic imaging Multibeam echo sounding Seabottom gas sampling Time-lapse 3D/4D surface seismic
Sleipner project monitoring techniques
The oldest of the four selected CCS projects is the offshore Sleipner project. So far, the storage of
CO2 at Sleipner has been very successful with no indication of migration of CO2 into the shallow
subsurface and atmosphere. Experience that was gained with the combination of seismic monitoring
and surface gravimetry has helped the understanding of the behavior of CO2 in the reservoir. Due to
the absence of leakage, no further understanding was gained in detecting environmental impacts
caused by leakage. The monitoring techniques were collected from: Hagen, 2012; Arts et al., 2008;
Hofstee et al., 2013; Chadwick et al., 2006.
Boomer/sparkler profiling
35
Downhole pressure/temperature Ecosystem monitoring Multibeam echo sounding Seabed EM Side scan sonar Surface gravimetry Time-lapse 3D/4D surface seismic
Overview of the monitoring techniques
All four projects perform pressure temperature measurements. The time-lapse 3D (or 4D) surface
seismic is also selected in three of the four monitoring programs, but the primary use of this
technique is on the monitoring of the deep subsurface. The monitoring plans for the onshore
projects both include the downhole fluid chemistry, fluid geochemistry measurements and soil gas
concentration measurements. For both offshore projects boomer/sparkler profiling and multibeam
echo sounding are selected.
3.3 Proposed monitoring requirements Some key requirements are developed based on knowledge gathered in the literature used in this
chapter. The requirements that should be acknowledged in a monitoring plan are listed below.
Early detection of CO2 leakage is the first priority. A lot of monitoring techniques have been developed are for the monitoring of the deep surface, especially for the detection of leakage and migration of CO2 before it will reach the shallow subsurface and atmosphere.
The greatest risk of CO2 leakage from any geological storage project into the shallow subsurface and atmosphere is identified to be along old abandoned wells (Benson et al., 2005; IPCC, 2005; Haskoning Nederland B.V., 2008; Mathieson et al., 2010). So therefore, it is proposed to perform intensive monitoring at locations around the wells, in particular for storage in depleted gas and oil fields. For storage in aquifers with little site-specific knowledge monitoring should also be directed to provide evidence for seal integrity.
Downhole pressure/temperature measurements can be a first indicator of CO2 leakage, and as shown in paragraph 3.2 pressure/temperature measurements are standard included in all monitoring plans. Time-lapse 3D (or 4D) monitoring could also provide a good basic knowledge of processes and changes around the risk areas. Furthermore, downhole fluid chemistry in observation wells is recommended as a monitoring technique that can early detect CO2 leakage.
For all the proposed shallow monitoring techniques the complementary use of other techniques is required so that the source of detected CO2/dissolved CO2 at the shallow subsurface and atmosphere can be verified.
It is also a proposed requirement to perform the monitoring in time-lapse mode so changes over time can be detected.
Proper knowledge of the natural background variability needs to be acquired as this is essential to determine whether the monitored changes are natural caused or not.
3.4 Proposed monitoring techniques For this project it is assumed that leaked CO2 does end up in the shallow subsurface and atmosphere
and there is a threat of physical consequences to occur which may lead to environmental impacts.
Proposed recommended monitoring techniques for the shallow subsurface and atmosphere are
selected from the monitoring techniques as described in Appendices 3A to C. In figure 3.1 the
recommended monitoring techniques are presented for each of the physical consequences as
identified and described in Chapter 2 (page 21).
36
For the recommendations only well-established techniques have been selected. Not all techniques
that have been selected for this study are already applied in existing CCS projects, but they are
considered relevant and established enough to be useful for the detection of the consequences.
FIGURE 3.1 PROPOSED MONITORING TECHNIQUES DIVIDED OVER THE FOUR DIFFERENT PHYSICAL
CONSEQUENCES
Monitoring of accumulations of gaseous CO2 in the atmosphere
To monitor whether high concentrations of CO2 are accumulating in the atmosphere three
monitoring techniques have been selected: Ecosystem monitoring, infrared gas analyzers, and
airborne multispectral techniques. Although airborne multispectral techniques are not yet used in
existing CO2 storage projects, it is a fast way of detecting vegetation stress.
Monitoring of accumulations of liquid, hydrated or dissolved CO2 in the water column
The detection of high CO2 accumulations in a water column can be done with the following
monitoring techniques: Fluid geochemistry, ecosystem monitoring, seabottom gas sampling, and
seawater geochemistry.
Seabottom gas sampling is not yet used in existing CCS projects, but would be recommended since it
is a straight forward method to verify if the gas at the seabottom is CO2.
Monitoring of accumulations of gaseous CO2 in the soil
To detect if CO2 has accumulated in the soil, three monitoring techniques are recommended: Soil gas
sampling, ecosystem monitoring, and infrared gas analyzers.
All the techniques are already applied in the monitoring of existing CO2 storage projects.
Monitoring of dissolution of CO2 in the groundwater or in seabed pore fluids
The monitoring of the dissolved CO2 in groundwater or in seabed pore fluids can be done using the
following four techniques: Ecosystem monitoring, downhole fluid chemistry, and fluid geochemistry.
37
Chapter 4 Mitigation measures Maintaining the long-term storage of CO2 is an important requirement for a large scale geological
CO2 storage project. Nevertheless, the possibility remains that the CO2 will leak out of the reservoir
and migrate into the overburden. This chapter focusses on mitigation measures for the shallow
subsurface and atmosphere after CO2 has escaped from the reservoir. A storage permit sets
requirements for the identification of mitigation measures as part of the ‘corrective measure plan'
(see Appendix 1).
Research Questions:
What mitigation measures are developed to stop the leakage of CO2? What mitigation measures are developed to reduce or remove the consequences of CO2
leakage? What mitigation measures are applicable to restore the impacted environment?
In this chapter we assume that CO2 leakage takes place and that there is a threat that consequences
and environmental impacts can occur.
4.1 Mitigation procedure The mitigation procedure is described in 3 steps:
Step 1. Preventing further leakage of CO2. Paragraph 4.2 will go into this process.
Step 2. Removing the consequences caused by CO2 leakage. This second step is the removal of the
unwanted CO2, the unwanted secondary minerals, metals, or other trace contaminants that are
present in the shallow subsurface and atmosphere as a consequence of the CO2 leakage. Paragraph
4.3 will elaborate on the mitigation measures for this process.
Step 3. Restoring the impacted environment. The final step is to restore the environment to its
original state. Paragraph 4.4 will describe the mitigation measures for this step.
For the removal of the CO2 and the restoration of the environment (step 2 and 3 of the mitigation
procedure) passive and active methods can be used. Passive methods are focused on the self-
restoration of the environment by, for example, biochemical processes or natural CO2 diffusion into
the atmosphere. This chapter will mostly focus on the active measures; the methods where humans
perform actions to mitigate the leakage of CO2.
It should also be noted that every storage site has different site-specific characteristics, which should
be recognized in the preparation of a mitigation plan.
4.2 Step 1. Preventing further leakage of CO2 The first step is to stop the leakage of CO2. In figure 4.1 a tree diagram for this stage is presented.
This paragraph will go through the tree diagram step by step.
To stop the leak, the starting point is to evaluate whether CO2 is leaking from the reservoir (so
through the seal or through fractures or faults) or from the well.
38
FIGURE 4.1 TREE DIAGRAM FOR THE MITIGATION PROCEDURE OF STEP 1
39
Leakage from the reservoir
In this research three options to stop or reduce leakage from the reservoir have been identified
(table 4.1):
1. Lowering the reservoir pressure
2. Stopping the injection
3. Intersecting the leak
1. Lowering the reservoir pressure: Lowering the reservoir pressure can be done by three different
mitigation measures. The first is reducing the reservoir pressure by lowering the injection rate,
which has shown to be an effective measure in a natural gas storage project in Illinois. In Illinois a
leak of natural gas from the reservoir was stopped by lowering the injection rate (Bell, 1961;
Buschbach et al., 1967).
Secondly, the pressure in the reservoir can be reduced. It could be a possibility that faults or
fractures become a leakage pathway for the CO2 because of high pressure in the storage reservoir
(Wo et al., 2005). By removing water or other fluids from the reservoir the pressure can be lowered
and the faults or fractures can stabilize (Benson et al., 2005).
Finally pressure can be decreased by creating a hydraulic barrier. This can be achieved by increasing
the pressure in the layer where the CO2 is leaking into (Benson et al., 2005).
2. Stopping the injection: Probably one of the most effective measures to stop or reduce leakage
from the reservoir is to stop injection and the use of the storage reservoir. If it is needed, the
injected CO2 can be extracted en reinjected into a more stable storage reservoir (Benson et al.,
2005).
3. Intersecting the leak: Another option to stop leakage from the reservoir is to extract CO2 with
wells that are nearby the actual leakage location. Thereby the leak will be intersected (Benson et al.,
2005).
TABLE 4.1 MITIGATION MEASURES FOR LEAKAGE FROM THE RESERVOIR
Leakage from the well
There are two things that can be done when CO2 is leaking from a well (table 4.2):
1. Repairing the well
2. Stopping the use of the well
1. Lowering the reservoir pressure
•Lowering injection rate
•Lower reservoir pressure
•Create a hydraulic barrier by increasing the reservoir pressure upstream of the leak
2. Stopping the injection
•Completely stop to stabilize the project
•Stop the injection and extract the CO2 from the reservoir to reinject it in a more stable geological structure
3. Intersecting the leak
•Intersect the leak with extraction wells near the leak
40
1. Repairing the well: When CO2 is leaking through the well it can be repaired by replacing the
injection tubings and packers.
When CO2 is leaking along the well, the leak can be plugged by squeezing cement behind the well
casing (Benson et al., 2005).
2. Stopping the use of the well: Before a well can be plugged and abandoned the flow of fluids into
the wellbore must be stopped by injecting heavy mud into the well. This process is also referred to
as ‘well kill’ (Benson et al., 2005).
If it is decided that the integrity of the well cannot be restored, it is best to stop using the well by
plugging the well and abandoning it using the standard abandoning techniques from the oil and gas
industry.
TABLE 4.2 MITIGATION MEASURES FOR LEAKAGE FROM A WELL
4.3 Step 2. Removal of the physical consequences The second step in the mitigation procedure is to remove the CO2 that has leaked and migrated into
the shallow subsurface and atmosphere. Figure 4.2 shows a tree diagram for this stage;
The selected mitigation measures are grouped for each type of physical consequence (see also
chapter 2), a summary of which is shown in table 4.3.
1. Removing accumulations of gaseous CO2 from the atmosphere
2. Removing accumulations of liquid, hydrated or dissolved CO2 from the water column
3. Removing accumulations of gaseous CO2 from the soil
4. Removing dissolved CO2 from the groundwater or seabed pore fluids
1. Repairing the well
•Replacing injection tubings and packers
•Squeeze cement behind the well casing to plug leaks
2. Stopping the use of
the well
•Kill the well by injecting heavy mud into the well casing
•Plug and abandon well that cannot be repaired
41
FIGURE 4.2 TREE DIAGRAM FOR THE MITIGATION PROCEDURE OF STEP 2
42
TABLE 4.3 MITIGATION MEASURES FOR PHYSICAL CONSEQUENCES OF THE SHALLOW SUBSURFACE AND
ATMOSPHERE
1. Remove accumulations of gaseous CO2 from the atmosphere: If a large amount of CO2 is released
into a confined space or inside a building, the immediate use of large fans would be sufficient to
dilute the CO2 to safe higher atmospheric levels (Benson et al., 2005).
Leakage in indoor environments and basements, chronic low concentration level
Extensive studies have been done on the mitigation of radon leaks from the subsurface into
basements. Techniques used for radon can be directly translated to mitigation measures of CO2
leakages in indoor environments. Two methods are described, both aim at dispersing contaminants
by inducing airflow through the soil gas (Benson et al., 2005). The first is subfloor or subslab
depressurization. The subslab is the area beneath the foundation plate of a building. Subslab
depressurization is commonly used in reducing pressure-driven radon entry into buildings with
concrete basement floors. Plastic pipes are installed through the concrete floor and small fans draws
the soil gas through the pipes to the outside, this would reduce the pressure beneath the basement
floor to a lower level than the pressure within the basement, thereby the chance of pressure-driven
soil gas entering the basements through the concrete floor will be eliminated (Fisk et al., 1995). The
other option is subslab pressurization. This method ventilates the region below the building with
outdoor air, thereby dispersing CO2 soil gas to surrounding areas. It also increases the pressure of
the region beneath the building which eliminates the possibility of CO2 from surrounding
environments to enter the area beneath buildings again (Fisk et al., 1995).
1. Removing accumulations of
gaseous CO2 from theatmosphere
•Immediate use of fans
•Subslab depressurization
•Subslab pressurization
2. Removing accumulations of
liquid, hydrated or dissolved CO2 from
the water column
•Lake degassing
3. Removing accumulations of
gaseous CO2 from the soil
•Extract CO2 accumulations with wells
•Enhance natural processes with 'BaroBalls
•Soil Vapor Extraction
•Dissolve CO2 accumulations in groundwater and extract
•Sprinkle or irrigate
•Create impermeable barrier with caps and place pumps below
4. Removing dissolved CO2 from the
groundwater or seabed pore fluids
•Pump and treat
•Treatment walls
•Pumping and aerating dissolved CO2
•Place hydraulic heads to prevent flow and spreading
43
2. Remove accumulations of liquid, hydrated or dissolved CO2 from the water column:
Accumulations of high concentration CO2 masses in deep stratified water layers can be removed by a
lake degassing methodology as described in Appendix 2.
3. Remove accumulations of gaseous CO2 from the soil: Large CO2 accumulations (gas phase) can be
extracted by the use of wells. The extracted CO2 can either be released in the atmosphere or
reinjected in suitable storage reservoirs.
If, after the extraction of CO2 accumulation, residual CO2 is still present in the subsurface, it can be
dissolved in the surrounding groundwater and subsequently be extracted with standard ground
water extraction wells. The dissolution process is rather slow and thus may not be very effective.
If unwanted CO2 accumulates in the soil, natural diffusive fluxes to the atmosphere through a
shallow installed well can be increased with the use of ‘BaroBalls’. A ‘BaroBall’ is a plug that is placed
on the shallow well, which may double the rate of contaminant removal by preventing the dilution
of contaminants with fresh air flowing into the well from the surface (DGSI, 2005).
To actively remove unwanted CO2 from the soil a commonly deployed mitigation measure is Soil
Vapor Extraction. This is a mechanism that flushes fresh air through the soil and subsequently collect
the soil gas with the use of vertical wells, horizontal wells, drainage systems, or trenches (Benson et
al., 2005; IEAGHG, 2007/11).
Another option is to sprinkle or irrigate the soil in order to dissolve CO2 and let it move down into
the groundwater. If the dissolution of CO2 leads to potentially harmful secondary reactions
groundwater mitigation measures like “pump and treat”, as will be described in the next paragraph,
can be used to remove the unwanted substances (Benson et al., 2005).
A last mitigation measure described in the article by Benson et al., 2005, is to place caps or another
impermeable layer above the CO2 accumulation. Pumping below this barrier could remove the CO2
and collect it to reinject in a suitable storage location (Benson et al., 2005).
4. Remove dissolved CO2 from the groundwater or seabed pore fluids: The measures that will be
described below are all applicable for onshore locations. To apply the measures at the seabed pore
fluids will probably be less easy, because of the unattainability of the seabed.
If the dissolved CO2 has contaminated the groundwater with dissolution of secondary minerals,
metals or other trace contaminants, the most common used method to purify it is to “pump and
treat” (Benson et al., 2005). A “pump and treat” system contains of a series of wells that pump the
contaminated groundwater to the surface. The groundwater is treated and reinjected in the
subsurface (Langwaldt et al., 2000).
It is also possible to place treatment walls in the subsurface. The contaminated groundwater will
then passively flow through the treatment wall where the impurities are removed by physical,
chemical and/or biological processes (figure 4.3) (Vidic et al., 1996).
Another option is to remove dissolved CO2 by aerating and then reinjecting it. Aeration is commonly
used as a first step in a water treatment procedure where the water is brought in close contact with
air to introduce oxygen and remove the CO2. For example by letting the water fall in several steps
over a cascade (Helm, 1998).
44
Finally, when the groundwater cannot be treated, it is possible to create a hydraulic barrier to
immobilize and contain the contaminated groundwater by placing extraction and injection wells on
strategically chosen locations (Benson et al., 2005).
4.4 Step 3. Restoring the impacted environments The last step in the mitigation procedure is to restore the impacted environment. Figure 4.4 shows a
tree diagram of this stage. This paragraph will go through the tree diagram step by step.
The categories of onshore impact receptors are plants, humans and animals. Since the mitigation
measures that are identified to protect humans and animals from CO2 are identical, the measures
will be combined under one paragraph. The mitigation measures for the offshore impact receptors
are combined under one paragraph as well. It should be noted that the mitigation of the
environmental impacts is very species dependent and therefore, a species specific or ecosystem
specific mitigation measure plan is desirable. Since it is beyond the scope of this research to specify
mitigation measures for every type of environmental impact some general examples will be given
and recommendations for further research will be provided.
The mitigation measures for the restoration of the impacted environments that will be described in
this paragraph are listed in table 4.4.
TABLE 4.4 MITIGATION MEASURES FOR THE ENVIRONMENTAL IMPACTS
Onshore:
1. Removal of stress for plants
• Mitigation measures step 1 and 2
• Mitigation measures from dune or agricultural management
Onshore:
2. Removal of stress for humans &
animals
• Mitigation measures step 1 and 2
• Move impact receptor away from the source point
Offshore:
3. Removal of stress for marine biota
• Mitigation measures step 1 and 2
• Reduce dominating species
• (Re-)introduce species
FIGURE 4.3. SCHEMATIC VIEW OF THE CONCEPT OF A TREATMENT WALL (VIDIC ET AL., 1996)
45
FIGURE 4.4 TREE DIAGRAM FOR THE MITIGATION PROCEDURE OF STEP 3
46
1. Removal of stress for plants: Plants can be impacted by leakage of CO2 caused by accumulation of
gaseous CO2 in the atmosphere and in the soil, and by dissolution of CO2 in the groundwater. The
impact caused by the accumulation of CO2 can be overcome if the steps described under paragraph
4.2 and 4.3 are followed. Usually, plants as part of an ecosystem will self-recover after a season.
If CO2 has dissolved in the groundwater and mitigation measures from step 2 have been applied
after plants already experienced impacts it can happen that the ecosystem is not able to self-
recover. A potential effect of acidified soils is the transformation from a species rich ecosystem to a
grass encroached area as is seen in for example Dutch coastal dune areas (Bobbink et al., 1992; Veer,
1997; Dorland et al., 2004). To restore this area to its original species-rich community various
intensive management programs can be used as are already applied in dune management or
agricultural management. In dune areas serious acidification caused grass-encroachment in the
ecosystem as a consequence of acid rain. Options to recover grass-encroached areas are: mowing,
grazing, sod cutting, burning, and additional liming (Dorland et al., 2004; Benson et al., 2005).
2. Removal of stress for humans and animals: Animals and humans can experience health stress
caused by high concentrations of CO2 in the atmosphere. These impacts can easily be mitigated by
two options. The first is to remove the accumulation with measures as described in step 2. If these
measures are not effective and the accumulation is not removed, the second option is to move the
impact receptor (humans and animals) away from the CO2 accumulation area.
Humans can also experience impact from migration of CO2 if it will end up in their potable
groundwater. CO2 reacting with water can reduce the water quality and purifying measures will need
to be expanded. Measures to purify groundwater are described under mitigation measures of step 2.
3. Removal of stress for marine biota: Impact caused by CO2 ending up in the offshore
environments can be seen in stress for the biota, in skeletal structure effects, in species domination,
and dis-balanced communities. Most of the impacts will self-recover when mitigation measures from
step 1 and step 2 are applied.
There is a lot of research done into management measures for impacted ecosystems as a
consequence of acidified oceans caused by anthropogenic increases in atmospheric CO2
concentrations (Harvey, 2007; Cullen et al., 2008; Jeffree, 2009). These measures can also be applied
for impact caused by acidification due to leakage and migration of CO2 from an offshore storage
reservoir into the water column.
An example of a mitigation measure to reduce dominating species are the measures that are
developed to reduce dominating algal blooms. By dispersing clay over the water the species algal
blooms can be reduced. The clay particles can aggregate with each other and with cells from the
algae and thereby removing those cells through sedimentation (Anderson, 2005).
Another way to restore the impacted marine environment from invasive species is to (re-)introduce
species that dominate the invasive species. The reintroduction of original species will also enhance
the possibility for the environment to restore to its original form (Anderson, 2005).
47
Chapter 5 Synthesis The previous chapters have aimed to identify potential effects of CO2 leakage from a storage
reservoir to the shallow subsurface and atmosphere and to describe the management of these
effects. All the different chapters are closely related to each other and these relations will be
described in this chapter. The information resulting from the previous chapters will be used in two-
fold. First, the bow-tie framework as introduced in the introduction of this thesis will be guiding in
representing the relations of the identified consequences, monitoring techniques and mitigation
measures, and will subsequently be tested with respect to its applicability. Second, the information
of the previous chapters will be used to critically analyze the TNO tool for risk evaluation and
monitoring of CO2 leakage with a focus on its completeness for the shallow subsurface and
atmosphere.
Research Questions:
How can all the information be compiled in a bow-tie framework? How can the bow-tie contribute to future work on risks of CO2 leakage? How can the TNO tool be improved with the results from this research?
5.1 The bow-tie framework The focus of this research has been on identifying the right part of the bow-tie framework which are
the consequences and the barriers. Figure 5.1 graphically represents the relations between the
different subjects of this research in a bow-tie framework. It is assumed that leakage of CO2 from a
storage reservoir takes place and CO2 migrates into the shallow subsurface or into the atmosphere.
The legal aspects shown in the overarching part are some permitting requirements. One of these
permitting requirements is the development of a monitoring plan that aims to detect CO2 leaks and
CO2 migration. The development of a monitoring plan is illustrated by the first proactive barrier of
this bow-tie: the shallow monitoring techniques. If the monitoring measures result in the detection
of the migration of CO2 into the shallow subsurface and atmosphere the next barrier of the bow-tie
aims to stop the leak and further migration of CO2. This second barrier is identified and described as
the first step in the mitigation procedure on page 37. The establishment of mitigation measures
results from the permitting procedure that require the development of a corrective measure plan.
If previous barriers have been unsuccessful in stopping the migration of CO2 before it ends up in the
shallow subsurface or in the atmosphere than some consequences can occur. Because of the
requirement of the development of an Environmental Impact Assessment it is required to identify
consequences of leakage of CO2 from a storage reservoir. The consequences are represented as
physical consequences and environmental impacts. Both the physical consequences and the
environmental impacts fall under the term consequences as used in the introduction where the
bow-tie concept is explained. The physical consequences are identified as accumulation of gaseous
CO2 in the atmosphere, accumulation of liquid, hydrated or dissolved CO2 in the water column,
accumulation of gaseous CO2 in the soil, and dissolution of CO2 in the groundwater or in seabed pore
fluids.
48
FIGURE 5.1 BOW-TIE FRAMEWORK FOR THE MIGRATION OF CO2 OUT OF CONTAINMENT INTO THE SHALLOW SUBSURFACE AND ATMOSPHERE
49
Since these physical consequences can lead to real tangible impacts (the Environmental impacts),
shallow monitoring should also be applied to detect if these physical consequences have occurred.
Once the physical consequences are detected the second step in the mitigation procedure aims at
removing the physical consequences from the shallow subsurface and atmosphere. If this barrier is
ineffective, environmental impacts can occur. Shallow monitoring measures are located at this stage
as well to detect if environmental impacts did occur. A last possibility to prevent the environmental
impacts to remain an impact is the application of mitigation measures from step 3 of the mitigation
procedure. Step 3 aims to restore the impacted environment to its original state.
Legal aspects have relations with every part of the scope of this research. Since it is impossible to
capture all legal aspects within the scope of this research in one figure, this overarching part just
shows some illustrative examples.
Applicability of the bow-tie framework
To evaluate the applicability of the bow-tie framework of figure 5.1 as an example one
environmental impact from the consequences is selected and tested in figure 5.2 to identify the
knowledge gaps of this research.
By assuming there is an exoskeleton structured species (impact receptor: benthic biota) that should
be protected in the area of the proposed CCS-project. By looking in the results from the
‘Consequences’ chapter it shows that benthic biota can experience impact by two different physical
consequences. The recommended monitoring approaches resulting from the ‘Monitoring’ chapter
give the recommended monitoring techniques for these physical consequences. The mitigation
measures that result from the second step of the mitigation procedure are also illustrated in figure
5.2
The applicability of the bow-tie framework was tested in figure 5.2. The links that were represented
resulted in an ineffective and inefficient management plan for the proposed problem. For example,
not all mitigation measures from step 2 are applicable for offshore use, definitely when the water
column is relatively deep.
50
FIGURE 5.2 BOW-TIE FOR THE IMPACT ON A BENTHIC BIOTA
5.2 Evaluation of the TNO tools for risk evaluation and monitoring of CO2 leakage The bow-tie framework from figure 5.1 could contribute to future research on risk assessments of
effects from CO2 storage in different ways. An example of how it could contribute will be sketched in
the following paragraphs.
First, it could be used to develop a tool where all possible consequences resulting from CO2 leakage,
monitoring techniques and mitigation measures are implemented with the help of a large database.
Input could then, for example, be a selected environmental impact. The output of the tool could
then result in specific recommendations for monitoring techniques and mitigation measures that are
linked to the physical consequence that causes the environmental impact.
The second purpose of the information that has been gained in this research is the contribution to
the TNO tools for risk evaluation and monitoring.
The tool for risk evaluation contains a database of features, events and processes (so called FEPs)
that may take place in the different release scenarios (CO2 leakage through the seal, along a fault, or
along a well).
51
The monitoring tool can be used when having a scenario in mind whereby leakage would take place.
For example a scenario could be “well failure”. Subsequently some FEPs have been selected with the
risk evaluation tool, which subsequently are evaluated in the monitoring tool. The FEPs are linked to
parameters, and the parameters are linked to monitoring techniques. The output of the tool is a set
of recommendations for the monitoring techniques that need to be used for the monitoring of the
selected FEPs.
FEPs related to the shallow subsurface and atmosphere
So far, this tool concentrates mostly on the possible causes of CO2 leakage around the reservoir and
does not take into account what happens to the shallow subsurface and atmosphere when a CO2
release scenario takes place. The FEPs that are currently in the tool that focus on the shallow
subsurface and atmosphere are:
CO2 release into the atmosphere
Ground water contamination
Mineral precipitation and dissolution
Surface soil contamination
The tool shows when selecting these FEPs that they are currently not linked to parameters and
therefore, no recommended monitoring techniques are presented in the output. The FEP ‘Mineral
precipitation and dissolution’ is the only FEP of these four that is related to some parameters (water
chemistry, permeability change, displacement of pore gas) but these parameters are not matched to
a recommended monitoring technique.
It is suggested that the following potential FEPs that have been identified in this study are added to
the tool:
Accumulation of liquid, hydrated or dissolved CO2 in the water column Accumulation of gaseous CO2 in the soil Dissolution of CO2 in the groundwater Dissolution of CO2 in the seabed pore fluids
Monitoring techniques related to the shallow subsurface and atmosphere
Monitoring techniques that are in the tool that are similar to the techniques that are identified in
the monitoring chapter on page 32 are:
Bubble stream chemistry
Bubble stream detection: High resolution acoustic imaging,
IR gas analyzers
lab testing of samples
Long -term downhole pH
Natural tracers
pH monitoring
Temperature sensors
Water/groundwater chemistry
There are some monitoring techniques available in the tool that could be matched to the FEPs that
are related to the shallow subsurface and atmosphere. Nevertheless, it is suggested that the
following monitoring measures are added to the tool and linked to the suggested FEPs as well:
52
Ecosystem monitoring Airborne multispectral Seabottom gas sampling Soil gas sampling
Overall comments that are made on the Monitoring Tool:
The tool could be further expanded with more shallow FEPs as could result from the
identified physical consequences in this thesis: accumulation of gaseous CO2 in the
atmosphere, accumulation of liquid, hydrated or dissolved CO2 in the water column,
accumulation of gaseous CO2 in the soil, dissolution of CO2 in the groundwater, or
dissolution of CO2 in the seabed pore fluids. If the FEPs are expanded some new monitoring
techniques will have to be added to the tool as well. For all the physical consequences
monitoring techniques are proposed in this thesis. At least ecosystem monitoring, airborne
multispectral, seabottom gas sampling, and soil gas sampling should be added to the
monitoring tool.
CO2 leaking from the storage reservoir and ending up in the shallow subsurface and
atmosphere would be a low-probability consequence if the storage site is properly
characterized, selected and managed. The main goal of monitoring CO2 storage reservoirs is
to detect irregularities long before the CO2 will enter the shallow subsurface and
atmosphere. The monitoring techniques that would result from the physical consequences
in the shallow subsurface and atmosphere are contingency measures that will only be
implemented if there is an indication of leakage.
To complete the tool, some extra FEPs will have to be incorporated that are related to the
shallow subsurface and atmosphere. FEPs that could be used as input are FEPs like the
physical consequences and the environmental impacts that are identified in this report.
These FEPs can then be linked to the monitoring techniques as are proposed.
Appendix 5 shows a complete list with current FEPs that are linked to a parameter, but not linked to
a monitoring technique. The list also shows the FEPs that are not linked to a parameter. It is
recommended that these FEPS will eventually be linked to monitoring techniques as well.
53
Chapter 6 Discussion This chapter will start with overall discussing the results from this study. Then it will discuss the bow-
tie framework that resulted from this study and will subsequently go into the separate aspects of
this bow-tie framework. The aim is to identify where the knowledge gaps are located.
6.1 Overall If migration of CO2 from a storage reservoir takes place this can potentially lead to some physical
consequences to the shallow subsurface or atmosphere. In this study the physical consequences are
identified as: accumulation of gaseous CO2 in the atmosphere at the surface, accumulations of liquid,
hydrated or dissolved CO2 in the water column, accumulations of gaseous CO2 in the soil, or
dissolution of CO2 in the groundwater or in seabed pore fluids. If these physical consequences are
significant it is considered certain that they will lead to environmental impacts. Therefore, it is
essential that the shallow subsurface and atmosphere are monitored and an extensive mitigation
measure plan is developed and ready to be used when leakage and migration of CO2 takes place.
It is seen in the results of this research that some aspects of this report are more detailed and others
are very general. That is partly because there was just not that much literature available on specific
details, and thereby the literature that was found on more detailed impacts or mitigation measures,
has been used to write the results. For another part, some chapters did not provide detail because it
is not possible to give details when the choice is made to do the research not on a specific location,
but in general.
Also because the scope of this study is very large, it is impossible to involve all possible
consequences, and resulting mitigation measures.
6.2 Synthesis Ideally the bow-tie framework from figure 5.1 would result in a tool that helps with identifying and
establishing site-specific environmental monitoring and related corrective measurement plans. But
before this is a realistic goal, a lot more work on more specific environmental characteristics will be
needed to be able to give detailed answers to questions about tangible environmental risks for a
specific location.
The applicability of the bow-tie framework was tested in figure 5.2. The links that were represented
resulted in an ineffective and inefficient management plan for the proposed problem. For example,
not all mitigation measures from step 2 of the mitigation procedure are applicable for offshore use,
definitely not in a deep marine environment.
The presented bow-tie framework can give conclusive results if it is applied to real site-specific case.
In research at a specific site, for example in the North Sea, should start with an extensive survey to
protected and/or vulnerable flora and fauna. The survey can result in experiments that test the
vulnerability of the species to for example increased CO2 concentrations and pH changes. Based on
the results a custom made mitigation plan can be produced. The results from the experiments will
also help in developing the details of the monitoring plan. If the critical CO2 concentrations resulting
from the experiments are known, it is also known what concentrations should be measured.
If surveys from all proposed CCS projects would save their results a general public accessible
database a complete set with information on vulnerable habitats, flora and fauna can be the
outcome. Subsequently a tool that is based on the bow-tie framework can be developed and be
54
linked to this database. This would result in saving a lot of work on developing Environmental Impact
Assessments, Monitoring plan and corrective measure plans for new proposed CCS projects.
6.3 Consequences As a part of the identification of the consequences for the bow-tie framework, this study resulted in
a deviation between physical consequences and environmental impacts. The difficulty with
identifying these consequences came from the scarce amount of literature available that focusses on
the environmental effects from CO2 storage. Most literature focusses on deep processes and leakage
mechanisms. As a consequence of the scarce availability of literature a large part of the identified
physical consequences and environmental impacts is based on a research done by Paulley et al.
(2013).
Another difficulty in identifying the consequences of CO2 is that this study did not focus on a specific
proposed storage location. Potential consequences highly depend on site specific characteristics like
for example soil composition, natural background CO2 variability, and the existing flora and fauna.
Since this study is performed in a generic way, including both onshore and offshore possible
consequences, there was a struggle in balancing information on site-specific impacts to more generic
impacts.
It is suggested that for further identification of the consequences future research will focus on a site-
specific case study. Once a potential storage site is selected rigorous baseline surveys should be
carried out to ascertain changes are noticed after the implementation of the CCS project.
Based on this research, some recommendations to minimize environmental impacts can be made.
CO2 storage should preferably not take place in a reservoir that is overlain by an ecosystem with
vulnerable species and habitats. For offshore locations CO2 storage should not take place in regions
that are in the presence of ecosystems that have a high reliance on calcification (such as corals and
maerl beds). Site selection should be based on the absence of unique and sensitive ecosystems.
6.4 Reactive barriers
Monitoring techniques
With the identification of the first reactive barrier from the bow-tie framework it became clear that
the amount of monitoring techniques that are identified in literature on CO2 storage is enormous.
Thereby it has been a challenge to select a complete list of monitoring techniques that are applicable
for the monitoring of the shallow subsurface and atmosphere. A lot of monitoring techniques are
not termed in the same words consequently throughout the literature. Another difficulty is that the
monitoring of the shallow subsurface and atmosphere is not a priority in the monitoring of CO2
storage sites. Emphasis in literature on monitoring is mostly put on the behavior of the injected CO2
in the reservoir.
In case there are indications of leakage in the deeper subsurface, gas sampling and fluid chemistry,
monitoring techniques should be installed, since these techniques are able to detect the identified
physical consequences.
Mitigation measures
By identifying the subsequent barriers it showed that currently there is not much literature present
on mitigation measures for leakage of CO2 from storage sites. The mitigation measures identified in
55
this study are largely based on a study performed by Benson and Hepple (2005), which is also not a
very in-depth research. It is expected that the MiReCOL project will contribute to the development
of more mitigation measures for the consequences to the shallow subsurface and atmosphere.
Based on the research done in this project it is suggested that a three step mitigation will be
performed when CO2 migration from the containment is detected. By following the three-step
procedure the potential leak will be stopped, the migrated CO2 removed and the environment
restored to its original state it will basically look like the situation before leakage started.
6.5 Legal Aspects The identification of the overarching part of the bow-tie framework resulted in the description of
some legal aspects. The legal situation of CO2 storage is a very complex subject to study. Not in the
least, because it is under constant changes. For example the CCS Directive is currently under review
and will probably be changed in the near future as well.
Another complexity is that applicable legal aspects also rely on site specific characteristics and can
be more or less complex depending on if storage of CO2 is for example planned on an onshore or
offshore location. Appendix A has given a sneak peek into some aspects of the legal requirements,
especially on how to manage the threat of environmental damage caused by CO2 leakage from a
storage reservoir.
What the appendix did show is that there is a high connectivity between two completely different
disciplines. Therefore, it is of added value to every researcher to look into other disciplines (for
example jurisdictional aspects) to see that there is so much more to Earth Science related topics
than just natural and physical aspects. Interdisciplinary research can potentially result in new
insights, because it forces a researcher to look into aspects from another point of view.
Because there is a great difference in earth scientific writing and legal writing it is suggested that
future work on a Legal Framework for CO2 storage projects is carried out by people with experience
on legal issues when the aim is to produce in-depth legal analysis. It still is very highly recommended
that research into the legal issues is carried out in extensive collaboration with people who have
expert knowledge on the techniques and theories behind CO2 storage and thereby making it a
multidisciplinary research. Mixing different ways of thinking is a great way to stimulate the
development of new approaches to a problem.
56
Chapter 7 Conclusions and recommendations for further research Based on this research and the discussion some main conclusions can be drawn. These will result in
recommendation for further research.
7.1 Conclusions In this research the bow-tie framework has successfully been applied. The resulting bow-tie
framework can be used in further research into identifying effects of CO2 storage on the
shallow subsurface and atmosphere.
Based on the bow-tie framework a statement on the possibility to perform CO2 storage
safely is only possible in relation to specific sites since the amount of threat for
environmental damage highly depend on site-specific characteristics.
A general overview of consequences of CO2 leakage is identified and subdivided between
four physical consequences and resulting environmental impacts. The physical consequences are accumulation of gaseous CO2 in the atmosphere, accumulation of liquid, hydrated or dissolved CO2 in the water column, accumulation of gaseous CO2 in the soil, and dissolution of CO2 in the groundwater or in seabed pore fluids. These four physical consequences can lead to numerous environmental impacts.
A list of key monitoring recommendations for the monitoring of the shallow subsurface and atmosphere is described and some monitoring techniques are recommended. Monitoring techniques should be applied at every stage of the bow-tie framework.
A mitigation procedure has been developed consisting of the following three steps: The first step describes measures to stop or reduce further leakage of CO2. The second step describes measures and techniques to remove the four physical consequences from the shallow subsurface and atmosphere. The last mitigation procedure step describes an approach to restore the potentially affected environment to its original state.
The legal aspects appendix has made it clear that legal aspects are a very complex subject, because there is a high connectivity between various laws and regulations. More research will have to be performed before a conclusive legal framework can be developed.
By the choice of not performing this research for a specific location the scope of the research became very large and identifying detailed consequences and management options became a challenge. Based on the discussion it can be concluded that more research is needed into the possible effects and management options of CO2 storage to the shallow subsurface and atmosphere.
7.2 Recommendations for further research In order to produce a complete bow-tie framework for all the consequences and reactive
barriers it is recommended that future research needs to either focus on a specific location of a proposed project, or it needs to start working on creating a very large public accessible database that can be used and complemented by all CCS-project developers. This will be a time consuming long-term project, but if done successfully can result in a tool that will provide a custom made monitoring and corrective measure plan for every potential environmental impact or physical consequence.
57
The timing of the exposure of impact receptors to physical consequences has a big influence
on the severity of the environmental impacts. For example, a very short-term exposure to
slightly increased CO2 concentrations will probably not result in an impact on an ecosystem.
But if this slightly increased CO2 concentrations will be exposed to an ecosystem for a long-
term it is expected that there might be a serious effect. It might be interesting to
incorporate this aspect in further research to consequences on the shallow subsurface and
atmosphere.
For the development of a mitigation procedure more research is needed into measures
identified in the second step: Removal of the physical consequences. Not all techniques
described in this step are feasible to be applied at offshore locations.
The third step of the mitigation procedure (‘Restoring the impacted environment’) should
also be further developed. There was little available scientific literature that described
research on mitigation measures for restoring the impacted environment. Potentially
mitigation measures for restoring the environment can be found by doing research into
other disciplines. Probably extensive research is done within the biological, agricultural and
marine disciplines to management options for eutrophication and acidification. So it is
suggested that further research will be done in the mentioned disciplines to develop
applicable mitigation measures for restoring the environment.
It is needless to say that overall more research needs to be done into identifying effects of
CO2 storage on the environment, since it can be stated that very few literature is available on the shallow subsurface and atmosphere in relation to CO2 storage. A nice suggestion for future research is to start the study by selecting a specific location and perform a site-specific research.
58
References AMESCO (2007) AMESCO Generic Environmental Impact Study on CO2 Storage. [Croezen, H., Van Eijs,
R., Vosbeek, M., Hagedoorn, S., Wildenborg, T., Goldsworthy M., Holleman, E. Th.] Final Report
Commissioned by AMESCO Steering committee
Anderson, D.M. (2005) The ecology and oceanography of harmful algal blooms: Multidisciplinary
approaches to research and management by Donald M. Anderson. IOC Technical Series 74, UNESCO
2007. IOC/2007/TS/74
Arts, R., Chadwick, A., Eiken, O., Thibeau, S., Nooner, S. (2008) Ten years’ experience of monitoring
CO2 injection in the Utsira Sand at Sleipner, offshore Norway. First break 26, January 2008
Bateson, L., Vellico, M., Beaubien, S.E., Pearce, J.M., Annunziatellis, A., Ciotoli, G., Coren, F.,
Lombardi, S., Marsh, S. (2008) The application of remote-sensing techniques to monitor CO2-storage
sites for surface leakage: Method development and testing at Latera (Italy) where naturally produced
CO2 is leaking to the atmosphere. International Journal of Greenhouse Gas Control 2 (3), p. 388–400
Bell, A. (1961) Underground storage of natural gas in Illinois. Division of the Illinois State Geological
Survey Circular 318, p. 27
Belotti, C., Cuccoli, F., Facheris, L., Vaselli, O. (2003) An application of tomographic reconstruction of
atmospheric CO2 over a volcanic site based on open-path IR laser measurements. IEEE Transactions
on Geoscience and Remote Sensing 41, p. 2629 – 2637 Part 1
Benson, S., Hepple, R. (2005) Prospects for early detection and options for remediation of leakage
from CO2 storage projects. Carbon Dioxide Capture for Storage in Deep Geologic Formations 2, p.
1189-1204
Bibby, R., Cleall-Harding, P., Rundle, S., Widdicombe, S., Spicer, J. (2007) Ocean acidification disrupts
induced defences in the intertidal gastropod Littorina littorea. Biology Letters 3, p. 699–701
Bibby, R., Widdicombe, S., Parry, H., Spicer, J., Pipe, R. (2008) Effects of ocean acidification on the
immune response of the blue mussel Mytilus edulis. Aquatic Biology 2, p. 67-74
Bobbink, R., Heil, G.W., Raessen, M.B.A.G. (1992) Atmospheric deposition and canopy exchange
processes in heathland ecosystems. Environmental Pollution 75(1), p. 29-37
BowTiePro.com (2014) BowTie Pro™ The modern, fast and easy to use risk analysis tool. Enterprise
Business Centre, Admiral Court, UK. www.bowtiepro.com
Bradshaw, J., Boreham, C., Pedalina, F. la (2005) Storage retention time of CO2 in sedimentary basins:
Examples from petroleum systems. Proceedings of the 7th International Conference on Greenhouse
Gas Control Technologies (GHGT-7), September 5-9, 2004, Vancouver, Canada, v.I, 541-550
Bresser, A.H.M., Berk, M.M., Van den Bron, G.J., Van Bree, L., Van Gaalen, F.W., Ligtvoet, W., Van
Minnen, J.G., Witmer, M.C.H. (2005) Effecten van klimaatverandering in Nederland. Milieu- en
Natuurplanbureau op verzoek van de Staatssecretaris voor Milieubeheer
Buschbach, T.C., Bond, D.C. (1967) Underground storage of natural gas in Illionois – 1967. Illinois
State Geological Survey. Illinois Petroleum 86, p. 54
59
Caldeira, K. and Wickett, M.E. (2003) Oceanography: Anthropogenic carbon and ocean pH. Nature
425, p. 365
Carlsen, I.M., Mjaaland, S., Nyhavn, F. (2001) SACS2 – Work Package 4. Monitoring well scenarios.
SINTEF Report 32.1021.00/01/01. p. 43
Chadwick, A., Arts, R., Bernstone, C., May, F., Thibeau, S., Zeigel, P. (2006) Best practice for the
storage of CO2 in saline aquifers. Observations and guidelines from the SACS and CO2STORE projects.
CO2CRC.com.au (2011) Leaders in research into Carbon Capture and Storage. Website
http://www.co2crc.com.au/
CO2GeoNet Open Forum (2009) What if CO2 reaches the surface? – Aquatic ecosystem responses to
CO2. Presentation on March 18-20 2009. At Venice, San Servolo Island
Comas, X., Slater, L., Reeve, A.S. (2005) Spatial variability in biogenic gas accumulations in peat soils
is revealed by ground penetrating radar (GPR). Geophysical Research Letters 32, L08401
Cuccoli, F., Facheris, L., Tanelli, S., Giuli, D. (2000) Infrared tomographic system for monitoring the
two-dimensional distribution of atmospheric pollution over limited areas. IEEE Transactions on
Geoscience and Remote Sensing 38, p. 155-168
Cullen, J.J., Boyd, P.W. (2008) Predicting and verifying the intended and unintended consequences of
large-scale ocean iron fertilization. Marine Ecology Progress Series 364, p. 295-301
Damen, K., Faaij, A., Turkenburg, W. (2006) Health, safety and environmental risks of underground
CO2 storage - overview of mechanisms and current knowledge. Climate Change 74, p. 289-318
Denman, K.L., Brasseur, G., Chidthaisong, A., Ciais, P., Cox, P.M., Dickinson, R.E., Hauglustaine, D.,
Heinze, C., Holland, E., Jacob, D., Lohmann, U., Ramachandran, S., da Silva Dias, P.L., Wofsy, S.C.,
Zhang, X. (2007) Couplings Between Changes in the Climate System and Biogeochemistry. In: Climate
Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment
Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z.
Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press,
Cambridge, United Kingdom and New York, NY, USA
DGSI (2005) BaroBallTM. Environmental and Geotechnical Products. Durham Geo Slope Indicator
DOE (1994) Handbook of methods for the analysis of the various parameters of the carbon dioxide
system in sea water; version 2, A. G. Dickson & C. Goyet, eds., ORNL/CDIAC-74.
Dorland, E., Berg, L.J.L. van den, Berg, A.J. van de, Vermeer, M.L., Roelofs, J.G.M., Bobbink, R. (2004)
The effects of sod cutting and additional liming on potential net nitrification in heathland soils. Plant
and Soil 265, p. 267-277.
EC (2009) Directive 2009/31/EC of the European Parliament and of the Council of 23 April 2009 on the geological storage of carbon dioxide and amending Council Directive 85/337/EEC, European Parliament and Council Directives 2000/60/EC, 2001/80/EC, 2004/35/EC, 2006/12/EC, 2008/1/EC and Regulation (EC) No 1013/2006. Official Journal of the European Union, 5 June 2009
60
EC (2013) Environmental Liability Directive – Protecting Europe’s Natural Resources. Luxembourg:
Publications Office of the European Union, 2013, ISBN 978-92-79-29753-3
Ec.europa.eu (2014) The 2020 climate and energy package. Last update: 04/04/2014
http://ec.europa.eu/clima/policies/package/index_en.htm
Ecofys (2007) Making large-scale Carbon Capture and Storage CCS in the Netherlands work - An
agenda for 2007-2020, policy, technology and organization. At the request of EnergieNed and the
Dutch Ministries of the Environment and Economic Affairs. By Mariëlle Vosbeek (Ecofys) and Hans
Warmenhoven (Spinconsult). May 2007
Feely, R.A., Sabine, C.L., Lee, K., Berelson, W., Kleypas, J., Fabry, V.J., Millero, F.J. (2004) Impact of
Anthropogenic CO2 on the CaCO3 System in the Oceans. Science 305, no. 5682, pp. 362-366
Fisk, W.J., Prill, R.J., Wooley, J., Bonnefous, Y.C., Gadgil, A.J., Riley, W.J. (1995) New methods of
Energy Efficient Radon Mitigation. Health Physics 68(5), p. 689-698
Fleming, E.A., Brown, L.M., Cook, R.I. (1992) Overview of Production Engineering Aspects of
Operating the Denver Unit CO2 Flood. Paper SPE/DOE 24157 presented at the 1992 SPE/DOE
Enhanced Oil Recovery Symposium, Tulsa, 22−24 April. Society of Petroleum Engineers Inc.,
Richardson, TX, USA.
Freifeld, B.M., Daley, T.M., Hovorka, S.D., Henninges, J., Underschultz, J., Sharma, S. (2008) Recent
advances in well-based monitoring of CO2 sequestration: presented at the 9th International
Conference on Greenhouse Gas Control Technologies (GHGT-9), Washington, D.C., November 16-20,
2008. GCCC Digital Publication Series #08-03f
Gambardella, B., Cardellini, C., Chiodini, G., Frondini, F., Marini, L., Ottonello, G., Zuccolini, M.V.
(2004) Fluxes of deep CO2 in volcanic areas of central-southern Italy. Journal of Volcanology and
Geothermal Research 136, p. 31-52
Global CCS Institute (2014) EU Directive 2009/31/EC on the geological storage of carbon dioxide.
http://www.globalccsinstitute.com/networks/cclp/legal-resources/dedicated-ccs-legislation/europe
Government.nl (2014) Environment - EU Legislation. Ministry of Infrastructure and the Environment.
http://www.government.nl/issues/environment/roles-and-responsibilities-of-central-
government/eu-legislation
Habib, M.K. (2007) Controlled biological and biomimetic systems for landmine detection. Biosensors
and Bioelectronics Volume 23, Issue 1, p. 1-18
Hagen, S. (2012) Sleipner Knowledge sharing in CCS projects - Workshop Mobile, Alabama. Sveinung
Hagen and colleagues - Statoil May 16 and 17 – 2012
Hall-Spencer, J.M., Rodolfo-Metalpa, R., Martin, S., Ransome, E., Fine, M., Turner, S.M., Rowley, S.J.,
Tedesco, D., Buia, M.C. (2008) Volcanic carbon dioxide vents show ecosystem effects of ocean
acidification. Nature 454, p. 96-99
Hans, I., Holleman, E. (2011) Milieueffectenrapportage CCS Maasvlakte (ROAD-project) Deelrapport
Opslag. Royal Haskoning in opdracht van ROAD, 17 juni 2011
61
Harmelink, M. (2013) 40 years of energy and climate policies. Presentation at the Utrecht University
by Harmelink Consulting on September 18, 2013
Harper, R.J., Furton, K.G. (2007) Biological Detection of Explosives. Chapter 13 in Counterterrorist
detection techniques of explosives by Jehuda Yinon. Elsevier p.395-432
Harrould-Kolieb, E., Huelsenbeck, M., Selz, V. (2010) Ocean acidification – the untold stories.
OCEANA, Protecting the World’s Oceans. November 2010
Haskoning Nederland B.V. (2008) MER Ondergrondse opslag van CO2 in Barendrecht. Deelrapport 3:
Ondergrondse opslag. Opgesteld in opdracht van Shell CO2 Storage B.V. December 2008
Harvey, L.D.D. (2007) Mitigating the atmospheric CO2 increase and ocean acidification by adding
limestone powder to upwelling regions. Journal of Geophysical Research 113, C04028
Helm, A.W.C van der (1998) Modellering van intensieve gasuitwisselingssystemen. Afstudeerverslag
TU Delft Faculteit Civiele Techniek en Geowetenschappen
Henry, X., Jonker, T., Schoonwater, A., Wattenberg, V. (2011) The permitting process. Special report
to the Global Carbon Capture and Storage Institute. ROAD | Maasvlakte CCS Project C.V., December
2011
Hofstee, C., Neele, F. (2013) Monitoring. Presentation on September 24, 2013 by TNO
Holloway, M. (2000) The Killing Lakes. Scientific American. July 2000
Holloway, S., Pearce, J.M., Ohsumi, T., Hards, V.L. (2005) A Review of Natural CO2 Occurrences and
their Relevance to CO2 Storage. British Geological Survey External Report, CR/05/104, 117pp.
Hoversten, G.M., Gasperikova, E. (2005) Non-seismic geophysical approaches to monitoring. In:
Thomas, D.C. & Benson, S.M. (ed.) Carbon dioxide Capture for Storage in Deep Geologic Formations
– Results from the CO2 Capture Project. Volume 2: Geological Storage of Carbon Dioxide with
Monitoring and Verification. Elsevier, Oxford, p. 1071 – 1112
IEA (2008) IEA Energy Policies Review. The European Union. The International Energy Agency.
OECD/IEA
IEAGHG (2007/3) Study of potential impacts of leaks from onshore CO2 storage projects on terrestrial
ecosystems. 2007/3, July 2007.
IEAGHG (2007/11) Remediation of leakage from CO2 storage reservoirs. IEA Greenhouse Gas R&D
Programme. 2007/11, September 2007
IEAGHG (2011) Potential Impacts on Groundwater Resources of CO2 Storage. 2011/11 October 2011
IEAGHG (2012) Quantification Techniques For CO2 Leakage. 2012/02, January, 2012
IEAGHG (2013/08) Interaction of CO2 Storage with Subsurface Resources. 2013/08 April 2013
IEAGHG (2013) Monitoring Selection Tool. http://www.ieaghg.org/ccs-resources/monitoring-
selection-tool1
62
IPCC (1990) Climate Change: The IPCC Scientific Assessment (1990). Report prepared for
Intergovernmental Panel on Climate Change by Working Group I [J.T. Houghton, G.J. Jenkins and J.J.
Ephraums (eds.)] Cambridge University Press, Cambridge, Great Britain, New York, NY, USA, and
Melbourne , Australia, 410 pp
IPCC (2005) IPCC Special Report on Carbon Dioxide Capture and Storage. Prepared by Working
Group III of the Intergovernmental Panel on Climate Change [Metz, b., O. Davidson, H.C. de Coninck,
M. Loos, and L.A. Meyer (eds.)] Cambridge University Press, Cambridge, United Kingdom and New
York, NY, USA, 442 pp
IPCC (2007) Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the
Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin,
M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University
Press, Cambridge, United Kingdom and New York, NY, U.S.A.
IPCC (2012) Managing the Risks for Extreme Events and Disasters to Advance Climate Change
Adaption [Field, C.B., Barros, V., Stocker, T.F., Qin, D., Dokken, D.J., Ebi, K.L., Mastrandrea, M.D.,
Mach, K.J., Plattner, G.-K., Allen, S.K., Tignor, M. and Midgley, P.M. (eds.)]. A Special Report of
Working Groups I and II of the Intergovernmental Panel on Climate Change. Cambridge University
Press, Cambridge, UK, and New York, NY, USA, 582 pp
IPCC (2013) Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the
Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin,
M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University
Press, Cambridge, United Kingdom and New York, NY, U.S.A.
Ishimatsu, A., Kikkawa, T., Hayashi, M., Lee, K., Kita, J. (2004) Effects of CO2 on marine fish: larvae
and adults. Journal of Oceanography 60, p. 731–741
Jeffree, R.A. (2009) Ocean acidification: a prognosis and treatment for this eclipsing issue in marine
ecotoxicology. Integrated Environmental Assessment and Management Nov 5, p. 173-175
Jones, N. (2010) Battle to degas deadly lakes continues. Nature 466, p. 1033
Jonker, T. (2013) The permitting process. Special report on getting a CCS project permitted.
Maasvlakte CCS Project C.V. January 2013
Judd, A., Long, D., Sankey, M. (1994) Pockmark formation and activity, U.K. block 15/25, North Sea.
Bulletin of the Geological Society of Denmark 41, p. 34-49
Khakzad, N., Khan, F., Amyotte, P. (2012) Dynamic risk analysis using bow-tie approach. Reliability
Engineering and System Safety 104, p. 36-44
Kharaka, Y.K., Cole, D.R., Hovorka, S.D., Gunter, W.D., Knauss, K.G., Freifeld, B.M. (2006) Gas-water-
rock interactions in Frio Formation following CO2 injection: Implications for the storage of
greenhouse gases in sedimentary basins. Geology 34, p. 577-580
Kharaka, Y.K., Thordsen, J.J., Kakouros, E., Ambats, G., Herkelrath, W.N., Beers, S.R., Birkholzer, J.T.,
Apps, J.A., Spycher, N.F., Zheng, L., Tratuz, R.C., Rauch, H.W., Gullickson, K.S. (2010) Changes in the
63
chemistry of shallow groundwater related to the 2008 injection of CO2 at the ZERT field site,
Bozeman, Montana. Environmental Earth Sciences 60, p. 273-284
Kikkawa, T., Kita, J., Ishimatsu, A. (2004) Comparison of the lethal effect of CO2 and acidification on
red sea bream (Pagrus major) during early developmental stages. Marine Pollution Bulletin 48, p.
108–110
Klusman, R.W., 2003. Rate measurements and detection of gas microseepage to the atmosphere
from an enhanced oil recovery/sequestration project, Rangely, Colorado, USA. Applied Geochemistry,
18(12), p. 1825 – 1838
Koornneef, J., Ramírez, A., Turkenburg, W., Faaij, A. (2012) The environmental impact and risk
assessment of CO2 capture, transport and storage – an evaluation of the knowledge base. Progress in
Energy and Combustion Science 38, p. 62-86
Korre, A., Imrie, C.E., May, F., Beaubien, S.E., Vandermeijer, V., Persoglia, S., Golmen, L., Fabriol, H.,
Dixon, T. (2011) Quantification techniques for potential CO2 leakage from geological storage sites.
Energy Procedia 4, p. 3413-3420
Kuijper, M. (2009) Barendrecht CO2 Opslag Project. Terugblikken en Vooruitkijken. Presentatie NL
CCS dag 15 April 2009 Margriet Kuijper, Manager CO2 Studies and Projects, Shell CO2 Storage BV
Langwaldt, J.H., Puhakka, J.A. (2000) On-situ biological remediation of contaminated groundwater: a
review. Environmental Pollution 107, p. 187-197
Mathieson, A., Midgely, J., Wright, I., Saoula, N., Ringrose, P. (2010) In Salah Storage JIP: CO2
sequestration monitoring and verification technologies applied at Krechba, Algeria. Energy Procedia
00 1063-00
Miles, N.L., Davis, K.J., Wyngaard, J.C. (2004) Detecting leaks from belowground CO2 reservoirs using
eddy covariance. In: Benson, S.M. (ed.) Carbon Dioxide Capture for Storage in Deep Geologic
Formations, Volume 2, p. 1031 – 1044. Elsevier Ltd, Oxford
Ministerie van Verkeer en Waterstaat (Directoraat-generaal Water) en ministerie van VROM
(programmadirectie Omgeveningsvergunning) (2009) De Waterwet en de Wet algemene bepalingen
omgevingsrecht (Wabo) Hoofdlijnen van de waterverguning en de omgevingsvergunning. Koninklijke
De Swart, Den Haag. Juni 2009
Ministerie van VROM (2007) Samenvatting Wetsvoorstel – wet algemene bepalingen
omgevingsrecht. Ministerie van Volkshuisvesting, Ruimtelijke Ordening en Milieubeheer.
Ministry EZ (2010) Wijziging van de Mijnbouwwet in verband met implementatie van richtlijn nr. 2009/31/EG van het Europees Parlement en de Raad van 23 april 2009 betreffende de geologische opslag van kooldioxide en tot wijziging van richtlijn 85/337/EEG van de Raad, de richtlijnen 2000/60/EG, 2001/80/EG, 2004/35/EG, 2006/12/EG en 2008/1/EG en verordening (EG) nr. 1013/2006 van het Europees Parlement en de Raad (PbEG L 140) en van Ospar Decision 2007/2 on the storage of carbon dioxide streams in geological formations. Ministerie van Ecomonische Zaken, 26 April 2010
64
Mooij, W.M., Hülsmann, S., De Senerpont Domis, L.N., Nolet, B.A., Bodelier, P.L.E., Boers, P.C.M.,
Pires, L.M.D., Gons, H.J., Ibelings, B.W., Noordhuis, R., Portielje, R., Wolfstein, K., Lammens, E.H.R.R.
(2005) The impact of climate change on lakes in the Netherlands: a review. Aquatic Ecology 39, p.
381-400
Mozaffarian, M., Horssen, van A., Lako, P., Meindertsma, W., Stortelder, B. (2011) Permitting needs
for CCS operations in the Netherlands. CATO2 Program WP4.2, 2011.12.06
Oldenburg, C.M., Lewicki, J.L., Hepple, R.P. (2003) Near-Surface Monitoring Strategies for Geologic
Carbon Dioxide Storage Verification. Earth Sciences Devision. Ernest Orland Lawrence Berkeley
National Laboratory, October 30, 2003
Oldenburg, C.M., Unger, A.J. (2004) Modeling of near-surface seepage of CO2 for risk
characterization. The CO2 capture and storage project for carbon dioxide storage in deep geological
formations for climate change mitigation. Kidlington, Oxford, United Kingdom: Elsevier
OSPAR Commission (2007) Convention for the protection of the marine environment of the North-
East Atlantic. Published 25 June 2007
http://www.ospar.org/html_documents/ospar/html/ospar_convention_e_updated_text_2007.pdf
Paulley, A., Maul, P., Metcalfe, R. (2013) Research into Impacts and Safety in CO2 Storage – Scenarios
for Potential Impacts from Hypothetical Leakage from Geological Storage Facilities for Carbon
Dioxide. Work package 1 Descriptions of Reference Environments and Scenarios. Contractor:
Quintessa Limited
Pearce, J.M. (2004) What can we learn from natural analogues? An overview of how analogues can
benefit the geological storage of CO2. In Part III Natural Analogues of CO2 Storage. The use of Natural
Accumulations of Carbon Dioxide or other Greenhouse Gases to Predict the Eventual Evolution of
Man-Made Storage Reservoirs
Pearce, J., Czernichowski-Lauriol, I., Lombardi, S., Brune, S., Nador, A., Baker, J., Pauwels, H.,
Hatziyannis, G., Beaubien, S., Faber, E. (2004) A review of natural CO2 accumulations in Europe as
analogues for geological sequestration. From: Baines, S.J., Worden, R.H. (eds.). Geological Storage of
Carbon Dioxide. Geological Society, London, Special Publications 233, p. 29-41. The Geological
Society of London 2004
Pickles, W.L., Cover, W.A. (2005) Hyperspectral Geobotanical Remote Sensing for CO2 Storage
Monitoring. In: Benson, S.M. (ed.) Carbon Dioxide Capture for Storage in Deep Geologic Formations,
Volume 2, p. 1045 - 1070. Elsevier Ltd, Oxford
Pörtner, H.O., Langenbuch, M., Reipschläger, A. (2004) Biological impact of elevated ocean CO2
concentrations: lessons from animal physiology and earth history. Journal of Oceanography 60, p.
705–718
Rausand, M. (2011) Risk Assessment: Theory, Methods, and Applications. John Wiley & Sons, Inc.,
Hoboken, New Jersey
Riebesell, U., Zondervan, I., Rost, B., Tortell, P.D., Zeebe, R.E., Morel, F.M. (2000) Reduced
calcification of marine plankton in response to increased atmospheric CO2. Nature 407, p. 364–367
65
Riebesell, U. (2004) Effects of CO2 Enrichment on Marine Phytoplankton. Journal of Oceanography
60, pp. 719-729
ROAD Project (2013) Case study of the ROAD storage permit. A report by the ROAD project – part of
the European CCS Demonstration Project Network. June 2013
Roggenkamp, M.M., Graaf, K.J. de, Holwerda, J.M. (2010) Afvang, transport en opslag van CO2. De
implementatie van Richtlijn 2009/31/EG in Nederland. Milieu & Recht jaargang 37, nummer 7
Rooijen, van T. (2011) Implementatie van de CCS-richtlijn in Nederland. Naar een integrale aanpak van CO2-opslag? Scriptie Master Omgevingsrecht UvA.
Saripalli, K.P., Mahasenan, N.M., Cook, E.M. (2003) Risk and Hazard Assessment for Projects
Involving the Geological Sequestration of CO2. Sixth International Conference on Greenhouse Gas
Control Technologies, Kyoto, vol 1, pp. 511-516
Schmid, M., Lorke, A., Wüest, A., Halbwachs, M., Tanyileke, G. (2003) Development and sensitivity
analysis of a model for assessing stratification and safety of Lake Nyos during artificial degassing.
Ocean Dynamics 53, p. 288-301
Schneider von Deimling, J., Brockhoff, J. & Greinert, J. (2007) Flare imaging with multibeam systems:
Data processing for bubble detection at seeps. Geochemistry, Geophysics, Geosystems, Vol. 8,
Q06004
Schroot, B.M., Schüttenhelm, R.T.E. (2003) Expressions of shallow gas in the Netherlands North Sea.
Netherlands Journal of Geosciences / Geologie en Mijnbouw 82, p. 91-2105
Smid, E., Mazot, A. (2012) Soil Gas CO2 Concentrations & CO2 Fluxes in the Auckland Volcanic Field.
Institute of Earth Science and Engineering, Aotearoa, Auckland. Report 1-2011.02
Solomon, S. (2007) Carbon Dioxide Storage: Geological Security and Environmental Issues – Case
Study on the Sleipner Gas field in Norway. Bellona Report, May 2007
Spence, B. (2012) CCS Community outreach – Shell’s experience. Carbon Sequestration Leadership
Forum. Perth, WA. October 26, 2012
Strutt, M. H., Beaubien, S. E., Baubron, J.-C., Brach, M., Cardellini, C., Granieri, R., Jones, D. G.,
Lombardi, S., Penner, L., Quattrocchi, F. & Voltatorni, N. (2003) Soil gas as a monitoring tool of deep
geological sequestration of carbon dioxide: preliminary results from the EnCana EOR project in
Weyburn, Saskatchewan (Canada). In: Gale, J. and Kaya, Y. (Editors) Greenhouse Gas Control
Technologies, Volume I. Elsevier Science Limited, Oxford, pp. 391 – 396.
UNFCCC (2014) Essential Background. From website United Nations Framework Convention on
Climate Change © 2014 http://unfccc.int/
United Nations University (2009) EIA Environmental Impact Assessment. Website United Nations
University. Last modified on 31 May 2009, http://eia.unu.edu/
Van Eijs, R., Kuijper, M., Bisschop, R. (2011) Containment demonstration for the Barendrecht CO2
storage project. GHGT-10. Energy Procedia 4, p. 4092–4099
66
Veer, M.A.C. (1997) Nitrogen availability in relation to vegetation changes resulting from grass
encroachment in Dutch dry dunes. Journal of Coastal Conservation 3, p. 41-48
Vidic, R.D., Pohland, F.G. (1996) Treatment Walls. Ground-water Remediation Technologies Analysis
Center. University of Pittsburgh. Technology Evaluation Report TE-96-01
Whaley, J. (2009) The Groningen Gas field. GeoExpro issue 4. Volume 6, 2009
Widdicombe S., Spicer, J.I. (2008) Predicting the impact of ocean acidification on benthic biodiversity:
What can animal physiology tell us? Journal of Experimental Marine Biology and Ecology 366, pp.
187-197
Widdicombe, S., Dashfield, S.L., McNeill, C.L., Needham, H.R., Beesley, A., McEvoy, A., Øxnevad, S.,
Clarke, K.R., Berge, J.A. (2009) Effects of CO2 induced seawater acidification on in faunal diversity and
sediment nutrient fluxes. Marine Ecology Progress Series 379, p. 59-75
Wildenborg, T., Scheffers, B., Ribberink, H., Schrovers, J. (2003) Framework for the and monitoring of
a facility for underground CO2 sequestration. TNO-NITG and safety ECN, may 2003
Wo, S., Lian, J.T. (2005) CO2 storage in coalbeds: CO2/N2 injection and outcrop seepage modeling.
Carbon Dioxide Capture for Storage in Deep Geologic Formations 2, p. 897-924
Yavuz, F., van Tilburg, T., David, P., Spruijt, M., Wildenborg, T. (2008) Second Generation CO2 FEP
Analysis: CASSIF – Carbon Storage Scenario Identification Framework. Energy Procedia 00
Ziogou, F., Gemeni, V., Koukouzas, N., de Angelis, D., Libertini, S., Beaubien, S.E., Lombardi, S., West,
J.M., Jones, D.G., Coombs, P., Barlow, T.S., Gwosdz, S., Krüger, M. (2013) Potential environmental
impacts of CO2 leakage from the study of natural analogue sites in Europe. Energy Procedia 37, p.
3521-3528
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Appendices
Appendix 1 Legal aspects This appendix will provide a legal framework for some aspects of the treatment of environmental
risk and damage as a consequence of CO2 leakage from storage reservoirs. The provided framework
in this appendix is relevant for the chapters in this report.
It should be stated that the legal situation around CO2 storage is very complex, because the projects
are related to for example mining, environmental and spatial aspects (AMESCO, 2007). Furthermore,
the legal situation on CO2 storage projects is also very dependent on site specific characteristics. This
appendix will give some examples of legal aspects that interface the content of this thesis. It is not
the purpose of this appendix to give an exhaustive conclusive analysis of all aspects of regulation and
legislation concerning CO2 storage since that is beyond the scope of this research.
Research Question:
What are some of the regulatory requirements for the treatment of threats to the environment caused by CO2 storage that interface this study?
First, some of the relevant International regulations, European directives and national legislations
will be mentioned. Subsequently, some elements of the main European directive on CCS will be
explained and how some of these elements are translated into Dutch law. This appendix will also
some of the relevant permits from Dutch legislation and some of the permitting requirements for
dealing with the threat of environmental damage will be presented. In a conclusive paragraph it will
be explained what has to happen when leakage does take place and who is responsible or liable for
the measures that have to be taken.
1.1 Relevant legislation
Some main environmental regulations for Dutch CCS Projects are governed by the 1996 London
Protocol1, the OSPAR2, the European CCS Directive3, the Water Framework Directive4, the
Groundwater Directive5, the Waste Framework Directive6, the General Environmental Conditions Act
(‘Wabo’ in Dutch), and the Mining Act (Mijnbouwwet), Mining Decree (Mijnbouwbesluit) and Mining
Regulation (Mijnbouwregeling) (Hans et al., 2011, Global CCS Institute, 2014).
The 1996 London Protocol and the Convention for the Protection of the Marine Environment of the
North-East Atlantic (OSPAR Convention) are examples of legal barriers at the international level. In
2006 the London Protocol was amended so that the dumping of carbon dioxide for geological
sequestration may be considered7. In 2007 Annex II and Annex III of the OSPAR Convention were
11996 Protocol to the convention on the prevention of Marine pollution by dumping of wastes and other matter, 1972. As
amended in 2006 http://www.gc.noaa.gov/documents/gcil_lp.pdf 21992 OSPAR Convention Annex III, Article 3(3)
3 Directive 2009/31/EC of the European Parliament and of the Council on the geological storage of carbon dioxide and
amending Council Directive 85/337/EEC, European Parliament and Council Directives 2000/60/EC, 2001/80/EC, 2004/35/EC, 2006/12/EC, 2008/1/EC and Regulation (EC) No 1013/2006 4 Directive 2000/60/EC
5 Directive 2006/118/EC
6 Directive 2006/12/EC
7 Annex I Protocol to the convention on the prevention of Marine pollution by dumping of wastes and other matter
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amended by adding ‘carbon dioxide streams from carbon dioxide capture processes for storage’ to
the list of matters that are excepted from the prohibition of dumping8(OSPAR Commission, 2007).
At the European level the legislation for CCS projects is mainly based on the European CCS Directive.
The main purpose of the CCS Directive is stated in Article 1(2):
“The purpose of environmentally safe geological storage of CO2 is permanent containment of CO2 in
such a way as to prevent and, where this is not possible, eliminate as far as possible negative effects
and any risk to the environment and human health.”9
When following the European Water Framework Directive and the Groundwater Directive the
injection of CO2 in the subsurface would have been prohibited. However the CCS Directive amended
the Water Framework-, and the Groundwater Directive and states that CO2 injection must be in
accordance with the protection of groundwater provisions10 (Global CCS Institute, 2014).
If an operator is planning a CCS activity in the Netherlands, the operator has a reporting requirement
to the European Commission about their planned CCS activities11. The European Commission will
review the plans from the operator for CO2 storage and may give an opinion. If the competent
authority, who decides on the granting of permits, deviates from the opinion, it shall inform the
Member State and state its reasons for their decision12. The advice from the European Commission is
to regulate consistency with regard to permitting CCS projects over the entire European Union (Hans
et al., 2011).
The competent authority within the Netherlands with regard to the relevant permits and plans for
the CCS projects is the Minister of Economics13.
About 80% of Dutch legislation on the environment is derived from EU legislation (government.nl,
2014). The Dutch environmental legislation for CCS projects is mainly based on the European CCS
Directive. In the Netherlands the CCS Directive was implemented entirely and almost literally into
the Dutch legislation and does not include additional requirements (Henry et al., 2011). This is in
favor of CCS project developers since every CCS project has its own specific characteristics. In order
to have a proper assessment of a project proposal, a tailor-made approach is essential (Henry et al.,
2011).
1.2 Permits & permitting process
Before an operator of a CO2 storage project is allowed to store CO2 in the subsurface the Dutch law
requires some permits to be obtained. Based on the permitting process as described by reports from
the ROAD project, the Netherlands there are two permits required for the storage of CO2 in the P18
formation offshore of the Netherlands14 (Henry et al., 2013). In the case of the ROAD project the two
permits are the storage permit and the ‘all-in-one permit for physical aspects’ (part of the Mining Act
and the General Environmental Conditions Act respectively). As part of the permitting process the
8 Annex II Article 3(2f) and Annex III Article 3(3) of the 1992 OSPAR Convention
9 Article 1(2) Directive 2009/31/EC
10 Directive 2009/31/EC (46); Article 4(1)(b) Directive 2000/60/EC
11 Article 10 Directive 2009/31/EC
12 Article 10 Directive 2009/31/EC
13 Article 1(p) Mining act: “Onze Minister: Onze Minister van Economische Zaken”
14 Staatscourant 2013, nr. 21233: Vergunning voor de opslag van kooldioxide in het voorkomen P18-4, Ministerie van
Economische Zaken
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submitting party has to meet certain requirements which are set out to assure efforts are made to
prevent damage to the environment. If no environmentally safe storage can be promised no permit
will be granted15. The following paragraphs will describe the storage permit and the all-in-one permit
for physical aspects and some of the permitting requirements that have to be developed for
preventing environmental damage.
1.2.1 The Mining Act & the storage permit
In March 2010 the Mining Act has been amended as a consequence implementation requirements
set out by the CCS Directive and the OSPAR Decision 2007/216 (Ministry EZ, 2010). As mentioned in
the introduction, the CCS Directive was implemented almost literally into the Dutch legislation,
particularly in the Mining Act. The new Mining Act was approved and entered into force on
September 10th 2011. The Mining Act is complemented by a Mining Decree and a Mining Regulation,
which set out requirements for the geological storage of CO2.
The Mining Act prohibits the storage of CO2 without a storage permit17. A storage permit can only be
granted if the permitting procedure has showed that there is no significant risk for leakage and no
significant environmental and health risks (Roggenkamp et al, 2010). Based on article 31b of the
Mining Act a request for a storage permit for permanent storage of CO2 should (amongst more
aspects) at least include information on characterization of the storage site and assessment of the
expected safety of storage, monitoring, closure and corrective measures (Hans et al., 2011; Henry et
al., 2011; Rooijen, 2011)18.
Besides the Mining Act, there are a large number of other Dutch Acts also applicable to Mining
activities. One of those is the General Environmental Conditions Act.
1.2.2 The General Environmental Conditions Act & the all-in-one permit for physical aspects
The Dutch General Environmental Conditions Act, which entered into force on 1 October 2010, also
requires a permit for the storage of CO2. This Act replaced 25 environmental permits for an all-in-
one permit for physical aspects. The objective was to simplify the application process for large
projects such as CO2 storage (Ministerie van VROM, 2007). Several environmental permits from
different acts are implemented in the General Environmental Conditions Act, which include, the
mining environmental permit, the permit for indirect discharges, and the environmental permit
(Ministerie van Verkeer en Waterstaat et al., 2009).
Relevant permitting requirements that are set out by the General Environmental Conditions Act for
mining activities are requirements to monitor, control and manage negative effects from the mining
activity to the environment19.
15
Article 2.14(1) Wabo; Article 27(3a) Mining act: “bij opslag onder de voorgestelde exploitatievoorwaarden een significant risico van lekkage bestaat of significante milieu- of gezondheidsrisico’s bestaan,” 16
OSPAR Decision 2007/2, On the storage of carbon dioxide streams in geological formations, OSPAR 07/24/1, Annex 6 17
Wet van 31 oktober 2002, houdende regels met betrekking tot het onderzoek naar en het winnen van delfstoffen en met betrekking tot met de mijnbouw verwante activiteiten (Mijnbouwwet), Article 25(1): “Het is verboden zonder vergunning van Onze Minister: a. stoffen op te slaan; b. CO2-opslagcomplexen op te sporen” 18
Mijnbouwwet Article 31b: “Een aanvraag om een vergunning voor permanent opslaan van CO2 omvat ten minste de volgende onderwerpen…” 19
Article 2.14(6) Wabo: “het systeem van met elkaar samenhangende technische, administratieve en organisatorische maatregelen om de gevolgen die de inrichting of het mijnbouwwerk voor het milieu veroorzaakt, te monitoren, te
70
A decision to develop an environmental impact assessment is also set out in the General
Environmental Conditions Act20, where it refers to the Dutch Environmental Management Act. The
content of the required monitor, control and manage activities and the environmental impact
assessment are set out in the next paragraph.
1.2.3 Permitting requirements
As mentioned in paragraph 1.2.1 and 1.2.2 the procedures for obtaining an all-in-one permit for
physical aspects and a storage permit require the development of different requirements. The
following relevant permitting requirements that deal with the threat of environmental damage
caused by CO2 leakage will be further explained:
Environmental Impact Assessment
Characterization of the storage site and assessment of the expected safety of storage
Monitoring Plan
Corrective Measure Plan
Closure Plan
There is a great consistency between these plans, especially between the characterization of the
storage site and assessment of the expected safety of storage, the Monitoring Plan, the Corrective
Measure Plan and the Closure Plan (Henry et al., 2011). The relations between the plans are
schematically shown in figure 1 and further explained in the next paragraphs.
FIGURE 1 RELATIONS BETWEEN DIFFERENT PERMITTING REQUIREMENTS (BASED ON HENRY ET AL., 2011)
Environmental Impact Assessment
A required procedure in the preparation of the permitting process for the all-in-one permit for
physical aspects, and according to the requirements of the storage permit, is the development of an
beheersen en, voor zover het nadelige gevolgen betreft, te verminderen, dat degene die de inrichting of het mijnbouwwerk drijft, met betrekking tot de inrichting of het mijnbouwwerk toepast, alsmede het milieubeleid dat hij met betrekking tot de inrichting of het mijnbouwwerk voert” 20
Article 3.1(15) Wabo: “Indien bij de voorbereiding van de beslissing op de aanvraag een milieueffectrapport moet worden gemaakt, is artikel 13.2 van de Wet milieubeheer van toepassing.”
71
Environmental Impact Assessment (EIA)(EC, 2009; Mozaffarian et al., 2011; Hans et al., 2011). The
general requirements for the aspects that should be in an EIA are provided by the Dutch
Environmental Management Act, which are based on the European EIA Directive21 and referred to by
Article 31 of the CCS Directive. The main goal of the EIA is to assess and evaluate possible
environmental effects of a proposed CCS project (EC, 2009; Mozaffarian et al., 2011; Hans et al.,
2011). An EIA should also propose a set of reasonable alternatives that show less negative
environmental effects. Whether an alternative is preferred, depends on the cost/benefit ratio
(United Nations University, 2009; Hans et al., 2011). In appendix 1B a schematic overview of the
common structure of an EIA process is shown.
Because of possible effects on the conservation of Natura 2000-areas, Nature assays are to be
prepared. A Nature Assay is an integral part of the EIA and can prevent the permits from being
granted if the impact on protected nature areas is too severe (AMESCO, 2007; Hans et al., 2011).
Characterization and Assessment of the storage site
Article 1.3.4a(1a) of the Mining Regulation states that the characterization of the storage site and
the assessment of the expected safety of storage should be carried out as is described in detail in
Annex I of the CCS Directive. It is build up in 3 steps:
Step 1: Data collection; in this step aims enough data is collected to construct a volumetric and
three-dimensional static model of the storage site, including the caprock and the surrounding area22.
Step 2: Building the three-dimensional static geological model; this step uses the data that is
collected in Step 1 to develop a three-dimensional static geological model with reservoir simulators.
The model is made to characterize the storage area23.
Step 3: Characterization of the storage dynamic behavior, sensitivity characterization and risk
assessment; The characterizations and assessment shall be based on dynamic modellings, which
consists of time-step simulations of CO2 injection into the storage site and using the three-
dimensional static geological model developed in step 2 as input. The risk assessment specifically
consists of a hazard characterization, an exposure assessment, an effects assessment and a risk
characterization24.
Annex I in the CCS Directive shows a detailed list of specific criteria for the characterization and
assessment of the storage site.
Monitoring plan
Monitoring measures are also part of the permitting requirements25. Since the monitoring plan is risk
based it is related to the risk assessment that has been carried out under the development of the
previous described plan. Article 1.3.4a(4) of the Mining Regulation refers to Annex II of the CCS
Directive where more details on what a monitoring plan should entail are described26:
21
Directive 2011/92/EU of the European Parliament and of the Council on the assessment of the effects of certain public and private projects on the environment 22
Directive 2009/31/EC Annex I 23
Directive 2009/31/EC Annex I 24
Directive 2009/31/EC Annex I 25
Article 31b Mining Act; Article 2.14(6) Wabo; Directive 2009/31/EC Article 13(1) 26
Directive 2009/31/EC Article 13(1)
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“(a) comparison between the actual and modelled behavior of CO2 and formation water, in the storage site; (b) detecting significant irregularities; (c) detecting migration of CO2; (d) detecting leakage of CO2; (e) detecting significant adverse effects on the surrounding environment, including in particular on drinking water, for human populations, or for users of the surrounding biosphere; (f) assessing the effectiveness of any corrective measures taken pursuant to Article 16; (g) updating the assessment of the safety and integrity of the storage complex in the short and long term, including the assessment of whether the stored CO2 will be completely and permanently contained.” The monitoring plan will be established including baseline, operational and post-closure monitoring.
This plan will be compared to the behavior as predicted by the three-dimensional static geological
earth model, and consequently the model will be recalibrated if necessary27.
Corrective measure plan
Corrective measures are defined in Article 3(19) of the CCS Directive as “any measures taken to
correct significant irregularities or to close leakages in order to prevent or stop the release of CO2
from the storage complex”28. To prevent worsening of leakage an ‘early warning’ and ‘early
intervention’ aspect is added to the corrective measure plan. The corrective measure plan is closely
linked to the monitoring plan and the characterization and assessment of the storage site, since the
plan has to be developed based on the risk assessment that is carried out in the characterization and
assessment of the storage site phase (Henry et al., 2011).
Closure plan
When the injection of CO2 filled up the storage reservoir, the site will be closed provided one of the
following conditions according to Article 17(1) of the CCS Directive: “(a) if the relevant conditions
stated in the permit have been met;(b) at the substantiated request of the operator, after
authorisation of the competent authority; or(c) if the competent authority so decides after the
withdrawal of a storage permit pursuant to Article 11(3)” 29.
During the application for the permits a closure plan has to be developed showing that safe
abandonment is possible on basis of the current technology and experience (Jonker, 2013). In the
monitoring plan and the corrective measure plan, measures are described that also apply to the
period after the closure of the side.30 Information on the liability of the period after the closure of
the site is provided in the next paragraph.
1.3 Transfer of responsibility and Environmental liability
The Dutch legal liability knows some specific provisions concerning leakage of CO2 storage. Some of
these provisions will be described here. In principle, all the national legal liability remains applicable,
both criminal law, civil law, and administrative law.
27
Directive 2009/31/EC Annex II 28
Directive 2009/31/EC Article 3(19) 29
Directive 2009/31/EC: Article 17(1) 30
Directive 2009/31/EC Annex II; Directive 2009/31/EC Article 3(19)
73
After the closure of a storage reservoir the operator remains responsible for the stored CO2 for
(normally) at least 20 years31. After this period the responsibility is transferred to the competent
authority once the following four conditions are met according to Article 31j of the Mining Act:
“all available evidence indicates that the stored CO2 will be completely and permanently contained;
(b) a minimum period, to be determined by the competent authority has elapsed. This minimum
period shall be no shorter than 20 years, unless the competent authority is convinced that the
criterion referred to in point (a) is complied with before the end of that period;
(c) the financial obligations referred to in Article 20 have been fulfilled;
(d) the site has been sealed and the injection facilities have been removed.” 32
From this point the competent authority is obliged to take corrective measures in case of leakages or
significant irregularities on the basis of the submitted corrective measures plan33. However, if the
(immediate threat of) environmental damage occurs due to negligence of the operator, the operator
is obliged to have immediate preventive and corrective measures at hand (ROAD Project, 2013). If
damage occurs due to negligence of the operator, the costs of the measures takes should be
recovered from the operator34.
1.4 Discussion and conclusion
The legal situation on CO2 storage projects is really complex and entails many International, European and nationals aspects.
Most of the Dutch legislation of CO2 storage is based on the CCS Directive. The permits that have been described in this appendix are based on the permitting process
of the ROAD project. It is acknowledged that the ROAD project is an offshore project and that if CO2 is to be stored in an onshore storage site potentially more permits are required.
It is also acknowledged that for the Capture and Transportation aspects of a CCS project, more permits are required. Since this report does only focus on the storage part of a CCS project, the other permits are not mentioned.
Permits that have been obtained for the ROAD CO2 storage project are the storage permit and the all-in-one permit for physical aspects.
As a part of the permitting process it is required to develop certain plan. Some of these plans are the Environmental Impact Assessment, a characterization of the storage site and assessment of the expected safety of storage, a monitoring plan, a corrective measure plan, and a closure plan. There is consistency between these plans as illustrated in figure 1.
After the closure of a storage site, the operator remains responsible for the monitoring and the corrective measures for a period of normally at least 20 years. After this period the responsibility can be transferred to the competent authority (which is the Minister for CO2 storage in the Netherlands).
If leakage from a storage site does occur all national legal liabilities apply in principle.
31
Mijnbouwwet Article 31j (1c): “na het tijdstip waarop het opslagvoorkomen is afgesloten en de bijbehorende bovengrondse voorzieningen en injectiefaciliteiten zijn verwijderd een periode van tenminste 20 jaar is verstreken of zoveel korter of langer als naar het oordeel van Onze Minister, gelet op onderdeel a, verantwoord is” 32
Mijnbouwwet Article 31j; Directive 2009/31/EC: Article 18(1) 33
Mining Act Article 31k (1.): “Met ingang van het tijdstip waarop een vergunning ingevolge artikel 31j is ingetrokken, is Onze Minister belast met: a. monitoring, b. corrigerende maatregelen en c. de preventieve en herstelmaatregelen” 34
Mijnbouwwet Article 31k (5.): “Onze Minister verhaalt de kosten die samenhangen met het eerste lid en zijn ontstaan na intrekking van de vergunning op de voormalige houder van een vergunning voor permanent opslaan van CO2 of, indien de vergunning door meerdere personen wordt gehouden, een aangewezen persoon als bedoeld in artikel 22 voor zover hij niet zorgvuldig heeft gehandeld in de periode voorafgaande aan de intrekking van de opslagvergunning.”
74
The interface between the aspects mentioned in this appendix and the aspects described in the report are illustrated in figure 5.1. The reason why in this study research has been done into identifying and managing possible effects of CO2 storage on the environment is not only because of personal interest and human concerns, but also because of permitting requirements. The Environmental Impact Assessment and the characterization of the storage site and assessment of the expected safety of storage are in compliance with chapter 2 of this report (identifying the consequences). The monitoring plan is in compliance with chapter 3 (monitoring measures). Finally the 4th chapter of this report shows an interface with the development of a corrective measure plan.
75
Appendix 1B
76
Appendix 2
CO2 from deep stably stratified lakes
There have been serious incidents in the past in volcanic areas, with rapid emissions of large
masses of CO2 resulting in major losses of life. In 1972 the Dieng volcano in Indonesia released a
cloud of CO2 before it erupted. This cloud asphyxiated 142 people (Holloway et al., 2005).
Two other examples of natural incidents with large releases of CO2 are incidents in Cameroon.
The death of 37 people in 1984 was caused by a CO2 release from lake Monoun in Cameroon. The
largest incident in the past occurred in 1986. Natural occurrences of CO2 had been seeping into
lake Nyos from deep magma below. Since the lake was deep and stably stratified it could
accumulate and form a dense, gas-filled water layer trapped at the bottom. Due to a triggering
event in 1986, possibly a landslide or heavy rainfall, this CO2 layer was suddenly released out of
the lake. A heavy cloud of CO2 moved over the surface, down into the valley, asphyxiating more
than 1700 people, as well as all the cattle, birds and insects (Schmid et al., 2003; Holloway et al.,
2005). In 2001, a team of scientists developed a mitigation technique to degas the lake, in order
to prevent this event from occurring again. A pipe was inserted into the middle of the lake and by
using a small pump, the deep water was raised to a level where it becomes oversaturated with
gas. Due to the pressure differential, a self-sustaining fountain of gas-rich water will stream up,
diffusing the CO2 away into the atmosphere (Picture 2.1) (Holloway, 2000; Schmid et al., 2003;
Holloway et al., 2005; Jones, 2010). This technique succeeded and the lake has been declared
safe (Jones, 2010). Since this technique has proved its functionality for Lake Nyos, it is a
promising technique for the leakage of CO2 from storage sites when it would accumulate in
bottom stratigraphic layers of a sea or lake. Nevertheless, this case is not considered relevant for
CO2 storage project for the Netherlands specifically, since deep stably stratified lakes or seas do
not exist in this country.
PICTURE 2.1 LAKE NYOS WITH ITS DEGASSING FOUNTAIN (FROM GON-CLUB.COM)
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Appendix 3A
Both onshore & offshore monitoring techniques
The monitoring techniques we found that are applicable for both onshore and offshore monitoring
as shown in figure 1 will be briefly described.
Bubble stream detection
This technique is used in the fishery to detect fish-shoals with sonar systems. This sonar system is
changed into a bubble stream detecting system. With the detection of bubble stream potential CO2
leakage pathways from the seabed can be identified. The technique can also be used for onshore
storage sites if they are overlain by for example lakes (Schneider von Deimling et al., 2007).
Downhole Fluid Chemistry
By frequently measuring the properties of samples of formation water along
the borehole, leaking of CO2 along the borehole can be detected. Examples
of measurable properties are pH, pCO2, alkalinity, dissolved gases,
hydrocarbons, cations and stable isotopes (Kharaka et al., 2006). Samples
can be obtained by the use of a specially produced U-tube that will be placed
in the borehole as shown in figure 4A1. Downhole fluids can enter the U-
tube through the inlet filter. The fluid is forced through the Ball Check Valve
by hydrostatic pressure. This check valve closes when the hydrostatic head in
the tubing equals the hydrostatic head in the reservoir. The sample is
recovered by pressurizing the drive leg and collecting the fluid from the
sample leg (Freifeld et al., 2008). To observe changes in the fluid
composition, samples have to be obtained before injection for baseline
geochemical characterization, during the injection, and after injection
(Kharaka et al., 2006). According to a research by IEAGHG (2012) the
downhole fluid chemistry measurements are suitable to detect intermediate
(100kg/day) and high (100ton/day) leakage rates.
Downhole Pressure and Temperature measurements
If the pressure and temperature in the storage reservoir will increase, the
cap can become critical and leakage of CO2 will result. Therefore, monitoring
changes in pressure and temperature down the well is highly recommended
(Carlsen et al., 2001; Freifeld et al., 2008). This technique is an indirect
indicator of leakage of CO2.
Ecosystem monitoring
Ecosystem monitoring can be done on terrestrial environments by studies on vegetation, with the
help of remote sensing techniques (see 4.3.2.7). The goal is to identify locations where plant stress is
severe. A shortcoming of this approach is the variability of plant growth with seasonal changes, or
plant stress induced by unrelated processes, such as flooding, and soil dryness (Bateson et al., 2008).
Offshore ecosystem monitoring can be done by identifying the lack of original species and/or the
abrupt emerging of non-native algal species (Hall-Spencer et al., 2008). In general, indicator species
(that experience stress in high acid surroundings, or prosper with high acid surroundings), have to be
identified. However this will be very site-specific (Paulley et al., 2013). Ecosystem monitoring is a
FIGURE 4A1 DOWNHOLE
MONITORING
INSTRUMENT: U-TUBE
(FREIFELD ET AL., 2008).
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technique which has to be used in combination with other monitoring techniques (for example gas
sampling) to verify the cause the stress (Korre et al., 2011; IEAGHG, 2012).
For low leakage rates (100g/day), the sensitivity of ecosystem monitoring is not applicable, since
ecosystems are suspected to be able to cope with low leakage rates. Intermediate leakage rates
(100kg/day) are possible suitable to monitor with ecosystem monitoring, although it will be site
dependent.
Fluid geochemistry
To keep track of changes to (sub-) surface water quality as a consequence of leakage from CO2
fluxes, measuring the amount of CO2 dissolved in groundwater is a straight-forward procedure.
There are specialized geochemical speciation computer codes that can measure the different
composition of dissolved carbon (Gambardella et al., 2004). Some chemical compositions of
dissolved carbon are for example, dissolved CO2, bicarbonate ions (HCO3-), carbonate ions (CO3
2- ),
and other complexes (IEAGHG, 2013).
High resolution acoustic imaging
This is a very high frequency seismic method that offers high resolution profiles of surface
morphology. It observes expressions like pockmarks (which are geomorphologic features at the
seabed or surface that are indicative for seeping of gas) and phenomena that are efficient in
trapping gas in reservoir sand. This techniques is potentially very useful for shallow storage
monitoring when used in combination with other techniques to verify that the cause of the
monitored changes to the seabed/surface are due to CO2 leakage (Schroot, B.M. et al., 2003).
Surface gravimetry
This method measures the gravitational acceleration that is caused by distributions within the Earth.
By measuring the gravitational acceleration variations in subsurface rocks and fluid density can be
measured and thereby mass changes can be detected. These mass changes can be a result of
possible CO2 leaks into the overburden (Hagen et al., 2012; IEAGHG, 2013). To check if the changes
are really caused by CO2 leakage, this technique has to be combined with other monitoring
techniques (e.g. time-lapse 3D surface seismic).
Time-lapse 3D (or 4D) surface seismic
By using multiple seismic sources and receivers, 3D surface seismic is a technique that can produce a
full volumetric image of the subsurface structures and the reservoir. When applying 3D surface
seismic method in time-lapse mode (so also called 4D) a number of repeated surveys are done,
enabling to map changes in fluid distribution through time (IEAGHG, 2013). Although this monitoring
technique is considered of primary use for deep monitoring of plume detection, it could also be used
for detecting leakages into the shallow subsurface and atmosphere. This technique has proven its
functionality for plume detection at the Sleipner field, but its functionality for the shallow subsurface
and atmosphere monitoring has not yet been shown (Chadwick et al., 2006; Korre et al., 2011;
IEAGHG, 2012). Nevertheless, it is a technique that can be used complementary to shallow
subsurface and atmosphere monitoring techniques to verify the cause of monitored changes in the
shallow subsurface and atmosphere.
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Appendix 3B
Onshore specific monitoring techniques
Airborne Electro-magnetic
Airborne electro-magnetic technique has been used to detect conductivity anomalies that are
related with polluted plumes from mineral waste masses in the groundwater. Since CO2 is
electrically resistive, conductivity changes occurring in the groundwater as a result of dissolved CO2
can potentially be identified by this technique as well (IEAGHG, 2013).
Airborne multispectral and hyperspectral remote sensing of vegetative stress
As increased CO2 concentrations in the soil can have serious effects on vegetation health, the
mapping of areas where CO2 leaks could be expected brings useful information. Changes to health
can be seen in both the visible (for example, dead tree) and near infrared wavelength ranges (by
observing chlorophyll content). These changes can be mapped with remote sensing techniques
(Pickles et al., 2005; Bateson et al., 2007; IEAGHG, 2013). This technique will have to be combined
with soil gas sampling to verify the cause of these changes (Korre et al., 2011; IEAGHG, 2012).
Eddy Covariance
The eddy covariance is a micrometeorological method that is extensively used in meteorology and
ecology studies to observe the CO2 exchange between vegetation and the atmosphere. The
technique uses an infra-red detector to detect CO2 from an upwind area and combines the
concentrations with meteorological information. This way data can be produced about the amount
of CO2 released per unit area per unit time, i.e. the flux (Miles et al., 2005; IEAGHG, 2013). This
technique is able to detect leakage over an area of several km2, but is less capable of quantifying
leakage rates (Miles et al., 2005; IEAGHG, 2012).
Electric spontaneous potentials
Fluids flowing through porous media generate electric potentials. The potential and fluid flux can be
related by coupled flow equations. A technique to measure these potentials is already routinely used
for locating leaks in fluid containment of dams. The technique shows potential for detecting CO2
leaks as well, but will need to be adjusted before it can be used (Hoverstein et al., 2005; IEAGHG,
2013).
Ground Penetrating Radar
Ground penetrating radar is a geophysical method which uses radio waves to map shallow
subsurface and atmosphere structures. It is a widely used method to evaluate water content in the
vadose zone and has been used to map CO2 concentrations in a peatland areas (Comas et al., 2005).
Although not yet applied, it shows potential identify CO2 leakage in the shallow subsurface and
atmosphere (IEAGHG, 2013).
Infrared Diode laser or Long Open Path IR and Tunable Lasers
With the use of an infra-red (IR) diode laser instrument it is possible to analyze samples from the
atmosphere. By selecting the IR-laser wave length, the number of CO2 molecules over a linear open
path can be measured and thereby an increase in CO2 concentration/flux from the surface can be
identified (Cuccoli et al., 2000; Belotti et al., 2003).
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Infrared Gas Analyzer
The Infrared Gas Analyzer is a device commonly used to measure CO2 concentration in subsurface or
atmosphere. The analyzer bases the presence of CO2 in air by measuring light absorption in the near
infrared part of the spectrum (IEAGHG, 2013).
Soil gas sampling
This technique simply is the collection of concentrations of CO2 in the soil. There is a lot of
experience in the monitoring of soil gas concentrations (Klusman, 2003; Strutt et al., 2003).
Dependent on the natural background fluctuations, this monitoring technique can measure very low
leakage rates (IEAGHG, 2012). A negative point of this method is that it is an inefficient method if
large areas must be covered, and also requires a lot of man-hours for the collection of the samples
(IEAGHG, 2013).
Surface Electro Magnetics
Surface electromagnetic surveys involve a towed electromagnetic source and a series of receivers
that measure induced electrical and magnetic fields. The measured information can be used to
interpret electrical profiles in the subsurface that potentially will be influenced by resistive CO2
These can be used to determine subsurface electrical profiles that may be influenced by the
presence of highly resistive CO2 (Korre et al., 2011; IEAGHG, 2012; IEAGHG, 2013).
Surface gas flux
The rate of CO2 seeping out of the soil will be measured by placing accumulation chambers on the
surface. The gas within this chamber will be analyzed using a closed-path infra-red gas analyzer in
order to detect CO2. Since soil naturally has concentration fluctuations of CO2, baseline
measurements are required (Klusman, 2003).
Trained Animals
Animals are known to have the potential to be trained in detecting specific substances. For example,
specialized dogs are trained for finding landmines, since they are able to locate odorant molecules
even with the presence of significant background chemicals (Habib, 2007; Harper et al., 2007). This
ability of specialization shows promising potential for the training of an animal to learn to detect CO2
leakages. Mosquitos are able to find animals by tracing the CO2 plumes that are exhaled (Oldenburg
et al., 2003). So far, no experiments have been done for the development of this technique
(Oldenburg et al., 2003).
Vertical seismic profiling (or crosswell seismic imaging)
To give an early warning of potential leakage from CO2 along a well, vertical seismic profiling is an
promising technique. The technique uses multiple seismic sources to produce a high seismic
resolution image around the well (IEAGHG, 2013)
Appendix 3C
Offshore specific monitoring techniques
Boomer/sparker profiling
Digital seismic reflection (boomer) profiles constitute a high frequency seismic technique that can
give high resolution 2D images of the shallow subsurface and atmosphere (Judd et al., 1994). Using
time-lapse datasets, migration and leakage of CO2 may be detected (IEAGHG, 2013).
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Bubble stream chemistry
With the use of an inverted funnel bubbles of gas escaping into a water column can be collected. By
applying routine analytical techniques, for example gas chromatography mass spectroscopy,
portable IR gas analyzers (see paragraph ‘infrared gas analyzer’ in Appendix B), the composition of
the bubbles can be determined. Locating the exact point of bubble escape will require the use of
additional techniques, such as high resolution acoustic imaging (under Appendix A)(IEAGHG, 2013).
Multibeam echo sounding
The combination of acoustic imaging and backscatter information is called multibeam echo
sounding. With this technique it is possible to make a detailed map of the morphology of the
seabed. If this technique is used in time-lapse mode it can detect very small changes in the
topography of the seabed that could occur as a consequence of CO2 leakage (IEAGHG, 2013). It can
also be used in identifying bubble plumes as described under paragraph ‘bubble stream chemistry’
(IEAGHG, 2013).
Seabed Electro Magnetic
Sea surface electromagnetic surveys involve a towed electromagnetic source and a series of seabed
receivers that measure induced electrical and magnetic fields. The measured information can be
used to interpret electrical profiles in the subsurface that potentially will be influenced by resistive
CO2 These can be used to determine subsurface electrical profiles that may be influenced by the
presence of highly resistive CO2 (IEAGHG, 2013).
Seabottom gas sampling
By sampling gas from the seabottom before injection of CO2 in a storage reservoir, potential shallow
migration pathways can be detected during site characterization. This also helps to establish
baseline variations. Collected samples of gas will experience routine geochemical analysis, such as
gas composition and stable isotopic analysis (Pearce, 2004; IEAGHG, 2013). Dependent on the
natural baseline variation this monitoring technique is suitable to detect CO2 from intermediate
leakage rates (100kg/day) (IEAGHG, 2013).
Seawater geochemistry
To know if any CO2 is leaking in the seawater, it is necessary to know the baseline variations of the
seawater. Typically, four parameters can be measured to obtain a complete picture of the CO2 in the
water-system; total dissolved inorganic carbon, total alkalinity (a form of mass-conservation
relationship for hydrogen ion), fugacity of CO2 in equilibrium with sea water (a measure of the partial
pressure of CO2), and the total of hydrogen ions (which is controlled by sulphate concentration)
(DOE, 1994; IEAGHG, 2013). Measurements of pH, temperature and salinity are also standard in the
monitoring of the seawater chemistry (IEAGHG, 2013). To make this technique more effective, it has
to be combined with measurements that can locate where the leak comes from in order to focus the
geochemical measurements around the affected area. For precise quantification of a leak, a good set
of natural background concentrations is a requisite (IEAGHG, 2012).
Sidescan sonar
Sidescan sonar comprises a towed echo sounding system which is capable of making a very accurate
image of the seabed. If this technique is used in time-lapse mode it can detect very small changes in
the topography of the seabed that could occur as a consequence of CO2 leakage to the seabed
(IEAGHG, 2013).
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Appendix 5
FEP Monitoring Technique
631 Alteration of borehole completion No Match: well integrity
631 Alteration of borehole completion No Match: isto ko 630?!
109 Blow-out No Match: pressure
223 Clay shrinkage No Match: water saturation
223 Clay shrinkage No Match: salinaty
223 Clay shrinkage No Match: CO2 phase? Ask more
224 Clay swelling No Match: water saturation
FEP has matches with
other parameters
267 Dehydratation No Match: water saturation
FEP has matches with
other parameters
629 Dessication of clays No Match: water saturation
629 Dessication of clays No Match: porosity increase
446 Drilling activities (human intrusion) No Match: seismicity
FEP has matches with
other parameters
149 Erosion of casing No Match: cement chemical
FEP has matches with
other parameters
320
Fault valve mechanism and episodic phase
transform No Match: temperature
FEP has matches with
other parameters
320
Fault valve mechanism and episodic phase
transform No Match: INSAR data
FEP has matches with
other parameters
153 Fluid density contrast No Match: variation in rock fluid density
153 Fluid density contrast No Match: check Geert
FEP has matches with
other parameters
242 Formation enhancement (fracing, acid jobs) No Match: permeability change
FEP has matches with
other parameters
Induced fracture opening No Match: pressure
In-situ pore pressure change No Match: pore pressure
82 Instantaneous material failure No Match: pressure
Leakage at sideseal No Match: seal integrity
330 Mineral precipitation and dissolution No Match: water chemistry
330 Mineral precipitation and dissolution No Match: permeability change
330 Mineral precipitation and dissolution No Match: displacement of pore gas?!
270 Mud invasion No Match: flow rates?? Not relevant
332 Pressurization of the reservoir No Match: pressure
221 Steel expansion/contraction No Match: well integrity
FEP has matches with
other parameters
234 Well interference No Match: pressure
Migration of CO2 or brine along injector Not linked to parameter
Migration of CO2 or brine via matrix pathways Not linked to parameter
CO2 release into the atmosphere Not linked to parameter
ground water contamination Not linked to parameter
surface soil contamination Not linked to parameter
primary well barrier failure Not linked to parameter
83