caitlin augustin structural geology
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Evaluation of the usefulness of hydraulic fracturing sites as an
analogue for geologic carbon sequestration sites
Caitlin AugustinStructural Geology
Introduction
Hydraulic fracturing for natural gas retrieval and deep geologic injection of carbon dioxide share several characteristics (NETL, 2010)
This presentation seeks to examine the similarities between the two injection fields and to analyze hydraulic fracturing sites as a potential analogue for geologic behavior and environmental risk assessment for geologic carbon sequestration.
Outline
Background◦ Process◦ General Structural Geology
Features◦ Overview in the United
States◦ Example sites
Methodology and Hypothesis
Analysis◦ Mineralization◦ Deformation◦ contamination
Conclusion and further work
Process
Hydraulic fracturing Carbon sequestration
Procedure◦ Injection of fracturing fluid into
the wellbore at a rate sufficient to increase the pressure down hole to a value in excess of the fracture gradient of the formation rock.
Depth◦ 8000 ft (2666 m)
Formations◦ Low permeability rocks◦ Typically shale
Procedure◦ Injection of supercritical
carbon dioxide at a rate maintaining reservoir pressure
Depth◦ 2400 ft (8000 m)
Formations◦ High permeability
reservoir capped with low permeability shale
General structural geology of injection sites
Systematic and Nonsystematic Natural Fractures (Joints)
Description◦ alteration along joints
indicating fluid movement.◦ Systematic joints are a group
of parallel to sub-parallel joints evenly spaced to one another
◦ Nonsystematic joints are irregularly oriented joints with no obvious spatial relationship
Site locations◦ Occurs in the Marcellus shale
Teapot dome CCS field◦ (Hancock, 1986)
General structural geology of injection sites
Fissility
Description◦ the property of rocks to split
along planes of weakness into thin sheets.
◦ Caused by the preferred orientation of clay minerals with their planes orientated parallel to bedding due to compaction, deformation, or new mineral growth
Site locations◦ Shale caprocks◦ (Arthur, 2008)
General structural geology of injection sites
Folds
Description◦ result of compressional
stress acting on rocks that behave in a ductile manner
Site locations◦ Weyburn injection site,
Marcellus Shale◦ (Daniels, 2006)
Active sites
Hydraulic fracturing Carbon sequestration
Approximately 400 active sites in the United States
Approximately 20 active sites in the United States
Evaluation Sites
Hydraulic FracturingMarcellus Shale, Pennsylvania, United States
Carbon SequestrationCarbonate Reservoir, Weyburn, Canada
Potential outcomes
Hydraulic fracturing Carbon sequestration
1. Cracks in the impermeable layer to release trapped natural gas
2. Surface fracturing3. Subsidence
1.Stable sequestration2.Surface Fracturing3.Viscous fingering
Hypothesis
Given the geologic similarity between the two injection fields the reactions at natural gas hydraulic fracturing sites should be a good analogue for assessment and management of carbon sequestration sites.
We anticipate similar deformation and leakage events to occur between sites.
Methodology
Comparison of injection sites based on the occurrence and treatment of ◦Mineralization◦Subsurface deformation◦Subsurface contamination◦Surface deformation◦Surface contamination
Mineralization: description
Mineralization is the reaction of a compound with existing minerals to form new minerals such as siderite and dawsonite
Mineralization
Hydraulic fracturing Carbon sequestration
Mineralization of precious metals
Pyrite unconformities (Phillips,1972) suggests
it commonly occurs with natural fracturing, but (Mcafferty,1999) suggests it is rare in retrieval sites
Mineralization occurs in carbonate reservoirs on a geologic timescale (Benson,2001)
Reactions occur more quickly in mafic rock formations (Matter and Kelemen,2009)
Subsurface deformation: description
Elastic Properties: ductile/brittleForces: compression/tension Geomechanical changes: heating/coolingIncreased tectonic stress field
Subsurface deformation
Hydraulic fracturing Carbon sequestration
Compression around borehole
effects on the prevailing tectonic stress field
Subsurface fracturing (Van Wees,2003) shows
that this deformation occurs in over 90% of injection sites
Microfracturescompression around
injection wellSediment compressionvein formation (Lu, 2001) One of
these deformations occurs in over 50% of sites
Subsurface contamination: description
Fluid migration and sediment mobilization that encroaches negatively on subsurface fluid or mineral reservoirs
Subsurface contamination
Hydraulic fracturing Carbon sequestration
Groundwater contamination
(EPA, 2009) occurrence prompted change in law
Coal sterilization(Wolf, 2000)
intentional sterilization in unmineable coal beds
Less than 1% pollute groundwater
Surface deformation: description
Reaction of subsurface deformation visible on the surface such as faulting, subsidence and uplift
Surface deformation
Hydraulic fracturing Carbon sequestration
Faulting and surface fracturing
Subsidence (Van Wees, 2009)
showed that this is directly linked to subsurface deformation and occurs at a similar pace
Faulting and surface fracturing
Uplift(CSA, 2010) surface
deformation occurs but requires monitoring standards
Surface contamination: description
The distribution of fluid and gaseous contaminants through currents
Surface contamination
Hydraulic fracturing Carbon sequestration
Surface water contamination
(Lustgarten,2009) documented 1500 cases of water contamination between 2003 and 2008
Carbon dioxide plumes
(DOE, 2010) reports at least two of the 17 funded injection sites have surface gas leakages
Key observations
The subsurface deformation, surface deformation, and surface contamination events occurring from hydraulic fracturing and carbon sequestration are the most similar and occur most often◦Recorded subsurface deformation occurs at
similar depths (approximately .5-1 mile below)◦Rehabilitation and education of deformation
and contamination can occur in similar ways
Study utility
The use of hydraulic fracturing sites as an analogue provides industry scale injections for carbon sequestration scientists to study for deformation and rehabilitation characteristics◦It shows key assumptions, such as groundwater
contamination are dissimilar between the two injection sites
Tool for disaster management protocols
Policy Regulations
Both hydraulic fracturing and carbon sequestration are regulated by the EPA◦Hydraulic fracturing ruled by 2009 FRAC Act◦Carbon sequestration by the 2010 UIC Law
Hydraulic fracturing has stricter regulation regarding contamination and rehabilitation
No industry standards exist for carbon sequestration
Recommendations and further study
Site by site comparisonPublic health studyMonitoring and verification comparison
and developmentAdapt computer models between injection
sites
Sources
NETL 2010 Hancock 1986 Arthur 2008Daniels 2006 Philips 1972McCafferty 1999 Benson 2001Matter and Kelemen 2009 Lu 2001Wolf 2000 Lustgerten 2009
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