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 fracturingCarbon 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 fracturingCarbon 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 fracturingCarbon 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 fracturingCarbon 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 fracturingCarbon 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