1. Evaluation of the usefulness of hydraulic fracturing sites as an analogue for geologic carbon sequestration sites Caitlin Augustin Structural Geology

2. 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.

3. 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

4. Process Hydraulic fracturingCarbon 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

5. 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)

6. 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)

7. 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)

8. Active sites Hydraulic fracturingCarbon sequestration Approximately 400 active sites in the United States Approximately 20 active sites in the United States

9. Evaluation Sites Hydraulic Fracturing Marcellus Shale, Pennsylvania, United States Carbon Sequestration Carbonate Reservoir, Weyburn, Canada

10. Potential outcomes Hydraulic fracturingCarbon sequestration 1. Cracks in the impermeable layer to release trapped natural gas 2. Surface fracturing 3. Subsidence 1. Stable sequestration 2. Surface Fracturing 3. Viscous fingering

11. 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.

12. Methodology Comparison of injection sites based on the occurrence and treatment of ◦Mineralization ◦Subsurface deformation ◦Subsurface contamination ◦Surface deformation ◦Surface contamination

13. Mineralization: description Mineralization is the reaction of a compound with existing minerals to form new minerals such as siderite and dawsonite

14. 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)

15. Subsurface deformation: description Elastic Properties: ductile/brittle Forces: compression/tension Geomechanical changes: heating/cooling Increased tectonic stress field

16. 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 Microfractures compression around injection well Sediment compression vein formation (Lu, 2001) One of these deformations occurs in over 50% of sites

17. Subsurface contamination: description Fluid migration and sediment mobilization that encroaches negatively on subsurface fluid or mineral reservoirs

18. 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

19. Surface deformation: description Reaction of subsurface deformation visible on the surface such as faulting, subsidence and uplift

20. 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

21. Surface contamination: description The distribution of fluid and gaseous contaminants through currents

22. 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

23. 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

24. 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

25. 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

26. Recommendations and further study Site by site comparison Public health study Monitoring and verification comparison and development Adapt computer models between injection sites

27. Sources NETL 2010 Hancock 1986 Arthur 2008 Daniels 2006 Philips 1972 McCafferty 1999 Benson 2001 Matter and Kelemen 2009 Lu 2001 Wolf 2000 Lustgerten 2009