Are There Links Between Earthquakes and Oil & Gas Activity in Oklahoma?

Are There Links Between Earthquakes and Oil & Gas Activity in Oklahoma? Randy Keller, Director Austin Holland, Research Seismologist Oklahoma Geological Survey Collaborators: Kyle Murray, Ken Luza, and many students

Increased Earthquake Activity in Oklahoma What we know and what we don't know Randy Keller, Director Austin Holland, Research Seismologist Oklahoma Geological Survey Collaborators: Kyle Murray, Ken Luza, and many students

Are There Links Between Earthquakes and Oil & Gas Activity in Oklahoma? In Some Cases Collaborators: Kyle Murray, Ken Luza, and many students

Earthquake Triggering Natural Causes Dynamically by the passage of seismic waves Remote Triggering Statically by local stress changes from previous earthquakes Small amounts of stress change have been shown to trigger earthquakes as little as 2-7 psi Natural fluid movement May be the cause of many aftershocks Hydrologic loads-some correlations with rainfall Anthropogenic Reservoir Impoundment Mining and Oil Production (Mass Removal) Fluid Injection Geothermal Production & Thermal Contraction

Earthquake Triggering How? Increase in shear stress Mass changes Permeability barriers Thermal changes Increase in pore pressure Fluid injected under pressure Fluid injected under little or no pressure can generate a hydraulic head (100 m head ~1 MPa or 145 psi) General Observations Most of the Earth s crust is near failure so the stress released is natural Magnitudes may correlate with total injected volume over time Earthquakes may start close to a well and migrate outward Earthquakes may show a temporal correlation to injection

Oklahoma Earthquakes 1882-2008 Oklahoma has long been known to be Earthquake Country

Seismicity of the US, 1977-1997

Meers Fault NW S E

An aerial view of the scarp

Mapped Faults in Oklahoma

A perspective view

Perspective View of Oklahoma s Subsurface Structure

~1500ft

What about hydrologic fracturing?

Seismographs Used to Locate OK Events OGS Network is 35 stations

Earthquakes 1882-2008 126 years of seismicity 86 earthquakes magnitude >=3.0 13 earthquakes magnitude >=4.0

Earthquakes 1882-2013 1882-2008 - 126 years of seismicity 86 earthquakes magnitude >=3.0 13 earthquakes magnitude >=4.0 Last 4 years of seismicity 278 earthquakes magnitude >=3.0 12 earthquakes magnitude >=4.0

Most Oklahoma Faults Appear to be Near Critical Stress Levels Oklahoma Earthquakes 2009 through 2014 Greatest increase in earthquakes is occurring over about 15,000 sq. miles

Dramatic Increase in Oklahoma Earthquakes 2014 08-15-2014

1882-2008 126 years of seismicity 86 earthquakes magnitude >=3.0 13 earthquakes magnitude >=4.0 2009-2013 4 years of seismicity 278 earthquakes magnitude >=3.0 12 earthquakes magnitude >=4.0 2014 231 days of seismicity 309 earthquakes magnitude >=3.0 18 earthquakes magnitude >=4.0 Updated 08/19/2014 UTC 13:36:45

Oklahoma s Increase in Earthquakes Earthquake rates per year Magnitude 4 or Greater Earthquakes Magnitude 3 or Greater Earthquakes 0.1 3 Years 1882-2008 Years 2009-2013 Year 2014 427 1.6 20 42 67 40 109 Years 1980-2008 Year 2009 Year 2010 Year 2011 Year 2012 24 Year 2013 Updated Oct. 20, 2014 Year 2014

An increase like this has not been observed in modern seismology in an intra-plate setting. The Gutenberg-Richter Law: log 10 N(x) = a bx It states that, for every 10 magnitude 3.0 earthquakes within a region, we can expect 1 magnitude 4.0 earthquake.

Simple Probabilities for Earthquakes From the Gutenberg-Richter Scaling Law

An example of the result of high Q

Earthquakes 1882-2013 2012-Present Mississippi Lime Play 1882-2008 - 126 years of seismicity 86 earthquakes magnitude >=3.0 13 earthquakes magnitude >=4.0 2009-Present Jones Swarm 2010-2011 Woodford Shale Play 2011-2012 M5.6 Prague & Hunton Dewatering

Seismicity Rates Mississippi Lime Play Large amounts of produced water ~10% oil cut Best correlation to change in injection volumes and seismicity rates Increase in 2009 Southern extent Increase in 2012-2013 Heart of the play, northern Oklahoma Cumulative Number of Earthquakes

Disposal wells in Oklahoma It is very hard to find an earthquake that is not near an injection well. Is the well active? What is the injected volume? What is the pressure?

Which zones are used for EOR and SWD injection? KS UIC data from KGS (2013) Well Database OK UIC data from Lord (2012) UIC Database Murray and Irwinsky, 2013-in review

Well Completions 2010-6/2012 ~5000 wells completed Compilation from the OCC ~50 wells bad spatial referencing

~1500ft

Earthquakes triggered by hydraulic fracturing Several earthquakes felt by one local resident Largest earthquake M 2.9 11 earthquakes >= M 2.0 Holland, Bull. Seismol. Soc. Amer. (2013)

Identification is easy when you have more information; took ~6 months to get injection data Holland, Bull. Seismol. Soc. Amer. (2013)

What are pressures versus depth in the Arbuckle Group? KS & OK Arbuckle pressure data from IHS database (Murray et al., 2014, in preparation)

Pressure distribution in the Arbuckle Group? OK Arbuckle pressure data from IHS database

Interagency Cooperation OCC UIC Program Data OGS Optimally Oriented Faults New Permit & Existing Permits Fault Maps Earthquake Information Fault Database Project Earthquake Monitoring and Reporting Injection and Operational Data Additional Studies

Industry Contributing to Enhanced Fault Database

3D geologic and geophysical model development 100,000 s of Wells in central Oklahoma Geological and geophysical logs combined to build 3D models Incorporated into 3D seismic velocity models Geospatially referenced surfaces Hunton (orange) and basement (brown). Geologic units are assigned physical properties such as from well logs with spatially varying properties such as permeability, density, porosity, and velocity.

Current Mitigation Steps Oklahoma Corporation Commission is the regulator of UIC Class II wells, and have implemented different mitigation strategies New rules regarding reporting of injection volumes and pressures in the Arbuckle Permit modifications; i.e. Traffic Light System Enhanced reporting requirements in OCC areas of interest, currently 10 km around ML 4+ earthquakes New permits are checked against fault maps and background seismicity

Industry Contributing to Enhanced Fault Database

General Comments No dramatic increase in injected volumes in significant areas are associated with corresponding earthquakes Except for the Mississippi Lime Play & perhaps the Woodford Shale Play Injected volumes have been decreasing in the Hunton Dewatering Play Given the rate of known cases of induced seismicity it is unlikely that the entire earthquake rate increase in Oklahoma is due to fluid injection from oil and gas More than 10,000 UIC Class II wells in Oklahoma More than 80% of Oklahoma is within 15 km of a UIC Class II well (It would be hard not to have spatial correlations) Either there is a natural contribution to some of the rate increase, or there is a large-scale tipping point that has been reached Developing a set of best practices http://www.gwpc.org/sites/default/files/event-sessions/holland_austin.pdf

Summary of Induced Seismicity Issues If not addressed properly, Induced Seismicity could unduly delay and cancel important energy applications (already has) Oil and Gas, CCS, Geothermal Has come to the attention of Congress (NAS Study) Induced seismicity issues are not new (over 100 yrs). Generally, causes are known and have been (or can be) mitigated Induced Seismicity risk cannot be calculated in the same manner as natural seismicity Must calculate risk as an adaptive process Must have a mitigation plan Risk will change as net volume increases Best practices must be developed for all stakeholders needs Geothermal best practices in use and being followed by the industry Modified from points raised by: Ernie Majer LBL

Conclusions & Further Work We do see some induced, or triggered, earthquakes in Oklahoma Like the rest of the country, induced earthquakes are probably rare We may be seeing a combination of natural earthquake rate changes and induced seismicity Adding more staff and seismic stations to do more science and better understand our earthquakes RPSEA (DoE) Grant has recently been funded and work is well underway

Some Considerations Concerning the Formulation of Best Practices It is for regulators or operators to decide what level of risk is acceptable? Within an established risk level, non-specific terms such as frequent and near can be more precisely defined. The recommendations would be general and based on current understanding of the causes of induced seismicity.

Sources for some ideas about best practices Minimizing and managing potential impacts of induced-seismicity from class II disposal wells: practical approaches, EPA Draft released through FOIA Committee on Induced Potential in Energy Technologies, 2012. Induced Seismicity Potential in Energy Technologies, National Academy of Sciences. Nicholson, C. & Wesson, R.L., 1990. Earthquake Hazard Associated With Deep Well Injection -- A Report the the U.S. Environmental Protection Agency, U.S. Geological Survey Bulletin, 1951, 74. Zoback, M.D., 2012. Managing the Seismic Risk Posed by Wastewater Disposal, Earth Magazine, April 38-43. Shemeta, J.E., Eide, E.A., Hitzman, M.W., Clarke, D.D., Detournay, E., Dietrich, J.H., Dillon, D.K., Green, S.J., Habiger, R.M., McGuire, R.K., Mitchell, J.K., Smith, J.L. & Gibbs, C.R., 2012. The potential for induced seismicity in energy technologies, The Leading Edge, December, 1438-1444. Talwani, P., Chen, L. & Ghalaut, K., 2007. Seismogenic permeability, k s, J. Geophys. Res., 112, 1-18. Davis, S.D. & Frohlich, C., 1993. Did (or Will) Fluid Injection Cause Earthquakes? Criteria for a Rational Assessment, Seismol. Res. Lett., 64, 207-224. Majer, E.L., Baria, R., Stark, M., Oates, S., Bommer, J., Smith, B. & Asanuma, H., 2007. Induced siemicity associated with Enhanced Geothermal Systems, Geothermics, 36, 185-222. Shapiro, S.A., Dinske, C. & Kummerow, J., 2007. Probability of a given-magnitude earthquake induced by a fluid injection, Geophys. Res. Lett., 34, 1-5. Suckale, J., 2009. Induced Seismicity in Hydrocarbon Fields, Advances in Geophysics, 51, 55-106 Case examples from: Paradox Valley, CO; Rocky Mountain Arsenal, CO; Rangely, CO; Carthage Cotton Valley Gas Field, TX; Fenton Hill, NM; KTB Deep Drilling Site; Basel; Cooper Basin; Soultz-sous-Foreˆts Hot Dry Rock facility, and many others

Our Workshop Brought Out Several Tricky Questions About Faults Where are the faults located? What does near really mean? What does large mean, and how do we measure it? What is the depth extent of faults? Is anyone willing to share their information that would help us address these questions?

Identified risk factors for triggered seismicity Proximity to known faults, large faults poses a greater risk for consequences Faults oriented favorably within the regional stress field Historical background seismicity indicates that there are faults at or near critical stress and favorably oriented within the regional stress field These are environments which would be considered higher risk environments for fluid injection Earthquake triggering occurs naturally in areas without fluid injection (van der Elst & Brodsky 2010) Earthquakes can be dynamically triggered by the passage of surface waves from distant large earthquakes or remotely triggered Indicates that small stress or pore pressure changes have an impact on fault rupture (van der Elst et al., 2013, Science)

Proximity to faults 1. Fluid injection near known faults should be avoided Faults and asperities (fault roughness) within faults act as stress concentrators, fault branches also act as stress concentrators Faults can act as both permeability barriers as well as high permeability zones (highly dependent on fault properties) Highly permeable zones can channel the diffusion of pore pressure significantly large distances Fluid pressure may build near an injection well (does not require injection under pressure, hydraulic head) 2. Fluid injection wells should be sited further from faults that are favorably oriented within either the regional or local stress field Zoback (April 2012) Earth magazine, and many others

Optimal Fault Orientations for Oklahoma Approximate Regional Stress Field

Monitoring of injection and formation pressure 3. Injection pressure and volume should be monitored and recorded frequently during the operation of the well. Monthly injection information will likely not accurately represent the injection history of the well Inadequate for detailed reservoir modeling 4. Formation pressure should be as often as practical. However, at a minimum, regular shut in, pressure fall-off tests should be conducted to measure formation pressure. This monitoring may help identify when and how fluid injection is altering properties within the formation Has the potential to improve performance of an injection well May help to identify or discount potential induced seismicity

Injection into or near basement 5. Injection into crystalline basement should be avoided. Permeability in crystalline basement is generally low Fluid and pore pressure may concentrate in networks of existing natural fractures and faults where permeability is the greatest Permeability barriers or spatial inhomogeneity can lead to increased stress

Permeability Barriers Can Increase Stress Roeloffs and Denlinger (SSA Mtg 2013) Permeability Barrier in the injected formation

Balance of fluid volumes 6. In operations that involve both production and injection of fluids in nearby wells, volumes should ideally be balanced to avoid any major increase in net fluid volume. Recommended by the NAS Induced Seismicity Potential in Energy Technologies If net fluid volume injected is related to magnitude then this is one method of mitigation Does not address majority of disposal wells This may not be true in geothermal fields Recent work at the Salton Sea, Brodsky and Lajoie (2013) Science

Additional Monitoring in Higher Risk Environments 7. The siting of new injection wells in higher risk environments should be approached with caution. More frequent monitoring of injected volume, injection pressure, and formation pressure is recommended, as well as additional earthquake monitoring. 8. In cases where fluid injection is occurring in higher risk environments, additional geotechnical information may help to provide further constraints on injection limits. Mini-fracs and image logs can provide the orientation and magnitude of stresses as well as the orientation of natural fractures and can help to address the potential for triggered seismicity.

Response to Potential Induced Seismicity 9. The operator should have a plan in place to recognize and respond in a timely manner to unexpected seismicity or changes in injection pressure or volume. Modifications to injection parameters Additional seismic monitoring Prior to operations, identify what levels of seismicity will generate actions within a response plan Zoback (April 2012) Earth magazine

LOVE COUNTY 2013 STATUS UPDATE Austin Holland, Research Seismologist Oklahoma Geological Survey (10-18-2013)

The Love Co. example where the operator is on a yellow light status Earthquake swarms have occurred in the past Poorly recorded because they were shallow so the regional network did not do well detecting and locating them Portable deployments were attempted but unsuccessful due to shallow depths Earthquakes 1882-8/29/2013 Personal Comm. Ken Luza (OGS)

Some Additional Questions Are there additional risk factors not identified here? What should be considered near a fault? Is there additional geotechnical information that may be useful in high risk environments? Extent of seismic monitoring? Is the database available to the public adequate? Capability to detect small earthquakes? Establish baseline prior to start of injection? Impact of local geology? What about companies that only do waste water disposal?

In spite of recent controversial high profile publications and statements by some earthquake seismologists, there is a lot agreement. The earthquake seismic community broadly agrees that earthquake triggering by injection wells is a rare occurrence. However, there are a few well-documented examples. This community also agrees that the probability of a damaging earthquake being triggered by hydraulic fracturing is extremely low. What can we, should we do? Ignore the issue Wait until something really bad happens Take some measured steps such as considering some best practices concerning fluid injection

Induced Seismicity from Fluid Injection Increased pore pressure from fluid injection effectively reduces friction on fault Or in Mohr-Coulomb space moves the circle towards failure Increase deviatoric stress o σ 1 -σ 3 σ n Failure σ i Add Pore Pressure - p

Pressure Diffuses Within the Earth Pressure increase is not due to actual fluid flow Can be much more rapid Because water is fairly incompressible it is similar to an elastic response although slower Diffusivity constant is T = transmissivity S = storativity Proportional to permeability Pressure Talwani increases et al. (2007) over J. Geophys time Res.

Maximum Seismic Moment (related to magnitude) vs. Injected Volume RAT=Raton Basin RMA=Rocky Mtn Arsenal. YOH=Youngstown OH PBN=Paradox Valley CO GAK=Guy AK BAS=Basel Switzerland GAR=Garvin County OK BUK=Bowland Shale UK KTB=Eastern Bavaria Germany Injection Duration Courtesy of Art McGarr (USGS)

Earthquakes may start close to the well and migrate away Pressure diffusion is often modeled using this observation Most of the earthquakes still tend to occur very near the injection interval Paradox Valley, Ake et al. (2005)

Stress Changes from mass or volume changes Fluid extraction can change the stress field and style of faulting Stress changes and style of faulting modeled for extraction from a reservoir Stress changes can also occur due mass loading reservoir loading Segall (1989)

Are all faults created equal? Large faults may lead to large earthquakes Energy and magnitude are proportional to fault size Faults of all sizes show great complexity at all subsequent scales This makes identifying all optimally oriented faults problematic Scholz (1990)

Optimal Fault Orientations Sibson (1990) Bull. Seismol. Soc. Am. Red lines indicate the range of possible orientations aligned within the regional stress field. Fault slip outside of this region is unlikely but possible with very dramatic increases in pore pressure.

Active Fault Orientations in Oklahoma Holland (2013) Seismol. Res. Let.

Stress Orientations from Focal Mechanisms Oklahoma is generally experiencing eastwest compression in a strike-slip regime Most notable exception are parts of the Jones swarm which show NE-SW compressive strikeslip regime, with faults oriented N-S

UIC Wells - 2011 It is very hard to find an earthquake that is not near an injection well. Is the well active? What is the injected volume? What is the pressure? KS Well Locations from: KGS (2013) Well Database OK Well Locations from: Lord (2012) UIC Database