Probabilistic Seismic Risk Assessment for CCS

Transcription

1 Probabilistic Seismic Risk Assessment for CCS Induced Seismicity Working Group National Risk Assessment Partnership

2 NRAP s Induced Seismicity Working Group Lawrence Berkeley National Laboratory C. Bachmann T. Daley B. Foxall L. Hutchings T. Kneafsey J. Rutqvist H. Murakami-Wainwright National Energy Technology Laboratory D. Crandall E. Lindner H. Siriwardane (WVU) Lawrence Livermore National Laboratory S. Carroll L. Chiaramonte S. Johnson W. Trainor-Guitton J. Wagoner J. White Pacific Northwest National Laboratory Z. Hou C. Murray Los Alamos National Laboratory C. Bradley B. Carey D. Coblentz R. Lee External Collaborators J. Savy, Savy Risk Consulting J. Dieterich, UC Riverside Contact: Joshua White, jawhite@llnl.gov LLNL- PRES Por1ons of this work were performed under the auspices of the U.S. Department of Energy by Lawrence Livermore Na1onal Laboratory under Contract DE- AC52-07NA27344.

3 Typical scenario of concern Injection creates relatively small CO 2 plume, surrounded by larger plume of pressurized brine. Pressure increase along a welloriented fault could trigger seismic (or aseismic) slip. The fault is sufficiently large to produce concerning earthquakes. Fault is sufficiently small that it may have been unobserved or poorly characterized during site selection. Overall risk is controlled by several components in a complex system.

4 Typical scenario of concern * Figure not to scale Overall risk is controlled by several components in a complex system.

5 Four key risks associated with induced seismicity 1 Damage Risk Induced ground motions can damage nearby infrastructure 2 Nuisance Risk Induced ground motions can annoy nearby populations 3 Brine Leakage Risk Slip-enhanced leakage pathways can allow brine to contaminate protected groundwater. 4 CO 2 Leakage Risk Slip-enhanced leakage pathways can allow CO 2 to contaminate protected groundwater. Helpful to consider each separately. Though related, they have different physics, 1mescales, likelihoods, impacts, poten1al mi1ga1on, etc.

6 A series of conditions must line up for an impact to occur: start Will the pressure plume encounter a sufficiently large fault? Is the fault capable of generating significant seismicity, based on its dimensions, orientation, tectonic loading, and frictional properties? Significant seismicity could occur. Could resulting ground motion exceed building code standards? Infrastructure could be damaged. Could resulting ground motion exceed nuissance standards? Local population could be scared and/or annoyed. Does the fault fully or partially penetrate the caprock seal(s)?

7 A series of conditions must line up for an impact to occur: start Will the pressure plume encounter a sufficiently large fault? Yes. Is the fault capable of generating significant seismicity, based on its dimensions, orientation, tectonic loading, and frictional properties? Significant seismicity could occur. Challenging to assess pre- injec1on (irreducible uncertain1es). Could resulting ground motion exceed building code standards? Infrastructure could be damaged. Offshore? Remote? Tokyo, San Francisco? Basel? Could resulting ground motion exceed nuissance standards? Local population could be scared and/or annoyed. Does the fault fully or partially penetrate the caprock seal(s)? Natural tendency to focus on early part of the chain, when later safeguards may exist (or be put in place).

8 Infrastructure could be damaged. Could resulting ground motion exceed nuissance standards? Local population could be scared and/or annoyed. Does the fault fully or partially penetrate the caprock seal(s)? Can new leakage pathways be created along the fault, based on slip distance, slip area, and fault lithology? Is the duration and magnitude of pressure drive sufficient to allow brine leakage to protected drinking water? Brine contamination could occur. Does mobile CO 2 ever reach the fault? Is the duration and magnitude of pressure and buoyancy drive sufficient to allow CO 2 leakage to protected drinking water? CO 2 contamination could occur. Should consider induced risks in tandem with background risks. Ac1ve interven1on and mi1ga1on should also be included.

9 High costs and large uncertainties suggest a phased approach to seismicity management Phase Characteriza-on & Monitoring Modelling Risk Assessment Site- screening Regional stress es1mates Fault density es1mates Back- of- the- envelope Red- flags Atlas Pre- injec1on 3D seismic XLOTs FMI Limited microseismic Injec1on & PISC 4D seismic Full microseismic array Simple models Qualita1ve Assessments PSHA Sophis1cated models Traffic- light PSRA - - Cost/benefit of addi1onal methods assessed based on evolving project condi1ons. - - Baselines are important. - - Timely processing and interpreta1on of data are important.

10 Probabilistic Seismic Risk Assessment PSRA is commonly used for dealing with natural seismic hazards. Framework is well-suited to dealing with induced seismicity, but must be modified to address differences between natural and induced events. Three key ingredients to a PSRA: Earthquake frequency/magnitude relationship. very challenging Ground motion hazard. mostly standard (some issues) Fragility curves. mostly standard (some issues) For CCS, framework also needs to be extended to capture leakage risks.

11 SIMRISK Framework SIMRISK is a framework for PSRA, specifically adapted to induced seismicity. Allows for flexible input, so that component modules may be easily swapped. Currently testing an earthquake simulation module based on RSQSim (Dieterich 1995; Richard- Dinger & Dieterich 2012) Validating against waste-water injection analogs.

12 Earthquake Frequency Modeled data for a synthetic site in a seismically-active region [Foxall et al. 2012]. Background: y Injec1on: y Post- injec1on: y Zoom of injec1on period

13 Ground Motion Intensity Background (0-200 y) Injec1ng ( y) For reference 2 cm/s/s is barely perceptible by most people. 20 cm/s/s will cause light shaking but no damage. 200 cm/s/s can cause moderate to severe building damage.

14 Fragility Curves Fragility curves quantity likelihood of damage to a structure given a certain level of shaking. Same idea can be applied to a nearby population via nuisance curves [Majer et al. 2012]

15 NRAP is pursuing integrated, system-level models of damage, nuisance, and leakage risk. Ground'mo)on' Basin2wide(fault( 6b( characteriza/on( Fault'leakage' 2,5( Earthquake(((( simula/on * ( 6a( Reservoir(flow( simula/on( pressure( fault(slip( pressure( satura/on( Δk( Fault(slip2 permeability(model( 7d( Δk( Slip2related(fault( permeability( 7a2c( evolu/on(model( 4( Ground(mo/on( calcula/on( Regional,(in#situ( stress;(background( 6c( seismicity( Fault(leakage( simula/on( 1 Damage(&(nuisance( risk( 8( Leakage(probability( Characteriza/on/research(studies( Simula/on/computa/on( Result( Downstream(calcula/on( 1 Task/subtask( *Empirical((Task(3)(alterna/ve( Aquifer(response( simula/on( Groundwater(impact( risk( Key science gap: permeability behavior of slipping faults.

16 Conclusions 1. There will always be irreducible uncertainties associated with the seismic behavior of a field. That said, it is possible to choose sites that are robust with respect to seismic behavior. 2. There are four key risks associated with induced seismicity, and each has nuances that should be considered separately. 3. Seismicity deserves real attention when developing the characterization, monitoring, mitigation plans. A phased approach, combined with good contingency plans, can reduce cost while still addressing risk. 4. Probabilistic seismic risk assessment provides a rigorous, quantitative framework. Significant progress has been made adapting it to induced seismicity, but some important science gaps still exist.