Pressure Management Induced Seismicity

Transcription

1 Pressure Management Induced Seismicity Jonny Rutqvist Lawrence Berkeley National Laboratory Berkeley, California Workshop on Geologic Capture and Sequestration of Carbon, Stanford, Nov 28, 2017 National Academies Study on Carbon Dioxide Removal and Reliable Sequestration

2 OUTLINE Geomechanics of CO2 Sequestration Injection-induced fault activation and seismicity (modeling) In Salah deep fracture zone response (modeling) Some remarks Large-scale pressure change and seismicity (observations) Some more remarks

3 Geomechanics of CO 2 Storage in Deep Sedimentary Formations [Rutqvist (2012) Int J Geotechnical and Geological Engineering]

4 Potential Fault Reactivation and Notable Seismic Events An important issue from safety, storage security, and public acceptance perspectives. Release of stored energy triggered by the injection. Not just limited to seismically active areas, but could also occur within the seismically quiet intraplate crust (Zoback and Gorelick., 2012). Undetected minor faults relevant [Rutqvist (2012) Int J Geotechnical and Geological Engineering]

5 Modeling Fault Activation and Seismicity TOUGH-FLAC Simulator (Rutqvist, 2011) FLAC3D Geomechanical Simulator Fault Discretization Strain-softening Fault TOUGH Multiphase Flow Simulator Typical Model Domain Strain-softening Coulomb failure along the fault Slip-weakening fault behavior Seismic magnitude (seismic moment M 0 = Ad) Fault permeability change

6 Modeling Fault Activation and Seismicity Integrated analysis from cause to consequence: Injection Fault activation Seismic wave Ground vibration Effects on buildings/humans Rutqvist et al 2014 (Int. J Greenhouse Gas Control)

7 Simulated CO2 Injection and Fault Activation Reservoir 7.5 MPa Overpressure Reactivation at about 7.5 MPa overpressure 290 m fault rupture corresponding to M w 2.5 to 3 4 cm fault slip over 0.4 seconds, peak slip 0.6 m/s (Cappa and Rutqvist, Geophysical J International, 2012)

8 Ground Surface Motion at Top of the Fault Top soil PGA 0.6g at Hz no top soil 50 m top soil 100 m top soil High frequency acceleration damped for soil (Rutqvist et al., IJGGC, 2014) PGV 30 mm/s at 6-12 Hz PGV for one jolt at a lower frequency 8

9 Building Damage and Human Perception US Bureau of Mines (USBM) ground vibration criteria for building damage and human perception Simulated ground motion frequency spectrum PGV 30 mm/s at 6-12 Hz (Rutqvist et al., Int J Greenhouse Gas Control, 2014) In this example vibrations could cause cosmetic building damage and be felt by humans

10 Comparison to Field Data on Size-Magnitude Stress Ratio TOUGH-FLAC modeling of events triggered by injection (Cappa and Rutqvist, 2011) V H H / V = 0.8, 0.7, 0.6 = 1.1, 1.7, 2.3 MPa (Rutqvist et al., 2016) Largest magnitude calculated for a fault exposed to the highest shear stress ( H = 0.6 V ) An event that might be widely felt, e.g. M W = 4, requires a km-sized rupture

11 Reactivation of a Minor Fault Small initial shear offset (i.e. <10 m) and 1 km long: undetected? When the horizontal-to-vertical stress ratio was reduced to as low as 0.65, the shear strength drops during reactivation to a value below the prevailing shear stress and the fault could thereby rupture in a self-propagating manner (Mazzoldi et al., IJGGC 2012). 11

12 Effect of Fault Properties Heterogeneous (immature) fault localized pressurization and lower magnitude events.. Homogeneous fault (mature) fault pressurize and rupture larger area leading to larger magnitude events.. (Rutqvist et al., 2016)

13 The In Salah CO 2 Storage Project, Algeria In Salah Gas JV (BP, Staoil, Sonatrach) CO 2 is reinjected into the reservoir at Krechba for long term sequestration Spain Marocco Krechba gas field Mali Algeria Libya In Salah Gas Project Niger Cretaceous Sandstones and mudstones (900 m thick) Carboniferous mudstones (950 m thick) Four gas producing wells Gas zone Carboniferous reservoir (20 m thick) Three CO 2 injection wells Water zone Plane view of Krechba Gas Field KB503 Horizontal CO2 injection wells KB502 Stress Fractures Gas-water contact at a depth of 1.8 km 5 km 3 1 KB501 Krechba Gas Field The CO 2 injected at a depth of about 1,8 to 1,9 km into a 20 m thick formation of relatively low permeability. Nearly one million tonnes CO 2 per year injected from 2004 to 2011 at 3 horizontal injection wells Bottom hole pressure limited to below the fracturing gradient maximum pressure increase of about 100 bar (160% of hydrostatic) 950 m thick caprock with multiple low permeability formations (Rutqvist, 2012)

14 In Salah Ground Surface uplift from Satellite (InSAR) Double-lobe uplift (Rutqvist et al., 2010) Rutqvist et al (2010)

15 In Salah Deep Fault or Fracture Zone Responses Vasco et al. (GRL, 2010) interpreted observed double-lobe (uplift) response to be caused by a tensile opening feature at the injection zone. u(x,t ) Tensile opening 1 Seismic contour in caprock 150 m above injection zone and surface uplift after 3 years. (Rutqvist, 2012)

16 In Salah Deep Fault or Fracture Zone Responses Rinaldi, Rutqvist (2013) TOUGH-FLAC modeling with simultaneous matching of transient uplift and injection data TOUGH-FLAC Data Modeling indicates that the fracture zone extends a few hundred meters up from the reservoir (contained within the 900 m thick caprock) 1

17 Pressure vs Seismicity at In Salah Injection pressure sufficiently high to induce deep fracture zone opening Minor faults indicated from 3D seismic (Ringrose et al., 2011) Theoretically close to critically stressed for shear reactivation (Morris et al., 2011) However, CO2 injection at In Salah did not result in any felt seismic events or substantial strike-slip shear movements (Max magnitude 1.7, (Stork et al. 2015)) Increased MEQ rate when fracturing pressure (= 155 bar) is exceeded (Oye et al., 2013) At lower injection pressure (e.g. 120 bar) the MEQ rate is much smaller MEQ rate can be controlled by pressure management Pressure management to prevent damage to caprock..

18 Some Remarks - We used numerical modelling to induce reactivation of steeply dipping faults at a high injection pressure in an unfavourable stress regime. - We simulated events of magnitudes < 4 that would not result in any structural damage, but could likely be felt and cause concern in the local community. - At In Salah, injection pressure was relatively high indicating minor faults being critically stressed for reactivation, but no felt seismic event has been reported. Major Fault Stress and strain changes beyond area of pressure change Pressure change far beyond CO 2 plume Injection well CO 2 plume Minor faults

19 Some Remarks - We used numerical modelling to induce reactivation of steeply dipping faults at a high injection pressure in an unfavourable stress regime. - We simulated events of magnitudes < 4 that would not result in any structural damage, but could likely be felt and cause concern in the local community. - At In Salah, injection pressure was relatively high indicating minor faults being critically stressed for reactivation, but no felt seismic event has been reported. - At future large-scale CO2 operations (much larger than In Salah), it is the large-scale and long-term pressure buildup, associated crustal straining, and potential undetected (minor) faults that might be of greatest concern. Major Fault Stress and strain changes beyond area of pressure change Pressure change far beyond CO 2 plume Injection well CO 2 plume Minor faults

20 Regional Pressure Response and Induced Seismicity Zhou and Birkholzer (2011) simulated 100Mt CO2 injection in Mt Simon Formation Illinoi Basin showing pressure changes could extend hundreds of kilometers Bauer et al. (2016) indicated that pressure changes < 1 MPa could have induced micro-seismicity at the Decatur Project, where injection took place in Mt. Simon on top of chrystalline basement rock Hornbach et al., (2015) indicate that small pressure changes of less than 0.2 MPa could have induced seismicity in a chrystalline basement fault near Azle, Texas. Should CO2 injection stay away from crystalline basement?

21 Injection Wells in Central/Eastern US and Seismicity Comprehensive study by Weingarten et al., (2015) indicated that: High-rate injection wells more likely associated with earthquakes. Managing injection rates may be a useful tool to minimize seismicity There are areas with a large number of wells associated with seismicity whereas there are large areas with large number of injection wells but no seismicity. What distinguish seismic and non-seismic areas? - Stress field? - Existence of Faults? - Rock properties? In Oaklahoma seismicity rates peaked in 2015, most likely in response to regulatory measures to reduce injection volumes into the most problematic injection zone, the Arbuckle Group (Langenbruch and Zoback, 2016).

22 Some More Remarks Induced seismicity behavior is highly site- and operationspecific. The complex, nonlinear systems that drive inducedseismicity processes are not completely understood. Need for better site characterization of faults, stress and rock properties (brittle-ductile) Major Fault Stress and strain changes beyond area of pressure change Pressure change far beyond CO 2 plume Injection well CO 2 plume Minor faults

23 References Bauer, R. A., M. Carney, and R. J. Finley (2016), Overview of microseismic response to CO2 injection into the Mt. Simon saline reservoir at the Illinois Basin-Decatur Project, Int. J. Greenhouse Gas Control, 54, Cappa F. and Rutqvist J. Seismic rupture and ground accelerations induced by CO2 injection in the shallow crust. Geophysical Journal International, 190, (2012). Cappa F. and Rutqvist J. Impact of CO2 geological sequestration on the nucleation of earthquakes. Geophysical Research Letters, 38, L17313, (2011). Hornbach MJ, DeShon HR, Ellsworth WL, Stump BW, Hayward C, Frohlich C, Oldham HR, Olson JE, Magnani MB, Brokaw C, Luetgert JH. Causal factors for seismicity near Azle, Texas. Nature Communications 2015;6:6728. Morris JP, Hao Y, Foxall W, McNab W. In Salah CO2 storage JIP: hydro-mechanical simulations of surface uplift due to CO2 injection at In Salah. Energy Procedia 2011;4:3269e75 Rinaldi AP, Rutqvist J. Modeling of deep fracture zone opening and transient ground surface uplift at KB-502 CO2 injection well, In Salah, Algeria. International Journal of Greenhouse Gas Control 2013;12:155e67. Ringrose PS, Roberts DM, Gibson-Poole CM, Bond C, Wightman R, Taylor M, Raikes S, Iding M, Østmo S. Characterisation of the Krechba CO2 storage site: critical elements controlling injection performance. Energy Procedia 2011;4: 4672e9. Rutqvist J. The geomechanics of CO2 storage in deep sedimentary formations. International Journal of Geotechnical and Geological Engineering, 30, (2012). Rutqvist J., Vasco D., and Myer L. Coupled reservoir-geomechanical analysis of CO2 injection and ground deformations at In Salah, Algeria. Int. J. Greenhouse Gas Control, 4, (2010). Rutqvist J., Rinaldi A.P., Cappa F., Jeanne P., Mazzoldi A., Urpi L., Guglielmi Y., Vilarrasa V. Fault activation and induced seismicity in geologic carbon storage - Lessons learned from recent modeling studies. Journal of Rock Mechanics and Geotechnical Engineering, 8, (2016). Rutqvist J. Status of the TOUGH-FLAC simulator and recent applications related to coupled fluid flow and crustal deformations. Computers & Geosciences, 37, (2011). Rutqvist J., Cappa F., Rinaldi A.P., and Godano M. Modeling of induced seismicity and ground vibrations associated with geologic CO2 storage, and assessing their effects on surface structures and human perception. International Journal of Greenhouse Gas Control 24, (2014). Vasco DW, Rucci A, Ferretti A, Novali F, Bisell R, Ringrose PS, Mathieson AS, Wright IW. Satellite-based measurements of surface deformation reveal fluid flow associated with the geological storage. Geophysical Research Letters 2010;37:L Zhou, Q., Birkholzer, J.T., On the scale and magnitude of pressure buildup induced by large-scale geologic storage of CO2. Greenhouse Gas Sci. Technol. 1,