Vol 2 Chapter 6: Predicting and Monitoring Geomechanical Effects of CO2 Injection
Jurgen E. Streit, Anthony F. Siggins and Brian J. Evans
Abstract: Predicting and monitoring the geomechanical effects of underground CO2 injection on stresses and seal integrity of the storage formation are crucial aspects of geological CO2 storage. An increase in formation fluid pressure in a storage formation due to CO2 injection decreases the effective stress in the rock. Low effective stresses can lead to fault reactivation or rock failure which could possibly be associated with seal breaching and unwanted CO2 migration. To avoid seal breaching, the geomechanical stability of faults, reservoir rock, and top seal in potential CO2 storage sites needs to be assessed. This requires the determination of in situ stresses, fault geometries, and frictional strengths of reservoir and seal rock. Fault stability and maximum sustainable pore fluid pressures can be estimated using methods such as failure plots, the FAST technique, or TrapTester (Badley Geoscience Ltd) software. In pressure-depleted reservoirs, in situ stresses and seal integrity need to be determined after depletion to estimate maximum sustainable pore fluid pressures. The detection of micro-seismic events arising from injection-induced shear failure of faults, fractures and intact rock is possible with geophone and accelerometer installations and can be used for real-time adjustment of injection pressures. In the event of injected CO2 opening and infiltrating extensive fracture networks, this can possibly be detected using multi-component seismic methods and shear-wave splitting analysis.
Carbon Dioxide Capture for Storage in Deep Geologic Formations – Results from the CO2 Capture
Project Geologic Storage of Carbon Dioxide with Monitoring and Verification - Volume 2
Edited by: Sally M. Benson, Lawrence Berkeley Laboratory, Berkeley, CA, USA
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