Lee, Jaewon (School of Mining Engineering, The University of New South Wales, Shahid Bahonar University of Kerman) | Min, Ki-Bok (Department of Energy Systems Engineering, Seoul National University) | Rutqvist, Jonny (Earth Sciences Division, Lawrence Berkeley National Laboratory)
In the context of Carbon Capture and Storage (CCS), the injection of CO2 induces a geomechanical change in the reservoir, which is an important issue for the stability of CO2 sequestration. The injection of CO2 makes the fluid pressure increase, resulting in ground heaving. In addition, the increased fluid pressure is expected to be a source of shear slip of fractures in the caprock, which leads to the leakage of CO2 and microseismicity. In this study, we conduct a multi-phase coupled thermo-hydromechanical analysis to investigate the geomechanical aspect of CO2 storage focusing on ground heaving and leakage of CO2. In order to describe the caprock, fractures are considered implicitly and explicitly. For the analysis using implicit fractures, the fracture orientations were generated using the Latin Hypercube Sampling (LHS) method. In order to investigate the effect of orientation of principal stresses, we considered three kinds of stress regimes with the pore pressure evolutions calculated using a TOUGH-FLAC analysis. Based on these generated fracture orientations and stress distribution information, the probability of fracture shear slip was examined using Mohr-Coulomb failure criteria. This study allows for a quantitative description of ground heaving and leakage potential induced by shear slip of fractures, which is an important parameter for performance assessment of CO2 reservoir.
For the geosequestration of CO2, fluid injection is the triggering force for the hydro-mechanical change of reservoir, and ground heaving and shear slip of fracture are critical issues for the stability CO2 reservoir. When a fluid is injected into the reservoir, the increased pore pressure makes the ground heave. For example, at the In Salah project in Algeria, approximately 5 mm/year of ground heaving was observed, with the affected area being several kilometers from the injection well .