Geomechanical Risk Assessment for a CCS Project in North Malay Basin

Abstract A field-scale geomechanical analysis is carried out on a depleted gas reservoir, located offshore Malaysia in North Malay Basin. The field is evaluated for CO2 storage to identify the risks related to fault instability and caprock integrity. The analysis is conducted using a finite element geomechanical model coupled to the reservoir dynamic simulation model. The first 1D geomechanical model for the study field was constructed in 2008. Since then, the model was updated using additional data acquired from new offset wells and a 3D static geomechanical model was constructed for the field. In the current study, a finite element geomechanical model is constructed for the field and coupled to a reservoir dynamic model. The results of the geomechanical simulation are used to investigate the stability of the storage caprock and the faults in the area close to the CO2 plume. The risk of fracture initiation in the caprock is investigated by comparing the storage layer pore pressure (increased due to CO2 injection) against the fracture initiation pressure of the caprock immediately above the storage layer (reduced due to reservoir expansion). The risks associated with fault instability are studied by calculating the shear stresses developed on the surface of the fault from the numerical model and comparing them against the shear strength of the fault. The results show that the risk of failure is relatively higher close to the injectors in the crest of the structure and close to the faults.