Investigation of caprock integrity for CO2 sequestration in an oil reservoir using a numerical method

Geological sequestration of carbon dioxide is a mitigation method for reducing greenhouse gas emissions to the atmosphere. Success and safety of a CO2 sequestration operation is strongly dependent on the mechanical stability of the caprock overlying the storage reservoir. Subsurface CO2 injection results in a pore pressure increase and thereby a decrease of the effective stresses, which may lead to caprock failure and subsequent CO2 leakage. In this study, a three-dimensional geomechanical finite element model was built by using Abaqus software to investigate the geomechanical effects of CO2 injection on the caprock and to estimate the risk of caprock failure. The CO2 injection induced pore pressure increase, vertical displacement of the caprock, and the effective stress decrease have been investigated. The results show that the caprock remains stable during the 10-year injection period under the considered conditions. Through quantitative sensitivity analysis, the effects of the input parameters are ranked. CO2 injection rate and initial stress state were found to have the most significant impact on the caprock failure tendency. Results of the numerical model were also validated against analytical solutions.