4D Geomechanical Modeling for Carbon Storage Risk Mitigation in Depleted Sandstone Reservoirs Offshore Malaysia

Abstract Geomechanical challenges in geological CO2 storage operations, such as caprock integrity, fault reactivation, wellbore deformation, and surface uplift during prolonged CO2 injection, can compromise containment and result in leakage. To mitigate these risks, it is crucial to comprehensively understand the underlying physical processes and develop advanced numerical models that incorporate chemical, thermal, and rock mechanical responses. These models are essential for evaluating subsurface risks in both near-wellbore and reservoir-wide areas. This study employed 4D coupled geomechanical modeling to evaluate the geomechanical risks associated with CO2 storage in laminated sandstone reservoirs offshore Malaysia. Five 1D geomechanical models were developed and calibrated using rock mechanical testing and field data, including in-situ stress measurements, caliper logs, and wellbore stability events. These models served as inputs for populating 3D geomechanical model properties using the Sequential Gaussian Simulation method and co-kriging with porosity. Laboratory studies on CO2-rock interactions informed the degradation of rock mechanical properties, which was incorporated into the CO2 injection scenarios. Results from thermal dynamic modeling were integrated into the 4D coupled geomechanical models to analyze the cooling effects of CO2 injection and their impact on geomechanical risks. The coupled modelling conducted identified safe caprock pressure margin for the reservoirs of interest whereby maximum injection pressures were determined for base and high case CO2 storage simulations. The simulation results show the impact of CO2 cooling resulted in less stable stress state closer to the failure envelope. Potential fault reactivation was evaluated based on fault plastic strain magnitude and distribution, and proximity of the faults to the injector wells This study highlights the geomechanical risks of CO2 injection in laminated sandstone reservoirs, adding value to CO2 storage assessments through interdisciplinary collaboration. It emphasizes the importance of a coupled chemo-thermo-poroplastic approach for a comprehensive evaluation of geomechanical risks in CO2 storage development projects.