Assessing Geomechanical Risks in Large-Scale Reservoirs: A Two-Way Coupled Geomechanics Modeling Approach with Integrated Safety Factor Screening for CO2 Storage

Abstract This paper addresses the geomechanical risks associated with CO2 sequestration in large-scale, highly heterogeneous reservoirs. A novel 2-Way Coupled Geomechanics Modeling approach is developed to estimate the effect of fault reactivation caused by CO2 injection on the pressure field in nearby rock formations. This approach integrates a Safety Factor (SF) to evaluate the hydro-mechanical stability of adjacent faults under different injection rates. The proposed methodology utilizes a 2-way coupled geomechanics and reservoir simulator to evaluate reservoir behavior for both the concept model SPE1 and a large complex synthetic model, incorporating a robust discontinuity treatment to accurately capture the effects of faults and fractures on reservoir performance. This approach enables the simulation of large-scale models, providing a comprehensive understanding of the reservoir's behavior during CO2 injection. A safety factor-based screen tool is employed to rapidly assess formation integrity, facilitating swift risk identification and evaluation of the interaction between fault and reservoir permeabilities. The results highlight the significant impact of reservoir heterogeneity on the assessment of reservoir integrity during CO2 injection. A safety factor-based approach is used to evaluate the integrity of both the SPE1 concept model and the large synthetic sector model, considering both cohesion and cohesionless faults. The study demonstrates that when the safety factor of all grid cells remains greater than 1, the reservoir integrity is preserved, and provides insight into how geological configuration, geomechanical properties, and operating conditions influence the risk of fault reactivation. The integration of advanced numerical techniques with the safety factor-based screen tool enables rapid identification of formation failure and CO2 leakage risks, while sensitivity analyses provide a robust framework for future studies on fault stability and induced seismicity. This comprehensive approach ultimately aids in the development of more effective risk assessment and mitigation strategies, ensuring the safe and efficient storage of CO2 in heterogeneous reservoirs.