Geomechanical Assessment and WAG Optimization for Fault-Caprock Integrity in Deep Sandstone CO2-EOR

ABSTRACT: Geological safety assessment is fundamental for CO2 injection in reservoir development. This study presents an integrated evaluation framework that combines geomechanical simulation, fault stability assessment, and caprock sealing analysis to ensure geological safety during CO2 injection in the H-Block of the deep sandstone reservoir. The results indicate a normal faulting stress regime, with 15-20% stress attenuation near fault zones, influencing injection operations. Fault stability evaluation identifies three critical pressure thresholds: secure sealing below 54 MPa, transitional stability between 54 and 59 MPa, and instability above 59 MPa. Caprock breakthrough pressure analysis reveals significant anisotropy, with vertical measurements of 15.2 MPa exceeding horizontal values of 11.8 MPa, providing valuable insights for injection well optimization. Through parameter optimization, the proposed water-alternating-gas (WAG) injection scheme achieves a recoverable oil volume of 129.8 x 104 m3. These findings advance both methodological approaches and practical guidelines for CO2-enhanced oil recovery in deep reservoirs.