Seismic and Geomechanical characterisation of seals in the deep carbonate reservoir of the KX field, offshore sarawak: implications for CO₂ storage

Caprock integrity is the primary safeguard for geological CO₂ storage, preventing upward migration and leakage. This study presents an integrated seismic and geomechanical assessment to characterise the sealing intervals of a carbonate reservoir located in the KX field, which is situated in the Southwest Luconia Province for CO₂ storage. A 3D post-stack seismic volume was interpreted to map structure and discontinuities; variance attributes delineated fault-related lineaments, and model-based acoustic-impedance inversion provided elastic trends. Log-derived dynamic elastic properties were calculated and calibrated with laboratory core results. A 3D geomechanical model was constructed from the elastic volumes and calibrated well trends to evaluate stresses, strains, and pore-pressure behaviour in the sealing section. Two stratigraphic sealing units (Seal A and B) were characterised. Seal A directly overlies the reservoir and is more variable, with sandy/silty interbeds and local overpressure, and exhibits lower stiffness and greater deformability with a young modulus (20–30 Gpa), pore pressure from 2000 to 4200 psia and UCS from 44 to 62 Mpa. Seal B is the secondary seal overlying Seal A, having a higher static Young’s modulus (10–20 GPa), lower deformability, near-hydrostatic pore pressure (1800–3600 psia), and UCS (30–46 mPa). Faults interpreted on the variance attribute locally cut the sealing section. The mapped throws and geometries do not present evidence of breach where hydrocarbons are trapped, indicating effective across-fault sealing at present conditions. The outcome of this study contributes to the development of the KX field for target carbon storage, and the workflow is suitable for other fields with similar challenges.