Integrated Geological and Petrophysical Assessment of Caprock Integrity and Reservoir in FX Field, Central Luconia, Sarawak

ABSTRACT Subsurface site characterisation is critical for assessing CO 2 storage in depleted reservoirs with proven trapping histories. The unresolved gap in Central Luconia is a coupled evaluation of multi‐layered seal performance together with the effect of NE–SW faults on containment. This study fills a regional gap by integrating multi‐layer seal characterisation with 3D structural and petrophysical modelling to quantify seal competency and reservoir storage properties on containment in a Central Luconia carbonate platform. Acoustic impedance spans 2.6–10.8 × 10 6 kg m −2 s −1 . Reservoir carbonates show 6.0–10.0 × 10 6 kg m −2 s −1 , whereas shales fall near 4.0–5.0 × 10 6 kg m −2 s −1 . Caprock thickness is 50–150 m. Reservoir thickness is 100–300 m. Effective porosity in the reservoir is 0.20–0.40 m 3 /m 3 . Reservoir permeability locally exceeds 2500 mD, consistent with well‐connected pore networks and possible karst features. Seal units exhibit permeability near 1.6 mD with porosity mostly below 0.20 m 3 /m 3 . Inversion highlights low‐impedance streaks within seals that correlate with sandy or shaly‐sand interbeds. NE–SW faults traverse reservoir and caprock and coincide with lateral variability in rock properties. These results indicate multi‐layered seals with regionally effective continuity, alongside localised leakage risk near major NE–SW faults and sandy interbeds. The integrated workflow reported here is directly applicable to similar carbonate fields in Central Luconia and comparable basins.