Conditioning Capillary Pressure Data to Improve Saturation-Height Modelling in Microporosity-Dominated Barik Formation

Comprehensive understanding of saturation distribution and state is essential for forecasting reservoir performance, estimating recoverable volumes, and optimizing completion costs. Tight sandstone gas reservoirs often experience complex histories of burial, diagenesis, structural changes, fluid pressure, and saturation dynamics. Diagenesis masks primary depositional features through compaction, cementation, and dissolution, thereby increasing the complexity of pore spaces and pore throats. Complex pore architecture coupled with cycles of drainage and imbibition make the prediction of water saturation (Sw) across varying rock qualities challenging. The Barik hydrocarbon column shows signs of at least one imbibition event, evidenced by approximately 500 m of gas-saturated reservoir, a sharp 2-4 m transition zone, and more than 200 m of residual gas interval. Laboratory analyses were conducted to characterize the complex pore structure and fluid distribution within the Barik reservoir. The Saturation-Height Modeling (SHM) workflow involved three key stages. First, Mercury InjectionCapillaryPressure (MICP) data were converted to a gas-water system under in-situ conditions, with corrections for clay-bound water using brine salinity and Cation Exchange Capacity (Qv), and adjustments for non-clay microporosity based on NMR and petrographic thin-section observations. Second, capillary pressure curves were fitted to Leverett-J, Brooks-Corey, and Thomeer models using Python's SciPy non-linear least-squares method. Imbibition modeling required conditioning mercury extrusion data and developing a residual gas saturation model below the Free Water Level (FWL), incorporating Counter-Current Imbibition (CCI) trapped gas measurements linked to rock quality. Third, the SHM was validated against independent water saturation measurements (Dean-Stark and resistivity-based models), and the FWL depth was optimized for consistency with observed saturation profiles. Clay-bound water correction of MICP was minimal due to high brine salinity and low clay content. Non-clay bound water correction ranged from negligible in high-qualityrocksto15saturationunits(s.u.)inpoorer-quality reservoirs. Reduced rock quality was linked to lithic and ductile grains, K-feldspar leaching, and increased dolomite and quartz cementation, resulting in complex pore structures inaccessible to Porous Plate experiments. Among tested models, the parametrized Leverett-J function gave the best fit to the bound water-corrected mercury extrusion data, with parameters tied to porosity and permeability. The match between SHM andArchie Sw (Sw_Ar) above the current FWL is generally strong, except in intervals with localized stratigraphic water trapping. Below the FWL, Sw_Ar is up to 20 s.u. lower than SHM, particularly in more heterogeneous, less amalgamated facies, suggesting the presenceof movablehydrocarbons in those zones. Conventional SHM workflows utilizing MICP and FWL derivedfrompressure gradient analysisdonot accurately predict Sw distribution in reservoirs with significant diagenetic alteration such as the Barik. Disparities between independent saturation methods can be as much as 20 s.u. Conditioning MICP for clay and non-clay effects and adapting alternative SHM models to fit imbibition end points, yields an accurate match between different Sw sources. Above the FWL, discrepancies highlight trapped water at sandstone bases, while mismatches below the FWL indicate inefficient imbibitioninlaterallyisolatedreservoirsthat retainsome movable hydrocarbons. These insights have supported 1 SPWLA67th Annual Logging Symposium, May 16-20, 2026 accurate volumetric assessments, enhanced reservoir performance predictions, and informed completion optimization strategies.