Analytical Study of Capillary Pressure Hysteresis and Its Impact on Multiphase Flow Simulation Accuracy in Niger Delta Heterogeneous Sandstone Reservoirs

Capillary pressure hysteresis, describing the difference between drainage and imbibition capillary pressure curves, has a significant but frequently neglected impact on multiphase fluid distribution and flow behaviour in heterogeneous sandstone reservoirs. This study analytically evaluates the magnitude of capillary pressure hysteresis in Niger Delta heterogeneous sandstone core samples and quantifies its impact on reservoir simulation predictions. Mercury injection capillary pressure measurements and porous plate imbibition capillary pressure measurements were conducted on thirty-six core plugs from three reservoir intervals with varying pore geometry complexity. Hysteresis scanning curves were measured between initial and residual oil saturation bounds using centrifuge methods at representative connate water conditions. The Land model and the Carlson method were fitted to the measured hysteresis data and implemented in an Eclipse 100 compositional simulation model of a representative heterogeneous Niger Delta sand. Production forecasts from twelve simulated development well configurations were compared between models incorporating hysteresis and models using conventional non-hysteretic two-phase curves. Results indicate that omitting capillary pressure hysteresis causes a systematic overestimation of predicted oil recovery by 4.2 to 6.8 percentage points in heterogeneous systems with strongly contrasting capillary properties between laminae. Sensitivity analysis confirms that hysteresis impact scales with the degree of vertical permeability heterogeneity, becoming negligible in highly permeable uniform sands. Keywords: capillary pressure hysteresis, multiphase flow simulation, Niger Delta sandstone, imbibition, reservoir heterogeneity.