Determination of Capillary Pressure from Imbibition Data for Niger Delta Porous Media

Abstract

Capillary pressure is of fundamental significance in reservoir engineering. Knowledge of capillary pressure is necessary for the design of injection projects. This study is therefore aimed at the determination of capillary pressure from imbibition data for Niger Delta cores. The samples used for this study were collected from three fields representing the Niger Delta depositional belts. Spontaneous cocurrent imbibition experiment was conducted using these samples for systems of oil-brine-reservoir rock. Two groups of core samples were used for this study-Group A and Group B. For Group A rock samples, the calculated capillary pressures of high permeability rocks increases at low interfacial tension but decreases at high interfacial tension while for low permeability rock samples, the capillary pressure increases at high interfacial tension. For Group B samples, there was an increased capillary pressure for samples whose permeability are low at low interfacial tension but decreased as the interfacial tension increases. The increase of capillary pressure as the interfacial tension is lowered by low permeability cores shows that the wettability of the cores has been altered to a more water-wet rock. There was a reduction in the capillary pressure for the high permeability core at low interfacial tension but increased at high interfacial tension which also signifies a slight wettability alteration. The capillary pressures calculated in this work were consistent with the change in interfacial tension. The oil-water-rock systems which had greater interfacial tensions gave greater capillary pressures.