Estimation Of Height Of Oil -Water Contact Above Free Water Level Using Capillary Pressure Method For Effective Classification Of Reservoirs In The Niger Delta

Abstract

An estimate of oil-water contact (OWC) and the understanding of the capillary behaviour of hydrocarbon reservoirs are vital for optimum reservoir characterization, hydrocarbon exploration and production. Hence, the height of oil-water contact above free water level for different rock types from some Niger Delta reservoirs were estimated here. Data obtained from oil-displacing brine (drainage) capillary pressure tests using refined oil as simulated brine formation or reservoir fluid on various rock samples were utilized to illustrate the basic capillary behaviour of ten hydrocarbon reservoirs within Niger Delta of Nigeria and to estimate the (OWC) above Free Water Level. Almost all the samples show plateau prominence and high permeabilities of (422-4110) x 10 Hm at very low displacement pressures with well sorted grains which is indicative of good reservoirs This is further confirmed by their low heights of 100% water saturation above free water level of 2.11m, 1.41m, 2.46m, 1.05m, 2.07m, 1.72m, 1.79m, 1.76m, and 1.05m, and corresponding to a depth range of 3030 to 3261 m which indicate good quality reservoirs. Only one sample showed evidence of low yield reservoir with high height of 5.62m at a depth of 3266 m. The derived knowledge of water density, oil density and saturation height function adequately estimates the quality of reservoirs and classify them in terms of prominence of the plateaux and channels. The results show that the typical Niger Delta reservoirs are of good quality as confirmed by the relatively low shale presence.

Keywords: Oil-water contact, capillary pressure, reservoir characterization, saturation height function and permeabilities

Nigerian Journal of Physics Vol. 19 (2) 2007: pp. 303-311