Method for determining oil and water saturation of core samples at

Abstract

A method and apparatus is provided to determine the amount of oil and water or brine in a representative core sample of reservoir rock at an overburden stress which approximates reservoir stress conditions. The core sample is initially saturated with reservoir hydrocarbon (crude oil) and aqueous fluids (water or brine). The core sample is surrounded with an elastic jacket, or sleeve, and placed in a confining pressure vessel that simulates reservoir overburden stress on the core sample. The hydrocarbon (oil) fluids and aqueous fluids (water or brine) are than extracted from the core sample with a solvent capable of dissolving both aqueous and hydrocarbon fluids. The solvent and aqueous fluids are separated from the hydrocarbon fluids by evaporation. Thereafter the aqueous fluids are separated from the solvent by extraction. The amounts of oil and aqueous fluids from the sample may be separately determined. The volume of the hydrocarbon fluids and aqueous fluids is determined from their weight and density or from direct volume measurement. For a rock sample fully saturated with a combination of oil and aqueous fluids, the total pore volume is the sum of the volumes of the two fluids and the fluid saturation is then the ratio of the fluid volume to the pore volume.