Lithofacies Interpretation through Capillary Equilibrium Analysis in the Transition Zones

Summary The characterization of lithofacies along wells is the first step before considering generating geological models. In this paper, a method to improve the well characterization in term of lithofacies is presented. This approach based on the relationship between capillary pressure and saturation associated with each lithofacies allows characterizing the lithofacies automatically along wells in transition zones. The saturation of fluids depends on the rock lithofacies, the fluid properties, the rock-fluid interactions, and must be calculated in order to satisfy the gravity-capillary equilibrium. From the well log data, the water saturation is assumed to be known. The aim of the method is to identify the capillary pressure curve that satisfies the calculated capillary pressure and the observed water saturation of the cells along the wells. The first step consists of calculating the pressure of each phase in the reservoir. From the pressure of each phase, the capillary pressure Pc is deduced. The lithofacies associated with the capillary pressure curve closest to the point [Sw, Pc] is assigned to the cell. An application on the Brugge Field is presented.