Simultaneous determination of capillary pressure and relative permeabilities

Simulation of multiphase flow in porous media requires knowledge of relative permeabilities. Such data can be obtained from laboratory experiments, either steady state or un-steady state methods. Steady state experiments are time consuming, and can run over several days to acquire a complete set of relative permeabilities. Unsteady state methods are limited to displacements where the assumptions underlying the Buckley-Leverett theory is satisfied and capillary pressure must be ignored. Capillary pressures are generated where interfaces between two immiscible fluids exist in the pores (capillaries) of the reservoir rock. Due to the interfacial energy of the interface between the two phases, a difference in the pressure across the interface results in a curvature of the interface. It is usual to consider one phase as a wetting phase and the other as a nonwetting phase. However, intermediate cases occur which can greatly complicate the picture. In this paper a simultaneous determination of relative permeability and capillary pressure was achieved from the results of a single two phase flow experiment using Sendra Software. By using this software a first simulation was performed and then the results were history matched using core flood data. The core flood experiment is a standard imbibition or drainage displacement with an imposed difference in pressure. A four-step core-flooding scheme provides the differential pressure across the core, production data as a function of time, injection rates from which the relative permeabilities and capillary pressures are computed for both drainage and imbibition by Sendra. Finally the capillary pressures and relative permeabilities were compared using different correlations available in the software. After comparing the different correlation for relative permeabilities and capillary pressure the best correlation was selected for each.