When capillary pressure is important water/oil and gas/oil displacement tests need to be interpreted carefully to establish the underlying relative permeability, since the JBN method will under estimate oil recovery and artificially suppress relative permeabilities. Previous work used a recasting of the Darcy flow equations to develop a method for interpreting displacement tests by direct processing of saturation data. These recast equations have now been used as the basis for a new coreflood simulator, which allows pressure drop and saturation data to be analysed separately. This approach has a number of advantages over conventional core flood simulators: the regression problem can be decoupled into three independent steps, the actual observed saturation history at the core outlet can be used as a boundary condition, and the interpreted fractional flow curve is independent of any assumptions about the phase pressure that is measured at the outlet. Regression to the observed data is achieved using a genetic algorithm. Analysis of saturation data can be made for the full length of the core or for data from defined subsections. This can be valuable when considering composite cores or when parts of the core are significantly affected by heterogeneity

The simulator is used to interpret results from a four rate waterflood on a carbonate core, to obtain relative permeability curves. The shape of the capillary pressure curve was also derived, however the cross-over saturation is not uniquely defined on the basis of the pressure measurements made, which were not phase selective. The simulator has also been used in a coreflood design mode, to select the minimum number of flow rate steps (including optimal selection of the individual rates) needed to derive reliable relative permeability curves, without unnecessarily complicating the laboratory flooding sequence