Relative Permeability from Unsteady-State Displacement Experiments: A Novel Analytical Estimation Technique

Relative permeability curves are a crucial part of numerical models for core flooding studies. These curves illustrate the fluids' performance during displacement procedures. Relative permeability can be computed from laboratory experimental observations. As in earlier conventional analytical solutions, information gathered during the fluid displacement process can be used to calculate the relative permeability of each fluid. Nevertheless, the resulting estimations of relative permeability were inaccurate even after accounting for the impact of capillary pressure. Pre-breakthrough values were overstated and occasionally showed non-monotonic behaviour for both fluids. This paper examines calculating methods and suggests a potential unique way for estimating relative permeability in order to enhance relative permeability curves for core flooding experiments in an unsteady two-phase (oil-water) flow. A variation of the Johnson-Busler-Nauman (JBN) approach is suggested, based on the estimation and use of normalized water saturation. Initially, several unsteady-state core flooding investigations were chosen from the published literature which used samples of mostly carbonate rock. Some secondary floods of high-salinity waters and other secondary floods of low-salinity waters with various fluid properties were represented by these displacement experiments. The relative permeability was determined using both our estimating method and the traditional analytical solution (with somewhat modified application procedures). Our approach yields reasonable pre-breakthrough results with accurate monotonic performance for both curves, as well as better values that are closer to those previously obtained using the numerical model by applying history matching. Compared to earlier analytical calculation methods, the estimation approach has been demonstrated to be appropriate for expressing relative permeability curves, particularly for the values calculated before to breakthrough. The proposed estimating approach can be used as an indicator (or range limit) to determine the final set of relative permeability through the history matching procedure. Unfortunately, more research on additional studies has shown that not all of them will yield similarly improved accuracy by using the method we have suggested. Some problems seem to be caused by other factors that affect the computation procedure. Unlike previous results, the numerical model results fit better with post-breakthrough relative permeability values calculated for additional tests using the traditional method. This may to highlight a weakness in our strategy. The computations of total mobility offer a potential foundation for identifying which tests can be reliably calculated using the suggested method or other techniques, and which should be employed in relative permeability estimates. To determine a general analytical technique for forecasting the optimal relative permeability curve, more research will be done in the future.