Relative Permeability and Wettability of Rocks Obtained From Their Capillary Pressure and Electrical Resistivity Measurements

Abstract

AbstractRelative permeability and Capillary pressure characteristics of reservoir rocks are usually determined using core analysis. In the absence of representative core sample, resistivity log-derived water saturation in the transition zone may be used to depict capillary pressure curve and, in turn to determine relative permeability characteristics from petrophysical correlations. Most of reported research works have investigated the relative permeability from a steady state and unsteady-state techniques. The technique of measuring relative permeability using resistivity measurements almost absent from the reported works. Hence, the main objective of this work is to determine the relative permeability from the resistivity measurements and compare it with those obtained from capillary pressure data using the same cores. Also, it is intended to find out which models could be used for calculating the relative permeability from capillary pressure realizing a best fit matches with the relative permeability obtained from resistivity measurements. In addition, to determine the types of wettability from resistivity measurements. Results and analysis indicate that the capillary pressure and resistivity measurements result in significant different irreducible water saturation values. This, in turn, results in substantially different relative permeability characteristic curve. Also by analogy, a semi analytical method was to be developed to infer relative permeability from resistivity index and free water saturation. In most cases, the Brook-Corey and Corey models, may be the best fit match to the relative permeabilities of wetting and nonwetting phases respectively obtained from resistivity measurements. Therefore, wettability was determined using the values of water saturation exponents, water saturation at crossover point. The results indicate that, the wettability of Berea cores was neutral-mixed wet. However the wettability of the synthetic cores compacted at 3000 psi, was strongly water wet.