Sca 2001-65.pdf

Accurate estimation of capillary pressure and relative permeability curves are very important for evaluating hydrocarbon recovery processes. Also, resistivity index data are important in evaluating fluid distributions in reservoirs during these processes. All these parameters are path dependent i.e. different in drainage and imbibition processes, commonly known as hysteresis, which makes them complicated to predict. Laboratory tests have therefore been performed on four North Sea chalk core samples to measure the wettability index and determine the hysteresis in capillary pressure, relative permeability and resistivity index. The cores were extracted using toluene and methanol, and a light oil (n-decane) and brine saturation equivalent to the formation water were used in the displacement processes. Varying levels of hysteresis were observed. Hysteresis effects were significant in capillary pressure and relative permeability curves and not so pronounced for the resistivity index.