Effect of Saturation Hysteresis and Wettability on Saturation Exponent Calculation

The determination of fluid saturation is vital for the estimation of hydrocarbon in place which is the base for economic decision making about reservoir production. Archie’s equations are the most prevalent equations used for saturation calculation. One of the important parameters in these equations is saturation exponent. Saturation exponent has fundamental difference comparing with other parameters which are cementation exponent and tortuosity. Cementation exponent and tortuosity mostly depend on rock type but saturation exponent depends on the distribution of fluids and therefore the hysteresis of saturation during imbibitions and drainage and also wettability. The purpose of this research is an investigation into the effect of saturation hysteresis and wettability on saturation exponent. The saturation exponent was measured from primary drainage to secondary drainage with a four-electrode system at reservoir temperature with reservoir fluids on some cylindrical core samples. Dynamic porous plate technique was used، for which full capillary pressure curves and wettability with combined Amott-USBM were determined simultaneously. It was concluded that the saturation hysteresis affects saturation exponent in different samples during imbibition and drainage and cause it to range from 0. 1 to 0. 66; the variations were higher in oil-wet samples than water-wet samples.