| knowledge of the generation of oil-wet spots in reservoir rock and the location of those spots is important for understanding the reservoir behavior. Measurements of physical and electrical properties should be made on the core sample retaining its native wettability in the reservoir.;In this research a laboratory procedure was developed to restore the wettability of cleaned Berea and dolomite cores to the wetting conditions that exist in oil reservoirs. The core samples were initially saturated with 5% NaCl brine and then flooded with kerosene followed by the reagent mixed with kerosene and stored in an oven for one day. The core samples were then flooded with kerosene to remove the remaining reagent in the pores. The core samples at this stage are called the "restored core samples.";The properties measured on both cleaned and restored core samples were porosity, permeability, capillary pressure as a function of water saturation, irreducible minimum water saturation, residual oil saturation, electrical formation factor, resistivity index, saturation exponent, and wettability index. The irreducible minimum water saturations measured on the restored core samples were higher than those measured on the cleaned core samples. The residual oil saturations measured on the restored core samples were lower than those measured on the cleaned core samples. The saturation exponents measured on the restored core samples were increased from 2.5 to 20 as the water saturations were increased from 40% to 95%. The saturation exponents measured on the cleaned core samples remained between 1.7 and 2.5. As the measurements were repeated on the restored core samples, the irreducible minimum water saturations were decreased, the residual oil saturations were increased, and the saturation exponents were decreased toward the values of the cleaned core samples.;The prediction equations were developed to correlate the residual oil saturation with other reservoir rock properties. Without considering the effect of wettability, the successful correlation could not be made. The inverse saturation exponent together with porosity and permeability in... |
