Characterization of Rock/Fluids Interactions at Reservoir Conditions

Abstract

In this study, interfacial phenomena of spreading, wettability, and rock/oil adhesion interactions in complex rock/oil/water systems were characterized at reservoir conditions of elevated pressures and temperatures. Capabilities of both ambient and reservoir condition optical cells were used for measuring the oil/water interfacial tension and dynamic (the water-receding and the water-advancing) contact angles for various complex rock/oil/water systems. Well known sessile oil drop volume alteration method was successfully used in this study for evaluating the applicability of the modified Young’s equation for characterizing the line tension in complex rock/oil/water systems at reservoir conditions. This appears to be first time when rock/fluids interactions in complex rock/oil/water systems of petroleum engineering interest have been characterized in terms of the measured oil/water interfacial tension (IFT), wettability, line tension, and the work of adhesion at elevated pressures (up to 14,000 psi) and temperatures (up to 250°F) using representative reservoir fluids and common reservoir rock minerals surfaces (glass, quartz, dolomite or calcite). Different oil (recombined live oil and stock-tank oil) and aqueous (deionized water, synthetic reservoir brines, synthetic sea water, and 35,000 ppm NaCl solution) phases were used to study the effects of fluids composition and experimental conditions on the oil/water IFT and the wetting characteristics of complex rock/oil/water systems of petroleum engineering interest. The effect of rock mineralogy was investigated by conducting the experiments with different mineral surfaces (quartz and calcite). A new equation was developed using the concepts of the line tension and the work of adhesion to estimate the adhesion energy per unit volume correlatable to maximum disjoining pressure in complex rock/oil/water systems. This equation uses the measured data of the oil/water interfacial tension (IFT) and dynamic contact angles, and an assumed thickness of the aqueous wetting films. The experimentally estimated adhesion energy per unit volume values for two glass/recombined live oil/synthetic reservoir brine systems using this new equation were compared with the maximum disjoining pressure values derived from the published reservoir condition disjoining pressure isotherms for the glass/Yates crude oil/Yates brine systems. The experimentally estimated values were found to be one order of magnitude higher than the theoretical values.