Experimental Investigation of the Effects of Temperature, Pressure, and Crude Oil Composition on Interfacial Properties

Summary The wettability of the fluid/rock system affects the distribution of fluids within a porous medium; this distribution in turn strongly affects displacement behavior and oil recovery efficiency. This paper is an investigation of the influence of temperature, pressure, and oil composition on the wettability of a specific carbonate reservoir. Contact-angle measurements were used to quantify wettabilities on calcium-carbonate crystals. The experimental conditions included varying temperature and pressure for both dead crude oil and oil recombined to the original bubblepoint. In addition to quantification of wetting properties, interfacial tension (IFT) between oil and water was measured, and formation of rigid films was observed. A complete reversal from a predominantly oil-wet system at lower temperatures to a predominantly water-wet system at higher temperatures was found. Pressure alone had little effect on the wettability of the system. IFT between crude oil and brine showed an increase with increase in temperature under anaerobic conditions, whereas at aerobic conditions, IFT decreased with increase in temperature. The tendency to form rigid films at the crude-oil/brine interface was found to be temperature-dependent. The formation of rigid films was stronger at lower temperatures.