A New Device For Determining Wetting Preference Of Crude Oil/brine/solid Systems

A dynamic Wilhelmy plate technique has been developed for quantitative determination of the wetting preference of crude oil/brine/solid systems. This method is simpler and less operator-dependent than the standard sessile drop (parallel crystal plate) technique used in the petroleum industry. This paper focuses on the laboratory setup required for the dynamic Wilhelmy plate technique to test crude oils, allowing for aging studies with oxygen-sensitive crude oils. When comparing forces in the reservoir, capillary forces are always described as the product of interfacial tension and the cosine of the contact angle, which is termed the adhesion tension. The Wilhelmy test gives a direct quantitative determination of the adhesion tension and a qualitative visual indication of wetting preference. The results graphically illustrate the wetting preference of the oil/brine/solid system. Three types of wetting preference have been observed: waterwetting, oil-wetting, and hybrid-wetting. In the first two cases, both the water-advancing and water-receding fronts indicate the same wetting preference. The hybrid-wetting system shows an oil-wetting character when water advances and a waterwetting character when water recedes across the solid. A systematic study of the wetting character of several mineral surfaces important to the petroleum industry has been performed, including studies on glass, marble (calcium carbonate), and dolomite. The dynamic Wilhelmy test uses a thin solid plate suspended from a balance that is moved through the crude oil/ brine interface inside an anaerobic vessel. The measured change in force as the plate passes through the oil/brine interface relates directly to the adhesion tension at that interface. The apparatus is computer controlled and monitored, allowing high quality data to be obtained and analyzed.