Wetting Alteration by Brine and Crude Oil: From Contact Angles to Cores

Factors that affect wetting alteration of a rock upon contact with crude oil include composition of the oil and brine, temperature and duration of aging in oil, and initial water saturation. Similar factors affect contact angle measurements, but the relationship between the surface and core wetting conditions remains to be clearly demonstrated for crude oil/brine/rock systems. An asphaltic crude oil and two sodium chloride solutions of varying pH have been used to alter wetting of flat glass surfaces, two-dimensional etched glass micro-models, and two core materials: synthetic core composed of silica and alumina (Aerolith-10), and Clashach-a relatively clay-free sandstone. Wetting changes on flat glass surfaces are consistent with the wetting conditions established in synthetic silicate cores; the effect on oil recovery by waterflooding is shown. In Clashach sandstone cores, wetting is less directly influenced by the brine pH; both high and low pH cores are distinctly mixed-wet.