Oil reservoirs are high temperature and pressure environments that consist of porous rocks, oil, and various gases. Typically, after the primary and secondary oil recovery processes, at least 50% of the original oil still remains in the reservoir. One method for recovering additional oil, termed tertiary or enhanced oil recovery (EOR), involves injecting supercritical carbon dioxide (CO2), to displace and dissolve some of the remaining oil. Surfactants can be used to increase the sweep efficiency of the CO2.
Interfacial tension measurements
The interfacial tension between hydrocarbon, brine and CO2 at increased temperatures and pressures is a measure of the adhesion forces that play an important role in determining the effectiveness of the CO2-enhanced oil recovery. When surfactants are added into the mixture, the measurements become more complicated since pressurization of the chamber can cause changes in the surfactant concentration inside the measurement chamber.
High pressure tensiometry is a way of determining the lowest operating pressure at which the injected gas and the crude oil become miscible at the reservoir temperature. It gives a quantitative value in a short measurement for the minimum miscibility pressure (MMP). The quickness of the measurement is based on being able to measure the interfacial tension on multiple pressures with one loading while keeping the surfactant concentration constant.
Learn more from Associate Professor Sandro da Rocha, Wayne State University, in a recorded webinar: Measuring interfacial tension and contact angle at high pressures and temperatures.
Different enhanced oil recovery methods are used to alter the wettability of the reservoir rock. To study the wettability alteration at the reservoir conditions, an instrument where the measurements can be done at high pressures and temperatures are needed.
Unconventional oils, such as heavy oil, extra heavy oil, and bitumen, normally exist tightly on host solids such as rocks, sands and clay minerals. Successful liberation of unconventional oil from solids is essential for effective recovery.
In enhanced oil recovery wettability plays an important role as that determines the interactions between the solid (rock) and the liquids in the reservoirs (crude oil, brine). Wettability has been recognized as one of the key parameters controlling the remaining oil-in-place.