AN EXPERIMENTAL STUDY OF ALKALINE SURFACTANT FLOODING FOR ULTRA SHALLOW HEAVY OIL RESERVOIRS

Economic recovery of heavy oil from ultra shallow oil reservoirs (<500 ft) is of interest as many such reservoirs exist throughout Utah, Missouri, and California. EOR methods, such as thermal flooding, can be limited in these ultra shallow situations, and other methods of heavy oil recovery are of interest. A study of alkaline‑surfactant flooding in the Pennsylvanian Warner sand of Western Missouri has been conducted. This work has included testing more than 30 commercially available surfactants using sands saturated with heavy oil (API 17). It has been found that a few surfactants can create a stable emulsion with the Warner heavy oil and the formation brine. In all cases examined, highest recovery is from water wet sands. Applications: This study benefits the industry by demonstrating the applicability of alkaline surfactant flooding to the Warner sands of Western Missouri, and detailing experimental methods necessary to extrapolate this work to other ultra shallow heavy oil reservoirs. Results, Observations, Conclusions: Viscosity of Missouri heavy oil can be reduced from 28834 cp to 2.5 cp at 25 B0C through emulsion of certain surfactants. Emulsion of the heavy oil and formation brine is stable for several weeks at 25 B0C. But the heavy oil in the emulsion can be easily separated without addition of de‑emulsion agent. Alkaline‑surfactant (AS) system can change oily sand wettability from strongly oil‑wet to water‑wet. Heavy oil recovery by AS flooding test at 25 B0C has been improved significantly. Significance: The total volume of heavy oil in the United States is 100~180 billion barrels and a significant amount of these reserves are in ultra shallow reservoirs (<500ft). Results of the current work demonstrate that alkaline surfactant flooding can be effective in enhancing oil recovery in the ultra shallow heavy oil reservoirs.