An Experimental Study of Alkaline Surfactant Flooding in Ultra Shallow Heavy Oil Reservoirs

Economic recovery of heavy oil from ultra shallow oil reservoirs (\u3c500 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 for the Pennsylvanian Warner sand in Western Missouri has been conducted. This work has included testing more than 30 commercial surfactants and using sands saturated with heavy oil (API 17). It has been found that a few of 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. Chemical flooding tests have found that using these surfactants is better than using other conventional ones. This study benefits the industry by demonstrating the applicability of alkaline surfactant flooding to the Warner sands of Western Missour. This paper presents the detail experimental methods necessary to extrapolate this work to other ultra shallow heavy oil reservoirs. In our experienments, viscosity of Missouri heavy oil can be reduced from 18518 cp to 2.5 cp at 25 °C through emulsion of certain surfactants. Emulsion of the heavy oil and formation brine is stable for several weeks at 25 °C. But heavy oil in the emulsion can be easily separated without addition of deemulsion agent. Alkaline-surfactant (AS) system can change wettability of oily sand from strongly oil-wet to waterwet. Heavy oil recovery by AS flooding test at 25 °C has been improved significantly. Considering 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 (\u3c500ft). Results of our work demonstrate that alkaline surfactant flooding can be effective on enhancing oil recovery in the ultra shallow heavy oil reservoirs