Enhanced heavy oil recovery by alkali-surfactant in the Pennsylvania Warner sandstone

Abstract

In this research, a study of the non-thermal method of alkaline-surfactant (AS) flooding to enhance heavy oil recovery from the Pennsylvanian Warner sandstone reservoir in Western Missouri was conducted. This work includ [sic] testing approximately 30 commercial surfactants and using a heavy oil sample with an API of 17. It was found that a number of surfactants could create stable emulsions. The viscosity of heavy oil could be reduced from 18,518 cp to 2.5 cp at 25⁰C through emulsification of certain surfactants. One of the major findings was that the emulsion created by the commercial surfactant, Igepalʼ CO-530 was stable at 25⁰C, but the oil and brine could be readily separated at 40⁰C. The addition of alkaline to Igepalʼ CO-530 produced a more stable emulsion of the heavy oil and formation brine. This emulsion separated automatically at 55⁰C. Core flooding tests were performed by the use of Igepalʼ CO-530 and alkaline NaOH at 0.6 wt% in the synthetic brine. These tests were conducted under both oil-wet and water-wet reservoir conditions, but the highest oil recovery always obtained under water-wet condition. The wettability alteration was studied through the measurement of interfacial tension and the contact angle of water on the sandstone surface treated with a model of the heavy oil sample was measured using Goniometer. Results indicated that wettability of the sandstone surface pre-treated with heavy oil could be effectively changed to water-wet by the surfactants. Additionally, spontaneous imbibition tests were conducted and it was found that the oil recovery was between 40% and 60% by nonionic surfactants, 10% and 20% by anionic surfactants, and 0% by formation water only. These results were used to conduct a simulation. The simulation results matched the experimental work, suggesting that further testing of AS flooding should be conducted --Abstract, page iii