Insights into Tight Reservoir Wettability and Its Alteration Through Oil Aging and Surfactant Adsorption
Wettability and capillary pressure play crucial roles in controlling fluid flow and distribution in tight/shale oil reservoirs with its nano-to micrometer-scale pore space,such as the Bakken formation in the Williston Basin,North America.Because wettability reflects the interactions between rock surfaces and in-situ fluids,introduction of external fluids during drilling,completion,and enhanced oil recovery processes may alter wettability through chemical adsorption on rock surfaces.Therefore,accurate deter-mination of representative reservoir rock wettability,particularly its alteration caused by oil aging and surfactant adsorption,is extremely important in the Bakken production process.In this study,an advanced ultra-high-speed centrifuge was employed to measure capillary pressures and examine the wettability of Bakken cores by calculating the USBM(United States Bureau of Mines)wettability indices.Cores satu-rated and aged with formation brine or surfactant solutions were first injected with Bakken crude oil(i.e.,drainage process).Then the fluids in the cores were displaced by brine or surfactant solutions to obtain the imbibition curve first and then by crude oil to generate the drainage curve.The experimental results revealed that wettability alteration caused by surfactant adsorption on rock surfaces changed the rocks from water-wet to a more neutral-wet status.To investigate oil aging effect,oil and water distributions in-side Bakken core samples with and without oil aging were scanned by a synchrotron-based computed tomography(CT)scanner.After aging with crude oil for over two months,polar components from the oil adsorbed onto the rock surfaces and altered their wettability from strongly water wet to slightly water wet.Consequently,this wettability alteration contributed to oil and water redistribution and saturation change in reservoir cores,and ultimately the oil recovery performance.
Tight oil reservoir wettability wettability alteration surfactant aging effect
Peng Luo Sheng Li Petro Nakutnyy Kelvin D.Knorr
Energy Division,Saskatchewan Research Council,Regina,Saskatchewan,Canada,S4S7J7 Department of Chemical and Petroleum Engineering,University of Calgary,Calgary,Alberta,Canada,T2N1N4
国内会议
青岛
英文
71-80
2018-06-20（万方平台首次上网日期，不代表论文的发表时间）