Enhanced oil recovery of low salinity water flooding in sandstone and the role of clay

Sandstone core and free clay sandstone core were prepared in chromatography columns, and core flooding experiments were done on them to determine the EOR mechanisms of low salinity water flooding and analyze the effect of clay on recovery factor. First, brine with high salinity of 100 000 mg/L was injected to simulate formation water. Then, low salinity water of 1 000 mg/L was injected at different temperatures. Concentrations of Ca 2+ and CH 3 COO - and pH of the fluid flowing out of the chromatography column were recorded. The study showed that during flooding of the free clay core with low salinity water, the carboxylic acid detached from the sand, albeit not as great as that of the clay-containing cores. It showed a noteworthy desorption of Ca 2+ from the free clay core surface, which indicated that low salinity water flooding got high recovery in sandstone reservoirs without clay. Compared with high salinity water flooding, in the low salinity water flooding, the pH of produced fluid increased significantly; as the temperature increased, the pH and Ca 2+ concentration of the produced fluid decreased; and the hydrophilic property of the sandstone was stronger. © 2018, The Editorial Board of Petroleum Exploration and Development. All right reserved.