Abstract
Recently, we proposed a chemical mechanism for the role of clay in sandstone during low salinity water (LS water) flooding using acetate to simulate the oil-bound carboxylic acids with the reservoir (Al-Saedi and Brady 2018). In this study, we propose to quantify the control of mineral composition and water chemistry on water/rock interactions by using oil during low salinity waterflooding of spatially heterogeneous sandstone porous media. A sandstone core and free-clay sand core were prepared in chromatography columns and were water flooded sequentially with high-low salinity water at the reservoir temperature of 90ºC. Brine with high salinity (100,000) ppm was injected to simulate formation water. Then, Inflow LS water (1100) ppm. One of the columns only contains quartz, to investigate the role of the clay in the mechanism of LS water enhanced oil recovery (EOR). The other columns contained quartz and different quantities of clays. The results showed that during flooding, the free-clay column with LS water the oil recovery from the quartz column was as great as that of the clay-containing cores. On the other hand, our previous investigation showed a noteworthy desorption of Ca2+ from the free-clay core surface. That indicates further RCOO- detachment in the absence of clay. The pH also increased significantly during LS water flooding for the free-clay column.
