Eliminate the role of clay in sandstone: EOR low salinity water flooding

Abstract

Abstract Low-salinity (LS) water flooding mechanism enhanced oil recovery (EOR) method in sandstone has been extensively debated in the literature. Many mechanisms have been proposed, but these proposed mechanisms remain a topic of debate. In this study, we propose to quantify control of mineral composition and water chemistry on water/rock interactions and wettability change during low-salinity waterflooding of spatially heterogeneous sandstone porous media. We intended to identify the dominant process of wettability alteration through considering water–rock interaction mechanisms containing/non-containing clays. Water chemistry partially determines the dominant wettability alteration. This includes salinity, type of ions, and possibly pH. Sandstone core and free clay sand core were prepared in chromatography columns and were water flooded with high/low/high-salinity water at different temperatures. Brine with high salinity 100,000 ppm was injected to simulate formation water, then, inflow low-salinity water 1100 ppm at different temperatures. Concentrations of Ca2+ and CH3COO− and pH were recorded. The core contains quartz only, to investigate the role of clay in the mechanism of smart water EOR. The results proved that during flooding the free clay core by low-salinity water the carboxylic acid detached from the sand, albeit not as great as that of the clay-containing cores. On the other hand, ICP-OES showed a noteworthy desorption of Ca2+ from the free clay core surface. That indicates further RCOO− recovery in the absence of clay. It has been observed that during flooding by LS water, the pH increased significantly. Also, as the temperature increased the pH of the LS water decreased and amount of Ca2+ decreased in the effluent. This work presents the results of forced imbibition experiments to examine the effect of clay in sandstone during LS flooding EOR.

Keywords

• LSWF
• Cation desorption
• Geochemistry
• EOR