Role of Kaolinite Clay Minerals in Enhanced Oil Recovery by Low Salinity Water Injection

Both laboratory studies and field observations have confirmed increased oil recovery by low salinity water injection beyond that obtained by standard water injection. Whether extra oil is produced or not depends on certain reservoir conditions, and among them is the content of clay minerals. Kaolinite clay minerals have been reported to impact the low salinity enhanced oil recovery (EOR) potential, and they are believed to be involved in the initial wetting of sandstone reservoirs. In this work, the effect of temperature on the wetting of clay surfaces was studied. The adsorption of the polar organic base, quinoline, onto kaolinite clay minerals was investigated at ambient and high temperature (130 °C) versus pH. The experiments were performed using brines with different ionic compositions and salinities. A discussion of the effect of brine chemistry, pH, and temperature on quinoline adsorption was also included. Finally, wettability alteration processes by adsorption and desorption of polar organic molecules were used to explain the low salinity EOR effect observed in clay-containing sandstone reservoirs. The experimental results showed that the adsorption of quinoline onto kaolinite clay minerals was strongly dependent on pH at both ambient and at 130 °C. However, the adsorption at high temperature was reduced, which could affect the initial wetting of a sandstone reservoir system. The adsorption process was reversible by adjusting pH, and adsorption of quinoline was in general higher in a low salinity brine than in a high salinity brine. Thus, releasing basic polar crude oil components like quinoline from the kaolinite clay surface requires an increase in the brine pH, and not only a lowering of the salinity of the injection brine.

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