Thermodynamic modeling of the temperature impact on low-salinity waterflooding performance in sandstones

Abstract

Low-salinity waterflooding has emerged as an innovative technique to improve oil recovery. Extensive research has been devoted to providing a better understanding of the mechanisms involved and to optimize its performance. Among those mechanisms, multi-component ion exchange mechanism explains the coordination of surface complexes in a way that highlights the essence of low-salinity waterflooding. However, the impact of temperature on low-salinity waterflooding is still poorly understood. We used surface complexation modeling to study both the oil/brine and mineral/brine interfaces up to a temperature of 150 ∘C. Given the heterogeneity of the oil interface, we studied three oil interfaces with varying total base number to total acid number ratios. It was determined that temperature is a critical factor in estimating the performance of low-salinity waterflooding. While temperature reduces the pH range at which low-salinity waterflooding yields positive effect for basic oil, it shifts the pH window at which low-salinity waterflooding has potentially negative results to lower pH values for neutral oil. In addition, the temperature magnifies the ability of low-salinity waterflooding to enhance surface potential. Our results support the need for conducting experimental work at the relevant reservoir temperature to evaluate the performance of low-salinity waterflooding.