Effect of Make-Up Water Salinity on Polymer Adsorption in Carbonate Reservoirs

Abstract

Abstract Application of polymer flooding in carbonate reservoirs still faces significant challenges, including polymer degradation, injectivity, and retention. With the increased awareness of the importance of water chemistry, this paper investigates the effect of make-up water composition on an ATBS (Acrylamido-Tertiary-Butyl Sulfonate)-based polymer performance focusing on polymer-rock interactions. Comprehensive rheological studies at ambient (25 °C) and reservoir (90 °C) temperatures were conducted on the potential ATBS-based polymer to study the effect of water chemistry. Different make-up water recipes were used with salinity ranging from 400 to 167,000 ppm. Further, static and dynamic adsorption studies were conducted at ambient temperature (25 °C) to investigate polymer performance and polymer-rock interactions. The water recipes with salinity less than 10,000 ppm showed better performance in terms of viscosity enhancement and reduced polymer adsorption. By reducing the overall salinity of the make-up water, the required polymer concentration to achieve a specific target polymer viscosity was decreased by 50-70%. The polymer solution in the diluted brine showed lowered adsorption value of 25 μg/g-rock as opposed to the high salinity formation water (167,000 ppm) and seawater (43,000 ppm) with adsorption levels between 47-56 μg/g-rock. Moreover, a reduction in polymer adsorption was further observed in the presence of crude oil. This research highlights the importance of make-up water salinity on polymer performance and concludes that low salinity water injection enhances polymer flooding performance and reduces polymer adsorption.