Low-Salinity Polymer Flooding: Improving Polymer Flooding Technical Feasibility and Economics by Using Low-Salinity Make-up Brine

Abstract

Polymer flooding is a mature EOR technique, which is successfully applied in both sandstone and carbonate reservoirs. In ongoing polymer projects, make-up brine is either formation water, sea water or any available water sources like deep or shallow aquifers. In this paper we focus on the use of low salinity water as the make-up brine. The objectives of combining low salinity flooding (LSF) with polymer flooding are three-fold: • Using low salinity brine reduces the amount of polymer required to obtain the target viscosity, which may lead to significant cost reduction. • Combining the benefit of low salinity flooding with polymer flooding leads to higher oil recovery over conventional polymer flooding. • Enhancing the elasticity of polymers by using low salinity brine which may lead to reduced Sorw and increased oil recovery. In addition to the objectives mentioned above, the use of a low-salinity make-up brine can give other benefits, such as better polymer stability especially at high temperatures), lower sensitivity to polymer shear degradation, lower polymer adsorption and lower scaling and souring tendency. The paper will present 1- Experimental procedures for investigating the potential benefits of low salinity polymer on both the required polymer concentration and the oil recovery. 2- Experimental results for several field cases 3- De-risking activities that were undertaken to mitigate any potential negative impact of using low salinity polymer, in the areas of clay swelling, polymer shear sensitivity, mixing and adsorption. The paper concludes that low-salinity polymer flooding can significantly improve existing and anticipated polymer flooding projects by reducing polymer volumes and/or increasing oil recovery. Low-salinity polymer flooding provides opportunities to apply polymer flooding in high-salinity and high-temperature reservoirs, for which polymer flooding with produced or formation water would be technically unfeasible or uneconomic.