Best Surfactant for EOR Polymer Injectivity

Abstract

Synthetic polymers in the emulsion form have been exploited for enhanced oil recovery applications especially in harsh environments for instance offshore or remote onshore locations. Polymer solutions can be prepared on-the-fly using saline make-up water like formation water or sea water. Use of an inverter surfactant accelerates the inversion of the polymer emulsion. For this study two highly efficient inverter surfactants at different price level were selected and their impact on the performance of an acrylamide-based emulsion copolymer was investigated. Polymer solutions prepared with the inverter surfactants S1 and S2 at different concentrations and conditioned by defined shear treatment were characterized by rheology, filter tests and injectivity behavior in sand packs. Significant impact of inverter surfactant on rheological properties and especially on injectivity performance is demonstrated. Viscosities of polymer solutions prepared with surfactant S1 are slightly higher (than viscosities with surfactant S2) and decrease with increasing surfactant concentration at constant polymer content. Besides, RRF values as a measure for injectivity behavior strongly decrease at ascending surfactant content. More intense conditioning leads to favorable injectivity of an otherwise plugging polymer solution. At lower concentrations surfactant S1 seems to adversely interact with the polymer and form polymer-surfactant complexes which are retained in the sand pack during injection. For surfactant S2 viscosities of polymer solutions are independent of surfactant concentration and RRF values are low even at low surfactant concentration. This surfactant ensures good injectivities over a broad range of conditions. Being the economically more favorable surfactant it adds value to polymer flooding projects.