Effects of surfactant-polymer formulation and salinities variation towards oil recovery

Abstract

Surfactant-Polymer (SP) formulation is a crucial part when dealing with SP flooding. Different formulations using different types and concentrations of combination of surfactant and polymer result in different interfacial tension (IFT) and viscosity obtained and it will affect the amount of oil recovered. Salinity also affects the efficiency of SP flooding. High salinity causes polymer viscosity reduction and optimal salinity results in low IFT. This research is conducted to design SP formulation, select an optimum SP formulation by core flooding tests and to determine the effect of salinity (NaCl) variations towards optimum SP formulation. Nine different SP formulations in constant salinity are designed by using different concentrations of Hydrolized Polyacrylamide (HPAM) and anionic surfactant (Alpha Olefin Sulfonate-AOS). The formulations were characterized in terms of viscosity and IFT. Artificial heterogeneous porous media were used in core flooding tests and only six SP formulations with lowest IFT value were tested. Three different salinities were used for optimum SP formulation with maximum incremental oil recovery after water flood to determine the effects of salinities on polymer viscosity, surfactant IFT, incremental oil recovery after water-flood and also phase behavior. For combination of HPAM and AOS in SP flooding, IFT was only affected by the concentration of surfactant used whereas viscosity is solely dependent on polymer concentration. Core flooding tests performed in heterogeneous porous media shows that there exist an optimum polymer viscosity and surfactant IFT in SP flooding which can maximize incremental oil recovery and increasing in salinity also results in poor incremental oil recovery.