Systematically Optimized Surfactant Formulation and Injection Design to Reduce Chemical while Maintaining Performance

Abstract

Abstract Chemical costs dominate surfactant enhanced oil recovery (EOR) processes. A measure of chemical usage is the pore volume of chemical injected multiplied by the concentration of the chemical in the formulation (PV*C). Recent developments have reduced PV*C to about 30 units for conventional surfactant processes and to about 10 units for ASP processes. Our goal was to demonstrate high oil recovery using conventional surfactant processes at PV*C of 10 units. Under these conditions surfactant polymer flooding becomes just as viable an alternative for oil recovery as the more complex ASP processes. In this paper, we conducted several phase behavior experiments with the goal of minimizing microemulsion viscosity and maximizing oil solubilization ratios. In addition, we focused on maintaining aqueous stability of both the surfactant slug and dilutions with polymer chase fluids. Both surfactant and co-solvent compositions were optimized to achieve low microemulsion viscosity. The microemulsion viscosity was also measured using three-phase relative permeability experiments. Once an appropriately low microemulsion viscosity was achieved, a series of corefloods at different PV*C units of surfactant were conducted in Bentheimer sandstone. Our baseline formulation included 2 wt% surfactant and 2.8 wt% co-solvent and recovered more than 95% oil in a surrogate Bentheimer coreflood using 30 units of surfactant. The existing surfactant formulation was optimized to match the new crude oil sample and it also recovered more than 95% oil in a Bentheimer coreflood using 30 units of surfactant. By incorporating large hydrophobe surfactants, we achieved good phase behavior with 1.25% surfactant and 2% co-solvent. The optimized formulation recovered 98% oil with 20 units and 91% with 10 units of surfactant, which translated into a retention of <0.1 mg/g of surfactant. These results indicate that high-performance surfactant formulations have the potential to significantly reduce chemical cost and compete with conventional SP processes in terms of PV*C. Consequently, we illustrate the ability of recovering more than 90% oil with only 10 units of surfactant in conventional surfactant-polymer flooding with high performance surfactants. Such an approach can potentially compete with ASP processes and allow for rapid deployment due to reduced complexity.