Fabrication of surfactant-biopolymer combined system with dual viscosity reduction and mobility controllability for heavy oil reservoirs

Abstract

Surfactant-polymer (SP) combined systems have been proven to be efficient for enhancing heavy oil recovery through in-situ emulsification and water thickening mechanisms due to their dual viscosity reduction and mobility controllability. In this study, 0.1 wt% anionic surfactant (fatty alcohol polyoxyethylene ether sulfate, SC) and 0.05 wt% biopolymer (xanthan gum, XG) were combined to develop a novel SP system (SC-XG). The emulsification properties including stability, droplet morphology and size distribution, as well as oil–water interfacial tension (IFT), rheology were systematically investigated. The results showed that the addition of XG into SC systems could obviously decrease the viscosity ratio of oil to displaced water (μo/μd) to 1.42 and simultaneously maintain the high viscosity reduction rate at 94.03 %, which is beneficial for decreasing the mobility ratio of water to oil (M). Besides, the emulsion prepared by SC-XG displayed stronger stability and smaller droplet size compared to those of SC after aging 2 h. Although the addition of XG into SC system could slightly increase the oil–water IFT, the viscosity and viscoelasticity were significantly strengthened and displayed main contributions to the enhancement of emulsion stability. Finally, the sand-pack flooding experiments showed that the optimum SC-XG system could enhance the heavy oil recovery by 20.20 % after brine flooding process, which exhibited dual viscosity reduction and mobility controllability. This study demonstrates the facile design and potential applications of SP system for heavy oil reservoirs.