Research of Polymeric Surfactant as Multifunctional Monocomponent Oil Displacement Agent in EOR

SP (Surfactant-Polymer) flooding is one of the most common methods in Enhance Oil Recovery (EOR). However, chromatographic separation underground limits its efficiency due to the enormous difference in molecular size between polymer and surfactant. A single-component oil displacement agent, polymeric surfactant (PolyS), was studied to solve the chromatographic separation. Properties were investigated under the reservoir conditions, including viscosity, interfacial activity, injectivity, adsorption, and core flooding. With the increase of the active functional group content, the viscosity decreased, while the oil-water interfacial activity increased. The viscosity of PolyS was higher than 10mPa∙s, and interfacial tension (IFT) was lower than 3×10-2 mN/m at 2500 mg/L PolyS in the brine with a salinity of 66560 mg/L at 72°C. The middle phase emulsion was formed when mixing crude oil and PolyS solution, indicating that PolyS had better capability to emulsify crude oil than commercial polyacrylamide (PAM). Furthermore, the adsorption amount of PolyS on silica with diameter of 100-150 μm was 1.16 mg/m2. PolyS can be easily injected into sandpack with different permeabilities from 300 mD to 1000 mD. The oil displacement results showed that an improved oil recovery of 26.15% OOIP was achieved with an injection of 0.3 PV PolyS solution containing a 2.04 mol% active functional group, which had both low IFT and high viscosity. As a comparison, only 20% OOIP was obtained for commercial PAM.