Preparation and evaluation of hydroxyethyl cellulose-based functional polymer for highly efficient utilization of heavy oil under the harsh reservoir environments

Abstract

Emulsification viscosity reduction and subsequent demulsification are effective strategies to improve the utilization rate of heavy oil. However, traditional surfactants are challenged by unsatisfactory salt tolerance, inadequate stability in emulsification, difficulty in demulsification and pollution problem of oily wastewater discharge. To realize the feasibility and environment-friendliness of heavy oil utilization in the harsh reservoir environments, we designed a functional polymer and conducted a comprehensive evaluation using heavy oil samples from Chenping oil well in Shengli Oilfield. It was synthesized by grafting two hydrophobic monomers, lauryl methacrylate (LMA) and N, N-Diethylaminomethyl methacrylate (DEAEMA), onto the hydrophilia hydroxyethyl cellulose (HEC) by free-radical polymerization. The viscosity reduction rate can reach 99.57 % even under the high salinity of 26,050 mg/L. The stable oil-in-water (O/W) emulsion can be maintained for >48 h, satisfying the actual requirements for heavy oil recovery. Moreover, the emulsion can be completely demulsified in a CO₂ atmosphere within 30 min, suggesting its satisfactory demulsification performance. Our study achieved the one-step transformation of heavy oil emulsion between emulsification and demulsification, which provides a green bio-based material and an ingenious strategy for enhanced oil recovery and other chemical engineering applications including oil/water separation.

Keywords: Emulsification and demulsification; Heavy oil; Hydroxyethyl cellulose; Salt tolerance; pH–responsive.