Development of a New Chemical Formulation for Heavy Oil Viscosity Reduction and Displacement

Abstract

Abstract A novel polycyclic aromatic hydrocarbon (PAH) based water-soluble viscosity reducer (VR) formulation was designed to reduce heavy oil viscosity for enhancing heavy oil production by chemical flooding. The polyaromatic structures such as benzene, naphthalene, and pyrene units in the VR formulation target asphaltene and resin components in heavy crude oil via π-π interaction to hinder formation and self-assembly of asphaltene aggregates and to reduce the viscosity of heavy oil accordingly. Two main chemical components in the VR package were synthesized from the reaction between poly(ethylene glycol) and naphthalenemethanol or pyrenemethanol to yield amphiphilic molecules. The chemical structured were confirmed by 1H NMR spectra. Heavy oil displacement evaluations were conducted through two experimental setups – a coreflooding equipment and a visualized micromodel. In the coreflooding experiments, a commercially available benchmark VR (BVR) and the synthesized VR (SVR) solutions at the optimized concentrations were injected to displace the heavy oil saturated in carbonate cores. The residual oil distribution pattern after injection of chemical slug and the profile change of saturated oil during chemical flooding with the BVR and SVR were observed using a micromodel equipment. At 0.2 wt%, the SVR package formed oil-in-water (O/W) emulsions with heavy oil at an oil-to-water ratio of 7:3 and dramatically reduced the viscosity of heavy oil by 84% at 50 °C. Visualized micromodel displacement tests showed that the injected SVR solution gradually emulsified the heavy oil at the oil/water interface to form emulsion droplets, which were subsequently deformed and stretched into long and narrow emulsion strips to pass through the smaller pores and throats along with injected fluid, thus facilitating the mobility of heavy oil and enhancing the oil production eventually. Coreflooding testing indicated that the injected SVR fluid significantly decreased the injection pressure due to viscosity reduction of the heavy oil. The oil production was enhanced by around 11% on the basis of water flooding. As a comparison, the heavy oil production by injection of the BVR solution was improved by 8%. The performance of the SVR on heavy oil viscosity reduction and oil displacement was found more pronounced than the BVR. Therefore, the formulated SVR package exhibits a great potential in heavy oil production.