A Polycyclic–Aromatic Hydrocarbon-Based Water-Soluble Formulation for Heavy Oil Viscosity Reduction and Oil Displacement
Shaohua Chen, Abdulkareem M. AlSofi, Jinxun Wang, Mohammad B. AlOtaibi
Abstract
A novel water-soluble viscosity reducer system based on polycyclic aromatic hydrocarbon (PAH) was designed and synthesized for heavy oil viscosity reduction and enhanced heavy oil production by oil displacement. This viscosity reducing agent (VRA) is composed of three components: the first one is a polyacrylamide (PAM) copolymer that contains hydrophobic pyrene groups, namely, P(Am- co -Py) (PAP); the second one is a nonionic surfactant, namely, n -dodecyl β- d -glucopyranoside (DDG); and the third component is a partially hydrolyzed PAM terpolymer that bears hydrophobic naphthalene groups, namely, P(Am- co -AMPS- co -VNp) (PAAN). The copolymer PAP was not soluble in high-salinity water (HSW). Addition of DDG solubilized PAP, and the yielded binary DDG/PAP solution was found to greatly decrease the interfacial tension (IFT) between heavy oil and water to an ultralow level and effectively reduce the heavy crude oil viscosity. In the presence of PAP, stable oil-in-water (O/W) emulsions were formed. The size of emulsion decreased and the size distribution narrowed with an increase in the PAP content. These observations were attributed to the strong interaction between the PAH molecules and heavy oil components via π–π stacking, hydrogen bonding, and hydrophobic association. Upon addition of the terpolymer PAAN, the solution viscosity of DDG/PAP/PAAN dramatically increased as a result of the formation of an extended polymeric network linked by intermolecular PAH junctions with strong hydrophobicity. The oil displacement tests conducted with a micromodel approach and a core-flooding equipment both indicated that the ternary VRA flooding significantly enhanced the heavy crude oil production based on the HSW flooding. The high effectiveness of heavy oil displacement by the ternary VRA system resulted from an enhanced volumetric sweep efficiency and a remarkable IFT reduction. This study investigated the synergy between the PAH-based polymers and the surfactant and developed a potential strategy in the design and formulation of high-performance VRAs for heavy oil viscosity reduction and heavy oil displacement.