Synthesis and evaluation of multi-aromatic ring copolymer as viscosity reducer for enhancing heavy oil recovery

Functional polymers play an increasingly significant role in oilfield development. Herein, the side-chain functionalized copolymer APVR was fabricated using functional monomer 2,6-bis(1-methyl-1H-benzo[d]imidazol-2yl)pyridin-4-yl-methacrylate (BMP) with similar structure to the heavy components in crude oil and dihexadecanol maleate (DHM) with long alkyl chain. 1H NMR, FTIR and TGA analyses were employed to characterize the structure of APVR. Simultaneously, viscosity reduction performance and heavy oil displacement performance of APVR were also studied. For comparison, the copolymers P(AAB), P(AAD) and P(AA) containing one functional monomer and without functional monomer were also synthesized. The results showed that when the copolymer concentration is 2000 mg/L, the viscosity reduction rate (VRR) of APVR, P(AAB), P(AAD) and P (AA) is 93.1%, 84.3%, 82.4% and 65.4%, respectively. Furthermore, compared with water flooding, their ultimate recovery of heavy oil increased by 18.34%, 13.78%, 13.18% and 9.93%. The interaction mechanisms between APVR and heavy oil were studied using XRD, SEM, and molecular dynamic simulation. Due to their unique structure, BMP and DHM were able to permeate into the molecule structures of heavy oil, reducing the intermolecular forces between heavy components by forming supramolecular forces with asphaltene. Thus, they led to the loose stacking of asphaltene aggregates, making it easier for APVR to emulsify oil droplets due to its amphiphilic property. The copolymer APVR shows promising potential for reducing heavy oil viscosity and may have broad application prospects in heavy oil exploitation.