Hyperbranched Copolymer as a Viscosity Reducer for Offshore Heavy Oil: From Optimization to Application

This paper discussed the selection of functional monomers and optimal synthesis conditions for hyperbranched copolymer named as HVR, a novel polymer flooding chemical, intended to enhance offshore heavy oil recovery. The potential application of HVR as a polymer for oil displacement was also evaluated. Through experiments and molecular simulations, functional monomers AOS and OP-10 for Bohai heavy oil were screened out due to their high viscosity reduction rates for oil, both above 90%. Moreover, the interaction energy calculation results suggested that AOS and OP-10 were more likely to spontaneously disperse asphaltene aggregation. Furthermore, the influence of various factors on the synthesis of HVR was discussed using orthogonal design, and optimal synthesis conditions were determined. The optimal conditions for HVR synthesis are as follows: polymerization concentration of 30 wt %, initiator dosage of 1 wt %, initiation temperature of 50 °C, and system pH of 7; the sum of OP-10 and AOS accounts for 29.9 wt %, with a molar ratio of 1:1; the total amount of AM and AA accounts for 79.9 wt %, with a mole ratio of 6.5:3.5; and 3.0 G PAMAM accounts for 0.2 wt %. Moreover, HVR demonstrated good mobility control capacity and improved the recovery of heavy oil significantly in core flooding tests. Injecting a slug of 0.3 PV of HVR led to the additional recovery of 21.96 and 16.04% for oil viscosities of 350 and 500 cP, respectively. Notably, HVR’s additional recovery was over 7% higher than that of conventional hydrophobically associating polymer. These findings highlight the potential of HVR as a novel polymer to enhance the heavy oil recovery.