Comprehensive Displacement System Utilizing Dispersed Particle Gels Coupling Viscosity Reduction and Breakthrough Channel Control for Heavy Oil Cold Production

Chemical flooding cold production technology is an important replacement method for the efficient development of heavy oil reservoirs after thermal recovery. The key challenge in achieving high oil recovery efficiency with this technology is addressing the low contact efficiency between the viscosity-reducers and heavy oil, caused by the migration of the reducer along breakthrough channels. In this study, a dispersed particle gel comprehensive displacement system (DPG-CDS) for the cold production of heavy oil is proposed. This system utilizes a composite of dispersed particle gel (DPG) profile control agents and viscosity-reducers, achieving both the stable plugging of breakthrough channels and the synergistic effect of effective viscosity reduction and oil displacement. The composition of DPG-CDS is optimized based on emulsion viscosity reduction efficiency, oil–water interfacial tension, system viscosity, and ζ-potential. A systematic investigation of the basic characteristics of DPG-CDS was conducted. Under simulated reservoir conditions, after aging, the particle size of DPG-CDS increased from 2.12 to 57.63 μm, and the system viscosity decreased from 9.46 to 5.68 mPa·s, demonstrating excellent particle aggregation ability. When the emulsion water content exceeded 30%, the viscosity reduction rates for three heavy oil samples exceeded 95%, and the viscosity reduction rate after aging decreased by no more than 2%. DPG-CDS exhibited excellent injection performance in cores with different permeabilities, with a core plugging efficiency exceeding 85%. In a dual-core model with significant permeability contrast, the profile improvement effect was significant, achieving a profile improvement rate of up to 89.71%. Low-field NMR was used to investigate the displacement modes of DPG-CDS in multiscale pores. The results showed that DPG-CDS can effectively plug high-permeability channels formed by water flooding and increase the heavy oil recovery in Nano-Micron pores, with a final cumulative recovery rate of 64.48%. The recovery increment in cores with different permeabilities was over 20%, with a particularly better oil displacement effect in the Nano-Micron pores of low-permeability cores. In dual-layer heterogeneous core models, DPG-CDS effectively plugged breakthrough channels and induced flow diversion, synergistically enhancing oil washing efficiency. The enhanced oil recovery (EOR) effect was more significant in reservoirs with a larger permeability ratio (3.03), with a recovery rate of 67.4%. The DPG-CDS system developed in this study demonstrates significant potential for increasing production in heavy oil cold production, providing a new perspective for the development of chemical composite flooding technology in cold heavy oil recovery.