Performance Evaluation of Hybrid Thermal-Solvent Injection in a Post-CHOPS Reservoir With Consideration of Wormhole Network

In this paper, techniques have been developed to evaluate performance of thermal, solvents, and hybrid thermal-solvent processes in a post-CHOPS reservoir with consideration of wormhole network. With the experimentally determined properties of injected gases and reservoir fluids, history matching is accomplished for the reservoir geological model conditioned to the fluid and sand production profiles together with pressure. Meanwhile, the wormhole network is characterized with the newly developed pressure-gradient-based (PGB) sand failure criterion. Once the history matching is completed, the calibrated reservoir geological model is then employed to evaluate performance of thermal, solvents, and hybrid thermal-solvent processes under various conditions. It is found that huff-n-puff processes have a very good performance on enhancing oil recovery when wormhole network is fully generated and propagated. Among all solvent-based methods, pure CO₂ huff-n-puff process shows a better performance than flue gas, while the addition of alkane solvents leads to a higher oil recovery compared with CO₂ only method. Since the addition of C₃H₈ and n-C₄H₁₀ will significantly decrease the heavy oil viscosity and enhance the swelling factor, all hybrid thermal-solvent injection achieves high oil recovery by taking the advantage of both hot steam and solvents injection.