Enhanced Heavy Oil Mobility Control and Recovery Through Synergistic Integration of Gas-Chemical Stimulation and Near-Wellbore Reconstruction
Abstract
Heavy oil’s high viscosity and poor mobility present significant extraction challenges. Under dual-carbon objectives, non-thermal recovery technologies are increasingly prioritized. Addressing heavy oil mobility issues in porous media under non-thermal conditions and enhancing recovery efficiency are critical for deep heavy oil, water-scarce, and offshore reservoirs. Integrating gas viscosity reduction, chemical viscosity reduction, and near-wellbore reconstruction aligns with current technological needs; however, the effectiveness and reliability of such synergistic approaches require further validation. Laboratory experiments optimized viscosity reduction techniques using target oilfield crude samples, focusing on viscosity reducer type, concentration, and dosage selection. Numerical simulations refined gas viscosity reduction parameters (e.g., gas type, injection volume) to improve sweep efficiency. Near-wellbore stimulation parameters, particularly fracture radius, were optimized via numerical modeling to maximize production. A novel integrated technology was developed, combining pre-injection of CO2, hybrid injection of viscosity reducers, and propellant stimulation (e.g., PST/WST). Key findings include: (1) Chemical viscosity reducers achieved >80% viscosity reduction at 5% concentration, with an injection intensity of 2.4-10.2 tonnes per meter (t/m); (2) Optimized CO2 injection intensity ranged from 5.6 to 30.9 t/m; (3) Precision propellant stimulation generated effective fracture radii of 5-15 m. This technology was successfully applied in China’s Shengli and Tuha oilfields. For a representative well (Depth: 3,000 m; Viscosity @122°F: 280,000 cP; Permeability: 1,700 mD; Porosity:18%), numerical simulations predicted an oil production rate of 107-220 barrels per day (bbl/d) and cumulative cycle production of ~18,869 bbl. This work provides a novel pathway for developing deep heavy oil, water-scarce, and offshore reservoirs. The integrated stimulation and viscosity reduction enable initial reservoir activation, establishing the foundation for subsequent multi-cycle huff-and-puff operations. These operations can transition to displacement or gravity drainage processes for sustained high-efficiency recovery.