Numerical-simulation-based criteria for well and layer selection in fracturing-flooding of offshore low-permeability reservoirs

To address the lack of clear criteria for well and layer selection in the offshore applications of fracturing-flooding technology, this study develops a refined numerical simulation method to quantitatively characterize the oil enhancement mechanisms associated with high-pressure fracture-induced permeability improvement, surfactant-assisted oil displacement, and soak-imbibition processes. Based on numerical simulations, selection criteria for wells and layers suitable for fracturing-flooding are systematically investigated, and the relative influence of key selection indicators on incremental oil production is analyzed. Results show that the oil-saturation condition play a more critical role than original reserves and physical properties of the reservoir in well and layer selection. Specifically, a pressure maintenance level greater than 0.4 and an oil saturation of exceeding 40% are identified as the lower limits for candidate wells and layers. After fracturing-flooding treatment of the optimized target wells and layers, the initial incremental oil production reaches 50 m³/d, and the productivity index of the target layer increases from 1.2 m³/(d·MPa) to 9.2 m³/(d·MPa), and the cumulative incremental oil production reaches 1.01 × 10⁴ m³ within six months, indicating that the fracturing-flooding performance meets the design requirements. Field practice shows that the proposed refined numerical simulation approach—which incorporates formation energy replenishment, pore and permeability enhancement, pressure-induced fracturing, surfactant-assisted washing oil, and imbibition displacement mechanisms—together with the established well and layer selection criteria, provides effective technical support for fracturing-flooding operations in offshore low-permeability reservoirs.