Research on the Influencing Factors during Hydraulic Fracturing Assisted Oil Displacement Process in Offshore Low Permeability Oilfields and the Quantitative Characterization of Fracture Propagation and Liquid Infiltration

Hydraulic fracturing assisted oil displacement (HFAOD) can improve the productivity of offshore low-permeability reservoirs, but challenges such as rapid productivity decline, difficulty in controlling fracture height, and unclear influence of geological and operational factors on key parameters of HFAOD persist. This study establishes a fluid-solid coupling model for HFAOD and verifies its accuracy with field data. It clarifies laws of HFAOD fracture propagation and fluid infiltration, conducts sensitivity analyses to identify dominant factors affecting fracture propagation and fluid infiltration, and achieves quantitative characterization and rapid prediction of fracture half-length and infiltration radius. The results indicate that the HFAOD fluid undergoes simultaneous infiltration during fracture propagation. In the initial stage of HFAOD, the fluid primarily contributes to fracture creation with limited infiltration, while in the middle to late stages, fracture propagation diminishes and the infiltration radius expands significantly. The dominant controlling factors affecting HFAOD fracture propagation are reservoir thickness and cumulative injection volume, the dominant controlling factors affecting HFAOD fluid infiltration are permeability and formation pressure coefficient before HFAOD, which should be given special attention on site. This study quantifies the relationships between HFAOD key parameters (fracture half-length and infiltration radius) and their dominant controlling factors and establishes a mathematical model for rapid prediction of these parameters. The research results provide a theoretical basis for optimizing HFAOD designs in offshore low permeability reservoirs.