Numerical study on infill fracturing of mature wells under free-drainage boundary conditions

Infill fracturing of mature wells involves re-fracturing within previously stimulated clusters, targeting unstimulated regions of the parent well's fracture network. This strategy sustainably enhances hydrocarbon recovery from depleted reservoirs without the environmental footprint of new drilling. Establishing a numerical simulation model for this process is essential for optimization. In this study, a numerical model for mature well infill fracturing was developed based on the extended finite element method and a free-drainage boundary module. The results indicate that prior production from mature wells primarily affects the fracture length and curvature in the infill wells. As infill fracturing-induced fractures propagate toward the far-field region, they are significantly influenced by the heterogeneous pore pressure distribution in the reservoir. This leads to a pronounced increase in fracture curvature. Compared with conventional fracturing, the curvature of fractures under infill fracturing is approximately 30% higher within the same simulation time, while the fracture length is notably shorter. With the increase in production time, fractures in infill wells tend to exhibit greater tortuosity. This enhanced complexity allows for more effective contact between the fractures and the reservoir, thereby improving the production potential of the infill wells to some extent.