Study on near-wellbore fracture geometry in perforated horizontal wells with discrete lattice method

• The near-wellbore fracture propagation behavior considering the perforation tunnel is simulated based on the discrete lattice model. • The fracture complexity and the initiation degree of different perforation tunnels are quantified. • A solution for multi-cluster initiation based on flow distribution mechanism in horizontal wells has been proposed. The near-wellbore hydraulic fracture geometry is governed by the combined effects of perforation arrangement, wellbore trajectory, in-situ stress field, and fluid injection parameters, which directly affects cluster fluid efficiency and proppant transport, ultimately determining the success of hydraulic fracturing operations. In this study, a three-dimensional fracturing numerical model based on discrete lattice method was established to simulate the near-wellbore fractures geometry under various engineering and geological conditions. Quantitative analysis was conducted on the variation coefficient and complexity of the fracture morphology. The results indicate that spiral perforation promotes the merging of multiple branch fractures, forming a dominant planar fracture characterized by low fractal dimension, with a 90° phasing angle generating more complex fracture morphology than a 60° phasing angle. As wellbore azimuth shifts from the minimum to the maximum horizontal principal stress direction, the fracture morphology evolves from quasi-two-dimensional to complex three-dimensional structures, accompanied by an increase in fractal dimension. The fracture variation coefficient generally rises with increasing stress difference, indicates that certain perforations act as preferred pathways for near-wellbore fracture propagation, revealing the inherent fluid uneven distribution mechanism during hydraulic fracturing. Under this mechanism, some perforations are further eroded and expanded due to the continuous flow of sand-carrying fluid, and temporary plugging balls are needed to plug these dominant channels, especially in wells with high stress or obvious deviation from the direction of principal stress, and larger plugging balls are required. The research results are helpful to optimize the construction parameters in the process of hydraulic fracturing.