Impacts of Natural Fractures on Propagation Behaviors of Hydraulic Fractures under Different Pulse Pressures

Pulse hydraulic fracturing can enhance the productivity of oil and gas wells in low permeability formations. During pulse hydraulic fracturing, natural fractures significantly influence the propagation path of hydraulic fractures and the fracturing effects. The impact mechanism of natural fractures on the propagation of hydraulic fractures under different pulse pressures remains unclear. A combination of experimental, theoretical, and numerical approaches is employed to examine the propagation characteristics and stress distributions of hydraulic fractures under different pulse pressures and natural fractures. Stress fields around the tips of hydraulic fractures, considering the influence of natural fractures, are established. Natural fractures exert a significant influence on the stress field at the tips of hydraulic fractures, either promoting or hindering their propagation and altering the propagation path of the hydraulic fractures in rocks. Under low pulse loading stress ratios (0.6, 0.75), natural fractures have a considerable effect on the stress distribution and the propagation path of hydraulic fractures. As pulse pressures rise to 0.9, the influence of natural fractures on the propagation of hydraulic fractures diminishes, resulting in hydraulic fractures extending along the direction of the stress difference. Pulse pressures and natural fractures influence fracturing effects on rocks. Under low pulse loading stress ratios (0.6, 0.75), a greater number of hydraulic fractures are generated in rocks and propagate along the natural fractures, enhancing the fracturing effects. When the pulse pressure increases to 0.9, high pulse pressures cause stress concentration in the direction of stress difference, which leads to less damage and a decrease in the number of hydraulic fractures, and hydraulic fractures are prone to penetrating natural fractures at larger azimuth angles (90°). The research results can reveal the influence mechanism of natural fractures on the propagation paths of hydraulic fractures under different pulse pressures and guide the design of pulse hydraulic fracturing.