Complex Well-Interferences During Multi-Wells Hydraulic Fracturing in Sichuan Deep Shale Gas Reservoir

As the first deep shale gas block in China, Weirong gas shale is characterized with complicated geological structures, heterogeneous natural fractures distribution, high geo-stress and high horizontal stress difference. Multi types of frac-hits were monitored in under the well spacing of 400 m, including frac-hit to the adjacent well, frac-hit to the multi-wells in same pad, frac-hit to the wells in different pads with the distance of over 1000 m. To investigate the mechanism of these frac-hits, an integrated DFN-FEM numerical model is built for multi-wells hydraulic fracturing. Involved with the field data, some conclusions can be drawn based on the simulation hydraulic fractures and induced stresses: (1) Due to the strong inducing effect of discontinuities, the high density of natural fractures or large size fault plays the main role on multi-wells frac-hit; (2) the frac-hit is enhanced with a larger induced stress range under a smaller natural fracture stiff-ness; (3) a stronger frac-hit can be detected with the shale of a lower cohesion and internal friction angle; (4) different fracturing sequences among multi wells present different induced stress among wells, the staggered fracturing sequence can highly weaken the frac-hit (5) the different injection parameters (injection intensity, injection rate, fluid viscosity, etc) mainly affect the frac-hit magnitude, merely change the frac-hit type.