Stress shadow effect and fracture evolution mechanism of hydraulic fracturing in horizontal well of Shoushan No.1 Mine
Hydraulic fracturing is a key technology for improving the permeability of coal seam and increasing the production of coalbed methane.It can effectively create fracture network,increase the area of gas seepage channel.However,with the increase of coal seam mining depth,coalbed methane development faces challenges such as deep burial,complex occurrence environment,dense rock mass,strong heterogeneity,and high development difficulty.The design of horizontal well cluster scheme has become the key to solving this problem.Based on the physical properties of a coal seam in a certain working face of Shoushan No.1 Mine,a geomechanical model was constructed using three-dimensional finite element stress simulation technology.The fracturing process technical indicators such as reser-voir fracturing displacement,liquid volume,and liquid viscosity were designed to study the influence of different stress differences on the hydraulic fracturing radius.Using this model and single factor control method,the development form and effective radius of fractures un-der different cluster spacings were studied and analyzed.The results showed that the effective radius of fracture was verified by hydraulic fracturing engineering test and was in agreement with the numerical simulation analysis results.With the increase of the difference coef-ficient of ground stress,the main fracture of hydraulic fracture gradually migrated,and the smaller the horizontal stress difference was,the more complex the compression fracturing network formed.With the increase of the cluster spacing,the intercluster stress interference of fractures decreased,and the propagation of cracks became more uniform.
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