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Numerical Simulation Study on the Regularity of the CIS Bedding Hydraulic Fracturing based on the 3D Penny-Shape Model

: In view of poor permeability of coal seam and soft coal quality in China's coal mining area, a point hydraulic fracturing method suitable for the occurrence characteristics of coal seam is put forward based on the characteristics of coal seam hydraulic fracturing and the field practical experience of coal seam hydraulic fracturing for many years. A theoretical and mathematical model of hydraulic fracturing is established. Based on the large-scale finite element software ABAQUS, numerical simulation of two dimensional and three dimensional hydraulic fracturing is carried out, and the fracture propagation law and its parameter sensitivity of coal seam point hydraulic fracturing are simulated and analyzed. The results show that when multi point synchronous hydraulic fracturing on the same layer borehole is carried out, there will be a certain coherence effect between fracture cracks when the interval between fracturing points is small. In the same fracturing time, the minimum effective stress in the coal body between the cracks will be reduced by about 10% when the gap between the cracks increase by 25%. We can use the fluctuation of effective stress field around fracture before and after fracturing as a discriminant index for effective radius of hydraulic fracturing. In general, it is advisable to have 10%~20% amplitude of effective stress field before and after fracturing.