Simulation Study of Characteristics of Hydraulic Fracturing Propagation of Low Permeability Coal Seam

Based on the coal deformation model, hydraulic pressure descent model in fracture, fracture propagation model and its growth criterion, the mathematical model of hydraulic fracturing of low permeability coal seam are established and the characteristics of hydraulic fracturing propagation under influencing factors such as injection pressure, elastic modulus of coal and fluid viscosity are studied. The results show that fracture length presents a linear increase and widest width increases as an exponent function with the increase of injection pressure and the ability of making fracture width is larger than fracture length during late fracturing; with the increase of Young's modulus of coal seam, fracture length and widest width decrease linearly; besides, fracture length decreases as an exponent function and widest width increases with the increase of fracturing fluid viscosity but its influencing action reduces when the fluid viscosity reaches a certain extent. The obtained conclusions provide a guiding role for the optimization of operation parameters of field hydraulic fracturing of low permeability coal seam.