Physical simutation experiment investigation on hydraulic fracture propagation in high-dip coal seam

In order to study the hydraulic fracture geometry in high-dip coal seam, a large-scale true triaxial fracturing simulation system was used to carry out physical simulation experiments, and the hydraulic fracture geometry of the maximum horizontal principal stress along the strike direction and along the dip direction-in 60° dip coal seam were investigated respectively. Experimental results of the maximum principal stress direction along the strike direction show that: hydraulic fracture initiation is easily; fracture height is limited in the whole time; fracture connectivity is good; fracture propagates mainly along bedding and natural fracture, vertical fracture is formed; the influence of high-dip on stimulation is relatively small; massive volume stimulation is needed. Experimental results of the maximum principal stress direction along the dip direction show that: hydraulic fracture initiation is hard; fracture height is limited in the early time and out of control in the later period; fracture connectivity is poor; fracture is not easy to form influenced by joint, and hydraulic fracture propagates difficultly; fracture diversion and multi-stage breakdown can be observed in the fracturing curve; small volume but multi-stage stimulation is needed. The experimental results have a good guiding effect on the stimulation model and scale determination of the high-dip coal seam in Xinjiang and other regions.