Effect of Creep on Gas Drillings in Soft Coal Seam

In order to solve the problems of larger deformation and poor stability of gas extraction boreholes in soft coal seam, based on mechanical model of interaction between creep coal seam and casing pipe, the influence of creep of soft coal seam on stability of gas extraction borehole formation is studied under non-uniform stress by theoretical analysis and ABAQUS numerical simulation, the creep conditions of the soft coal seam with or without cement ring and casing were compared. The results show that the effect of cement ring and casing pipe on the stability of the coal hole is positive. When the drilling diameter is φ85 mm, the stress of casing and hole wall is smaller.