Abstract

Coalbed methane wells on the ground in coal mining areas are used to extract a large amount of gas from the working face, but mining activities can cause strata movement, resulting in casing deformation. Numerical simulation was used to study the shear stress loading of casing under thick alluvial conditions. The study found that the casing will have shear stress peak points at the interface between the aquifer, alluvial layer and bedrock, and the mudstone layer in the bedrock, with a stress intensity of 49.9–77.1 MPa. The peak shear stress point of the casing in the aquifer will appear 4 m below the aquifer floor as the working face is mined. The casing stress at the junction of the thick alluvial layer and the bedrock increases linearly with depth, and the stress peak appears just above the junction. The casing stress in the bedrock section fluctuates periodically with lithology changes, and the stress peak mostly appears in weak rock formations such as mudstone. The introduction of non-uniform stress theory explains the reasons for casing deformation in these layers, and proposes suggestions for casing deformation control. This study can provide a reference for the formulation of casing deformation control methods.