The in-situ stress state significantly influences the development of coalbed methane (CBM). The Changzhi Basin in Shanxi Province, North China has abundant CBM resources, but the reliable in-situ stress in this area remains poorly understood. We conducted hydraulic fracturing and imaging logging tests in a 600-m-deep borehole at the Changcun coal mine in the Changzhi Basin. The magnitude and orientation of the maximum horizontal principal stress ( \({\text{S}}_{\text{Hmax}}\) ) were jointly constrained using the imaging logging data, and the in-situ stress data were analyzed. The results show that thrust-faulting and strike-slip faulting stress regimes develop from shallow to deep in the Changcun coal mine area and that the main orientation of the \({\text{S}}_{\text{Hmax}}\) is N38.7° ± 7.3°E, which is consistent with the background of the regional tectonic stress field. The \({\text{S}}_{\text{Hmax}}\) magnitudes constrained by the borehole failures are higher than those measured by the hydraulic fracturing method, regardless of their uncertainties, which provides the upper limit ranges for \({\text{S}}_{\text{Hmax}}\) . The principal stress profile shows that the reservoir in the study area is in the critical stress state restricted by the frictional coefficient of 0.6–1.0. However, the in-situ stress orientation also exhibits heterogeneity with depth, shifting to N72° E and N75° E near the fault and coal seam, respectively, which differ from the mean \({\text{S}}_{\text{Hmax}}\) orientation by approximately 33.3° and 36.3°. We speculate that this stress variability is related to abrupt changes in rock stiffness. Interestingly, the heterogeneous lithology leads to compressive failure in mudstones while tensile failure in sandy mudstones. This shows the sensitivity of borehole failure modes to differences in rock mass strength. We use the Mohr–Coulomb failure criterion to evaluate the possibility of reservoir fracture reactivation at different pore pressures in the CBM hydraulic fracturing stimulation operations. The results show that although the natural fractures are generally stable under the current in-situ stress state, the critical pore pressure to reactivate them is relatively low. This study indicates that the combined constraint methods of hydraulic fracturing and image logging have valuable prospects for evaluating the detailed stress state of shallow engineering rock masses.
