Comprehensive Evaluation of In Situ Stress in the Daning–Jixian Area and Its Control on the Distribution of Coal-Measure Gas

Revealing the distribution of coal-measure gas (CMG) in horizontal and vertical directions as well as the stimulation effect of coal-measure reservoirs under different geological conditions is significant for guiding the co-prospecting and co-production of CMG. In this study, the characteristics of in situ stress in the Daning–Jixian area were analyzed using optimized evaluation methods. Then, the effects of various stress parameters on the reservoir parameters, stimulation effect of coal seams, and spatial distribution of CMG were discussed. It was found that the pressure, gas content, and porosity of coal reservoirs show different trends with increasing vertical stress, namely linear increase, first increase and then decrease, and exponential decrease. Compared with transitional stress areas, fractures in tensile stress areas are likely to expand horizontally, and areas with tension stress states or larger horizontal stress differences have better stimulation effect. In addition, the gas content of coal reservoirs in horizontal directions is higher when the roof and floor (RF) are mudstones and the in situ stress index is lower. In comparison, the CMG is more likely to escape from hydrocarbon source rocks and enriches in the adjacent coal-measure reservoirs, when the RF are sandstones or the in situ stress index is higher. The lithology of RF is the crucial geological factor for gas content in the transition stress areas, whereas in situ stress is the most important geological factor in compression stress areas.