Thermochemical sulfate reduction (TSR) is one of the main contributors to the formation of hydrogen sulfide (H2S) in coal seam strata. Four reaction systems (coal, coal+water, coal+water and MgSO4, and coal+water and MgSO4 and AlCl3) were selected and simulated from 250°C to 600°C with eight temperature steps using a high-temperature and high-pressure reaction device, and the evolution characteristics of the gaseous products of hydrocarbons (methane, C2-5) and nonhydrocarbon gases (CO2, H2, and H2S) were studied. Thermal simulation experiments showed that the TSR led to the reduction of heavy hydrocarbons, and the presence of salts accelerated the evolution of hydrocarbons; SO42-, Al3+, and Mg2+ had a certain promoting effect on the TSR, which increased the total amount of alkane gas, H2S, and CO2 production. Improving the salinity of the reaction system can promote the occurrence of TSR, and water plays a key role in hydrocarbon generation evolution and the TSR.

A hydraulic fracture extension model was established, an extension criterion and an extension mode of hydraulic fracture were analyzed, and the theoretical prediction was compared with the practical results, a good agreement was observed. Furthermore, the direction of hydraulic fracture extension was also discussed, the results showed that the hydraulic fracture propagates from the cut to the bedding plane, forming a complex mixture of longitudinal and transverse fractures fracture network. The hydraulic fracture extension direction is influenced by its extension critical pressure and its extension pressure in the rock formation. Practice shows that hydraulic fracturing can effectively weaken the strength and integrity of the roof, so that the roof in the mining area can collapse in layers and stages. The present theoretical analysis can be used for reducing or eliminating the hazard of the hard roof to the working faces.