Influence of Fracture Morphology on Gas Desorption Promotion in Coal by Hot Water Injection

The influence of hydraulic fracture morphology on the flow of two-phase fluids and heat transfer characteristics during hot water injection into coal was studied by using a thermal-fluid-solid coupling model. Quantitative analysis was performed on the coal temperature distribution, fracture gas pressure, gas phase saturation dynamics, and total gas output variation. The results show that (1) with the change of fracture morphologies from single to complex combination, the average temperature of the coal body increases significantly. (2) The complexity of the fracture morphology increases the gas pressure of the fracture and expands the high-pressure area. (3) Fractures provide channels for hot water injection and gas migration, resulting in a gradient effect on gas saturation. (4) Gas output increases with the increase in fracture complexity. (5) The effective heat-affected area expands as the hot water injection duration extends and the fracture complexity rises. The results of this research have both vital practical worth and theoretical significance, enabling the execution of technology that integrates hydraulic fracturing with hot water injection to promote gas desorption within coal.