A Feasibility Study of Coal Seam Water Injection Processes: The Effects of Coal Porosity and Mass Flow Rates of Injected Water on Wetting Radii

Various effective methods of water injections for coal seams, which have been implemented in order to control coalmine disasters, have attracted substantial renewed interest in the fields related to water injection process parameters and the physical properties of coal seams. The water injection parameters, typically the mass flow rates of the water injections, are known to significantly affect the osmotic pressure levels and saturated wetting times. However, there remains a lack of effective evidence for wetting efficiency, such as wetting radii, infiltration regions, and diffusion times. In this study, the effects of porosity and mass flow rates were investigated using both numerical simulation and field application methods. The test results revealed that the moisture content, natural moisture absorption, firmness coefficients, and contact angles of the coal samples have satisfied the criteria for the identification of the feasibility of water injections in coal seams. In addition, the simulated results highlighted and quantified the wetting radii in different porosity and mass flow scenarios. The influencing effects of the wetting radii were mainly attributed to the constant flow rates of the water injections with the increased osmotic pressure, rather than the porosity levels. Moreover, as the porosity of the coal seams decreased, it was found that the water injection radii tended to increase. In comparison with the simulated results, the field measured results were also observed to demonstrate that there were remarkable improvements in the wetting radii when the porosity level equaled 7.2% combined with 3.88 m(3)/h. The findings obtained in this study will potentially be helpful in guiding and improving actual field applications.