A Study Of The Transport Mechanism And Model Of Coalbed Methane On Different Pore Scale

Coalbed methane disaster is always one of the main disasters to threaten the security of coal mine in the coal exploitation, but at the same time coalbed methane is the strategic alternative energy in 21st century. A lot of research has been done on this alternative energy, but until now some problems still remain unsolved, such as the absorption, desorption, diffusion essence in the process of exploration and control. Based on the previous research done by other scholars, this thesis focuses on the following:1.The structure of three-dimensional cross-link giant molecules and the impact of small molecular atomic ground group on the absorption of coalbed methane are introduced.2.Different classifications of coalbed fractures and pores fracture is summarized, the different roles of pores and fractures system are illustrated in coalbed methane absorption and mass transition, based on the physical characteristics and the construction network structure.3.The absorption between coal and methane is investigated and the adsorption potential of coal and methane is calculated; the different types of absorption: Fick diffusion, Knudsen diffusion, Transitional diffusion, Surface diffusion, and Crystal diffusion are discussed. To judge the types of absorption with Knudsen number is not appropriate on the basis of factors, such as the impacts of gas compressibility, reservoir pressure and temperature; the absorption coeffient formulae: D = (1 -ω)D_fe +ωD_ne + D_se + D_C is developed. The gas's slippage effects is investigated.4.The methane desorption, diffusion and seepage flow essence of coalbed methane is explored , the Gas's Darcy Law is deduced; the mathematic model of methane seepage diffusion is established, with the factor of slippery under consideration.5.The diffusion fracture network seepage flow theory which is different from continuous media is discussed; the model of diffusion fracture network seepage flow is set up by the graph method, the program of solving the model is written by Matlab software. The feasibility of using the model to solve the flow of fluid in coal rock mass is testified.