Review on desorption-diffusion-flow model of coal-bed methane

Abstract

Literature reviews on matrix pores classification, gas and water phase behavior characteristics, kinetic behavior of methane in coal matrix pores, desorption model, diffusion model, percolation model, and gas production model of Coal-bed Methane (CBM) are conducted. It is concluded that the production process of CBM includes adsorbed gas desorbing, a small amount of desorbed gas dissolving into water and diffusing, a large amount of gas nuclei escaping after saturated, gas bubble and column forming, gas bubbles and columns percolating in matrix pores, free gas cross-flowing from matrix pores to cleat-fracture system, free gas flowing from matrix pores to wellbore (in case of low stage coal seam), and free gas percolating from cleat-fracture system to wellbore. As a reference to development of CBM and a theoretical basis on numeric simulation of CBM, it is valuable to the better understanding of gas production discipline of CBM.

Peak Gas Production Analysis and Influencing Factors Study of Coal Bed Methane Well

“…Different from the conventional natural gas production mechanism, the producing process of coalbed methane (CBM) is characterized by desorption diffusion and seepage [1,2]. The coal seam gas can only be produced when the reservoir pressure decreases down below the desorption pressure.…”