Study on process and model of CBM dissipating

Coal Bed Methane(CBM) occurs in coal seams in the states of adsorption gas, free gas and water-dissolved gas. Its dissipating starts with desorption, and then it dissipates outwards in the states of free gas and water-dissolved gas. The dissipating approach is classified to three patterns:Free gas in pores dissipates through the cover rocks; hydrocarbon molecules in the cap-rocks and reservoir diffuse because of concentration gradient; gas dissolving in water is directly taken away by water. According to the controlling factors of CBM conservation and considering the cover rocks,soleplate, hydrological region identification and dissipating theory, three geological models of CBM dissipating are built:closed system model, lateral hydrological closed model and open system model.