| Coal reservoirs methane adsorption always affected by groundwater. Coal seam stored in high temperature environment layer for the increase depth of coal mining, so thermal effect and water act on high- gas coalbed that constitute the system of coal absorbs gas. Taking the coal of Guqiao coalmine in Huainan for experiment, this paper research the impact of thermal effect and moisture on adsorption capacity of coal, which could provide basic theory for coalbed methane exploitation and accurate determination of the gas parameter of the reservoirs.To explore the influence of thermal effect to the change of coal’s pore structure and the isothermal adsorption of methane. Then the experime nts of analyze the pore structure and coal isothermal adsorption were carried out to the coal samples that heated by 45℃,60℃,and 75℃.Through CO2 adsorption and mercury injection experiments, the results found that the total pore volume and pore specific surface area of coal after high-temperature water treatment is increased with the rising of water temperature. The increment of coal porosity treated by water temperature between 60℃ and 75℃ is 30 times treated by water temperature between 45℃ to 60℃. In the equal pressure of isothermal adsorption, the amounts of coal adsorption also increase with the rising of temperature. The adsorption constant a of coal samples from different temperature conform to quadratic function relation with the heating temperature.The analysis of case of coal methane adsorption under water is utilized by physics, chemistry theory and adsorption isotherm experiments. By calculating intermolecular force, we know van der Waals force between coal macromolecules and methane molecules in water medium is much less than force between coal macromolecules and water molecules due to the presence of hydrogen bonding in vacuum medium. Within the range of experimental coal moisture content, the isotherm adsorption constant of a value and coal mo isture content accord with quadratic function, in which we do adsorption isotherm experiments on coal samples in Guqiao central and south district with different moisture content. The mathematical expression of the coal adsorption amount of pressure and moisture content is obtained by combing exponential equation which is fitted through coal adsorption capacity under certain pressure and moisture content with the moisture correction formula. Because of the influence of the water,isothermal adsorption experiment with equilibrium water coal samples which represent the water of the original reservoir,it can simulate the real situation of coal adsorption. When determining the gas pressure of 1414(1) face in Guqiao coal, the quick calculated gas pressures obtained by equilibrium water coal samples test’s adsorption constant and gas content are more close to the actual gas pressures than that by dry coal samples. |
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