Experimental Study Onadsorption And Desorption Characteristic Of Cbm At Different Temperatures

The study on adsorption/desorption mechanism of CBM is the key theory to technological development of CBM. In the long-term experimental study of isothermal adsorption/desorption, we found that temperature changes were accompanied by pressure changes during the process of adsorption pressurized and desorption step-down, The temperature variation of free space at the same equilibrium pressure is different. At exploitation field of coal-bed methane, the gas production capacity of two wells with the identical basic geological conditions, technology, drainage system is very different. Especially for the vertical wells fractured on different seasons, as large quantities of pre-fluid enter to the coal-bed by small differences of temperature, the time starting to produce of two adjacent wells differ three months sometimes. All these show the temperature effect on adsorption/desorption process of CBM. Temperature effects to adsorption/ desorption of CBM is the current blind study, on which do require special experimental analysis.Through isothermal adsorption/desorption experiment of three coal samples at series of temperature points, get adsorption/desorption curve to the three samples of different rank. To fit experimental data of adsorption using Langmuir model, Weibull model for the experimental data of desorption. Calculate the heat of adsorption/desorption process with Clausius-Clapeyron equation, analysis the thermal effect mechanism to adsorption/desorption of coalbed methane. Then summed up the infection of temperature to adsorption/desorption. The main conclusions are these:(1)Langmuir model can describe the adsorption isotherm data well, and for the isothermal desorption process, Weibull model is the best model;(2)Adsorption is a continuous exothermic process, the greater the adsorption, the greater the heat released; And desorption process is non-spontaneous and endothermic, absorbed heat is less than the heat released at the same equilibrium pressure point of the adsorption process. Desorption processes lead to temperature decreases of the reservoir which restrains itself;(3)As the temperature increases, desorption rate increases. High pressure stage from 3.5 to 5Mpa, the temperature heighten is more sensitive than pressure lowering to the effects of desorption. And this pressure range is drainage stages, which is very important to drainage systems.