考虑温度影响下煤层气解吸渗流规律试验研究

Experimental study on desorption and seepage rules of coal-bed gas considering temperature conditions

通过不同温度条件下煤层气渗透率、渗流量测定的试验,研究了温度条件下煤层气渗透率、渗流量的影响因素,得到考虑温度情况下的煤层气解吸渗流规律。利用三维应力条件下煤样吸附解吸试验系统,在三轴渗透仪中加入温度控制系统,测定煤样在温度、围压、轴压和孔隙压力的不同组合情况下的渗透率和渗流量。结果表明,在相同围压、轴压和孔隙压力情况下,煤样渗透率随温度的增加而减少;不同温度条件下,渗透率随孔隙压力的增加均以指数形式递增。在相同围压、轴压和孔隙压力情况下,等温解吸时,煤样渗流量随温度的增加而减少;升温解吸时,煤样20℃吸附、升温至40℃解吸时渗流量比20℃吸附、20℃解吸时明显增加;等温或升温情况下,渗流量随孔隙压力增加均呈现非线性递增关系。这一规律对煤层气热采方式的选择具有重要指导意义。

Through the experiments on permeability and seepage flux of coal-bed gas under different temperatures, the affecting factors of permeability and seepage flux of coal-bed gas were studied, and the rules of permeability and seepage of coal-bed gas were obtained concerning temperature conditions. Using the 3D experimental devices of CBM desorption, the temperature controlling sYstem was added, and the permeability and seepage flux of coal samples were measured under different temperature, confining pressure, axial pressure and pore pressure. It was shown that under the same conditions of confining pressure, axial pressure and pore pressure, the permeability of coal gas decreased as the temperature increased; the permeability increased exponentially as the pore pressure increased under different temperatures. Under the same confining pressure, axial pressure and pore pressure, the seepage flux of coal-bed gas decreased as the temperature increased in the isothermal desorption in the calefactive desorption, the sorption occurred at 20℃ and desorption occurred when temperature increased to 40℃, the seepage flux increased more obviously than in the sorption and desorption at 20℃. Under the calefactive and isothermal conditions, the seepage flux increased nonlinearly as the pore pressure increased. This rule was significant for choosing the way of gas injection heat mining of coal-bed.