高温高压条件下深部煤层气吸附行为

摘要

为了对深部煤层吸附特性进行分析，以鄂尔多斯盆地东部主要煤层为对象，展开4组不同温度条件下煤样的高压等温吸附实验。从温度、压力、煤级等地质要素方面入手，研究较高温压条件下煤样的吸附特征。同时，通过对比分析各地质因素对吸附行为的影响，比较深部煤层吸附行为与浅部煤层吸附行为的差异性。结果表明：深部煤层的吸附特性主要受温度、压力的控制；高温条件下煤样对CH4的吸附量大大减少，且煤级、煤岩显微组分、灰分产率以及水分含量对吸附性能的影响已明显小于浅部煤层，温度、压力成为控制吸附量的决定因素。在100℃条件下，吸附量到达某一压力后随着压力的增大煤样吸附量下降，分析认为由于在此温压下，随着压力的增加，吸附相与游离相气体的密度差逐渐减小，超临界吸附已不再符合Langmuir等温吸附模型。%In order to analyze adsorption characteristics of deep coalbed, this paper studies the main coalbed of Eastern Ordos Basin and develops 4 groups of methane isothermal adsorption experiments of high pressure of the coal samples under different temperatures. By varying geological factors including temperature, pressure, and coal rank etc, we studied the adsorption characteristics under high temperatures and high pressures. Meanwhile, effects of geological factors on the adsorption behavior are analyzed by comparing results of different geologic factors, and the adsorption behaviors of deep coalbeds and shallow coalbeds. The results show that the adsorption characteristics of deep coalbeds is mainly influenced by temperature and pressure for deep coalbeds;The adsorption capacity of coal samples to CH4 is greatly reduced and the coal rank, coal macerals, ash content and moisture are less effective than the shallow coalbed on the adsorption property under high temperature conditions. So temperature and pressure become determinant factors in controlling the adsorption quantity. Adsorption capacities of the coal samples decrease along with the increase in pressure as the pressure reaches a certain value under 100℃according to the analyses, With the increase in pressure, the density difference of gas between the adsorbed phase and dissociative phase decreases gradually and Langmuir isothermal adsorption model is no longer applicable.