晋城地区煤层气解吸及碳同位素分馏特征

Desorption and Carbon Isotope Fractionation of Coalbed Methane in Jincheng Area

通过晋城地区煤心样的解吸实验，计算获得该区煤层甲烷的解吸率为65．0％～96．2％，预测煤层气井应具有较高的采收率。煤层吸附时间为0．33～8d，表明生产井短时间内可以达到产能高峰。罐装煤样气体解吸过程可分为两个阶段，第一阶段气体解吸速率较高，第二阶段解吸速率较低。解吸过程中甲烷碳同位素变重的趋势同样可分为先快后慢两个阶段。煤储层气体解吸过程中发生的同位素分馏效应导致井口气样甲烷碳同位素值在一定范围内波动。波动持续时间越长，预示该井的开采稳定性越好，可以获得长期稳定的产气量。通过对煤样解吸气量与甲烷碳同位素的相关分析，获得了总解吸量预测方程，根据该方程可以预测生产井的可采储量。

The canister desorption experiments of the coalbed methane （ CBM ） from the coal samples of the Jincheng area were carried out, and the CBM desorption rate was calculated as 65.0% - 96.2%. The estimated recovery of coalbed gas well should be higher in this area. The CBM adsorption time is 0.33-8 d, which indicates that the CBM-producing well should reach a peak productivity in a short time. The CBM desorption process can be divided into two stages, the gas desorption rate is higher at the first stage and lower at the second stage. In the desorption process, the CBM carbon isotope tends to become heavier, but the tendency seems to be faster at the first stage and slower at the second stage. The CBM carbon isotopic fractionation during the gas desorption from coal reservoir might result in a fluatuation of δ^13C1 value in well head in a narrow range. A longer period of fluctuation might mean a better exploitation stability and a higher production. Through the correlation analysis of the desorption amount and the carbon isotope value, the total gas desorption predicting equation was regressed, by which the producible reserves of the coalbed gas well can be predicted.