高煤阶煤储层解吸曲线定量表征及解吸参数研究

Quantitative Characterization of the Desorption Curve and Desorption Parameters of High-Rank Coalbed Methane(CBM)Reservoir

为定量研究煤层气井解吸特征文章通过煤样解吸实验获取解吸曲线并进行拟合回归得到了煤样解吸曲线定量表征公式。结果表明:煤样解吸曲线可以用v=(VdeT)/(T+Tde)来定量表征;解吸体积常数可表征煤样的最大解吸量解吸时间常数表征解吸气体体积达到最大解吸气体积一半时所用的解吸时间;煤样初始解吸速率等于解吸体积常数与解吸时间常数之比煤样解吸速率随着解吸体积常数增加而增加,随着解吸时间常数增加而降低。解吸时间常数与吸附时间成线性正相关关系,解吸时间常数越大,煤样解吸速率越小;在工程上可以用解吸体积常数代替解吸气量和残余气量之和;解吸时间常数随气体压力和裂缝指数增加而降低,随镜质组、惰质组含量增加而先增加后降低,与粘土矿物含量关系不明显;解吸体积常数随气体压力、惰质组含量增加而增加,与粘土矿物含量关系不明显,随着镜质组含量增加而降低,随裂缝指数先降低后增加。

This work quantitatively studies the desorption characteristics of CBM wells.A desorption curve is obtained through coal sample desorption experiments and then its quantitative characterization formula is derived by fitting regression.The results show that the coal sample desorption curve can be characterized quantitatively by v=(VdeT)/(T+Tde).The desorption volume constant can represent the maximum desorption volume of coal samples,and the desorption time constant can represent the desorption time when the volume of desorbed gas reaches half of the maximum desorption volume.The initial desorption rate of the coal sample is equal to the ratio of the desorption volume constant to the desorption time constant.There is a linear positive correlation between the desorption time constant and the adsorption time.In mining practice,the desorption volume constant can be used as the sum of volume of desorption gas and residual gas.The desorption time constant decreases with the increase of gas pressure and the fracture index,increases first and then decreases with the growth of vitreous and inert contents,while has no obvious relationship with clay mineral contents.Meanwhile,the desorption volume constant increases with the increase of gas pressure and inert content,decreases with the increase of vitreous content,while has no obvious relationship with clay mineral content and increases with the decrease of the fracture index.