等温吸附曲线方法在煤层气可采资源量估算中的应用

Application of Isothermal Curves in Estimating Minable Resource of Coalbed Methane

在缺乏煤层气井生产资料的情况下,为了合理利用我国煤田地质勘探中煤层气解吸法所测的煤层气含量,使其计算的煤层气资源量与可采资源量更为接近,根据煤层气解吸特征,煤储层等温吸附特征,通过计算解吸系数,求取煤层气的解吸率.利用等温吸附曲线与煤层气临界解吸压力的关系,估算出煤层气临界解吸压力,并结合煤层气井的枯竭压力,估算出煤层气采收率,进而获得煤层气可采资源量.结果表明,残余气在煤层气开采时基本上是不可能获得的,另外由于生产技术的原因,参考国外煤层气实际生产情况,井深结构所能达到的最低储层压力之下的煤层气也基本上不能被采出.因此通过解吸系数法校正、等温吸附曲线法校正后,计算的煤层气资源量更能反映煤层气的可采潜力.

The data of coalbed methane （CBM） contents obtained from coal resource exploration can be used to evaluate the CBM and recoverable CBM resources. Based on the characteristics of CBM desorption and coal isothermal adsorption, the desorption ratio of CBM is obtained through calculating the CBM desorption coefficient. The critical desorption pressure is estimated based on the relationship of isothermal adsorption curve to the critical desorption pressure. Then, the recoverable CBM ratio can be calculated in combination with the abandoned pressure of CBM well, and then the recoverable CBM resources can be obtained. The result shows that the remnant CBM can＇t be recovered out from coal seam. Moreover, the CBM resources under the condition of the lower limit of the coal reservoir pressure with respect to the depth of CBM well is nearly impossible to be mined. Thus, the recoverable potential of the CBM can be reasonably reflected by the CBM resources calculated through the emendation of the desorption coefficient and isothermal adsorption curve.