煤层气井实际解吸阶段影响因素及意义

The Significance and Geolgocal Controls on the Actual Desorption Stages of Coalbed Methane Well

为了明确煤层气井解吸段数的确定方法及影响因素,基于前人提出的解吸阶段划分方法,提出了实际解吸段数概念和相应的确定方法,基于沁对水盆地和鄂尔多斯盆地东缘煤层等温吸附参数和解吸压力数据研究,了解吸段数的影响因素及意义。结果表明,此次所提方法能够有效确定煤层气井解吸段数并估算初始解吸效率,煤层气井实际解吸阶段由兰氏压力、兰氏体积和解吸压力决定。兰氏体积增加,解吸阶段减少,解吸效率增加;兰氏压力增加,解吸段数先减少后增加,初始解吸效率先增加后降低。解吸压力越高,煤层气开发经历的解吸阶段越多,初始解吸效率越低。实际解吸阶段是煤层气储层评价的有效参数,沁水盆地南部煤层气井只有1~2个解吸阶段,大部分处于敏感解吸阶段,总体解吸效率较高。鄂东缘煤层气井一般有3~4个解吸阶段,解吸效率整体较低。

In order to determine the division method and influence factors of the number of desorption stages for CBM wells,the concept,the number of actual desorption stages,and the corresponding determining method are proposed in this present study,based on the desorption stages dividing method proposed by the previous researchers.The influence factors and significance of actual desorption stages are studied,based on the parameters of isothermal adsorption and desorption pressure from Qinshui Basin and the eastern margin of Ordos Basin.The results show that the method given by this paper can effectively determine the number of desorption stages,and estimate the initial desorption efficiency for some CBM wells.The actual desorption stage of CBM well is determined by Langmuir pressure,Langmuir volume,and the desorption pressure.With the increase of Langmuir volume,the number of desorption stages decreases while the initial desorption efficiency increases.With the increase of the Langmuir pressure,the number of desorption stages firstly decreases and then increases while the initial desorption efficiency firstly increases and then decreases.The higher the desorption pressure is,the more desorption stages the CBM well will go through during the development,and the lower the initial desorption efficiency is.The actual desorption stages is an effective evaluation parameter for formation evaluation.In Southern Qinshui Basin,there are only 1 or 2 desorption stages of CBM Wells,most of which are in the sensitive desorption stage,and the overall desorption efficiency is high.While in Eastern Ordos Margin,there are generally 3 or 4 s desorption stages,and the desorption efficiency is generally low.