影响沁南—中南煤层气井解吸压力的地质因素及其作用机制

摘要

以沁南的郑庄-樊庄区块和沁中南的长治-安泽区块为研究区,依据煤层气地质背景和气井排采资料,对各区块煤层气井的解吸压力分布特征以及引起区块间解吸压力差异的主要因素进行研究.结果表明:沁南的郑庄-樊庄区块西、北部煤层气井的实际解吸压力明显高于东南部、中部;沁中南的长治-安泽区块,解吸压力总体呈东西两翼低中部高的条带状展布;实际解吸压力和临界解吸压力的对应关系一定程度上与煤级有关;煤级,灰分含量及煤体结构的差异是盆地南部与中南部解吸压力差异的主要原因,地质构造、埋深是沁水盆地南部煤层气井解吸压力局部性变化的主要因素,而埋深、地应力是沁水盆地中南部煤层气井解吸压力区内差异的主要因素.%Based on geological settings of coalbed methane (CBM) and production data of CBM wells,which were obtained from the Zhengzhuang-Fanzhuang block and the Changzhi-Anze block in the southern and south-central regions of the Qinshui coal basin,respectivly,the distribution laws of desorption pressure of CBM wells between different CBM blocks were ana-lyzed,and the main influencing factors on the difference of desorption pressure were investigated. The results show that the actual desorption pressure of CBM wells in the west and north of the Zhengzhuang-Fanzhuang block is greater than that in the southeast and the central. For the Changzhi-Anze block,the desorption pressure in the east and west is lower than that in the central,showing a banding distribution. The relationship between the critical desorption pressure calculated by the adsorption theory and the actual desorption pressure obtained from CBM wells is influenced by coal ranks to some extent. Those factors, including the coal rank,the ash content and the deformation degree of coal body,result in the differences of actual desorption pressure between the southern part and the central-southern part in the Qinshui coal basin. In addition, our study suggests that geological structure and buried depth of coal seam are the main factors controlling the local changes of desorption pres-sure for the Zhengzhuang-Fanzhuang block,while buried depth of coal seam and in-situ stress are the principal factors for the Changzhi-Anze block.