Coalbed methane desorption characteristics controlled by coalification and its implication on gas co-production from multiple coal seams  

作　　者：Bin ZHANG Yafei ZHANG Suping ZHAO Wei HE Shu TAO Zhejun PAN Yi CUI 

机构地区：[1]School of Energy Resources,China University of Geosciences(Beijing),Beijing 100083,China [2]Coal Reservoir Laboratory of National Engineering Research Center of CBM Development&Utilization,Beijing 100083,China [3]China United Coalbed Methane Corporation Ltd.,Beijing 100016,China [4]PetroChina Research Institute of Petroleum Exploration and Development,Beijing 100083,China [5]Ningxia Mineral Geological survey Institute,Yinchuan 750021,China [6]Key Laboratory of Continental Shale Hydrocarbon Accumulation and Efficient Development(Ministry of Education),Northeast Petroleum University,Daqing 163318,China [7]China Huaneng Group,Beijing 100031,China

出　　处：《Frontiers of Earth Science》2023年第1期121-134,共14页地球科学前沿（英文版）

基　　金：This work was supported by the National Natural Science Foundation of China (Grant Nos. 42130802, 41772132), the Major Projects of Ningxia Key Research and Development Plan (No. 2020BFG2003);the Fundamental Research Funds for the Central Universities (No. 2652019095);the Key Technologies R&D Programme of PetroChina Company Limited (No. 2021DJ2306).

摘　　要：In this work,CH4 isothermal adsorption measurements were carried out on 64 coal samples collected from western Guizhou Province of China,and the coalbed methane(CBM)desorption processes were quantitatively analyzed.The results show that the Langmuir volume and the Langmuir pressure are controlled by coalification,and tend to increase as the vitrinite reflectance changes from 0.98% to 4.3%.Based on a division method of CBM desorption stages,the CBM desorption process were divided into four stages(inefficient,slow,fast and sensitive desorption stages)by three key pressure nodes(the initial,turning and sensitive pressures).The fast and sensitive desorption stages with high desorption efficiency are the key for achieving high gas production.A theoretical chart of the critical desorption pressure(P_(cd))and its relationship with different pressure nodes was established.The higher-rank coals have the higher initial,turning and sensitive pressures,with larger difference between pressure nodes.Most CBM wells only undergo partial desorption stages due to the differences in P_(cd) caused by the present-gas content.Under the same gas content conditions,the higher the coal rank,the less desorption stages that CBM needs to go through.During coalbed methane co-production from multiple coal seams within vertically superposed pressure systems,the reservoir pressure,the P_(cd),the initial working liquid level(WLL)height,and coal depth are key factors for evaluating whether coal seams can produce CBM simultaneously.It must be ensured that each production layer enters at least the fast desorption stage prior to that the WLL was lower than the depth of each layer.Only on this basis can all layers achieve the maximum gas production.

关 键 词：co-production from multiple coal seams CBM adsorption DESORPTION coal rank 

分 类 号：P618.11[天文地球—矿床学]