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黔西-滇东地区煤岩吸附-解吸特征及其对多层合采的指示意义
李站伟,陈世达,陶树,汤达祯,丁鹏飞
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(1.中国地质大学(北京)能源学院,北京100083;2.煤层气开发利用国家工程研究中心中国地质大学(北京) 煤储层物性实验室,北京100083;3.中国石化胜利油田分公司油气销售中心,山东东营257000)
摘要:
为研究黔西-滇东地区煤岩变质程度控制下的煤岩吸附-解吸特征,基于83块煤岩样品的甲烷等温吸附曲线系统分析,建立煤岩吸附-解吸特征参数与煤岩变质程度之间的数学统计模型,并探讨其对多煤层合采产层组合优化的指示意义。研究结果表明:随着煤级的增高,煤岩趋于致密化,微小孔的比表面积大幅增加,对甲烷的吸附能力也显著增强;解吸关键压力节点(启动压力、转折压力、敏感压力)及各解吸阶段(低效解吸阶段、缓慢解吸阶段、快速解吸阶段、敏感解吸阶段)覆盖压差也随之增大。当镜质组反射率大于3.0%时,煤岩储渗空间及吸附-解吸特征参数开始趋于稳定。研究区煤岩变质程度的差异分布和叠置压力系统的空间分异,进一步导致不同煤层解吸产气过程的复杂化。从多层合采的角度而言,在煤层暴露之前,确保产层实现较高的解吸效率,才能保证合采产能和 分层贡献,并据此划分出产层组合评价的七类约束条件,进而用于指导多层合采方案的设计。
关键词:  变质程度  煤层气  多层合采  吸附-解吸  产层组合  黔西-滇东地区
DOI:10.13673/j.cnki.cn37-1359/te.2021.01.015
基金项目:国家科技重大专项“多煤层煤储层精细描述及可改造性研究”(2016ZX05044001-003),国家自然科学基金项目“深部煤层气系统及其能量动态平衡机理研究”(41530314)。
CBM adsorption-desorption characteristics of coal in western Guizhou-eastern Yunnan region and its significance to commingled production
LI Zhanwei,CHEN Shida,TAO Shu,TANG Dazhen,DING Pengfei
(1.School of Energy Resources,China University of Geosciences(Beijing),Beijing City,100083,China;2.Coal Reservoir Laboratory of National Engineering Research Center of CBM Development & Utilization,China University of Geosciences(Beijing),Beijing City,100083,China;3.Oil and Gas Sales Center,Shengli Oilfield Company,SINOPEC,Dongying City,Shandong Province,257000,China)
Abstract:
CH4 isothermal adsorption curves of 83 coal samples were systematically analyzed,and the statistical model between coal rank and parameters related to adsorption-desorption characteristics were established to reveal the influence of coal rank on CBM adsorption-desorption characteristics in the western Guizhou-eastern Yunnan region. Also,its implications on the optimization of production-layer combination were discussed. The analysis shows that a higher coal rank leads to denser coal,much larger specific surface areas of micropores,and further better adsorption to CH4,resulting in higher desorption pressure at key nodes(starting,turning,and sensitive points)and greater overburden pressure differences at every desorption stage(inefficient,slow,fast,and sensitive stages). When vitrinite reflectance is more than 3.0%,the pore-fracture system and CBM adsorption-desorption characteristic parameters of coal tend to be stable. This differential distribution of coal rank in the study area and the spatial differentiation of the superimposed pressure system further complicate the desorption of different coalbeds. The high desorption efficiency of each production layer before coalbed exposure is an important prerequisite to ensuring the commingled production and gas productivity of each layer. Based on this,the seven constraints on the feasibility of the production-layer combination are identified to guide the future project design of commingled production.
Key words:  coal rank  CBM  commingled production  adsorption-desorption  production-layer combination  western Guizhou-eastern Yunnan region

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