摘要
湘鄂西地区位于中扬子板块,研究区龙马溪组富有机质页岩的有机质类型以Ⅱ1型为主,Ⅱ2型次之,TOC含量高,有机质热成熟度高,页岩矿物以脆性矿物为主,黏土矿物次之。通过分析三个实验阶段(20℃、65℃、90℃)解析气样发现,气体中CH4含量较高(90. 34%~99. 64%),含有少量非烃气体。龙马溪组页岩气CH4碳同位素值为-41. 9‰^-30. 8‰,C2H6碳同位素值为-42. 3‰^-36. 2‰,δ2HCH4为-193. 4‰^-156. 0‰,随着成熟度的增加,CH4碳同位素、C2H6碳同位素以及CH4氢同位素都有升高的趋势。烃类气体碳同位素具有明显的倒转现象,即δ13C1>δ13C2。根据解析实验三个阶段的气体同位素特征和测得的各阶段含气特征建立游离气与吸附气所占比例的计算公式,进一步推算出解析过程总含气量中所含有的游离气量以及吸附气量。
The Longmaxi Formation organic-rich shale,featured by high total organic carbon(TOC)and high thermal maturity,is located in western Hunan and Hubei region of the middle Yangtze plate.Organic matter in the region are typeⅡ1 to typeⅡ2 kerogen and are dominated by the former.In the region,brittle minerals(dominant)and clay minerals are abundant in the organic-rich shale.The CH4 content of the gas samples is high(90.34%to 99.64%),and the gas also contains minor non-hydrocarbon components,as revealed by the experiment under 20℃,65℃,and 90℃.CH4 carbon isotopes of the hydrocarbon gases are of-41.9%to-30.8‰,whilst those of C2H6 andδ2 HCH4 are of-42.3%to-36.2‰and-193.4%to-156.0‰,respectively.With increasing maturity,carbon isotopes of CH4 and C2H6,and hydrogen isotope of CH4 all become heavier.Carbon isotopes of the hydrocarbon gases show clear reversals,i.e.δ13 C1>δ13 C2.Accurate calculation of the free gas and adsorbed gas in the shale gas is of substantial guiding significance for the future exploration and development.Therefore,our work establish the calculation formula of the proportion of free gas and adsorbed gas according to the gaseous isotope characteristics of the three temperature stages of the experiment and the gas bearing characteristics measured at each stage.The free gas volume and the amount of adsorbed gas contained in the total gas content could thus be determined.
作者
张鹏
陈世敬
刘子驿
黄宇琪
杨军伟
刘洪洋
ZHANG Peng;CHEN Shijing;LIU Ziyi;HUANG Yuqi;YANG Junwei;LIU Hongyang(School of Mining&Civil Engineering,Liupanshui Normal University,Liupanshui,Guizhou553004,China;Key Laboratory of Shale Gas Exploration and Evaluation(Ministry of Land and Resources),China University of Geosciences(Beijing),Beijing100083,China)
出处
《现代地质》
CAS
CSCD
北大核心
2019年第4期883-889,共7页
Geoscience
基金
贵州省科技计划项目(黔科合基础[2017]1420)
贵州省教育厅青年科技人才成长项目(黔教合KY字[2016]266号)
