雨汪区块煤层气气体同位素变化特征及成因判识  

Gas isotope variation characteristics and genesis identification of coalbed methane in Yuwang Block

作　　者：王芳芳 吴财芳[1,2] 杜明洋 唐依然 王聪 文德修 WANG Fangfang;WU Caifang;DU Mingyang;TANG Yiran;WANG Cong;WEN Dexiu(Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process,Ministry of Education,China University of Mining and Technology,Xuzhou 221008,China;School of Resources and Geosciences,China University of Mining and Technology,Xuzhou 221116,China;School of Resources and Civil Engineering,Suzhou University,Suzhou 234000,China;Shanxi Coal Geological Exploration Research Institute Co.,Ltd.,Taiyuan 030000,China;Bureau of Land and Mineral Resources Reserve of Guizhou Province,Guiyang 550001,China)

机构地区：[1]中国矿业大学煤层气资源与成藏过程教育部重点实验室,江苏徐州221008 [2]中国矿业大学资源与地球科学学院,江苏徐州221116 [3]宿州学院资源与土木工程学院,安徽宿州234000 [4]山西省煤炭地质勘查研究院有限公司,山西太原030000 [5]贵州省土地矿产资源储备局,贵州贵阳550001

出　　处：《煤炭科学技术》2024年第7期148-157,共10页Coal Science and Technology

基　　金：国家自然科学基金资助项目(42372182);国家自然科学基金重点资助项目(42130802);中央引导地方科技发展资金资助项目(YDZJSX2022D002)。

摘　　要：研究煤层气地球化学特征及其成因,对煤层气成藏及资源勘查开发具有重要意义。为探究滇东雨汪区块煤层气成因及其地球化学特征,采集该区6口典型煤层气井的产出气气样,开展了组分测定、碳同位素和稀有气体同位素测试,系统分析了煤层CH_(4)、N_(2)等气体的成因,并结合水文地质环境,探讨了雨汪区块煤层气排采过程中气体的同位素变化及其控制因素。结果表明:雨汪区块煤层气井产出气中CH_(4)体积分数平均为73.95%~92.90%,乙烷、CO_(2)、N_(2)体积分数分别为0.20%~0.40%、0.05%~1.05%、6.15%~25.32%。此外,He仅在产气第1天检测到,而碳原子数大于2的烃类未检测到;煤层气干燥系数(C_(1)/C_(1~5))为0.9995~0.9997,属于高成熟干气;CH_(4)的δ^(13)C值为-36.7‰~-27.6‰,为有机质热成因气;CO_(2)的δ^(13)C值介于-19.1‰~-6.6‰,主体分布在-18.0‰~-14.3‰,为有机成因;氮气体积分数平均为12.63%,含量相对较高,其φ(N_(2))/φ(Ar)远大于84,以有机成因为主;氩气体积分数平均为0.06%,远大于0.017%,以大气成因为主;氦气体积分数平均为0.02%,φ(^(3)He)/φ(^(4)He)为0.29×10^(-8)~19.6×10^(-8),主体范围为2.00×10^(-8)~9.38×10^(-8),φ(^(3)He)/φ(^(4)He)与大气氦的比值介于0.01~0.09,属于典型的壳源氦气,且φ(^(4)He)、φ(^(20)Ne)的变化趋势与φ(^(4)He)/φ(^(20)Ne)具有一致性;随着排采时间增加,气体纯度增高,产出气的烷烃同位素值呈现逐渐变轻的趋势。研究认为,雨汪区块煤层气“变干、变轻”是气体解吸、扩散和水溶解作用综合影响的结果。The research on the geochemical characteristics and genesis of coalbed methane(CBM)is of great significance to the formation and resource exploration-development.In order to investigate the genesis and geochemical characteristics of CBM in the Yuwang Block in eastern Yunnan,the gas samples from six typical CBM wells in the area were collected,and the composition determination,carbon isotope and rare gas isotope tests were carried out.The genesis of CH_(4),N_(2)and other gases in coal seam were systematically analyzed.Com-bined with the hydrogeological environment,the isotope variation of gases and their controlling factors during the CBM drainage process in Yuwang Block were investigated.The results shown that,the volume fraction of CH_(4)in the gas produced from CBM wells in the Yuwang Block averaged 73.95%-92.90%,and those of ethane,CO_(2)and N_(2)were 0.20%-0.40%,0.05%-1.05%and 6.15%-25.32%,re-spectively.In addition,helium was only detected on the first day of gas production,while hydrocarbons with a carbon atom number great-er than 2 were not detected.The drying coefficient(C_(1)/C_(1~5))of coalbed methane was 0.9995-0.9997,which belonged to high mature dry gas.Theδ^(13)C value of CH_(4)was-36.7‰--27.6‰,which was an organic matter thermogenic gas.Theδ^(13)C value of CO_(2)was-19.1‰--6.6‰,with the main distributed from-18.0‰to-14.3‰,which was of organic origin.The volume fraction of nitrogen averaged 12.63%,with relatively high content,and itsφ(N_(2))/φ(Ar)value was much larger than 84,dominated by organic genesis.The average con-tent of argon was 0.06%,much larger than 0.017%,dominated by atmospheric genesis.The volume fraction of helium averaged 0.02%,φ(^(3)He)/φ(^(4)He)was 0.29×10^(-8)-19.6×10^(-8),with the main distributed from 2.00×10^(-8)to 9.38×10^(-8),the ratio ofφ(^(3)He)/φ(^(4)He)to atmospher-ic helium was 0.01~0.09,which was typical shell source helium,and the variation trends ofφ(^(4)He)andφ(^(20)Ne)were consistent withφ(^(4)He)/φ(^(20)Ne).The alkane isotope values of th

关 键 词：煤层气 地球化学 成因类型 碳氢同位素 雨汪区块 

分 类 号：TE37[石油与天然气工程—油气田开发工程] P618[天文地球—矿床学]