四川盆地长宁地区志留系页岩气碳同位素组成  

Carbon isotopic composition of shale gas in the Silurian Longmaxi Formation of the Changning area,Sichuan Basin

作　　者：冯子齐[1] 刘丹[1] 黄士鹏[1] 吴伟[2] 董大忠[1] 彭威龙 韩文学[1] 

机构地区：[1]中国石油勘探开发研究院 [2]中国石油西南油气田公司勘探开发研究院

出　　处：《石油勘探与开发》2016年第5期705-713,共9页Petroleum Exploration and Development

基　　金：中国石油天然气股份有限公司"中国煤成气地球化学与成藏机制规律研究"项目(2014B-0608);中国南方海相页岩气高效开发的基础研究"页岩气优质储层形成机制与定量表征"(2013CB228001)

摘　　要：为了研究四川盆地长宁地区志留系龙马溪组页岩气碳同位素组成特征,以及该区过成熟页岩气碳同位素组成倒转成因,对长宁地区15个页岩气样的地球化学特征进行综合分析。通过测试烷烃气组分和碳同位素组成,结合四川盆地涪陵和威远地区龙马溪组页岩气碳同位素组成研究,长宁地区龙马溪组页岩气CH4含量为97.11%~99.45%,湿度平均为0.49%,δ13C1值异常重,平均可达-28.2‰,δ13C2平均为-33.2‰,气源母质为腐泥型,属于油型干气。随热演化程度增加,页岩气湿度逐渐降低,甲烷碳同位素组成整体变重,乙烷和丙烷碳同位素组成会发生反转,但长宁地区过成熟页岩气的乙烷和丙烷碳同位素组成处于反转后阶段,不会持续变重。综上,长宁地区页岩气甲烷碳同位素组成的重异常、碳同位素（δ13C1〉δ13C2〉δ13C3）的完全倒转现象,主要由过成熟阶段的二次裂解效应及乙烷瑞利分馏条件下与水、含铁金属发生反应等次生作用所导致,高地温条件也是重要影响因素之一。A comprehensive analysis was carried out on the geochemical characteristics of 15 shale gas samples from the Changning area to study the carbon isotopic composition features of shale gas and the reversal cause of carbon isotopic composition in post-mature shale gas in the Silurian Longmaxi Formation of the Changning area,Sichuan Basin.Through the analysis of alkane gas component and carbon isotopic composition,combining with the research on carbon isotopic composition from the Longmaxi Formation of the Fuling and Weiyuan areas in Sichuan Basin,the methane from the Longmaxi Formation shale gas accounts for 97.11% to 99.45%,the average gas wetness is 0.49% representing typical dry gas,abnormal average δ13C1 value as ？28.2‰ and the average of δ13C2 values is ？33.2‰,in view of sapropel-type kerogen,the Longmaxi Formation shale gas belongs to the typical oil-associated gas.With the increasing degree of thermal evolution,the wetness of shale gas decreases gradually,and carbon isotopic composition of methane becomes heavier,and the carbon isotopic composition of ethane and propane will reverse,but the carbon isotopic composition of ethane and propane in the post-mature shale gas of the Changning area stays in the post-stage of reverse and will not get continuously heavier.The abnormal heavy carbon isotopic composition of methane and the reversal phenomenon of carbon isotopic（δ13C1δ13C2δ13C3） mainly generate from the secondary cracking effect in the post-mature stage and reactions between ethane with ferrous metals and water under Reileigh fractionation situation.Furthermore,the high temperature is also one of the important influence factors.

关 键 词：四川盆地 长宁地区 志留系龙马溪组 页岩气 碳同位素组成 

分 类 号：TE122[石油与天然气工程—油气勘探]