银额盆地古生界过成熟烃源岩特征及其地球化学意义  

Characteristics and geochemical indication of over-mature source rocks in the Paleozoic,Yingen-Ejinaqi Basin

作　　者：陈治军 张春明 贺永红 文志刚 马芳侠 李渭[3] 高怡文 陈义国 张慧元[3] 魏东涛 Chen Zhijun;Zhang Chunming;He Yonghong;Wen Zhigang;Ma Fangxia;Li Wei;Gao Yiwen;Chen Yiguo;Zhang Huiyuan;Wei Dongtao(College of Resources and Environment,Yangtze University,Wuhan,Hubei 430100,China;Research Institute of Yanchang Petroleum(Group)Company Limited,Xi’an,Shaanxi 710075,China;Xi’an Center of Geological Survey,China Geological Survey,Xi’an,Shaanxi 710054,China)

机构地区：[1]长江大学资源与环境学院,湖北武汉430100 [2]陕西延长石油(集团)有限责任公司研究院,陕西西安710075 [3]中国地质调查局西安地质调查中心,陕西西安710054

出　　处：《石油与天然气地质》2022年第3期682-695,共14页Oil & Gas Geology

基　　金：国家自然科学基金项目(41872144);延长石油集团科技攻关项目(ycsy2020jcyj-B-03)。

摘　　要：银额盆地的部分钻井和野外露头发现了古生界过成熟烃源岩,对于分析盆地古生界油气成藏条件、探讨过成熟烃源岩地球化学问题等有重要的意义。对25个过成熟烃源岩样品开展测试分析,研究其地球化学特征,分析其原始生烃潜力。结果表明:①烃源岩总有机碳含量平均为1.31%,有机质类型为Ⅱ_(1)-Ⅱ_(2)型,镜质体反射率R_(o)平均为4.20%,为残余有机碳含量较低、混合型干酪根的过成熟烃源岩;②主要受控于热降解作用,过成熟烃源岩的生物标志化合物普遍呈现“正构烷烃具有双峰型、甾类化合物中孕甾烷(含升孕甾烷)具有异常高的相对含量、萜类化合物中三环萜烷的相对含量较高、芳烃化合物中低碳环数化合物占据优势”等特征;③提出了“有机碳构成”的概念,建立了基于岩石热解资料计算有机碳构成的方法,计算结果表明虽然本研究中过成熟烃源岩的有效碳仅占极小的一部分,但烃源岩原始总有机碳含量平均为2.07%,且烃源岩具有持续时间长、产率较高的生烃特征,明确了银额盆地古生界过成熟烃源岩具有较高的生烃潜力。The Paleozoic source rocks encountered by some wells and present on outcrops in Yingen-Ejinaqi Basin are believed to carry with them important geochemical information that will help understand the oil and gas accumulation conditions in the Paleozoic system of the basin.Geochemical characterization and hydrocarbon generation potential assessment of 25 such rock samples indicate over-mature(Ro=4.20%)source rocks with low total organic carbon(TOC)content(1.31%)and mixed kerogen types(typesⅡ_(1)-Ⅱ_(2)).They are mainly products of thermal degradation with biomarkers showing a bimodal N-alkanes,abnormally high relative abundance of pregnane(including L pregnane)in steroids,high relative abundance of tricyclic terpene in terpenoids,a predominance of low-carbon ring number compounds in aromatic compounds and other characteristics.A concept of“organic carbon composition”is presented and a method for calculating its value based on rock pyrolysis data is established.The results show that although the pyrolytically effective carbon only accounts for a fraction of organic carbon composition of the over-mature source rock,the original average TOC content of source rock is high at 2.07%.In addition,the duration of hydrocarbon generation is long and its yield is high.Therefore,the Paleozoic over-mature source rocks in Yingen-Ejinaqi Basin are suggested to have a high original hydrocarbon generation potential.

关 键 词：有机碳构成 生物标志化合物 地球化学特征 过成熟烃源岩 古生界 银额盆地 

分 类 号：TE122.1[石油与天然气工程—油气勘探]