准噶尔盆地玛湖凹陷含油储集岩连续抽提组分地球化学特征与油源对比  

Oil source assessment based on molecular and carbon isotopic compositions of oil-containing reservoir rocks in the Mahu Sag,Junggar Basin

作　　者：张仲达 谷元龙 靳军[4] 李二庭[4] 于双[1,2] 潘长春 ZHANG Zhongda;GU Yuanlong;JIN Jun;LI Erting;YU Shuang;PAN Changchun(State Key Laboratory of Organic Geochemistry,Guangzhou Institute of Geochemistry,China Academy of Sciences,Guangzhou 510640,Guangdong,China;University of Chinese Academy of Sciences,Beijing 100049,China;CAS Center for Excellence in Deep Earth Science,Guangzhou 510640,Guangdong,China;Research Institute of Experiment and Testing,Xinjiang Oilfield Company,PetroChina,Karamay 834000,Xinjiang,China)

机构地区：[1]中国科学院广州地球化学研究所,有机地球化学国家重点实验室,广东广州510640 [2]中国科学院大学,北京100049 [3]中国科学院深地科学卓越创新中心,广东广州510640 [4]中国石油新疆油田公司实验检测研究院,新疆克拉玛依834000

出　　处：《地球化学》2024年第3期351-369,共19页Geochimica

基　　金：中国科学院先导项目(XDA14010104);国家科技重大专项专题(2017ZX05008-002-030)联合资助。

摘　　要：近十年来,在玛湖凹陷发现了大面积连片分布的砾岩大油区,但凹陷区及其西部边缘克–百断裂带油气富集区的油源仍不清晰,分析原油的来源和充注过程对于推动该地区勘探具有重要的实际意义。通过对玛湖凹陷南斜坡和西斜坡21个含油储集岩样品进行连续抽提,获得了自由态组分a1和a2、束缚态组分b和包裹体组分c。对这些组分与同井位的13个原油样品进行GC、GC-MS以及GC-IRMS分析,依据正构烷烃单体C同位素组成特征,将含油储集岩连续抽提组分和原油样品分为Ⅰ、Ⅱ和Ⅲ类油组分。Ⅰ类油组分来源于下二叠统风城组(P_(1)f)烃源岩,Ⅱ类油组分来源于中二叠统下乌尔禾组(P_(2)w)烃源岩,Ⅲ类油组分来源于两套烃源岩的混合原油。含油储集岩连续抽提组分和原油样品成熟度变化大,从生油窗早期至晚期,成熟度严重影响了油源分子指标的应用效果。本文提出,应用成熟度分子指标与油源分子指标绘制交会图,可以对成熟度相近的连续抽提组分和原油样品进行油源对比。例如,应用C_(30)藿烷/n-C_(21)与Pr、Ph、伽马蜡烷、Ts、C_(29)Ts、C_(30)重排藿烷和C_(20)、C_(21)和C_(23)三环萜烷与n-C_(21)的比值绘制交会图,可以将Ⅰ、Ⅱ和Ⅲ类油组分有效区分开来,为玛湖凹陷油源对比研究提供了一个新方法。During the past 10 years,a new type of oil reservoirs have been found in the conglomerates of the Mahu Sag,which are continuously distributed on a massive scale.However,the sources of oils in the Mahu Sag and the Ke-Bai fault zone in the western border of the sag remain unclear.Therefore,determination of the sources and oil charging processes for oil reservoirs in this region is very useful for oil exploration.In this study,free oils a1 and a2,adsorbed oil b and conclusion oil c were obtained by sequential extraction from 21 oil-containing reservoir rocks from the southern and western slopes of the Mahu Sag.Quantitative GC,GC-MS,and GC-IRMS analyses were conducted on these sequential extracts,as well as 13 oils from the same boreholes of some of the aforementioned reservoir rocks.The 13 oils and sequential extracts from the 21 reservoir rock samples are classified into three groups,i.e.,groupsⅠ,Ⅱ,andⅢ,which were derived from source beds within the Lower Permian Fengcheng Formation(P_(1)f),Middle Permian Lower Wuerhe Formation(P_(2)w),and both aforementioned formations,respectively,on the basis of carbon isotopes of individual n-alkanes.These sequential extracts and oil samples have a wide maturity range from the early to late oil generative window,making the routine molecular facies parameters ineffective in assessing of the oil sources of these samples.GroupsⅠ,Ⅱ,andⅢfor the sequential extracts from the 21 reservoir rocks and 13 oils,which were classified on the basis of carbon isotopes,can be sufficiently distinguished in plots of C_(30) hopane/n-C_(21) ratio versus the ratios of Pr,Ph,Ts,C_(29) Ts,C_(30) hopane,C_(20),C_(21),and C_(23) tricyclic terpanes to n-C_(21).This approach can be very useful for oil source assessment in the Mahu sag.

关 键 词：玛湖凹陷 砾岩大油区 连续抽提 单体烃C同位素 分子地球化学 

分 类 号：P593[天文地球—地球化学] P618.13[天文地球—地质学]