川北中、下侏罗统烃源岩重排藿烷组成变化与油源对比  

Compositional Variations and Oil-source Implication of Rearranged Hopanes from the Middle-Lower Jurassic Source Rocks in the Northern Sichuan Basin

作　　者：朱扬明[1] 郝芳[2] 邹华耀[3] 李平平[3] 胡东风[4] ZHU YangMing;HAO Fang;ZOU HuaYao;LI PingPing;HU DongFeng(School of Earth Sciences,Zhejiang University,Hangzhou 310027,China;School of Geosciences,China University of Petroleum(East China),Qingdao,Shandong 266580,China;College of Geosciences,China University of Petroleum(Beijing),Beijing 102249,China;SINOPEC Exploration Company,Chengdu 610041,China)

机构地区：[1]浙江大学地球科学学院,杭州310027 [2]中国石油大学(华东)地球科学与技术学院,山东青岛266580 [3]中国石油大学(北京)地球科学学院,北京102249 [4]中国石化勘探分公司,成都610041

出　　处：《沉积学报》2022年第4期1137-1150,共14页Acta Sedimentologica Sinica

基　　金：国家科技重大专项(2017ZX05005-003-003)。

摘　　要：利用色谱—质谱定量分析技术,对40余个取自四川盆地北部石龙场和元坝地区不同成熟度的中、下侏罗统湖相烃源岩和原油样品进行分析,以此揭示其重排藿烷组成和分布的变化特征,并进行精细的油源对比。研究结果表明,不同成熟度的烃源岩中重排藿烷的丰度相差悬殊。石龙场地区Ro值为0.8%~1.0%的中侏罗统千佛崖组和下侏罗统自流井组大安寨段泥岩中,各类重排藿烷异常丰富,检出了17α(H)-重排藿烷、18α(H)-新藿烷和早洗脱重排藿烷3个完整碳数系列。它们的相对含量大都数倍于规则藿烷,是该层系烃源识别的分子标志。而在相邻的元坝地区相带、岩性相近的这两层段高成熟(Ro值主要在1.4%~1.9%)烃源岩中,藿烷类化合物出现异常变化,重排藿烷的相对含量很低,可能与干酪根在高热演化阶段生成的规则藿烷比例较高有关。烃源岩中高丰度重排藿烷并不取决于其绝对含量的高低,而在于它们相对于规则藿烷的富集。弱氧化的沉积环境是导致重排藿烷相对富集的一个重要原因,而有机质生源中的细菌组成可能更是一个关键因素。当烃源岩达到高成熟阶段时,藿烷类化合物的组成和分布不再受控于热化学动力学机制,各类重排藿烷均按一定比例分布,基本失去了其地球化学属性。区内中、下侏罗统原油中重排藿烷的组成和分布也随热演化程度而变化。它们在成熟原油中极丰富,而在高成熟原油中则很少,与烃源岩存在对应关系。经油—岩对比,认为这些原油来源于所在层位的烃源岩。Over 40 lacustrine source rock and oil samples with different maturities collected from the middle-lower Jurassic strata in the Shilongchang and Yuanba regions of the northern Sichuan Basin were analyzed using GC-MS(gas chromatography-mass spectrometry)to characterize the compositional variations of rearranged hopanes and carry out a genetic correlation between the oils and the source rocks.The results indicate the rearranged hopanes show a great difference in abundance for the different mature source rocks.The mudstones with Ro values ranging from 0.8%to 1.0%in the middle Jurassic Qianfoya Formation and the Da’anzhai member of the lower Jurassic Ziliujing Formation in the Shilongchang region are extremely enriched in three series of rearranged hopanes,i.e.,17α(H)-diahopanes,18α(H)-neohopanes,and early-eluting rearranged hopanes with a full carbon number member.These compounds are present several times in relative concentrations as regular hopanes and can serve as a molecular indicator for the identification of hydrocarbons from the middle-lower Jurassic source rocks.In contrast,the hopanoids from over-mature source rocks(Ro mostly in 1.4%-1.9%)with similar depositional facies and lithology in the Yuanba region are found to change abnormally.Their rearranged hopanes exhibit a low relative abundance,possibly as a result of more regular hopanes generated from kerogen at a high maturity level.Enhanced rearranged hopanes in the source rocks are attributed to the relative enrichment of these compounds with respect to regular hopanes,rather than their high absolute concentration.A sub-oxic depositional environment could favor the formation of these compounds,while the bacterial component in a biological source may be of critical importance.The constitution of hopanoids appears not to be controlled by thermodynamic processes at high thermal maturity,and rearranged hopanes show a highly similar molecular distribution with the deprivation of their geochemical proprieties.The composition and distribution of rearranged

关 键 词：重排藿烷 烃源岩 原油 油源对比 四川盆地 

分 类 号：P618.13[天文地球—矿床学]