摘要:侏罗系是四棵树凹陷油气勘探的重要目的层，进一步查明侏罗系油气来源，落实生烃中心，对今后勘探选区选带十分重要。本文在对侏罗系烃源岩有机质丰度、类型、成熟度以及埋藏史和生烃潜力分析的基础上，开展了原油分类、油源对比及油气运移分析研究。结果表明，下侏罗统八道湾组主要发育湖相泥岩和河沼—三角洲相煤系两类烃源岩，有机质类型较好，丰度较高，主体处于低成熟—成熟阶段，局部演化程度高，生气潜力大；八道湾组具晚期快速埋藏生烃特点，四棵树凹陷主体以生油为主；生物标志化合物特征及其指纹对比发现，中侏罗统头屯河组含A、B两类原油，A类原油主要源自八道湾组中段湖相泥岩，生油母质以低等水生生物为主，B类原油的生油母质主要为高等植物，应主要来自八道湾组上、下段煤系地层；据三环萜烷/五环三萜烷和重排甾烷/规则甾烷反映出的运移效应推断，卡因迪克构造带以南至西湖构造之间存在八道湾组烃源岩的生油中心，是卡6井区和西湖1井头屯河组原油的主要供烃区，该区域是今后侏罗系勘探的有利区带。
关键词: 四棵树凹陷/
八道湾组/
头屯河组/
烃源岩/
油源对比/
生物标志化合物
Abstract:Since the Jurassic system is an important target strata for oil and gas exploration in theSikeshu Depression, the further investigation on the origin of Jurassic oil and gas and theidentification of the hydrocarbon generating center is of great significance for the selection ofexploration areas and zones. Based on the analysis of organic matter abundance, types, maturityof the Jurassic source rocks as well as their burial history and hydrocarbon-generating potential,the crude oil classification, oil-source correlation and hydrocarbon migration were fullydiscussed in this study. The result shows that two types of source rocks are developed in theLower Jurassic Badaowan Formation, i. e. the lacustrine mudstone and the coal measuresdeposited in delta facies. These source rocks are primarily within low-mature to mature stages,characterized by favorable organic types and abundance and renders high abundance, with partof them entering the highly mature stage, indicating high potential for gas generation. TheBadaowan Formation is characterized by rapid burial for hydrocarbon generation at the laterstage and oil was predominantly generated in Sikeshu Depression. Biomarker fingerprintsindicated that two types of crude oil（type-A and type-B）were observed in the Middle Jurassic Toutunhe Formation. Type-A oil was originated from the lacustrine mudstones in the middleBadaowan Formation whose organic matters are mainly composed of lower aquatic organism.Type-B oil was originated from the coal measures in the upper and lower Badaowan Formationwhose organic matters are mainly composed of higher plants. The migration effect inferred fromtricyclic terpane/pentacyclic triterpane and diasteranes/regular sterane ratios showed that an oilgenerating center of Badaowan Formation may develop between the south of Kayindikestructural belt and Xihu structure, being the primary source for oils from Toutunhe Formationin the well block Ka-6 and well Xihu-1. As a result, this area is a favorable exploration field forJurassic petroleum system in future.
Key words:Sikeshu Depression/
Badaowan Formation/
Toutunhe Formation/
Hydrocarbon source rocks/
Oil source correlation/
Biomarkers
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