【作者】 李红敬；

【导师】 解习农；

【作者基本信息】 中国地质大学 ， 能源地质工程， 2009， 硕士

【摘要】 在世界范围内,海相地层是一种非常重要的油气生储层,世界可采储量的61%都产自海相地层。相比之下,中国的海相地层占大陆沉积岩面积的40%,而在海相地层中的油气发现却相对很少。因此,中国海相碳酸盐岩地层应当具有相当大的油气勘探潜力。前人的研究已经证实,二叠系是中国南方重要的海相烃源岩层。本论文以扬子地区二叠系三个典型剖面为解剖对象,以碳酸盐岩露头层序地层为理论指导,采用微量元素、碳氧同位素地球化学测试分析,结合野外实际考查和室内薄片观察,系统开展了二叠系典型剖面沉积相及层序地层研究,并探讨了层序构成基本特征。在层序地层分析及前人对本区生境型研究的基础上,结合残余有机碳测试,探讨扬子地区二叠系有机质富集规律,进而判识典型剖面优质烃源岩富存层位,并初步探讨了海相烃源岩的地球生物学判识方法,最后总结了研究区优质烃源岩的发育模式。主要认识及成果:1、根据野外记录描述和室内薄片观察,对典型剖面二叠纪地层进行了沉积相的划分,总结了各沉积相的地球化学特征。Co、Ba、V、Rb等具有指相意义的元素,沉积相越靠近深水环境,Co、Ba、V、Rb平均丰度越大,而Sr/Ba值从台地相到盆地相整体有降低趋势。贵州罗甸剖面从台地前斜坡相→陆棚相→斜坡相→盆地相,REE值逐渐增大。贵州罗甸剖面各沉积相稀土元素配分模式存在明显的Ce异常。总结了广元地区、华蓥山地区和贵州罗甸地区碳酸盐岩沉积模式。广元地区和华蓥山地区碳酸盐台地边缘生物礁不发育,台地前斜坡相发育不好,浅海陆棚与盆地之间的斜坡不发育。贵州罗甸地区碳酸盐岩沉积主要位于斜坡相,台地前斜坡相和斜坡相发育良好。2、通过对研究区野外剖面考查、碳氧同位素和微量元素测试,深入研究层序特征的基础上,在广元剖面二叠系识别出了9个三级层序,重庆华蓥山剖面下二叠统识别出了6个三级层序,贵州罗甸剖面识别出了7个三级层序。详细讨论了各层序和体系域的构成特征:依据岩性组合特征总结出8种准层序基本组构型式;讨论了碳酸盐台地、斜坡沉积、盆地沉积三种沉积背景下层序构成特征及体系域内的地球化学元素分布特征。从海侵体系域到高位体系域,REE及稀土元素总量（∑REE）逐渐降低;海侵体系域的（La/Yb）_N大于高位体系域,表明海侵体系域的轻稀土的富集程度大于高位体系域。在此基础上进行了层序地层对比,建立了下二叠统等时层序地层格架;讨论了研究区层序发育的主要控制因素包括:海平面变化、构造沉降、气候、沉积物供给等。其中海平面变化及气候为主要控制因素。3、通过研究典型剖面的有机质富集特征得出:有机质富集与岩性密切相关,薄层硅质岩与硅质页岩互层或纹层状灰岩与页岩互层层是有机质最为富集的岩性,其中灰岩随着层理厚度增大而有机质明显降低,纹层和薄层灰岩TOC最高;二叠系残余有机质分布与生境型关系密切,优质烃源岩发育的最有利生境型类型是Ⅳ₂和生境型Ⅴ₂,再次为生境型Ⅲ;层序的发育对有机质的富集程度的影响,TST的有机质明显要比HST的有机质富集程度要高。广元上寺剖面可以成为优质烃源岩的层位主要有三套:栖霞组的下部、茅口组顶部和大隆组中部;华蓥山剖面有可能成为有效烃源岩的层位有2层,分别位于茅口组中部和栖霞组下部,贵州罗甸剖面二叠系地层不存在有效烃源岩层段。4、本文采用TOC＜0.3%为非烃源岩,TOC＞1.5%为优质烃源岩的3级判别方案,发现已知烃源岩与各种地球生物学指标之间存在以下关系:①从各种与古生产力相关的生源元素和与埋藏环境相关的地球化学指标来看,Cr、Ni、Cu、Zn、Ba、Mo、U等元素的平均含量以及指示氧化还原条件的Ni/Co、V/Cr、V/（V+Ni）等从非烃源岩（TOC＜0.396）到一般烃源岩（0.3%＜TOC＜1.5%）到优质烃源岩（TOC＞1.5%）均显示规律性变化,除V/（V+Ni）比值变化不明显外,其它元素和比值均明显增大,其中优质烃源岩上述元素含量和元素比值明显增大。②对比不同岩性（灰岩、硅质岩和泥页岩）中各种元素含量变化发现,就优质烃源岩而言,泥页岩中Ni、Cu、Cr、Ba、Mo、U元素含量明显高于灰岩和硅质岩,而Ni/Co和V/Cr比值则比较接近;灰岩中Ni、Cu、Cr、Ba元素含量与硅质岩相近,但Mo、U元素含量明显小于硅质岩。就非烃源岩（TOC＜0.3%）和一般烃源岩（0.3%＜TOC＜1.596）而言,硅质岩中多数元素含量与灰岩中元素含量相近,而硅质岩中Cr含量明显大于灰岩。5、在典型剖面有机质分布特征的基础上总结了优质烃源岩发育模式。生烃母质生物能否发育及其丰度为优质烃源岩发育的必要条件,保存条件也是控制优质烃源岩发育的重要因素。深部流体和上升流作用是川西北地区优质烃源岩产生高古生产力的重要影响因素。更多还原

【Abstract】 Marine deposits are very important hydrocarbon source beds and reservoirs in the world. There are 61%available reserve come from marine deposits.40%depositional area is coverd by marine sediments in China,but a few hydrocarbon pool is explored in marine sediments compared with worldwide.Hereby,marine deposits have significant hydrocarbon exploration potential in China.The previous research shows that Permian system is one of the most important marine resource rocks in Lower Paleozoic in south China.In this paper 3 typical Permian profiles in Yangtze region have been studied.Taking the sequence stratigraphy of carbonate rock outcrops as theory guidance,geochemical testing of trace elements as well as carbon and oxygen isotope is used to systematically study the sedimentary facies and the sequence stratigraphy of the typical Permian profiles,and to discuss the basic characteristics of sequence achitectures,with the integration of field work and the microscope observation of thin sections.On the basis of sequence stratigraphy analysis and the previous studies involved with the habitat types in this area,and with the integration of the results from residual organic carbon testing,organic matter enrichment of the Permian in Yangzi region is discussed,in turn the intervals with high quality source rocks developed on the typical profiles have been identified.A preliminary study on the identification for marine source rocks is made by Geo-biology methods in this paper.Finally,the development model for high quality source rocks is concluded in the study area.The main results and conclusions are as follows:1.According to the observation of fieldwork and thin sections,depositional facies in 3 typical Permian profiles are divided,and the geochemical characteristics in each depositional facies are summarized.The average contents of Co、Ba、V、Rb showing distinct marks for depositional facies become higher toward deep marine environments,but Sr/Ba ratio decrease from platform facies to basin facies.In the Luodian profile,total REE(∑REE) increases gradually from fore-platform,outershelf,slope to basin facies,and obvious Ce anomaly in REE Patterns of every faces has been observed. Carbonate sedimentary models in Guangyuan,Huayingshan and Luodian areas have also been summarized.Carbonate platform deposits are dominated without reef in the Guangyuan and Huayingshan sections,where a few continental slope deposits between outershelf and basin facies.While carbonate slope facies are developed well in the Luodian area.2.According to the field description and the test results of carbon and oxygen isotope as well as trace elements,the Permian deposits in Guangyuan,Huayingshan and Luodian were divided into 9 third-order sequences,6 third-order sequences and 7 third sequences,respectively. The achitecture characteristics of each sequence and system tract are discussed individually in detail:Based on lithologic association,8 basic subsequence achitecture patterns were summarized;and the characteristics of the sequence architecture as well as the distributions of geochemical elements in the system tract were described in the sedimentary backgrounds of carbonate platform,slope deposit and basin floor respectively.Rare earth elements(REE) and total REE(∑REE) gradually reduce from the transgressive systems tract to the highstand systems tract;the La/Yb ratio in the transgressive systems tract is higher than that in the highstand systems tract,which indicates a higher enrichment degree in the former one than the latter.Then,the stratigraphic sequence correlation of the Permian systerm were discussed,and the isochronous stratigraphic framework of the lower Permian was established;the main controlling factors for sequence development,in our research area,were also concluded as sea-level change,tectonic subsidence,climate conditions,sediment supply,and so on,of them sea-level change and climate condition are taken as the main controlling factors.3.Through the analysis of those typical profiles,the results indicate that(1) the organic matter enrichment is closely related to the lithology:the organic matter is most enriched in thin layer siliceous rocks interbedded with siliceous shale,or laminated limestone interbedded with shale,and the organic matter decreases apparently with the increasing thickness of beddings in limestone,the laminated limestone and the thin layer limestone has the highest TOC;(2) the distribution of residual organic matter in the Permian shows a close relationship with the habitat types,and high quality source rocks are supposed to be most likely developed in habitat types ofⅣ2 andⅤ2,then the habitat type ofⅢ;(3) the sequence development has certain influences on the organic matter enrichment,for example,the organic matter enrichment degree in TST is obviously higher than that in HST.In the Shangsi profile in Guangyuan,three intervals of high quality source rocks are mainly identified as the lower Qixia group,the top Maokou group and the middle Dalong group;In the Huayingshan profile in Chongqin,two intervals of high quality source rocks are mainly identified as the middle Maokou group and the lower Xixia group;but in Luodian profile in Guizhou,high quality source rocks are apparently absent.4.The following relationship between known source rock and the Geo-biological indexes has been discussed adopting the discriminant value with the less than 0.3%TOC in non-hydrocarbon source rock and more than 1.5%in high quality source rocks:(1) the average contents of Cr、Ni、Cu、Zn、Ba、Mo、U,as proxies for pre-productivity,and the ratios of Ni/Co、 V/Cr,as proxy for sedimentary environment,reveal a regular change from non-hydrocarbon source rocks to high quality source rocks.Significant increasing trends are shown with these contents as well as ratios(the ratio of V/(V+Ni) is an exception,whose change is not so obvious as others);(2)Contrasting levels of the above elements and ratios in different lithology(limestone, siliceous rocks and mud),in high quality source rocks,the contents of Ni、Cu、Cr、Ba、Mo、U in mudstone is much higher than those in limestone and siliceous rocks,however,the ratios of Ni/Co and V/Cr among them are similar;the contents of Ni、Cu、Cr、Ba between limestone and siliceous rocks are close,but the contents of Mo、U is much less than these of siliceous rocks.In non-hydrocarbon source rock and common source rock,most of element contents in siliceous rocks are similar to these in limestone,but the content of Cr is obviously more than in limestone.5.On the base of organic matter distribution in the typical profiles,the development model of high quality source rock is summarized.Occurrence of hydrocarbon-generating organisms and its abundance are essential conditions for the formation of high quality source rocks,and preservation condition is also another important factor.Deep fluid and upwelling activities are throught to be main reasons to result in the formation of high ancient productivity for high quality source rocks in northwestern Sichuan.更多还原