【作者】 谢渊；

【导师】 刘家铎； 王剑； 罗建宁；

【作者基本信息】 成都理工大学 ， 古生物学与地层学， 2002， 博士

【摘要】 世界上很大一部分油气资源赋存于湖相沉积盆地中，特别是我国具有陆相湖盆成油的显著特点。因此，湖盆的地质研究一直是地学研究的一个重要内容，其中湖盆层序地层学更是一个国际性的研究课题，也是当今地学中争议极大的、需要深入探讨的一个重要理论难点；而鄂尔多斯湖盆富县探区延长组层序地层与储层的深入研究已成为该区油气勘探取得重大突破的一个紧迫而又现实的要求。鉴于此，本论文选题“鄂尔多斯盆地富县探区延长组层序地层与储层研究”，应用陆相层序地层学、储层沉积学、储层地质学及微量元素地球化学等理论和测试手段，系统研究了富县探区延长组沉积相、层序地层及储层特征。 论文在富县探区首次应用陆相层序地层学的观点和方法，把延长组划分为6个三级层序，平均时限4.5Ma，各层序由三角洲与湖泊相砂、泥岩沉积组成，主要在低位体系域和高位体系域发育水下(上)分流河道和河口砂坝砂岩储层．延长组层序地层的形成与演化主要受控于当时缓慢的构造沉降、温湿气候、陆源碎屑物源供给及湖平面升降等地质因素。 综合运用重矿物、古水流方向及沉积相展布等方法，对沉积物源系统的研究得出，晚三叠世延长期富县探区存在东南部与东-北东部两个方向的物源供给，物源供给的变化控制了本区延长组层序地层和沉积相的发育与展布。 初次通过泥岩常、微量元素测试资料和沉积学分析得出，延长期富县探区湖泊水体属于淡水-微咸水，微量元素含量及其比值在剖面上的变化对延长期湖平面升降和气候的演变具有良好的响应，湖平面升降、气候演变对层序地层的发育有着直观而又重要的影响。 系统的储层特征研究表明，该区延长组储层成因类型主要为三角洲前缘水下分流河道、河口砂坝及三角洲平原水上分流河道微相细粒长石砂岩、粉砂岩；储层岩石经历了压实，胶结，溶蚀等成岩作用，历经早成岩机械压实和化学压溶孔隙缩小期、晚成岩A亚期溶蚀作用孔隙扩大期及晚成岩A亚期(B亚期)胶结充填孔隙缩小期三个成岩-孔隙演化阶段；储层物性总体上具有较低孔渗、低孔渗的特点，孔隙类型主要为粒间溶孔、残余粒间孔隙、粒内溶孔、晶间孔及晶间溶孔，裂缝不发育，储集岩排驱压力和中值压力较高，孔隙结构类型以细小孔-微孔隙，微细喉-微喉型为主。 储层控制因素的综合分析认为，沉积微相和成岩作用是控制或影响该区储层发育与展布的主要地质因素。三角洲前缘水下分流河道、河口砂坝、远砂坝及三角洲平原水上分流河道微相决定了储集岩的发育，分布及原始物性条件；水下(上)分流河道微相砂体厚度大、物性和孔隙结构好，次之为河口砂坝微相砂体，远砂坝微相砂体储集性较差，而分流伺湾微相砂体物性和孔隙结构最差。成岩作用是形成本区延长组压实-胶结型低孔渗储层的主要原因，强烈的压实，压溶及晚期碳酸盐胶结作用极大地降低了岩石的孔渗性，而较晚、较弱的有机酸溶蚀作用未能明显改善储层，极弱的构造破裂作用没能有效地提高储层渗透性。 首次通过系统的储层评价与预测提出，长8、长6、长2油层组是富县探区延长组三套主要储集层，其中长2油层组储层最发育，长6次之，长8相对较差；富县F30井-ZF3井-ZF4井-ZF2井区与直罗-张村驿F2井-ZF22井-ZF26井区是该区的两个有利储层分布区块，具有储层沉积微相有利、储层砂岩富集，厚度较大、物性较好、油气显示丰富等有利条件，是两个有利的油气勘探区块。更多还原

【Abstract】 Much of the oil and gas resources reside in lake basins in the world including China. The approaches of the geology, especially sequence stratigraphy of lake basins are interpreted to be most important and much debated. Exemplified by the Ordos Basin, the sedimentary facies, sequence stratigraphy and hydrocarbon reservoirs in the Fuxian prospect area are examined in detail in the present paper on the basis of reservoir sedimentology, continental sequence stratigraphy, reservoir geology and trace element geochemistry.The Yanchang Formation is divided, for the first time, into six third-order sequences, each with an average time duration of about 4.5 Ma. The single sequence is composed of deltaic and lacustrine sandstones , siltstones and mudstones. The subaerial and subaqueous distributary channel and channel-mouth bar sandstone reservoirs are well developed mainly in the lowstand and highland systems tracts. The formation and evolution of the sequence stratigraphy of the Yanchang Formation are governed by slow tectonic subsidence, warm humid climates, sediment supply and lake-level fluctuations.The integrated study of heavy mineral, palaeocurrent direction, and sedimentary facies distribution has disclosed that the detritus are derived chiefly from the southeast and east-northeast during the deposition of the Yanchang Formation in the Late Triassic. The variations in the palaeocurrent directions have consequences for the development and distribution of the sequence stratigraphy and sedimentary facies of the Yanchang Formation. The major and trace element analyses of the mudstones from the Yanchang Formation also show that the lake waters would be freshened to brackish. The variations in trace element contents and ratios may hold up a mirror to the lake-level fluctuations and climatic changes, which, in turn, have exerted a direct and important effect on the sequence stratigraphic development.Collectively, the reservoir rocks from the Yanchang Formation consist dominantly of the delta front subfacies subaqueous distributary channel and channel-mouth bar microfacies and delta plain subfacies subaerial distributary channel microfacies fine-grained feldspar sandstones and siltstones. The reservoir rocks have been subjected to three stages of diagenetic and porosity evolution: (1) the porosity reduction by the mechanical compaction and chemical pressure solution during the early diagenetic stage; (2) the porosity increase by the dissolution during the A substage of the late diagenetic stage, and (3) the porosity reduction by the cementation and filling during the B substage of the late diagenetic stage. In general, they have low porosity and permeability.The porosity types consist of residual intergranular porosity, intergranular solution openings, intragranular solution openings, intercrystal porosity and intercrystal solution openings. The cracks and fissures are commonly less developed. The driving pressures and median pressures are relatively high. The porosity textures include fine- to microporosity and fine-throat to microthroat types.The examination of the controls of the reservoir rocks indicates that the sedimentary microfacies and diagenesis are the principal geological factors controlling the development and distribution of the reservoir rocks in the study area. The rock types comprise the delta front subfacies subaqueous distributary channel, channel-mouth bar and distal bar microfacies, and delta plain subfacies subaerial distributary channel microfacies sandstones and siltstones. As for the reservoir quality, the subaqueous (subaerial) distributary microfacies channel sandstones are the first, the channel-mouth bar microfacies sandstones come second, the distal bar microfacies sandstones is the third, and the last one is the interdistributary bay microfacies sandstones. The intense compaction, pressure solution and late carbonate cementation are responsible for the reduction of the porosity and permeability of the reservoir rocks. Both the later weak organic acidic dissolution and stru更多还原