【作者】 杨斌虎；

【导师】 罗静兰；

【作者基本信息】 西北大学 ， 矿产普查与勘探， 2009， 博士

【摘要】 首次对鄂尔多斯盆地上古生界二叠系下石盒子组盒8与山1段砂岩碎屑锆石开展了LA-ICPMS微区原位U-Pb同位素定年与物源示踪研究,准确厘定了盒8与山1段沉积期的物源区、对应不同峰期年龄的源区母岩时代与母岩性质。利用取芯井岩心相标志,结合测井相研究,建立了盒8与山1段的沉积体系与沉积相模式,研究了各种沉积微相在纵向上与平面上的展布特征。通过岩心观察、铸体薄片鉴定、X-射线衍射分析、粒度分析、阴极发光、扫描电镜、物性分析与毛细管压力测试、包裹体测温等分析测试手段,对盒8、山1段砂岩储层的岩石学特征、孔隙类型及其组合、孔隙喉道及其配置等孔隙结构微观特征及其在纵向上与平面上的分布规律进行了精细研究。探讨了源区母岩性质、沉积相与水动力条件、成岩作用等对形成优质储层的影响。研究结果显示,鄂尔多斯盆地山1与盒8地层沉积期的物源主要自北部阴山地块基底岩系中早元古代晚期(2300Ma～1800Ma)孔兹岩带和早元古代早期(2300Ma～2600Ma)TTG片麻岩；其次为阴山地块泥盆纪-石炭纪(300-400Ma)的花岗岩及火山岩；鄂尔多斯盆地东部物源中有一部分来自阴山地块东北部太古代古老变质岩系。盒8及山1段储层砂岩的类型、骨架矿物成分与重矿物组合及其平面分布规律主要受源区母岩地层时代与母岩性质的控制,也是造成储层非均质性的内因。物源方向、母岩地层与母岩性质、沉积条件同时控制了沉积相带与砂体的空间展布特征。山1沉积期,研究区以曲流河三角洲平原亚相沉积环境为主,南部为曲流河三角洲前缘亚相沉积环境。垂向剖面上分流河道二元结构沉积同等发育,砂体以带状分布为主,局部成连片状分布。盒8沉积期,北部蚀源区物源供给更充足,水动力条件更强,形成北部为冲积平原、其余地区为交织状分流河道为特征的浅水辫状河控三角洲平原亚相沉积。河道的频繁改道致使多期河道彼此叠置形成巨厚砂体,形成盒8特有的连片状砂质与含砾砂质沉积。沉积相与水动力条件不仅控制了砂体展布特征,同时影响了砂岩的结构成熟度,并由此决定了砂岩的原始孔隙特征。不同的砂岩类型其成岩作用的路径及成岩产物不同,致使各砂岩类型中的胶结物成分及其产状、孔隙类型及其发育程度、孔喉组合与微观孔隙结构特征存在一定差异,直接导致各砂岩类型不同的储集性能与储层的非均质性。研究区以石英砂岩的储集性能最好,岩屑砂岩的物性较差,岩屑石英砂岩的物性介于两者之间。本研究不仅解决了鄂尔多斯盆地上古生界源区与母岩时代问题,而且,对于深入理解鄂尔多斯盆地北部物源区特征、沉积特征与构造演化,预测上古生界天然气有利勘探期及促进鄂尔多斯盆地天然气资源的勘探与开发均具有重要的理论意义和实际意义。更多还原

【Abstract】 It is the first time to construct age spectrum of detrital zircons in the He 8 and Shan 1 Group of the Low Permian, Upper Paleozoic in Ordos basin, and research on chronology and characteristics of parent rocks in provenance tracing, using techniques of LA-ICPMS in situ U-Pb isotopic dating and trace element analysis of detrital zircons, accompanied with comparative study on petrology of skeleton and heavy minerals and their assemblages in the sandstones, reconstruction via magnetic fabric paleomagnetic original orientation. The depositional system and sedimentary facies models for the He 8 and Shan 1 Group are constructed, temporal and spatial distribution of depositional microfacies are investigated in this paper, base upon solid research on facies indicators from cores, study on well log facies accompanied by regional depositional background. Characteristics of petrology, types of pores and their assemblage, size of pore and throat and their coordination relationship, as well as the horizontal and vertical distribution of these pore structure micro features, based on observation of drilling cores, identification of thin-sections, X-ray diffraction (XRD)of clay minerals, cathodoluminescence image and electron scan micrpscope (ESM) analysis, sandstone grain, porosity, permeability and capillary pressure measurement of the sandstones, homogenization temperature of inclusions in authigenic cements. Impact of parent rock characteristics in provenence, depositional facies and hydrodynamic conditions and diagenesis on formation and development of excellent reservoir is also discussed in this study.Research result indicates that the Early Proterozoic Khondalite (2300Ma-1800Ma) zone and TTG gneisses (2300Ma-2600Ma) in the Yingshan Block located in north of the Ordos basin was the major provenence, and subordinate ones came from the Devinian-Carboniferous (300Ma-400Ma) granites and volcanic rocks. Part of the sedimentary sources in the eastern Ordos may derived from the Archean old metamorphic rock series in the northeastern Yingshan Block.Types of sandstones, skeleton and heavy minerals and their horizontal distribution of He 8 and Shan 1 group are controlled by chronology and stratigraphy, and characteristics of parent rocks, and the latter also resulted in heterogeneity of reservoir internally. Direction of sedimentary sources, stratigraphy and characteristics of parent rocks, depositional condition controlled the spatial distribution of sedimentary facies and sandbodies. Meandering deltaic plain sedimentary environment was domineering in the study area with the deltaic front in the southern part during the Shan 1 period. "Two-element structure" of the distributary channel sediment developed equally in vertical section. Horizontal distribution of zonal sand bodies dominated and sheet sand bodies subordinated occurred. While during the He 8 period, richer sources from the north provenence and more intense hydrodynamic condition compared with the Shan 1 phase resulted in alluvial plain in the north part, and shallow-water braided deltaic plain environment in vast region of study area, which was characterized by multiple network of distributary channels.Distributary channel course’s frequent. changes resulted in multi-period channels overlapped, thus joint-sheet sandbodis horizontally and very thick sand body vertically occurred. Depositional facies and hydrodynamic condition controlled distribution of the sand bodies, influenced the structural maturity of sandstones, thus lead to the primary pore features of sandstones.Different sandstone types contributed to different diagenetic paths and various authigenic products, thus resulted in deviation in cements and their occurrences, pore types and their development, pore-throat assembledges and different mico pore structures, and this in turn induced heterogeneity and various reservoir quality. The excellent reservoir for natural gas is quartzarenite with litharenite poor ones, quality of sublitharenite is between the former and the latter.This study may not only answer problem of Upper Paleozoic provenance and parent chronology of the Ordos basin, but is very important theatrically and practically in a thorough exploration in characteristics of provenance in the northern part and deposition and tectonic evolution of the Ordos basin, and predict prospecting natural-bearing area and promote exploration and development for hydrocarbon resources in the Ordos basin.更多还原