柴西缘干柴沟地区古近系下干柴沟组物源分析与沉积特征

发布时间：2018-09-19 17:24

【摘要】：柴达木盆地古近系渐新统下干柴沟组是西部油田主要的产油层,蕴涵巨大的油气勘探与开发潜能。详细研究其物质来源、沉积相展布等特征对砂体空间分布研究具有重要意义。本论文在前人研究成果上,结合野外典型露头观察、剖面实测、室内样品分析测试及测井曲线特征,以统计资料、作图对比分析等为研究方法,对柴西地区下干柴沟组沉积特征及物源特征进行综合研究,明确干柴沟地区下干柴沟组的物源方向、物源区构造背景及母岩性质,从宏观角度揭示研究区内下干柴沟组的沉积相类型、沉积相平面展布,为柴西地区下干柴沟组砂体展布研究提供依据。研究区下干柴沟组主要为一套碎屑岩沉积。其砂岩类型主要为长石岩屑砂岩、岩屑长石砂岩、岩屑砂岩。砂岩中岩屑含量较高,为23%-57%,碎屑颗粒磨圆度主要为棱角状-次棱角状,分选较差,具有低成分成熟度及低结构成熟度特征。物源分析表明:干柴沟剖面下干柴沟组物源来自阿尔金山西段索尔库里方向,碎屑岩岩屑主要来自阿尔金山中出露的元古界、奥陶系变质岩,物源区构造环境为过渡型多岛洋盆环境,源岩具有多样性,主要是来自上地壳的花岗岩、长英质火山岩及少量中、基性岩类,沉积环境为弱氧化-弱还原环境,有利于有机质富集、保存。下干柴沟组岩石学特征、沉积构造、典型井测井曲线等特征表明:下干柴沟组主要发育有冲积扇相、扇三角洲相及湖泊相等沉积相类型。干柴沟剖面下干柴沟组为湖侵背景下形成的退积型扇三角洲相沉积。沉积相(沉积微相)连井分析表明:下干柴沟组沉积期,研究区沉积格局以周围被阿尔金山前及祁漫塔格山前冲积扇包围,向沉积中心逐渐过渡为内陆湖泊相沉积为特征。在此基础上建立了该时期的冲积扇-扇三角洲-湖泊沉积模式。
[Abstract]:The Lower Ganchaigou formation of Paleogene in Qaidam Basin is the main oil-producing zone in the western oil field, which contains great potential for oil and gas exploration and development. It is of great significance to study the spatial distribution of sand bodies by studying its material source and distribution of sedimentary facies in detail. In this paper, based on the previous research results, combining the field typical outcrop observation, profile measurement, indoor sample analysis, testing and logging curve characteristics, taking statistical data, drawing contrast analysis and other research methods as the research methods, The sedimentary characteristics and provenance characteristics of Xiaganchaigou formation in western Qaixi area were studied, and the source direction, source tectonic setting and parent rock properties of the Lower Ganchaigou formation in Ganchaigou area were determined. The types of sedimentary facies and the distribution of sedimentary facies in the Xiaganchaigou formation are revealed from the macroscopic point of view, which provides the basis for the study on the distribution of sand bodies of the Lower Ganchaigou formation in the western Qaixi area. The Xiaganchaigou formation in the study area is mainly composed of a set of clastic deposits. The sandstones are mainly feldspathic sandstone, lithic feldspathic sandstone and lithic sandstone. The content of rock debris in sandstone is high, ranging from 23 to 57. The grinding roundness of clastic grain is mainly angle-sub-angle-shaped, and the separation is poor, with the characteristics of low compositional maturity and low structural maturity. The provenance analysis shows that the Ganchaigou formation in the Ganchaigou section is derived from the Solkuri direction of the western section of the Altun, and the clastic lithoclasts are mainly from the Proterozoic, Ordovician metamorphic rocks, which are exposed from the middle of the Altun Mountains. The tectonic environment of the provenance area is transitional multi-island oceanic environment, and the source rocks are diversified, mainly from granites in the upper crust, feldspathic volcanic rocks and a small amount of basic rocks, and the sedimentary environment is a weak oxidation-weak reductive environment. It is favorable for the enrichment and preservation of organic matter. The petrological characteristics, sedimentary structures and typical well logging curves of the Lower Ganchaigou formation indicate that the Lower Ganchaigou formation is mainly characterized by alluvial fan facies, fan delta facies and lacustrine equivalent sedimentary facies. The Ganchaigou formation in the Ganchaigou section is a retrogressive fan delta facies formed under the background of lacustrine transgression. The analysis of sedimentary facies (sedimentary microfacies) shows that the sedimentary pattern of the study area was surrounded by alluvial fans in front of Aljin Mountain and Qimantag Mountains and gradually transitioned into inland lacustrine facies during the sedimentary period of Lower Ganchaigou formation. On this basis, the alluvial fan-fan delta-lake sedimentary model was established.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.13

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