鄂尔多斯盆地志丹探区三叠系延长组沉积体系研究

【作者】 柴改建；

【导师】 李文厚；

【作者基本信息】 西北大学 ， 矿物学、岩石学、矿床学， 2009， 硕士

【摘要】 本文综合应用沉积学、岩相古地理学及层序地层学等理论和方法,通过野外剖面观察、钻井岩心观察、测井资料解释、薄片鉴定等手段,对志丹探区地区三叠系延长组沉积体系进行了深入的研究。通过区域对比标志层、野外踏勘资料及层序界面的确定,对研究区延长组进行地层划分。根据构造运动面划分出超长期基准面旋回,在测井剖面上识别层序界面、最大湖泛面、初始湖泛面、准层序、准层序组,并进行体系域及基准面旋回的识别与划分,将延长组划分为一个构造超层序和五个三级沉积层序,进一步分析层序对含油气性的控制作用。依据区域地质、古流向资料、轻重矿物岩屑分析、微量元素分析、稀土元素(REE)分析及古陆分布特征,对志丹探区延长组的物源进行了研究,认为物源主要来自北东方向,母岩为盆地东北缘太古代及早元古代变质岩。依据野外剖面露头观察,岩心描述、单井测井相分析和连井剖面对比,结合岩石类型、结构特征、沉积构造、古生物特征、剖面结构、测井相和沉积旋回分析等多种手段,识别出志丹探区延长组沉积体系主要三角洲沉积体系、湖泊沉积体系,划分出5类沉积亚相、16类沉积微相,其中主要发育三角洲前缘亚相首次详细研究了志丹探区延长组沉积微相和砂体展布特征,认为三角洲前缘水下分流河道和三角洲平原分流河道是志丹探区延长组油气储集的骨架砂体,沉积相决定着砂体的展布规律;在古地理演化过程中,长10-长8为三角洲前缘亚相;长7北部为三角洲前缘,南部发育深湖亚相:长6三角洲发育达到鼎盛时期,发育三角洲前缘;长4+5,长3,长2三角洲逐渐萎缩,其北部为三角洲平原,南部为三角洲前缘及浅湖;长1演化为三角洲平原。并建立了该区缓坡型的浅水三角洲沉积模式。更多还原

【Abstract】 Apllied with field profile observation,core description,logging data interpretation, thin section identification, reservoir lithology and physical analysis, and some effcective theories of other subjects such as sedimentology, lithofacies- paleogeography, reservoirgeology, and sequence stratigraphy, the sedimentology systerm of Triassic Yanchang Formation of Zhidan region was studied deeply.By the primary marks of contrast in region, data of reconnaissance in field and interface of sequence stratigraphy, stratum of the oil-containing interval Yanchang formation were devised.Based on the tectonic movement surface, super long-term base level cycles are marked off.All the sequences are identified from logging profiles, including sequence boundaries, maximum flooding surface, first flooding surface, ubsequences and subsequence sets; meanwhile, identified and classified system tracts and datum level cycles, From all the work above, Yanchang Formation are divided into a tectonic supersequence and five pieces of third class sedimentary sequences, which are use to analysis the control of the reserviors.This paper investigated source of Yanchang formation in Zhidan region, by the study of the regional geology, palaeocurrent direction, light and heavy mineral debris analysis, trace element and REE analysisi as well as ancient land distribution feature. These make sure that NE is the main direction of sediment provenance, and that metamorphic rock of Archeozoic and lower Proterozoic.According to outcop observation, core description, single well log facies analysis and connecting-well section comparison, combining with rock type, depositional tecxture, structure characteristics, paleontology, litho-electric features, profile structures and sedimentary cycles, ect. It shows that Yanchang formation is composed of the lacustrine system and the delta system in Zhidan region, which are subdibide carefully into 5 subfacies and 16 microfacies, the modal is the deltaic front microfacies.The sedimentary microfacies and sandstone distribution character of Yanchang formation in Zhidan region is displayed for the first time by this thesis.Considering that subaqueous distributary channels in deltaic front microfacies and distributary channels are the main frame sandbodies for oil and gas reservoir.The distribution rule of sandbodies is determined by sedimentary facies. Sedimentary environments of Yanchang formation have good inheritance, which make all the sandbodies of different time spreading in the NE direction in the region. The favorable source-reservoir-caprock group can be formed for the frequency of lacustrine transgression and regression. Through analysisi of sedimentary facies, the distribution of sandbodies, the character of structure and the property of reservior, etc, the favorable exploration area can be found out in the main oil-bearing beds of Yanchang formation in the region.更多还原