【作者】 冯娟萍；

【导师】 李文厚；

【作者基本信息】 西北大学 ， 矿物学、岩石学、矿床学， 2008， 博士

【摘要】 鄂尔多斯盆地是我国油气资源丰富的第二大内陆沉积盆地。经过多年的勘探与研究,近年来发现了众多岩性油气藏,证明其中生界仍有较大的勘探潜力,这对我国的油气战略和资源勘探开发具有重要的现实意义与经济意义。姚店油田北区位于鄂尔多斯盆地陕北斜坡东部,三叠系延长组是其主要的含油层系。最新资源评价预示其具有较大的勘探空间。但是由于对该区的沉积相、储层特征以及成藏主控因素等的研究较薄弱,从而制约了对该区油气富集规律的深入认识,致使勘探未能有重大突破。本文针对研究区存在的问题,从沉积学、储层沉积学、层序地层学、石油地质学等多学科入手,应用多种分析测试手段,对延长组的沉积相、储层微观特征及油气富集规律进行研究,并提出有利区带。将延长组划分为1个超长期、4个长期、9个中期和24个短期4级规模的地层旋回,并与延长组传统的地层划分进行对比。根据古流向、轻、重矿物及稀土元素分析,结合区域地质,认为研究区延长组沉积时物源主要来自盆地北部,源区母岩为阴山一带的变质岩和岩浆岩。本区延长组发育三角洲和河流沉积体系,认为长6三角洲平原分流河道及长2辫状河河道砂坝微相是该区油气储集的骨架相,砂体的发育完全受控于沉积相带的展布。研究区延长组砂岩为中、细粒长石砂岩,泥质杂基分布不均匀,胶结物主要是方解石,其次为石英、长石的次生加大、黏土矿物、浊沸石和少量铁质等。碎屑颗粒分选中等—好,以次棱角状为主,颗粒之间以线、点—线接触为主,主要为薄膜—孔隙式胶结。砂岩发育残余粒间孔和溶孔,孔隙小,分布状况差,结构复杂,喉道细小且不均匀,显示出较强的非均质性,相对而言长2油层组物性最好,长6次之,其他层位物性较差,整体属于典型的低孔低渗型储层。长2和长6砂岩经历了压实作用、胶结作用和溶解作用等主要成岩作用,目前主要处于晚成岩A期,长6油层组部分砂岩可达晚成岩A—B期。压实和胶结作用强烈破坏了原生孔隙,溶解作用则有效地改善了孔隙结构。发育的主要成岩相有压实压溶成岩相、弱压实—绿泥石薄膜胶结相、压实—石英、长石次生加大胶结相、压实—碳酸盐胶结相、泥质胶结相、浊沸石—长石溶蚀相。优质储层常出现在弱压实—绿泥石薄膜胶结相和浊沸石—长石溶蚀相的发育区,而其余四种成岩相发育区则物性差,常成为成岩致密带。除成岩作用外,沉积作用也是一个重要的影响因素,综合沉积相及储层特征的研究,结合本区实际情况,将延长组砂岩储层划分为4种类型。长2辫状河河道砂坝中主要发育Ⅰ类好储层,长6三角洲平原分流河道砂体中发育Ⅱ类较好储层和Ⅲ类差储层。通过对研究区油气成藏地质条件的研究,结合多年的勘探开发实践,表明沉积作用、成岩作用和构造作用不仅是油气成藏的重要基础,而且控制了油气的富集与分布,并根据有利区预测依据,在延长组长6及长2油层组中优选出多个有利区块,为下一步勘探开发提供了地质依据。更多还原

【Abstract】 Ordos Basin is the second largest inland sedimentation basin with prolific in oil, gas, coal and uranium resources. After years of exploration and research, many lithology reservoirs were discovered, it is indicated that the Mesozoic Erathem formation of Ordos Basin will likely continue to yield additional oil and gas discoveries for many years to come, that is of great practical and economic significance to the exploration and exploitation of hydrocarbon resources.Northern Yaodian Oilfield lies on eastern part of Shanbei Slope in Ordos Basin and the primary oil-bearing bed is Yanchang Formation. It is implied that there is biggish space for exploration in the future. However, our understanding of the hydrocarbon accumulation regularity of Yanchang Formation in northern Yaodian Oilfield was not deepened due to the weakness researches of sedimentary facies, the characteristics of reservoirs and the master controlling factors of oil accumulation, a momentous breakthrough in oil exploration has not been made in past years. In allusion to those issues about sedimentary facies, microcharacteristics of sandstone reservoirs and hydrocarbon enrichment rule, the much systemic researches have been carried out by means of sedimentology, reservoir sedimentology, sequence stratigraphy, petroleum geology and analyzing, testing measures.Yanchang Formation is divided into four scale Cycles, that is 1 Super-long-term Sea Level Cycle, 4 Long-term Sea Level Cycles, 9 Middle-term Sea Level Cycles and 24 Short-term Sea Level Cycles. They are compared with traditional stratigraphic classification. Based on analyzing palaeocurrent direction, light minerals, heavy minerals and REE characteristics combined with the regional geologic background, it is suggested that sediments in this area originate from the northern part of Ordos Basin in the period of Yanchang Formation. In addition, it is indicated that the parent rocks are metamorphic rocks and magmatic rocks in Yinshan mountain at the northeast side of Ordos basin. Based on source direction, depositional characteristics and studying in the fields, delta facies and fluvial facies are identified, of which distributary channels in delta plain microfacies and braided channels microfacies controlled the distribution of sand bodies and accumulation of oil and gas.It was shown that the sandstones are medium to granule arkose, which the mud matrix is widespread but not uniform distribution and the type of cements observed including calcite, quartz and feldspar overgrowths, clay minerals and laumonite. The main clastic particles constituents observed in sandstones are middling to fine in separation, sub-angular and sub-rounded but moderately to well sorted. These grains mainly have point-line or lines contact, membrane-porosity typed cementation. It was also shown that the main types of pores are remnant intergranular pores and dissolved pores. The reservoirs are poor in pore throat distribution, complex in structure, small and asymmetry in throat showing heterogeneity. But relatively speaking, the quality of Chang 2 sandstone reservoirs is the best and Chang 6 is the second while they are better than others. Taken as a whole, they are the typical low porosity and permeable reservoirs.It is shown that the diagenesis of the sandstones mainly include compaction, cementation and dissolution, which are in the late diagenesis phase A while part of the Chang 6 sandstones are in the A to B stage of late diagenesis. At the same time, the compaction and cementation destroyed their primary pore intensively, dissolution changed the pore structure effectively, consequently the reservoirs quality was improved. The diagenetic facies include compaction and pressolution facies, weak compaction-chlorite film cementation facies, compaction-quarts and feldspar overgrowth cementation facies, compaction-carbonate cementation facies, mud-cementation facies, and laumonite-feldspar dissolution facies, and favourable reserviors mostly occurred in the sandbodies of weak compaction-chlorite film cementation and laumonite-feldspar dissolution diagenetic facies belts. While rest four diagenesis facies developing zones have weak properties of matter and always turned into diagenetic tight zones. Besides the diagenesis, deposition is another important factor to the reservoirs quality. Integrated these researches with practical situation in this area, the sandstone reservoirs are divided into four types. I -good reservoirs are occur in the Chang 2 braided river channel sandbars, II -appreciably good reservoirs and Ill-poor reservoirs are occur in the Chang 6 delta plain distributary channels.According to the study of the geological conditions for oil and gas accumulation, sedimentation, tectonism and diagenesis not only are basement of hydrocarbon accumulation, but also control its enrichment and distribution. On the base of range of profitability, some advantageous blocks of oil are predicted of Chang 6 and Chang 2 Member in northern Yaodian Oilfield, which provide the credibility geology gist for further exploration and exploitation in this area.更多还原