【作者】 杨超；

【导师】 陈清华；

【作者基本信息】 中国石油大学 ， 地质学， 2010， 博士

【摘要】 柴达木盆地为被祁连山、阿尔金山、昆仑山包围的山间盆地,上古生界地质研究工作和油气勘探程度较低。本文以构造地质学、沉积学为理论指导,综合运用露头、地震及其钻井资料对柴达木盆地构造特征、上古生界沉积地层分布特点、烃源岩发育特征等进行了深入研究;并结合大量的分析化验资料,对柴达木盆地石炭系勘探前景进行了评估;这对指导柴达木盆地上古生界油气勘探工作具有重要意义。通过对野外18条露头剖面的实地观测和对比,并结合地震剖面的地层追踪,认为上古生界地层不仅在盆地外围出露较全,而且盆地内发育大面积的上古生界地层,在德令哈附近及其阿姆尼克山南部地区沉积地层较厚。通过对贯穿全区的地震地质剖面的研究,盆地整体表现为山间有盆,盆内有山的构造格局;盆地内形成了多隆、多坳,隆坳相间的构造格局;盆地与周围山脉均以断层接触,都是以山体向盆地逆冲,逆冲方向指向盆地,而断面倾向山体一侧,形成北冲南倾、南冲北倾的构造样式;盆地与阿尔金山深层以断层接触,浅层为超覆关系。并对盆地内断裂进行了分析研究,划分出祁南反S型断裂体系、昆北压扭断裂体系和中部弱变形构造断裂体系。根据盆地的基底性质及其起伏特点、重磁资料特点、盆地构造变形特点、沉积中心迁移规律以及含油气系统的分布特点,并结合前人对该盆地的划分方案,把盆地划分为祁南逆冲带,一里坪坳陷,昆北逆冲带,德令哈坳陷,欧龙布鲁克隆起,三湖坳陷共六个一级沉积构造单元。通过对野外测量的古流向数据的研究认为,陆源总体来自北部,反映海侵方向由南向北,反应沉积中心在沉积盆地的南部地区。并通过上古生界火山岩地球化学特征的研究认为,晚泥盆世构造背景盆地北缘表现为碰撞期的板内拉伸,盆地南缘表现为后碰撞期的陆内拉张;早石炭世构造背景表现为陆内稳定拉伸的构造背景;晚石炭世盆地北缘构造背景与早石炭世相同,南缘为洋陆俯冲的构造背景,并重点对上古生界构造演化特点进行了研究。通过对野外样品的分析化验,研究结果表明,以胜利口-锡铁山一带为界,在柴达木盆地西北地区上古生界地层普遍变质,而东部地区变质则相对较弱,变质作用较强的地区,已经不具备生烃潜力。石炭系烃源岩主要以暗色泥岩为主,炭质泥岩和煤可能具有生烃能力。下石炭统暗色泥岩有机碳含量一般达到了差到中等,而上石炭统暗色泥岩有机碳含量达到好或者很好;上、下石炭统的暗色灰岩有机碳含量均比较低,一般仅为非到差等烃源岩;有机碳评价较好的泥岩主要发育在潮坪、泻湖、沼泽相沉积相类型中;剖面上评价较好的层位为怀头他拉组的中部和克鲁克组及其扎布萨尕秀组的下段,评价结果已经达到好到很好等级。样品中的有机质类型均以Ⅲ型和Ⅱ2型为主。除都兰、格尔木地区有机质成熟度过高、处于过成熟的生干气阶段外,其它地区有机质成熟度中等,正处于生、排烃高峰期,具有良好的油气勘探前景,并优选出两类油气勘探远景区。更多还原

【Abstract】 Qaidam Basin is surrounded by the Qilian Mountains, Altun Mountains and Kunlun Mountains. In this area, few geological research works and oil and gas exploration of low level in the upper Paleozoic have been done. In this paper, guided by structural geology and sedimentology, we conducted in-depth research on the structural characteristics of the Qaidam Basin, distribution characteristics of sedimentary strata in the Upper Paleozoic, and the development characteristics of hydrocarbon source rock, using integrating outcrop, seismic and drilling data. Moreover, by analyzing a large number of test data, we also evaluated the Carboniferous exploration prospect in the Qaidam Basin, which will have great significance for guiding the Upper Paleozoic oil and gas exploration work in Qaidam Basin.Through the 18 field outcrops in the field observation and comparison, combined with interpreting and tracking seismic profiles, we found that the Upper Paleozoic strata is not only exposed in the periphery of basin, but a large number of Upper Paleozoic strata also exist within the basin. And thick sedimentary strata exist near the Delingha area and the southern Amunike Mountains.By studying on the geological section of the whole region, we found that Qaidam basin performance tectonic pattern as a basin within which there is a mountain, and in turn among of the mountains there is a basin. And there formed a multi-uplift, multi-depression, and uplift and depression alternate distribution of tectonic pattern. The basin contact surrounding mountains by the fault, and the mountain thrust to the basin, whose direction point to the basins, while the fault surface tend to the side of the mountain, and form the tectonic style about North thrust -South tend and south thrust - north tend. Basin contacts the Altyn Tagh fault in deep level and in shallow level the fault overlap the basins. From studying on the fault, we divided the whole basin into three geological systems: the anti-S-fault system of northern basin, pressure torsional fracture system of north Kunlun Mountain and the weak deformation fault system in the central of basin. Based on the study of the principle of division about tectonic features, transportation of the depocenter, distribution of the oil and gas, lithology character and fluctuate of the bedrock and the character of the abnormality in gravitation and magnetic field, we divided the Qaidam Basin into east and west units by the line of the Ganshen-Xiaochaidan where the characters of sedimentation and tectonic deformation start to defer. The tectonic deformation is more intense in the west than in the east of the Qaidam basin. Then we divided the Qaidam Basin into six first-order units: the obduction zone in south of Qiliang mountains, the obduction zone in north of Kunlun mountains, Oulongbuluke uplift zone, the Yiliping, Sanhu and Delingha Depression.From the study of paleocurrent data that is collected in the field and geochemical behavior of Neopaleozoic volcanic rocks, it is concluded that the land sources of the eastern part of the basin generally come from the north, which reflects that the direction of transgression is from the south to the north and the depocenter lies in the southern part of the basin. The tectonic settings were intraplate tension in later stage of collision in Late Devonian, intracontinental tension in Early Carboniferous and ocean-continent underthrust in Late Carboniferous. The Chaidamu Block Mass developed a series of slim graben-like basin or ocean trough and formed the prototype of Chaidamu central uplift (Niubiziliang ancient land) because of tension from Late Devonian. The Carboniferous depositional basin, with a depression and uplift palaeogeographic framework, is a differential subsidence basin, which formed by Hercynian movement on the basis of Late Devonian rift trough. It was a rift basin deposited with neritic facies carbonate rocks and was extensively transgressed. Lagoon, fan dalta (or braided river dalta) of transitional facies and coal-bearing deposition of paludal facies were formed around the ancient land. Permian period had the same sea area as that of Carboniferous Period, which still located in epicontinental faulted depression and belonged to clasolite-carbonate construction with stable shallow marine deposition.Through the analysis of field samples for testing, the results show that by boundary with the Shenglikou-Xitieshan line, the Upper Paleozoic strata widespread corruption in the northwest of Qaidam Basin, while the eastern region is relatively weak metamorphism. Moreover, a strong regional metamorphism does not have hydrocarbon potential. Carboniferous source rocks which are mainly dark mudstone, carbonaceous mudstone and coal may have the ability of hydrocarbon. Carboniferous dark-colored mudstone, carbonate rocks, coals and carbonaceous mudstone are well developed in the eastern Qaidam basin. Regional geological surveying and organic geochemical analysis indicate that Carboniferous hydrocarbon source rocks consist of the main part of dark-colored mudstones and carbonate rocks among which coals and carbonaceous mudstones probably have hydrocarbon-generating capacity. The dark-colored mudstones have a poor to moderate grade content of organic carbon in lower Carboniferous, but in upper Carboniferous there are good or better grade content of organic carbon and the organic matter is mainly ofⅡ2 andⅢtypes, whereas the limestones have a low content of organic carbon, and the organic matter is also of Ⅱ2 andⅢtypes. Therefore, they belong to poor to moderate hydrocarbon source rocks. The dark-colored mudstones evaluated that are better in organic carbon develop in tidal flat, lagoon and marsh-phase sedimentary fans. The horizon that is good in evaluation is the middle of Huitoutala group, Kuluke group and below of the Zhabushagaxiu group. All the source rocks are in a peak period of oil generation and expulsion with a moderate maturity of organic matter and have good petroleum prospects, except those in the Dulan and geermu area that contain post-mature organic matter and are in a post-mature, dry gas-generating stage.更多还原