柴达木盆地柴西地区喜马拉雅运动与油气成藏研究

【作者】 陈新领；

【导师】 王廷栋； 张永高；

【作者基本信息】 西南石油学院 ， 矿产普查与勘探， 2004， 博士

【摘要】 论文首先分析了柴达木盆地的区域构造特征及演化过程,进一步明确了阿尔金断裂带主要为中新生代以来活动的大型走滑构造带。论文首次探讨了喜马拉雅运动以来,新生代柴达木盆地的形成机制与控制因素,分析认为,柴达木盆地受边界构造活动和深部地质作用共同控制,新生代盆地沉积沉降中心的迁移与深部构造有密切关系,柴东地区的天然地震资料、深部地球物理资料、沉积特征及地热信息等综合反映了目前柴达木盆地东部第四系沉积中心受深部构造控制作用明显,柴西古地温资料、断裂构造及沉积特征也揭示出早喜马拉雅期间在某些地区可能产生了地壳的伸展作用引起深部地幔经受了局部隆升作用。因此,柴达木盆地新生代沉积中心的迁移受深部地质构造控制,而边界活动性的变迁也是受大地构造背景影响。新生代柴达木盆地沉积中心迁移的主要构造动力学特点为盆地区域构造的横向压缩、纵向伸展作用,具体表现为盆地沉积中心迁移的过程,实际是盆地基底或上地壳通过地壳中的塑性层在一定的周期或时间内向东侧拆离,从而使沉积中心处地壳变薄,沉降作用加大,形成相对坳陷区。 论文详细分析了柴西地区构造变形、深部构造特点,对英雄岭地区的构造演化动力学过程进行了深入的解剖,充分分析了英雄岭及周边复杂的地质构造现象及控制因素。分析认为晚喜马拉雅期间,因近SN向的构造挤压力作用,阿尔金构造带上的阿卡腾能山与英雄岭西段发生了构造块体旋转方向相对的挤压作用,导致两者之间的区域发生了强烈的构造反转,产生了显著的隆升,形成了指状交错的构造格局。通过分析柴西南三维连片区地震资料、柴西地区重力资料和遥感所揭示的深部断裂构造信息,得出早喜马拉雅期间,柴西地区为断裂作用活动为特征的断陷结构,表现为断裂带两侧沉积厚度差别显著,断裂活动控制沉积相带的展布,对柴西连片三维区地震属性分析表明,在断陷湖盆的中部分布有储集性能较好的砂体,这可能与该区湖盆以陡坡为特征造成的。如同为E₃²在Ⅺ号断裂带的北侧深湖盆中沉积物颗粒较粗,反而为粗相带。推测属于重力流作用的结果。柴西地区的断陷构造格局形成了该区多个相对独立的断陷湖盆,使柴西地区具有多个不同母质类型的生烃凹陷。 地球化学参数所指示的烃源岩发育环境特征和油气运移路径信息,同样说明柴西地区在烃源岩发育期间,存在多个分割性的凹陷,它们在母质类型、氧化还原条件、盐碱度等方面均有一定的差异,说明在凹陷的深度、基底构造活动、物源供给等方面均存在分异性。沉积相、沉积体系与层序地层学研究成果揭示该区沉积凹陷受构造运动控制特征最为主要,说明是构造活动导致了各沉积凹陷在地球化学特征、沉积体系等方面的差异,而分析构造活动的特点应该是研究断裂和断块活动的差异性。 中喜马拉雅运动期间,柴西地区西南的阿尔金山开始隆升,在七个泉一带出现了角度不整合。这一次区域性的抬升作用产生了该区第一期构造裂缝。中喜马拉雅运动使柴西地区由断陷构造特征转变为坳陷构造环境,柴西地区的中新世以后的坳陷作用过程也是该区烃源岩加速成熟的过程,构造裂缝的发育与烃源岩的成熟相匹配,形成了柴西地区第一次油气生排烃过程,同沉积构造为有利的油气圈闭。 晚第三纪后期的晚喜马拉雅运动在柴西地区构造变形强烈,以强烈的压扭构造活动为特征。第四纪以来的新构造活动虽然主要表现为明显的构造抬升作用,但由于构造边界的影响,更多还原

【Abstract】 The author analyzed tectonics of Qaidam basin and plate evolution process, further make definite that Altin fault zone mainly activated during Mesozoic and Cenozoic. The author discussed the mechanism of Cenozoic Qaidam basin development and controlling factors. The Qaidam basin formed with the control of boundary activation and deep-seated structures, and the migrations of depocenter and subsidence center are related with the activation of deep-seated structures. The earthquake data, geophysics of deep-crustal structure, sediments and geothermal data show that the depocenter of Quaternary is controlled by deep geology; paleogeothermal data of west of Qaidam basin,faults structures and sediment characters implied that this area underwent mantle uplift during the early Himalaya Orogeny because of extension of supracnist developed following Altin and east Kunlun faults sinisterly strike slip. The tectonics dynamics which control migration process of depocenter during Cenozoic is the lateral shortening and strike extension of deep-seated structure. Basin basement and supracnist activate with the middle crust as plastic strata which result the crust under depocenter become thinner and subsidence enhanced and form the depression regions.The author discussed with detail the structure deformation, deep geology character of west of Qaidam basin, summarized dynamic features of Himalaya stages of west of Qaidam Basin from integration of geology, 2D/3D seismic data, remote sensing, gravity, aeromagnetic and well data. During the later stage of Himalayan orogeny, Aktenen mountain(part of Altin Zone, west of Yingxiongling Uplift) rotated clockwise and uplifted caused by SN regional compression, while Ganchaigou zone(middle part of west YL Uplift) developed a SE local compression stress field, which resulted the basement uplifted rapidly. In the near southern area of YL, local extension tectonic stress field developed, and a Neogene-Quaternary lake formed. The middle stage of Himalaya orogeny transformed the paleogene transtensional tectonic setting to down-warping in West Qaidam Basin. Altin mountain rise, sediment center migrated to east and north. By analyzing the major faults, tectonic blocks and sediment depression distribution, the author realized that YL and adjacent area developed local extension tectonic setting, formed the stable fault-controlled basin, fine source rocks developed.Geochemical data shows source rocks distribute in several segmented depressions which generated different hydrocarbons in mother material types, redox conditions and salinity. The major reason is that tectonics controlled the depth of depressions, basement activation and supplement of sediments. Faces, sediment systems and sequences studies imply that depressions are controlled by tectonics.During the mid Himalaya orogeny, Altin mountain in south west of Yingxiongling began to uplift and unconformity between Pliocene and Miocene can be observed in Qigequan section. This regional uplift generated the first stage structural fracture and resulted the down-warped basin developed from fault depression setting. The down-warped process accelerated source rocks maturation. With good match of fracture developing and maturation of source rocks, the first stage of generation and migration of hydrocarbon appeared. Synsedimentary structures are favorite traps of this stage.The late Himalaya orogeny was very strong in west of Qaidam basin, which resulted severe deformation, displaying as strong compression-shear movement. Neotectonics since Quaternary is displayed as apparent uplift in west of Qaidam basin, but with different boundary conditions, different sectors have their own structure activations. For example, Gaskule area developed a Quaternary down-warped depression while Yingxiongling uplifted apparently, and local structurezones and depressions controlled by compression-shear activation of faults developed in northern of Yingxiongling. The late Himalaya orogeny controlled" late stage accumulation of hydrocarbon, and structure traps developed in this stage are favorable for petroleum seeping from destroyed paleo-reservoir.The late Himalaya orogeny produced large number of fractures. The regional SN direction compression make SN trend fractures be the effective discharge system, and the generated NW and NE trends shearing fractures are also effective during tectonic activation. So the oil fields in west of Qaidam basin have the character of late accumulation. With late Himalaya orogeny destroying primary reservoirs, secondary reservoirs appear in structures or non-structure traps developed during late Himalaya orogeny stage. The perspective exploration targets include fracturing traps, stratigraphic traps and Oligocene epoch raised fault blocks.更多还原