【作者】 杨磊；

【导师】 刘池阳；

【作者基本信息】 西北大学 ， 油气田地质与开发， 2008， 博士

【摘要】 中生代鄂尔多斯盆地为叠加在早、晚古生代华北克拉通大型盆地之上,历经多期不同形式改造的残留克拉通内盆地。有关该盆地中生代原始沉积面貌的探讨,长期以来深受关注但认识不一。侏罗纪延安组沉积期是盆地发展演化的重要阶段,为油、气、煤等矿产形成转化的主要时期,但研究程度较弱。本文在广泛吸收和客观分析前人研究成果的基础上,以“整体、动态、综合”的三项原则和改造型盆地研究理论为指导,从今鄂尔多斯盆地及周邻地区残存沉积建造和盆地构造演化特征两方面实际出发,通过系统的地层划分与对比、沉积相分析、物源综合分析、边缘相的识别、地震剖面解释、沉积速率对比和裂变径迹测年等综合研究方法,取得对原始盆地沉积面貌的认识。受后期强烈而不均匀的剥蚀改造的影响,鄂尔多斯盆地延安组与周邻地区同期地层的分布和厚度发生了较大的改观:在今盆地本部,延安组大范围整体分布,主体厚度在160～300m之间,呈东薄西厚和南薄北厚的特征;在盆地周邻的山西、河南、内蒙古及宁夏贺兰山、六盘山等地区均有同期可对比的地层零星分布。根据鄂尔多斯盆地延安组孢粉、古植物和双壳类等化石,划分其时代属于中侏罗世早期。根据岩性颜色、标志层分布、沉积旋回及煤层发育特征将延安组划分为4段10个油层组,除东部露头区外盆地内大部分地区只发育延10～延4层,盆地周邻地区同期地层同样可以与延安组进行分段式岩性及古生物对比。通过对盆地内大量岩心、野外露头剖面观察和钻、测井资料分析解释并结合岩矿鉴定、粒度分析等多种方法,识别出了鄂尔多斯盆地延安组主要以曲流河、辫状河、三角洲和浅湖相沉积体系为主,盆地边缘局部发育有冲积扇沉积体系。鄂尔多斯盆地侏罗纪富县期至延安期经历了由填补、区域沉降-沉积到缓慢抬升的演化过程,相应的沉积体系划分为富县期至延10期的冲积扇-河流沉积体系,延9～延6期的三角洲-湖泊沉积体系,以及延4+5期的交织河-湖泊沉积体系。对周邻地区同期地层的沉积相分析表明,义马地区义马组以冲积扇、河流、湖泊相发育为特征,济源地区杨树庄组发育滨、浅湖沉积体系。山西地区大同至宁武一线大同组自北向南由含煤的河流-三角洲相为主的沉积序列变为不含煤或含煤性差的湖泊相为主的沉积序列。汝箕沟煤田延安组的岩性、岩相、含煤性及地层的分段性与盆地西缘完全有可比性。石拐地区五当沟组自身就构成一个完整的冲积扇-河流-滨浅湖-深湖相的沉积旋回。通过沉积相、古水流、轻、重矿物含量、石英阴极发光和稀土元素含量研究发现,鄂尔多斯盆地延安期存在多个物源区,而西部、西北部又为盆地的主要物源区。从古流向平面分布看,山西地区大同组古流向皆以指向今盆地东部延安及其以东地区为主,显示与今盆地东部露头具统一汇水中心。贺兰山汝箕沟煤田延安组古流向亦指向盆地本部,与盆地西缘的石沟驿古流向一致。河南义马盆地义马组、内蒙古石拐盆地五当沟组古流向均具有指向今鄂尔多斯盆地内部的趋势。首次采用了最新的测井和露头资料,系统的编制了鄂尔多斯盆地富县组和延安组各层段厚度等值线图和底面构造图,发现现今残余地层厚度在古河道发育区明显增厚。通过采用Surfer8软件的三维建模技术,真实直观的重塑了富县组和延安组各层段底面的构造面貌,以及六条古河道的河谷阶地和分布位置,盆地呈现出东高西低的西倾单斜的构造格局,东北缘和南缘微微翘起。综合分析研究认为,鄂尔多斯盆地延安期的原始沉积边界大致为:向东在今太行山脉以西,包括了大同、宁武、义马和济源盆地。西北边界为贺兰山西侧的贺兰山西缘断裂带;西南边界为六盘山西侧的六盘山西缘断裂带。北部边界位于黄河断裂以南的乌兰格尔-罕台川一线,即伊盟隆起的北部一带。南部边界大致位于陇县-千阳-麟游-彬县-旬邑-宜君一线,即渭河盆地以北。更多还原

【Abstract】 The Mesozoic Ordos basin is a residual interior cratonic basin that superimposed on the Palaeozoic large North China craton and experienced multistaged deformation by different styles. The discussion about the primary features of this basin in Mesozoic has been paid more attention. Various conclusions have been proposed.The Yan’an period in middle Jurassic is an important stage in the development and evolution of Ordos basin.It’s the main period for the hydrocarbon and coal seams forming and transforming,but the study about Yan’an formation is very little.On the base of predecessor’s work,taking integrated,dynamic and comprehensive analysis and the research theories about reformed basin as guidance,starting from the nowadays’ remanent sedimentary entities and structural framework of the basin and its adjacent areas,by the systemic stratigraphic partition and compare,sedimentary facies analysis,provenance analysis,identify of marginal facies,seismic profile interpretation,sediment speed compare,and fission-track dating, the cognition about the sedimentary features of primary basin is acquired as a result.Effected by the intense and diversified denudation in later stages,the stratum distribution and thickness pattern of Yan’an formation in Ordos Basin and its synchronal stratum in adjacent areas altered largely.In the residual basin,Yan’an formation distributed extensively,the primary thickness is from 160m to 300m,appearing west thicker than east and north thicker than south generally.The synchronal stratum that can be compared sparsely distributed in the adjacent areas of Ordos basin,including Shanxi,Henan Province,inner Mongolia,Ningxia autonomous region.It is early middle Jurassic according to sporomorph,ancient plant and bivalve fossils in Yan’an formation in Ordos basin.Based on the characteristic of lithology,color,marker bed, depositional cycle and coal seam,the Yan’an formation in the residual basin is divided into four segments or ten reservoirs and existing Y10-Y4 reservoir except for eastern outcrops nowadays. The synchronal stratum that distributed in the adjacent areas of Ordos basin can be compared with the Yan’an formation on the characteristic of lithology,segmentation and paleontology.According to the analysis of great deal of the well cores,outcrops observation,well logging data interpretation,and combined with other methods,such as lithology identify and grain size analysis,some sedimentary system types as alluvial fan,meandering river,braided river,delta and shallow lake facies are identified in Yan’an formation in residual Ordos basin.There is a evolution process of filling to regional sedimentation and uplift slowly from Fuxian to Yan’an period in Ordos Basin.So it can be divided into alluvial fan-river sedimentary system from Fuxian to Y10 period,delta-lake sedimentary system from Y9 to Y6 period and anastomosing river-lake sedimentary system in Y4+5 period.On the basis of analysis of sedimentary facies of synchronal stratum in adjacent areas,Yima formation shows characteristic of alluvial fan,river,and lake facies in Yima.Yangshuzhuang formation shows shallow lake facies in Jiyuan.Datong formation shows from a set of coal-bearing viver-delta facies to none coal-bearing lake facies in Datong to Ningwu of Shanxi Province. Yan’an formation in Rujigou can be compared with synchronal stratum in western of Ordos Basin on the characteristic of lithology,coal-bearing and segmentation.Wudanggou formation shows characteristic of a complete set of alluvial fan-river-shallow lake-deep lake facies in Shiguai.There are many provenances of sediments and it is main provenance in west or northwest of Ordos Basin in Yan’an period by studying sedimentary facies,paleocurrent direction,content of light and heavy mineral,quartz cathode luminescence and content of rare earth elements.It shows a unified catchment center with eastern outcrops because paleocurrent direction in Datong formation of Datong basin is eastward to Yan’an.Paleocurrent direction in Yan’an formation of Rujigou mine is consistency with synchronal stratum in western of Ordos Basin.Paleocurrent direction of synchronal stratum in Yima and Shiguai basin is inner of Ordos Basin nowadays.It shows thickness of present stratum is higher in ancient river area by drawing depth isoline graph and lower surface structure graph in Yan’an and Fuxian formation of Ordos Basin.It shows valley terrace and distribution location of ancient river of lower surfaces in Yan’an and Fuxian formation visually by using 3D modeling basin of Surfer 8 software.It is high east and low west of monocline,upwarping appreciably in northeastern and south margin of Ordos Basin.Based on multidisciplinary analysis and research,the boundary of the original basin in Yan’an period is approximately concluded:the eastern borderline is in west of Taihangshan, including Datong,Ningwu,Yima and Jiyuan basin;the northwestern borderline is fault zone in west margin of Helanshan;the southwestern borderline is fault zone in west margin of Liupanshan; the northern borderline lie in Wulangeer-Hantaichuan of Yimeng liftup;the southern borderline lie in Longxian-Qianyang-Linyou-Binxian-Xunyi-Yijun of Weihe basin.更多还原