【作者】 刘刚；

【导师】 董树文； 柳永清；

【作者基本信息】 中国地质科学院 ， 构造地质学， 2007， 博士

【摘要】 从大地构造的观点看,两个板块相互碰撞形成挤压造山带,常常在俯冲板块的前缘形成前陆盆地。前陆盆地对油气的生成、运移、聚集和保存都十分有利,所以,前陆盆地成为油气聚集和油气勘探的有利地区。大巴山位于中央造山带的中部,是秦岭三叠纪碰撞造山带中唯一向南凸出的弧形构造带,称之为大巴山弧型前陆带。但是,大巴山前陆变形的时间、方式、沉积体系、生油机制、含油气性等认识仍存在较大的分歧。大巴山紧连接下扬子地块的北部,相互交接,由于近年川东北油气资源的新突破,使大巴山前陆形成、演化过程及其与油气成藏的关系越来越受到关注,是研究造山带与前陆盆地油气耦合关系的理想场所。特别是自普光大气田发现以来,为了更多的发现大油气田,深入了解大巴山前陆盆地的演化过程以及侏罗纪沉积充填历史非常必要。研究工作涉及四川盆地中北部大巴山前陆侏罗纪盆地层序地层、含油气系统等内容。论文在石油地质学及构造地质学理论指导下,综合应用地球化学分析,开展了研究区侏罗系油气成藏研究。旨在利用新理论、新方法、新技术对研究区侏罗系进行整体、系统、定量地研究,综合评价前陆盆地层序地层的发育特征,预测有利前景区带。在导师的指导下,本人于2004年,2005年和2006年多次在大巴山开展野外调查研究,野外工作时间累计110天,观测路线长度180km,测量剖面68km,采集样品200余件,重达300多kg。在实验分析、数据统计、地质成图等基础上,取得的研究成果与认识如下:1.首次系统划分大巴山前陆侏罗纪盆地各层序界面,通过露头层序地层解释、沉积旋回划分、沉积地球化学研究等,明确了从野外露头剖面上识别各级层序界面的标志。侏罗系作为一个独立的Ⅱ级层序,在此Ⅱ级层序中根据冲刷面、最大湖泛面等结构特征,又划分为7个Ⅲ级层序。2.依据关键露头剖面高精度层序特征分析,通过剖面对比建立高精度等时层序地层格架,通过对5条关键露头剖面的详细高精度层序特征分析,认识到:剥蚀面上的粗碎屑岩或与之可区域对比的其它沉积是层序底部边界附近的主要沉积特征;在盆地沉积环境中,砂泥岩发育,厚层、块状砂岩与泥质岩类的突变组合是低位体系域(LST)的主要沉积特征;湖进体系域(TST)以厚层泥岩夹砂岩为主,有时夹厚度较大的重力流砂体;高位体系域(HST)为砂泥互层沉积组合,以进积式叠加样式为主;最大湖泛面多为泥岩,但其厚薄不一。由于受凹陷东北部及北部双向物源的影响,砂岩呈半环状分布于凹陷的东北部,向西南部过渡为泥岩、粉砂质泥岩,研究中把层序结构分两种类型:既早侏罗世强烈构造运动形成的冲积扇-辫状河形的砂泥岩碎屑层序、中晚侏罗世形成的湖泊-三角洲-曲流河形的砂泥岩碎屑层序。对大巴山前陆侏罗纪盆地层序的结构特征与形成机理进行详细分析,为大巴山陆相前陆盆地层序地层的理论模式打下了基础。3.分析沉积物中氧化物、微量元素、稀土元素和重矿物的沉积环境意义及古气候意义,建立地球化学的层序特征。对砂岩碎屑进行统计,判别构造背景。4.在分析了研究区沉积地质背景及构造演化特征基础上,阐述了大巴山前陆侏罗纪盆地的成盆历史,指出其演化经历了3个演化阶段,形成时间为早侏罗世开始至晚侏罗世定型。5.在野外露头资料研究基础上,认为研究区烃源岩主要为J1层序(白田坝组)和J2层序(千佛岩组)上部泥岩,均为好烃源岩。提出了大巴山前陆侏罗系发育源上和源内3套成藏组合。沙溪庙组的油藏属下生上储油藏,烃源来自下伏J2层序(千佛岩组)或J1层序(白田坝组),油气藏靠油源断裂的沟通.与下面的烃源岩构成下生上储成藏组合;J2层序(千佛岩组)页岩和J1层序(白田坝组上部)页岩为主要的生油岩,以自生自储的方式存在,与上覆的盖层构成源内成藏组合。J5层序(遂宁组)含有少量深水暗色泥岩与上覆的J6层序(蓬莱镇组下段)河道砂岩,有可能构成下生上储的成藏组合。更多还原

【Abstract】 From the tectonic structure point of view, the collision of the two plates forms a series of orogenic belt, while in the frontal edge of the subducting plate , it is always shaped into the foreland basin. The foreland basin is convenient for the generation, migration and preservation of oil and gas, as a result, it is a favorable place for the accumulation and exploration of the oil gas.Daba Mountain, which is called the Daba Mountain arc foreland belt, is located in the central part of the central orogenic belt. It is the only parenthetical orogenic belt protruded to the south in the Qinling Trias orogenic belt.But the knowledge of the mechanism、sediment system、oil and gas generation、oil and gas reserve of Jurassic in Daba mountain foreland is still in disagreement, besides the time and the way of transformation. Daba mountain is joined north to the lower Yangtse block. Because of the breakthrough in the oil gas resource in northeastern Sichuan, close attention has been paid to the formation, evolving process of Daba Mountain in recent years ,as well as its relation with oil and gas accumulation.It is the ideal place for studying the connection between orogenic belt and the oil and gas coupling in foreland basin. Since the discovery of Puguang gas field, it is necessary to give a further insight into the generation process of the foreland basin along with its sedimentation silting history, in order to find more oil and gas filed.The research involves sequence stratigraphy in Jurassic, petroleum system in Daba mountain foreland basin in the north-east Sichuan basin etc. In this dissertation that under the theory of sequence stratigraphy, petroleum system, petroleum geology and structural geology , a major research of oil and gas accumulation of Jurassic in the researching area has been carried out ,with the allsided use of geochemical analysis . It is aim to use new theory, new method and new technology to study Jurassic literally ,systematically and quantificationally , to give an overall evaluation of the development feature about the foreland basin sequence stratigraphy, and then to predict the advantageous exploration target. Study under my tutor, I made the field investigation repeatedly in 2004, 2005 and 2006, about 110 days altogether. observed a route of 180km, measured a section of 68km, and collected about 200 pieces of sample that weighed about 300kg. The research results that based on a great number of study on the experimental analysis and statistic data as well as map, are as follows:1.Divide the sequence boundary Daba mountain foreland basin systematically for the first time. Define the symbol of distinguishing sequence boundary from outcrop through the explanation of outcrop sequence stratigraphy, the partition of sediment cycles, and the study of geochemistry. Jurassic, as an independentⅡorder sequence, has been redivided into 7Ⅲorder sequence according to the structure feature such as erosion surface and the largest lake flooding surface.2.According to the analysis of features of the key outcrop sequence stratigraphy, build the sequence frame, through the section comparison, and the study of feature of the 5 key outcrops, then it can be concluded that, conglomerate on the denudation plane or the other contrastive sediment are the main features surrounding the bottom border of the sequence. In the foreland basin sediment environment, the transilient group of mud rock and sandstone are the main sediment features of low-stand system tract (LST). Thick mud rock and sandstone interbedded is the chief component of transgressive system tract (TST), sometimes together with thick turbidity current sandstone; High-stand system tract (HST) is composed by the combination of mud rock and sandstone interbedded, with the progradation as its main style. Maximum flooding surface Sediment are usually mudstone, and the thickness is different from each other.Effected by provenance from the depression northeast and the north, sandstones shaped as semicircle,are distributed in the depression northeast ,and then mudstone and silty argillite as its transition to the southwest. The sequence is classified into two types: alluvial fan-braided river sequence, which was formed by the strong tectonic movement in the lower Jurassic, lake-delta-meander river sequence that generated in the middle and upper Jurassic. These two types have been used in the particular analysis of the structure feature and the formation mechanism of the Daba mountain foreland basin sequence, and they have laid the foundation for the theoretical mode of Daba mountain foreland basin sequence stratigraphy.3.To analyze the sediment environment and paleo-climate meaning of the oxide, microelement and lanthanon of sediment and heavy minerals, create the sequence feature of geochemistry. Carry on the statistical study of sandstone crumb to distinguish the tectonic environment.4.To elaborate the history of Daba mountain foreland basin ,on the basis of the analysis of sedimentology background and the evolving feature of the structure in the researching area ,and indicate the 3 evolving stages in this process, which started in the lower Jurassic and completed in the upper Jurassic.5.According to the study of outcrop, the mud stone identified in J1 and J2 are both good hydrocarbon source rocks in the researching area, Put forward that there are 3 oil and gas accumulation systems in Jurassic of Daba mountain foreland .according to the study of outcrop, the mud stone identified in J1 and J2 are both good source rock in the researching area, Put forward that there are 3 oil and gas accumulation system in Jurassic,Daba mountain foreland. Hydrocarbon in oil and gas accumulation systems of Shaximiao formation comes from J2 or J1, Reservoir together with the source rock beneath form oil and gas accumulation system, depend on the connectivity of fault. Shale in J1 and J2 is the main source rock, they form oil and gas accumulation systems along with the overlying cap. J5 that contains a small quantity of deep water dark mud rock, may form oil and gas accumulation system with the overlying J6 channel sandstone.更多还原