【作者】 戴朝成；

【导师】 郑荣才；

【作者基本信息】 成都理工大学 ， 沉积学， 2011， 博士

【摘要】 位于造山带前缘与克拉通之间的前陆盆地,是世界上油气最丰富和大油气田最多的沉积盆地,也是最早发现油气和进行油气田勘探的领域。中国中西部前陆盆地的油气资源也十分丰富,是中国陆上油气勘探最重要的战略接替区之一。特别是四川前陆盆地,经过几十年的努力,已发现大量油气田,但据前人初步统计,前陆盆地油、气探明程度分别只有17%和6.7%,勘探潜力很大,是我国油气勘探的重要领域之一。由于四川盆地上三叠统须家河组物源、沉积层序和成岩作用的复杂性,储层普遍致密化,大多为非常规低孔低渗和特低孔特低渗裂缝-孔隙型储层,仅局部发育有少量中孔低渗储层,鉴于前陆盆地的构造复杂性和不同构造单元的层序地层、岩性、岩相、沉积埋藏史和成岩流体的差异性所决定的各构造单元成岩作用、成岩相和储集类型的差异性缺乏研究。本文在运用沉积学、古生物学、测井地质学、构造地质学、储层沉积学等方法技术,通过对四川前陆盆地形成时的沉积和构造背景分析,以及晚三叠世诺利克期～瑞替克期沉积地层的物源区分析和高分辨率层序地层学研究,建立全盆地层序地层格架,并进一步分析须家河组各层序形成时盆地的古地理格局。在此基础上,通过对盆地内逆冲推覆带、前渊坳陷带、前陆斜坡带和前陆隆起带等不同构造带上的须家河组成岩作用、成岩相、和孔隙类型对比,总结该盆地须家河组层序格架内不同类型的储层在平面上和纵向上的分布规律和控制因素,主要内容和成果如下:(1)采用区域沉积学对比、岩石矿物学和沉积地球化学示踪(稀土元素和微量元素)等方法、手段,对四川盆地须家河组砂岩的物源进行了研究,认为:研究区晚三叠世须家河期四川前陆盆地的沉积是多物源的,多物源区的存在为须家河组沉积相和古地理的系统研究奠定了基础,同时结合地表剖面、钻井岩芯和测井资料分析,将上三叠统须家河组划分为4个主要沉积相类型,从盆地边缘近物源区至盆地沉积-沉降中心区依次为冲积扇相、扇三角洲相、辫状河三角洲相以及湖泊相等沉积体系。(2)通过对四川前陆盆地上三叠统须家河组地表露头、地震剖面、测井剖面层序界面特征和最大洪泛面特征识别,将须家河组划分为分别代表“须下盆”和“须上盆”成盆期次的2个超长期旋回层序,5个分别对应于须二段～须六段的长期旋回层序和17个中期旋回层序。在描述各次级构造单元须家河组高分辨率层序发育特征与区域对比的基础上,分别建立了贯穿盆地的东西向及南北向等时地层格架,此二个方向的地层格架都具有自坳陷带向前陆隆起方向上超变薄的楔形充填体特征和区域地层对比关系,可确定为龙门山和米仓山-大巴山两造山带分别对应于“须下盆”和“须上盆”非同步异方向逆冲推覆活动的结果。在此基础上,以各长期旋回层序上升和下降半旋回相域为等时地层单元编制四川盆地层序-岩相古地理图。编图结果表明须家河组各时期岩相古地理面貌和沉积相带的展布规律严格受类前陆盆地的构造格局中的川西坳陷、川东北坳陷、渝东-川东南坳陷和川中古隆起组成的“三坳围一隆”构造格局控制。(3)四川前陆盆地由于构造相对复杂,不同构造带上成岩作用和成岩相具有较大差异,从而决定了储层在不同构造带的分布规律。本文在沉积相、铸体薄片观察和岩矿分析数据基础上,对各构造带上须家河组砂岩的成岩作用进行系统研究,得出逆冲推覆带前缘以压实作用和破裂作用为主;川西前渊坳陷带以压实和压溶作用为主;前陆斜坡和前陆隆起带压实作用相对较弱,绿泥石环边胶结作用和溶蚀作用发育,其中起破坏作用的成岩作用主要有压实-压溶作用、胶结作用,起建设性的成岩作用主要有早期绿泥石环边胶结作用、溶蚀作用和破裂作用。在成岩作用研究的基础上,进行了成岩相划分及成岩相组合特征分析,将须家河组砂岩砂岩划分为3种成岩相组合,其中压实-破裂-胶结成岩相和胶结-溶蚀成岩相为最有利于储层发育的成岩相带。(4)四川前陆盆地上三叠统须家河组储层在岩石学上具有低成分成熟度、低胶结物含量和结构成熟度中等特征,岩性在平面上具有一定的规律性,在川西北地区以岩屑砂岩为主,川西中部地区为岩屑砂岩与长石砂岩混合区,川西南地区以岩屑长石砂岩为主,川中前陆隆起为长石岩屑与岩屑石英砂岩混合区。储层总体物性较差,属低孔低渗和特低孔特低渗储层,局部发育有少量中孔低渗储层。由于盆地内逆冲推覆带、前渊坳陷带、前陆斜坡带和前陆隆起带的沉积、成岩以及构造作用的差异性。决定了储层孔隙类型的分带性,龙门山逆冲推覆带储层类型以裂缝型为主,另可见少量的溶蚀孔和原生粒间孔;前渊坳陷带储层类型为裂缝-次生溶孔型,以次生溶蚀孔隙为主,原生孔隙基本消失;前陆斜坡带储层类型以次生溶孔及原生粒间孔为主;前陆隆起带以溶蚀扩大孔和原生孔组成的混合孔为主,储层发育受沉积、层序、成岩和构造破裂作用的控制。更多还原

【Abstract】 Foreland basin between orogenic belt and craton is a sedimentary basin, which contains many of gas or oil field, and it is also the first exploration area and discovered the gas and oil place. The Foreland basin in Midwest of China is rich in hydrocarbon resources also, and it has become the most important strategy replace area in Chinese exploration area of gas and oil. In particular, after few decades efforts, Sichuan Foreland Basin has found many gas and oil field, but according to preliminary statistics of predecessors, explored gas and oil in foreland basin was only 17% and 6.7%, so it is of great potential and importance area for exploration to our country.Because the provenance, sequence and diagenesis of Upper Triassic Xujiahe Formation in Sichuan Basin are complicated, reservoirs generally densify, the main reservoir type is with low porosity and permeability. only a few with middle porosity and low permeability in partial, the structure in Sichuan Foreland Basin is complicated, and the sequence- stratigraphy, lithology, lithofacies, sedimentary burial history and diagenetic fluid are different, so it decided the diagenesis, diagenetic facies and reservoir types of secondary structural unit are distinct, but some of these are lack of study.The paper is basis on the technology of sedimentology, structural geology, palaeontology, logging geology and reservoir sedimentology, according to analysis of the sediment-tectonic setting when the formation of Sichuan Foreland Basin, also, including the study of provenance and high-resolution sequence stratigraphy between Norian to Rhactian period of Upper Triassic, the sequence stratigraphy frameworks from east to west and from north to south have been built, and the palaeogeographic frameworks of different sequence have been further analyze. On this basis, according to the comparison of diagenesis, diagenetic facies and pore types in thrust belt, foredeep depression zone, foreland slope and foreland uplift, the purpose is to conclude the distribution regularity and control factors of reservoir types in plane and vertical, main contents are as follows:(1)The region sedimentology comparison, mineralogy and sedimentary geochemistry have been used in provenance analysis of Xujiahe Formation sandstone, the conclusion is that the deposit of Late Triassic Xujiahe stage is of several provenances, the idea of several provenances provides basic for the palaeogeography study, combining with the surface section, drilling cores and the well logging data, the Upper Triassic Xujiahe Formation is divided into four sedimentary facies types, it is alluvial fan, fan delta, braid river delta and lake, which is ordinal from basin margin closer to provenance to basin subside-deposit center.(2) Based on the recognition of surface section, seismic section, sequence boundary features of well logging section, and features of maximum flooding surface of Xujiahe Formation of Upper Triassic in Sichuan analogous foreland basin, the Xujiahe Formation is divided into 2 super long-term sequence cycles, 5 long-term sequence cycles ( LSC1～LSC5 ) and 17 middle-term sequence cycles(MSC1-MSC17), which correspond to lower and upper the Xujiahe Formation of structure sequence, Xujiahe 2 member to Xujiahe 6 member respectively. On the basis of the sequence features of secondary structural unit and regional correlation, the sequence stratigraphy frameworks from east to west and from north to south have been built. The frameworks of the two directions are of the feature that is a wedge uplapping from depression to uplift, and the regional correlation. This phenomenon is the result of differently directional and nonsynchronous thrusting-napping process of Longmenshan, Micangshan-Dabashan, which correspond to lower and upper the Xujiahe Formation of structure sequence. On the basis of the rising and falling base-level phases of each long-term sequence cycles, the sequence-based lithofacies and paleogeography maps of Xujiahe Formation have been mapped. The result indicates that the sedimentary facies systems are controlled strictly by a so-called“three depressions and one uplift”tectonic pattern, which is made up of western Sichuan depression, northeast Sichuan depression, east Chongqing-southwest Sichuan depression and Sichuan central palaeo uplift.(3) Because the structure is complicated in Sichuan Foreland Basin, diagenesis and diagenetic facies are of significant differences in different tectonic zone, it has decided the distribution rule of reservoir. Based on the analysis of sedimentary facies, cast slice and rock and mineral logging datas, diagenesis of the Xujiahe Formation sandstone in different tectonic zone have been researched systematically, it is concluded that compaction and cataclasis are leading in thrusting nappe tectonic zone, compaction and pressolution are mainly in western depression, while in ramp region and uplift zone, compaction is relatively weak, rim agglutination of chlorite and denudation developed, It showed that the destructive diageneses mainly include compaction-pressure solution,cementation, and that the constructive diageneses mainly include rim agglutination of chlorite, denudation and cataclasis. Basis on the research of diagenesis, the diagenetic facies was studied, diagenetic facies association of Xujiahe Formation sandstone is divided into three type, and the diagenetic facies of most beneficial to the reservoir development is compaction- clastation- cementation and cementation- denudation types.(4) Reservoirs of the Upper Triassic Xujiahe Formation is of the characteristics that low compositional maturity, low cement content and medium maturity in Sichuan Analogous Foreland Basin, Lithology in the plane with some regularity, in the Northwest region dominated by lithic sandstone, there are lithic sandstone and feldspathic sandstone mixed zone in Central west Sichuan, In Southwest dominated by lithic feldspathic sandstones, while In central-South Sichuan region, there are feldspathic lithic and lithic quartz sandstone mixed zone. Reservoirs are generally bad, the main reservoir type is with low porosity and permeability. Only a few with middle porosity and low permeability in partial. Because of the sedimentation, diagenesis and tectonic difference in thrust belt, foredeep depression zone, foreland slope and foreland uplift, It determines the type of porosity and zonation, fractured reservoirs are mainly in Longmen Mountain thrust belt, there are a small amount of emposieu and original intergranular pore, the pore type in foredeep depression zone is fracture-secondary dissolved pore, the primary pore is disappearance, in foreland slope, the pore type is secondary dissolved pore and primary pore, while, in foreland uplift, mixed hole consist of corrosion hole and primary hole is mainly, the development of reservoirs is controlled by deposition, diagenesis and cataclasis.更多还原