HIGH-RESOLUTION SEQUENCE STRATIGRAPHIC ANALYSIS OF THE PERMIAN IN THE WESTERN SHANDONG AND HUAINAN-HUAIBEI COALFIELDS

The sedimentary characteristics and their combination succession of the Permian in the Shandong nd Huainan-Huaibei coalfields are analyzed. The mid-and short-term stratigraphic base-level cycles are identified. High-resolution sequences are divided based on the above results. The study shows that the stratigraphic base-level cyclic method is an efficient way in the determination of the high-resolution sequences, especially in the classification of tbe terrestrial and transitional depositional succession.

Tertiary Sea Level Changes and Sequence Stratigraphic Framework in East China Sea Shelf Basin

The East China Sea shelf basin is a key area for setting up the sea level changes of Cenozoic in the West Pacific. Based upon the characteristics of seismic reflection, the analysis of sequence stratigraphy and depositional system, the high resolution chronostratigraphic framework has been set up by using the data of micropaleontologic biozone fossils. The relative sea level change curve has been set up by combining analysis of paleoecology, genetic facies, specific sedimentary structures and on lap recognized from the seismic profiles with study of geochemical characteristics. There are 4 2nd order basin cycles showing the long term sea level changes, and 22 3rd order cycles showing short term ones with relative changing ranges of 0-150 m. Transgression and regression showing long term sea level changes bear asymmetric feature, which indicates that the speed of transgression is faster than that of regression. There are a lot of differences when compared with Haq ’s curve. The sequence stratigraphic framework has also been set up and 3 tectonic sequences, 7 supersequences and 19 sequences have been subdivided for Tertiary in the East China Sea shelf basin. On the basis of detailed analysis of genetic facies and log facies, 9 sedimentary systems, 20 depositional assemblages and many genetic facies have also been recognized and investigated. Based on the studies mentioned above, the favorable source and reservoir facies of gas and petroleum are indicated.

The Late Triassic Sequence-Stratigraphic Framework of the Upper Yangtze Region,South China

In the transitional period between the Middle and the Late Triassic, the Indochina orogeny caused two tectonic events in South China：（1） the formation and uplift of the Qinling-Dabie orogenic belt along the northern margin of the South China Plate, due to its collision with the North China Plate; and 2） the development of a 1300-km-wide intra-continental orogen in the southeastern part of the South China Plate, which led to a northwestward movement of the foreland thrust-fold zone. These tectonic events resulted in the ending of the Yangtze Platform, and were a stable paleogeographic factor from the Eidacaran to the end of the Middle Triassic. This platform was characterized by the widespread development of shallow-water carbonates. After the end of the Yangtze Platform, the upper Yangtze foreland basin（or Sichuan foreland basin） was formed during the Late Triassic and became a accumulation site of fluvial deposits that are composed of related strata of the Xujiahe Formation. In western Sichuan Province, the Xujiahe Formation overlies the Maantang Formation shallow-water carbonate rocks of the Xiaotangzi Formation siliciclastic rocks（from shelf shales to littoral facies）. The sequence-stratigraphic framework of the Upper Triassic in the upper Yangtze foreland basin indicates a particular alluvial architecture, characterized by sequences composed of（1） successions of low-energy fluvial deposits of high-accommodation phases, including coal seams, and（2） high-energy fluvial deposits of low-accommodation phases, including amalgamated river-channel sandstones. The spatial distribution of these fluvial deposits belonging to the Xujiahe Formation and its relative strata is characterized by gradual thinning-out, overlapping, and pinching-out toward both the east and south. This sedimentary record therefore expresses a particular sequence-stratigraphic succession of fluvial deposits within the filling succession of the foreland basin. The sequence-stratigraphic framework for the Upper Triassic in the Upper Yangtze region provides a record of the end of the Yangtze Platform and the formation of the upper Yangtze foreland basin.

Late Paleozoic Sequence-Stratigraphic Frameworks and Sea Level Changes in Dianqiangui Basin and Its Adjacent Areas with Systematic Revision of Regional Unconformities

The formation process of the Dianqiangui basin, a special basin, occurred after the Caledonian orogeny, in the south of Guizhou, the west of Guangxi and the southeast of Yunnan, experienced three periods: it began in the Devonian, persisted in the Carboniferous, and became fiercer in the Permian. Controlled by syndepositional fault-zones, varieties of isolated carbonate platforms, large and small, were developed in the background of a deep-water basin, namely, an inter-platform ditch. And a special paleogeographical Late Paleozoic pattern marked by “platform-basin-hill-trough” was produced in both the Dianqiangui basin and its adjacent areas. Affected by regional tectonic activities and the global changes in the sea level, the platform carbonates and coal measures superimposed each other cyclically on the attached platform. The reef-building on the isolated platform and the margin of the attached platform corresponds to the development of the shale succession in the deep-water basin. All of these elementary characteristics reflect a regular and sophisticated filling succession of the Dianqiangui basin, a result of the dual controls of the regionally tectonic activities and the eustacy. Based on the two elementary features of the third-order sequences, i.e. the regularity of sedimentary-facies succession in space and the simultaneity of environmental changes in time, 25 third-order sequences could be discerned in the Upper Paleozoic strata in the Dianqiangui basin and its adjacent areas. On the basis of the two kinds of facies-changing surfaces and the two kinds of diachronisms in stratigraphic records, the regional Late Paleozoic sequence-stratigraphic framework in the Dianqiangui basin and its adjacent areas can be established. There are two types of facies-changing surfaces and two types of diachronisms in stratigraphic records: the static type, a result of the change in sedimentary facies in space, and the dynamic type, a result of the change in time. These two types of facies-changing surfaces led to the generation of the two types of diachronisms: the diachronism of facies-changing surfaces that was formed by the static facies-changing surfaces, and the diachronism of punctuated surfaces that was formed by the dynamic facies-changing surfaces. The two types of facies-changing surfaces and the two types of diachronisms in stratigraphic records are the key to the establishment of the sequence-stratigraphic framework. The sequence boundaries could be divided geologically into four types: tectonic unconformity, sedimentary unconformity, drowned unconformity and their correlative surfaces. All of these four types can be further grouped into exposed punctuated surfaces and deepened punctuated surfaces. The tectonic unconformity is similar to Type Ⅰ sequence boundary, and the sedimentary unconformity is similar to Type Ⅱ sequence boundary defined by Vail et al.. In terms of sequence stratigraphy, the tectonic unconformities of the Ziyun movement, the Qiangui epeirogeny and the Dongwu revolution as well as the drowned unconformity in the transitional period from the Permian to the Triassic can be systematically defined and their geological characteristics are briefly presented.

High-Resolution Sequence Stratigraphy and Coal Accumulating Models of the Permo-Carboniferous Coal Measures in Southwestern Shanxi

The Qinshui Basin in southeastern Shanxi Province is an important base for coalbed methane exploration and production in China.The methane reservoirs in this area are the Carboniferous and Permian coals and their thickness are strongly controlled by the depositional environments and the sequence stratigraphic framework.This paper analyzes the high-resolution sequence stratigraphy of the Permo-Carbo-

Distribution regularity of the Ordovician reef-bank reservoir inside sequence stratigraphic ework in central Tarim Basin

Based on the integrated study of the outcrops, the seismic, drilling and logging data of Lianglitage formation in central Tarim Basin, the sequence stratigraphic framework of the platform margin is built, and the Lianglitage formation is divided into 3 third-order sequences. The vertical pattern and lateral distribution for carbonate reef-bank reservoir in sequence stratigraphic framework are analyzed. The reef-bank reservoir mainly developed in highstand system tract of sequence Ssq2, and distributed along the carbonate platform margin of the Middle-Late Ordovician in central Tarim Basin. The mudstone mound, organic reef, granule bank are vertically stacked. Laterally, the area of well shun3-shun4-shun2-shun6 are characterized by multiphase bank reservoir overlapping, and the area of well TZ82 -TZ44 - TZ161 -TZ24 - TZ26 are characterized by multiphase organic reef and bank overlapping. The reef-bank complexes in sequence Ssq2 are the main targets of exploration in central Tarim Basin.

Sedimentary architecture and distribution of intra-platform shoal in sequence framework of Permian Changxing Formation in central Sichuan Basin,SW China

Based on the comprehensive analysis of core, thin section, logging and seismic data, this study carried out the identification and comparison of Permian Changxing Formation sequences, clarified the typical sedimentary architectures of intra-platform shoal, investigated the vertical and horizontal development and distribution of intra-platform shoal in each sequence, and thus established the sedimentary evolution model of shoal body. The study results are reflected in four aspects.First, there are two complete third-order sequences(SQ1 and SQ2) in Changxing Formation in central Sichuan Basin. SQ1 is generally thick in the north and thin in the south, and SQ2 shows a thickness differentiation trend of “two thicknesses and three thinnesses”. Second, the Changxing Formation in central Sichuan Basin mainly develops intra-platform shoal, inter-shoal sea and intra-platform depression subfacies. In the vertical direction, the intra-platform shoal mainly presents two typical sedimentary sequences: stable superposed and high-frequency interbedded. Third, the stable superimposed sedimentary sequence is developed in the shoal belt at the edge of intra-platform depression, which is composed of two shoal-forming periods and located in the highstand systems tracts(HSTs) of SQ1 and SQ2. The high-frequency interbedded sedimentary sequence is developed in the southern shoal belt of intra-platform depression, which is composed of four shoal-forming periods and mainly located in the HST of SQ2. Fourth, during the SQ1 deposition, the intra-platform shoal was mainly developed at the edge of the intra-platform depression on the north side of the study area, and the inter-shoal sea subfacies was mainly developed on the south side. During the SQ2 deposition, the intra-platform shoal was widely developed in the area, forming two nearly parallel intra-platform shoal belts. The study results provide direction and ideas for exploration of Changxing Formation intra-platform shoal reservoirs in central Sichuan Basin.

Study on Carbonate Sequence Stratigraphy of Ordovician in Northern Ordos Basin

The formation of carbonates is different from that of siliciclastics. The controlling factors, such as the in-situ production of carbonates the transport, local variation in depositional processes and the way of dispersal are unique to carbonates systems, and have resulted in the formation of a wide variety of stratal patterns. The authors believe that all the factors influencing the formation of carbonates, such as the evolution of carbonate platform, transgression and regression, drowning and exposing of the platform, should be taken into consideration during the study of carbonate sequence stratigraphy.This paper attempts to summarize the study procedure in outcrop sequence stratigraphy and to describe the integrated identification of condensed section, first flooding surface and maximum flooding surface, so that the framework of high-resolution sequence stratigraphy can be constructed. During the Sandokan in early Ordovician, a carbonate-siliciclastic ramp was developed in northern Ordos, which changed into a carbonate rimmed shelf or a distally steepened ramp during the Zhuozishan and Kelimoli. It was the break in the Wulalike and Middle Ordovician,changing the sedimentary setting into an aulacogen According to the basin evolution, the authors have established some different idealized models for depositional sequences and systems tracts.

Depositional Sequences of Yitong Graben (Eastern China) and Its Response to Transform-Extensional Processes

The Yitong graben is located in the northeastern segment of the Tertiary rift system in East China. The graben is bounded by a steep dipping transform fault on the northwestern side and subparallel normal faults on the southeastern side, with very thick marginal fan complexes indicating syntectonic sedimentation. The graben is infilled with Tertiary sediments up to 6 000 m thick, in which a series of different scaled hiatuses and tectonic inversion events have been discerned during hydrocarbon exploration. According to regional and local conformities, the basin infill may be divided into three tectonic sequences, among which the major sequence TS2 is further subdivided into three sequence sets and fourteen subsequences. Based on the sequence stratigraphic framework, depositional system tracts which are characterized by marginal fan complexes on both sides of basin and deep or shallow lacustrine deposits in the central part are reconstructed. The subsidence curves show that the graben had undergone several rapid subsidence episodes, which is interpreted to have been caused by multiple stretching of the lithosphere. Integrative analysis of the depositional structural features shows that the regional tectonic stress system experienced a transformation from dextral transformational shear through thermal subsidence to sinistral compressional shear with a general extensional setting. Extension and wrenching dominated the graben evolution and affected the depositional style in different evolutionary stages, the spatial configuration of depositional system and its relationship with unconformities. The conclusions have been applied with some successes to studying the reservoir and hydrocarbon source rock distribution and lithologic stratigraphic traps in this basin.

Geometric and Dynamical Characteristics of Sequences in Yitong Graben

Yitong graben belongs to the north segment of the Tanlu fault belt .It was infilled with Eogene, Neogene and Quaternary clastic deposits, each Of them represents a distinct tectonic sequence.Six types of systems association characteristics of distinct depositional systems and spatial disposition are identified in different evolutionary period of the graben.Sequence Stratigraphic framework of the graben is mainly controlled by structural framework,tectonic movement, sources supply, expanding and contracting cycle of lake, position of depositional center. The key factors are structural framework and tectonic movemeat.Through systematic analysis Of regional tectonic settings, it is recognized that Eogene tectonic sequence of Yitong graben was formed under tenso-shear regime. It includes four sequences indicating four tectonic events attributed to tectonic movement of marginal faults.Neogene tectonic sequence was formed under compresso-shear regime, which includes coarse clastic deposits with a thicknessof 0-500m.Pattern of in the Yitong graben indicates the asymmetrical subsisence of marginal faults along two sides and the complicated structural framework.

Sequence-stratigraphic frameworks and their palaeogeographic patterns for the Permian Lopingian of the Dianqiangui Basin and its adjacent areas of Southwestern China

The Permian Lopingian in the Dianqiangui Basin and its adjacent areas is marked by the coal measures of the Wuchiapingian and the carbonate strata of the Changhsingian stages. For the Lopingian of the Dianqiangui Basin and its adjacent areas,the diversity of sedimentary facies and the obviousness of facies change provide an advantaged condition on a study of sequence stratigraphy. Approximately,the Wuchiapingian stage constitutes a third-order sequence and the Changhsingian stage forms an-other. For the Wuchiapingian stage in the study area,coal-measures were developed on the attached platform and,in addition,a special coal-measure that is composed of both limestone beds and coal beds was also developed in the central part of some isolated platforms. Grain-bank grainstones and packstones were formed on the margin of the attached platform as well as in the windward part of iso-lated platforms. For the Changhsingian stage in the study area,open-platform limestones were formed on the attached platform,while sponge-reef limestones were developed both on the margin of the at-tached platform and on the isolated platforms. The Lopingian Series is a set of basin-facies muddy shales with interbeds of silicalites in the inter-platform basin,which appears a set of the large-thick coarse clastic strata of molasses covering direct the deep-water strata from the Devonian to the Per-mian Yangsingian in the Qinzhou-Fangcheng region in the southern part of the study area. All of these features indicate the complexity of temporal-spatial facies-changes. Sequence-stratigraphic frame-works could be established,which would illustrate two types of facies-changing surfaces and dia-chronisms in the stratigraphic records,based on the combination of both biostratigraphic and chronostratigraphic materials and the regularity reflected by temporal evolutionary succession of sediments as well as spatial distributional patterns of sedimentary facies. Ultimately,features of sedi-mentary succession and palaeogeographical evolution of the Permian Lopingian in the study area are revealed clearly in a series of the panel diagrams of sequence-stratigraphic frameworks and the outline maps showing the sedimentary-facies and palaeogeography. The Permian Lopingian formed by two third-order sequences differs from the stratigraphy of the same era characterized by the constant re-gression along Euramerica. Most specially,if the end-Guadalupian mass-extinction event is genetically related to a regressive event represented by the unconformity of the first episode of the Dongwumovement in the study area,the mass-extinction event at the turn from the Permian to the Triassic is genetically related to a rapid transgressive event re-flected by the drowning unconformity in the study area. These phenomena might reveal a complex rela-tionship between mass-extinction events and trans-gressive-regressive events.

鄂尔多斯盆地庆城油田延长组页岩层系层序地层与沉积相特征

鄂尔多斯盆地三叠系延长组页岩层系蕴藏着丰富的油气资源,但其层序格架及沉积相展布存在较大的争议,从而影响着页岩油气的精细勘探与开发。以庆城油田西233区块为例,应用岩心、测井及最新的三维地震资料重构了层序地层格架及沉积相分布。研究表明,在延长组原长81—长32砂组内,地层向湖盆中心呈进积叠置样式,可分为2个长期基准面旋回和10个中期基准面旋回。在每个中期旋回内,向盆地方向的古地貌依次为浅水带、斜坡带和盆底带。浅水带主要发育三角洲;斜坡带发育重力流水道,顺斜坡呈窄条带状分布;在盆底带近端发育重力流朵叶体沉积,砂体夹于泥页岩中,而盆底带远端主要为深湖页岩夹滑塌体沉积。原长7油层组页岩层系为1套穿时地层,由多个中期旋回的斜坡带下部、盆底带湖底扇砂体和半深湖—深湖泥岩组成。这一研究不仅对鄂尔多斯盆地夹层型页岩油的有效开发(开发区优选及水平井部署)具有重要的指导作用,亦对拗陷湖盆层序与沉积演化理论的发展具有一定的促进作用。

塔里木盆地塔河油田T738井区一间房组高精度层序地层格架内沉积微相特征

塔河油田T738井区一间房组地质年代老、埋藏深度大,虽经历了复杂的构造与成岩改造,但仍具有良好的储集性能。目前该井区重点勘探开发主要集中在断裂带发育部位,以断溶体为主要钻探目标。然而,礁滩相勘探潜力巨大,但是对影响碳酸盐岩礁滩相储层发育沉积相认识的不足制约了勘探突破。本研究基于塔河油田T738井区重点井钻测井资料的分析和薄片鉴定工作,建立了T738井区一间房组高精度层序地层格架,总结了一间房组开阔台地内沉积微相常规测井相模式,对沉积微相类型和特征分别进行了划分和描述,分析了四级层序内部礁滩体厚度分布和沉积微相平面展布特征。结果显示,一间房组划分为1个三级层序(Sq1)和3个四级层序(Ssq1、Ssq2和Ssq3),在开阔台地相识别出高-中-低能滩、丘滩间、生物礁(丘)等几种沉积微相。其中,颗粒滩在常规测井判别值域分别对应AC为51~61μs/m,DEN为2.5~2.6 g/cm^(3),CNL为1%~6%,RD为80~3000Ω·m。一间房组Ssq1层序礁滩体规模较小且孤立,仅分布在地势相对高部位,归因于其在三级层序内所处的海侵体系域低部位,水动力条件较弱。Ssq2、Ssq3层序礁滩体位于三级层序内高位体系域,其规模较大、连片性较好,厚度稳定,最大累计厚度达40 m。

The marine Triassic sequence stratigraphy of Lower Yangtze

Based on detailed field observation and multidisciplinary studies of integrated stratigraphy, the marine Lower and Middle Triassic of Lower Yangtze region is divided into five third order sequences, the general approach of the outcrop sequence stratigraphical study of carbonate ramp is proposed, the pattern in the development of the Early and Middle Triassic sequence under the major regression is summarized, and the sequence stratigraphical and chronostratigraphical frameworks across various paleogeographical facies zones on the marginal platform are established.

中国陆相盆地层序地层格架及模式

陆相盆地与海相盆地的层序地层之间存在地质基础的差异性,主要体现在构造、沉积、层序形成的主控因素和油气生成、运移诸方面。在陆相盆地层序地层的研究中,划分、对比层序以及建立等时格架与模式,需要新的思路和更精细有效的方法。在凝缩体的概念、陆相盆地中湖相沉积层序形成的主控因素、体系域的划分以及陆相层序地层学的研究方法等方面,提出了探讨性的意见。在对各类陆相盆地层序特征分析的基础上,结合近年来的实际勘探情况和建立陆相盆地层序地层模式的可能,根据坡折带的有无,将陆相盆地划分成2个或3个体系域,建立了断陷型盆地、坳陷型盆地和陆内前陆盆地的沉积体分布格架和地层层序模式,为在陆相盆地中进行油气勘探提供了理论指导。

松辽盆地层序地层格架及油气聚集规律

本文通过对松辽盆地典型地区的解剖和分析 ,建立起松辽盆地上侏罗统—上白垩统地层格架 ,并按层序四分原则划分出体系域和准层序。对不同超层序发育特征进行了描述 ,并指出油气在不同体系域内的生储盖规律及其隐蔽性油气藏类型。

济阳坳陷古近系区域层序地层格架地层特征对比

综合生物地层学、磁性地层学(ESR测年法)、地震地层学及层序地层学等地层学的研究成果,通过对断陷盆地区域等时界面的识别、界面级次和界面性质的分析与对比,以三级层序为基本组构单元建立了济阳坳陷古近系区域层序地层格架系统。通过分析济阳坳陷4大次级凹陷古近系各二级层序和隐蔽油气藏最为发育的重点三级层序的可对比性,认为二级层序完全受构造幕的直接控制,具有很好的可对比性。4个次级凹陷的重点三级层序的旋回性质具有一致性,标志性沉积物出现于相同或类似的旋回位置。然而,T2(沙一段底)、T4 (沙三段上亚段底)和T6(沙三段中亚段底)三级层序界面的性质在不同凹陷问具有明显的差异性。从层序成因动力学角度来解释,这种旋回性质的相似性和界面性质的差异性分别表明了:同一层序地层格架中沉积环境对沉积物类型起决定性的影响作用,以及渤海湾盆地构造沉降、沉积中心的迁移对层序界面性质具有主要的控制作用。

三级基准面旋回内三角洲砂体骨架模型的建立——以陕北安塞三角洲露头为例

三角洲砂体是中国陆相盆地最重要的油气储集层之一,建立层序地层格架内三角洲砂体骨架露头地质模型,对于三角洲砂体分布预测有重要意义。对鄂尔多斯盆地东缘多个延长组曲流河三角洲露头剖面开展了深入的高分辨率层序地层学研究,正确识别出以长61下部下切河谷底面以及对应整合面为界面的三级基准面旋回,构建了三级基准面旋回格架内三角洲砂体骨架原型模型,建立了三级基准面旋回内三角洲平原分流河道(河流)样式响应模式图。该项研究表明,三级基准面旋回过程中,不同基准面升降速率下分流河道发生规律性的下切、充填、迁移、漫溢及河型改变,控制了层序地层格架内三角洲砂体的类型、形态、规模和连通性。这对于认识三角洲砂体的分布规律,分析三角洲砂体形成岩性地层圈闭的条件有重要帮助。深入开展多种地质背景下层序格架内三角洲砂体分布规律研究,有助于实现三角洲砂体分布“成因上可解释、时空上可预测”的层序地层学研究目标。

上扬子区震旦系层序地层格架及其形成的古地理背景

上扬子区的震旦系包括陡山沱组和灯影组,前者包含较多的黑色页岩,而后者则以发育大套白云岩为特征。从岩相序列到米级旋回,从沉积相序列到三级层序,可将浅水台地背景的震旦系划分为5个三级层序。这些三级层序可以进一步归为一个二级层序。以各个主要剖面的层序划分为基础,依据地层记录中的两种相变面和两种穿时性,可以建立研究区震旦系的层序地层格架。其中包含较多的深水黑色页岩系的陡山沱组,反映了大冰期之后海侵作用的特点;与寒武系的变化特征不同,自北西而南东沉积环境由浅变深,该背景中沉积了原生沉积组构保存较为完好的灯影组白云岩,这种变化可能反映了前寒武纪末期特殊的白云石化作用特征,同时也代表了许多有待于进一步研究的沉积学问题。从陡山沱组黑色页岩系到灯影组白云岩,不但构成了一个更大级别的总体向上变浅的沉积相序列,还反映了一个与三级和二级海平面变化过程相响应的缓坡型碳酸盐台地的生长发育过程,该过程较为清楚地显示在系列层序地层格架栅状图和岩相古地理图之中。

安塞地区三叠系延长组层序地层分析

目的详细划分安塞地区延长组层序,论述层序演化特征,并分析层序对油气藏的控制作用。方法在对露头剖面、钻井岩心及测井曲线综合分析的基础上,结合层序界面识别、准层序组样式、层序的划分和对比、沉积体系域识别及其组合样式,划分层序并进行分析。结果把延长组化分为4个三级层序,分别对应长10—长9,长8—长7,长6—长4+5和长3+2—长1期沉积;层序1至层序4分别经历了湖盆形成及扩张期、鼎盛期、回返期、萎缩消亡期;区域规模的储层大都处在低位体系域中。结论层序控制着生储盖的组合、储层的展布及储层的储集性能。