Timing and mechanism of reservoir forming in the Upper Triassic Halahatang Formation,Yuqi block,Tarim Basin,northwestern China

The Yuqi block is an important area for oil and gas exploration in the northern Akekule uplift, Tarim Basin, northwestern China. The Upper Triassic Halahatang Formation (T₃h) within the Yuqi block can be subdivided into a lowstand system tract (LST), a transgressive system tract (TST), and a highstand system tract (HST), based on a study of initial and maximum flood surfaces. Oil in the lowstand system tract of the Halahatang Formation is characterized by medium to lightweight (0.8075 g/cm³–0.9258 g/cm³), low sulfur content (0.41%–1.4%), and high paraffin content (9.65%–10.25%). The distribution of oil and gas is principally controlled by low-amplitude anticlines and faults. Based on studies of fluorescence thin sections and homogenization temperatures of fluid inclusions, reservoirs in the T₃h were formed in at least two stages of hydrocarbon charge and accumulation. During the first stage (Jurassic–Cretaceous) both the structural traps and hydrocarbon reservoirs were initiated; during the second stage (Cenozoic) the structural traps were finally formed and the reservoirs were structurally modified. The reservoir-forming mechanism involved external hydrocarbon sources (i.e. younger reservoirs with oil and gas sourced from old rocks), two directions (vertical and lateral) of expulsion, and multi-stage accumulation. This model provides a theoretical fundament for future oil and gas exploration in the Tarim Basin and other similar basins in northwestern China.     

Seismic geomorphology and depositional system of delta and terminal fan: A case study of the Neogene Shawan Formation in the Chepaizi Uplift,Junggar Basin,China

The mainpurpose of this article is to demonstrate the utility of stratal slice images for exploring the sequence stratigraphy and sedimentology of complex depositional systems. A seismic sedimentological study was performed to map sediment dispersal characteristics of the Neogene Shawan Formation in the Chepaizi Uplift of the Junggar Basin, China. The Chepaizi Uplift is developed on the Carboniferous igneous rock basement that lies at the western boundary of the Junggar Basin. The data sources primarily include lithology, well-logging and seismic data. In the main target strata, the Neogene Shawan Formation can be divided into three fourth-order sequences (SQN₁s₁, SQN₁s₂, and SQN₁s₃), and the sequence SQN₁s₁ is subdivided into three fifth-order sequences (SQN₁s₁¹, SQN₁s₁², and SQN₁s₁³). Based on the established fine-sequence stratigraphic framework, the sedimentary facies types have been identified, they are shallow braided-river deltas, fan deltas, littoral and sublittoral lakes, braided rivers, and terminal fans. Then, stratal slices have been used to clearly depict the boundaries of sedimentary facies. Accurate results have been obtained that characterize braided river channels, terminal fans, littoral and sublittoral lake beaches, and subaqueous distributary channels in the braided-river delta front. Additionally, this seismic sedimentology study reflects variations in source area and evolution history.     

北黄海盆地东部坳陷东南部层序地层特征及沉积体系

以层序地层学为理论指导,通过对地震、钻井、测井及古生物等资料的研究,建立了北黄海盆地东部坳陷东南部的层序格架。研究区的中生界可分为1个一级层序、2个二级层序、5个三级层序,在此层序格架内进行了沉积相划分及沉积体系研究,厘定了扇三角洲、辫状河三角洲、浊积扇和湖泊沉积等4种沉积体系。断陷早期,JSQ1的西部与东部分别发育了中型的扇三角洲与辫状河三角洲沉积体系;断陷中期,西部的扇三角洲沉积体系逐步扩展并在其前端多发育小型浊积扇,东部的辫状河三角洲沉积体系亦持续扩张且在JSQ4沉积期规模达到最大;断陷晚期,KSQ1内仅发育盆缘的小型扇体和滨浅湖相沉积,东部、南部隆起区未接受沉积或沉积较薄并剥蚀殆尽。沉积体系的平面展布和纵向演化受古构造与古地貌的控制。     

Mapping sediment-dispersal characteristics using seismic geomorphology: Late Paleogene to Neogene,Qinan Sag,Huanghua Depression,China

The main objective of this article has been to demonstrate the utility of stratal slice images for exploring the sequence stratigraphy and sedimentology of complex depositional systems. The seismic-geomorphology study and sedimentary interpretation were performed to map sediment-dispersal characteristics from late Paleogene to Neogene in Qinan Sag, located in Huanghua Depression of China. The Qinan Sag is underlain by a non-marine Mesozoic and Cenozoic-age stratigraphic section. Main data types in this study area are lithology, wire-line logs and 3D seismic. The main study strata, Member one of Shahejie Formation to Minghuazhen Formation, divided into two second-order sequences and four third-order sequences. The older of the two second-order sequences, SE, corresponds to the formations from Kongdian to Dongying. The younger of the two second-order sequences, SN, correspond to Guantao and Minghuazhen formations. Guided by third-order sequence-stratigraphic correlations from seismic and wireline-log data, we prepared stratal slices from a three-dimensional seismic volume to reveal high-resolution (10-m) sediment dispersal characteristics in a relative geologic-time domain. Using techniques of 3-D seismic geomorphology, we defined four types of depositional systems: braided deltas, deltas, braided rivers and meandering rivers. Stratal slices indicated that the depositional evolution of these interest sequences was from braided-delta front to delta front, braided river and finally meandering river system. Many factors related to the structural evolution history controlled the sediment-dispersal characteristics, such as the basin type, dynamic mechanism, faulting activity, subsidence rate and paleo-high.     

哥伦比亚Magdalena盆地V油田沉积及演化特征

通过岩心、录井、测井等资料分析认为研究区为辫状河三角洲沉积,沉积主体为辫状河三角洲前缘亚相,只在研究区北端为辫状河三角洲平原沉积。研究区Guaduas组经历了两期湖平面的升降旋回,十几个短期旋回。由于辫状河道频繁改道,河漫滩以及水下分流河道间湾沉积形成的隔夹层分布广泛,储层的连通性变差,形成非常复杂的油水系统。储集砂体主要是水下分流河道与河口坝,物性受沉积微相的控制,河口坝砂体储层物性最好,水下分流河道次之,辫状河道最差。     

琼东南盆地陵水组层序格架及沉积体系的时空配置关系

利用层序地层学、沉积学原理和方法,对琼东南盆地古近系陵水组进行了层序划分和沉积体系时空配置关系的研究。建立了陵水组的层序地层格架,将其划分为Els3、ElS2和Elsl三个三级层序,其层序和体系域变化主要受控于凹陷内沉降中心的分布位置,沉积主要受控于盆地边缘的断坡带。每个三级层序低位体系域发育局限,海侵与高位体系域发育。沉积体系构成以扇三角洲、三角洲、滨海平原和浅海为主。探讨了沉积体系的演化,总结了其时空配置关系的特点。     

Sequence stratigraphy,sedimentary facies and reservoir quality of Es4s,southern slope of Dongying Depression,Bohai Bay Basin,East China

Thin-bedded beach-bar sandstone reservoirs are common in the Eocene Shahejie Formation (Es4s) of Niuzhuang Sag, along the southern gentle slope of the Dongying Depression. Here we report on the link between sequence stratigraphy, sedimentary facies and diagenetic effects on reservoir quality. Seismic data, wireline logs, core observations and analyses are used to interpret depositional settings and sequence stratigraphic framework. Petrographic study based on microscopic observation of optical, cathodoluminescence (CL), confocal laser scanning (LSCM) and scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses were used to describe the fabric, texture, allogenic and authigenic mineralogy of these highly heterogeneous sandstone reservoirs. The Es4s interval is interpreted as third-order sequence, composed of a lowstand systems tract (LST), a transgressive systems tract (TST) and a highstand systems tract (HST). On the fourth order, twenty-nine parasequences and seven parasequence sets have been identified. Sand bodies were deposited mainly in the shoreface shallow lake beach-bar (clastic beach-bar), semi-deep lake (carbonate beach-bar) and the fluvial channels. The depositional and diagenetic heterogeneities were mainly due to the following factors: (1) fine grain size, poor sorting, and continuous thin inter-bedded mud layers with siltstone/fine-sandstone having argillaceous layers in regular intervals, (2) immature sediment composition, and (3) even with the dissolution of grains and several fractures, destruction of porosity by cementation and compaction. Secondary pores from feldspar dissolution are better developed in sandstones with increased cementation. Grain coating smectite clays preserved the primary porosity at places while dominating pore filling authigenic illite and illite/smectite clays reduced permeability with little impact on porosity. Due to the high degree of heterogeneity in the Es4s beach-bar interval, it is recognized as middle to low permeable reservoir. The aforementioned study reflects significant insight into the understanding of the properties of the beach-bar sands and valuable for the comprehensive reservoir characterization and overall reservoir bed quality.     

Provenance identification and sedimentary analysis of the beach and bar systems in the Palaeogene of the Enping Sag,Pearl River Mouth Basin,South China Sea

During deposition in the Palaeogene, the Pearl River Mouth Basin (Enping Sag) was filled by sediments derived from northern and southern source regions. The northern sources are the fold belt Caledonian and Hercynian metamorphic rocks that are widely exposed along the South China block and stacked with Mesozoic igneous rocks, and the southern sources are Mesozoic igneous rocks from the southern Panyu lower uplift. We analysed the characteristics of the provenance and sediment-dispersal patterns of the beach and bar systems in the Palaeogene third-order sequence framework on the basis of detritus, thin section, zircon and the geophysical response test data. The source and deposition areas were distinguished based on their palaeogeomorphology. The sedimentary material composition of the deposition area was determined based on the characteristics of the detrital assemblage and cathode luminescence, and the characteristics of the age distribution were determined in detail using detrital zircon U–Pb dating. This study suggests that the provenance system in the Palaeogene mainly consisted of Palaeozoic metamorphic rocks and Mesozoic igneous rocks, with a supplement of Proterozoic metamorphic rocks. The transport capacity of three large fault troughs that delivered the northern provenances gradually increased from the Wenchang Formation (E₂w) to the Enping Formation (E₃e), whereas the southern provenances were transported by four or five incised valleys in E₂w and then submerged in E₃e. In the 3D seismic area, the features of the beach and bar sedimentary systems were described and interpreted based an analysis of the well-based sedimentary facies, seismic reflection characteristics and multiple attribute clustering. The results show that the beach and bar systems by the short-axis braided deltas mainly developed in the upper member of E₂w and that the beach and bar systems on the subaqueous high in E₃e developed during the Palaeogene. In addition, the bedrock-beach bar sedimentary system in the lower member (E₃e^L) was transferred to the braided delta–beach bar sedimentary system in the upper member (E₃e^U).     

Diagenetic alterations related to marine transgression and regression in fluvial and shallow marine sandstones of the Triassic Buntsandstein and Keuper sequence,the Paris Basin,France

The distribution of diagenetic alterations in Triassic fluvio-deltaic, quartzarenitic to sublitharenitic, lowstand systems tract (LST) sandstones of the Grès á Voltzia Formation, anastomosing fluvial, quartzarenitic transgressive systems tract (TST) sandstones of the Grès á Roseaux Formation, and shallow marine, quartzarenitic to sublitharenitic, TST sandstones of the Grès Coquiller Formation, the Paris Basin (France), can be linked to transgression and regression events, and thus to the sequence stratigraphic context. Near-surface eogenetic alterations, which display a fairly systematic link to the depositional facies and sequence stratigraphic framework, include: (i) cementation by meteoric water calcite (δ¹⁸O=−8.9‰ and δ¹³C=−9.1‰) in the fluvio-deltaic, LST sandstones, (ii) cementation by mixed marine–meteoric calcite (δ¹⁸O=−5.3‰ to −2.6‰ and δ¹³C=−3.9‰ to −1.3‰) and dolomite (δ¹⁸O=−4.6‰ to −2.6‰ and δ¹³C=−2.9‰ to −2.3‰) in the foreshore, TST sandstones and below parasequence boundaries (PB), and transgressive surface (TS), and in the shoreface, TST sandstones below maximum flooding surfaces (MFS), being facilitated by the presence of carbonate bioclasts, (iii) dissolution of detrital silicates and precipitation of K-feldspar overgrowths and kaolinite, particularly in the fluvio-deltaic, LST sandstones owing to effective meteoric water circulation, and (vi) formation of autochthonous glauconite, which is increases in abundance towards the top of the fluvio-deltaic, LST sandstones, and along TS, and in the shoreface, TST sandstones, by alteration of micas owing to the flux of seawaters into the sandstones during transgression, whereas parautochthonous glauconite is restricted to the TS sandstones owing to marine reworking. Mesogenetic alterations, which include cementation by quartz overgrowths and illite, display fairly systematic link to fluvio-deltaic, LST sandstones. This study has revealed that linking of diagenesis to transgression and regression events enables a better understanding of the parameters that control the spatial and temporal distribution of diagenetic alterations in sandstones and of their impact on reservoir quality evolution.     

辽河拗陷东部凹陷南部地区古近系沉积体系与储层评价

Detailed studies on a number of core sections,well logs and seismic date of the paleogene systems of the southern part of eastem sag in Liaohe Depression revealed theat six sedimentary systems,i,e.delta,lake,fan delta,braided river,delta,river and alluvial fan,were distinguished,The sedimentation in the studied area remarkably controlled reservoir and the variability of sedimentary facied caused the diversity of reservior sand bldies and the inhomogeneity of reservoir properties plane distribution;The best reservoir properties are the sand bodies of deltaic front and braided-river deltaic front;the better are the sand bodies of braided-river deltaic plain,deltaic front,braided river and meandering river;the medium reservoir properties are the sand bodies of delta plain,the fan-delta front,the alluvial-middle fan,beach-bar and turbidite fan;the wores are the sand bodies of upper fan and lower fan of alluvial fan,alluvial plain.The favorable sedimentary facies belt controlled the distribution of favorable reservoir and it was an important evidence for prediction favorable stratigraphiv reservoir.     

Sedimentary facies associations and sequence stratigraphy of source and reservoir rocks of the lacustrine Eocene Niubao Formation (Lunpola Basin,central Tibet)

The Eocene Niubao Formation of the Lunpola Basin, a large Cenozoic intermontane basin in central Tibet, is an important potential hydrocarbon source and reservoir unit. It represents ∼20 Myr of lacustrine sedimentation in a half-graben with a sharply fault-bounded northern margin and a low-angle flexural southern margin, resulting in a highly asymmetric distribution of depositional facies and sediment thicknesses along the N-S axis of the basin. An integrated investigation of well-logs, seismic data, cores and outcrops revealed three third-order sequences (SQ1 to SQ3), each representing a cycle of rising and falling lake levels yielding lowstand, transgressive, and highstand systems tracts. Lowstand systems tracts (LST) include delta and fan delta facies spread widely along the gentle southern margin and concentrated narrowly along the steep northern margin of the basin, with sublacustrine fan sand bodies extending into the basin center. Highstand systems tracts (HST) include expanded areas of basin-center shale deposition, with sublacustrine fans, deltas and fan deltas locally developed along the basin margins. Sequence development may reflect episodes of tectonic uplift and base-level changes. The southern margin of the basin exhibits two different structural styles that locally influenced sequence development, i.e., a multi-step fault belt in the south-central sector and a flexure belt in the southeastern sector. The sedimentary model and sequence stratigraphic framework developed in this study demonstrate that N2 (the middle member of Niubao Formation) exhibits superior hydrocarbon potential, characterized by thicker source rocks and a wider distribution of sand-body reservoirs, although N3 (the upper member of Niubao Formation) also has good potential. Fault-controlled lithologic traps are plentiful along the basin margins, representing attractive targets for future exploratory drilling for hydrocarbons.     

Tectono-stratigraphy of Lower Cretaceous Tanan sub-basin,Tamtsag Basin,Mongolia: Sequence architecture,depositional systems and controls on sediment infill

Tanan sub-basin is an active-fault bounded basin. The spatial distribution and temporal evolution of depositional systems were significantly influenced by tectonics. Fault movement and stages of basin development controlled the subsidence rates and the potential for erosion and the rate of sediment supply. Distinct stages of rift evolution during the early Cretaceous can be recognized, namely the early syn-rift, rift climax and late syn-rift stages. Three types of lacustrine sequence, consisting of distinctive depositional systems, are distinguished: (1) the early syn-rift sequences (SQ1 + SQ2), which are composed mainly of fan delta and shallow lacustrine depositional systems; (2) the rift climax sequences (SQ3) which developed in response to rapid and differential tectonic subsidence rates, and consist of fan delta, deep lacustrine and sublacustrine fan depositional systems; and (3) the late syn-rift sequences (SQ4) which are comprised of braided-delta and shallow lacustrine depositional systems. Each of the three lacustrine sequence architectures stands for a particular stage of basin fill and reflects variable rates of basin subsidence. Within each sequence, depositional systems and their stacking patterns are interpreted to have been a function of the interaction between tectonics and sediment supply. Differential subsidence across the basin, related to rotation of fault blocks, resulted in the formation of distinct paleomorphologies in different structural settings. These settings were fault-scarp zones controlling the development of fan-deltas, fault-terrace zones controlling the development of fan-delta and sublacustrine fans, half-graben dip-slope zones controlling the development of braided river and braided deltas, and intra-basinal fault-break zones controlling the development of sublacustrine fans. During the late syn-rift stage, active tectonism, displacement on the boundary faults had ceased. At this stage the depositional systems and their stacking patterns were dominantly related to the sediment supply rates, and not to tectonic activity.     

Three-dimensional facies architecture analysis using sequence stratigraphy and seismic sedimentology: Example from the Paleogene Dongying Formation in the BZ3-1 block of the Bozhong Sag,Bohai Bay Basin,China

The Bohai Bay Basin is a classic non-marine rift basin in eastern China. The Paleogene Dongying sequences are the main hydrocarbon-bearing stratigraphic unit in the basin. Using three-dimensional (3-D) seismic data and one well control in the BZ3-1 Block in the western slope of the Bozhong Sag, we analyzed 3-D facies architectures of the Dongying sequences. The Dongying Formation, a second-order sequence, can be subdivided into four third-order sequences (from base to top: SQ1, SQ2, SQ3, and SQ4). The facies architecture was analyzed by using the seismic sedimentology approach based on 3-D seismic data. Sediment of the Dongying sequences was derived from the northern Shijiutuo Uplift via four major configurations of incised valleys, namely “V”, “U”, “W”, and composite shaped incised valleys. Seismic stratal slices reveal branching and converging characteristics of the channels from upstream to downstream. On the basis of an integrated analysis of well log, core data, seismic facies based on multi-seismic attributes, three sedimentary facies (e.g., “delta”, “fan-delta”, and “shore” or “shallow lacustrine” facies) have been recognized. The four types of incised valleys and their evolution control the sedimentary systems in the sedimentation area. The numbers and sizes of the fans are controlled by the sedimentary systems at various scales. Incised valley-fill and deltaic sand bodies are excellent hydrocarbon reservoirs and potentially good exploration targets for the study area. The reservoir quality of sequences SQ1, SQ2, and SQ3 become better gradually from base to top. The proposed sediment dispersal patterns may aid in the prediction of potential reservoir distribution. This study also demonstrates that facies architecture analysis using sequence stratigraphy and seismic sedimentology may serve as an effective approach for constructing 3D facies models for petroleum exploration in areas lacking of well or outcrop data.     

Facies sequences in large-volume debris- and turbidity-flow deposits from the Pyrenees (Cretaceous; France,Spain)

Facies types and depositional models for thick gravity-flow deposits are inferred from Cretaceous Pyrenean examples occurring in different sedimentary settings: basin-plain during relative low sea level stand; slope-apron or deep valleys during relative sea level rise; and slope during relative sea level rise. The depositional units are interpreted as debrites, debrite-turbidite couplets, and megaturbidites. They are a function of transport distance and hydraulic jump by liquefaction and phase separation in large subaqueous flows.     

塔东北地区白垩系辫状河沉积特征研究

根据沉积构造、沉积层序特征及测井剖面对比分析,对塔东北地区白垩系的沉积相进行了研究,认为该地区为辫状河沉积,明确了辫状河沉积相的时空展布和变化规律.研究表明,白垩系沉积时期,古水流由塔东北地区的北部隆起和南部高地向中间低洼地区汇集,在整个地区广泛分布辫状河道、河间砂坝及漫滩沉积微相, 储集层主要为辫状河道和河间砂坝砂砾岩和中粗砂岩.沉积构造主要有各种层理构造和侵蚀构造.储集层常见单一河道层序、河道-砂坝复合体及多层楼式河道沉积层序.     

Geological roles of the siltstones in tight oil play

Understanding the hydrocarbon accumulation pattern in unconventional tight reservoirs is crucial for hydrocarbon evaluation and oil/gas extraction from such reservoirs. Previous studies on tight oil accumulation are mostly concerned with self-generation or from source to reservoir rock over short distances. However, the Lucaogou tight oil in Jimusar Sag of Junggar Basin shows transitional feature in between. The Lucaogou Formation comprises fine-grain sedimentary rocks characterized by thin laminations and frequently alternating beds. The Lucaogou tight silt/fine sandstones are poorly sorted. Dissolved pores are the primary pore spaces, with average porosity of 9.20%. Although the TOC of most silt/fine sandstones after Soxhlet extraction is lower than that before extraction, they show that the Lucaogou siltstones in the area of study have fair to good hydrocarbon generation potential (average TOC of 1.19%, average S₂ of 4.33 mg/g), while fine sandstones are relatively weak in terms of hydrocarbon generation (average TOC of 0.4%, average S₂ of 0.78 mg/g). The hydrocarbon generation amount of siltstones, which was calculated according to basin modeling transformation ratio combined with original TOC based on source rock parameters, occupies 16%–72% of oil retention amount. Although siltstones cannot produce the entire oil reserve, they certainly provide part of them. Grain size is negatively correlated with organic matter content in the Lucaogou silt/fine sandstones. Fine grain sediments are characterized by lower deposition rate, stronger adsorption capacity and oxidation resistance, which are favorable for formation of high quality source rocks. Low energy depositional environment is the primary reason for the formation of siltstones containing organic matter. Positive correlation between organic matter content and clay content in Lucaogou siltstones supports this view point. Lucaogou siltstones appear to be effective reservoir rocks due to there relatively high porosity, and also act as source rocks due to the fair to good hydrocarbon generation capability.     

辽东湾晚第四纪层序地层

通过对辽东湾高分辨率浅地层剖面声学地层与典型钻孔沉积地层的对比分析,揭示了研究区晚第四纪MIS5以来的地层层序。辽东湾高分辨率浅地层剖面自下而上划定的6个声学地层单元(SU5、SU4、SU3、SU2、SU12、SU11)与钻孔岩芯划分的6个沉积地层单元(DU5、DU4、DU3、DU2、DU12、DU11)具有良好的对应关系。分别与MIS4期、MIS2期低海面时期的沉积间断密切相关的两个层序界面R5、R3,将辽东湾识别出的地层单元自下而上划分为3个层序(SQ3、SQ2、SQ1)。其中SQ3仅识别出上部的海侵体系域与高水位体系域,对应MIS5期海平面相对较高时期的滨浅海相沉积(DU5);SQ2自下而上由低水位体系域(MIS4期的河流相与河道充填相沉积(DU4))与海侵体系域(MIS3期早中期滨海相沉积(DU3))组成;SQ1自下而上包括低水位体系域(MIS2期的河流相与河道充填相沉积(DU2))、海侵体系域(全新世早中期滨海相沉积(DU12))高水位体系域(全新世高海面以来的浅海相沉积(DU11))。研究区的海侵体系域厚度较薄且变化较小,分布广泛,而低水位体系域厚度与横向分布均变化较大。     

Formation and distribution of coal measure source rocks in the Eocene Pinghu Formation in the Pinghu Slope of the Xihu Depression,East China Sea Shelf Basin

The Xihu Depression in the East China Sea Shelf Basin is a large petroliferous sedimentary depression, in which oil and gas reservoirs were mainly discovered in the Pinghu Slope and the central inversion zone. The oil-gas source correlation in the Xihu Depression was analyzed by hydrocarbon generating thermal simulation data via gold-tube pyrolysis experiments. The results indicated that the oil and gas in the Xihu Depression were mainly derived from coal measure source rocks of the Eocene Pinghu Formation. Therefore, the identification of coal seams is extremely crucial for evaluating coal measure source rocks in the Pinghu Formation in the Xihu Depression. Geochemical and petrological characterization pointed to input of terrigenous organic matter and redox conditions of the depositional environment as factors that govern the ability of the coal measure source rocks in hydrocarbon generation in the Xihu Depression. In this regard, the sedimentary organic facies in the Pinghu Formation were classified into four predominantly terrigenous and one mixed-source subfacies, which all varied in carbon and hydrogen content. The coal measure source rocks in the carbon- and hydrogen-rich tidal flat-lagoon exhibited the highest hydrocarbon generation potential, whereas the mudstone in the neritic facies was the poorest in its hydrocarbon yield. These results suggested that the coal measure source rocks in the Pinghu Formation likely developed in the Hangzhou Slope and the Tiantai Slope, both representing promising sources for oil and gas exploration.     

Physical,biological, geochemical and sedimentological controls on the ichnology of submarine canyon and slope channel systems

Sediments of the continental slope are commonly bioturbated by endo- and epibenthic organisms, particularly in and around submarine canyons and channels. This study reviews the architecture and depositional environments associated with canyons and channels on the continental slope, and assesses the key physical and chemical conditions encountered in and around these conduits. Hydrodynamic energy, concentration and quality of organic carbon, dissolved oxygen concentration and sedimentation rate are identified as key controls on the composition of benthic ecosystems in slope environments. Submarine canyons and channels focus a variety of turbid and clear-water currents, all of which serve to increase the concentration of oxygen, labile organic carbon and other nutrients, which tend to elevate the abundance and biodiversity in the seafloor sediments, compared with those of the surrounding slope. Ancient slope channel and canyon systems reflect some of the variation in ichnological assemblages that is seen in modern analogues, although processes of erosion and trace fossil preservation mean that the benthic environment is often incompletely preserved in the ancient record. By integrating current understanding of sedimentology, oceanography, biology and ichnology of slope environments it is possible to provide a first order summary of the inter-relationships between ichnology and depositional environments on the continental slope. The combination of these data has the potential to improve our understanding of changes in deep marine benthic ecosystems through geological time, and to further the use of ichnology in assessing hydrocarbon reservoir presence, quality and performance from bioturbated slope, canyon and channel-levee hydrocarbon reservoirs.