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1.
Three small turbidite systems (Almeria, Sacratif, and Guadiaro), each tens of kilometres long, are developed in the complex morpho-structural setting of the northern Alboran Sea and have similar primary architectural elements (canyons, channel-levee systems, lobes). However, comparison reveals differences in the axial gradients of their canyons, depth/physiographic location, morphological framework, and lateral and longitudinal sedimentary shifts of turbidite deposition. The depositional architecture and sedimentary evolution from late Pliocene to Quaternary seems to be conditioned by number of submarine feeding sources (canyons), sea-level fluctuations and local tectonic (e.g. margin/canyon-channel gradients, faults). We group the Alboran turbidite systems into two models: mud/sand-rich submarine point-source and mud/sand-rich multiple submarine source ramp.  相似文献   

2.
The Cretaceous Tres Pasos Formation of southern Chile records a slope system characterized by >800 m of paleo-bathymetric relief. Channel deposits are exposed in an outcrop 2.5 km long by 125 m thick and are located in proximity to the toe of a slope clinoform. Exquisite exposures of channel strata offer a unique opportunity for high-resolution analyses of channel stacking patterns and provide insight into the evolution of conduits that transport sediment from continents to the deep ocean.Eighteen slope channels, or channel elements, are present in the strata studied. They are 6–15 m thick and comprised of stacked turbiditic sedimentation units. Channel fills are characterized by a gradational transition from amalgamated sandstone-rich facies in the channel axes to thinly interbedded sandstone and siltstone at the channel margins over distances of 10–30 m. These elements are generally considered to be ∼300 m wide and were formed by punctuated periods of incision and sedimentary bypass, followed by in-filling by collapsing turbidity currents. Out-of-channel deposits consist primarily of fine-grained facies, which are typically covered by vegetation in the study area.The channel strata of the mapped portion of the Tres Pasos Formation can be grouped into three channel complexes 25–70 m thick. Complexes are differentiated based on the preservation of siltstone-dominated deposits (bypass drapes and channel margin), which persist across the entire outcrop belt and coincide with shifts in channel stacking pattern. The oldest four channel elements (channel complex 1) are characterized by the highest lateral offsets, relative to one another. These are interpreted to record the most unconfined channel-stacking pattern present. As the channel system evolved (channel complexes 2 and 3), channel elements began to stack on top of one another, due to the increased confinement imparted on the slope channel system. The amount of vertical offset between successive channel elements preserves the record of channel aggradation as well as erosional degradation. The greatest vertical offset observed is associated with the oldest channels; as the system matured, vertical offset decreased. This decrease in vertical offset is coincident with the decrease in lateral offset of channels. The lateral offset decrease is attributed to establishment of constructional confinement and is the consequence of increased focusing of successive channel-initiating gravity flows. As confinement establishes, channels are predisposed toward underfilled conditions upon abandonment. The capture of channel-initiating currents along channel abandonment relief fairways focused incision and resulted in increased erosion and decreased vertical offset. The consequence of these conditions is an upward increase in channel element amalgamation.The organized stacking of slope channels observed in the Tres Pasos Formation is comparable to that of seismically imaged channel-levee or entrenched slope valley systems. By analogy to these 3-dimentionally constrained systems, a portion of the poorly exposed out-of-channel facies in the Tres Pasos Formation is attributed to aggradational internal levee deposits. The facies insight derived from the studied outcrop provides insight into analogous hydrocarbon-bearing units from numerous continental margins.  相似文献   

3.
The paleogeographic evolution of Campos Basin, a major oil province of Brazil, during the deposition of its giant turbidite reservoirs, was reinterpreted based on the integration of quantitative sandstone petrography and structural analysis of regional 3D seismic data. The major detrital compositional trends indicate that the geodynamic evolution of the continental margin, rather than global eustatic sea-level fluctuations, has exerted the main control on sand supply to the deepwater systems. This control was imposed by the interaction of three geodynamic processes: (i) escarpment retreat of the coastal mountain ridges, (ii) mantle plume-related dynamic uplift and magmatic activity, and (iii) tectonic reactivation of major basement fault-zones. The pattern of distribution of compositional and textural parameters within the turbidite sequences indicated that the sand supply to deepwater was also constrained by high-frequency stratigraphic processes of the climate Milankovitch band. This new approach to the controls on the formation of the sand-rich, deepwater systems in Campos Basin has a key importance for the generation of realistic models for the exploration of new turbidite reservoirs and for the optimized development of producing turbidite oilfields in such a world-class hydrocarbon province. The proposed integrated methodology can help to unravel the controls on the deposition of deepwater sand-rich, deepwater reservoirs in other divergent margin settings.  相似文献   

4.
The existence of a slope equilibrium profile has been widely used to account for erosional and depositional processes on submarine slopes and turbidite systems. Profiles out-of-equilibrium are commonly observed in actively deforming areas where channels seem to be deflected or diverted by seafloor structures. In this study the concept of the submarine equilibrium profile is tested in an area of extensive surface faulting to examine whether channels adopt an equilibrium-type profile through time. The study area is on the slope of the Nile Delta, which is disrupted by a number of surface-rupturing normal faults. Prior to fault linkage, several submarine channels flowed down the slope and either utilised relay ramps or flowed through fault scarps of the fault array. Where a relay ramp had been utilised, post fault linkage, the channels of the area either avulsed or converged into one major channel in response to a change in the deformed slope profile to a more concave shape. The thalweg of the post fault linkage channel and two slope profiles either side of it are measured in the area of the fault array, to understand how the channel evolved in response to the active faulting. When fault displacement is relatively small the combination of channel erosion and aggradation results in a channel thalweg profile near-equilibrium with predictable modifications of channel dimensions (depth and width) even if sediment supply was infrequent and episodic. It is concluded that turbidite channels can conform to the concept of equilibrium and submarine base level if it is the most energy efficient route for submarine gravity flows downslope. The most energy efficient route will be one where flows bypass the slope without eroding or depositing and move in a direct downslope course towards base level.  相似文献   

5.
The reservoir architecture of methane hydrate (MH) bearing turbidite channels in the eastern Nankai Trough, offshore Japan is evaluated using a combination of 3-D seismic and well data. On the 3-D seismic section, the MH-bearing turbidite channels correspond to complex patterns of strong seismic reflectors, which show the 3-D internal architecture of the channel complex. A seismic-sequence stratigraphic analysis reveals that the channel complex can be roughly classified into three different stages of depositional sequence (upper, middle, and lower). Each depositional sequence results in a different depositional system that primarily controls the reservoir architecture of the turbidite channels. To construct a 3-D facies model, the stacking patterns of the turbidite channels are interpreted, and the reservoir heterogeneities of MH-bearing sediments are discussed. The identified channels at the upper sequence around the β1 well exhibit low-sinuosity channels consisting of various channel widths that range from tens to several hundreds of meters. Paleo-current flow directions of the turbidite channels are typically oriented along the north-northeast-to-south-southwest direction. High-amplitude patterns were identified above the channels along the north-to-south and north-northeast-to-south-southeast directions. These roughly coincide with the paleo-current flow of the turbidite channels. An interval velocity using high-density velocity analysis shows that velocity anomalies (>2000 m/s) are found on the northeastern side of the turbidite channels. The depositional stage of the northeastern side of the turbidite channels exhibits slightly older sediment stages than the depositional stages of the remaining channels. Hence, the velocity anomalies of the northeastern side of the channels are related to the different stages of sediment supply, and this may lead to the different reservoir architectures of the turbidite channels.  相似文献   

6.
With abundant well penetrations in proximal and distal settings and 3D seismic coverage, the Auger Basin is an ideal location to study the influence of basin setting and accommodation on the stratigraphic architecture of ancient turbidite systems. Pliocene-age turbidites at Macaroni Field were deposited in ponded accommodation in the distal portion of a salt-bounded intraslope basin, immediately inboard of a sediment spill point to the linked outboard basin. Deposits at Auger Field are contained within point-sourced submarine fans deposited in healed slope accommodation in the more proximal portion of the basin on the flank of a paleo-bathymetric ridge, immediately down depositional dip of a sediment spill point from an inboard basin. Both areas of the basin are distinct in terms of sediment dispersal patterns, rate of sediment fill, and preservation potential of reservoir/seal pairs, and while both fields contain sand-rich deposits and record vertical evolution from older sheet dominated- to younger channel dominated deposits over the Late Pliocene section, there are key differences in the nature in which the fill occurs. The ponded stratigraphic section at Macaroni Field records (1) an early mud-rich phase in which incoming flows are completely captured by confining topography, (2) a brief phase of diminished relief when high frequency fill/spill cycles occur, and ultimately (3) a phase of incision of the former basin sill and large-scale bypass to the outboard basin. Over the same period, the healed-slope section at Auger Field records a fill pattern consisting of alternating episodes of initial sand-rich sheet/lobe deposition followed by intervals of channelization. We acknowledge extra-basinal controls (eustacy, climate) on the timing, rate, and nature of sediment supply to the basin, but there is considerable evidence for paleo-bathymetric control on cyclical fill patterns observed at fourth and higher-order scales.  相似文献   

7.
High-resolution multichannel 2-D and 3-D seismic data, primarily from upper fan reaches of near-seafloor channel-levee systems on the Niger Delta slope and in the Arabian Sea, reveal a high level of detail and architectural complexity. Several architectural elements are common to each system examined in this study. They include inner levees, outer levees, erosional fairways, channel-axis deposits, rotational slumps blocks, and mass transport deposits. Although the scale of individual systems varies significantly, similarities in first-order architectural elements and their configurations suggest that common depositional processes are involved regardless of scale differences.Most of the channel-levee systems examined in this study are characterized by a basal erosional fairway that is bordered by outer levees of varying thickness. Together these elements define the base and margins of the channel-belt, where channel-axis deposits and inner levees are the dominant architectural elements. Vertical, sub-vertical, and lateral stacking patterns of sinuous and/or meandering channels create seismic facies that range from narrow to wide zones of high amplitude reflections (HARs) with chaotic to continuous and shingled to horizontal reflections. Some HARs appear as isolated or stacked asymmetric to symmetric u- and v-shaped reflections, referred to here as channel-forms. Channel-belts evolve within the confines of the scalloped erosional fairway walls (flanked by outer levee), and are similar in morphology to meander-belts in fluvial systems, but commonly have a greater component of vertical aggradation. Detailed study of one particular channel-levee system on the Niger Delta slope shows a period of incision followed by three distinct phases of channel development during its aggradational history. Each fill phase corresponds to a different channel stacking architecture, planform geometry, and nature of terrace development, with important implications for reservoir architecture. In some cases, multiple phases of inner levee growth are observed, each intimately linked to the channel migration and aggradation history. Channel sinuosity evolves dynamically, with some meander loops undergoing periods of accelerated meander growth at the same time that others show little lateral migration.  相似文献   

8.
This study documents the stratigraphic and palaeogeographic distribution of hybrid event beds that comprise both debris-flow (cohesive) and turbidity current (non-cohesive) deposits. This is the first study of such beds in a submarine fan system to combine outcrop and research borehole control, and uses a dataset from the Skoorsteenberg Formation of the Tanqua depocentre in the Karoo Basin, South Africa. Three types of 0.1–1.0 m thick hybrid beds are observed, which have a basal weakly graded fine-grained sandstone turbidite division overlain by a division of variable composition that can comprise 1) poorly sorted carbonaceous-rich material supported by a mud-rich and micaceous sand-matrix; 2) poorly sorted mudstone clasts in a mud-rich sand-silt matrix; or 3) gravel-grade, rounded mudstone clasts in a well sorted (mud-poor) sandstone matrix. These upper divisions are interpreted respectively as: 1) the deposit of a debris-flow most likely derived from shelf-edge collapse; 2) the deposit of a debris flow, most likely developed through flow transformation from turbidity current that eroded a muddy substrate; and 3) from a turbidity current with mudstone clasts transported towards the rear of the flow. All three hybrid bed types are found concentrated at the fringes of lobes that were deposited during fan initiation and growth. The basinward stepping of successive lobes means that the hybrid beds are concentrated at the base of stratigraphic successions in medial and distal fan settings. Hybrid beds are absent in proximal fan positions, and rare and thin in landward-stepping lobes deposited during fan retreat. This distribution is interpreted to reflect the enhanced amounts of erosion and availability of mud along the transport route during early lowstands of sea level. Therefore, hybrid beds can be used to indicate a fan fringe setting, infer lobe stacking patterns, and have a sequence stratigraphic significance.  相似文献   

9.
The Pab Formation consists of deltaic and turbiditic sediments which were deposited during the Late Maastrichtian on the Indo-Pakistani passive margin. The margin geometry has been restored in the Pab Range from a regional transect 120 km long. Two superposed turbiditic systems onlap the slope carbonates and completely pinch-out southward. The lowest turbiditic system (Lower Pab) is a sand-rich basin floor fan, which consists of sand-rich channel complexes distally passing to lobes northward. This basin floor fan is overlain by a mud-rich slope fan formed during the subsequent sea-level rise, which drowned the shelf. The upper turbiditic system (Upper Pab) is a sand-rich slope fan, formed during the progradation of a deltaic system in the shelf setting. It consists of prograding tabular lobes passing upward to conglomeratic channels, and thins out northwards. The Lower Pab turbiditic system consists of three channel complexes (LP1, 2, 3) organised in a backstepping succession. Each channel complex has a multi-storey internal architecture, resulting from the amalgamation of several individual turbiditic channels. Five major facies associations have been determined in the LP3 channel complex. FA-1 corresponds to polygenic and monogenic debris-flows, FA-2 to high-density gravelly or sandy turbidites, FA-3 to by-pass deposits, FA-4 to thin-bedded turbidites (spill-over lobes and levees) and FA-5 to hemipelagites. The downstream evolution of the LP3 channel complex can be studied from canyon to mid-fan settings. Where it is confined in the canyon, the channel complex is 50 m thick and 1 km large, and shows a high sand/shale ratio. The development of overflow deposits is limited and occurs only at the top of the channel complex. At the canyon mouth, the channel complex is still deeply incised but overflow deposits start to expand laterally as a result of the decreased confinement. By-pass facies here are well-developed, and are related to hydraulic jump processes. In the mid-fan setting, the channel complex widens and the sand/shale ratio decreases. Erosion at the channel base is less developed, whereas internal and external levees are well-developed. Spill-over lobes form the last stage of the channel complex infill. The internal geometry of the channel complexes is a result of a complex interaction between lateral confinement, by-pass and lateral migration processes.  相似文献   

10.
The Wollaston Forland Basin, NE Greenland, is a half-graben with a Middle Jurassic to Lower Cretaceous basin-fill. In this outcrop study we investigate the facies, architectural elements, depositional environments and sediment delivery systems of the deep marine syn-rift succession. Coarse-grained sand and gravel, as well as large boulders, were emplaced by rock-falls, debris flows and turbulent flows sourced from the immediate footwall. The bulk of these sediments were point-sourced and accumulated in a system of coalescing fans that formed a clastic wedge along the boundary fault system. In addition, this clastic wedge was supplied by a sand-rich turbidite system that is interpreted to have entered the basin axially, possibly via a prominent relay ramp within the main fault system. The proximal part of the clastic wedge consists of a steeply dipping, conformable succession of thick-bedded deposits from gravity flows that transformed down-slope from laminar to turbulent flow behaviour. Pervasive scour-and-fill features are observed at the base of the depositional slope of the clastic wedge, c. 5 km into the basin. These scour-fills are interpreted to have formed from high-density turbulent flows that were forced to decelerate and likely became subject to a hydraulic jump, forming plunge pools at the base of slope. The distal part of the wedge represents a basin plain environment and is characterised by a series of crude fining upward successions that are interpreted to reflect changes in the rate of accommodation generation and sediment supply, following from periodic increases in fault activity. This study demonstrates how rift basin physiography directly influences the behaviour of gravity flows. Conceptual models for the stratigraphic response to periodic fault activity, and the transformation and deposition of coarse-grained gravity flows in a deep water basin with strong contrasts in slope gradients, are presented and discussed.  相似文献   

11.
Forward seismic models of two ‘seismic scale’ outcrops of different style channel systems have been made to investigate their seismic signature. These two outcrops illustrate the geometric end members of channel stacking architecture in response to low- and high-accommodation space. The Eocene Nohut Tepe channel system of the Elaziğ Basin in eastern Turkey was deposited in an area of high accommodation resulting in an aggradational geometrical offset stacking of channels up against a slope. The Eocene Ainsa II Channel system of the Tremp-Pamplona Basin in the Spanish Pyrenees was deposited in an area of low accommodation resulting in a tabular, compound sheet geometry, with amalgamated channel bodies separated by clay drapes.Depth models were drawn from outcrop photos and converted to impedance models by assigning acoustic impedance properties to the sand filled channels and surrounding and interbedded mud and clay layers. These were the input for the forward seismic models, which constructed various frequency synthetic seismic sections of the two outcrops. Analysis of the outcrop synthetic seismic identified three distinct reflection configurations. Type I is characterised by a strong black peak and white trough reflection, which is due to a discrete channel body. Type II is characterised by multiple offset, time ‘stepped’ black peak reflections that are underlain by one continuous, strong white trough reflection, which is due to offset stacked channel bodies. Type III is characterised by strong black peaks which onlap an underlying, continuous white trough reflection, caused by the lateral amalgamation of channel bodies.These three types of reflection configurations observed on the outcrop synthetic seismic can also be found on actual seismic from channelised turbidite systems, which aids in interpreting channel stacking architecture, accommodation space prediction and depositional styles from the actual seismic data. Channel stacking architecture is clearly an important aspect which needs to be considered when making channel system interpretations based on seismic data.  相似文献   

12.
New high-resolution seismic reflection data collected along the eastern margin of Corsica have been analysed to describe the morphology of the turbidite systems located seaward of the Golo River mouth. The boomer data reveal that there is not only one turbidite system directly associated with the river, but four additional, non-coalescing systems which grew simultaneously. In the south, the system has the typical morphology of a turbidite deposit rich in mud and sand with a well-developed meandering canyon and channel morphology. In the north, they have the morphology of sand-rich turbidite systems with shorter straight channels. The southernmost deposits are interpreted to represent a more advanced stage of turbidite system development. Terraces, recognised by their particular seismic facies on boomer profiles which clearly differs from the surrounding levee facies, are observed in the channel meanders. They are interpreted as confined levees built by vertical accretion due to deposition from low-energy flows. Despite limited penetration, boomer seismics are demonstrated to be a useful complement to lower-resolution sparker data. The boomer data are superior (1) for the characterisation of fine-grained turbidite deposits by extending seawards the limits of the turbidite systems commonly defined by the acoustic response of sands, (2) in demonstrating the persistence of turbiditic processes farther towards the basin, and (3) for proposing conceptual models for the formation of terraces in fan valleys.  相似文献   

13.
Shallow 3D seismic data show contrasting depositional patterns in Pleistocene deepwater slopes of offshore East Kalimantan, Indonesia. The northern East Kalimantan slope is dominated by valleys and canyons, while the central slope is dominated by unconfined channel–levee complexes. The Mahakam delta is immediately landward of the central slope and provided large amounts of sediments to the central slope during Pleistocene lowstands of sea level. In the central area, the upper slope contains relatively straight and deep channels. Sinuous channel–levee complexes occur on the middle and lower slope, where channels migrated laterally, then aggraded and avulsed. Younger channel–levee complexes avoided bathymetric highs created by previous channel–levee complexes. Levees decrease in thickness down slope. Relief between channels and levees also decreases down slope.North of the Mahakam delta, siliciclastic sediment supply was limited during the Pleistocene, and the slope is dominated by valleys and canyons. Late Pleistocene rivers and deltas were generally not present on the northern outer shelf. Only one lowstand delta was present on the northern shelf margin during the upper Pleistocene, and sediments from that lowstand delta filled a pre-existing slope valley complex and formed a basin-floor fan. Except for that basin-floor fan, the northern basin floor shows no evidence of sand-rich channels or fans, but contains broad areas with chaotic reflectors interpreted as mass transport complexes. This suggests that slope valleys and canyons formed by slope failures, not by erosion associated with turbidite sands from rivers or deltas. In summary, amount of sediment coming onto the slope determines slope morphology. Large, relatively steady input of sediment from the Pleistocene paleo-Mahakam delta apparently prevented large valleys and canyons from developing on the central slope. In contrast, deep valleys and canyons developed on the northern slope that was relatively “starved” for siliciclastic sediment.  相似文献   

14.
运用近年来采集的高分辨率地震资料和多波束测深数据,在珠江海谷及西北次海盆深海平原区发现大规模发育的第四纪重力流沉积体系,该沉积体系沿珠江海谷以北西-南南东方向贯穿整个北部陆坡,进入西北次海盆后呈扇形展开,形成珠江海谷-西北次海盆大型深水浊积扇系统。据沉积体系空间展布特征差异,将珠江海谷划分为北、中、南三段,北段为过路侵蚀和水道下切,中段以水道充填和天然堤沉积为主,南段以水道-天然堤和朵叶体沉积共存为特征,揭示出北部陆坡珠江海谷是珠江口外陆缘物质输送海盆深海平原的主要通道;海盆区总体以朵叶体发育为特色,呈扇形展布。深水扇系统可分为三期次沉积体,其区域结构记录了重力流沉积物从侵蚀、卸载到南海海盆作为限制性盆地接收陆源沉积物的全过程,为“源-渠-汇”的研究构建了一个完美的范例。本文以珠江海谷-西北次海盆第四纪深水浊积扇沉积体系为例,完整地揭示了水道-扇体的组构和特征,清晰呈现了陆坡-海盆砂体展布的规律,可为建立南海北部新近纪早期深水扇形成模式提供参考,有助于指导南海深水油气勘探工作。  相似文献   

15.
Based on analysis of well and drilling data, cores, sediment grains and 3D seismic data, four types of turbidites–slope fan, channelized, laminated and sublacustrine fan turbidite–are identified in Members 1 and 2 of the Qingshankou Formation in northern Songliao Basin. The slope fan turbidite is located in Members 1 and 2 of the Qingshankou Formation. It is dominated by silt and fine sand and is distributed in an SN-trending ribbon zone along the slope break at delta front in the western part of the basin. The channelized turbidite is located at the bottom of Member 1 of the Qingshankou Formation. It is dominated by silt and fine sand and is distributed in an SN-trending strip-shaped zone along the Qijia-Gulong sag, with funnel-shaped sublacustrine fans at the end. The laminated turbidite body is located in Member 2 of the Qingshankou Formation. It is dominated by siltstone and argillaceous siltstone and is distributed continuously in a tongue-shaped zone along the northern delta front towards the lacustrine region, with belt-like distributaries at the central part and sublacustrine fans at the end. Low-permeability and low-yield lithologic reservoirs are formed near the delta front within the slope fan turbidite and channelized turbidite. There are “sweet spots” in local regions, where reservoir reform techniques are required to attain high industrial yields. Laminated turbidite and sublacustrine fans can form unconventional and continuous reservoirs that generally have no natural productivity; industrial production is impossible until horizontal drilling and multistage volume fracturing are employed. Therefore, the research results are important to the exploration of unconventional oil and gas reservoirs in northern Songliao Basin.  相似文献   

16.
The role of internal and external forcing of sedimentation in turbidite systems remains a subject of debate. Here we propose new insights from the quantitative analysis of architectural parameters of the Congo Axial Fan.Fifty-two channel-levee-lobe systems, spanning the last ca. 200 ka, are visible on the seafloor, most of them having slightly elongated lobe complexes at their termination. Volumes of lobe complexes (usually 3–196 km3) are highly variable in time and space. The cumulative volume of the lobe complexes represents approximately 30% of the volume of the Axial Fan.The Axial Fan is sequentially divided into periods of increasing/decreasing channel lengths and basinward/landward migrations of avulsion points, representing successive prograding/retrograding architectural patterns called architectural cycles. These cycles are either symmetrical saw toothed and bell-shaped with progressive progradation and retrogradation phases, or asymmetrical, with long-lasting progradation phases and abrupt retrogradation phases that correspond to channel avulsions occurring high up on the fan.Our study points to the interplay between internal and external factors controlling the architecture of the Congo Axial Fan. The local topographic constraint is a major factor in the fan's stacking pattern. However, cyclic evolution of the architecture reveals major shifts in the deposition site that are linked to very upfan avulsion events. These events are interpreted to be driven by external factors (e.g. climate and/or eustatic sea-level change) that were able to drastically increase and/or coarsen the sediment supply to the fan.  相似文献   

17.
Currently, conventional forecasting methods of well-to-seismic integration are unable to identify turbidite channel sandstones due to scarcity of well data in deepwater areas, small geophysical differences between sandstones and mudstones of turbidite channels and strong sandstones heterogeneity. The reservoir prediction of deep-water turbidite channels is still a difficult issue in deep-water research. On the basis of previous studies, we propose a new technology named “reservoir prediction of deep-water turbidite sandstones with seismic lithofacies control” in view of the characteristics of deep-water turbidite sandstones. This new technology improves the reservoir prediction of complex sedimentary systems after classifying seismic lithofacies and connecting lithofacies with rock-physics. Furthermore, it can accomplish the genetic classification statistics of rock-physics, improve conversion accuracy of seismic elastic parameters/reservoir parameters and achieve the quantitative reservoir prediction under the double control of seismic geomorphology and seismic lithofacies. The C block of Lower Congo Basin is characterized by few well data, complex lithology but high resolution-seismic. We use the technology to predict the reservoirs of this area and have achieved excellent results. This has great significance for the later exploration.  相似文献   

18.
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19.
An important hydrocarbon reservoir is hosted by the third member of the Shahejie Formation (Es3) in the Zhanhua Sag, Bohai Bay Basin. Seismic stratal slices reveal different characteristics of channels and fan-delta lobes between the south (slope break belt) and southwest (gentle slope) areas combined with lithology, wire-line logs and three-dimensional (3-D) seismic data in the southern slope of Zhanhua Sag. And an excellent analogue has been provided for understanding various key depositional evolution of fan-deltas in the slope system (from base to top: Es3L, Es3M and Es3U). The Sedsim, a three-dimensional stratigraphic forward modelling programme, is applied to simulate the evolution of fan-deltas in the southern slope break systems and southwestern gentle slope systems of the Zhanhua Sag by considering a number of key processes and parameters affecting the fan-deltaic deposition from 43 Ma to 38.2 Ma. Modelling results indicate that depositional types and scales evolved from the thickest medium-scale gravel- or sand-rich fan deltas (43 Ma ∼41.4 Ma, Es3L) to the thinnest small-scale mud-rich fan deltas and lacustrine mud (41.4 Ma ∼39.8 Ma, Es3M), and lastly to less thicker larger-scale mixed sand-mud fan deltas (39.8 Ma ∼38.2 Ma, Es3U). The types of slope system, sediment supply and lake-level change are three controlling factors for determining the source-to-sink architecture of the gravel-to mud-rich fan-deltas and sediment-dispersal characteristics. This study has demonstrated that the process-based modelling approach can be effectively used to simulate complex geological environments and quantify controlling factors.  相似文献   

20.
The Middle to Upper Jurassic Todagin assemblage in northwestern British Columbia, Canada, was deposited in the Bowser Basin above arc-related rocks of the Stikine terrane. Sedimentary structures indicate that a variety of gravity flow processes were involved in transport and deposition in deep-water slope environments. At Mount Dilworth, laterally continuous and channelized turbidites are interbedded with and overlain by mass-transport deposits in which sedimentary clasts are supported in a mudstone matrix. More than 50% of the succession consists of mass-transport deposits, indicating significant slope instability. A 300 m thick mass-transport complex exposed near the top of the succession is interpreted to result from tectonic activity, which triggered a major change in sediment supply from a local source area. At Todagin Mountain, a channel complex displays three successive channel-fills with associated overbank sedimentation units. Mass-transport deposits are rare, and confined to channel axes. Channels 1 and 2 are characterized by 40-50 m thick, ungraded pebble clast-supported conglomerate while the uppermost Channel 3 contains graded beds and occasional traction structures. The gradual change from erosive and amalgamated channel deposits at the base, to more aggradational channels at the top, is related to elevation of the equilibrium profile. Creation of accommodation favored aggradation on the mud-dominated slope succession and construction of well-developed channel-levee systems. The vertical succession exposed at Todagin Mountain is consistent with normal progradation of the slope under high sedimentation rates. In the Mount Dilworth area, extensional faulting associated with development of the restricted Eskay rift in the early Middle Jurassic produced a dissected basement above which the Todagin assemblage was deposited. These structures were inverted during collision of the Stikine and Cache Creek terranes, and likely played a major role in the stratigraphic evolution of the deep-water architectures.  相似文献   

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