南海北部陆坡深水区沉积物输送模式探讨

南海北部陆坡深水区沉积物输送模式复杂多样,研究发现主要有碎屑流、浊流、砂质碎屑流、碳酸盐岩重力流、块体搬运、河流搬运、深水水道搬运7种类型,它们共同影响着南海北部陆坡沉积物类型和储层分布。其中(砂质)碎屑流沉积、块体搬运沉积、河流供给、深水水道砂是南海北部深水储层的主要成因,而纯粹的浊积岩在该地区发育不广泛。珠江口盆地的深水储层受到河流的供给和后期流体改造的影响,并且存在碳酸盐岩重力流沉积物薄层,证明该地区水动力条件较强;琼东南盆地深水储层分布受到了碎屑流控制和深水水道的影响,相对浅水区来看可能存在分选较好、干净的砂体储层,具有良好的勘探潜力。     

珠江口盆地深水区油气储层发育规律及勘探方向北大核心CSCD

珠江口盆地白云凹陷是我国深水油气勘探的重点区域,然而对其深水储层分布特征及规律并没有明确的认识。利用钻井、岩心以及地震资料,针对白云凹陷发育的三套重要的储层,从储层类型分析入手探讨了其时空展布规律,指明珠江口盆地深水区油气勘探方向。研究结果表明:珠江口盆地深水区主要发育深水扇、陆架边缘三角洲与东沙台缘斜坡扇砂体;在缓陆坡阶段,主要在陆架坡折带附近发育陆架边缘三角洲和深水扇储层,而在陡陆坡阶段深水储层主要发育在陆架坡折带的下方,为典型的深水扇砂体;珠江口盆地深水油气勘探目标主要为SQ23.8发育的陆架边缘三角洲、深水扇以及台缘斜坡扇砂体,SQ21时期水道、深水扇和陆架边缘三角洲砂体,SQ13.8发育的深水扇砂体、水道充填砂体。     

珠江口盆地深水区油气储层发育规律及勘探方向

珠江口盆地白云凹陷是我国深水油气勘探的重点区域,然而对其深水储层分布特征及规律并没有明确的认识。利用钻井、岩心以及地震资料,针对白云凹陷发育的三套重要的储层,从储层类型分析入手探讨了其时空展布规律,指明珠江口盆地深水区油气勘探方向。研究结果表明:珠江口盆地深水区主要发育深水扇、陆架边缘三角洲与东沙台缘斜坡扇砂体;在缓陆坡阶段,主要在陆架坡折带附近发育陆架边缘三角洲和深水扇储层,而在陡陆坡阶段深水储层主要发育在陆架坡折带的下方,为典型的深水扇砂体;珠江口盆地深水油气勘探目标主要为SQ23.8发育的陆架边缘三角洲、深水扇以及台缘斜坡扇砂体,SQ21时期水道、深水扇和陆架边缘三角洲砂体,SQ13.8发育的深水扇砂体、水道充填砂体。     

琼东南盆地海底地形地貌特征及其对深水沉积的控制

琼东南盆地位于南海北部大陆边缘西部,其深水区是重要的油气勘探新领域。利用琼东南盆地高密度的多道地震资料,阐明了琼东南盆地海底地形地貌特征,分析了盆地内深水沉积体的类型、特征、形成机制和空间展布,探讨了地形地貌对深水沉积的控制作用,对深入理解深水沉积过程,尤其是该区深水油气储层的预测具有重要意义。研究结果表明,琼东南盆地海底地形总体可以划分为陆架、陆坡和深海平原。在该地形地貌控制下,研究区内主要发育6种深水沉积体:浊流沉积、陆坡峡谷充填、滑塌沉积、滑移沉积、沉积物波和碎屑流沉积。进一步的研究表明,这些沉积体的空间发育部位和规模与陆坡的坡度有关。地形坡度通过控制重力流流体的流态产生各类型重力流沉积,进而控制了陆坡体系的调整过程。研究结果还表明,由于地形坡度的变化,重力流流态会发生相应变化,并进而导致各种类型重力流沉积在其形成过程中发生相互转化,其一般转化顺序通常为滑塌-碎屑流-浊流。     

墨西哥湾盆地新生代沉积特征分析

通过收集、整理国内外学者的研究成果,总结了墨西哥湾盆地新生代的沉积特征及其与油气成藏的关系。分析认为,由于受古新世和早始新世的拉腊米构造运动的影响,墨西哥湾盆地新生代沉积时大量陆源碎屑不断进入盆地,使其海岸线、陆架和陆架边缘在新生代期间不断向盆地方向迁移,最终在陆棚处沉积巨厚的河流—三角洲沉积物;沉积中心的迁移控制了该区油气田的分布,而三角洲相控制了新生界油气富集,另外深水河道砂体、浊积扇砂体等是油气富集的重要相带。     

陆架边缘三角洲沉积特征研究及其油气意义

陆架边缘三角洲自发现以来,因具有分布面积广、厚度大、储层发育等特点,在世界上已成为重要的油气勘探目标.结合国内外研究现状,通过研究国外典型陆架边缘三角洲和我国珠江口盆地珠海组陆架边缘三角洲的沉积特点,阐述了陆架边缘三角洲的识别特征,分析其对深水陆坡及海盆砂体沉积的控制作用并指出陆架边缘三角洲沉积对于深水油气勘探具有重大...     

东非鲁伍马盆地深水沉积体系及油气勘探意义

利用高分辨率三维地震资料、测井和钻井数据,对东非鲁伍马盆地深水沉积特征进行了系统刻画。根据深水沉积体的地震相特征,识别出峡谷、水道、漫溢沉积、朵体、块体搬运沉积(MTDs)和凝缩段等深水沉积单元,建立了地震识别图版。分析总结了水道和朵体的岩性特征、电性特征和储层物性特征,砂岩具有低伽马(GR)和高电阻(RT)特征,厚层砂岩GR曲线呈“箱型”,有泥岩夹层的砂岩段呈叠加的“钟型”特点;储层压实程度弱,发育原生粒间孔隙,具有中—高孔、中—高渗的特征。结合成藏条件研究,认为由水道和朵体浊积砂岩储层、凝缩段和漫溢沉积泥岩盖层、天然堤和MTDs为侧向遮挡等要素构成的油气储、盖配置关系,是研究区油气成藏的一个关键因素,对深水油气勘探具有一定的指导意义。     

西非塞拉利昂—利比里亚盆地深水岩性油气藏成藏特征

立足于大西洋的构造演化,划分了盆地构造演化阶段,明确了不同演化阶段的构造、沉积特征,分析了漂移期岩性油气藏的成藏特征,建立油气成藏模式,指出了油气勘探的方向。研究表明,塞拉利昂—利比里亚盆地经历了裂陷期和漂移期两个演化阶段,早白垩世裂陷期,构造活动强烈,以陆相沉积为主;晚白垩世至今的漂移期构造活动弱,以海相沉积为主。赛诺曼—土伦阶海相烃源岩是漂移期岩性油气藏的主要油气来源,是油气成藏的基础;盆地漂移期广泛发育大型深水沉积体,深水沉积体是漂移期储层和岩性圈闭形成的关键;油气运移控制了岩性油气藏的成藏模式,漂移期构造活动弱,缺少油源断裂,赛诺曼—土伦阶成熟烃源岩生成的油气就近运移至烃源岩层内的岩性圈闭中聚集成藏,形成自生自储的油气成藏模式;寻找赛诺曼—土伦阶烃源岩灶内大型沉积体是盆地未来深水区油气勘探的重要方向。     

东非坦桑尼亚盆地油气地质特征与勘探前景

近几年,东非海岸坦桑尼亚盆地发现了14个大中型气田,使得坦桑尼亚成为全球深水油气勘探的焦点。以收集到的盆地最新地质基础资料和油气田资料为依据,归纳总结该盆地构造沉积演化特征,分析烃源岩、储集层、盖层及含油气系统特征,预测其勘探前景。研究认为,盆地发育3套烃源岩,主力烃源岩为中上侏罗统页岩、下白垩统三角洲相页岩和上白垩统海相页岩。主要储层是下白垩统河流三角洲砂岩以及上白垩统、古新统和渐新统的深水水道砂岩。潜在储层包括卡鲁群河流三角洲砂岩、中侏罗统砂岩和灰岩。盆地内具有优良盖层质量的黏土岩层序出现在整个侏罗系—新近系地层,形成了区域和层间盖层。陆上及浅水区以构造成藏组合为主;深水区以重力流砂体在陆坡形成的构造—地层成藏组合为主。勘探的目标应着重于白垩纪以来重力流砂砾沉积物及河道充填沉积物形成的斜坡扇和海底扇。     

深水沉积储层地震精细描述技术研究及应用

沉积储层识别与精细描述是深水区油气藏勘探的重点及难点。针对深水沉积砂体内部储层横向变化快、纵向多期叠置切割、非均质性强等储层预测及评价难题,提出了利用地震甜点/梯度融合属性定性识别沉积体,高精度频谱成像精细雕刻沉积体内幕,多相约束随机地质建模实现储层精细描述的技术方案,实现了储层定性分析向半定量评价转变,解决了深水沉积体识别与储层精细评价难题,对加快复杂深水碎屑岩油气藏勘探步伐具有积极的推进作用。     

Seismic stratigraphy and hydrocarbon prospectivity of the Lower Cretaceous Knurr Sandstone lobes along the southern margin of Loppa High,Hammerfest Basin,Barents Sea

The Lower Cretaceous Knurr Sandstone deposited along the southern slope of Loppa High and overlain by the Kolje and Kolmule seals forms an attractive play in the Hammerfest Basin of the Barents Sea. Late Jurassic organic-rich Hekkingen shale directly underlies the Knurr Sandstone and acts as a source to provide effective charge. Three wells, 7120/2-2, 7122/2-1 and 7120/1-2, have proven the Knurr-Kolje play in structural traps, with an oil discovery in 7120/1-2. Prospectivity related to stratigraphic traps is, however, highly under-explored.In order to document and map the reservoir distribution and stratigraphic-trap fairway, the Lower Cretaceous sedimentary package containing the Knurr Sandstone is divided into a number of depositional sequences and systems tracts using key regional seismic profiles calibrated with logs. Mapping of the key surfaces bounding the Knurr sandstone has been carried out using all the seismic vintages available from Norwegian Petroleum Directorate (NPD).The thick massive nature of the sandstone (123 m in well 7122/2-1), sedimentary features characteristic of gravity flow deposits, high-resolution internal seismic reflections and stratal geometries (truncations and lapout patterns), and sequence stratigraphic position of the Knurr Sandstone on seismic profiles confirm that the lobes identified on the seismic section are gravity driven base of the slope lobes. These Knurr lobes and slope aprons were formed as a result of uplift of the Loppa paleo-high in the Late Jurassic to Early Cretaceous times which caused subaerial exposure and incision. The characteristic mounded, lobate geometry evident on the seismic can be mapped along the toe-of-slope and records multiple stacked lobes fed by multiple feeder canyons. Lateral partitioning and separation of the lobes along the toe-of-slope could potentially create stratigraphic traps. The existing 2D seismic coverage is, however, not sufficient to capture lateral stratigraphic heterogeneity to identify stratigraphic traps. 3D seismic coverage with optimum acquisition parameters (high spatial and vertical resolution, appropriate seismic frequency and fold, long offsets and original amplitudes preserved) can allow for the reconstruction of 3D geomorphologic elements to de-risk potential stratigraphic traps prior to exploratory drilling.     

鄂尔多斯盆地西南缘奥陶系深水牵引流沉积

深水牵引流沉积是沉积学中的一个重要研究领域，包括内潮汐、内波沉积和等深流沉积两大类，主要发育于海洋深水区。深水牵引流沉积的研究起步较晚，目前主要集中于现代深海沉积和野外露头研究，对深埋地下的古代深水牵引流沉积发现较少，其所具有的油气潜能还不被人们所认识。本文论述了鄂尔多斯盆地西南缘奥陶系内潮汐沉积、等深流沉积的特征和沉积类型。内潮汐沉积是在研究区首次发现，以灰色中一细砂岩为主，部分为粗粉砂岩，单层厚十余厘米至数十厘米，砂岩以普遍发育双向交错纹理为特征。等深岩丘主要由3种碳酸盐等深岩组成，即砂屑等深岩、粉屑等深岩和灰泥等深岩，共发育有4种层序样式。最后，阐明了其油气勘探意义，并分析了其潜在的油气勘探价值。     

Annot Sandstone in the Peïra Cava basin: An example of an asymmetric facies distribution in a confined turbidite system (SE France)

High-resolution physical stratigraphy and detailed facies analysis have been carried out in the foredeep turbidites of Annot Sandstone in the Peïra Cava basin (French Maritime Alps) in order to characterize the relationship between facies and basin morphology. Detailed correlation patterns are evidence of a distinction between a southern bypass-dominated region, coincident with a channel-lobe transition and a north-eastern depositional zone, represented by sheet-like basin plain. These depositional elements are characterized by three main groups of beds related to the downcurrent evolution of bipartite flows. These facies groups are: 1) pebbly coarse-grained massive sandstones with rip-up mudstone clasts and impact mudstone breccias (Type I and II beds) deposited by basal dense flows, 2) coarse-grained massive sandstone overlain by tractive structures (Type III and IV beds) indicating the bypass of overlying turbulent flows and 3) massive medium-grained and fine-grained laminated sandstones related to the deposition of high and low density turbidity currents (Type V and VI beds). Ponding and reflection processes, affecting the upper turbulent flows, can characterize all type beds, but especially the beds of the third group. As described in other confined basins of the northern Apennines (Italy), the lateral and vertical distribution of these type of beds, together with other important sedimentary characteristics, - such as the sandstone/mudstone ratio, bed thicknesses, amalgamation surfaces and paleocurrents - reveal that the deposition of the Annot Sandstone in the Peïra Cava basin was controlled by an asymmetric basin with a steep western margin. This margin favored, on the one hand, basal dense flow decelerations and impacts, as well as bypass and deflection of the upper turbulent flows towards the north east.     

Reconstructing large-scale remobilisation of deep-water deposits and its impact on sand-body architecture from cored wells: The Lower Cretaceous Britannia Sandstone Formation,UK North Sea

The Lower Cretaceous Britannia Sandstone Formation comprises deep-water sandstones deposited in the Witch Ground Graben, Outer Moray Firth, UK North Sea. The sandstones form a major gas condensate reservoir stratigraphically trapped against the Fladen Ground Spur. Although the first-order architecture is a simple northwards-thinning wedge, the lower part of the reservoir has a high degree of internal heterogeneity. The presence of thick debrites interleaved with or replacing sandstone units suggests that large-scale remobilisation has significantly impacted the sandstone distribution. This paper aims to reconstruct the style, geometry and history of the remobilisation over a 20 km², densely drilled area of the Britannia Field, focussing on the lower reservoir interval where remobilisation is thought to be prevalent. The study is based on documentation of approximately 2000 ft (610 m) of high quality core from 11 wells, together with wireline data from an additional 26 wells. Two main phases of remobilisation are recognised, each associated with excision surfaces removing up to 45 m of previously deposited stratigraphy. These surfaces are overlain by debrites that can be an order of magnitude thinner than the inferred excision depths, so that up to 40 m of differential topography was created as a consequence of the remobilisation. Subsequent sandstone intervals are shown to heal this differential topography, giving rise to a simple layer-like, large-scale architecture despite the complex internal remobilisation-induced heterogeneity. Remobilisation has thus affected the sand-body geometry both by removing previously deposited sand intervals and by controlling the thickness distribution of subsequent sandstones. Integration of the model with data from uncored wells shows that spatial variability may in some areas occur on distances smaller than current core-spacing (450 m), diminishing the geometric predictive value of the model in these areas. The fully mixed nature of the debrites is interpreted to indicate efficient transformation of the remobilised mass into a debris flow, controlling the highly evacuated morphology of the failure area. This link between morphology and process is used to characterise the Britannia remobilisation morphotype and place it into existing mass wasting classifications.     

Anatomy of a submarine channel–levee: An example from Upper Cretaceous slope sediments,Rosario Formation,Baja California,Mexico

To date, facies architecture models of submarine channel–levees have largely been derived from seismic data, isolated core data and limited field studies. We report field observations of an Upper Cretaceous submarine channel–levee complex within the Rosario Formation, Baja California, Mexico, which provide high-resolution data of lithofacies and ichnofacies distribution, and levee depositional thickness decay along transects perpendicular to the channel axis. Within the levee, both sandstone thickness and the overall proportion of sandstone decrease according to a power law away from the channel axis. Spatial variation in sedimentary structures away from the channel axis is predictable and provides an important link to the depositional flow regime. In channel-proximal locations, structureless sands, parallel lamination, overturned ripples, and ripple cross-lamination (including climbing ripple cross-lamination) are common; in channel-distal localities starved ripples are abundant. Sandstone bed thickness generally increases up stratigraphy within the levee succession, which is interpreted to indicate increasing turbidity current magnitude and/or contemporaneous channel floor aggradation reducing relative levee relief. However, in the most channel-proximal location sandstone bed thickness decreases with height; combined with evidence from both facies and palaeocurrent analysis this allows the position of the levee crest to be inferred. The thickest beds occur at higher levels with increasing distance from the channel axis, using this evidence we present a model for levee growth and migration of the crest.Quantitative analysis of ichnofacies distribution reveals that traces typical of the Cruziana and Skolithos ichnofacies are superimposed over the ‘normal’ background Nereites ichnofacies, forming a ‘bioturbation front’ which is indicative of proximity to the channel. By analogy with modern canyons and channels, the association of Cruziana and Skolithos ichnofacies with the channel may be attributed to oxygen and nutrient enrichment and possible turbidity current transport of organisms responsible for these ichnofacies.     

Facies-based rock properties characterization for CO2 sequestration: GSWA Harvey 1 well,Western Australia

GSWA Harvey 1 was drilled as part of the South West CO₂ Geosequestration Hub carbon capture and storage project (South West Hub) to evaluate storage volume, injectivity potential and carbon dioxide retention capacity in the south-western Perth Basin. Six cored intervals from the Triassic Lesueur Sandstone contain nine lithofacies consistent with fluvial depositional environments: the lower Wonnerup Member is dominated by fluvial lithofacies consisting of stacked beds of porous, permeable sandstone deposited as high-energy fill and barforms, with rare finer-grained swampy/overbank deposits. The overlying Yalgorup Member contains mainly floodplain palaeosols with low- to moderate-energy barforms. The high- to moderate-energy fluvial facies typically have a low gamma response and contain clean, medium to very coarse-grained quartz-dominated sandstones. Other clastic components include K-feldspar (8–25%) with trace muscovite, garnet and zircon, and interstitial diagenetic kaolinite (up to 15%) and Fe-rich chlorite (up to 13%). The low-energy facies contain variably interbedded mudstone and thin, moderate to well sorted fine-grained sandstone, typically with a high gamma response, and are consistent with deposition under swampy, overbank and palaeosol conditions. These facies have significantly higher proportions of mica and diagenetic clays, including smectite (up to 8%) and illite (up to 10%), and detrital plagioclase (up to 21%) and trace carbonate bioclasts. High porosity and permeability in the cored intervals of the Wonnerup Member indicate good reservoir characteristics in terms of storage capacity and injectivity at depths relevant to CO₂ injection (>1500 m). High porosity and extremely variable permeability values in the Yalgorup Member were measured. The variation is due to permeable vertical sandstone features in low permeability sandy mudstone and indicate limited sealing potential, although the spatial connectivity of the vertical features cannot be resolved from the available core. A preliminary assessment of the area as a CCS site seems favourable; however, the project is only in the early stages of its characterization and far more regional and site-specific data are needed to evaluate how injected CO₂ may behave in the subsurface.     

Development and flow structures of sand injectites: The Hind Sandstone Member injectite complex,Carboniferous, UK

The Hind Sandstone Member of the Carboniferous Craven Basin occurs within a thick succession of marine mudstone and is here interpreted as a sandstone injectite complex. Injectites take the form of (i) sills; (ii) upwards emplaced dykes; (iii) downwards emplaced dykes; (iv) a sedimentary laccolith; and (v) sandstone bodies remobilised in-situ. The remobilised and injected sand originated from small turbidite scour fills and potentially a more significant sand body such as a submarine slope gully fill. The sedimentary laccolith appears to jack-up the units it injects, and is filled by sandstone with a chaotic fabric suggestive of brecciation of partly cemented sand. The laccolith and sill-dominated nature are suggestive of relatively shallow remobilisation. Sills are commonly laterally gradational with upwards emplaced dykes, and in some cases these feed apparently downwards emplaced dykes. A series of flow structures are preserved within some of the injectites, and these provide clues to the emplacement history. Crack propagation direction is inferred from the orientation of undulating crests developed on the upper and lower surfaces of injectites. Peak-flow is indicated by scour marks, resembling flute and tool marks, which are superimposed onto these undulating surfaces. Internal flow structures highlighted by pyrite mineralistion record the waning stage of injection. The observed flow structures suggest that the apparent crack propagation direction was generally oblique to the peak flow, and nearly perpendicular to the direction of late-stage fluidised sediment flow. Crack propagation relates to the local stress field, whilst injection flow may be related to the local pore pressure distribution. Recognition of this suite of structures may provide a useful interpretational tool for other injectites in both core and outcrop. Pore fluid overpressure which drove injection developed through the migration of petroleum and mineralising fluids from the underlying Bowland Shales and older limestones. A complex brecciated fracture network within the mudstones underlying the injectites records fluid migration pathways. Sliced blocks and thin sections from injectites reveal flow structures defined by iron pyrite mineralisation. The trigger is here related to growth of compressional structures and associated syn-sedimentary slumps which occur at the same stratigraphic level as the injectites.     

Upper Jurassic stratigraphy and sedimentary facies in the Central Outer Moray Firth Basin,North Sea

The Upper Jurassic of the Outer Moray Firth Basin can be divided into two main stratigraphic units — the Piper and Kimmeridge Clay Formations. In each of these formations five major sedimentary facies can be recognized. The Piper Formation, of late Oxfordian to early Kimmeridgian age, comprises very fine to coarse-grained sandstones and minor mudstone of clastic shelf to shoreline origin. Large scale upward-coarsening sequences are well developed in some areas, particularly in the reservoir sands of the Tartan oilfield, and are interpreted as regressive, possibly deltaic deposits. The unconformably overlying Kimmeridge Clay Formation ranges in age from late Oxfordian through Volgian to Ryazanian. The formation is predominantly argillaceous, but also contains locally thick accumulations of sandstone deposited by gravity flow processes. The Claymore Sandstone Member is proposed as a new name for these sandstones in the region of the Claymore oilfield, where they form the major reservoir. Sands of the Piper Formation were derived mainly from the south-west, although some input from the north may also have occurred. Deposition may have extended further eastwards than the present erosional limit of the sands. Thick sand sequences in the Kimmeridge Clay Formation are probably restricted to the margins of the Witch Ground Graben, where contemporaneous faulting occurred.     

A Lagrangian study of the near-surface intrusion of Pacific water into the South China Sea

Satellite-tracked Lagrangian drifters are used to investigate the transport pathways of near-surface water around the Luzon Strait. Particular attention is paid to the intrusion of Pacific water into the South China Sea(SCS).Results from drifter observations suggest that except for the Kuroshio water, other Pacific water that carried by zonal jets, Ekman currents or eddies, can also intrude into the SCS. Motivated by this origin problem of the intrusion water, numerous simulated trajectories are constructed by altimeter-based velocities. Quantitative estimates from simulated trajectories suggest that the contribution of other Pacific water to the total intrusion flux in the Luzon Strait is approximately 13% on average, much smaller than that of Kuroshio water. Even so, over multiple years and many individual intrusion events, the contribution from other Pacific water is quite considerable. The interannual signal in the intrusion flux of these Pacific water might be closely related to variations in a wintertime westward current and eddy activities east of the Luzon Strait. We also found that Ekman drift could significantly contribute to the intrusion of Pacific water and could affect the spreading of intrusion water in the SCS. A case study of an eddy-related intrusion is presented to show the detailed processes of the intrusion of Pacific water and the eddy-Kuroshio interaction.