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1.
【目的】转换陆缘虽然发现时间相对较晚，但近年却获得重大油气勘探发现；其海底扇沉积特征和沉积模式是当前深水油气勘探研究的热点。【方法】以赤道大西洋漂移晚期转换陆缘为例，利用PaleoScan全三维智能解释手段和三色（RGB）混相分频技术，揭示了转换陆缘海底扇的沉积特征与沉积模式。【结果】漂移晚期陆缘上发育的海底扇主要由深水水道和末端朵叶两个亚相单元构成。在剖面上，深水水道连续无间断发育，呈多期叠置状；在平面上，单期水道—朵叶复合体规模相对较小，且无溢岸和决口沉积伴生，在远物源一端，多期水道—朵叶复合体则汇聚叠置成裙边状。【结论】海底扇的剖面沉积特征是转换陆缘“较小陆架宽度（平均为43 km）”的沉积响应。窄陆架使得陆源沉积物在基准面变化的任何时刻均可被搬运分散到深水陆坡，导致形成的多期水道复合体在剖面上连续叠置。海底扇的平面沉积特征是转换陆缘“窄（平均为23 km）陡（平均为5.4°）陆坡地貌”的沉积响应。窄陡陆坡孕育“流速大—侵蚀能力强”的重力流，其所形成的水道不易发生溢岸和决口现象，从而使得单期水道—朵叶复合体的平面规模相对较小；此外，由于陆坡外缘海山或转换脊的存在，其阻挡了重力流进... 相似文献
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《地质科技情报》2017,(3)
深水海底扇是深水油气勘探的重要目标,尼日尔三角洲盆地深水区海底扇具备良好的油气成藏条件,深入分析其沉积体系是预测有利储集体发育区带的关键。根据岩心观察、测井解释及地震资料等,对研究区深水海底扇的沉积特征进行了研究。结果表明:重力流沉积是研究区深水海底扇主要沉积物类型,但牵引流沉积也大量存在;研究区主要发育水道和朵叶体2种亚相,空间上可分为限制、半限制及非限制3个沉积区域;高弯度的曲流水道是深水海底扇半限制沉积区域的重要特征,水道的弯度指数分布在1.16~2.85之间,其与水道宽度呈正相关关系;水道向非限制沉积区逐渐演变为席状展布、多层叠置的复杂朵叶体沉积。综合分析表明水道和朵叶体均是有利储层发育的重要位置,古地貌是控制海底扇展布的重要因素。 相似文献
3.
深水扇储层的沉积特征是油气勘探开发中的一个热点问题。通过分析珠江口盆地白云凹陷荔湾3-1地区珠江组深水扇的沉积特征,明确了研究区具备深水扇形成的有利条件,受白云凹陷总体构造沉积背景影响,形成了富砂型的深水扇。本区深水扇是多种流体动力学机制共同作用的结果,碎屑流、浊流及底流相互作用与复合,形成了平面上具水道复合朵体的分布特征。在建立深水扇沉积模式的基础上,提出了水道加朵体型深水扇沉积微相划分方案,研究区储层以重力流水道、天然堤及滑塌朵体为主;而水道逐渐由相对近源的宽浅下切型变为远离物源的窄深型,其深度与天然堤宽度呈正比。 相似文献
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《地质科技情报》2017,(5)
深水沉积砂岩储层是近年来全球油气勘探重点领域之一,对于深水沉积模式认识、沉积类型划分、储层分布规律及宏观演化规律能否实现系统深入的认知也成为制约全球油气勘探获得更多突破的关键问题之一。以典型深水沉积广泛发育的西非被动大陆边缘尼日尔三角洲盆地和刚果扇盆地为研究区,以地震资料为主,钻井资料为辅,开展针对性的深水沉积体系层序界面识别,明确研究区层序及体系域划分方案,建立深水沉积层序地层格架;综合2个研究区的深水沉积特征,探索建立了一套西非地区的深水沉积类型的划分方案,将其划分为陆坡峡谷、块体流、水道体、朵叶体、半深海泥5种亚相;将块体流细化为滑移体和滑塌碎屑流2种微相,将水道体进一步划分为高侵蚀充填型水道、低侵蚀过路加积型水道、过路高弯度水道、废弃水道、堤岸-漫溢5种微相,将朵叶体细分为末端朵叶和决口扇朵叶2种微相;同时系统总结解剖了各微相的岩性组合、地震反射及平面发育特征;深入分析了研究区深水沉积体系的宏观演化特征及展布规律,认识到尼日尔三角洲盆地深水沉积体系中水道体和朵叶体均有发育,自下向上,随着相对海平面先下降再上升的过程,早期主要发育朵叶体沉积,晚期则转变为以发育大型浊积水道为主。刚果扇盆地深水沉积则主要为水道体沉积,朵叶体较少发育,早期水道规模小,中期开始发育多支复合水道并呈退积趋势,水道发育程度逐渐降低,至晚期水道能量及侵蚀能力复又转强,甚至形成较大的陆坡峡谷及多支水道体。 相似文献
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珠江口盆地深水扇的发现为中国油气勘探中的重大突破,并以其宏大的规模、典型的结构及巨大的勘探前景引起国内外的关注。在区域地质背景研究基础上,通过白云凹陷X-1气田岩石学特征、地球化学特征和地球物理特征研究,识别出该盆地内深水扇沉积体,将深水扇划分为内扇、中扇和外扇三个亚相和水道颗粒流、碎屑流、水道间、近源和远源浊流等微相。对各微相作了较为详细的描述,结果表明水道砂质碎屑流微相是最有利于优质储集砂体发育的沉积微相。在此基础上提出深水扇理想沉积模式。 相似文献
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近年来,深水油气勘探发现的储量在全球新增储量中的占比逐年增加,2010年以来其占比已超过50%,深水已经成为未来油气勘探的重点领域。作为深水油气勘探主要储层之一的深水水道,同样成为深水油气勘探的重点研究对象。以高分辨率（40 Hz）三维地震资料为基础,对研究区内的加积型水道—天然堤复合体进行了精细刻画,着重刻画了水道—天然堤复合体内部不同期次水道的中心线,重点分析了深水水道的发育和演化特征。该水道天然堤复合体整体宽25～30 km,单期水道宽度约300 m,推测厚度约10 m。深水水道的演化整体表现为有序的发育过程,初期水道较顺直,弯曲度较低,后期弯曲度逐渐升高,晚期水道的平面形态较为稳定,变化较小。深水水道在演化过程中不仅向左右两侧迁移,同时也具有向下游方向迁移的特征;前人认为深水水道向下游迁移的现象非常罕见,但是研究表明在某些情况下,这种现象可能并不罕见。 相似文献
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以高精度三维地震资料为基础,结合深水水道成因机制和水道截面形态特征,将下刚果盆地A区块中新统深水水道分为侵蚀型、侵蚀加积型和加积型三类,并进一步细分为九种亚类。该分类体现了A区块深水水道从近源至远源方向的横向展布特征。从近源至远源,流体动力条件逐渐减弱,水道形态演化过程为限制性-非限制性-限制性-前端朵叶,水道宽深比和弯曲度均逐渐变大。通过对每个三级层序均方根振幅属性图的分析,并结合海平面升降和构造抬升作用,可见刚果扇不断由南向北迁移及向盆地方向进积,层序自下而上并由南向北,整体由加积水道和远端朵叶沉积向侵蚀加积水道和侵蚀水道沉积转变。 相似文献
8.
利用高分辨率三维地震资料分析了孟加拉扇上扇某区块的深水沉积体特征。发现了六种典型地震相:下切充填相、海鸥翼状相、楔形发散相、透明相、强振幅平行相和弱振幅平行相。下切充填相代表粗粒的水道充填沉积;海鸥翼状相代表水道-天然堤复合体;楔形发散相代表细粒的天然堤沉积;透明相代表块体搬运沉积;强振幅平行相代表朵叶体沉积;弱振幅平行相代表深海披覆沉积。通过对典型地震剖面特征和平面属性分布分析可知:上扇垂向上依次沉积了朵叶体、水道和堤岸、朵叶体、水道-天然堤复合体。 相似文献
9.
利用多个地震数据体的地震反射特征,分析了孟加拉湾若开盆地深水沉积体系的不同沉积结构单元类型(峡谷、水道及水道复合体、天然堤—漫溢沉积、朵体以及块体搬运沉积)的典型地震响应特征、及其发育的位置,构建了研究区陆架—陆坡—盆底的沉积结构单元演化模式。研究表明,一个深水沉积体系垂向上自下而上的组合样式为:底部块体搬运沉积及厚层大规模朵体沉积,上覆水道复合体沉积,之后为水道—天然堤复合体沉积、以及一些小规模朵体沉积,顶部为薄层深海泥岩沉积。横向上自陆架向深海盆地的发育模式表现为:陆架/上陆坡峡谷—上陆坡侵蚀型水道—下陆坡侵蚀沉积型水道—沉积型水道—盆地朵体。 相似文献
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Well-exposed, vertically dipping, glacially polished outcrops of the Neoproterozoic Windermere Supergroup in the southern Canadian Cordillera include basin-floor deposits of the Upper Kaza Group overlain by slope channel complexes of the Isaac Formation. Within the 2·5 km thick Kaza and Isaac succession is an up to 360 m thick interval composed of diverse deep-water stratal elements including scour and interscour deposits, distributary channels, fine-grained turbidites, terminal splays, mass-transport deposits, erosional and levéed channels and avulsion splays, which collectively were formed during the development of an ancient passive-margin channel-lobe system. The proportion and vertical and lateral arrangement of stratal elements reveal three distinct complexes. The lower complex, consisting mostly of distributary channels and small and large scours, is interpreted to represent the detachment of lobes from an upflow levéed channel, wherein a well-developed channel-lobe transition zone was formed by efficient, siliciclastic flows during a period of sustained transport bypass and limited deposition coincident with the onset of falling relative sea level. The middle, comparatively thicker and more sandstone-rich complex, comprises distributary channel fills, fine-grained turbidites and lesser terminal splays that are interspersed with small scours, capped by a slope levéed channel filled with coarser-grained siliciclastic sediment. The abundance of basin-floor elements suggests negligible separation between the levéed channel and lobe, and therefore a poorly-developed channel-lobe transition zone, resulting from inefficient, siliciclastic-rich depositional flows that became dominant during lowstand and/or ensuing transgression. The stratal makeup of the upper complex resembles the lower detached complex, suggesting a return to efficient flows, and an abrupt change to mixed carbonate–siliciclastic sediments associated with highstand conditions. Accordingly, the stratigraphic architecture and stacking pattern of the Kaza–Isaac interval, which relate to the formation of multiple channel-lobe transition zones, were controlled by temporal changes in sediment supply and flow characteristics during the long-term progradation of the Laurentian continental margin. 相似文献
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松辽盆地中央坳陷南部下白垩统泉头组四段沉积相 总被引：7，自引：0，他引：7
松辽盆地中央坳陷南部下白垩统泉头组四段沉积时期，松辽盆地地形平缓，基底沉降缓慢，在湖平面整体扩张及浅水背景下河流入湖成三角洲沉积。通过岩心观察、相标志与测井相研究，该区储层主要为岩屑长石砂岩和长石岩屑砂岩，识别出三角洲平原、三角洲前缘、前角洲3种亚相，以及分支河道、天然堤、决口扇、分支河道间湾、水下分支河道、水下决口扇、河口坝、远沙坝、水下分支河道间湾9种微相三角洲平原、三角洲前缘广泛发育，前三角洲不发育。三角洲平原分支河道通过填积和频繁的分叉改道，向湖盆中心方向长距离推进，在三角前缘的浅水区域发育了大量水下分支河道，分支河道与水下分支河道砂体相互切割、叠加，形成了平均宽度200~600 m、平均厚度3~8 m的道单砂体，（水下）分支河道砂体构成了油气富集的主要储集体。该区沉积相的精细研究，为进一步调整开发井网奠定了基础。 相似文献
14.
A miniature, 9 m-wide floodplain, developed along a gravel-washing effluent stream, shows features such as levées, crevasse splays and floodbasins which compare with their larger-scale counterparts. For sediments deposited overbank, median size decreases exponentially with distance from the channel whilst sorting increases, with coarser sediment on the outside of a meander bend. Overbank flows are only a few grain diameters in depth near the channel. This study shows potentially useful systematic relationships in floodplain sediment textures, but it involves only one of a possible variety of floodplain types dominated by overbank sedimentation. This suggests that further exploration of overbank depositional processes is desirable as an aid to field interpretation. 相似文献
15.
Modern fluvial meander plains exhibit complex planform transformations in response to meander‐bend expansion, downstream migration and rotation. These transformations exert a fundamental control on lithology and reservoir properties, yet their stratigraphic record has been poorly evaluated in ancient examples due to the lack of extensive three‐dimensional exposures. Here, a unique exhumed meander plain exposed to the north of Scarborough (Yorkshire, UK) is analysed in terms of architecture and morphodynamics, with the aim of developing a comprehensive model of facies distribution. The studied outcrop comprises tidal platforms and adjacent cliffs, where the depositional architecture of un‐tilted deposits was assessed on planform and vertical sections, respectively. In its broader perspective, this study demonstrates the potential of architectural mapping of extensive planform exposures for the reconstruction of ancient fluvial morphodynamics. The studied exhumed meander plain is part of the Scalby Formation of the Ravenscar Group, and originally drained small coastal incised valleys within the Jurassic Cleveland Basin. The meander plain is subdivided into two storeys that contain in‐channel and overbank architectural elements. In‐channel elements comprise expansional and downstream‐migrating point bars, point‐bar tails and channel fills. Overbank elements comprise crevasse complexes, levées, floodplain fines and lake fills. The evolution of the point bars played a significant role in dictating preserved facies distributions, with high flood‐stage nucleation and accretion of meander scrolls later reworked during waning flood‐stages. At a larger scale, meander belt morphodynamics were also a function of valley confinement and contrasts in substrate erodibility. Progressive valley infilling decreased the valley confinement, promoting the upward transition from prevalently downstream migrating to expansional meander belts, a transition associated with enhanced preservation of overbank elements. Strikingly similar relations between valley confinement, meander‐bend transformations and overbank preservation are observed in small modern meandering streams such as the Beaver River of the Canadian prairies and the Powder River of Montana (USA). 相似文献
16.
根据密井网测井、录井以及其它分析化验资料,结合区域地质背景,对松辽盆地杏树岗油田杏三区东部白垩系姚家组一段葡萄花Ⅰ组油层1-3小层(葡Ⅰ1-3小层)沉积微相类型、特征、组合模式和不同地质时期沉积微相平面展布特征及其演化规律进行系统的研究。结果表明,葡Ⅰ1-3小层为浅水湖泊三角洲沉积,主要发育三角洲分流平原和三角洲内前缘2种沉积亚相,含11种沉积微相,具有不同的沉积特征和测井相模式;利用自然电位曲线幅变值和砂体厚度,有效识别天然堤、水上决口沉积、溢岸薄层砂3种有成因联系、测井曲线形态类似的沉积微相;进一步根据各沉积微相的测井曲线形态组合、沉积成因及沉积作用的不同,总结出7种沉积微相组合模式。葡Ⅰ1-3小层沉积演化经历了早期湖退、中期稳定、晚期湖侵3个阶段,不同时期的沉积特征、沉积微相展布各异,总体表现出湖盆发育规模由大变小,再变大,骨架砂体厚度和理想钻遇率逐渐减小的特点。 相似文献
17.
Crevasse splays from the rapidly aggrading, sand-bed, braided Niobrara River, Nebraska: effect of base-level rise 总被引：2，自引：0，他引：2
Base-level rise of ≈2·35 m on the Niobrara River has resulted in aggradation of the channel belt and a recent avulsion. Overbank areas have become flooded by rising groundwaters, and more than eight crevasse splays have formed between 1993 and 1997. Two crevasse splays, situated on the west and east sides of the Niobrara, have been studied using ground-penetrating radar (GPR), shallow boreholes and topographic surveys. The vibracores and GPR profiles provide a nearly three-dimensional view of the architecture of crevasse splay deposits. The east splay was initiated in the winter of 1993/94 and has expanded to cover an area ≈200 m by 1000 m, with sediment up to 2·5 m thick. The west splay, which was initiated by the opening of a crevasse channel through a levee in the autumn of 1995, covers an area ≈150 m by 250 m, with up to 1·2 m of sand deposited in a single year. The Niobrara splays are sand dominated and characterized by bedload deposition within channels, 5–30 m wide and 0·5–2 m deep, with the development of slipfaces where splays prograde into standing bodies of water. Sedimentary structures in cores include horizontal lamination, ripple lamination and sets of cross-stratification. There is a slight tendency for splays to coarsen up, but individual beds within the splays often fine up. The abundance of crevasse splays on the Niobrara River contrasts with other braided river floodplains. In the Niobrara, crevasse splay formation followed aggradation within the channel belt, which occurred in response to base-level rise. The link between crevasse splays, channel aggradation and base-level rise has important implications for the interpretation of ancient braided river and floodplain sequences. It is suggested that crevasse splay deposits should be an important component of aggrading fluvial sediments and, hence, should be preserved within the rock record. In this case, the aggradation and crevassing have been tied to a rise in base-level elevation, and it is suggested that similar deposits should be preserved where braided rivers are affected by base-level rise, for instance during transgression and filling of palaeovalleys. 相似文献
18.
The passive margin Texas Gulf of Mexico Coastal Plain consists of coalescing late Pleistocene to Holocene alluvial–deltaic plains constructed by a series of medium to large fluvial systems. Alluvial–deltaic plains consist of the Pleistocene Beaumont Formation, and post-Beaumont coastal plain incised valleys. A variety of mapping, outcrop, core, and geochronological data from the extrabasinal Colorado River and the basin-fringe Trinity River show that Beaumont and post-Beaumont strata consist of a series of coastal plain incised valley fills that represent 100 kyr climatic and glacio-eustatic cycles.
Valley fills contain a complex alluvial architecture. Falling stage to lowstand systems tracts consist of multiple laterally amalgamated sandy channelbelts that reflect deposition within a valley that was incised below highstand alluvial plains, and extended across a subaerially-exposed shelf. The lower boundary to falling stage and lowstand units comprises a composite valley fill unconformity that is time-transgressive in both cross- and down-valley directions. Coastal plain incised valleys began to fill with transgression and highstand, and landward translation of the shoreline: paleosols that define the top of falling stage and lowstand channelbelts were progressively onlapped and buried by heterolithic sandy channelbelt, sandy and silty crevasse channel and splay, and muddy floodbasin strata. Transgressive to highstand facies-scale architecture reflects changes through time in dominant styles of avulsion, and follows a predictable succession through different stages of valley filling. Complete valley filling promoted avulsion and the large-scale relocation of valley axes before the next sea-level fall, such that successive 100 kyr valley fills show a distributary pattern.
Basic elements within coastal plain valleys can be correlated with the record offshore, where cross-shelf valleys have been described from seismic data. Falling stage to lowstand channelbelts within coastal plain valleys were feeder systems for shelf-phase and shelf-margin deltas, respectively, and demonstrate that falling stage fluvial deposits are important valley fill components. Signatures of both upstream climate change vs. downstream sea-level controls are therefore interpreted to be present within incised valley fills. Signatures of climate change consist of the downstream continuity of major stratigraphic units and component facies, which extends from the mixed bedrock–alluvial valley of the eroding continental interior to the distal reaches, wherever that may be at the time. This continuity suggests the development of stratigraphic units and facies is strongly coupled to upstream controls on sediment supply and climate conditions within hinterland source regions. Signatures of sea-level change are critical as well: sea-level fall below the elevation of highstand depositional shoreline breaks results in channel incision and extension across the newly emergent shelf, which in turn results in partitioning of the 100 kyr coastal plain valleys. Moreover, deposits and key surfaces can be traced from continental interiors to the coastal plain, but there are downstream changes in geometric relations that correspond to the transition between the mixed bedrock–alluvial valley and the coastal plain incised valley. Channel incision and extension during sea-level fall and lowstand, with channel shortening and delta backstepping during transgression, controls the architecture of coastal plain and cross-shelf incised valley fills. 相似文献
19.
Interdistributary bay sequences and their genesis 总被引：3，自引：1，他引：3
T. ELLIOTT 《Sedimentology》1974,21(4):611-622
Interdistributary bay sedimentation is dominated by flood-generated incursions from the distributaries. There are three processes by which sediment-laden flood waters can be transferred to the bay: overbank flooding, crevassing and avulsion. These processes combine to produce a family of sedimentary sequences, the majority of which are small-scale coarsening upwards sequences representing infilling of the bay. Subordinate related sequences include those of small-scale (crevasse) channels and larger scale (distributary) channels. Spits or beaches at the mouth of open interdistributary bays produce larger scale, wave-dominated coarsening upwards sequences. A model of bay sedimentation concerning a recently initiated (hypothetical) distributary is presented. Four phases of sedimentation (overbank flooding, crevasse splay, minor mouth bar—crevasse channel couplets and avulsion) characterize the history of the distributary, and it is postulated that the phases are genetically related to alluvial ridge development. 相似文献
20.
利用实地考察、浅钻孔、探槽及卫星影像等方法,对鄱阳湖信江决口三角洲进行了系统研究。该决口三角洲是洪水冲破信江西岸天然堤流入附近的河漫湖泊形成的,其平面形态为鸟足状,总体延伸方向与主河道近垂直。在横切剖面上整个决口三角洲沉积体呈透镜状覆盖在早期的湿地或河漫湖泊沉积之上。鄱阳湖信江决口三角洲可分为3个亚相:决口三角洲平原、决口三角洲前缘和决口前三角洲。决口三角洲平原主要发育决口河道、决口天然堤、废弃决口河道和湿地,其中决口河道又可以进一步划分为决口水道、边滩、汊口滩;决口三角洲前缘主要发育河口坝、支流间湾。河漫湖泊规模小、深度浅、波浪能量弱,对河口坝和决口河道砂体的改造较弱,不易形成连片分布的席状砂;决口前三角洲不发育。决口三角洲沉积受河流作用和河漫湖泊作用的共同控制,其演化可以划分为主河道天然堤生长阶段、决口初期阶段、进积分汊阶段及分汊—废弃阶段4个阶段。 相似文献