南海北部陆坡白云深水区深水沉积结构要素

在回顾深水沉积结构要素研究的基础上,结合白云深水区的勘探实践,对白云深水区深水沉积的结构要素进行了研究。将白云深水区深水沉积划分为4种结构要素,分别为水道、天然堤-溢岸沉积、席状砂和块体搬运沉积。水道是白云深水区深水沉积的主要组成部分,也是重要的储层;水道按成因可分为侵蚀型、侵蚀/加积型和加积型;水道充填沉积物的岩性变化较大,有砾岩、砂岩、泥岩以及几种岩性的混合。天然堤-溢岸沉积主要以泥岩、粉砂岩为主,平面上,天然堤-溢岸沉积与水道走向平行,横向上远离水道扩散,侧向连续性好但垂向连续性差。席状砂位于水道末端,具有朵叶状外形,分为层状和合并状2种类型：层状席状砂具有相对低的砂岩体积分数,泥岩和砂岩互层;而合并状席状砂岩体积分数高,砂层和砂层接触,夹有少量的泥。块体搬运沉积包括滑塌、滑块、块体流、碎屑流、坡身失稳复合体、块体搬运复合体等;块体搬运沉积常直接位于层序界面上,对下伏地层侵蚀明显,分布广泛,可作为良好的油气封盖层。     

浅水三角洲基本特征、形成条件及沉积模式：以渤海新近系为例

渤海海域新近系浅水三角洲是渤海重要的勘探开发储层类型,沉积于湖盆浪基面以上的滨浅湖中,以分流河道砂岩和水下分流河道砂岩为骨架砂体,前缘席状砂分布广泛,前三角洲沉积以浅湖相为主,垂向沉积层序不连续,不具有典型的吉尔伯特型三层式沉积结构为显著特征。浅水三角洲形成于稳定的坳陷湖盆环境,沉积物供给相对平衡的半干旱—半湿润的气候环境下。依据河口分流作用演化的不同,水体极浅时,三角洲进积易形成分流河道向湖泊的长驱直入,形成枝状的分流河道型浅水三角洲,分流河道和天然堤极为发育;水体相对较深时,分流河道会在河道分支处堆积河口坝或分流沙坝,并由水下分流河道砂体连接形成朵状前缘砂体,分流砂坝极为发育,河口坝外缘的席状化沉积物,包括天然堤、决口扇、溢岸不连续砂等都可成为连通储层。在连片的分流砂坝型三角洲,砂体连通性好、分布面积较大,多形成构造油气藏,包括断层油气藏和背斜油气藏;分流河道型三角洲由于砂体多孤立状,分布面积小、连通性差,易于发育岩性油气藏。

     

重力流沉积砂岩的成因、改造及油气勘探意义

在前人研究基础上,结合最新研究成果,以深水砂岩形成为线索,讨论重力流沉积砂岩成因机制以及后期底流改造作用,分析争议问题,探讨解决方法,并揭示油气勘探意义。重力流沉积砂岩成因机制复杂,将浊流严格定义为紊流支撑,悬浮沉降的重力流,有利于砂岩成因机制解释及砂体分布预测。具有正粒序构造的砂岩为浊流成因,块状砂岩和逆粒序砂岩为砂质碎屑流成因。浊流砂岩沉积在平面上向四周散开,形成朵叶状砂体,碎屑流砂岩沉积沿流体搬运方向展布,形成舌状砂体。重力流沉积受后期底流改造而形成含牵引流构造的砂岩,但牵引流构造不是底流改造砂体所特有的标志,需结合砂体分布特征及沉积环境加以鉴别。水道内重力流沉积受底流影响,天然堤不对称发育,水道发生单向迁移,砂体平面展布范围变大,但砂体垂向厚度变小。同时,受底流改造的天然堤之间会形成局部负向地形,为后期水道、朵体有利沉积场所,易形成连续垂向叠置砂体。深水砂岩预测需将重力流沉积和底流改造结合起来。     

广东三水盆地第四纪网状河沉积特征

珠江三角洲西北部的三水盆地范围内发育典型的网状河体系。它们具有重复分叉合并、坡降低以及河道深且窄的特点，并且发育天然堤、河间湖泊和洼地等地貌单元。钻井资料显示，网状河的沉积记录以泛滥平原地区沉积的悬浮负载的细粒沉积物为主，由砂砾和砂组成的河道沉积物分布比较局限，呈较窄的带状，被包裹在细粒的泛滥平原积物之中。主干河道表现出较高侧向稳定性垂向继承性，形成了较厚的砂体。较小的分叉河道则容易发生决口改道，沉积了较薄的砂体。河间湖泊沉积主要为含植物碎片的灰黑色粉砂质淤泥，沼泽中植物遗体的堆积形成了泥炭层。晚更新世以来的构造沉降、全球海平面上升以及河流搬运物质的快速加积是珠江三角洲平原地区形成网状河体系的主要原因.     

大庆油田葡一油层组高精度层序格架内储集砂体的沉积构成及其对油田开发的意义

大庆油田北三区上白垩统葡一油层组以高频湖进面可划分为3个四级和8个五级的高精度层序地层单元。以密集开发井资料为基础追踪这些层序单元可为储层砂体研究提供精细的等时对比框架。该油层组的主要储集砂体多为复合型砂体,由各种单一砂体相互叠置和切割所形成,包括下切河道（谷）分流河道复合砂体、水下分流河道上叠水上分流河道复合砂体、分流河道上叠河口坝砂体、决口水道上叠决口三角洲砂体等复合类型。这些砂体的内部沉积构成复杂,控制着厚油层储层物性的非均质性变化。在高精度层序框架内可划分出3个砂体复合带,其沉积构成的差异对剩余油的分布具有重要影响。主河道复合砂体带的孔渗性和连通性好,易形成上部层内和隔层非均质性剩余油;河道边部-河口坝复合砂岩带结构复杂,隔层发育,易形成平面未波及或物性变化导致的剩余油,应是区内剩余油挖潜的重要相带;边缘砂坝-决口扇-越岸泛滥砂泥岩互层带砂体分布局限,孔渗性和连通性差,由于井网控制不够或连通性差形成剩余油。     

陆相湖盆深水重力流沉积特征、砂体结构研究及油气勘探意义—以鄂尔多斯盆地上三叠统长7油层组为例

结合深水重力流沉积理论、野外剖面、岩心、测井等资料的分析,对鄂尔多斯盆地合水地区延长组长7油层组重力流沉积相和砂体结构的类型、特征进行了深入分析。研究表明长7沉积期发育大面积的深水砂岩,主要发育砂质碎屑流、浊流等重力流砂体,砂质碎屑流沉积以块状层理为主,单砂体厚度大,浊流沉积以粒序层理为主,砂泥互层频繁;结合重力流沉积背景下各成因砂体测井曲线形态、垂向发育厚度、垂向连续性及组合特征,将砂体垂向叠置结构划分为多期砂叠置厚层型、厚砂-薄泥互层型、厚砂-薄砂-泥互层型及薄砂-厚泥互层型四种类型,并对研究区单井砂体结构进行了聚类。实践表明,砂质碎屑流沉积区虽是油气藏有利聚集分布带,但分布面积较广,结合砂体结构特征,可进一步细化有利区划分,为致密油藏有利区的优选提供了新的研究思路。     

鄂尔多斯盆地三水河剖面上三叠统块状砂岩的异重流成因——来自岩石结构的证据

由于储层质量好、非均质性弱、成藏条件优越,深水沉积中的块状砂岩常常成为油气勘探开发的重要目标。相对具有各种交错层理等沉积构造的其他砂岩而言,块状砂岩的成因判识难度更大。因此,对块状砂岩成因机制的研究,直接影响了其沉积过程的认识,制约了其沉积模式、储层预测地质模型的重建。针对鄂尔多斯盆地南部旬邑县三水河剖面中发育的晚三叠世中层—巨厚层块状砂岩,利用高密度岩石样品的岩石薄片和激光粒度分析,对块状砂岩的粒度组成、粒度参数及其垂向变化特征进行研究。结果表明: 1）块状砂岩为长石岩屑质极细砂—细砂岩,内部偶含漂浮状灰黑色、红褐色泥砾,底部发育球枕、沟模等沉积构造;2）块状砂岩之间及其与交错层理砂岩层之间夹薄层—极薄层灰黑色泥岩、油页岩,二者间突变接触常见;3）岩石薄片中碎屑颗粒分选差,呈棱角—次棱角状,成分及结构成熟度中等偏低;4）粒度组成上,跳跃组分与悬浮组分各占50%左右,显示底床载荷与悬浮载荷同时存在且贡献相当;5）其偏度与浊流沉积相似,但其分选略差于浊流沉积,与三角洲沉积相差更远;6）垂向上,块状砂岩内部存在多期分米级复合韵律,厚度范围为10~30 cm。综合研究区地质背景、沉积构造、微观显微结构、粒度组成及其搬运过程、沉积分异解释结果,认为该剖面块状砂岩为洪水成因的异重流沉积。该研究丰富了对深水块状砂岩成因的理解,深化了异重流沉积块状砂岩结构特征的认识,同时也为异重流沉积的判识提供了依据。     

湖相深水块状砂岩特征、成因及发育模式——以南堡凹陷东营组为例

块状砂岩因其厚度大、储层物性较好而成为深水沉积油气勘探开发中最重要的目标。沉积构造相对简单,但变化迅速且组构特征多变。为了探索不同块状砂岩的成因及其联系,建立预测性地质模型,首先将南堡凹陷东营组深水块状砂岩分为2类8种岩相和10种岩相组合,其中单期砂层顶部常含漂浮状砾石,形态多变、内外源均有。本区块状砂岩成分成熟度差,结构成熟度不稳定,粒度累积概率曲线反映了3种搬运过程:多流体改造型、三角洲前缘继承型和混杂快速冻结型。成因分析认为,块状砂岩以砂质碎屑流搬运为主,真正碎屑流和颗粒流次之,并见部分砂质滑塌成因;常与浊流、泥流、泥质滑塌沉积伴生,发育5种相序组合,其中砂质碎屑流-浊流、砂质碎屑流-泥流组合最常见。高密度流体内沉积物浓度分层与特殊的流速剖面共同控制下塑性层流与牛顿紊流间的界面控制了漂浮状砾石搬运和沉积。最后,建立了陡坡带外源型、陡坡带内源型和缓坡地内源型深水沉积过程及块状砂岩发育模式,为断陷盆地深水沉积砂岩储层的预测提供了新思路。     

渤海湾盆地A油田新近系明下段沉积特征及演化模式

渤海湾盆地A油田新近系明下段Ⅱ—Ⅴ油组是其主力含油层位。通过观察分析岩心资料的沉积构造特征、岩矿特征和粒度特征、测井形态、地球物理属性等特征,综合判定其主要发育曲流河和浅水三角洲两种沉积相类型,油田范围内曲流河主要发育河道、决口扇、天然堤和泛滥平原4种沉积微相,浅水三角洲主要发育水下分支河道、水下天然堤、河口坝和分流间湾4种沉积微相。通过分析沉积相特征,结合高分辨率层序地层学观点,对A油田明下Ⅱ—Ⅴ油组的垂向演化特征进行了探讨,结果表明:处于长周期上升半旋回的Ⅴ油组曲流河呈条带状分布;处于长周期下降半旋回初期的Ⅳ油组浅水三角洲平面呈坨状,内部砂体连通性差;处于长周期下降半旋回中期的Ⅲ油组浅水三角洲平面呈朵叶状,砂体以侧向叠置为主;处于长周期下降半旋回晚期的Ⅱ油组浅水三角洲平面呈鸟足状,砂体以垂向叠置为主。最终提出该油田沉积演化模式。     

鄂尔多斯盆地陇东地区长7段沟道型重力流沉积特征研究

致密砂岩目前已成为中国油气勘探开发的重点领域。本文通过野外剖面及岩心观察、测井资料和深水重力流沉积理论对就鄂尔多斯盆地陇东地区长7段重力流沉积特征进行了系统研究,结果表明该区发育砂质碎屑流沉积、浊流沉积及滑塌沉积3种成因类型的重力流沉积砂体。砂质碎屑流沉积由灰色、褐灰色细砂岩构成,厚度均在0.5m以上,多数大于1m,块状层理发育,具有近源分布特征;浊流沉积由灰色、深灰色粉砂岩、泥质粉砂岩构成,单层厚数度从几厘米到十几厘米,具有完整或不完整的鲍马序列,呈远源分布特征;滑塌沉积在研究区发育较少。研究区长7段重力流沉积砂体横向连通性较差,纵向连通性较好,具有带状展布的特征,为沟道型(非扇型)重力流沉积体系。     

琼东南盆地中央峡谷深水天然堤—溢岸沉积

中央峡谷位于琼东南盆地深水区,发育面积较广,内部天然堤—溢岸沉积发育。深水天然堤—溢岸可作为良好的油气储集体,深受油气工业界的关注。为了指导中央峡谷的油气勘探,利用三维地震资料,结合地震剖面以及均方根振幅属性对中央峡谷内部天然堤—溢岸沉积的形态和控制因素进行了分析,总结了天然堤—溢岸的沉积模式,并对其油气勘探前景进行了...     

东非鲁伍马盆地深水X气藏海底扇储层构型研究:重力流—底流交互作用的指示意义*

底流在陆缘深水环境下广泛存在,可对深水沉积过程及砂体分布产生重要影响。前人对重力流与底流的交互作用机制及沉积产物开展了大量研究,但目前有关底流改造型的海底扇储层构型模式仍然研究不够深入。东非鲁伍马盆地是当前重力流—底流交互作用研究的热点地区,文中以其代表性的下始新统海底扇水道体系为例,综合岩心、测井及三维地震资料开展储层构型精细表征,建立重力流—底流交互作用下的海底扇水道体系构型模式。研究表明,目标水道体系内部发育水道、溢岸及朵叶3种构型要素,其中水道可分为水道复合体、单一水道及其内部不同级次的构型单元。底流对细粒物质的搬运可形成非对称的溢岸沉积,导致水道复合体之间呈逆底流侧向迁移叠置样式,其间泥岩隔层容易保存; 单一水道之间呈顺水道纵向迁移或逆底流侧向迁移样式,其中纵向迁移部位水道切叠连通,而侧向迁移部位容易保存泥质侧向隔挡体。受重力流沉积演化的影响,单一水道内部充填由砂泥交互型逐渐演化为富砂型,且在水道弯曲段的轴部砂体最为发育。     

Deep-water fan-channel conglomerates of Late Cretaceous age, southern Chile

The exceptionally well exposed Lago Sofia conglomerate and sandstone lenses in the Upper Cretaceous Cerro Toro Formation of southern Chile are interpreted as the channel and channel margin facies of a deep-sea fan. The north-to-south oriented channels formed on an elongate fan in a narrow retroarc basin between a rising cordillera to the west and the South American craton to the east. The great length of some of the channels (> 120 km) seems to reflect the long duration (> 30 m.y.) and stable nature of the basin. Enclosing the lenses is the fine-grained Cerro Toro Formation which represents overbank turbidite flows and hemipelagic sedimentation on levee and levee flank areas. Foraminiferal assemblages suggest deposition in 1000-2000 m of water. Most of the conglomerate has features developed by tractive currents (parallel- and cross-stratified conglomerate). Most is moderately well sorted, imbricated, and has parallel to inclined stratification; large-scale dunes up to 4 m high are exposed. Typical sediment, gravity flow structures and bedding styles (e.g. pebbly mudstones, graded conglomerate, giant flutes) are not as common in the channel deposits as are tractive features. Tractive features in the gravels apparently were developed by rolling, sliding, and saltation as the bed-load component of highly turbulent, moderate- to low-density turbidity currents flowing in a confined channel. Graded-to-massive conglomerates appear to have been deposited rapidly from fully turbulent flows; diamictites were deposited from debris flows in which fluid viscosity, yield strength, and buoyancy of the fluid were dominant. The three major conglomerate classes recognized do not occur in a systematic manner; vertical and lateral heterogeneity is the rule.     

Fluvial channel and overbank deposits from the Westphalian of the Durham coalfield, NE England

The Westphalian (Upper Carboniferous) Coal Measures of the Durham coalfield in NE England were deposited in lower and upper delta plain environments. Distributary channels crossed the plain and were separated by shallow, interdistributary lakes and bays. Detailed observation of three-dimensional (3-D) opencast (surface) mine exposures, in collaboration with subsurface borehole analysis, has revealed the existence of five varieties of channel deposits and two associated overbank facies within the Durham Coal Measures. Major distributary channels were the major avenues of sediment transport across the Coal Measures plain, were variably sinuous, mostly 1–2 km wide and deposited elongate belts of sand mostly up to 5 km wide. Proximal, major crevasse splay channels formed by the breaching of major channel banks during flood events, were straight, sand-filled and up to 400 m wide. Minor distributary channels formed by the sustained operation of such crevasses, varied from straight to highly sinuous, and deposited ‘shoestring’ sand/mud belts up to a few hundred metres wide. Minor crevasse channels, generally straight and up to 50 m wide, were formed through bank breaching of minor, and in a few cases major, distributaries. Distal feeder channels formed down-palaeocurrent extensions of minor distributaries which supplied interdistributary minor delta subsystems, were generally straight and up to 200 m wide. Of the two types of channel overbank (levee) deposits recognized, one, comprising thinly interbedded fine-grained sandstone and siltstone/claystone, is mostly, though not exclusively, associated with major distributary channels. The other, consisting of ‘massive’ siltstones with regularly spaced, thin claystone bands, is uniquely developed at the margins of minor distributary channels. The lower part of the Westphalian A succession in the northern Pennines records a change in the depositional environment upwards from a lower to upper delta plain. Through this transition, major channel deposits show evidence of having evolved from being of dominantly low sinuosity to being more variable in morphology. Channel sedimentation was profoundly influenced by regular, possibly seasonal, variations in flow stage and sediment load.     

穆尼盆地第四纪深水弯曲水道:沉积构型、成因及沉积过程

深水水道是陆坡沉积的重要组成单元,深水水道储层受到广泛关注。基于高分辨率三维地震资料,利用地震属性、分频技术等研究穆尼盆地第四纪深水弯曲水道的沉积构型、成因及沉积过程,主要取得以下3个方面的成果:(1)建立了深水弯曲水道沉积构型模式。弯曲深水水道由水道和堤岸组成。堤岸脊将堤岸分成内堤岸和外堤岸两部分。水道由底部粗粒滞留沉积、深海泥质披覆沉积以及滑块组成。(2)深水水道早期为低弯曲水道,后期逐渐演化为高弯曲水道。(3)建立了深水弯曲水道沉积的岩相模式,深水弯曲水道由垂向加积水道和侧向迁移水道组成。顺重力流方向,侧向迁移带,内弯带以沉积作用为主,外弯带以侵蚀作用为主。垂向加积带,水道底部粗粒滞留沉积往往表现为垂向加积特征。深水弯曲水道岩相模式的建立对深水浊积水道储层准确预测具有重要的理论指导意义。     

Deep-sea avulsion and morphosedimentary evolution of the Rhône Fan Valley and Neofan during the Late Quaternary (north-western Mediterranean Sea)

The Petit-Rhône Fan Valley (north-western Mediterranean) is a broad, sinuous, filled valley that is deeply incised by a narrow, sinuous thalweg. The valley fill is differentiated into three seismic subunits on high-resolution seismic-reflection profiles. The lower chaotic subunit probably consists of channel lag deposits that seem to be in lateral continuity with high-amplitude reflections representing levee facies. The intermediate transparent subunit, which has an erosional base and clearly truncates levee deposits, is interpreted to be mass-flow deposits resulting from the disintegration of the fan-valley flanks. The upper bedded subunit shows an overall lens-shaped geometry and the seismic reflections onlap either onto the top of the underlying transparent subunit or onto the Rhône levees. Piston core data show that the upper few meters of this upper subunit consist of thin turbidites, probably deposited by overflow processes. The few available ¹⁴C ages suggest that the upper stratified subunit filled the Petit-Rhône Fan Valley between 21 and 11 kyr BP. The upper bedded subunit is deposited within the Petit-Rhône Fan Valley downslope of a major decrease in slope gradient. This upper subunit and the thalweg are genetically related and represent a small channel/levee system confined within the fan valley. Previous studies interpreted this thalweg to be an erosional feature resulting from a recent avulsion of the major channel course. Our interpretation implies that the thalweg is not a purely erosional feature but a depositional/erosional channel. This small channel/levee system is superimposed on a large muddy channel/levee system after the sediment supply changed from thick muddy flows during the main phase of aggradation of the Rhône Fan levees, to thin, mixed (sand and mud) flows at the end of Isotope Stage 2 (～16–18 ka BP). The pre-existing morphology of the Petit-Rhône Fan Valley played a determinant role in the sediment dispersal leading to the creation of this small and confined channel/levee system. These mixed flows have undergone flow stripping resulting from the changes in the slope gradient along the thalweg course. The finer sediment overflowed from the thalweg and were deposited in the Petit-Rhône Fan Valley. Coarser channelled sediment remaining in the thalweg were deposited as a ‘sandy’lobe (Neofan). As indicated by ¹⁴C dating, sedimentation on this lobe continued until very recently, suggesting a further evolution of the turbidity flows from small mixed flows to small sandy flows. the deposition of this study lobe and the sedimentary fill of the Petit-Rhône Fan Valley may be related to widespread shelf edge and canyon wall failures with a resulting downslope evolution of failed sediment into turbidity currents.     

西秦岭直合隆地区三叠系深水水道沉积模式分析

西秦岭三叠系地层主要由深水沉积物组成。选取西秦岭直合隆地区出露较好的三组剖面进行研究,按重力流类型及静水条件下所发生的沉积现象,总结出六种岩石相类型,即滑塌岩相（F1）、碎屑流相（F2）、超高密度流相（F3）、高密度浊流相（F4）、低密度浊流相（F5）、深海泥岩相（F6）。通过对三处剖面的横向追踪对比,结合不同沉积环境下表现出特定的岩石相占比及砂体堆叠样式,共识别出限制性水道、弱限制性水道及水道天然堤三类沉积单元。限制性水道中砂体叠置关系复杂,以超高密度流相占主导地位,次为碎屑流相;弱限制性水道中砂体叠置较规整,以超高密度流相占主导地位,次为低密度浊流相;而水道天然堤表现为砂泥互层（总厚度约15 m）,主要为低密度浊流相和深海泥岩相。最后建立了研究区内深水水道沉积演化阶段模式图——早期限制性环境下水道较顺直,水道较窄,砂体叠置关系复杂;中期限制性环境相对早期有所减弱,水道弯曲度增大,水道变宽,出现溢岸沉积,砂体叠置关系复杂;晚期为弱限制性环境,弯曲水道两侧发育天然堤,砂体叠置规整。本次研究利用野外露头建立的深水水道沉积演化模式,在一定程度上还原其相关的重力流演化过程及发育期次,对全球其他类似研究具有一定的参考意义。     

Submarine channel levee shape and sediment waves from physical experiments

Submarine channel levees aggrade through repeated overspill events from the channel axis. The shape of the levees may therefore reflect some characteristic(s) of the overspilling flow. It has been noted that basin floor levees typically have a relatively low-relief and taper exponentially to their termination; in contrast slope channel levees may be much steeper close to the channel. A simple physical experiment was performed where a surge-like sediment-laden current flowed through a curved channel. Significant overspill occurred and generated a deposit flanking the channel on either side. The experiment was repeated 25 times to build up low-relief channel-levees. It was found that in proximal areas, levees were steep and characterised by power-law decays, a transitional zone of logarithmically thinning levee was found a little further down-channel, followed by exponential decays in medial to distal areas. The style of levee decay is a function of spatial variation in overbank sedimentation rates. Where flows rapidly lose momentum and deposit across the grain-size spectrum, i.e., in proximal areas, levees tend to be steep; farther down the channel, the steep levee slope gives way to a more gradually tapering deposit. In more distal parts of the channel, deposition is directly related to sediment settling velocity (rather than the suspended load exceeding flow transport capacity as is the case in proximal areas), the deposit reflects this with relatively simple exponential thickness decays. Additionally, small-scale sediment waves developed under lee wave conditions on the inner-bend overbank. The waves initially migrated slightly towards the channel, but as the style of overspill evolved due to intra-channel deposition, flows moved out of the lee wave window and sedimentation became out of phase with the wavelength of the features and the topography was healed.