泥质重力流沉积研究进展及其页岩油气地质意义
——以东营凹陷古近系沙河街组三段为例

2017-08-08 03:00宋明水向奎张宇蔡攀刘建磊杨仁超
沉积学报 2017年4期
关键词:东营细粒碎屑

宋明水,向奎,张宇,蔡攀,刘建磊,杨仁超

1.中国石化胜利油田勘探管理中心,山东东营 257017 2.山东科技大学地球科学与工程学院,山东青岛 266590

泥质重力流沉积研究进展及其页岩油气地质意义
——以东营凹陷古近系沙河街组三段为例

宋明水1,向奎1,张宇1,蔡攀1,刘建磊1,杨仁超2

1.中国石化胜利油田勘探管理中心,山东东营 257017 2.山东科技大学地球科学与工程学院,山东青岛 266590

页岩油气的勘探开发推动了泥页岩沉积机理研究的快速发展,使得细粒物质的搬运和沉积成为当今沉积学界和油气工业界共同关注的焦点。尽管海洋环境下的泥质重力流沉积研究成果频见报道,但有关我国新生代湖泊环境中的泥质重力流沉积尚未引起沉积学界的关注。故本文在国内外相关文献调研基础上,以岩芯观察和薄片鉴定为重点,分析了渤海湾盆地东营凹陷古近系沙河街组三段湖相泥质重力流沉积特征;探讨了湖相泥质重力流沉积的形成机制;以期为湖泊沉积学研究和陆相页岩油气开发提供参考。研究发现,东营凹陷古近系沙河街组三段发育泥质块体流、泥质碎屑流、泥质浊流及泥质异重流等多种重力流沉积类型;泥质滑塌岩、泥质碎屑岩、泥质浊积岩和泥质异重岩在时空上可以共生共存。认为泥质沉积物可以在动荡水体和较强水动力条件下沉淀;泥质重力流沉积在深水沉积区占有重要地位;泥质重力流对于泥页岩中的粗粒碎屑物质、有机质的搬运和沉积以及有机质的埋藏起到重要作用,因而具有重要的非常规油气地质意义。

重力流沉积细粒物质;泥质碎屑岩;泥质浊积岩;泥质异重岩;非常规油气;东营凹陷;古近系

随着页岩油气开发的热忱不断高涨[1-2],细粒物质沉积学逐渐成为当今沉积学研究的前沿领域和非常规油气工业界的关注焦点[3-7]。大型沉积盆地中的泥岩、页岩、油页岩等细粒沉积岩规模巨大,不仅可作为常规油气的烃源岩,而且细粒沉积岩具有巨大的页岩油气、油页岩等非常规油气资源潜力[8-9]。细粒沉积岩中发育多种重力流沉积,但长期以来的研究多聚焦于致密砂岩储层[10-12];有关细粒沉积岩的研究刚刚起步,泥、页岩中的重力流事件沉积研究尤为薄弱,针对我国中、新生代陆相湖盆细粒沉积岩中的重力流沉积事件研究,必将随着非常规油气开发和细粒物质沉积学研究的深入受到更多的关注。本文在国内外文献调研的基础上,以渤海湾盆地东营凹陷古近系沙河街组三段湖相细粒沉积体系为例,探索了湖相泥质重力流沉积的形成机制,以期为湖相泥页岩沉积学研究和非常规油气勘探提供理论参考。

1 研究进展与趋势分析

1.1 细粒沉积物搬运—沉积机理

细粒沉积物是指粒径小于62 μm的黏土级和粉砂级物质,其成分主要包含黏土矿物、粉砂、碳酸盐、有机质等[3,13-14]。细粒沉积岩分布广泛,约占沉积岩的三分之二[3,15]。然而,细粒物质的沉积、成岩过程极其复杂,是当今沉积学界研究相对薄弱的领域[13]。

1.1.1 泥质沉积物可在动荡水体环境中搬运和沉积

传统观点认为泥质只能在静水环境中垂向沉降,但这种认识早已被突破[3,16-20]。现代研究表明,大多数直径小于10 μm的黏土颗粒以絮凝物形式沉积,絮凝过程有助于大量泥质沉积物在海洋环境中的长距离搬运[21-22];而直径大于10 μm的黏土颗粒则主要以单颗粒形式沉降[23]。貌似单调的纹层或块状泥岩实际上是以集合颗粒的形式在动荡环境中被搬运和沉积而成[4,17,19]。现代河口的测量表明,大量的大直径絮凝物(一般0.2~0.7 mm,或>1 mm)迅速出现在最大流速之后,且能稳定存在于高速流体之中[24];一些泥岩含有大量黏土矿物集合颗粒,其粒径变化从黏土级、粉砂级至粗砂级[4,25-26];水槽实验也表明,弱固结的泥(含水约85%)可以被侵蚀成为扁平的泥砾[26];在相当于搬运细砂的流速条件下,泥质集合颗粒可以形成交错层理[27]。

上述研究均表明泥质沉积物可在动荡环境下以集合颗粒的形式被搬运和沉积,这一新认识对于细粒沉积研究有重要的推动作用。但细粒物质沉积动力学过程复杂,目前还没有较为理想的沉积模式[1]。随着研究的不断深入,更多的沉积环境因素将被引入到相关研究领域;研究范畴将拓展为海洋与陆相环境兼顾、现代沉积与地史记录并重的格局。

1.1.2 搬运—沉积细粒物质的流体类型

泥质浊流观点早在1978年被Piper提出[28],他将鲍马序列的E段划分为递变纹层段、无纹层递变段及块状段,并建立了泥质浊积岩模式;其主要特征为粒度递变、底部突变或与浊积砂岩渐变。其后的学者开展了广泛的研究,例如:南盘江印支期前陆盆地中发现的泥质浊积岩[29]、东营凹陷古近纪湖泊沉积中交错层理泥岩及块状浊积泥岩[13]、南海珠江口盆地细粒物质组成的低密度浊流沉积[30]以及北亚平宁前陆盆地晚渐新世源自远端细粒浊流沉积泥岩[31]。可见浊流在海洋、湖泊环境中均可作为搬运—沉积细粒物质的主要营力。

Kirbyetal.[32]将细粒沉积物质浓度大于10 g/L的水下底流定义为泥质流(fluid mud),其内部含有黏土粒级、粉砂粒级的颗粒及一定量的有机质;文献[18,33]提出了近滨、潮汐和浪控背景下的泥质流沉积的鉴定标志。而在许多陆架环境中受重力驱动的薄层坡移泥浆流(slurry flow)中,泥质被风暴浪产生的紊流支撑,而非自悬浮[34-37];这里的泥浆流是指浊流和碎屑流之间的过渡流体,其沉积物含有10%~35%的泥质杂基,且为颗粒支撑[38]。

现已知的将泥质搬运至盆地的流体还有异轻流(hypopycnal flow)、异重流(hyperpycnal flow)、风暴激发的弛缓流(storm-setup relaxation flows)以及重力驱动液化泥流(gravity-driven fluidized muds),但风或潮汐诱发的底流循环可能是更大范围陆表海泥质的搬运营力[39]。尽管针对泥质沉积流体的研究取得诸多进展,但理解泥质沉积物的搬运仍存在较大难度[4]。

上述流体的定义和内涵之间存在划分标准不一、交叉重叠等不足。国外的研究主要针对现代海洋沉积,而目前我国陆相湖盆细粒沉积体系的研究仍较薄弱,但也不乏针对这一问题的深入思考和有益探索[13,40-41]。针对我国广泛发育的中、新生代陆相沉积盆地,急需剖析典型细粒沉积岩组构特征,揭示陆相湖盆细粒物质的沉积机理、分布规律与主控因素,建立湖盆细粒沉积体系成因模式,从而推动湖泊沉积学研究和陆相致密油、页岩油气的发展。

1.2 水下沉积物重力流研究新进展

1.2.1 泥质重力流沉积

细粒沉积物是深水重力流的重要组分,暨重力是细粒物质远距离搬运的主要营力。滑坡坝的破裂、三角洲前缘斜坡失稳以及源自三角洲的沉积物重力流在水下分流河道和侵蚀沟谷充填方面扮演着重要角色[42]。细粒沉积物波可在受限的峡谷—水道环境中形成[6],而且在水道维持方面起重要作用[43]。富泥的沉积层特征主要取决于滑坡的规模和位置、分流河口的位置、盆地地形以及沉积速率[42]。因此,富泥的重力流将影响湖相浊积水道和朵叶体的建造和改造。

近年来,在陆架泥岩中识别了波浪增强沉积物重力流(wave-enhanced sediment gravity flow)沉积及其明显的“波状—纹层—均质层”三层结构[4,22],表明泥岩也可发育波状层理。由于粒度小、观察难度大以及受实验条件的限制,细粒物质的沉积作用仍是沉积学研究的薄弱领域[13],鉴别泥岩微构造(microstructure)仍存在较大难度[4],对深海盆地—平原的水道—朵叶体详细的内部结构仍知之甚少[7]。

尽管现代陆棚上广泛发育的泥质重力流沉积已有诸多报道[4,25-26,44-45],但地史中泥质重力流沉积的研究范例并不多,中、新生代湖相三角洲至深湖背景下的泥质重力流沉积研究尤为薄弱。对于泥质岩、粉砂岩等细粒沉积岩的微构造研究,需要开展毫米级、亚毫米级等细小尺度的观测和精细描述;并在此基础上,应用当代细粒沉积学新理论、新技术对其加以合理解释、分类及成因研究。

1.2.2 异重流沉积研究新进展

异重流作为一种将大量细粒沉积物搬运至深水盆地的作用机制,近年来引起了广泛关注[37,46-52]。异重流是洪水期河流注入较小密度的水体底部而形成的沿盆地底部流动的浊流[53-56]。异重流的发生主要受控于构造和气候[57-58],因无需大量沉积物的积累和触发机制,异重流的发生频率比碎屑流和浊流更高[59-62],故地史中的异重岩将比此前预测的多得多[4,63]。

异重岩的主要特征是逆粒序段—正粒序段成对出现,逆粒序—正粒序段的转换常表现为层内微侵蚀面,其顶、底接触关系以突变为主[53-55]。由于其巨大的悬浮载荷及其下潜、流动过程中存在着侵蚀作用,异重流可以保持悬浮载荷浓度并做长距离流动[64-65],因而,异重岩的分布可直达盆地中心深水区。例如,松辽盆地中心嫩江组具前积结构的富泥沉积被认为是高悬浮载荷河流入湖形成的泥质三角洲沉积[66],其作用机制应与异重流密切相关。

古近纪渤海湾断陷盆地构造极其活跃,断裂系统发育,坡降较大,气候湿润,物源区近,临近物源区洪水河口,半咸水湖盆湖水密度较低,这些地质背景特征均有利于异重流的发生,但异重流形成的细粒沉积并未引起足够的重视。随着细粒物质沉积学认知的进步和研究的深入,泥质异重岩必将受到沉积学家的密切关注。

1.2.3 水下沉积物重力流类型及其转化

尽管水下沉积物重力流研究已有许多经典之作,但对于重力流与其沉积特征之间的关系仍然知之甚少[56,58,67-69],在细粒沉积流体性质方面的认识尤其薄弱。当受地震、火山、风暴或河流洪水等激发,斜坡失稳并产生重力流,将形成滑塌岩、浊积岩和碎屑岩[61,69-70]。水下重力流之间的转化是普遍存在的[65],碎屑流与浊流可相互转化;异重流也可转化为碎屑流,或诱发斜坡失稳而产生碎屑流和浊流[71];非黏性的浊流能够影响黏性的软泥沉积底质,侵蚀产生泥质碎屑,进而形成泥质碎屑流[72]。因此,异重岩可与浊积岩、碎屑岩共存[12]。

重力流沉积类型多样,如何鉴别其类型,如何根据其类型及组合分析流体性质的转化成为重力流沉积学研究的关键。本文以渤海湾盆地东营凹陷沙三段为例,分别从地质背景、沉积物特征、成因机制及其非常规油气地质意义等方面展开讨论,力图为相关领域的研究提供参考。

2 地质背景

渤海湾盆地东营凹陷古近系沙河街组自下而上可分为沙四段、沙三段、沙二段、沙一段;其中沙三段是烃源岩和岩性圈闭最发育的层段。古近纪东营凹陷是一个大型的宽缓箕状凹陷[73],其东西长90 km,南北宽65 km ,面积约5 700 km2。研究区主要位于东营凹陷中—东部(图1)。在古近纪区域拉张的地质背景下,研究区内发育一系列NEE向正断层,断面整体向北倾斜,造就了北陡南缓的盆地地形特点,而这种古地貌特征控制了东营凹陷的沉积格局[74]。沙河街组主要发育湖泊、三角洲沉积体系,来自盆地东部的东营三角洲和永安三角洲分别自东部、北东部向湖盆中心进积[75];重力流沉积自三角洲前缘至湖盆中心均有发育[76]。

3 泥质重力流沉积特征描述及解释

3.1 泥质滑塌变形构造(泥质滑塌岩)

泥质沉积物滑塌变形构造在东营凹陷沙三段三角洲前缘—湖泊沉积中较为常见(图2)。包卷变形构造的物质成分以泥质沉积物为主,混有一定量的粉砂或细砂。不同成分、颜色的条带凸显了变形构造特征。深灰色泥岩与浅灰色的粉砂质泥岩呈现弯曲变形一致的条带状,变形层段厚度约12 cm(图2A);深灰色泥岩中包含浅灰色扭曲状粉砂质泥岩条带和团块,变形层段厚度约18 cm,而变形构造底部可见深灰色页岩水平层理,且未变形(图2B);或深灰色泥岩中局部发生变形,浅灰色条带宽度不一,部分为后期方解石充填,变形层段厚度约9 cm(图2C);深灰色泥岩发生弯曲变形,浅灰色细砂岩脉呈不规则状贯穿其中(图2D);灰色泥质粉砂岩夹弯曲状深灰色泥岩条带,厚度约6 cm,顶部纹层未变形(图2E);灰色粉砂质泥岩中部夹一层褐红色泥岩,呈现紧闭的平卧褶皱,厚度约3 cm(图2F)。

渤海湾盆地东营凹陷古近系沙河街组沙三段泥质岩变形构造特征是其成因分析的重要基础。滑塌变形构造系泥质沉积物在斜坡失稳的情况下[21,71],沿斜坡向下滑动,由于底部的摩擦大于中上部,滑塌体中上部在惯性作用下持续向前运动。由于在运动过程中,沉积物富含水、呈塑性状态,且层内连续性一般未被破坏。沉积体在发生滑动、滚动或变形过程中,砂质、粉砂质沉积物会被卷入、混合并发生变形。或者,块体在运动过程中,软沉积物受到扰动,孔隙水产生液化,形成砂岩脉等液化变形构造。在三角洲前缘地带,沉积速率一般较快,来自物源区的大量碎屑物质堆积于前三角洲和湖泊相泥岩之上,孔隙流体压力逐渐增大;使得三角洲前缘地带极易发生变形。其一,当富含孔隙水的泥岩难以承受上部沉积载荷时,超高孔隙压力会自发释放[60],引起三角洲前缘斜坡上的松散沉积物发生滑塌变形;其二,当受到地震、火山、洪水、风浪等外部作用叠加,也可诱发三角洲前缘斜坡失稳,产生滑塌变形。

图1 渤海湾盆地东营凹陷构造地质简图(据文献[76])Fig.1 Structural sketch map of Dongying sag in the Bohai Bay Basin (after reference[76])

图2 东营凹陷沙三段滑塌变形构造泥质岩A. 史122井,3 346.18 m;B. 史126井,3 387.76 m;C. 营691井,3 008.92 m;D.史134井,3 058.60 m;E. 营691井,2 856.7 m;F. 王541井,3 053.40 mFig.2 Slump deformations of mudstones in the Shahejie Formation Sha 3 member in the Dongying sag

3.2 泥质碎屑构造(泥质碎屑岩)

泥质碎屑构造是指泥质沉积物中含有大量先期沉积并经过再改造的沉积构造,岩石基质为泥质(或粉砂质泥),同时含大量泥质岩碎屑,岩石中的总泥质含量体积比≥50%。泥质碎屑结构与砂质碎屑岩的区别在于:前者泥质含量高(体积比≥50%),基质以泥质为主;后者泥质含量多低于岩石体积比30%,最多不超过岩石体积比50%,基质为砂质颗粒。它们的相同之处是都含有泥质碎屑。具有泥质碎屑构造的泥质沉积岩,称之泥质碎屑岩(狭义)。此处仅限于具有泥质碎屑结构的泥质沉积岩;含有一定泥质、以陆源砾石—砂级颗粒为主的粗碎屑岩不在此范畴。

深灰色泥质碎屑5~60 mm不等,呈现不规则碎片状杂乱分布于浅灰色粉砂质泥组成的基质之中,泥质碎屑可呈点或线状接触;泥质碎屑向上砾径变大,单层厚度大于20 cm(图3A)。或大量深灰色泥质碎屑以不规则状、撕裂状散布于浅灰色泥质粉砂基质之中,泥质粉砂沉积物可见液化变形特征,单层厚度大于10 cm(图3B)。此外,泥质沉积物液化变形构造常见。灰色泥岩中,贯穿不规则弯曲状砂岩和粉砂岩细脉(图3C);或灰色泥岩中分布大量的扭曲状粉砂岩条带,可见球枕构造(图3D),浅灰色粉砂质沉积物将泥质分割为不规则条带或碎片。

泥质碎屑构造的成因可以有两种解释:其一,泥质沉积物经滑塌、崩解和变形而形成泥质碎屑流,泥质碎屑流在盆地斜坡脚至盆地平原之间发生快速堆积而成;其二,由重力流侵蚀堤岸系统的泥岩(或具有较强黏结性的泥质沉积物)产生的泥质碎屑混入重力流沉积体系,形成泥质碎屑结构。在未固结成岩的泥质沉积物被继续搬运的过程中,变形构造常见。由于密度、含水饱和度和黏度的不同,不同成分的沉积物之间发生复杂的调整,导致岩石变形、崩解、混合,造成岩性的强非均质性[67]。泥质岩的液化变形构造可以发生于原地,也可以发生于块体搬运过程之中。砂质、粉砂质沉积物的液化变形与贯穿侵入可加剧泥质沉积物的碎片化过程和沉积物的混杂作用[77]。

3.3 泥质正粒序构造(泥质浊积岩)

东营凹陷沙三段泥质岩常见正粒序结构(图4),泥质岩下部颜色浅、与泥质粉砂岩呈渐变过渡;上部泥质较纯,泥岩颜色较深,反映粒度、泥质含量、有机质含量和沉积速率的逐渐变化。这种粒度的变化和沉积物组分的变化在显微镜下具有清晰的反映(图5A,B),下部粉砂质石英颗粒含量高,向上粒度变细,泥质、有机质含量逐渐增加。厚层的浊积泥岩的上部,可见火焰状构造;浊积泥岩厚度变化较大,从1 mm~3 cm不等(图4A)。正粒序泥岩多呈薄层状与浊积砂岩、粉砂岩共生,形成韵律互层结构,厚度介于1~5 mm之间(图4B)。或3 mm~ 1 cm厚的薄层浊积泥岩覆盖于明显的正粒序砂岩之上(图4C)。

浊积泥岩的快速堆积与欠压实脱水,在后期的砂质沉积物覆盖之后,由于二者的反密度梯度,极易发生软沉积物变形构造[69]。细粒沉积物在浊流中以悬浮方式被搬运,当流体紊流度降低时,悬浮沉积物依次沉降,故正粒序是浊积岩最显著的特征[61]。正粒序泥岩与浊积砂岩频繁共生,每一个细砂岩—粉砂岩—泥质岩的正粒序组合系同一次浊流事件的沉积产物,故与浊积砂岩伴生的泥质岩应归于浊积泥岩的范畴。

图3 东营凹陷沙三段泥质碎屑岩与液化变形构造A.史122井,3 402.8 m;B.史126井,3 323.16 m;C.营691井,2 684.12 m;D.史115井,3 036.61 m。Fig.3 Mudstone debrites and liquified deformation structures in the Shahejie Formation Sha 3 member in the Dongying sag

图4 东营凹陷沙三段泥质浊积岩A.史122井,3 422.08 m;B.王541井,3 051.10 m;C.王541井,3 057.50 m;DB.碎屑流砂岩;FS.火焰状构造;SSDS.软沉积物变形构造;TM.浊积泥岩;TS.浊积砂岩Fig.4 Mudstone turbidites in the Shahejie Formation Sha 3 member in the Dongying sag

图5 东营凹陷沙三段泥质浊积岩(A、B)、显微交错层理(C)与异重岩(D)A,B,C.牛页1井,3 409.05 m,A和C(单偏光),B(正交偏光);D.樊页1井,3 443.95 m(单偏光);OM.有机质;CL.黏土纹层;QZ.石英;CB.碳酸盐;CS.交错层理Fig.5 Mudstone turbidites, micro-cross beddings and hyperpycnites in the Shahejie Formation Sha 3 member in the Dongying sag

3.4 泥质韵律粒序构造(泥质异重岩)

渤海湾盆地东营凹陷沙三段泥质岩韵律纹层的常见,厚度多介于1~5 mm。显微镜下,泥质岩粒度的变化易于识别,在泥页岩中,可见泥质—有机质纹层与泥晶方解石纹层组成的显微交错层理(图5C)。粉砂质泥岩可见逆粒序—正粒序的成对出现,粒序纹层之间夹颜色较深的泥质—有机质纹层(图5D)。在每一个韵律层组合之间,泥质、有机质含量较高;在韵律层由逆粒序向正粒序转换之际,细粉砂等含量较高,且单颗粒直径达到该层粒径的最大。

泥页岩中微型交错层理的出现表明泥质等细粒沉积物不仅可以在低能环境下通过悬浮沉淀,也可以在较强的水动力条件下发生沉积。浊积岩常见正粒序,对于逆粒序的成因难以解释,尤其是逆粒序—正粒序的成对出现,可以用洪水异重流沉积机理来解释[51-55,78]。异重流是一种洪水河流输入型的稳定浊流,由于两种水体的密度差和沿斜坡向下的重力分量的作用,密度较大的洪水河流潜入汇水盆地水体底部,并沿盆地底部做长距离搬运悬浮沉积物的一种流体[51-52]。异重流的搬运机制主要依靠紊流的扬举力,从流体本质上讲,它与浊流是相同的,属于广义的浊流范畴[51-55]。泥质岩中的显微交错层理表明其沉积过程受动荡水体的控制;这种水体的动荡可能由浊流事件引起,也可能由季风引起的湖流产生。但作为事件沉积层,常被夹于正常泥页岩沉积层之中。

4 泥质重力流成因机制探讨

上述研究表明,东营凹陷沙三段泥质岩成因类型复杂,滑塌变形泥质岩、泥质碎屑岩、泥质浊积岩和泥质异重岩均有发育。在东营三角洲快速向湖盆进积的过程中,三角洲前缘砂质沉积物常常覆盖于前三角洲泥质沉积物之上,在同沉积作用阶段,泥质岩未经压实脱水;随着上覆沉积物厚度的不断增加,松软沉积物中的孔隙流体压力不断增加;加之上覆砂质沉积物密度大于下伏泥质沉积物密度,这种反密度梯度在重力作用下呈非均衡、非稳定状态;当孔隙压力积累到一定程度,超过沉积物的黏性阻力时,变形构造随之发生;或一旦有外部因素激发时,三角洲前缘的斜坡快速失稳[6,60],变形、滑塌、液化、崩解接踵而至。因此,变形构造泥岩、泥质碎屑岩、泥质浊积岩等重力流沉积可以呈现连续、渐变的空间接触关系。

泥质异重流、碎屑流与浊流存在复杂的共生共存关系。其一,碎屑流向浊流转化[24,65]:砂质碎屑流可以与水体混合、稀释,向浊流转化,这种转化一般发生于流体的中上部和尾部。其二,浊流向碎屑流转化[67]:随着悬浮沉积物的沉降,浊流底部悬浮沉积物浓度不断增加;且流体侵蚀底床或水下天然堤,堤岸物质可以重新进入水道系统,当浓度增大到一定程度,并含有一定泥质碎屑时,浊流转化为碎屑流。其三,异重流也可向砂质碎屑流转化,或诱发砂质碎屑流的产生[71]。前者的转化机制与上述浊流向碎屑流的转化机制相同。而洪水期的河流强烈的冲刷作用以及流体对底部沉积物施加的切应力,都是诱发三角洲前缘斜坡失稳滑塌的可能因素。因而,异重流也可诱发碎屑流及浊流的发生。在平水期或河流洪水中的悬浮沉积物浓度不足以产生异重流时,河流携带的沉积物在分流河口以河口坝或水下分流河道的形式就近沉积;当这种积累达到一定程度,并有外部因素激发时,滑塌—液化变形—碎屑流—浊流等依次产生。因此,碎屑岩、浊积岩与异重岩可以在一定时空范围内共生共存。

需要说明的是,作为重力流事件沉积细粒岩层,只是夹于正常(非事件沉积)泥页岩沉积层中的一部分,不能代表全部的泥页岩沉积,正常的泥页岩沉积层仍然占据相当的比重。实际工作中,根据沉积物结构、沉积构造特征,可加以区分(表1)。重力流沉积细粒岩与正常泥岩的区分也主要依据沉积物结构、沉积构造特征。正常沉积泥页岩一般具有均匀块状构造或水平纹层发育,且纹层内难以识别粒序、颜色变化。

但事件沉积与正常沉积泥页岩的区分目前只能在野外、岩芯、或在镜下识别;由于多数细粒沉积层薄、夹层多,许多薄层的厚度远低于测井数据采样间隔0.125 m,暨测井分辨率难以识别极薄层的泥质沉积;地震反射方面,更是无法达到极薄层的识别。

5 泥质重力流沉积的非常规油气地质意义

表1 泥质重力流沉积类型对比

湖相泥、页岩类型多样,沉积机理复杂。其中,陆源碎屑物质的输入占据重要地位,尤其是对泥、页岩储集性能和压裂密切相关的较粗粒脆性矿物的输入机制,重力流作为一种将沉积物向盆地中心深水区搬运的主要流体,对其重要性的认识有待于提高。在东营凹陷沙三段页岩油气储层中,重力流沉积层较为常见(图5A~D)。对于页岩油气而言,重力流沉积的地质意义主要集中于以下几个方面:

第一,重力流沉积泥质岩影响烃源岩的物质积累和保存。重力流将泥质、有机质等远距离搬运至盆地深水沉积区,促进有机质的富集和保存[20]。尤其是洪水输入型浊流——异重流常含有大量陆源有机物质,这些物质一方面为微生物提供了大量营养,或直接增加源岩的有机碳含量[59];另一方面,大量有机质及碎屑物质的输入会在一定程度上影响盆地的生态环境,进而影响微生物的繁衍和有机质的积累;此外,重力流事件向沉积盆地输入大量陆源物质,是一种重要的搬运—沉积机制;这种事件沉积会在较短的时间内加快深水区的沉积速率,从而有利于有机质的埋藏和保存。

第二,重力流沉积细粒岩是重要的页岩油气储层。对于非常规油气而言,重力流搬运—沉积的砂岩已成为深水致密砂岩油气藏的主要储集层;而重力流搬运—沉积而成的粉砂岩、泥页岩等是页岩油气的主要储集体。例如,在陆相湖泊背景下沉积的细粒沉积岩具有巨大的页岩气资源量[8-9]。东营凹陷沙河街组页岩油气储层中亦发现大量重力流成因的细粒沉积层(图5A~D)。碎屑颗粒之间的粒间孔、有机质粒内孔以及微裂缝等往往是页岩油气的主要储集空间,其中的较粗碎屑颗粒、有机质的搬运与重力流沉积作用密切相关。

第三,重力流搬运—沉积的碎屑颗粒影响水平井压裂工艺参数。在讨论泥页岩压裂力学性质之时,石英、长石、方解石等脆性矿物的含量是其中重要的评价指标。尽管泥质岩中存在成岩成因的粉砂级石英[79],但具有较好磨圆和分选的石英、长石等碎屑颗粒多数是由物源区经搬运—沉积而成。传统的认为泥质岩形成于静水低能环境絮凝沉淀的观点,难以解释泥质岩中存在的砂质、粉砂质沉积物;但对于重力流而言,可将大量较粗颗粒沉积物搬运至盆地中心深水沉积区。许多纹层状的泥页岩,其中相当一部分极有可能由重力流沉积而成。由于此前的常规油气储层研究主要关注砂、砾岩等粗碎屑沉积岩;对于非常规油气储集性能和压裂工艺参数评价至关重要的碎屑矿物来源及成因分析,需要加强沉积作用机理的研究。

6 结论

(1) 通过广泛的文献调研,认为泥、粉砂等细粒沉积物可以在动荡的高能水体环境中发生搬运—沉积;相关的实验、现代沉积观测和地史中的沉积记录研究均证明了这一点,并逐渐被国外的地质同行普遍接受;有关泥质沉积物只能在水动力条件极弱的静水环境中沉积的传统观点需要与时俱进。

(2) 泥、粉砂等细粒物质可以被重力流搬运至盆地中心深水沉积区,但由于沉积纹层一般较细,在以往的研究中往往不被重视。研究表明,深水沉积细粒岩中有相当一部分是重力流事件沉积层,需要沉积学家根据细粒沉积岩的结构、组分、微沉积构造等仔细加以甄别。

(3) 陆相湖盆中,来自三角洲前缘的细粒沉积物在重力作用下,发生滑动、滑塌、变形、崩解、稀释等作用,产生泥质滑塌岩、泥质碎屑岩、泥质浊积岩、泥质异重岩等重力流沉积细粒岩;多种重力流沉积细粒岩在时空上可以共生共存,垂向上反复叠置,横向上呈连续、渐变关系过渡。

(4) 重力流沉积细粒岩对于页岩油气在生烃物质聚集、储集空间形成和压裂工艺参数评价方面均可能产生重要影响,重力流沉积细粒岩具有重要的页岩油气地质意义。

致谢 胜利油田物探研究院陈杰、河口采油厂刘奎元、孙波和朱晓平等高级工程师在岩芯观察期间提供了大力帮助,审稿专家和编辑仔细审阅本文并提出宝贵建议,作者在此向他们致以崇高的敬意和衷心的感谢!

References)

[1] Law B E, Curtis J B. Introduction to unconventional petroleum systems[J]. AAPG Bulletin, 2002, 86(11): 1851-1852.

[2] Pollastro R M. Total petroleum system assessment of undiscovered resources in the giant Barnett Shale continuous (unconventional) gas accumulation, Fort Worth Basin, Texas[J]. AAPG Bulletin, 2007, 91(4): 551-578.

[3] Aplin A C, Macquaker J H S. Mudstone diversity: origin and implications for source, seal, and reservoir properties in petroleum systems[J]. AAPG Bulletin, 2011, 95(12): 2031-2059.

[4] Plint A G. Mud dispersal across a Cretaceous prodelta: storm-generated, wave-enhanced sediment gravity flows inferred from mudstone microtexture and microfacies[J]. Sedimentology, 2014, 61(3): 609-647.

[5] Hovikoski J, Lemiski R, Gingras M, et al. Ichnology and sedimentology of a mud-dominated deltaic coast: upper Cretaceous Alderson Member (Lea Park Fm), Western Canada[J]. Journal of Sedimentary Research, 2008, 78(12): 803-824.

[6] Kostic S. Upper flow regime bedforms on levees and continental slopes: turbidity current flow dynamics in response to fine-grained sediment waves[J]. Geosphere, 2014, 10(6): 1094-1103.

[7] Terlaky V, Rocheleau J, Arnott A W C. Stratal composition and stratigraphic organization of stratal elements in an ancient deep-marine basin-floor succession, Neoproterozoic Windermere Supergroup, British Columbia, Canada[J]. Sedimentology, 2016, 63(1): 136-175.

[8] 刘岩,周文,邓虎成,等. 鄂尔多斯盆地上三叠统延长组含气页岩地质特征及资源评价[J]. 天然气工业,2013,33(3):19-23. [Liu Yan, Zhou Wen, Deng Hucheng, et al. Geological characteristics of gas-bearing shales in the Yanchang Formation and its resource assessment in the Ordos Basin[J]. Natural Gas Industry, 2013, 33(3): 19-23.]

[9] 王永炜,高胜利,高潮. 鄂尔多斯盆地延长探区陆相页岩气勘探[J]. 地质科技情报,2014,33(6):88-98. [Wang Yongwei, Gao Shengli, Gao Chao. Continental shale gas exploration and discussion on issues related to geological theory in Yanchang exploration area, Ordos Basin[J]. Geological Science and Technology Information, 2014, 33(6): 88-98.]

[10] Zou Caineng, Wang Lan, Li Ying, et al. Deep-lacustrine transformation of sandy debrites into turbidites, Upper Triassic, Central China[J]. Sedimentary Geology, 2012, 265-266: 143-155.

[11] Yang Hua, Deng Xiuqin. Deposition of Yanchang Formation deep-water sandstone under the control of tectonic events in the Ordos Basin[J]. Petroleum Exploration and Development, 2013, 40(5): 549-557.

[12] Yang Renchao, He Zhiliang, Qiu Guiqiang, et al. A Late Triassic gravity flow depositional system in the southern Ordos Basin[J]. Petroleum Exploration and Development, 2014, 41(6): 724-733.

[13] 姜在兴,梁超,吴靖,等. 含油气细粒沉积岩研究的几个问题[J]. 石油学报,2013,34(6):1031-1039. [Jiang Zaixing, Liang Chao, Wu Jing, et al. Several issues in sedimentological studies on hydrocarbon-bearing fine-grained sedimentary rocks[J]. Acta Petrolei Sinica, 2013, 34(6): 1031-1039.]

[14] 柳波,吕延防,孟元林,等. 湖相纹层状细粒岩特征、成因模式及其页岩油意义——以三塘湖盆地马朗凹陷二叠系芦草沟组为例[J]. 石油勘探与开发,2015,42(5):598-607. [Liu Bo, Lv Yanfang, Meng Yuanlin, et al. Petrologic characteristics and genetic model of lacustrine lamellar fine-grained rock and its significance for shale oil exploration: a case study of Permian Lucaogou Formation in Malang sag, Santanghu Basin, NW China[J]. Petroleum Exploration and Development, 2015, 42(5): 598-607.]

[15] Macquaker J H S, Adams A E. Maximizing information from fine-grained sedimentary rocks: an inclusive nomenclature for mudstones[J]. Journal of Sedimentary Research, 2003, 73(5): 735-744.

[16] Schieber J. Evidence for episodic high-energy events and shallow-water deposition in the Chattanooga Shale, Devonian, central Tennessee, USA[J]. Sedimentary Geology, 1994, 93(3/4): 193-208.

[17] Macquaker J H S, Bohacs K M. On the accumulation of mud[J]. Science, 2007, 318(5857): 1734-1735.

[18] Ichaso A A, Dalrymple R W. Tide- and wave-generated fluid mud deposits in the Tilje Formation (Jurassic), offshore Norway[J]. Geology, 2009, 37(6): 539-542.

[19] Ghadeer S G, Macquaker J H S. Sediment transport processes in an ancient mud-dominated succession: a comparison of processes operating in marine offshore settings and anoxic basinal environments[J]. Journal of the Geological Society, 2011, 168(5): 1121-1132.

[20] Ghadeer S G, Macquaker J H S. The role of event beds in the preservation of organic carbon in fine-grained sediments: analyses of the sedimentological processes operating during deposition of the Whitby Mudstone Formation (Toarcian, Lower Jurassic) preserved in northeast England[J]. Marine and Petroleum Geology, 2012, 35(1): 309-320.

[21] Davies R J, Clark I R. Submarine slope failure primed and triggered by silica and its diagenesis[J]. Basin Research, 2006, 18(3): 339-350.

[22] Macquaker J H S, Bentley S J, Bohacs K M. Wave-enhanced sediment-gravity flows and mud dispersal across continental shelves: reappraising sediment transport processes operating in ancient mudstone successions[J]. Geology, 2010, 38(10): 947-950.

[23] Kranck K, Smith P C, Milligan T G. Grain-size characteristics of fine-grained unflocculated sediments II: ‘multi-round’ distributions[J]. Sedimentology, 1996, 43(3): 597-606.

[24] van Leussen W. Macroflocs, fine-grained sediment transports, and their longitudinal variations in the Ems Estuary[J]. Ocean Dynamics, 2011, 61(2/3): 387-401.

[25] Plint A G, Macquaker J H S, Varban B L. Bedload transport of mud across a wide, storm-influenced ramp: Cenomanian-Turonian Kaskapau Formation, Western Canada Foreland Basin[J]. Journal of Sedimentary Research, 2012, 82(11): 801-822.

[26] Schieber J, Southard J B, Schimmelmann A. Lenticular shale fabrics resulting from intermittent erosion of water-rich muds-interpreting the rock record in the light of recent flume experiments[J]. Journal of Sedimentary Research, 2010, 80(1): 119-128.

[27] Schieber J, Southard J B. Bedload transport of mud by floccule ripples-direct observation of ripple migration processes and their implications[J]. Geology, 2009, 37(6): 483-486.

[28] Piper D J W. Turbidite muds and silts on deep sea fans and abyssal plains[M]//Stanley D J, Kelling G. Sedimentation in submarine Canyons, Fans, and Trenches. Stroudsburg, PA: Dowden, Hutchinson & Ross, 1978: 163-176.

[29] 秦建华. 南盘江印支期前陆盆地泥质浊积岩沉积特征及其环境意义[J]. 岩相古地理,1991(5):11-18. [Qin Jianhua. Sedimentary characteristics and environmental significance of the muddy turbidites in the Indosinian Nanpanjiang Foreland Basin[J]. Lithofacies Palaeogeography, 1991(5): 11-18.]

[30] 庞雄,朱明,柳保军,等. 南海北部珠江口盆地白云凹陷深水区重力流沉积机理[J]. 石油学报,2014,35(4):646-653. [Pang Xiong, Zhu Ming, Liu Baojun, et al. The mechanism of gravity flow deposition in Baiyun sag deepwater area of the northern South China Sea[J]. Acta Petrolei Sinica, 2014, 35(4): 646-653.]

[31] Amendola U, Perri F, Critelli S, et al. Composition and provenance of the Macigno Formation (Late Oligocene-Early Miocene) in the Trasimeno Lake area (northern Apennines)[J]. Marine and Petroleum Geology, 2016, 69: 146-167.

[32] Kirby R, Parker W R. Distribution and behavior of fine sediment in the Severn Estuary and inner Bristol Channel, U.K.[J]. Canadian Journal of Fisheries and Aquatic Sciences, 1983, 40(S1): S83-S95.

[33] MacKay D A, Dalrymple R W. Dynamic mud deposition in a tidal environment: the record of fluid-mud deposition in the Cretaceous Bluesky Formation, Alberta, Canada[J]. Journal of Sedimentary Research, 2011, 81(12): 901-920.

[34] Ogston A S, Cacchione D A, Sternberg R W, et al. Observations of storm and river flood-driven sediment transport on the northern California continental shelf[J]. Continental Shelf Research, 2000, 20(16): 2141-2162.

[35] Traykovski P, Geyer W R, Irish J D, et al. The role of wave-induced density-driven fluid mud flows for cross-shelf transport on the Eel River continental shelf[J]. Continental Shelf Research, 2000, 20(16): 2113-2140.

[36] Traykovski P, Wiberg P L, Geyer W R. Observations and modeling of wave-supported sediment gravity flows on the Po prodelta and comparison to prior observations from the Eel shelf[J]. Continental Shelf Research, 2007, 27(3/4): 375-399.

[37] Bhattacharya J P, MacEachern J A. Hyperpycnal rivers and prodeltaic shelves in the Cretaceous Seaway of North America[J]. Journal of Sedimentary Research, 2009, 79(4): 184-209.

[38] Lowe D R, Guy M. Slurry-flow deposits in the Britannia Formation (Lower Cretaceous), North Sea: a new perspective on the turbidity current and debris flow problem[J]. Sedimentology, 2000, 47(1): 31-70.

[39] Schieber J. Mud re-distribution in epicontinental basins-Exploring likely processes[J]. Marine and Petroleum Geology, 2016, 71: 119-133.

[40] 袁选俊,林森虎,刘群,等. 湖盆细粒沉积特征与富有机质页岩分布模式——以鄂尔多斯盆地延长组长7油层组为例[J]. 石油勘探与开发,2015,42(1):34-43. [Yuan Xuanjun, Lin Senhu, Liu Qun, et al. Lacustrine fine-grained sedimentary features and organic-rich shale distribution pattern: A case study of Chang 7 Member of Triassic Yanchang Formation in Ordos Basin, NW China[J]. Petroleum Exploration and Development, 2015, 42(1): 34-43.]

[41] 蒲秀刚,周立宏,韩文中,等. 细粒相沉积地质特征与致密油勘探——以渤海湾盆地沧东凹陷孔店组二段为例[J]. 石油勘探与开发,2016,43(1):1-10. [Pu Xiugang, Zhou Lihong, Han Wenzhong, et al. Geologic features of fine-grained facies sedimentation and tight oil exploration: A case from the second Member of Paleogene Kongdian Formation of Cangdong sag, Bohai Bay Basin[J]. Petroleum Exploration and Development, 2016, 43(1): 1-10.]

[42] Hansen L, L’Heureux J S, Longva O. Turbiditic, clay-rich event beds in fjord-marine deposits caused by landslides in emerging clay deposits-palaeoenvironmental interpretation and role for submarine mass-wasting[J]. Sedimentology, 2011, 58(4): 890-915.

[43] Covault J A, Kostic S, Paull C K, et al. Submarine channel initiation, filling and maintenance from sea-floor geomorphology and morphodynamic modelling of cyclic steps[J]. Sedimentology, 2014, 61(4): 1031-1054.

[44] Talling P J, Wynn R B, Masson D G, et al. Onset of submarine debris flow deposition far from original giant landslide[J]. Nature, 2007, 450(7169): 541-544.

[45] Talling P J. On the triggers, resulting flow types and frequencies of subaqueous sediment density flows in different settings[J]. Marine Geology, 2014, 352: 155-182.

[46] Addington L D, Kuehl S A, McNinch J E. Contrasting modes of shelf sediment dispersal off a high-yield river: Waiapu River, New Zealand[J]. Marine Geology, 2007, 243(1/2/3/4): 18-30.

[47] Parsons J D, Bush J W M, Syvitski J P M. Hyperpycnal plume formation from riverine outflows with small sediment concentrations[J]. Sedimentology, 2001, 48(2): 465-478.

[48] Yoshida M, Yoshiuchi Y, Hoyanagi K. Occurrence conditions of hyperpycnal flows, and their significance for organic-matter sedimentation in a Holocene estuary, Niigata Plain, Central Japan[J]. Island Arc, 2009, 18(2): 320-332.

[49] Migeon S, Mulder T, Savoye B, et al. Hydrodynamic processes, velocity structure and stratification in natural turbidity currents: results inferred from field data in the Var Turbidite System[J]. Sedimentary Geology, 2012, 245-246: 48-62.

[50] Turowski J M, Hilton R G, Sparkes R. Decadal carbon discharge by a mountain stream is dominated by coarse organic matter[J]. Geology, 2016, 44(1): 27-30.

[51] 杨仁超,金之钧,孙冬胜,等. 鄂尔多斯晚三叠世湖盆异重流沉积新发现[J]. 沉积学报,2015,33(1):10-20. [Yang Renchao, Jin Zhijun, Sun Dongsheng, et al. Discovery of hyperpycnal flow deposits in the Late Triassic lacustrine Ordos Basin[J]. Acta Sedimentologica Sinica, 2015, 33(1): 10-20.]

[52] 孙福宁,杨仁超,李冬月. 异重流沉积研究进展[J]. 沉积学报,2016,34(3):452-462. [Sun Funing, Yang Renchao, Li Dongyue. Research progresses on hyperpycnal flow deposits[J]. Acta Sedimentologica Sinica, 2016, 34(3): 452-462.]

[53] Mulder T, Syvitski J P M. Turbidity currents generated at river mouths during exceptional discharges to the world oceans[J]. The Journal of Geology, 1995, 103(3): 285-299.

[54] Mulder T, Migeon S, Savoye B, et al. Twentieth century floods recorded in the deep Mediterranean sediments[J]. Geology, 2001, 29(11): 1011-1014.

[55] Mulder T, Syvitski J P M, Migeon S, et al. Marine hyperpycnal flows: initiation, behavior and related deposits. A review[J]. Marine and Petroleum Geology, 2003, 20(6/7/8): 861-882.

[56] Lamb M P, Mohrig D. Do hyperpycnal-flow deposits record river-flood dynamics[J]. Geology, 2009, 37(12): 1067-1070.

[57] Bourget J, Zaragosi S, Mulder T, et al. Hyperpycnal-fed turbidite lobe architecture and recent sedimentary processes: a case study from the Al Batha turbidite system, Oman margin[J]. Sedimentary Geology, 2010, 229(3): 144-159.

[58] Pouderoux H, Proust J N, Lamarche G, et al. Postglacial (after 18 ka) deep-sea sedimentation along the Hikurangi subduction margin (New Zealand): characterisation, timing and origin of turbidites[J]. Marine Geology, 2012, 295-298: 51-76.

[59] Khripounoff A, Vangriesheim A, Crassous P, et al. High frequency of sediment gravity flow events in the Var submarine canyon (Mediterranean Sea)[J]. Marine Geology, 2009, 263(1/2/3/4): 1-6.

[60] Yao Y, Flemings P, Mohrig D. Dynamics of dilative slope failure[J]. Geology, 2012, 40(7): 663-666.

[61] Clare M A, Talling P J, Challenor P, et al. Distal turbidites reveal a common distribution for large (>0.1 km3) submarine landslide recurrence[J]. Geology, 2014, 42(3): 263-266.

[62] 何起祥. 沉积动力学若干问题的讨论[J]. 海洋地质与第四纪地质,2010,30(4):1-10. [He Qixiang. A discussion on sediment dynamics[J]. Marine Geology & Quaternary Geology, 2010, 30(4): 1-10.]

[63] Soyinka O A, Slatt R M. Identification and micro-stratigraphy of hyperpycnites and turbidites in Cretaceous Lewis Shale, Wyoming[J]. Sedimentology, 2008, 55(5): 1117-1133.

[64] Brunner C A, Normark W R, Zuffa G G, et al. Deep-sea sedimentary record of the late Wisconsin cataclysmic floods from the Columbia River[J]. Geology, 1999, 27(5): 463-466.

[65] Kane I A, Pontén A S M. Submarine transitional flow deposits in the Paleogene Gulf of Mexico[J]. Geology, 2012, 40(12): 1119-1122.

[66] 王陆新,吴朝东,莫午零,等. 松辽盆地嫩江组泥质三角洲沉积特征及沉积机理[J]. 北京大学学报:自然科学版,2014,50(3):497-506. [Wang Luxin, Wu Chaodong, Mo Wuling, et al. Sedimentary characteristics and identification of muddy deltaic in Nenjiang Formation of Songliao Basin[J]. Acta Scientiarum Naturalium Universitatis Pekinensis, 2014, 50(3): 497-506.]

[67] Sumner E J, Talling P J, Amy L A. Deposits of flows transitional between turbidity current and debris flow[J]. Geology, 2009, 37(11): 991-994.

[68] Talling P J, Masson D G, Sumner E J, et al. Subaqueous sediment density flows: depositional processes and deposit types[J]. Sedimentology, 2012, 59(7): 1937-2003.

[69] Sumner E J, Talling P J, Amy L A, et al. Facies architecture of individual basin-plain turbidites: comparison with existing models and implications for flow processes[J]. Sedimentology, 2012, 59(6): 1850-1887.

[70] Sumner E J, Siti M I, McNeill L C, et al. Can turbidites be used to reconstruct a paleoearthquake record for the central Sumatran margin[J]. Geology, 2013, 41(7): 763-766.

[71] Sawyer D E, Flemings P B, Nikolinakou M. Continuous deep-seated slope failure recycles sediments and limits levee height in submarine channels[J]. Geology, 2014, 42(1): 15-18.

[72] Baas J H, Manica R, Puhl E, et al. Processes and products of turbidity currents entering soft muddy substrates[J]. Geology, 2014, 42(5): 371-374.

[73] 李丕龙,姜在兴,马在平. 东营凹陷储集体与油气分布[M]. 北京:石油工业出版社,2000:47-80. [Li Peilong, Jiang Zaixing, Ma Zaiping. Reservoir and distribution of oil and gas in Dongying sag[M]. Beijing: Petroleum Industry Press, 2000: 47-80.]

[74] 刘军锷,简晓玲,康波,等. 东营凹陷东营三角洲沙三段中亚段古地貌特征及其对沉积的控制[J]. 油气地质与采收率,2014,21(1):20-23. [Liu Jun’e, Jian Xiaoling, Kang Bo, et al. Paleogeomorphology of the middle part of 3rdmember of Shahejie Formation and their effects on depositional systems, Dongying delta, Dongying depression[J]. Petroleum Geology and Recovery Efficiency, 2014, 21(1): 20-23.]

[75] 孔凡仙. 东营凹陷北带砂砾岩扇体勘探技术与实践[J]. 石油学报,2000,21(5):27-31. [Kong Fanxian. Exploration technique and practice of sandy-conglomeratic fans in the northern part of Dongying depression[J]. Acta Petrolei Sinica, 2000, 21(5): 27-31.]

[76] 陈杰,刘传虎,谭明友,等. 进积型三角洲交汇区沉积模式——以东营凹陷沙三中亚段为例[J]. 沉积学报,2016,34(6):1187-1197. [Chen Jie, Liu Chuanhu, Tan Mingyou, et al. Depositional model of prograding delta confluences: A case from Es3mmembers in the Paleogene Dongying sag[J]. Acta Sedimentologica Sinica, 2016, 34(6): 1187-1197.]

[77] Yang Renchao, van Loon A J, Yin Wei, et al. Soft-sediment deformation structures in cores from lacustrine slurry deposits of the Late Triassic Yanchang Fm. (central China)[J]. Geologos, 2016, 22(3): 201-211.

[78] Yang Renchao, Jin Zhijun, van Loon A J, et al. Climatic and tectonic controls of lacustrine hyperpycnite origination in the Late Triassic Ordos Basin, central China: implications for unconventional petroleum development[J]. AAPG Bulletin, 2017, 101(1): 95-117.

[79] Schieber J, Krinsley D, Riciputi L. Diagenetic origin of quartz silt in mudstones and implications for silica cycling[J]. Nature, 2000, 406(6799): 981-985.

Research Progresses on Muddy Gravity Flow Deposits and Their Significances on Shale Oil and Gas: A case study from the 3rdoil-member of the Paleogene Shahejie Formation in the Dongying Sag

SONG MingShui1, XIANG Kui1, ZHANG Yu1, CAI Pan1, LIU JianLei1, YANG RenChao2

1. Exploration Management Center, Shengli Oilfield Company, SINOPEC, Dongying, Shandong 257017, China 2. College of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China

With promotion of shale oil and gas development on intensive studies on depositional mechanisms of mudstone and shales, transportation and deposition of fine-grained sediment have currently become hot topics in both sedimentoligical studies and petroleum industries. However, muddy gravity flow deposits in the Cenozoic lacustrine environment have not yet arisen attentions of geologists, although literatures of gravity flow-generated muddy deposits in marine environments extensively existed. Based on extensive literature researches, detailed core examinations and thin section observations, this paper analyzes characteristics of gravity flow-generated fine-grained deposits in the 3rdoil-member of the Paleogene Shahejie Formation (E2s3), Dongying Sag, Bohai Bay Basin. Discussions on their forming mechanisms have theoretical significances on lacustrine sedimentary environment study and have practical meanings on developments of shale oil and gas. Results: 1) there are various gravity flow deposits, including muddy mass flows, muddy debris flows, muddy turbidity currents and muddy hyperpycnal flows exist in E2s3in the Dongying Sag; 2) muddy slumps, muddy debrites, muddy turbidites and muddy hyperpycnites co-generate and co-exist in spatio-temporal extents. Conclusions: 1) muddy sediments can deposit in turbulent waterbody and high hydrodynamic conditions; 2) muddy gravity flow deposits play an important role in deep water sedimentary regions; 3) muddy gravity flows are of great importance to transportation and deposition of coarse grains and organic matters, and so to preservation of organic matters; 4) muddy gravity flow deposits have important geological significances on unconventional oil and gas.

gravity flow-generated fine-grained deposits; muddy debrites; muddy turbidites; muddy hyperpycnites; unconventional oil and gas; Dongying Sag; Paleogene

1000-0550(2017)04-0740-12

10.14027/j.cnki.cjxb.2017.04.008

2016-11-07; 收修改稿日期: 2017-01-12

山东省重大科技创新工程项目(2017CXGC1608);国家自然科学基金项目(41372135,41672120);山东科技大学科研团队计划(2015TDJH101)[Foundation: Major Scientific and Technological Innovation Project of Shandong Province, No.2017CXGC1608; National Natural Science Foundation of China, No.41372135, 41672120; SDUST Research Fund, No. 2015TDJH101]

宋明水,男,1964年生,博士,教授级高工,油田勘探与管理,E-mail: songmingshui.slof@sinopec.com

杨仁超,男,副教授,E-mail: yang100808@126.com

P618.13 TE121.1

A

猜你喜欢
东营细粒碎屑
Sweet Carrots甜甜的胡萝卜
细粒级尾砂高浓度胶结充填试验研究与工业应用
滇西澜沧岩群碎屑锆石U-Pb定年及其地质意义
清洁搅拌机的小妙招
陕西青年作家采风团走进山东东营
渤中X油田沙一段生物碎屑白云岩井场识别方法
济阳陆相断陷湖盆泥页岩细粒沉积层序初探
微细粒磁铁矿提铁降硫试验研究
山东东营黎宁化工有限公司
颈康细粒剂配合两联疗法治疗神经根型颈椎病46例