Status and Trends in Research on Deep-Water Gravity Flow Deposits

Deep-water gravity flows are one of the most important sediment transport mechanisms on Earth. After 60 years of study, significant achievements have been made in terms of classification schemes, genetic mechanisms, and depositional models of deep-water gravity flows. The research history of deep-water gravity flows can be divided into five stages： incipience of turbidity current theory; formation of turbidity current theory; development of deep-water gravity flow theory; improvement and perfection of deep-water gravity flow theory; and comprehensive development of deep-water gravity flow theory. Currently, three primary classification schemes based on the sediment support mechanism, the rheology and transportation process, and the integration of sediment support mechanisms, rheology, sedimentary characteristics, and flow state are commonly used.Different types of deep-water gravity flow events form different types of gravity flow deposits. Sediment slump retransportation mainly forms muddy debris flows, sandy debris flows, and surge-like turbidity currents. Resuspension of deposits by storms leads to quasi-steady hyperpycnal turbidity currents （hyperpycnal flows）. Sustainable sediment supplies mainly generate muddy debris flows, sandy debris flows, and hyperpycnal flows. Deep-water fans, which are commonly controlled by debris flows and hyperpycnal flows, are triggered by sustainable sediment supply; in contrast, deep-water slope sedimentary deposits consist mainly of debris flows that are triggered by the retransportation of sediment slumps and deep-water fine-grained sedimentary deposits are derived primarily from fine- grained hyperpycnal flows that are triggered by the resuspension of storm deposits. Harmonization of classification schemes, transformation between different types of gravity flow deposit, and monitoring and reproduction of the sedimentary processes of deep-water gravity flows as well as a source-to-sink approach to document the evolution and deposition of deep-water gravity flows are the most important research aspects for future studies of deep-water gravity flows study in the future.

An Upward Shallowing Succession of Gravity Flow Deposits in the Early Cretaceous Lingshandao Formation,Western Yellow Sea

Objective Several well-exposed gravity flow deposits in the Early Cretaceous Lingshandao Formation provide a rare opportunity to study deep-water processes. The main objective of this work is to establish the spatial and temporal relationships between the various gravity flow deposits, and thus to establish their sequence stratigraphic patterns and depositional conditions.

Temporal and Spatial Seasonal Variations in Quality of Gravity Flow Water in Kyanamira Sub-County, Kabale District, Uganda

The study was designed to investigate temporal and spatial seasonal variations in quality properties of gravity flow water samples collected from Kigata, Kacuro, Kihanga, Kitibya and Kanjobe located in Kyanamira Sub-County, Kabale District, Uganda. Physical, chemical and biological parameters such as pH, temperature, dissolved oxygen, total dissolved solids, electrical conductivity, turbidity, colour and total suspended solids, total hardness, total alkalinity, chloride, fluoride, nitrates-N, nitrites-N, ammonium-N, sulphates, total phosphate, sodium, calcium, magnesium and some heavy metals were analyzed. Total iron, lead, chromium, copper, zinc, manganese and cadmium were analyzed by atomic absorption spectrometry. Two of the basic biological parameters for drinking water such as faecal coliforms and salmonella were analyzed by incubation followed by counting colony forming units (CFUs). Statistical presentations of data including cluster analysis, dendrograms and principal component analysis were used with the assistance of PAST software. Temperature, pH, TDS dissolved oxygen, cations, anions (chemical parameters) and salmonella, faecal coliforms were the major contributing parameters to gravity flow water’s quality variations during both seasons. Values of pH ranged between 3.78 and 4.84 from March to August in all study sites and they were consistently below the WHO permissible pH range of 6.5 - 8.5. Total suspended solids ranged between 0.66 and 2.17 mg·L-1 and were above the recommended WHO limit of zero value in all study sites. Salmonella and faecal coliforms colonies were present in scaring numbers in the wet season. In March, salmonella counts at Kacuro (14 CFU) and Kanjobe (128 CFU) while faecal coliforms counts at Kacuro (515 CFU) and Kanjobe (228 CFU). The findings of this study call for special attention when using gravity flow water.

Effects of Seasonal Variations in Physical Parameters on Quality of Gravity Flow Water in Kyanamira Sub-County, Kabale District, Uganda

The effect of seasonal variations in physical parameters on quality of gravity flow water was investigated in Kyanamira Sub-County, Kabale District, Uganda. The seasonal variations in the physical parameters (pH, temperature, electrical conductivity (EC), turbidity, colour, total dissolved solids (TDS), and total suspended solids (TSS)) were determined during wet and dry seasons. Composite samples from gravity flow water sources were collected monthly from March to August, 2014 and then analyzed. Temperature was measured using thermometer;pH, EC and TDS were determined using a multimeter, turbidity, colour and total suspended solids were determined by spectrophotometric method. TDS, pH and temperature were the most contributing parameters to water quality variations in both seasons. The mean pH values varied between 3.78 - 4.84 from March to August, 2014 at all study sites. These pH values were consistently below the WHO permissible range of 6.5 - 8.5. Similarly, total suspended solids varied between 0.66 - 2.17 mg·L-1 and were well above the recommended WHO limit of zero mg·L-1 at all study sites. Turbidity mean values varied between 0.83 - 3.7 NTU and were outside the recommended limits of 3 NTU at Kigata (3.7 NTU) only. Temperatures (20.3°C - 21.15°C) for all the study sites were within the recommended limit of 20°C - 30°C in water for domestic purposes. The mean values of physical parameters for the wet season were: temperature (21.12°C), colour (12.5 PtCoU), turbidity (3.4 NTU), TDS (76.76 mg·L-1), TSS (2.13 mg·L-1), pH (4.19) and EC (152.7 μS·cm-1) were different from those of the dry season (temperature (20.99°C), colour (0.93 PtCoU), turbidity (0.53 NTU), TDS (77.33 mg·L-1), TSS (0.67 mg·L-1), pH (4.86) and EC (158.65 μS·cm-1). Basing on these findings above, it was evident to justify discouraging the use of gravity flow water at these study sites for domestic purposes without proper treatment.

Observed characteristics of flow,water mass,and turbulent mixing in the Preparis Channel

Preparis Channel is the very important exchange path of energy and materials between the northern Bay of Bengal and Andaman Sea(AS).A set of hydrographic measurements,a microstructure profiler,and a deep mooring were used to determine the characteristics of water masses,turbulent mixing,and flows in the Preparis Channel.The unprecedented short-term mooring data reveal that a deep current in the deep narrow passage(below 400 m)of the Preparis Channel flows toward the Bay of Bengal(BoB)with a mean along-stream velocity of 25.26 cm/s at depth of 540 m;above the deep current,there are a relatively weak current flows toward the AS with a mean along-stream velocity of 15.46 cm/s between 500 m and 520 m,and another weak current flows toward the BoB between 430 m and 500 m.Thus,a sandwiched vertical structure of deep currents(below 400 m)is present in the Preparis Channel.The volume transport below 400 m is 0.06 Sv(1 Sv=106 m^(3)/s)from the AS to the BoB.In the upper layer(shallower than 300 m),the sea water of the AS is relatively warmer and fresher than that in the BoB,indicating a strong exchange through the channel.Microstructure profiler observations reveal that the turbulent diffusivity in the upper layer of the Preparis Channel reaches O(10−4 m^(2)/s),one order larger than that in the interior of the BoB and over the continental slope of the northern AS.We speculate that energetic high-mode internal tides in the Preparis Channel contribute to elevated turbulent mixing.In addition,a local“hotspot”of turbidity is identified at the deep mooring site,at depth of about 100 m,which corresponds to the location of elevated turbulent mixing in the Preparis Channel.

The patterns of surface capillary-gravity short-crested waves with uniform current fields in coastal waters

A fully three-dimensional surface gravitycapillary short-crested wave system is studied as two progressive wave-trains of equal amplitude and frequency, which are collinear with uniform currents and doubly-periodic in the horizontal plane, are propagating at an angle to each other. The first- and second-order asymptotic analytical solutions of the short-crested wave system are obtained via a perturbation expansion in a small parameter associated with the wave steepness, therefore depicting a series of typical three-dimensional wave patterns involving currents, shallow and deep water, and surface capillary waves, and comparing them with each other.

Proof of Six-Wave Resonance Conditions of Ocean Surface Gravity Waves in Deep Water

A necessary big step up in the modern water wave theories and their widespread application in ocean engineering is how to obtain 6-wave resonance conditions and to prove it. In the light of the existing forms and characteristics of 3-wave, 4-wave and 5-wave resonance conditions, the 6-wave resonance conditions are proposed and proved for currently a maximum wave-wave resonance interactions of the ocean surface gravity waves in deep water, which will be indispensable to both the Kolmogorov spectrum of the corresponding universal wave turbulence and a synthetic 4-5-6-wave resonant model for the ocean surface gravity waves.

三角洲型被动陆缘盆地陆坡地貌演化研究——以尼日尔三角洲盆地某深水研究区为例

【目的】陆坡因其巨大的沉积物总量和丰富的油气资源而成为勘探的热点领域。明确陆坡地貌演化特征能够助力于深水沉积学研究和油气勘探。研究旨在针对三角洲型被动陆缘盆地陆坡具有强物源供给条件的特征,探索一种基于沉积构型原理的古陆坡地貌演化研究新方法。【方法】以尼日尔三角洲盆地某陆坡研究区为例,综合应用地震、测井和岩心资料,根据13个层序的沉积构型时—空演化规律反演古陆坡地貌演化特征。【结果】研究区中新世至今的地貌演化过程经历了两个阶段。阶段1中,地貌演化受大型三角洲进积驱动,研究区由深海平原演化为陆坡,地貌始终为非限制型。阶段2中,在重力滑动作用下先后经历了由逆冲断层、泥底辟、填平补齐主导的演化过程,地貌由限制型、半限制型演变为现今的非限制型。逆冲断层期,泥底辟强度有限,地貌形态受控于断层活动,研究区处于重力滑动体系的远缘逆冲构造区。泥底辟期,底辟强度大幅增强,具备了独立改造地貌格局的能力,研究区由逆冲构造区向泥底辟构造区转化。【结论】重力滑动体系由沉积作用驱动,表现出与沉积相类似的空间组合与演化特征。平面上相邻的伸展、泥底辟、逆冲构造区存在成因关联,与具有排序特征的沉积相类似。因此,研究区两期构造活动的叠合关系指示了陆坡向海推进的过程。综上,典型深水研究区沉积构型的时—空演化特征能够为陆坡古地貌演化过程的恢复提供重要依据。

深海重力流与底流交互作用的沉积响应及其勘探意义

顺坡而下的重力流(浊流)与沿坡流动的底流(等深流)之间的交互作用是当前国际沉积学研究的前沿领域与薄弱环节,交互作用沉积体系及其沉积特征相较于重力流或等深流沉积体系仍“知之甚少”。本文总结了论文作者所识别的两种典型交互作用沉积体系的形态特征、沉积特征与沉积样式,查明了交互作用成因优质储层的识别标志与分布模式。深水单向迁移水道具有不对称的剖面形态与持续稳定向陡岸一侧迁移叠加的沉积样式,可进一步分为迁移方向与参与其建造底流流向相同(顺向迁移)和相反(反向迁移)两种类型;深水单向迁移朵叶具有长轴方向与区域等深线平行的形态特征以及侧向迁移延伸方向与区域等深线一致的沉积样式。重力流(浊流)与底流(等深流)交互作用所形成的底流改造砂/交互作用砂具有与浊积砂迥异的沉积特征,如富含有孔虫和生物骨骼,无年龄倒序现象出现,突变非侵蚀接触顶界面,含有大洋水团所伴生的底栖有孔虫,可见牵引流沉积特征(如两到三段式累积概率分布特征、单峰正态的频率分布特征和位于C-M图牵引流沉积区等),这些沉积特征可作为底流改造砂的识别相标志。在剖面上,底流改造砂总是向水道迁移一侧不断迁移叠加,具有“单向叠加、有序展布”的分布模式;在平面上,底流改造砂总是沿区域等深线侧向迁移,具有“单向偏移、侧向叠置”的分布模式;时空上形成连续性好、分布范围广、面积大的超大型优质深水油气储集体。

融合多种模态特征的井下供水管网流量预测

煤矿井下供水系统是煤矿安全生产的生命线,供水管网水流量的预测是供水系统优化调度的基础,预测的重要性对供水调度有重要影响。文章提出了一种融合多模态数据特征的煤矿井下供水管网流量预测方法,该方法通过图深度学习的方法实现了对井下管网空间拓扑结构、历史时间依赖、井下实际生产工况、周期相关等多种数据模态特征的融合,具体的,使用添加空间注意机制的图卷积神经网络获取井下管网监测点的空间拓扑关系,然后利用循环神经网络中的门控循环单元获取监测点的时间依赖,并融合煤矿生产规律与不同周期的流量数据形成最终预测结果,通过陕西亭南煤矿实际数据进行实验,结果表明,提出的预测方法相较于SVM、LSTM、STGCN等方法能更准确地预测井下流量未来的趋势,预测偏差分别降低了9.3%、6.84%和3.65%。

陆相坳陷湖盆深水重力流沉积类型、模式及控制因素分析——以鄂尔多斯盆地延长组长7段为例

鄂尔多斯盆地长7深水沉积是大型坳陷湖盆深水重力流的典型代表。基于多口取心井厘米级岩心描述和测录井、薄片资料,对长7深水重力流沉积的类型、特征、流体性质和沉积演化过程进行探索。明确深水沉积包括4种类型:深湖泥页岩沉积、滑塌沉积、砂质碎屑流沉积、浊流沉积。剖面上三角洲前缘砂体在外力触发条件下发生滑塌,转变为砂质碎屑流,最终演化为浊流。平面上三角洲前缘坡折带末端发育大面积砂质碎屑流舌状体,其前端的浊流沉积呈扇状分布。鄂尔多斯盆地晚三叠世独特的构造背景、气候条件以及强烈的造山活动,造就了鄂尔多斯盆地特有的重力流沉积模式。砂质碎屑流和浊流砂体分别对应长7页岩油的一类、二类砂体,具有近源成藏的优势,油气资源量可观,目前已产生规模效益。

喜马拉雅北缘石炭系纳兴组事件沉积的发现及意义

石炭系纳兴组事件沉积的发育对明确喜马拉雅北缘盆地属性和构造背景具有重要指示意义。通过野外地质调查在石炭系纳兴组下部识别出典型深水重力流沉积,并新发现大量软沉积物变形构造。深水重力流主要包括滑塌沉积和砂质碎屑流沉积,浊流沉积发育有限。负载构造、火焰构造、液化砂岩脉和液化角砾岩的发育指示地震触发软沉积物变形构造特征。综合区域地质背景,纳兴组深水重力流和软沉积物变形构造特征表明石炭纪喜马拉雅北缘处于被动陆缘裂谷环境。

东非海岸盆地第四系深水沉积特征、过程及沉积模式

东非海岸盆地深水区的研究主要集中在油气富集的深部地层,缺乏对第四系深水沉积的研究。文中利用二维地震资料,对东非坦桑尼亚和鲁伍马盆地第四系深水区的深水沉积开展研究,查明了沉积类型,划分了沉积单元,对深水沉积建立了沉积模式。研究表明:1)研究区发育深水重力流沉积、等深流沉积、等深流与重力流交互作用沉积,分为峡谷、水道、漂积体及块状搬运复合体4种沉积单元。2)研究区深水沉积由北至南差异明显,坦中地区深水沉积规模较大,主要发育重力流水道及丘状漂积体;坦南地区发育峡谷,深水沉积规模整体较小;鲁北地区深水沉积规模较大,发育有峡谷、水道及席状漂积体。3)海底地形的差异导致坦中地区的重力流能量较弱,坦南地区和鲁北地区的重力流能量较强;在海底地貌的限制下,等深流沉积在坦中地区形成丘状漂积体,在鲁北地区形成席状漂积体;坦中南部的等深流与重力流发生交互作用,发育向南迁移的侧向迁移水道。

鄂尔多斯盆地东南部三叠系长7油层组深水沉积特征及演化规律

以沉积学理论为指导,利用野外露头、钻井岩心、测井等资料,对鄂尔多斯盆地东南部三叠系长7油层组深水沉积特征包括相标志、沉积微相类型等进行了研究,并揭示了其沉积演化规律。研究结果表明:(1)鄂尔多斯盆地东南部三叠系长7油层组深水沉积的相标志包括:岩石中常见水平层理、鲍马序列、槽模沟模、滑动与滑塌构造、撕裂屑、泥包砾等沉积构造,含有深水双壳类和鱼类动物化石,粒度概率曲线中悬浮总体含量大且分选差,测井曲线上可见锯齿状、齿化箱形-钟形-指形、泥岩基线等特征。(2)研究区长7物源主要来自东北和南部2个方向,发育深湖—半深湖、湖底扇、浅湖沉积,湖底扇包括浊流和砂质碎屑流2种重力流类型,可进一步划分为重力流主水道、溢流沉积、重力流分支水道、分支水道间、朵叶体等微相。湖底扇主水道主要为砂质碎屑流沉积,分支水道和朵叶体主要为浊流沉积。(3)研究区长7沉积期,中南部主体发育深湖—半深湖、湖底扇沉积,东北部发育浅湖沉积;其中,东北方向发育4个湖底扇体,南部发育2个湖底扇体,半深湖/浅湖界线呈北西向延伸于延安—甘泉一带。长7^(3)亚段沉积期,深湖—半深湖范围最大,仅局部发育湖底扇;长7^(2)、长7^(1)亚段沉积期,湖底扇逐步增多,深湖—半深湖范围有所缩小,整体呈深湖—半深湖与湖底扇交互沉积态势。

山丘区自压输水管道水锤计算与模拟方法

为了准确预测和防护山丘区自压输水管道的水锤破坏,提高管道输水的安全性和可靠性,针对山丘区自压输水管道落差大、距离长和地势起伏的特点,提出将输水管道划分为弯曲段和带倾斜角度的直管段,利用极限思想将弯曲管段基于切线的曲线拟合矢量化方法,拟合为沿管道中心线具有相同过流断面的多段等效短管;采用拟合等效短管和倾斜直管相结合的方法进行水锤计算,建立了自压输水管道的数值计算模型.以陕西省千阳县一自压管道输水工程为例进行了验证分析,通过模拟管道末端阀门不同关阀时间的水锤压力变化规律,得出最优关阀时间为50 s≤T≤120 s,提出了相应的水锤防护方案.结果表明该方法的计算和模拟精度高,可为山丘区长距离自压管道输水工程建设与管理提供参考.

重力流和加压泵刚性串联供水系统的停泵水锤防护

以江西省某供水工程为例,针对重力流和加压泵刚性串联供水系统的停泵水锤防护问题,基于停泵水锤计算模型,从泵出口阀驱动方式选择、最小水锤压力防护标准拟定、泵出口阀关闭规律优化、空气阀水锤防护效果等方面开展水锤防护研究。结果表明,该类供水系统在事故停泵、泵出口阀拒动工况下,水泵将最终稳定在正转、正流、负扬程的制动耗能工况区,因此泵出口阀必须采用外力驱动才能实现机组断流。事故停泵后,水泵上游段将首先产生升压波而水泵段将首先产生降压波,由于水泵进水管不允许进气,水泵上、下游管段的最小水锤压力可分别按+2m和-2m控制。根据实例工程特点,泵出口阀两段关闭优于线性关闭,但对水泵出水管线中的负压和汽化现象无改善作用;在水泵下游管段合理设置防水锤型空气阀,可有效改善负压状况。

深层页岩气井气水两相缝网参数反演方法

深层页岩气藏的开发离不开大规模的体积压裂技术,而缝网参数反演方法是压裂效果评价、产能动态分析的一种重要手段。现有的缝网参数反演方法忽略了支撑剂不均匀分布和气水两相渗流对深层页岩气藏开发的影响,导致参数反演误差较大,且难以区分“近井支撑裂缝”和“远井未支撑裂缝”对产能的贡献。针对这一问题,基于动态分析方法,建立了考虑多重非线性流动机理和未完全支撑裂缝的深层页岩储层气水两相缝网参数反演方法。反演方法建立过程中基于线性流模型假设,将压后的复杂裂缝网络等效为支撑裂缝区、压裂改造内区、未支撑裂缝区和压裂改造外区4个区域,采用变量替换、摄动变换、逐次替换等手段处理气体高压物性参数、超临界吸附、应力敏感、非达西渗流和气水两相渗流引起的非线性。利用数值模拟模型验证了本文方法的可靠性,并选取四川盆地4口深层页岩气井进行了应用分析。结果表明,建立的深层页岩气水两相缝网参数反演方法考虑了气液同产对产能预测和参数反演的影响,实现了支撑与未支撑裂缝半长和渗透率等参数的定量区分,为准确计算深层页岩气产量、评价压裂效果提供了理论指导。

大鼠血流缓慢模型的制备

目的通过皮下反复注射肾上腺素、冰水游泳后观察血液流变学指标和双下肢超声结果,以构建血栓形成前的大鼠血流缓慢模型。方法选取12只健康SD大鼠,肾上腺素组(n=6)皮下注射0.8 mL/kg肾上腺素,2 h后冰水游泳5 min,注射4 h后再次注射,并禁食16 h。生理盐水组(n=6)皮下注射0.8 mL/kg生理盐水,其制备方法与肾上腺素组一致。造模完成后,行双下肢股静脉超声和血液流变学检查。结果两组大鼠双下肢均无明显肿胀。在冰水游泳第1 min内,肾上腺素组大鼠较生理盐水组兴奋(P=0.015)。超声结果显示,两组大鼠股静脉均无明显血栓形成,但是肾上腺素组的右侧股静脉流速比生理盐水组低(P<0.001)。血液流变学结果显示,肾上腺素组大鼠的全血粘度低切(P=0.024)及血浆粘度(P=0.004)较生理盐水组高。结论通过大鼠皮下反复注射肾上腺素及冰水游泳,并利用血液流变学和超声检查,可以构建大鼠血流缓慢模型。

入口弯管结构对重力式油水分离器内流场的影响

采用Fluent软件紊流计算中的标准k-ε模型,对安装不同结构参数入口弯管的重力式油水分离器内部流场进行数值模拟,得到含有3个出口位置、4种入射角度和4种不同轴向位置入口弯管的分离器内部流动特性.分析比较研究结果可以得出:入口弯管出口距筒体顶端内壁面越小,筒体对入射流体的阻碍作用越佳,流体通过整流构件后产生的返混区域越小;弯管入射角度在30°、60°和120°时,整流构件后方均产生涡旋,流场紊乱程度大,入射角度为90°时没有涡旋产生,流体流动相对最为平稳;入口弯管越靠近封头,整流构件前涡旋区域越小,整流效果越佳,后部流场轴向流动比例越多,越有利于油水两相分离.

合水地区Z183区块长72致密储层宏观非均质性及其主控因素

基于合水地区Z183区块长72储层岩心、薄片、压汞等资料,从层内、层间、平面三个方面开展宏观非均质性特征描述。结果表明,区内发育砂质碎屑流、浊流、滑塌三类深水重力流沉积与泥质夹层、钙质夹层两类层内夹层,其中泥质夹层在沉积物中出现频率较高;区内砂体叠置关系可分为四类,对层间非均质性控制程度由弱到强,依次为Ⅰ类、Ⅱ类、Ⅲ类、Ⅳ类;研究区储层可分为四类,对平面非均质性控制程度由弱到强。半深湖-深湖背景下的砂质碎屑流沉积有利于形成相对高孔高渗的储层,压实作用是储层物性变差、非均质性变强的主控因素。