Nearshore intertidal topography and topographic-forcing mechanisms of an Amazon-derived mud bank in French Guiana

The intertidal topography in the vicinity of the contact zone between a longshore-migrating Amazon-derived mud bank and the muddy terrestrial shoreline in French Guiana was defined from a combination of satellite-based SPOT images, airborne lidar data and high-resolution total station ground surveying of a 75,000 m² plot. The three approaches, at different scales, were carried out at different periods. Digital elevation models generated from these three techniques, however, converge in highlighting the topographic micro-scale (centimetre-scale) variability of the mud bank surface while showing meso- to macro-scale features that reflect the dominance of wave activity in mud bank mobilization and attachment to the terrestrial shoreline. These features are bar-like longshore forms that develop in the intertidal zone from the shoreward drift of gel-like mud that accompanies wave damping. The features progressively become consolidated through mud drying out associated with the formation of cracks that are important in mangrove colonization and ecological changes. Fluid-mud accumulations formed from high concentrations of mud trapped in the troughs behind these linear bar forms generate flat featureless surfaces that tend to mask topographic heterogeneity of the mud bank surface. Dewatering of these lower zones by progressive mud consolidation complements tidal water discharge in providing a mechanism for the formation of the numerous channels that dissect the linear bar features, especially in the upper intertidal contact zone with the terrestrial shoreline. This dissection in the upper intertidal zone generates an intricate topography that replaces the original linear bar forms. The innermost bar forms a ‘suture’ zone with the terrestrial shoreline. Reworking of this bar by high-energy waves may lead to mud dispersal over old terrestrial mangrove substrates, resulting in stifling of mangrove pneumatophores. Mud reworking at the narrow trailing edge of the mud bank in the subtidal and lower intertidal zones leaves behind a flat bed that will eventually be completely eroded by waves in the course of mud bank migration.     

TOWARDS A BETTER FORECAST FOR RESERVOIR SLOPE SLIDING

The siltation of reservoir causes many problems of management and environmental disturbances that are important to minimize. Solving these problems requires in particular a good knowledge of mud bank instabilities. In partnership with the Laboratoire National d'Hydraulique (LNH), a subsidiary of Electricite de France (E.D.F.), authors realize a study of soft soils sliding entailed by reservoir emptying. Using a geotechnical flat sliding mechanism, the theoretical formulation of the safety factor can be established when the sediment mass is submerged and emergent. The measurement campaign carried out makes it possible to obtain bathymetric and topographic surveys and a geotechnical characterization of the soil for the whole reservoir of Grangent dam, located on the Loire (France). The proposed model appears to agree satisfactorily with the instability of the zones emerged because of the emptying and with the stability of the profile after emptying. The use of this model within the framework of forecasts     

滆湖底质特性对菹草(Potamogeton crispus)和伊乐藻(Elodeanattalii)生长的影响

通过模拟试验,研究滆湖3种沉积物(表层湖泥、硬底湖泥、表层覆岸泥)对菹草和伊乐藻生长的影响.结果表明,生长于表层湖泥、硬底湖泥、表层覆岸泥的菹草和伊乐藻生物量分别为4.07、1.98、3.69kg/m2和1.86、1.27、1.74kg/m2,表层湖泥较适合这两种沉水植物生长.3种沉积物对菹草和伊乐藻的干湿比影响显著,...     

利用阵列感应测井进行储层渗透率评价

钻井过程中储层受到泥浆侵入影响的程度与储层岩性有着密切关系,其中储层渗透率对侵入深度有着较大影响,因此若可以获知泥浆侵入深度,则有望对储层渗透率进行评估.本文首先建立含泥饼增长的泥浆侵入数值模型,然后建立阵列感应测井数值模型,两者的联合正演模拟显示泥浆侵入对地层的影响可以反映在阵列感应测井响应上,利用阻尼最小二乘法对阵列感应测井响应进行反演可以得到侵入深度.对侵入深度和储层渗透率的关系进行分析发现:在渗透率为1～100mD(1mD=0.987×10~(-3)μm～2)数量级的储层中,渗透率的变化可以在侵入深度上得到反映.以储层和井数据进行二维数值模拟发现:利用阵列感应测井响应反演出来的侵入深度曲线反映了渗透率在地层上的变化趋势,采用解释图版的方法可以对储层各层段的渗透率进行粗略估算.     

Short‐term changes in the plan shape of a sandy beach in response to sheltering by a nearshore mud bank,Cayenne, French Guiana

Montjoly is a headland‐bound embayed sandy beach in Cayenne, French Guiana, that shows long‐term plan shape equilibrium in spite of periodic changes in accretion and erosion that alternately affect either end of the beach. These changes are caused by mud banks that move alongshore from the Amazon. The mechanisms involved in changes in the plan shape of the beach in response to the passage of one of these mud banks were monitored between 1997 and 2000 from airborne video imagery and field work. The beach longshore drift to the northwest, driven by the incident easterly to northeasterly swell usually affecting this coast, became temporarily reversed as the mud bank, migrating from east to west, initially sheltered the southeastern end of the beach. The difference in exposure to waves engendered a negative wave height gradient alongshore towards the southeast, resulting in the setting up of a cell circulation and counter‐active longshore drift from the exposed northwestern sector to the southeast. Sand eroded from the exposed sector accumulated first in the southeastern, and then the central sectors of the beach. The effect of increasing beach sheltering by the mudbank moving west is highlighted on the videographs by an ‘arrested’ pattern of beach shoreline development. The videographs show hardly any changes in beach plan shape since January 1999, due to sheltering of the beach from wave attack by the mud bank. It is expected that the eroded sector will recover in the future as the mud bank passes, leading to re‐establishment of the northwesterly sand drift. This temporally phased bi‐directional drift within the confines of the bounding headlands results in a rare example of mud‐bank‐induced beach rotation, and probably explains the long‐term equilibrium plan shape of Montjoly beach. Copyright © 2002 John Wiley & Sons, Ltd.     

Bank permeability in an Australian ephemeral dry‐land stream: variation with stage resulting from mud deposition and sediment clogging

Percolation of flood waters into the bed and banks of ephemeral streams provides one of the key mechanisms responsible for transmission loss. However, there are very few published estimates of the rates at which water can enter stream‐bank sediments, and little is known about the variation in bank permeability with elevation above the bed and the resulting effects on transmission loss in floods of different magnitudes. This paper presents the results of 69 field determinations of bank infiltrability made on Fowlers Creek, an ephemeral dry‐land stream located in arid western New South Wales, Australia. Fowlers Creek carries high concentrations of suspended sediments, which are deposited as mud drapes on the bed, banks and floodplain. Results demonstrate that infiltration rates are lowest at the base of the banks, and tend to increase steadily with elevation on the bank, even above the apparent upper limit of mud drapes. In parallel, the texture of the bank sediments (assessed from samples of the uppermost 10 cm) becomes coarser with elevation above the bed. This pattern is inferred to relate to the delivery of silts and clays into pore spaces in the bank sediments by percolating flood waters. The patterns of infiltration rate and sediment texture mapped in the field are reasoned to be the product of many clogging episodes in past flood events having different peak stages. The increase in infiltration rate and mean particle size up the banks reflects lower frequencies of submergence and clogging of the upper banks by large floods, and more frequent inundation and clogging of the lower banks by sub‐bank‐full flows. The stage‐related changes in bank permeability provide a mechanism that can drive variations in transmission loss among floods having different peak stages and hydrograph shapes. Copyright © 2007 John Wiley & Sons, Ltd.     

水库诱生的孔压变化及应力特征

应用“固结问题和布辛涅斯克问题解”,计算了丹江水库水位在130m和157m两种情况下,库区基岩体深度分别为1、3、5、7、9、11、13和15km时的水压应力场、变形场和超孔隙水压力场。结果表明,σ_1、σ_3和τ_(max)在库中心位置最大,库岸边较小;同时σ_1和σ_3在库中心均显压性,而在库岸边σ_3显张性;垂直位移在库中心最大(7cm),而水平位移在库岸边最大(0.5cm);超孔隙水压力一般在库中心深水区库基下3—9km处最大,库岸边和浅水区较小;体应变一般在库中心位置形成压缩区,而在库岸边则形成拉伸应变区并同时向四周扩展,与诱发地震震中分布相一致。     

斜井泥浆侵入仿真及其阵列侧向测井响应数值模拟

为了研究斜井泥浆侵入储层的井周岩石物理特征,采用广义曲线坐标系统模拟斜井泥浆侵入特性,进而研究泥浆侵入过程的阵列侧向测井响应.数值仿真表明,采用广义曲线坐标系消除了笛卡儿坐标系统在斜井边界处网格划分的锯齿现象;储层非均质造成泥浆侵入不均匀,储层渗透性越好,泥浆滤液侵入越深;泥浆滤液侵入使得井周地层饱和度、孔隙水矿化度的分布发生变化,进而造成斜井井周岩石电阻率分布剖面复杂变化;泥浆侵入过程中阵列侧向视电阻率变化以及深浅视电阻率的幅度差异,有效反映了斜井泥浆侵入特性;文中采用了基于Marquardt方法的阵列侧向测井四参数反演,有效恢复了斜井储层侵入剖面,得到了原状地层电阻率.斜井泥浆侵入特征及其阵列侧向测井响应模拟分析,有助于正确认识斜井井周岩石物理特征和利用阵列侧向测井进行斜井储层评价.     

Application of Multiboost-KELM algorithm to alleviate the collinearity of log curves for evaluating the abundance of organic matter in marine mud shale reservoirs: a case study in Sichuan Basin,China

The total organic carbon (TOC) content reflects the abundance of organic matter in marine mud shale reservoirs and reveals the hydrocarbon potential of the reservoir. Traditional TOC calculation methods based on statistical and machine learning have limited effect in improving the computational accuracy of marine mud shale reservoirs. In this study, the collinearity between log curves of marine mud shale reservoirs was revealed for the first time, which was found to be adverse to the improvement of TOC calculation accuracy. To this end, a new TOC prediction method was proposed based on Multiboost-Kernel extreme learning machine (Multiboost-KELM) bridging geostatistics and machine learning technique. The proposed method not only has good data mining ability, generalization ability and sound adaptivity to small samples, but also has the ability to improve the computational accuracy by reducing the effect of collinearity between logging curves. In prediction of two mud shale reservoirs of Sichuan basin with proposed model, the results showed that the predicted value of TOC was in good consistence with the measured value. The root-mean-square error of TOC predicting results was reduced from 0.415 (back-propagation neural networks) to 0.203 and 1.117 (back-propagation neural networks) to 0.357, respectively; the relative error value decreased by up to 8.9%. The Multiboost-KELM algorithm proposed in this paper can effectively improve the prediction accuracy of TOC in marine mud shale reservoir.     

EROSION OF BANKS OF STORAGE RESERVOIRS IN POLAND

ABSTRACT

The abrasion of banks of certain storage reservoirs can have considerable importance. Cases are known where the shift of the bank line forecast to take place within a period of ten or fifteen years was exceeded during the first year of operation of the reservoir. However, transformation and erosion of banks in other reservoirs or other bank sections, although anticipated, either has not occurred, or, when it did, its intensity was much lower than expected. This is why the problem of transformation of the near-shore zone in reservoirs is attracting more and more attention from many scientific institutes.

The paper presents the subject, methods and results of research on the transformation and erosion of the reservoir banks. The main effort has been concentrated on trying to establish the relationships between geological-morphological and climatic-hydrological conditions. It has been stated that the dynamic potential of the reservoir is of decisive importance. This potential, depending on the morphometry of the reservoir and the meteorological conditions (mainly wind) exerts an influence on the reservoir shore line. Consequently, the erosive-accumulation processes become interrelated, resulting in transformation of the bank zone and its adaptation to new conditions.     

Application of back-propagation neural network on bank destruction forecasting for accumulative landslides in the three Gorges Reservoir Region,China

In recent years, a large number of bank destruction occur in the reservoir area under the effect of water fluctuation, which may be lead to reservoir accumulative landslide geological hazards finally. The paper conducted the bank destruction forecasting study for accumulative landslides in the Three Gorges Reservoir Region, China utilizing back-propagation (BP) neural network approach. A representative scenario of Jinle landslide is then taken for analysis purposes. On the basis of the existing data sets of bank destruction cases, the BP neural network forecasting model and the corresponding programs for bank destruction are both presented, whose forecasting result is validated by two independent approaches, namely empirical method and numerical modeling method. Furthermore, the BP neural network model had obvious advantages over the convention approaches in the aspects of the fast calculation speed and high convenience. According to the bank destruction forecasting scale presented above, the corresponding revetment measures can be proposed to prevent the occurring of the bank destruction, whose effectiveness has been further validated by the actual engineering practice.     

Distribution and transportation of nitrogen in Miyun reservoir waters

The Miyun reservoir is an important water supply for Beijing city. The distribution laws of nitrogen in the Miyun reservoir waters and the transportation factors have been systematically analyzed in space and time by using water monitoring data sampled in the high-water and low-flow periods in 2001 and 2002. The nitrogen in east and west reservoir waters is distributed differently in space. It shows the change characteristics in high-water and low-flow periods and is affected by the source of nitrogen, runoff conditions, hydrodynamic conditions, precipitation and the control of bed mud, of which the source of nitrogen controls the change of concentration of nitrogen, the peripheral runoff controls the distribution law of nitrogen, bed mud controls the vertical distribution of nitrogen, and the contents of nitrogen and its change in the surrounding environment directly cause the change of concentration of total nitrogen in the waters. The improvement and protection of the waters in the Miyun reservoir basically rests with the amelioration of the peripheral environment.     

Mud bank colonization by opportunistic mangroves: A case study from French Guiana using lidar data

Mud bank colonization by mangroves on the Amazon-influenced coast of French Guiana was studied using light detection and ranging (lidar) data which provide unique information on canopy geometry an sub-canopy topography. The role of topography was assessed through analysis of vegetation characteristics derived from these data. Measurements and analyses of mangrove expansion rates over space and time led to the identification of two distinct colonization processes. The first involves regular step-by-step mangrove expansion to the northwest of the experimental site. The second is qualified as ‘opportunistic’ since it involves a clear relationship between specific ecological characteristics of pioneer Avicennia and mud cracks affecting the mud bank surface and for which probabilities of occurrence were computed from terrain elevations. It is argued from an original analysis of the latter relationship that mud cracks cannot be solely viewed as water stress features that reflect desiccation potentially harmful to plant growth. Indeed, our results tend to demonstrate that they significantly enhance the propensity for mangroves to anchor and take root, thus leading to the colonization of tens of hectares in a few days. The limits and potential of lidar data are discussed with reference to the study of muddy coasts. Finally, the findings of the study are reconsidered within the context of a better understanding of both topography and vegetation characteristics on mangrove-fringed muddy coasts.     

Temporal variations of reservoir sediment sources in a small mountainous catchment in Korea

An understanding of the temporal variation in reservoir sedimentation and identification of the main sources of sediment are necessary for the maintenance of sustainable reservoirs. For this purpose, field measurements, sampling, and fingerprinting of reservoir sediment were undertaken from July 2005 to November 2007. Source fingerprinting of reservoir sediment was conducted using cesium‐137 (¹³⁷Cs). The relative contributions of gully bank and forest road, and forest floor material to reservoir sediment were calculated using a mixing model. Bank and forest road material, estimated to make up about 96% of the reservoir sediment, was the dominant source. Enormous reservoir sedimentation, which amounted to about 60% of the total reservoir sedimentation during the observation period, occurred during a heavy rainstorm with an 80‐year recurrence time. To maintain the sustainability of the reservoir in this study, therefore, temporal and spatial preparation strategies for heavy rainstorms and bank and forest road erosion should be considered. However, spatial information on sediment sources from ¹³⁷Cs fingerprinting is limited. To better identify the sediment sources spatially and temporally, further studies applying soil erosion models and more detailed field studies are needed. Copyright © 2013 John Wiley & Sons, Ltd.     

THE FLUID GEOCHEMICAL VARIATION CHARACTERISTICS OF THE WUSU MUD VOLCANOES BEFORE THE JINGHE EARTHQUAKE OF MS6.6 ON AUGUST 9, 2017

Mud volcano is a conical sedimentary body formed by high-pressure mud and gas-dominated fluid migrated to the surface through faults and other channels deep underground, which looks like a volcanic cone formed by magma-volcanism. As a product of crustal movement, mud volcano can bring a large amount of valuable information from deep to the surface when erupting. Therefore, mud volcano is called "god-given borehole" with a depth of 7~12km. Mud volcanoes are the result of upthrust of trapped gases released by the pressure in the stratum and also the channel for the upward migration of gases in the earth. The submarine mud volcano is one of the signs of hydrate and the living evidence of hydrate. The Wusu mud volcanoes are located in the northern Tianshan tectonic belt. Since the mud volcamoes locate in the active part of the tectonic belt and are well connected to the underground, their active degree has a good correlation with the seismicity. The earthquake cases studies based on the 7a long real-time macroscopic monitoring data and the more than 3a long geochemical monitoring data of the Wusu mud volcanoes show that in the earthquake cases of M_S ≥ 5.0 within the range of 300km around the Wusu mud volcanoes, the abnormal mud gushing quantity obviously increased by macroscopic monitoring before 9 out of 13 earthquakes. The geochemical microcosmic monitoring data showed obvious abnormal changes before 3 out of 6 earthquakes. The anomalous duration from the emergence of the anomaly to the occurrence of the earthquake is mainly of the mid-term(6~12 months). Before the Jinghe M_S6.6 earthquake on August 9, 2017, the Wusu mud volcanoes spewed violently and the chemical components showed an obvious high value anomaly. In January 2017, there was a significant increase in the amount of mud spewing in Aiqigou No.1mud volcano and Baiyanggou No.1mud volcano, and one month before the earthquake, there was the phenomenon that mud gushing amount of Aiqigou No.2 mud volcano gradually increased and the volcano was from dormant to active. There were obvious high values appearing before the earthquake in F^-and SO₄^2- in the Aiqigou No.1mud volcano and in F^-, CO₃^2-, SO₄^2-, Rn(gas), CH₄, Ar and N₂ in Baiyanggou(No.1 and 2)mud volcanoes. The values of F^-, CO₃^2-, SO₄^2-, Ar and N₂ showed short-term anomalies, while CH₄ and Rn(gas)showed medium term anomalies. Giggenbach triangular diagram (Na-K-Mg) indicates that the water-rock reaction of Baiyanggou mud volcanoes is complete and little disturbed by the outside. The water-rock reaction of the Aiqigou mud volcanoes is still ongoing, which can explain why the precursor anomaly of the chemical components of the Baiyanggou mud volcanoes is more obvious than that of the Aiqigou mud volcanoes. The geothermal reservoir temperature of the study area is estimated by using a cationic (Na-K, K-Mg, Na-K-Ca) geothermometer. The geothermal reservoir temperature of the Wusu mud volcanoes is about 70℃, and the circulation depth is about 3km. In the process of earthquake preparation, the mud carries deep chemical components to the ground surface due to the effect of compression stress(the result of focal mechanism)or the concentration of regional tectonic stress with earthquake preparation; Or the rock strata in or near the seismogenic area are deformed, the depth of liquid circulation will increase, and the water-rock reaction will be accelerated, which will increase the concentration of some ionic components, and the squeezing process will cause a large number of mud to gush out of the ground, carrying geochemical components. Therefore, the gushing quantity and some chemical components of the mud volcanoes were obviously abnormal before the earthquake.     

孔隙结构对储层电性及测井解释评价的影响（英文）

在多个区块的测井评价工作发现,孔隙结构直接影响储集层的品质和油气层的电阻率,是测井准确评价流体性质的关键。岩石物理资料表明不同区块内影响储层孔隙结构的因素不同,但效果是一致的,即孔隙结构的复杂程度控制着储层的储集能力和渗透能力。孔隙结构的复杂程度影响了储层中导电流体的分布和含量,从而控制了储层的电阻率。储层出现低阻油气层的内因均为复杂的孔隙结构（骨架导电及工程原因除外）。测井储层评价在分析控制储层孔隙结构复杂程度的地质因素及储层分类的基础上,针对不同类型储层采用不同的模型、参数和标准,可以有效的认识储层品质和识别不同类型储层的流体性质。     

Radiological aspects of red mud disaster in Hungary

One of the most severe industrial catastrophes happened in Kolontár, Hungary, on 4 October 2010. Red mud (bauxite residue) broke through the eroded wall of the red mud reservoir pond “Number X” and flooded the surrounding area. This led to the instant death of 10 people and the injury of more than 100 people. Red mud is enriched in radium and thorium isotopes; therefore, there is a chance that this flooding will increase radionuclide concentrations of soils and also in air. In this study we have examined the site to assess the realistic radiological risks. For the risk assessment the following parameters were determined: gamma dose rate, radon concentration, radionuclide concentration of red mud and air dust concentration. It was found that the radiation dose exposure resulting from red mud contamination was < 0.045 mSv y^?1 (excluding radon), which can be considered negligible when compared to the average annual effective dose from natural sources (2.4 mSv y^?1).     

Main models and distribution patterns of gas reservoirs in large-medium gas fields of China

Based on characteristics and trap types of gas reservoirs in large and medium gas fields in China, 4 gas reservoir models have been established:(i) structural trap gas reservoir model I, formed earlier than or simutaneously with generating of gases; (ii) structural trap gas reservoir model II, formed later than generating of gases; (iii) fossil weathered residuum gas reservoir model; and (iV) mud diapir abnormal temperature and pressure gas reservoir model. Distribution patterns of large-medium gas fields are described with the concept of “sealed compartment”. It is concluded that the inner-compartment area, marginal area of the compartment and the areas between two overlapped sealed compartments are the most favourable areas for discovering large-medium gas fields. Project supported by the “85–102” Chinese National Key Science and Technology Project.     

Concave-bank benches and associated floodplain formation

This paper describes the morphology, sequential development and general sedimentology of concave-bank benches on the Murrumbidgee River of southeastern Australia, and also notes their important role in floodplain formation on certain meandering rivers in western Canada. Benches form against the concave bank (cut-bank) of abruptly curving bends immediately upstream of the point of maximum curvature. As a result of flow deflection against the upstream limb of the convex bank, the channel widens here and produces a zone of expanded flow facilitating flow separation near the upstream limb of the concave bank. Sedimentation within this zone starts with a longitudinal-shaped bar of medium sand forming a platform isolated even at low flow by a narrow secondary channel against the concave bank. Aggradation of the longitudinal-shaped bar with fine sand, mud and organic matter permits the establishment of trees. Further sedimentation, particularly around the young trees, results in the formation of a fully developed bench isolated by the secondary channel from the remainder of the floodplain only during high flows. Observations on confined meandering rivers in western Canada provide evidence of substantial floodplain formation by concave-bank bench accretion, a process distinctly different in character to the more familiar mechanism of lateral point-bar accretion. Furthermore, the preservation of abundant organic debris means that extensive bench deposits may be a source of locally useful natural gas from within floodplain sediments.