Sediment Oxygen Demand and Nutrient Fluxes for a Tropical Reservoir in Singapore

Sediment oxygen demand (SOD) and nutrient flux studies were conducted for a tropical reservoir in Singapore in order to determine the approximate SOD and nutrient release rates from the sediments. SOD values obtained from laboratory experiments ranged from 1.4 to 3.3?g?O2/m2-day. Similar results were also obtained by calculating SOD values from in situ DO measurements taken in the field. The nutrient flux study was performed in the laboratory at a constant temperature of 25°C in oxic and anoxic columns. Except for nitrate+nitrite, higher nutrient release rates were generally observed under anoxic conditions. The ammonium release rate was 0.06?g?O2/m2-day under oxic conditions and 0.117?g?O2/m2-day under anoxic conditions. The nitrate flux rate was 0.17?g?O2/m2-day under oxic conditions but was negligible under anoxic conditions. Orthophosphate flux results were negative throughout the oxic incubation implying that sediments acted as a sink. The release rate of orthophosphate was 0.007?6?g?O2/m2-day under anoxic conditions.     

Parsimonious Model for Combined Sewer Overflow Pollution

The reservoir concept for flow modeling has been generalized for the purpose of the parsimonious modeling of combined sewer overflow pollution. Conceptual models have been used for the buildup and washoff of pollutants on the paved surfaces, and the transport of these pollutants in the sewer system (advection, dispersion, sedimentation, and resuspension). For the parsimonious modeling of the water quality of the sewage in the effluent of the combined sewer system, the conceptual submodels of these different processes were lumped into one single model equation. When ancillary structures such as a storage sedimentation tank are present at the combined sewer overflow, the additional effect of advection, dispersion, storage, and sedimentation is considered in a similar parsimonious conceptual way. Such a parsimonious model aims to reduce the model complexity, and therefore the number of calibration parameters. In most practical cases of urban drainage modeling, water quality data are extremely limited and consequently only a small number of parameter values can be identified from the data. The proposed model is tested on the basis of 10-min and hourly concentration measurements for total suspended solids, settleable solids, biochemical oxygen demand, and ammonia at the outlet of the combined sewer system of the village of Dessel (Belgium), which were available in this case only for six overflow events.     

Evidence of High Vertical Wave-Number Behavior in a Continuously Stratified Reservoir: Boadella, Spain

High vertical wave-number modes clearly dominate the internal wave field during the stratification period in Boadella reservoir in northeast Spain. In this period, the extraction of hypolimnetic water, due to summer irrigation, brought the surface level down by 6 m in one month and the epilimnetic water progressively occupied the whole water column. The temperature profile, with the exception of a few meters at the surface layer, presented an almost constant temperature gradient of about 0.7°C/m. The period of the main vertical mode is 24 h with an amplitude of around 1 m. Thermistor chain records and meteorological data allow us to deduce that this mode is, at least, a third vertical mode forced by the wind, which normally has a typical periodicity of 24 h. However, when the wind changes direction from south to north, the circulation cells developed due to this forced nonstationary oscillation are destroyed. When this occurs, the Bulk Richardson number is Rib ～ 1. Similar vertical structures as a response to wind forcing should be expected in similar systems, although this has not been reported in the literature.     

Acid-Gas Storage in a Deep Saline Aquifer: Numerical Sensitivity Study to Evaluate Parameter and Model Uncertainty

A modeling study is conducted to evaluate the sensitivity of acid gas evolution in a deep saline aquifer to expected variations of multiple geologic and engineering variables. Relative permeability hysteresis, aquifer heterogeneity variance, formation water salinity, permeability of caprock and leakage wells, injection rate, regional hydraulic gradient, and formation depth are evaluated as uncertain input parameters to a three-dimensional synthetic aquifer model with fully heterogeneous permeability. To understand the effect of conceptual model uncertainty on predicting gas flow and storage, permeability of the heterogeneous model is upscaled to equivalent permeability for three increasingly homogenized stratigraphic models: an eight-unit facies model, a three-unit depositional model, and a one-unit formation model. Two upscaling methods are used: a flow-based numerical method and an analytical averaging method. Over 120?years (20?years of injection and 100?years of monitoring), multiphase compositional simulation is conducted to model gas migration and trapping in the aquifer and its dissolution in the formation brine. Results suggest that among the variables evaluated, gas-relative permeability hysteresis, heterogeneity variance, and injection rate have the most significant impact predicting the total mobile gas in the storage system, whereas caprock permeability is the most important factor influencing the prediction of total gas leakage and thus the storage security. Over the simulation time scale, for the fixed amount of gas injected, regional hydraulic gradient, salinity, and formation depth have lesser impact on gas flow and storage predictions. Further, leakage through abandoned wells can occur when permeability of the wellbore is as low as 1?mdarcy (md), while caprock permeability becomes critical to storage security when it is more than 1×10-4??md, in which case significant leakage occurs during the monitoring phase. Compared to the predictions of the heterogeneous model, the greater the number of stratigraphic units in the upscaled models, the better its accuracy in predicting gas storage and plume sweep. However, the accuracy of the stratigraphic models depends on aquifer variance, upscaling method, and type of prediction outcome that is being evaluated.     

Regulated rivers in the United Kingdom

This paper identifies the principal regulated rivers in Britain and summarizes their physical and ecological characteristics. Virtually all major rivers in the United Kingdom are shown to be regulated directly or indirectly by mainstream impoundments, interbasin transfers, pumped storage reservoirs, or groundwater abstractions. Flow records for sixty per cent of all gauging stations are significantly affected by flow manipulations. Three phases in the development of river regulation are identified: firstly, the development of direct supply and compensation reservoirs from 1840; secondly, the development of large dams and large-scale interbasin water transfers from 1890; and thirdly, the modern era of multipurpose river regulation that began in 1965. Any assessment of the environmental effects of river regulation must consider the spatial variation of natural river systems throughout the U.K., climatic changes, and the cumulative effect of river regulation and other impacts over an historic timescale. Today, the rivers of the U.K. are shown to have an underlying character that reflects the marked climatic, geologic, and topographic differences between the upland north and west, and lowland south and east; differences in part that relate to their different histories during the Pleistocene. However, many rivers show the effects of human impacts that began about 5000 years ago. Most rivers have experienced changes since about 1930 consequent upon afforestaton, land drainage, and channelization. These, together with short-term climatic changes, make defining ecological impacts of river regulation problematic. Pollution has had the most dramatic effects. Nevertheless, it is suggested that new concepts of environmentally sound river regulation could lead to the restoration and even enhancement of rivers in the United Kingdom.     

靖边油田曹崾岘地区延9油藏储层特征及物性研究

曹崾岘地区位于陕北靖边地区,属于鄂尔多斯盆地伊陕斜坡中部。在大量的岩心铸体薄片、X衍射、扫描电镜及物性资料统计分析的基础上,总结研究了陕北靖边油田曹崾岘地区延安组延9油藏储层特征及物性,得出结论：该地区岩石成分主要以长石质石英砂岩、长石砂岩为主。孔隙类型以原生粒间孔为主,储层物性上,延9油藏分为两个小层,延91孔、渗好于延92。     

隐蔽油气藏勘探对基准面旋回研究的启示

从基准面以及基准面旋回研究的进展出发,论述了层序界面划分的弊端,该弊端导致了基准面旋回应用于工业化生产中,带来了诸多不便.目前,我国油气勘探工作已经进入了隐蔽油气藏勘探阶段,而这种弊端更显突出.隐蔽油气藏中,洪泛面的意义尤为突出,不但控制了岩性油气藏的分布,更是控制了主力油层的分布,因而对原有的基准面旋回划分方案提出质疑.松辽盆地隐蔽油气藏勘探的结果进一步表明,在隐蔽油气藏勘探阶段,调整基准面旋回划分界限,大大提高了基准面旋回划分的可操作性,意义非常重大.     

潜江凹陷老新地区油气成藏机理与勘探潜力

在综合应用地质、地震、试油和化验分析资料基础上,根据油气成藏动力学理论对油气成藏条件和油气成藏机理进行综合分析,认为,老新地区具备形成岩性油藏和构造-岩性油藏的良好条件。油气是在高地层温度、地层压力场和势能场等主要动力作用下形成和在沉积型、构造型和复合型油气输导体系中运移。油气于荆河镇组沉积中后期聚集成藏,其空间分布具有互补性。直路口断层下降盘是隐蔽油藏勘探的最有利区。     

塔河油田碳酸盐岩缝洞型油气藏注水替油开发研究

塔河油田奥陶系碳酸盐岩缝洞型油藏非均质性强、油水分布规律差。部分高产井易水淹或产量大幅度递减。在生产实践中,发现部分单井在压井后,压力明显上升、可以恢复部分产量。分析奥陶系碳酸盐岩缝洞型油藏储层特征,研究注水开发的地质影响因素,并通过对注水替油的机理研究,结合现场单井注水替油和多井缝洞单元注水替油的实践,来分析选井、选层及注采参数的影响,评价注水替油开发效果,优化注水方案设计,是为了使注水开发在塔河碳酸盐岩油藏的推广应用,以便提高油田采收率。     

裂缝性油气藏勘探技术与应用

裂缝不仅是决定低渗透储层产能的关键因素,而且也直接控制着裂缝性油气藏的形成与分布。裂缝性储层识别与评价一直是油气藏勘探的重点和难点,而地质资料分析只是作为裂缝分布的一种定性测算,测井中的裂缝鉴定虽能达到定量水平,但只是小范围的、局部的。地震资料虽是大范围的,但其对地层的分辨率较低。因此,综合应用各种资料描述和预测裂缝分布是裂缝性油气藏勘探的基本思路。