沉积盆地热史研究综述

盆地热历史的恢复和重建,根据不同尺度,其研究方法分为构造热演化法和古温标法。其中构造热演化法是在岩石圈尺度上,对其构造演化下的热流变化进行模拟,结合盆地沉降与埋藏,恢复盆地热历史。由不同地球动力学背景差异形成的盆地类型应用不同热演化模型,拉张盆地、走滑盆地多用拉张模型来描述,前陆盆地等以挤压模型来描述。而古温标法则是利用盆内可记录古地温的有机质、矿物等进行盆地热史的重建。镜质体反射率、粘土矿物和流体包裹体等记录的是其经历的古温度峰值,利用磷灰石裂变径迹则可反演其所经历的热史路径,不同盆地条件应用不同的古温标法。     

A Regionally Applicable Model for Estimating Flow Velocity at Ungauged River Sites in the UK

Measurements of flow velocity are often required for a broad range of issues surrounding water-resource management, and a velocity-estimation method is therefore desirable where extensive field data are unavailable. This paper presents the development of a model for estimating flow velocity using readily available catchment characteristics, and flow and channel geometry data. The velocity equations were calibrated using UK data, so that their application at any river site in the UK is attainable. The calibrated equation uses the mean flow and the dimensionless magnitude of the flow on the day in question to estimate the mean reach velocity for flows at any river site in the UK.     

PETROLEUM GEOLOGY AND HYDROCARBON POTENTIAL OF THE GUBAN BASIN,NORTHERN SOMALILAND

The Guban Basin is a NW‐SE trending Mesozoic‐Tertiary rift basin located in northern Somaliland (NW Somalia) at the southern coast of the Gulf of Aden. Only seven exploration wells have been drilled in the basin, making it one of the least explored basins in the Horn of Africa – southern Arabia region. Most of these wells encountered source, reservoir and seal rocks. However, the wells were based on poorly understood subsurface geology and were located in complex structural areas. The Guban Basin is composed of a series of on‐ and offshore sub‐basins which cover areas of 100s to 1000s of sq. km and which contain more than 3000 m of sedimentary section. Seismic, gravity, well, outcrop and geochemical data are used in this study to investigate the petroleum systems in the basin. The basin contains mature source rocks with adequate levels of organic carbon together with a variety of reservoir rocks. The principal exploration play is the Mesozoic petroleum system with mature source rocks (Upper Jurassic Gahodleh and Daghani shales) and reservoirs of Upper Jurassic to Miocene age. Maturity data suggest that maximum maturity was achieved prior to Oligocene rift‐associated uplift and unroofing. Renewed charge may have commenced during post‐ Oligocene‐Miocene rifting as a result of the increased heat flows and the increased depth of burial of the Upper Jurassic source rocks in localised depocentres. The syn‐rift Oligocene‐Miocene acts as a secondary objective owing to its low maturity except possibly in localised offshore sub‐basins. Seals include various shale intervals some of which are also source rocks, and the Lower Eocene evaporites of the Taleh Anhydrite constitute an effective regional seal. Traps are provided by drag and rollover anticlines associated with tilted fault blocks. However, basaltic volcanism and trap breaching as a consequence of the Afar plume and Oligocene‐Miocene rifting of the Gulf of Aden cause considerable exploration risk in the Guban Basin.     

Future bottlenecks in international river basins: where transboundary institutions,population growth and hydrological variability intersect

Using global data, this article examines the nexus of transboundary flood events and future social vulnerability. Which international river basins are forecast to experience an increase in both hydrological variability and population in the future, but currently lack institutional provisions to deal with these shared events? Concentrations of elevated risk are found in several basins in Central Asia, Central America and Central Africa. The article ends by highlighting transboundary basins that merit further investigation and possibly additional institution building to reduce urban flood risk.     

Effect of Stilling Basin Geometry on Clear Water Scour Morphology Downstream of a Block Ramp

The scour mechanism downstream of a block ramp in clear water conditions is quite a complex phenomenon that depends on several parameters. Majors role are played by ramp configuration, hydraulic conditions (downstream tailwater level and discharge), material granulometry, and stilling basin geometry. Previous studies analyzed both the scour phenomenon and the effects of all the parameters involved except the last one (i.e., the case in which the ramp has the same width as the downstream stilling basin) and the case of symmetrically expanding stilling basins. This last basin configuration represents an optimal equilibrium between the necessity to dissipate energy and to create a natural pool for the biological species, thus it has a prominent ecological value. The present paper aims to assess the effect of both the width and length of the downstream stilling basin on scour features and flow pattern in clear water conditions. Different scour morphology types are distinguished and classified according to hydraulic and geometric conditions. Simple novel relationships are proposed to evaluate the scour depth and length and the maximum water level in the stilling basin. The results are valid for unsubmerged block ramps.     

巴西塞尔西培-阿拉戈斯盆地油气地质特征

对巴西塞尔西培-阿拉戈斯盆地的地层与沉积和石油地质等特征进行了综合研究。盆地的主要烃源岩为阿普第阶湖相高盐度灰质黑色页岩,主要油气储集层为上侏罗统粗粒河流相砂岩储层、下白垩统三角洲相与风成相砂岩、砾岩与砾质砂岩储层、上白垩统-古近系浊积砂岩储层,区域性盖层为Ibura段和Carmpolis段及上侏罗统页岩和蒸发岩,油气主要运移期和聚集期发生在渐新世及以后,同裂谷期地层的上段（地层-构造圈闭）以及裂后层系（Calumbi地层圈闭）为具备勘探潜力的有利目标段。     

Supercritical Flow over a Dentated Sill

Experimental analysis concerning supercritical flow over a dentated sill in nonsubmerged conditions and the local scour downstream of this sill is presented. In this case, the energy dissipation is incomplete so that a scour control downstream of the hydraulic structure could be required. The use of this type of dissipation device could be needed in cases where the maximum flow depth upstream of the sill must be limited to satisfy physical or structural conditions. This could happen, for instance, in the restoration of stilling basin in gravity dams and at the outlet of diversion systems. Experimental and theoretical results, useful in the design of this type of stilling basin and scour control, are presented in the paper, with an application to the case of the Molato Dam in Italy.     

Regionalisation of impervious area parameters of urban drainage models

Stormwater drainage models are increasingly being used in design and analysis of urban drainage systems. If these models are to be used for ungauged drainage systems for which no storm and corresponding flow data are available, then the model parameters have to be estimated through regional equations. These regional equations define the model parameters via measurable catchment properties. In this study, regional equations of two impervious area parameters, namely directly connected impervious area percentage (DCIA) and its depression storage (DS_i ), were developed for use in urban drainage models, using 15 gauged urban catchments in Melbourne Metropolitan area (Australia). The ‘small’ storm events of these gauged catchments were first used to calibrate the impervious area parameters, since the ‘small’ storm events produce runoff only from the impervious areas. These calibrated impervious area model parameters were then analysed with several measurable catchment properties to derive the regional equations. The results of the study revealed that DCIA was depended only on household density of the catchment, while DS_i was not correlated with any of the catchment properties analysed.     

PREDICTING ECOLOGICAL FLOW REGIME AT UNGAGED SITES: A COMPARISON OF METHODS

Nineteen ecologically relevant streamflow characteristics were estimated using published rainfall–runoff and regional regression models for six sites with observed daily streamflow records in Kentucky. The regional regression model produced median estimates closer to the observed median for all but two characteristics. The variability of predictions from both models was generally less than the observed variability. The variability of the predictions from the rainfall–runoff model was greater than that from the regional regression model for all but three characteristics. Eight characteristics predicted by the rainfall–runoff model display positive or negative bias across all six sites; biases are not as pronounced for the regional regression model. Results suggest that a rainfall–runoff model calibrated on a single characteristic is less likely to perform well as a predictor of a range of other characteristics (flow regime) when compared with a regional regression model calibrated individually on multiple characteristics used to represent the flow regime. Poor model performance may misrepresent hydrologic conditions, potentially distorting the perceived risk of ecological degradation. Without prior selection of streamflow characteristics, targeted calibration, and error quantification, the widespread application of general hydrologic models to ecological flow studies is problematic. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.