The relative effects of deformation and thermal advection on fluid pathways in basin-related mineralization     

John G. McLellan  Nicholas H.S. Oliver  Bruce E. Hobbs 《Journal of Geochemical Exploration》2006,89(1-3):271

The migration of basinal brines into basement material has been proposed as a means of scouring or leaching metals for subsequent ore deposition. Here we address this issue by numerically examining competing processes, namely deformation, fluid flow and thermal gradients, to describe potential fluid pathways leading to enrichment of metals and ore deposition. Stable convective fluid patterns may be established across the cover/basement interfaces if permeability contrasts are minimized, however, at the onset of extensional deformation these convective patterns quickly collapse. On cessation of the deformation, convection cells again develop, which are oscillatory with time. Input to the thermal budget from a radiogenic heat source suggests that basinal fluids can be drawn down around the margins of granite intrusions and fluid mixing processes may take place due to small and localised convective patterns. Fluid migration from basin into basement and back is highly likely given the right conditions, however, the rate and extent of fluid flow are determined by thermal and deformation processes.  相似文献   

MAST solution of advection problems in irrotational flow fields     

Costanza Aricò  Tullio Tucciarelli 《Advances in water resources》2007

A new numerical–analytical Eulerian procedure is proposed for the solution of convection-dominated problems in the case of existing scalar potential of the flow field. The methodology is based on the conservation inside each computational elements of the 0th and 1st order effective spatial moments of the advected variable. This leads to a set of small ODE systems solved sequentially, one element after the other over all the computational domain, according to a MArching in Space and Time technique. The proposed procedure shows the following advantages: (1) it guarantees the local and global mass balance; (2) it is unconditionally stable with respect to the Courant number, (3) the solution in each cell needs information only from the upstream cells and does not require wider and wider stencils as in most of the recently proposed higher-order methods; (4) it provides a monotone solution. Several 1D and 2D numerical test have been performed and results have been compared with analytical solutions, as well as with results provided by other recent numerical methods.  相似文献   

不同边界层参数化方案对江苏地区一次平流雾过程的模拟影响   总被引：4，自引：1，他引：3  

崔驰潇  包云轩  袁成松  周林义  焦圣明  宗晨 《大气科学》2018,42(6):1344-1362

边界层参数化方案的选取在平流雾的预报准确度上起着决定性的作用。本文利用WRF模式对2013年3月18~19日发生在江苏地区的一次平流雾过程进行数值模拟试验,对耦合不同闭合方式边界层参数化方案的试验结果与实测气象数据进行对比分析,评估了他们对此次平流雾的模拟效果,探讨了边界层高度对此次平流雾的生成和发展的影响。研究结果表明:（1）耦合不同边界层方案的WRF模式对地面气象要素的模拟结果均呈现气温偏低、湿度和风速偏大的特征。（2）QNSE方案对气温的模拟能力最强;ACM2方案对相对湿度的模拟性能最好;YSU方案对风速的模拟效果最佳。不同边界层方案的模拟结果在垂直方向上的差别主要表现在低空相对湿度上:QNSE方案预报的湿度更大。（3）综合TS（Threat Score）和BS（Bias Score）两个评分指标来看,ACM2方案对雾区分布的模拟效果最好。三个边界层方案对此次平流雾的模拟结果在江苏沿海站点的预报评分较高,在距海较远站点的预报评分表现较差。YSU方案对东南沿海地区的雾区预报评分较高;QNSE方案对长江沿江区域的雾区预报评分较高;ACM2方案对沿海地区、尤其对沿海北部地区的有较好的预报效果。（4）QNSE方案对此次平流雾的生成时间、出现地点预报比较准确。（5）平流雾的生成与发展阶段模拟雾区覆盖范围与边界层高度关系十分紧密,适当强度的湍流混合作用有助于平流雾在地面的生成与发展;但是过强的湍流混合作用会导致大雾过早的消散。  相似文献   

Models of heat transport in the Central European Basin System: Effective mechanisms at different scales     

《Marine and Petroleum Geology》2014

Understanding heat transport in sedimentary basins requires an assessment of the regional 3D heat distribution and of the main physical mechanisms responsible for the transport of heat. We review results from different 3D numerical simulations of heat transport based on 3D basin models of the Central European Basin System (CEBS). Therefore we compare differently detailed 3D structural models of the area, previously published individually, to assess the influence of (1) different configurations of the deeper lithosphere, (2) the mechanism of heat transport considered and (3) large faults dissecting the sedimentary succession on the resulting thermal field and groundwater flow. Based on this comparison we propose a modelling strategy linking the regional and lithosphere-scale to the sub-basin and basin-fill scale and appropriately considering the effective heat transport processes. We find that conduction as the dominant mechanism of heat transport in sedimentary basins is controlled by the distribution of thermal conductivities, compositional and thickness variations of both the conductive and radiogenic crystalline crust as well as the insulating sediments and by variations in the depth to the thermal lithosphere–asthenosphere boundary. Variations of these factors cause thermal anomalies of specific wavelength and must be accounted for in regional thermal studies. In addition advective heat transport also exerts control on the thermal field on the regional scale. In contrast, convective heat transport and heat transport along faults is only locally important and needs to be considered for exploration on the reservoir scale.The general applicability of the proposed workflow makes it of interest for a broad range of application in geosciences including oil and gas exploration, geothermal utilization or carbon capture and sequestration issues.  相似文献   

Chlorine transport processes through a 2000 m aquifer/aquitard system     

《Marine and Petroleum Geology》2014

In the Paris Basin, in France, the Callovo-Oxfordian (COx) is currently studied over a 250 km² surface area by the French national radioactive waste management agency in order to assess the feasibility of long-term underground nuclear waste repository. The COx is a 140 m thick clay-rich layer, which is part of the 2000 m aquitard/aquifer system constituting the sedimentary cover. In such sedimentary context, the transport processes of potential contaminants can be represented by both vertical diffusion and horizontal advection through the most permeable layers.Chloride is used as a natural conservative tracer, and is monitored in term of concentrations and isotopic composition (δ³⁷Cl) for both pore and groundwater. During this study, the samples were collected from three boreholes located in the center of the studied zone, one of them (EST433) going down to 2000 m depth. The main solute transport process is shown to be vertical diffusion from the massive Keuper halite level to the rest of the sedimentary pile. This global diffusive system can be occasionally disturbed by horizontal circulation of groundwater occurring in the Oxfordian and Dogger limestone formations. Therefore, these circulations cut the global diffusive system in a succession of independent diffusive systems. In this study the data set was implemented in a simplified 2D solute transport model and scenarii reproducing known history in term of paleo circulations inside the system, were applied and allowed to obtained a good fit of the data. Model results showed that paleo circulations, occurring between −145 Ma and −110 Ma, still have an impact on current distribution of chloride in the system, especially for δ³⁷Cl. The model highlights the need of the presence of a circulation spatially limited at the base of the Liassic formation to fit the data. The best fit obtained indicated current residence time of 500 ka in the Dogger and Oxfordian, with respective onset of the circulations at −20 Ma and −5 Ma.  相似文献   

北京一次持续性雾、霾的特征和成因分析     

赵娜  尹志聪  吴方 《气象与环境学报》2014,30(5):15-20

基于2013年1月9-15日北京地区一次持续雾、霾过程,对环流形势、要素、物理量场以及污染监测情况进行分析。结果表明：高PM_2.5和SO₂事件持续时间超过100 h,浓度达到严重污染级别。高空为偏西或西南气流且850 hPa有弱暖平流输送和地面倒槽维持少动是有利于雾、霾持续的背景条件。持续轻雾或霾对湿层厚度要求不高,在925 hPa下即可,且湿层越厚,能见度越低。逆温维持是雾、霾持续的主要原因,且轻雾或霾为主时逆温层特点为厚度浅强度弱,高度或强度的突然增大可预示向大雾或雪转换; 850 hPa以下涡度平流较弱是轻雾或霾持续的动力结构;总温度平流垂直分布表现为闭合中心强度在500 hPa明显分界,且相对较弱的平流中心的高度一般在850-1000 hPa之间,当高度达到500 hPa时或可预示雾、霾天气消散。  相似文献   

Nonlocal and localized analyses of nonreactive solute transport in bounded randomly heterogeneous porous media: Computational analysis     

Eric Morales-Casique  Shlomo P. Neuman  Alberto Guadagnini 《Advances in water resources》2006

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