Calculation of Well Index for Nonconventional Wells on Arbitrary Grids     

Christian Wolfsteiner  Louis J. Durlofsky  Khalid Aziz 《Computational Geosciences》2003,7(1):61-82

Wells are seldom modeled explicitly in large scale finite difference reservoir simulations. Instead, the well is coupled to the reservoir through the use of a well index, which relates wellbore flow rate and pressure to grid block quantities. The use of an accurate well index is essential for the detailed modeling of nonconventional wells; i.e., wells with an arbitrary trajectory or multiple branches. The determination of a well index for such problems is complicated, particularly when the simulation grid is irregular or unstructured. In this work, a general framework for the calculation of accurate well indices for general nonconventional wells on arbitrary grids is presented and applied. The method entails the use of an accurate semianalytical well model based on Green's functions as a reference single phase flow solution. This result is coupled with a finite difference calculation to provide an accurate well index for each grid block containing a well segment. The method is demonstrated on a number of homogeneous example cases involving deviated, horizontal and multilateral wells oriented skew to the grid. Both Cartesian and globally unstructured multiblock grids are considered. In all these cases, the method is shown to provide results that are considerably more accurate compared to results using standard procedures. The method is also applied to heterogeneous problems involving horizontal wells, where it is shown to be capable of approximating the effects of subgrid heterogeneity in coarse finite difference models.  相似文献   

Eutrophication and some European waters of restricted exchange   总被引：1，自引：0，他引：1  

Paul Tett  Linda Gilpin  Harald Svendsen  Carina P. Erlandsson  Ulf Larsson  Susanne Kratzer  Eric Fouilland  Carol Janzen  Jae-Young Lee  Christian Grenz  Alice Newton  Joo Gomes Ferreira  Teresa Fernandes  Serge Scory 《Continental Shelf Research》2003,23(17-19):1635

Regions of Restricted Exchange (RREs) are an important feature of the European coastline. They are historically preferred sites for human settlement and aquaculture and their ecosystems, and consequent human use, may be at risk from eutrophication. The OAERRE project (EVK3-CT1999-0002) concerns ‘Oceanographic Applications to Eutrophication in Regions of Restricted Exchange’. It began in July 2000, and studies six sites. Four of these sites are fjords: Kongsfjorden (west coast of Spitzbergen); Gullmaren (Skagerrak coast of Sweden); Himmerfjärden (Baltic coast of Sweden); and the Firth of Clyde (west coast of Scotland). Two are bays sheltered by sand bars: Golfe de Fos (French Mediterranean); and Ria Formosa (Portuguese Algarve). Together they exemplify a range of hydrographic and enrichment conditions. The project aims to understand the physical, biogeochemical and biological processes, and their interactions, that determine the trophic status of these coastal marine RRE through the development of simple screening models to define, predict and assess eutrophication. This paper introduces the sites and describes the component parts of a basic screening model and its application to each site using historical data. The model forms the starting point for the OAERRE project and views an RRE as a well-mixed box, exchanging with the sea at a daily rate E determined by physical processes, and converting nutrient to phytoplankton chlorophyll at a fixed yield q. It thus uses nutrient levels to estimate maximum biomass; these preliminary results are discussed in relation to objective criteria used to assess trophic status. The influence of factors such as grazing and vertical mixing on key parameters in the screening model are further studied using simulations of a complex ‘research’ model for the Firth of Clyde. The future development of screening models in general and within OAERRE in particular is discussed. In addition, the paper looks ahead with a broad discussion of progress in the scientific understanding of eutrophication and the legal and socio-economic issues that need to be taken into account in managing the trophic status of RREs.  相似文献   

Snow Mass Quantification and Avalanche Victim Search by Ground Penetrating Radar     

Christian Jaedicke 《Surveys in Geophysics》2003,24(5-6):431-445

Ground penetrating radar (GPR) systems can be used in many applications of snow and ice research. The information from the GPR is used to identify and interpret layers, objects and different structures in the snow. A commercially available GPR system was further developed to work in the rough environment of snow and ice. The applied GPR is a 900 MHz system that easily reaches snow depths of up to 10 meters. The system was calibrated in the course of several manual snow depth measurements during each survey. The depth resolution depends on the snow type and is around ±0.1 m. The GPR system is carried alongside a line of interest and is triggered by an odometer wheel at regular adjustable steps. All equipment is mounted in a sledge and is pulled by a snowmobile over the snow surface. This setup allows for an efficient coverage of several kilometers of terrain profiles. The radar profiles give a real time two-dimensional impression of structures and objects and the interface between snow and the underlying ground. The actual radar profile is shown on a screen on the sledge allowing the immediate marking of objects and structures. During the past three years the instrument was successfully used for the study of snow distributions, for the detection of glacier crevasses under the snow cover, and for the search of avalanche victims in avalanche debris. The results show the capability of the instrument to detect persons and objects in the snow cover. In the future, this device may be a new tool for avalanche rescue operations. Today, the size and weight of the system prevents the accessing of very steep slopes and areas not accessible to snowmobiles. Further developments will decrease the size of the system and make it a valuable tool to quantify snow masses in avalanche release zones and run-out areas.  相似文献   

Late Visean thermal event in the northern part of the French Massif Central: new 40Ar/39Ar and Rb–Sr isotopic constraints on the Hercynian syn-orogenic extension     

Michel Faure  Patrick Monié  Christian Pin  Henri Maluski  Christele Leloix 《International Journal of Earth Sciences》2002,91(1):53-75

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Determination of Zr, Hf, Th and U by Isotope Dilution and Inductively Coupled Plasma-Quadrupole Mass Spectrometry After Concomitant Separation Using Extraction Chromatography     

Brieuc Le Fèvre  Christian Pin 《Geostandards and Geoanalytical Research》2002,26(2):161-170

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Typology of streams in Germany based on benthic invertebrates: Ecoregions, zonation, geology and substrate   总被引：1，自引：0，他引：1  

Armin Lorenz  Christian K. Feld  Daniel Hering 《Limnologica》2004,34(4):379-389

Based on 390 benthic invertebrate samples from near-natural streams in Germany we defined eight stream type groups by Non-metric multidimensional scaling (NMS). The taxa lists were restricted to Mollusca, Ephemeroptera, Odonata, Plecoptera, Coleoptera and Trichoptera species and evaluated on presence/absence level. At genus level, streams located in the lowlands differ from streams in lower mountainous areas and the Alps, while the two latter groups were undistinguishable. At species level, a clear separation of different stream size classes is visible in the lowlands; a second gradient is related to the bottom substrate. Streams in the Alps can be distinguished from streams in lower mountainous areas at species level. Within the lower mountainous regions a size gradient is detectable, a less obvious gradient indicates catchment geology. The resulting “bottom-up” stream typology is compared to other stream typological systems in Germany.  相似文献   

Key site variables governing the functional characteristics of Dissolved Natural Organic Matter (DNOM) in Nordic forested catchments   总被引：1，自引：0，他引：1  

Rolf D. Vogt  Jarkko Akkanen  Dag Olav Andersen  Rainer Brüggemann  Bimal Chatterjee  Egil Gjessing  Jussi V. K. Kukkonen  Håkon E. Larsen  Jörg Luster  Andrea Paul  Stephan Pflugmacher  Mike Starr  Christian E. W. Steinberg  Philippe Schmitt-Kopplin  Ádám Zsolnay 《Aquatic Sciences - Research Across Boundaries》2004,66(2):195-210

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Formation, subduction, and exhumation of Penninic oceanic crust in the Eastern Alps: time constraints from Ar/Ar geochronology     

Lothar Ratschbacher  Christian Dingeldey  Christine Miller  Bradley R. Hacker  Michael O. McWilliams 《Tectonophysics》2004,394(3-4):155-170

New ⁴⁰Ar/³⁹Ar geochronology places time constraints on several stages of the evolution of the Penninic realm in the Eastern Alps. A 186±2 Ma age for seafloor hydrothermal metamorphic biotite from the Reckner Ophiolite Complex of the Pennine–Austroalpine transition suggests that Penninic ocean spreading occurred in the Eastern Alps as early as the Toarcian (late Early Jurassic). A 57±3 Ma amphibole from the Penninic subduction–accretion Rechnitz Complex dates high-pressure metamorphism and records a snapshot in the evolution of the Penninic accretionary wedge. High-pressure amphibole, phengite, and phengite+paragonite mixtures from the Penninic Eclogite Zone of the Tauern Window document exhumation through ≤15 kbar and >500 °C at 42 Ma to 10 kbar and 400 °C at 39 Ma. The Tauern Eclogite Zone pressure–temperature path shows isothermal decompression at mantle depths and rapid cooling in the crust, suggesting rapid exhumation. Assuming exhumation rates slower or equal to high-pressure–ultrahigh-pressure terrains in the Western Alps, Tauern Eclogite Zone peak pressures were reached not long before our high-pressure amphibole age, probably at ≤45 Ma, in accordance with dates from the Western Alps. A late-stage thermal overprint, common to the entire Penninic thrust system, occurred within the Tauern Eclogite Zone rocks at 35 Ma. The high-pressure peak and switch from burial to exhumation of the Tauern Eclogite Zone is likely to date slab breakoff in the Alpine orogen. This is in contrast to the long-lasting and foreland-propagating Franciscan-style subduction–accretion processes that are recorded in the Rechnitz Complex.  相似文献   

Urban tourism and small tourism enterprise development in Johannesburg: The case of township tourism   总被引：1，自引：0，他引：1  

Christian M. Rogerson 《GeoJournal》2004,60(3):249-257

Urban tourism is a focus of vibrant research in developed countries. In this paper the focus is upon an element of urban tourism in a developing world city, viz., Johannesburg. Specific attention centers on an analysis of the role of small enterprise development in urban tourism. The major issues surrounding the development of small tourism businesses in two of Johannesburg's former black townships, namely Soweto and Alexandra, which are emerging as centers for so-termed ‘township tourism’ in South Africa, are investigated. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Rôle du fluor dans la formation des gisements d'émeraude de Mananjary (Est de Madagascar)     

Bernard Moine  Christian Chan Peng  Alain Mercier 《Comptes Rendus Geoscience》2004,336(6):513-522

The Mananjary emerald deposits are hosted in phlogopite-rich rocks formed through metasomatic alteration of meta-ultrabasites (hornblendites) at about 500 °C and 2 kbar due to infiltration of fluoride-rich fluids. A thermodynamic model explains the role of fluoride-complexation in the transport of Be and points to co-precipitation of F-phlogopite as the cause of beryl deposition. To cite this article: B. Moine et al., C. R. Geoscience 336 (2004).  相似文献