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  • 2000-2004  (3)
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  • 1
    Publication Date: 2003-01-01
    Description: Current advances in finite element computer codes and increase in computer power theoretically allow quantitative modelling of the geomechanical effects of hydrocarbon depletion from reservoirs. Here we show that it is technically possible to incorporate the full complexity of the 3D geological structure of a reservoir including faults into geomechanical models. In the workflow GOCAD is used for the structural modelling, integrated with DIANA for the geomechanical calculations. A case study on the Roswinkel gas field in the eastern Netherlands illustrates the working methodology. The case study clearly shows the strong dependency of gas depletion deformation effects on the prevailing tectonic stress field. Our models for gas depletion predict a stabilization of the stress field (further away from failure) for reservoirs in compressive and strike-slip regimes. On the other hand extensional stress regimes will result in failure of the reservoir, in agreement with observed earthquakes, provided that (a) the reservoir material or existing faults are weak and (b) the state of stress is close to failure of the material. The Roswinkel field, which is marked by a high abundance of earthquakes occurring after gas depletion started, is therefore most likely marked by an extensional tectonic regime and by geomechanically weak rock or pre-existing faults. According to base Tertiary fault displacements and the World Stress Map, the extension (minimum horizontal principal stress) is most likely NE-SW oriented.
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Layered structures of cubic yttria-stabilized zirconia (YSZ) sandwiched between two layers of platinum/YSZ composites with the platinum concentration varying between 20 and 55 vol % were prepared. Large double-layer capacitances were obtained due to the presence of large three-dimensional electrode surface areas in the composite layers. The layers were subjected to image analysis obtained from scanning electron microscopy micrographs. The specific surface area of the platinum particles decreased from ∼17×103 to ∼13.5×103 cm2/cm3 with increasing Pt concentration. Image analyses obtained with an in-lens detector revealed that the effective surface area of the Pt particles that were part of a conducting percolative network increased with Pt concentration to ca. 11×103 cm2/cm3 at a Pt metal volume fraction of 0.50. Impedance spectroscopy measurements performed at 550 °C demonstrated that the capacitance increased with increasing Pt concentration in the composite layer and optimal values as high as 4.3±1.3 kF/m2 at 50 vol % Pt were recorded. The specific electrode surface area calculated from this data was in good agreement with the data obtained from image analysis. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2001-01-01
    Description: Many investigations show relationships between topographical factors and the spatial distribution of soil moisture in catchments. However, few quantitative analyses have been carried out to elucidate the role of different hydrological processes in the spatial distribution of topsoil moisture in catchments. A spatially distributed rainfall-runoff model was used to investigate contributions of subsurface matric flow, macropore flow and surface runoff to the spatial distribution of soil moisture in a cultivated catchment. The model results show that lateral subsurface flow in the soil matrix or in macropores has a minor effect on the spatial distribution of soil moisture. Only when a perched groundwater table is maintained long enough, which is only possible if the subsurface is completely impermeable, may a spatial distribution in moisture content occur along the slope. Surface runoff, producing accumulations of soil moisture in flat flow paths of agricultural origin (field boundaries), was demonstrated to cause significant spatial variations in soil moisture within a short period after rainfall (〈2 days). When significant amounts of surface runoff are produced, wetter moisture conditions will be generated at locations with larger upstream contributing areas. © 2001 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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