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  • 1
    Publication Date: 2019-11-04
    Description: A common problem in dolomite reservoirs is the heterogeneous distribution of porosity-reducing diagenetic phases. The intrasalt carbonates of the Ediacaran-Early Cambrian Ara Group in the South Oman Salt Basin represent a self-sourcing petroleum system. Depositional facies and carbonate/evaporite platform architecture are well understood, but original reservoir properties have been modified by diagenesis. Some of the carbonate reservoirs failed to produce hydrocarbons at acceptable rates, which triggered this study. The extent of primary porosity reduction by diagenetic phases was quantified using point counting. To visualize the distribution of diagenetic phases on a field scale, we constructed 2D interpolation diagenesis maps to identify patterns in cementation. The relative timing of diagenetic events was constrained based on thin-section observations and stable isotope analyses. Near-surface diagenesis is dominated by reflux-related processes, leading to porosity inversion in initial highly porous facies and a patchy distribution of early cements. This strong diagenetic overprint of primary and early diagenetic porosity by reflux-related cements leads to a reduction of stratigraphic and facies control on porosity. Calcite was identified as a burial-related cement phase that leads to an almost complete loss of intercrystalline porosity and permeability. Bitumen is an important pore-occluding phase and time marker of the deep-burial realm. The stratigraphic position of the dolomite reservoirs embedded at the base of a salt diapir had a strong impact on its diagenetic development. The salt isolated the dolomites from external fluids, leading to a closed system diagenesis and the buildup of near lithostatic fluid pressures. In combination, these processes decreased the impact of further burial diagenetic processes. The study highlights that cement distribution in salt-encased carbonate reservoirs is mainly related to early diagenetic processes but can be very heterogeneous on a field scale. Further work is needed to implement these heterogeneities in an integrated numerical reservoir model.
    Print ISSN: 1468-8115
    Electronic ISSN: 1468-8123
    Topics: Geosciences
    Published by Hindawi
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  • 2
    Publication Date: 2021-03-29
    Description: Movement on fault planes causes a large amount of smaller-scale deformation, ductile or brittle, in the area surrounding the fault. Much of this deformation is below the resolution of reflection seismics (i.e. sub-seismic, 〈10m displacement), but it is important to determine this deformation, since it can make up a large portion of the total bulk strain, for instance in a developing sedimentary basin. Calculation of the amount of sub-seismic strain around a fault by 3-D geometrical kinematic retro-deformation can also be used to predict the orientation and magnitude of these smaller-scale structures. However, firstly a 3-D model of the fault and its faulted horizons must be constructed at a high enough resolution to be able to preserve fault and horizon morphology with a grid spacing of less than 10 m. Secondly, the kinematics of the fault need to be determined, and thirdly a suitable deformation algorithm chosen to fit the deformation style. Then by restoring the faulted horizons to their pre-deformation state (a ‘regional’), the moved horizons can be interrogated as to the strain they underwent. Since strain is commutative, the deformation demonstrated during this retro-deformation is equivalent to that during the natural, forward deformation...
    Description: conference
    Keywords: 551 ; TQC 220 ; TSB 000 ; VAE 200 ; VAE 400 ; VBE 000 ; Reflexionsseismik {Geophysik} ; Mitteleuropa {Geophysik} ; Geodynamik der Lithosphäre {Geologie} ; Tektogenese {Geologie} ; Modellierung von Prozessen in der Geosphäre ; Niedersächsiches Becken ; Dreidimensionale Seismik ; Störung 〈Geologie〉 ; Kinematik ; Modell
    Language: German
    Type: anthologyArticle , publishedVersion
    Format: application/pdf
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  • 3
    Publication Date: 2021-03-29
    Description: The Aachen RWTH-1 well was drilled to 2544mTVD for geothermal purposes and gives substance to extensive geoscientific research. It is located in a hydrothermally and seismically active area of the Aachen Anticline, 500m NW of the Aachen Overthrust and 420m ENE of the Laurensberg Fault. The main focus of this PhD work is the structural and microtectonic analysis of the cores sampled. For 94% of the total well length the collected cuttings give information of the lithology and stratigraphy of the subsurface. A total of 145.5m was cored in three different intervals. A complete set of wireline measurements including high resolution borehole image allow mapping of fractures and folds, and linking the core to the logs. About 100 core samples were selected for detailed microstructural analysis.
    Description: conference
    Keywords: 551 ; VBL 500 ; VAE 200 ; VKA 130 ; VKA 200 ; Geologische Bohrungen in einzelnen Regionen ; Geodynamik der Lithosphäre {Geologie} ; Optische Petrographie ; Gefügekunde der Gesteine ; Aachen 〈Region〉 ; Tiefbohrung ; Dünnschliff ; Gefüge 〈Gesteinskunde〉
    Language: German
    Type: anthologyArticle , publishedVersion
    Format: application/pdf
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