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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 132 (1990), S. 583-597 
    ISSN: 1420-9136
    Keywords: Reflection ; seismology ; conservation ; inversion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We show that the time-dependent wave equation in both one and two spatial dimensions possesses quantities which are globally conserved. We show how these conserved quantities can be used to determine the characteristic impedance, the rock density and the elastic constant of the rock. We also demonstrate that the conserved quantities possess the capability of determining and/or bracketing the unknown component of the direct pressure response, which is required to begin downward continuation algorithms. Further, we demonstrate that the conserved quantities are always available irrespective of the source structure in time. Numerical instability, arising if the “filtering” due to the source structure is too harsh, can then be controlled to a degree by demanding that the conserved quantities be indeed conserved.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-8868
    Keywords: Thermal indicators ; inversion ; tomography ; paleoheat flux
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract A quantitative tomographic method to determine simultaneously several geological, geochemical, and geothermal parameters associated with reconstruction of the geohistory and thermal history of sediments in a well is presented. Using vitrinite reflectance data from the well Inigok-1, National Petroleum Reserve of Alaska, the numerical algorithm was tested and found to be effective in delineating the variation of heat flux with time. In addition, the size and timing of a major unconformity also were bracketed. Application of tomography using apatite fission track distributions with depth as a thermal indicator enabled not only the thermal history of two wells in the NW Canning Basin of Australia to be determined, but also the chemical parameters associated with fission track annealing to be constrained. Results of both the Alaska study and the Australian study were consistent with the qualitative behavior inferred from current geological models.
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  • 3
    ISSN: 1573-8868
    Keywords: thermal indicators ; paleoheat ; vitrinite reflectance ; age determination ; inversion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Thermal indicator data are used in an inverse mode to determine ages of stratigraphic horizons simultaneously with paleoheat flux. Results from “blind” tests on wells with horizon ages ranging from Ordovician through Carboniferous and Jurassic to Miocene indicate that thermal indicator inversions are capable of resolving such ages to within about 10% uncertainty. Results using the inversion procedure with one thermal indicator (vitrinite reflectance) were comparable to the results using another independent thermal indicator (sterane isomerization) in the same well. The activation energy for sterane isomerization was determined to be 30±15 kJ mol−1. In addition: (a) the age of a stratigraphic horizon, the thickness of eroded sediments at an unconformity, and the variation of paleoheat flux with time were determined simultaneously by thermal indicator inversion in a single well; (b) two neighboring wells, less than 10 km apart, provided essentially identical ages for the same formation when tested using the inversion procedure. The ability to determine stratigraphic horizon ages from inversion of thermal indicator data implies that sedimentation rates can be determined; thus, basinal evolution can be inferred to a degree of resolution not previously obtainable from assumed interpolation methods applied to determine the age of horizons between a limited set of stratigraphic horizons of known ages.
    Type of Medium: Electronic Resource
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