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Extended subspace method for cross-talk mitigation in multi-parameter inversion

  • US 10,459,117 B2
  • Filed: 05/08/2014
  • Issued: 10/29/2019
  • Est. Priority Date: 06/03/2013
  • Status: Active Grant
First Claim
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1. A computer-implemented method for iteratively inverting measured geophysical data to infer 3D subsurface models of N physical properties with N≥

  • 2 and prospecting for hydrocarbons, comprising;

    providing an initial model for each physical property, wherein a subsurface region is subdivided into discrete cells, each cell having a value of the physical property;

    for each physical property and for each of a plurality of the cells, representing a search direction, indicating whether the initial model needs to be updated positively or negatively, as a linear combination of M basis vectors with M>

    N, wherein;

    each basis vector has its own coefficient in the linear combination, said coefficient to be determined;

    the basis vectors are chosen such that their coefficients account for cross-talk between the N physical properties during inversion, wherein a mixing matrix is formed from the coefficients of the basis vectors, and degree of mixing between the model updates for the N physical properties is adjusted by scaling off-diagonal elements of the mixing matrix with scaling factors that are optimized in the inversion; and

    optimal values of the coefficients are simultaneously solved for, using a computer, to minimize or maximize an objective function measuring misfit between model-simulated geophysical data and the measured geophysical data, wherein solving for the coefficients is performed at least by numerical computation constrained by the geophysical data;

    generating search directions with the optimal values of the coefficients, and generating an updated model for each physical property by making changes, respectively, to the initial model for each physical property in the search directions; and

    producing an image of the subsurface from the updated model, which includes subsurface reflectors, positioned with the optimal coefficients, that returned seismic energy to receivers that recorded the measured geophysical data, and prospecting for hydrocarbons according to structural features of the subsurface region.

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