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ABSTRACT Considering the influence of conductivity and displacement current at the meantime, we have derived a few functional formulation of A-f and developed a 3D finite element code to simulate electromagnetic well logging response in full 3D and wide range frequency. We have computed the field coil. We have also given the response of induction well logging in derived wells. Finally we have analyzed the influence of coil radius and anisotropy. An effective method to solve full three-dimensional (3-D) electromagnetic (EM) Fields in great demand for practical application of EM methods.
- Africa > South Africa > Western Cape Province > Indian Ocean (0.24)
- North America > United States > Texas > Bexar County > San Antonio (0.18)
ABSTRACT We present a unified workflow for processing, inversion, and interpretation of 3-D seismic data that is applicable to love-relief structure and complex structures associated with extensional and compressional tectonics. With some modifications, the workflow also is applicable to complex overburden structures associated with salt and over-thrust tectonics. The seismic workflow described in this paper includes earth modeling and imaging in depth with unique aspects. First, we want to obtain the best estimate of a structurally consistent initial earth model in depth where layer velocities are based on rms velocities associated with migrated data so as to minimize the work required to update the model and thus obtain a final earth model in depth.
Summary Presented here is a method for reducing the computational storage cost associated with solving large-scale linear systems arising from the discretization of the time-harmonic Maxwell''s equations in the low{frequency limit. Specifically, a “matrix-free" implementation of the well-known staggered grid finite difference (FD) algorithm is derived for use with Krylov subspace methods for solving the resulting sparse system of linear equations. The method is matrix-free in that the Krylov methods require computing the action of the matrix on an arbitrary vector, but not explicit storage of the matrix itself. For example, in using the quasi-minimal residual method to solve a linear system with NDF degrees of freedom, the strorage cost is reduced from 23NDF to 10NDF complex double precision words.
SUMMARY Based on observations from two distinct settings, a faulted sandstone aquifer and a clay{rich alluvial floodplain, we present evidence that near{surface controlled{source elec- tromagnetic (CSEM) responses are fractal signals. The observed responses are very rough; they do not show the statistical behavior of smoothly varying functions superim- posed by random Gaussian noise. This suggests that CSEM signals reflect self{similarity in the underlying, heteroge- neous electrical conductivity structure. The process of EM induction in the Earth thus may be regarded as a mapping from a fractal medium to a fractal response. This result poses exciting new challenges for numerical modeling and geological interpretation of CSEM responses in the areas of engineering and environmental geophysics and shallow resource development.
Summary The inverse scattering multiple attenuation (ISMA) algorithm for ocean bottom seismic (OBS) data can be formulated as a combination of streamer data and OBS data in the form of a series expension for each of the four components of OBS data. Besides the actual data, which constitutes the first term of the series, each other term aims at removing one specific order of multiples. If the streamer data do not contain free-surface multiples, we found that the computation of only the second term of the series is needed to predict and remove all orders of multiples, irrespective of the water depth. As the computation of the various terms of the series is the most expansive part of ISMA, this result can produce signifi- cant savings in computation time, even in data storage, as we no longer need to store the various terms of the series.