Guilherme S. Rosa

A Robust Mode-Matching Algorithm for the Analysis of Triaxial Well-Logging Tools in Anisotropic Geophysical Formations

In this paper, a new pseudoanalytical axial mode-matching formulation is introduced to provide a flexible technique for analyzing direction well-logging tools in anisotropic formations. The presented technique does not rely on spatial discretization as former well-known methods. In this problem, a number of coil antennas with arbitrary relative tilt angle with respect to the symmetry axis are used to radiate electromagnetic fields in a cylindrically layered medium with both axial and radial stratifications, composed of a metallic mandrel, a borehole, and a surrounding layered earth formation. This configuration corresponds to that of triaxial well-logging tools used for oil and gas exploration. Our approach combines closed-form solutions of Maxwell’s equations for uniaxially anisotropic media in cylindrical coordinates with the generalized scattering matrix (GSM) at each axial discontinuity based on the mode-matching technique. The electromagnetic field from the tilted-coil source is represented by a set of modal coefficients that, after computation using GSM matrices, are used to extract the transimpedances of the well-logging tool.

Improvements on the Search Modal Propagation Constants in Lossy Circular Waveguides

In this letter, we review the calculation of the propagation constants in a circular lossy waveguide. We highlighted some improvements in order to find the propagation constants of the guided modes. We present a new characteristic equation that simplifies the application of the winding number technique described in previous publications, and also we discussed some numerical criteria for the application of this technique.

Relativistic Aspects of Plane Wave Scattering by a Perfectly Conducting Half-Plane With Uniform Velocity Along an Arbitrary Direction

The scattering of time-harmonic plane waves by a perfectly electrically conducting (PEC) half-plane (H-P) in relativistic uniform motion is discussed. The problem is formulated using the special theory of relativity by means of the Lorentz transformation applied to the classic Sommerfeld solution. Exact fields are obtained for the 3-D vector problem of scattering of an obliquely incident and arbitrarily polarized plane wave by a PEC H-P in relativistic translational motion. The total fields are then presented as the relativistic analog of their motionless counterparts and an association with the uniform asymptotic theory of diffraction framework is inferred. In addition to recovering known features such as the relativistic Doppler effect and shadow boundary shifts, it is herein depicted a polarization coupling effect due to motion that can give rise to a 3-D scattered field with all components present even for a linearly polarized incident wave. Validating results and illustrative examples are also presented.

Pseudo-Analytical Modeling for the Electromagnetic Propagation in Stratified Cylindrical Structures

In this letter, we present a pseudo-analytical formulation to model cylindrical structures composed by both radial and axial dielectric layers. In order to improve the location of the complex propagation constants, we propose a series of considerations on the argument principle, the so-called winding number technique. We use the complex coordinate stretching formulation of the perfectly matched layers to analyze unbound structures. The axial discontinuities are figured out by an analytical formulation of the mode matching technique. The mode excitation from electric current sources combined with the generalized scattering matrix allows us to accurately compute the fields along the entire structure.

Electromagnetic propagation along lossy anisotropic and radially stratified cylindrical structures

In this paper, we present a formulation to analyze the electromagnetic propagation in circular structures filled with complex materials. We consider an uniaxially anisotropy to describes each layer of a stratified cylindrical waveguide. A perfectly matched layer (PML) is used to compute the fields of unbounded waveguides. The mode excitation from an electric current source combined with the mode matching technique (MMT) allows to analyze the propagation through axial discontinuities at the junction between two radially stratified waveguides. Preliminary results are presented.

Electromagnetic analysis of wireless telemetry for oil fields

The monitoring and control of the sensors in an oil well casing have been classically performed by electrical cables that connect sensors and actuators in the deep end to the surface station. Classical telemetry techniques have critical aspects in ultra-deep wells, and in some cases its use is impractical. This motivates the investigation of methods for wireless telemetry. In this paper, the electromagnetic characteristics of an oil well casing are analyzed rigorously. Approximations are derived from modal analysis, and the oil well is modeled as a coaxial waveguide heterogeneously filled with lossy matters. The problem of propagation is modeled by the mode matching technique and feasibility of wireless telemetry in oil wells is discussed.

Corrections to “Relativistic Aspects of Plane Wave Scattering by a Perfectly Conducting Half-Plane With Uniform Velocity Along an Arbitrary Direction” [Sep 17 4759-4767]

In a recent paper [1] , there was a typo in (13), which should read as a scalar equation for the

Pseudoanalytical modeling of electromagnetic well-logging sensors inside directional wells

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Electromagnetic modeling of wave propagation in curved boreholes for geophysical exploration

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A comparison of numerical mode-matching techniques for the analysis of well-logging tools

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