Carlos Eduardo Theodoro

Nonlinear impedance inversion for attenuating media

Applications of seismic impedance inversion normally assume the data are free of multiples and transmission effects, requiring knowledge of the seismic pulse that is assumed to be stationary. An alternative formulation for impedance inversion is based on an exact frequency-domain, zero-offset reflectivity function for a 1D medium. Analytical formulas for the Frechet derivatives are derived for efficient implementation of an iterative nonlinear inversion. The exact zero-offset reflectivity accounts for internal multiples and transmission effects in the data. Absorption and dispersion are also conveniently handled if a reasonable estimate for the quality (Q) factor of the medium is available. A series of convenient features are included in the inversion algorithm: an automatic estimation of the amplitude spectrum of the seismic pulse, an impedance transform that makes the inversion independent from the initial smooth model, and a practical approach to estimate the regularization weight. Numerical tests usin...

Target oriented illumination analysis using wave equation

The proposed methodology requires considerably less resources, in terms of processing time and disk space, than the traditional procedure using wave equation. The traditional procedure compares depth images obtained by a migration scheme, after modeling the complete dataset for a certain acquisition geometry. Both methodologies are more accurate than the results based on ray tracing modeling in complex areas (due to the high frequency approximations involved in this scheme).

Ultra-deepwater 4-C offshore Brazil

This paper is the case history of an ultra-deepwater 4-C seismic program, recently acquired in the Campos and Santos basins, offshore Brazil. All aspects of the program will be discussed, including the feasibility study which first indicated the potential value of multicomponent technology to this region, to the survey objectives, to the illumination analysis used in designing the survey, to the field operations, to the fully processed results. Acquisition was completed on 19 April 2005, and the fully processed data were delivered in early November 2005.

Tomographic Inversion Over Diffraction CFP Operators In Structurally Complex Areas

In the universe of tomographic techniques aiming to determine the subsurface velocity field, inversion over CFP Operators (CFPOs) reduces depth-velocity ambiguity. Its main drawback is the operator estimation for very complex areas, where conventional CFPO estimation is damaged by the non-continuity of events and diffractions. We overcome this problem using diffractions in Common Offset Gathers (COG) to estimate CFPOs. A synthetic example based on a geologic-geophysics model of the Santos Basin (offshore Brazil) is used to validate the idea. An overview of the inversion workflow is presented in which a Singular Value Decomposition (SVD) pseudo-inverse technique is explored.