Non-Hyperbolic Velocity Analysis of Seismic Data from Jequitinhonha Basin, Northeastern Brazil.

Francisco G Ortega,Amin Bassrei,Ellen N.S Gomes,Andrei G De Oliveira

doi:10.1590/0001-3765202020180619

Abstract

Normal moveout (NMO) velocity is used in seismic data processing to correct the data from the moveout effect. This velocity depends on the medium above the reflector and it is estimated from the adjustment of a hyperbolic function that approximates the reflection time. This approximation is reasonable for media formed by isotropic layers. For deeper exploration targets, which effectively behave as anisotropic media, the NMO velocity estimate from the hyperbolic approximation becomes imprecise. One possibility is the use of non-hyperbolic approximations for the reflection time and deeming the medium to be anisotropic. However, these approximations make the NMO velocity estimation a more complex problem, since the anisotropic parameters are unknown. In this study the NMO velocities for a vertical transverse isotropy medium are estimated using two non-hyperbolic reflection time approaches. For comparing the two methodologies that estimate NMO velocity, a 2-D dataset from Jequitinhonha Basin is used and it presents anisotropic behavior. The results show that this approach produces more consistent results than the conventional approach, which ignores the anisotropy of the medium.

Highlights

After the seismic reflection data acquisition, the same data is processed, so that the final product is the seismic section, to be interpreted by geophysicists and geologists
This is done by applying the normal moveout (NMO) correction to seismic traces sorted in groups or families of common midpoints (CMPs), and the traces are summed along the offset axis
We show that even when the medium presents anisotropy it is possible to estimate a consistent NMO velocity model without the knowledge of the anisotropic parameters of the medium, with better results than the conventional approach

Summary

Introduction

After the seismic reflection data acquisition, the same data is processed, so that the final product is the seismic section, to be interpreted by geophysicists and geologists. There are three main steps in seismic data processing: deconvolution, stacking and migration, in their usual order of application (Yilmaz 1987). There is the stacking which is a compression procedure, so that the volume of data is reduced to a stacked seismic section. This is done by applying the normal moveout (NMO) correction to seismic traces sorted in groups or families of common midpoints (CMPs), and the traces are summed along the offset axis. To obtain the stacked image the data is transformed from source-receiver coordinates to CMP families. A CMP family consists of several seismic traces that have different source and

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Conclusion