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De Figueiredo J.J.S.,University of Campinas | Oliveira F.,Federal University of Para | Esmi E.,University of Campinas | Freitas L.,Geoprocessados | And 4 more authors.
Geophysical Prospecting | Year: 2013

Hydrocarbon reservoirs are generally located beneath complex geological structures. Frequently, such areas contain seismic diffractors that carry detailed structure information in the order of the seismic wavelength. Therefore, the development of computational facilities capable of detecting diffractor points with a good resolution is desirable but has been a challenge in the area of seismic processing. In this work, we present a method for the detection of diffraction points in the common-offset-gather domain. The method applies a two-class k nearest neighbours (kNN) pattern recognition technique to amplitudes along diffraction traveltime curves to distinguish between diffractions and reflections or noise. While the method, in principle, requires knowledge of the migration velocity field, it is very robust with respect to an erroneous model. Numerical examples using synthetic seismic and field ground-penetrating-radar (GPR) data demonstrate the feasibility of the technique and show its usefulness for automatically mapping diffraction points in a seismic section. In our applications, the method was able to detect all diffractions present in the data and did not produce any false positives. © 2012 European Association of Geoscientists & Engineers. Source

Perroud H.,University of Pau and Pays de lAdour | Tygel M.,University of Campinas | Freitas L.,Geoprocessados
Geophysical Journal International | Year: 2010

The Common-Reflection-Surface (CRS) stack method is a powerful tool to produce high-quality stacked images of multicoverage seismic data. As a result of the CRS stack, not only a stacked section, but also a number of attributes defined at each point of that section, are produced. In this way, one can think of the CRS stack method as a transformation from data space to attribute space. Being a purely kinematic method, the CRS stack lacks amplitude information that can be useful for many purposes. Here we propose to fill this gap by means of a combined use of a zero-offset section (that could be a short-offset or amplitude-corrected stacked section) and common midpoint gather. We present an algorithm for an inverse CRS transformation, namely one that (approximately) transforms the CRS attributes back to data space. First synthetic tests provide satisfying results for the two simple cases of single dipping-plane and single circular reflectors with a homogeneous overburden, and provide estimates of the range of applicability, in both midpoint and offset directions. We further present an application for interpolating missing traces in a near-surface, high-resolution seismic experiment, conducted in the alluvial plain of the river Gave de Pau, near Assat, southern France, showing its ability to build coherent signals, where recording was not available. A somewhat unexpected good feature of the algorithm, is that it seems capable to reconstruct signals even in muted parts of the section. © 2010 The Authors Geophysical Journal International © 2010 RAS. Source

Oliveira F.D.S.,Federal University of Para | De Figueiredo J.J.S.,Federal University of Para | De Figueiredo J.J.S.,National Institute of Petroleum Geophysics INCT GP | Freitas L.,Geoprocessados
Acta Geophysica | Year: 2015

A redatuming operation is used to simulate the acquisition of data in new levels, avoiding distortions produced by near-surface irregularities related to either geometric or material property heterogeneities. In this work, the application of the true-amplitude Kirchhoff redatuming (TAKR) operator on homogeneous media is compared with conventional Kirchhoff redatuming (KR) operator restricted to the zero-offset case. The TAKR and the KR operators are analytically and numerically compared in order to verify their impacts on the data at a new level. Analyses of amplitude and velocity sensitivity of the TAKR and KR were performed: one concerning the difference between the weight functions and the other related to the velocity variation. The comparisons between operators were performed using numerical examples. The feasibility of the KR and TAKR operators was demonstrated not only kinematically but also dynamically for their purposes. In other words, one preserves amplitude (KR), and the other corrects the amplitude (TAKR). In the end, we applied the operators to a GPR data set. © 2014 Versita Warsaw and Springer-Verlag Wien Source

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