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53rd EAEG Meeting
- Conference date: 26 May 1991 - 30 May 1991
- Location: Florence, Italy
- ISBN: 978-90-73781-03-0
- Published: 28 May 1991
281 - 300 of 315 results
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The F-X dip barrier removed with a pie slice
By M. GalbraithThe method of noise reduction known as FX-Deconvolution or FX-Prediction was fust introduced by Canales (1984). Gulunay (1986) pointed out that FX is incapable of correctly predicting coherent energy when more than one dip is present. Examples show that the effect of this in the real world is not as drastic as the mathematics might indicate and FX is now widely used as an effective after stack process. (or pre-stack on fully corrected gathers).
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An introduction to FKK techniques
Authors L. G. Peardon and C. W. M. BaconIn the early days of seismic data analysis, much emphasis was placed on single trace, or 1D, processing. Eventually, we became accustomed to the idea of treating the data as a two-dimensional image and 2D processing became commonplace. Today, of course, with the advent of more and more 3D surveys, there is a requirement for 3D processing techniques. In this paper we discuss a particular 3D analysis tool, namely the FKK transform, and its applications.
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A new environment for land 3D processing
By P. DixonThe traditional medium of magnetic tapes for seismic data storage and processing is being superceded by an increasing use of discs. As these plummet in cost, they are, and will increasingly be, a much more attractive medium for the seismic industry. As well as rendering significant improvements in data handling, the benefits of disc to disc processing also extend to substantial improvements in the quality of processing due to the rapid access to data in various domains.
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Complexity analysis in the double transformed radon domain
Authors M. Vissinga and J. T. FokkemaLet Dr,s(xy;xs;w) represent a data set of a splitspread seismic experiment in the freqency domain, organized for different shot and receiver coordinates xs and xy, respectively.
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On estimation of minimum-phase wavelet
By V. BardanAn important goal of seismic processing is to shape reflection events so that the final seismic section can be interpreted easily and unambiguously. The manipulation of seismic data to achieve this goal is generally called wavelet processing. Typically, some form of deconvolution is used to perform the desired shaping of the wavelets in a seismic dataset. Many different deconvolution algorithms have been developed for processing of seismic data. They all have one thing in common: their derivation are based on mathematical assumptions about the seismic trace. The most important assumptions are: the autocorrelation of the trace is a scaled version of the seismic wavelet and the seismic wavelet is minimum-phase, In these conditions we want to estimate the minimum-phase wavelet.
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Frontier exploration techniques applied to multivintage 2D seismic
Authors E. Rieser and J. D. KerrThe Laa Area lies in the North East of Austria close to the Czechoslovakian border. It is situated in the Undisturbed Molasse of Lower Austria at the edge of the Washbergzone Overthrust. The exploration targets are within the Mesozoic Malm and are changing from structural to stratigraphic traps within the Oncophora Sandstone. Multifold seismic exploration began in 1977-79 with vibroseis data being acquired.
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A Regional water-gun profile across the quaternary basin of the Southern North Sea
Authors J. Bulat, D. Cameron and C. MesdagIn 1989, a European-Community funded project was set up to study the Quatemary deposits of the southem North Sea, involving collaboration between the geological surveys and universities in Denmark, Germany, Netherlands, Belgium and the United Kingdom. The funding has enabled the drilling of nine stratigraphic boreholes and the acquistion of 1000km of digitally recorded 10cu. in air gun data.
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A case history of high resolution seismic methods for exploration of shallow oil deposits in Suriname
Authors P. Goerdajal, J. A. C. Meekes and M. H. MulderIn the coastal region of the Republic of Suriname oil is found in Paleocene sand deposits at depths of about 300 m. Although drilling costs are relatively low for these shallow depths, the structure of the sand bodies is so complex that it was decided to carry out high resolution seismic measurements with the objective to increase the succes ration of producing wells.
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Shallow seismic and gravimetric exploration of brown coal - A review
Authors H. Gaertner, R. Seitz, H. Petzold and H. SchubertFor many years coal was the main resource of primary energy in East Germany. The production of more than 300 mio. tons a year implemented a great volume of geophysical exploration activities including shallow seismic surveys which started 15 years ago. Depending on the actual tasks and seismogeological conditions several shallow seismic techniques were developed which will be presented in this paper together with gravimetric results.
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Optimum acquisition and processing for seismic reflection techniques for extractive industries
Authors I. Hill and L. VannesteSeismic reflection is a highly desirable tool for exploration for the extractive industries due to the combination of good vertical resolution with the ability to image complex structures. The disadvantages are equally apparent, high cost, complexity and delay in receiving processed sections. In addition, the technique is not weIl understood in the extractive industries and has areputation for uncertain results. Our work at Leicester has been directed towards investigating the applicability of the reflection method to a variety of geological environments, and of clearly defining the optimum acquisition and processing techniques for this type of data. With this knowledge we can develop a total system which optimises field acquisition and provides in-field processing and section display.
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Estimation of reflection co-efficients from zero-offset field data
Authors B. Arnsten, B. Ursin and M. LandrøThe classical one-dimensional inverse problem consists of predicting reflection coefficients from surface seismic data using the one-dimensional wave equation. In one spatial dimension only plane waves propagating along one axis can be described. Spherical waves originating from a point source can not be adequately described. Many authors have considered this problem, and given examples of use on field data. An early example is Bamberger et.al. (1982). This work considers the inverse problem of predicting reflection coefficients from vertically travelling spherical waves in a one-dimensional horizontally layered medium. It is a more realistic problem than the classical one in the sense that point sources are commonly used in seismic exploration.
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Calibration of seismic data for inversion
Authors A. Ziolkowski and K. -J. KosterWe present a method, based on the critical reflection theorem, for determining the system sensitivity of a seismic recording system, using only the recorded data and the known source signature.
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A massively parallel implementation of prestack Kirchhoff depth migration
By J. van TierIntegral or Kirchhoff migration methods compute the integral solution of the wave equation, and have been used extensively in seismic imaging (Schneider, 1978; Berryhill, 1979; Berkhout, 1980). For each image point in the subsurface, these methods sum amplitudes of the recorded wavefield along a diffraction curve. The shape of the diffraction curve is described by the impulse response of the image point, the Green function, which depends on the velocity field and the shot-geophone geometry.
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Sub-surface structural images from pre-stack time migrated data at an optimum velocity using a cost effective approach
Authors G. Hodgkiss, G. E. Lane and G. HorganIt has long been recognised that tbe application of dip-moveout (DMO) does not necessarilyresolve all stacking velocity conflicts in areas where: - there is a velocity gradient - where there are steep dips Such circumstances may require pre-stack time migration. A problem with full pre-stack time migration is knowledge of the velocities with which to drive the migration. In principle finding out could be a very expensive exercise. The following case-history demonstrates how to obtain high quality from an efficient approach to gaining a good image from pre-stack time migrated data at an optimum velocity.
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The modified elastic wave equation: Applied to modelling and migration
By O. SelviIn this study a modified elastic wave equation is described which simultaneously permits both upgoing and downgoing propagation. This equation can be expressed as a nonreflecting elastic wave equation Which gives reduced reflection coefficients for transrnission across material boundaries. For horrogeneous region, it becomes the full elastic wave equation.
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An interactive approach to macro model estimation
Authors B. C. Scheffers, J. W. de Bruijn and A. J. BerkhoutAdvanced seismic processing techniques are elastic and depth-oriented. With elastic, depth-oriented processing a more accurate image of the subsurface can be obtained than with acoustic time-oriented processing. Properties of the subsurface can he divided into properties that mainly influence the propagation of seismic waves (macro properties) and properties accounting for reflection of these waves (detail). If the macro properties of the sub surface are known, the propagation effects can be removed from the data, yielding a depth image of the detail. Since the elimination of propagation effects is a major processing goal, a clear understanding of the macro properties of the subsurface is necessary.
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Prestack depth migration in the double transformed radon domain
Authors R. Tatalovic and J. T. FokkemaThe proposed migration procedure is performed in the double Radon transfonned frequency domain. The main advantages of the procedure are that it does not require a detailed input velocity model, does not need decomposition to up- and downgoing waves, and does not assume laterally invariant geology.
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High-dip time migration
Authors J. L. Black, M. A. Brzostowski and H. CrookWe introduce a steep-dip time migration algorithm which exploits the strenghts of current time migration algorithms and minimizes their weaknesses. This new time migration scheme uses Stolt and phase-shift migration as a base and finite-difference migration as a residual. The data is first redatumed using a phase-shift operation and then Stolt migrated using a constant velocity over some time interval.
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Parallel implicit finite-differences prestack migration
Authors B. Moorhead and B. BiondiPrestack finite-difference depth migration is a widely used method for imaging complex geological structures (Schultz and Sherwood, 1980). This migration method not only can be used for imaging seismic data in presence of lateral variations in velocity, but its results can be also used for improving the velocity model by applying focusing analysis to the migrated wavefield (Faye and Jeannot, 1986).
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Smoothing constraints in cross-hole seismic tomography
Authors M. Pilkington and J. P. TodoeschuckThe cross-hole seismic tomography problem is ill-posed in the sense that small changes in travel times may cause excessive variations in the calculated slowness image. These artifacts can have amplitudes large enough to mask the true velocity structure and a spatial extent small enough than the resolving power of the data. Consequently, the image should be smoothed to pro duce results that are geologically meaningful.
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