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- Volume 28, Issue 4, 2010
First Break - Volume 28, Issue 4, 2010
Volume 28, Issue 4, 2010
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Impact on hydrocarbon exploration potential of a structural study of the Chott El Jerid area, Tunisia
Authors G. Chaari and P. TremolieresGhassen Chaari, Al Thani Emirates Petroleum, and Paul Trémolières, retired professor, Institut Français du Pétrole, describe a structural study of the Tunisian Tozeur Block to identify the most prospective areas for future seismic and drilling activity.
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New seismic may put offshore Cyprus hydrocarbon prospects in the spotlight
Authors L. Montadert, Ø. Lie, P.H. Semb and S. KassinisBased on newly interpreted seismic data, Lucien Montadert, Øystein Lie, Per Helge Semb and Solon Kassinis come to some new conclusions about the prospectivity of the offshore Cyprus area of the Mediterranean.
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Unconventional view of hydrocarbon prospecting in Israel and adjacent areas
Authors B.E. Khesin, Y.A. Vapnik and S.E. ItkisBoris E. Khesin, Yevgeny A. Vapnik and Sonja E. Itkis, believe that the traditionally pessimistic view of potential hydrocarbon resources in Israel and Jordan should be revised in view of the results of new integrated geophysical studies suggesting promising targets for prospecting such as the methane-hydrates of the Eastern Mediterranean, bituminous carbonates, and gas deposits related to fossil mud volcano province of Israel and Jordan.
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Thematic Set: Full-azimuth modelling and field trial at Heidrun
Authors M. Houbiers and M. ThompsonOver recent decades, the Heidrun Field in the Norwegian Sea has been imaged several times with conventional narrow-azimuth seismic surveys. The extensively faulted structure and the presence of a dome-shaped feature cause imaging challenges in some areas. A modelling study shows that a survey design with increased crossline offset and fold, such as a four-vessel wide-azimuth or coil shooting design, can produce improved subsurface images with fewer artefacts, sharper fault edges, and more consistent amplitudes along horizons compared to images from conventional acquisition. Based on the modelling results, a field trial with coil shooting acquisition was carried out at Heidrun. The survey design with 18 intersecting coils provided full-azimuth, high fold data over a 2.5 × 2.5 km2 target area with sufficient surrounding aperture for comparing the migrated data with previously acquired conventional seismic data. Preliminary processing of the coil shooting data show fewer dip conflicts and an improved fault definition at the reservoir level compared to conventional survey data. However, due to a smaller migration aperture, the images from the field trial have lower spatial frequency content, so some details of the structure are lost.
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Thematic Set: Velocity model building with wave equation migration: the importance of wide azimuth input, versatile tomography, and migration velocity analysis
Authors F. Audebert, P. Jousselin, B. Duquet and J. SirgueWave equation migration is suitable for imaging in complex structures. Ideally, its imaging capability should be matched by corresponding velocity model building tools. However, the tool of choice for velocity model building, ray-based tomography, at first sight seems weakly compatible with wave equation migration. To overcome this contradiction we propose several strategies. The first is to convert the wave equation migration image gathers, typically indexed by subsurface offset, into a format appropriate for tomography: local reflection angle or its tangent. In conjunction with this conversion, we employ a datuming procedure to restrict the tomography to a localized domain where it is compatible with the wave equation migration band-limited propagation. A second strategy, more expensive and not yet widely tested, is to replace ray-based tomography with wave-equation-based migration velocity analysis, assuring complete compatibility with the imaging. In all cases, we notice that having wide-azimuth data makes velocity model building easier, as any chosen subsurface azimuth contains specular information.
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Thematic Set: Depth migration velocity model building with wave equation imaging
Authors J. Higginbotham, M. Brown and C. MacesanuIn spite of impressive advances in the application of wave equation imaging technology to generate images of complex structures, ray-based tools are generally used for the equally important step of velocity determination. Closing the experimental loop, by using the same wave equation imaging algorithm to measure velocity and to obtain a final image, is more than just philosophically pleasing. In strata exhibiting complex velocity structure, wave equation migration algorithms may be the only tools able to image some reflectors, so it stands to reason in such cases that only a wave equation velocity update can reliably measure velocity errors near these reflectors. In this article, we present a wave equation velocity update scheme, similar to depth focusing analysis, utilizing the time-shift imaging condition. We demonstrate the robustness of this approach under salt and in a land fault shadow example with limited acquisition effort. A common criticism levied against wave equation migration is the difficulty in efficiently obtaining 3D angle gathers (incidence, azimuth, and dip angle). We also present an efficient Fourier-domain angle decomposition technology for wave equation migration and demonstrate efficacy on synthetic and field data examples.
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Thematic Set: Full waveform inversion: the next leap forward in imaging at Valhall
Authors L. Sirgue, O.I. Barkved, J. Dellinger, J. Etgen, U. Albertin and J.H. KommedalWe present the results of applying full waveform inversion at the Valhall Field in the Norwegian sector of the North Sea. The resulting velocity model not only substantially improves the depth-migrated image, but also offers an excellent basis for detailed interpretation itself, because it reveals many geological features not visible in the migrated image. These results demonstrate that full waveform inversion can produce spectacular results on industrial-scale real 3D seismic data.
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Thematic Set: Full waveform inversion of a deep water ocean bottom seismometer dataset
Authors R.-E. Plessix and C. PerkinsImprovements in seismic acquisition, such as the collection of long-offset and wide-azimuth data, coupled with the increase in computer power have made full waveform inversion methods based on the minimization of the residuals between modelled and observed data viable. Here we present results from the application of full waveform inversion to an ocean bottom seismometer dataset recorded in the Gulf of Mexico. First, an isotropic formulation is applied to show the relevance of this approach for capturing fine details, such as gas accumulations, in the shallow part of the velocity model where the diving waves propagate. Also, to produce flatter common image gathers in the deep part of the model, an anisotropic formulation with a fixed ratio between the horizontal and the vertical velocities is used. This real example shows that full waveform inversion is an affordable approach in 3D for velocity analysis, at least with certain types of datasets, even though it is not a standalone method. It also illustrates the benefit of improving the shallow part of the velocity model to better image the deeper part.
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Volumes & issues
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Volume 42 (2024)
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Volume 41 (2023)
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Volume 40 (2022)
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Volume 39 (2021)
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Volume 38 (2020)
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Volume 37 (2019)
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Volume 36 (2018)
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Volume 35 (2017)
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Volume 34 (2016)
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Volume 33 (2015)
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Volume 32 (2014)
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Volume 31 (2013)
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Volume 30 (2012)
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Volume 29 (2011)
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Volume 28 (2010)
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Volume 27 (2009)
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Volume 26 (2008)
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Volume 25 (2007)
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Volume 24 (2006)
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Volume 23 (2005)
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Volume 22 (2004)
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Volume 21 (2003)
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Volume 20 (2002)
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Volume 19 (2001)
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Volume 18 (2000)
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Volume 17 (1999)
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Volume 16 (1998)
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Volume 15 (1997)
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Volume 14 (1996)
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Volume 13 (1995)
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Volume 12 (1994)
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Volume 11 (1993)
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Volume 10 (1992)
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Volume 9 (1991)
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Volume 8 (1990)
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Volume 7 (1989)
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Volume 6 (1988)
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Volume 5 (1987)
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Volume 4 (1986)
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Volume 3 (1985)
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Volume 2 (1984)
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Volume 1 (1983)