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Near-surface layer with laterally varying velocities

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Proceedings Papers

Paper presented at the Abu Dhabi International Petroleum Exhibition & Conference, November 11–14, 2019
Paper Number: SPE-197656-MS
... generating Wavefronts which propagate "upwards" and are received by detectors on the surface. The response (zero offsets or near stack section) is a Time-varying function and has only some resemblance with geology is "unfocussed" band is not the structure. Depending on the plane of observation this...
Proceedings Papers

Paper presented at the 2016 SEG International Exposition and Annual Meeting, October 16–21, 2016
Paper Number: SEG-2016-13959344
... data processing, especially in areas with topography variations, thickness-varying weathering zone, and lateral velocity variations. These near-surface heterogeneities can severely distort deeper structural imaging. In order to remove the distortions caused by these near-surface features, people apply...
Proceedings Papers

Paper presented at the 2012 SEG Annual Meeting, November 4–9, 2012
Paper Number: SEG-2012-0767
... velocity-depth model. We have applied our method on a 3D field dataset from the Middle East, yielding very promising results. INTRODUCTION Traditional near-surface correction algorithms are based on the assumption of a low velocity near-surface layer overlaying a medium with laterally smoothly varying...
Proceedings Papers

Paper presented at the 2018 SEG International Exposition and Annual Meeting, October 14–19, 2018
Paper Number: SEG-2018-2997700
... arrivals and later refraction arrivals as input to produce layered models with variable velocities within each layer. Then the interface between the near surface and the bedrock would be selected as the intermediate datum for long-wavelength statics calculations. For method (3), we combine traveltime...
Proceedings Papers

Paper presented at the 1984 SEG Annual Meeting, December 2–6, 1984
Paper Number: SEG-1984-0715
... of a seismic line over a permafrost body A comparison is made between conventional and tomo- graphic processing of a seismic line with an abrupt lateral change in velocity due to permafrost. The presence of the permafrost anomaly is verified by a near-surface reflection anomaly, a pull up of events...
Proceedings Papers

Paper presented at the 2018 SEG International Exposition and Annual Meeting, October 14–19, 2018
Paper Number: SEG-2018-2996939
... cwtbased approach continuous wavelet transform theoretical phase velocity reservoir characterization velocity dispersion curve geophysics data quality lateral variation dispersion curve phase velocity estimation phase velocity surface wave surface-wave tomography tomography near...
Proceedings Papers

Paper presented at the 2009 SEG Annual Meeting, October 25–30, 2009
Paper Number: SEG-2009-1401
... variation with space. We present an example which indicates that the new method is helpful for solving statics problems of very thick near- surface structures. Introduction Super-thick gravel deposited at piedmonts and huge sand dunes are distributed widely throughout western China. Its velocity varies...
Proceedings Papers

Paper presented at the 2015 SEG Annual Meeting, October 18–23, 2015
Paper Number: SEG-2015-5828951
... nonexistent reflections. The example presented here highlights some of the extreme changes in near-surface properties, including: a 2:1 lateral velocity gradient, a 3:1 vertical velocity gradient (both of which occur as abrupt velocity discontinuities), and a thin low-velocity layer overlying part of the line...
Proceedings Papers

Paper presented at the 2015 SEG Annual Meeting, October 18–23, 2015
Paper Number: SEG-2015-5819107
... velocity and the thickness of fans vary violently in vertical and lateral direction. But, they can be traced only around 2000m/s and about 70m by a conventional near-surface investigation method. According to the data processing experiences in this area, the weathered layer velocity which is traced less...
Proceedings Papers

Paper presented at the 2004 SEG Annual Meeting, October 10–15, 2004
Paper Number: SEG-2004-2116
... sampling of the laterally varying velocity field. This paper outlines a two-layer approach that takes advantage of the near-surface velocity information contained in the first breaks of 3D seismic shot-records to build a detailed velocity-depth model of the near surface for use in the statics solution. For...
Proceedings Papers

Paper presented at the 2018 SEG International Exposition and Annual Meeting, October 14–19, 2018
Paper Number: SEG-2018-2998028
... DLT to estimate the long- wavelength velocity variations. Assuming we know the approximate range of near-surface velocities, we build the initial DLT model with 6 layers. We then keep velocities unchanged and focus on inverting for the layer geometries according to Equation (3). The interface kernel...
Proceedings Papers

Paper presented at the Abu Dhabi International Petroleum Exhibition & Conference, November 13–16, 2017
Paper Number: SPE-188205-MS
... irregular frequency-dependent picks into a regularized (x, y, frequency) Rayleigh wave’s velocity volume. Lastly a laterally constrained depth inversion is performed, delivering a 3D shear wave’s near-surface depth velocity model. The second step of this workflow uses this S-wave velocity model, which...
Proceedings Papers

Paper presented at the 1995 SEG Annual Meeting, October 8–13, 1995
Paper Number: SEG-1995-0623
... is given by 624 Green s function of laterally varying media 3 The source wavelet is a bandlimited wavelet with unit strength inside the frequency range 12.5-27.0 Hz, and tapered to zero by sin -function outside this band. The acoustic velocity for the upper layer is = 1500 m/s and for the lower layer...
Proceedings Papers

Paper presented at the 2012 SEG Annual Meeting, November 4–9, 2012
Paper Number: SEG-2012-0075
... present a 3D tomostatics method based on deformable layer tomography (DLT) with 3D gradient velocity models. Because the near-surface velocity fields in many areas are composed of thickness-varying velocity layers, the DLT method focus on inverting for the thicknesses of model layers and layer velocities...
Proceedings Papers

Paper presented at the 2000 SEG Annual Meeting, August 6–11, 2000
Paper Number: SEG-2000-1197
... wavelength scholte wave sediment seg 2000 fundamental mode surface s-velocity model higher mode vertical travel time variation frequency upstream oil & gas reservoir characterization receiver line Scholte wave velocity inversion for a near surface S-velocity model and PS-statics Everhard...
Proceedings Papers

Paper presented at the 2018 SEG International Exposition and Annual Meeting, October 14–19, 2018
Paper Number: SEG-2018-2998536
... with a layer of soft soil or gravel. Figure 1: Topography of the working area. To more accurately investigate the near surface S-wave velocity model, the density of down-hole surveys was set to be 1km × 1km and additional down-hole surveys were added in the lithological transition zones and on both...
Proceedings Papers

Paper presented at the 2018 SEG International Exposition and Annual Meeting, October 14–19, 2018
Paper Number: SEG-2018-2978310
... model building Theory and Method The diving wave ray path of a source-receiver pair is a circular arc in the mountainous near-surface layer in which the seismic wave velocity increases with depth. For a horizontal surface, the depth of the turning point can be uniquely inverted by Herglotz-Wiechert...
Proceedings Papers

Paper presented at the 2016 SEG International Exposition and Annual Meeting, October 16–21, 2016
Paper Number: SEG-2016-13849319
... southern Tianshan is situated between Tarim basin and Tianshan mountain, China. The surface which is covered by mountain, Gobi gravel, alkaline and farm land is complicated with elevation varying from 912 to 2330 m. Rugged topography and strong lateral variation of near-surface give rise to low S/N ratio...
Proceedings Papers

Paper presented at the Abu Dhabi International Petroleum Conference and Exhibition, November 11–14, 2012
Paper Number: SPE-161488-MS
... azimuthally varying reflection traveltimes. To correct the effective and interval NMO velocities or ellipses for the influence of a lens, I present an analytic expression for the NMO velocity in a horizontally layered medium with laterally varying velocity. Numerical testing for an HTI model confirms that our...
Proceedings Papers

Paper presented at the 2018 SEG International Exposition and Annual Meeting, October 14–19, 2018
Paper Number: SEG-2018-2986560
... several 1D inversions that are merged assuming smooth lateral velocity changes, this approach may be counter-indicated in areas with structurally complex near- surface conditions. Even though the field data processing shown here considered a two-layered velocity model, the physical framework presented...

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