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Results: 995

A ghost prediction based OBC PZ summation method for complex seabedA ghost prediction based OBC PZ summation method for complex seabed
EAGE - European Association of Geoscientists and Engineers, 2015
Fei Allen Sun | Kunlun Yang | Barry Hung
©2015 EAGE
Summary
In ocean bottom acquisition, receiver side deghosting is normally done by summing together the hydrophone P and geophone Z data. A prerequisite for this method to work effectively is the precise calibration of geophones to hydrophones, so as to compensate for the differences in sensitivity and coupling. A ?cross-ghosting? approach has been proposed to extrapolate geophone and hydrophone data to have the same manner for matching. However, as far as we know, existing cross-ghosting methods are based on a 1D geology assumption. In this paper, we describe a cross-ghosting method using 2D wave-equation extrapolation, which accurately predicts the ghost according to the structure of the seafloor.
High-dimensional resolution enhancement in the continuous wavelet transform domain High-dimensional resolution enhancement in the continuous wavelet transform domain
CSEG - Canadian Society of Exploration Geophysicists, 2015
Shaowu Wang | Juefu Wang | Tianfei Zhu
©2015 CGG
Summary
We present a method to enhance the bandwidth of seismic data in the continuous wavelet transform (CWT) domain. By utilizing the features of CWT in detecting time-variant frequency content and automatically designing band-dependent time window, we can enhance the seismic bandwidth mostly based on signal. A high-dimensional implementation of the method enables us to make full use of the information from nearby data to stabilize the algorithm. A real data example shows that applying the proposed method at different processing stages has different benefits. If implemented properly, the approach is AVO friendly and a better alternative to conventional spectrum balancing.
Incorporating seismic velocity data in AVO/AVA low frequency models by honoring local geologyIncorporating seismic velocity data in AVO/AVA low frequency models by honoring local geology
EAGE - European Association of Geoscientists and Engineers, 2015
Bobby Hak | Peter Mesdag
©2015 EAGE
Summary
Low frequency information is required for quantitative reservoir characterization. Because borehole measurements are often (laterally) sparse and preferential towards reservoir locations, there is much uncertainty on the low frequency models away from well control. Methods to improve the reliability of the low frequency data include the use of low frequency update schemes or seismic attribute maps. The use of seismic velocity data for trend modeling is well recognized, but the methodology for incorporating the velocity is not always clearly described. Especially in case of an AVO/AVA study, a rigorous workflow is desired. Here, we propose a method to include seismic velocity data. The methodology uses local geological knowledge through rock physics relations. We validate by comparing results of a more common method with our proposed workflow at blind wells. This shows that a low frequency model that does not use the velocity data misses significant (lateral) variations that are representative for the local geology.
Least Squares Kirchhoff Depth Migration: potentials, challenges and its relation to interpolationLeast Squares Kirchhoff Depth Migration: potentials, challenges and its relation to interpolation
CSEG - Canadian Society of Exploration Geophysicists, 2015
Daniel Trad
©2015 CGG
Summary
Least squares migration (LSM), like interpolation, has the potential to address sampling issues and generate images with better amplitudes than migration. Although both techniques share the same goal and often the same formulation, they differ on the nature of the model that is used to predict the data. For LSM the cost of the migration/modelling operator bring limitations. In this abstract I discuss some of these limitations, possible ways to overcome them, and analyse some similarities and differences with respect to interpolation. Also I present results using a LSM implementation for Kirchhoff Depth Migration for both PP and PS data.
Lowrank RTM for converted wave imagingLowrank RTM for converted wave imaging
CSEG - Canadian Society of Exploration Geophysicists, 2015
Lorenzo Casasanta | Zhiguang Xue | Sam Gray
©2015 CGG
Summary
Although wavefield extrapolation techniques are well developed for P-wave seismic imaging, ray based migration algorithms are still the workhorse for converted-wave (PS-wave) depth imaging. Full (exact) elastic-wave reverse-time anisotropic migration (RTM) has not been widely adopted for reasons of computational and workflow efficiency, despite its potential to deliver accurate sub-surface images in complex geological settings by directly solving the elastic wave equation. Even (approximate) converted-wave RTM in anisotropic media, using separate finite-difference propagators for quasi-P and quasi-S waves, is limited in applicability for algorithmic reasons. Here, we introduce an alternative converted-wave anisotropic RTM, using a low-rank decomposition of mixed-domain space-wavenumber propagators for quasi-P and quasi-S waves. These operators are formal integral solutions of the pure-mode wave equations which guarantee stable and dispersion-free time extrapolation for coarse time steps in anisotropic, heterogeneous media. The pure-mode extrapolators are attractive for both PS-wave structural imaging and velocity analysis. An ocean bottom cable synthetic example illustrates the effectiveness of low-rank PS-wave RTM when compared against state-of-the-art Gaussian beam and finite difference RTM algorithms.
A deblending strategy using alternating constant delay simultaneous source dataA deblending strategy using alternating constant delay simultaneous source data
SEG - Society of Exploration Geophysicists, 2014
Gordon Poole | Damien Russier | Kent Stevens | Thomas Mensch | Risto Siliqi
©2014 SEG
Summary
This paper introduces a deblending strategy for simultaneous source data acquired using alternating constant delays. The technique uses uncontaminated data to generate a cross-talk noise estimate for deblending. The effectiveness of the strategy is demonstrated on a broadband dual source marine dataset acquired offshore Indonesia.
A new parameterization for anisotropy update in full waveform inversionA new parameterization for anisotropy update in full waveform inversion
SEG - Society of Exploration Geophysicists, 2014
Nuno Vieira Da Silva | Andrew Ratcliffe | Graham Conroy | Vetle Vinje | Geoff Body
©2014 SEG
Summary
Full Waveform Inversion (FWI) is now used regularly by the industry to update velocity models. These algorithms often take into account anisotropy but do not update it. We introduce a set of parameters, new in the scope of FWI, which have better orthogonal properties in comparison to other equivalent sets. This was done in an attempt to mitigate the existing ambiguity when jointly estimating anisotropy and velocity from FWI. After demonstrating the properties of this new parameter set, a practical application to a North Sea field dataset is then presented. Our FWI result reveals interesting velocity and anisotropy details associated with features in the near surface geology; an associated improvement in the seismic image is also observed.
Acquiring and Imaging Ultra High Density Land Seismic Data - Practical Challenges and the Impact of Spatial SamplingAcquiring and Imaging Ultra High Density Land Seismic Data - Practical Challenges and the Impact of Spatial Sampling
EAGE - European Association of Geoscientists and Engineers, 2014
A. Ourabah | M. Grimshaw | J. Keggin | M. Kowalczyk-Kedzierska | J. Stone | E. Murray | S. Cooper | L.Shaw
©2014 EAGE
Summary
In this presentation we take an ultra-high fold test dataset and decimate to simulate 20 different acquisition sub-sets. By carefully designing a processing sequence to process the data consistently between the datasets, it is possible to understand how shot and receiver sampling for each configuration affects processes such as noise attenuation, surface-consistent processing, velocities, the final imaging and attributes.
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