Generation and processing of pseudo‐shear‐wave data: Theory and case study

Grechka, Vladimir; Dewangan, P.

doi:10.1190/1.1635033

Cited by 29 publications

(47 citation statements)

References 8 publications

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“…It is important to distinguish the pseudo S-wave response here with the pseudo shear-wave response of the PP + PS = SS method (denoted as S-wave) described by Grechka and Dewangan (2003). It is important to distinguish the pseudo S-wave response here with the pseudo shear-wave response of the PP + PS = SS method (denoted as S-wave) described by Grechka and Dewangan (2003).…”

Section: Discussionmentioning

confidence: 99%

Pseudo S-wave broadband response of C-waves after domain change

Gaiser¹,

Verm²,

Chaveste³

2013

The Leading Edge

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Pseudo S-wave broadband response of C-waves after domain change T ransforming multicomponent data from one domain to another has long been an important tool for interpretation, V P /V S analysis and joint amplitude versus offset/angle AVO/AVA inversion. Recent interest in the dynamics of these domain changes has led to investigations in wavelet distortion and correction methods for improved inversion and bandwidth for well ties (Bansal and Matheney, 2010;Gaiser, 2011;and Ursenbach et al., 2012). In this article, we derive corrections for converted P-to S-waves (C-waves), to match their effective wavelengths with the physical wavelengths of S-waves, in P-wave time or depth. We call this a pseudo S-wave response. Although bandwidth is broadened, these corrections do not completely retrieve the resolution benefits of shorter wavelength S-waves.Implementation of these corrections has several key elements similar to Bansal and Matheney (2010): estimation of an interval V P /V S function, performing zero phase corrections and applying wavelet corrections using nonstationary wavelet filters (Margrave, 1998). Application of our technique to a 3D multicomponent data set acquired over the Marcellus shale provides broader bandwidth C-waves that match P-wave data and reveal improved well ties in the reservoir.

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Section: Discussionmentioning

confidence: 99%

Pseudo S-wave broadband response of C-waves after domain change

Gaiser¹,

Verm²,

Chaveste³

2013

The Leading Edge

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“…A "full-waveform" version of the PP+PS=SS method based on equation 2.4 was developed by Grechka & Dewangan (2003). They Figure 2.2: Matching the horizontal slownesses on common-receiver PP and PS sections at locations x 1 and x 2 helps find the source-receiver coordinates x 3 and x 4 of the pure SS ray x 3 Rx 4 .…”

Section: Implementation Of the Pp+ps=ss Methodsmentioning

confidence: 99%

Joint migration velocity analysis of PP- and PS-waves for VTI media

Cai

Tsvankin

2013

GEOPHYSICS

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Combining PP-waves with mode-converted PS reflections in migration velocity analysis (MVA) can help build more accurate VTI (transversely isotropic with a vertical symmetry axis) velocity models. To avoid problems caused by the moveout asymmetry of PS-waves and take advantage of efficient MVA algorithms designed for pure modes, I suggest to generate pure SS-reflections from PP and PS data using the PP+PS=SS method. Then the residual moveout in both PP and SS commonimage gathers is minimized during iterative velocity updates. The model is divided into square cells, and the VTI parameters V P 0 , V S0 , , and δ are defined at each grid point. The objective function also includes the differences between the migrated depths of the same reflectors on the PP and SS sections and a regularization term.Synthetic examples confirm that 2D MVA of PP-and PS-waves may be able to resolve all four relevant parameters of VTI media if reflectors with at least two distinct dips are available. The algorithm is also applied to a 2D line from 3D OBS (ocean bottom seismic) data acquired at Volve field in the North Sea. After the anisotropic velocity model has been reconstructed, accurate depth images can be obtained by migrating the recorded PP and PS data.

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“…Publications: , Grechka and Dewangan (2003) (see the list of publications). A presentation based on these results was recognized as one of the best papers at the Annual Meeting of the Society of Exploration Geophysicists (SEG) in San Antonio (2001).…”

Section: New Methods For Processing and Inversion Of Multicomponent Sementioning

confidence: 99%

“…Although the joint inversion of the PP and SS data did not produce a unique result, we were able to map the effective anisotropic parameter χ constrained by the ratios of the NMO velocities and vertical traveltimes of the PP-and SS-waves. Publications: Grechka, Tsvankin, et al (2002a,b), Grechka and Dewangan (2003).…”

Section: Application Of Anisotropic Velocity Analysis To Multicomponementioning

confidence: 99%

“…3. The portion of PS data in the vicinity of the polarity reversal (where the PS amplitudes are small) can be muted out without compromising the processing results.Publications: , Grechka and Dewangan (2003) (see the list of publications). A presentation based on these results was recognized as one of the best papers at the Annual Meeting of the Society of Exploration Geophysicists (SEG) in San Antonio (2001).…”

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Inversion of multicomponent seismic data and rock-physics intepretation for evaluating lithology, fracture and fluid distribution in heterogeneous anisotropic reservoirs

Tsvankin¹,

Larner²

2004

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, the deliverables include algorithms and codes for processing and inversion of multicomponent seismic data in anisotropic media and for modeling of seismic signatures of fracture systems. Most of this software is available from CWP as part of Seismic Unix (SU) -a package of programs for Unix-based machines. SUMMARY OF RESEARCH RESULTS New method for processing and inversion of multicomponent seismic dataDue to the high cost of shear-wave excitation, the difficulty of placing sources on the sea floor, and often poor quality of SS-wave data, it has become a practice in reflection seismology to replace pure SS reflections with mode-converted PS-waves. Converted waves are of particular importance in offshore seismic, where they represent the only available type of shear energy. For a number of exploration scenarios, PS-waves provide valuable information about the subsurface structure and anisotropic medium parameters that cannot be inferred from conventional PP-wave data. Kinematics and waveforms of reflected PS-waves, however, possess such undesirable features as moveout asymmetry, reflection point dispersal and polarity reversal, which preclude application of conventional velocity-analysis methods to mode conversions.Rather than using PS-waves directly, we developed a method for constructing SSwave reflections (if they are not physically excited in the survey) from PP and PS data. The original version of this technique ) is based on picking of PP and PS traveltimes on prestack data and identification (correlation) of the PP and PS events from the same interfaces. The key idea of the method is to match the reflection slopes (horizontal slownesses) on common-receiver PP and PS gathers. This matching allows us to find the coordinates of receivers that record PPand PS-waves reflected at exactly the same (albeit unknown) subsurface points and to determine the traveltime of the SS primary reflection as a simple combination of the PP and PS times. The constructed SS-wave moveout can then be processed by velocity-analysis methods designed for pure reflection modes (see below).To avoid traveltime picking on prestack data, we generalized the above algorithm (often called the "PP+PS=SS" method) to operate directly with recorded traces of PP-and PS-waves (Grechka and Dewangan, 2003). By designing a special convolution of PP-and PS-wave seismograms, it is possible to compute full-waveform SS data well-suited for moveout inversion and, potentially, for AVO (amplitude variation with offset) analysis.The PP+PS=SS method has the following attractive features: 1. Although it is necessary to establish correlation between the PP and PS sections, no information about the velocity field or anisotropic parameters is required to obtain SS-waves with the correct kinematics from the PP and PS data. 2. The moveout of the output SS-waves is symmetric with respect to zero offset and can be processed by algorithms designed for pure-mode reflections. 3. The reflection-point dispersal of PS-waves has no influence on the generated SS data. 3....

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Generation and processing of pseudo‐shear‐wave data: Theory and case study

Cited by 29 publications

References 8 publications

Pseudo S-wave broadband response of C-waves after domain change

Pseudo S-wave broadband response of C-waves after domain change

Joint migration velocity analysis of PP- and PS-waves for VTI media

Inversion of multicomponent seismic data and rock-physics intepretation for evaluating lithology, fracture and fluid distribution in heterogeneous anisotropic reservoirs

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