Frequency-dependent reflection wave-equation traveltime inversion from walkaway vertical seismic profile data

To accurately image the geologic structures from walkaway vertical seismic profile (VSP) data, it is necessary to estimate the subsurface velocity field with high resolution and enhanced illumination of deep reservoirs. Because full-waveform inversion (FWI) suffers from cycle skipping when the initial model is far from the true model, we have adopted frequency-dependent reflection wave-equation traveltime inversion (FRWT) to generate the background velocity model for VSP migration. The upgoing reflection data are separated from the original shot gathers, and dynamic warping is used to evaluate the traveltime differences between the observed data and the calculated data. Different frequency bands of the data are inverted in sequence to reconstruct the velocity model with higher resolution. We also implement wavefield decomposition on the gradient field to extract the contributions of reflection components and improve the updated model. The inverted results obtained from FRWT can be used as the initial model for conventional FWI or the velocity model for reverse time migration. The experiments on synthetic data and field data demonstrate that our approach can effectively recover the background velocity model from walkaway VSP data.

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Integrated prestack depth migration of vertical seismic profile and surface seismic data from the Rocky Mountain Foothills of southern Alberta, Canada

Geophysics ◽

10.1190/1.1635031 ◽

2003 ◽

Vol 68 (6) ◽

pp. 1782-1791 ◽

Cited By ~ 1

Author(s):

M. Graziella Kirtland Grech ◽

Don C. Lawton ◽

Scott Cheadle

Keyword(s):

Seismic Data ◽

Rocky Mountain ◽

Velocity Model ◽

Seismic Profile ◽

Vertical Seismic Profile ◽

Prestack Depth Migration ◽

Data Set ◽

Depth Migration ◽

Southern Alberta ◽

Vsp Data

We have developed an anisotropic prestack depth migration code that can migrate either vertical seismic profile (VSP) or surface seismic data. We use this migration code in a new method for integrated VSP and surface seismic depth imaging. Instead of splicing the VSP image into the section derived from surface seismic data, we use the same migration algorithm and a single velocity model to migrate both data sets to a common output grid. We then scale and sum the two images to yield one integrated depth‐migrated section. After testing this method on synthetic surface seismic and VSP data, we applied it to field data from a 2D surface seismic line and a multioffset VSP from the Rocky Mountain Foothills of southern Alberta, Canada. Our results show that the resulting integrated image exhibits significant improvement over that obtained from (a) the migration of either data set alone or (b) the conventional splicing approach. The integrated image uses the broader frequency bandwidth of the VSP data to provide higher vertical resolution than the migration of the surface seismic data. The integrated image also shows enhanced structural detail, since no part of the surface seismic section is eliminated, and good event continuity through the use of a single migration–velocity model, obtained by an integrated interpretation of borehole and surface seismic data. This enhanced migrated image enabled us to perform a more robust interpretation with good well ties.

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Salt-flank delineation by interferometric imaging of transmitted P- to S-waves

Geophysics ◽

10.1190/1.2209550 ◽

2006 ◽

Vol 71 (4) ◽

pp. SI197-SI207 ◽

Cited By ~ 25

Author(s):

Xiang Xiao ◽

Min Zhou ◽

Gerard T. Schuster

Keyword(s):

Velocity Model ◽

Seismic Profile ◽

Migration Velocity ◽

Interferometric Imaging ◽

S Waves ◽

Time Migration ◽

Transmitted Waves ◽

Imaging Results ◽

Vsp Data ◽

Migration Method

We describe how vertical seismic profile (VSP) interferometric imaging of transmitted P-to-S (PS) waves can be used to delineate the flanks of salt bodies. Unlike traditional migration methods, interferometric PS imaging does not require the migration velocity model of the salt and/or upper sediments in order to image the salt flank. Synthetic elastic examples show that PS interferometric imaging can clearly delineate the upper and lower boundaries of a realistic salt-body model. Results also show that PS interferometric imaging is noticeably more accurate than conventional migration methods in the presence of static shifts and/or migration velocity errors. However, the illumination area of the PS transmitted waves is limited by the width of the shot and geophone aperture, which means wide shot offsets and deeper receiver wells are needed for comprehensive salt-flank imaging. Interferometric imaging results for VSP data from the Gulf of Mexico demonstrate its superiority over the traditional migration method. We also discuss other arrivals that can be used for interferometric imaging of salt flanks. For comparison, reduced-time migration results are presented, which are similar in quality to those obtained for interferometric imaging. We conclude that PS interferometric imaging of VSP data provides the geophysicist with a new tool by which salt flanks can be viewed from both above and below VSP geophone locations.

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Dual-well 3D vertical seismic profile enabled by distributed acoustic sensing in deepwater Gulf of Mexico

Interpretation ◽

10.1190/int-2014-0248.1 ◽

2015 ◽

Vol 3 (3) ◽

pp. SW11-SW25 ◽

Cited By ~ 22

Author(s):

Han Wu ◽

Wai-Fan Wong ◽

Zhaohui Yang ◽

Peter B. Wills ◽

Jorge L. Lopez ◽

...

Keyword(s):

Gulf Of Mexico ◽

Velocity Model ◽

Seismic Profile ◽

Seismic Survey ◽

Vertical Seismic Profile ◽

Acoustic Sensing ◽

Velocity Models ◽

Vsp Data ◽

Distributed Acoustic Sensing

We have acquired and processed 3D vertical seismic profile (VSP) data recorded simultaneously in two wells using distributed acoustic sensing (DAS) during the acquisition of the 2012 Mars 4D ocean-bottom seismic survey in the deepwater Gulf of Mexico. The objectives of the project were to assess the quality of DAS data recorded in fiber-optic cables from the surface to the total depth, to demonstrate the efficacy of the DAS VSP technology in a deepwater environment, to derisk the use of the technology for future water injection or production monitoring without intervention, and to exploit the velocity information that 3D VSP data provide for evaluating and updating the velocity model. We evaluated the advantages of DAS VSP to reduce costs and intrusiveness, and we determined that high-quality images can be obtained from relatively noisy raw 3D DAS VSP data, as evidenced by the well 1 image, probably the best 3D VSP image we have ever seen. Our results also revealed that the direct arrival traveltimes can be used to assess the quality of an existing velocity model and to invert for an improved velocity model. We identified issues with the DAS acquisition and the processing steps to mitigate them and to handle problems specific to DAS VSP data. We described the steps for conditioning the data before migration, reverse time migration, and postmigration processing to reduce noise artifacts. We outlined a novel first-break picking procedure that works even in the absence of a strong first arrival and a velocity diagnosis method to assess and validate velocity models and velocity updates. Finally, we determined potential applications to 4D monitoring of fluid movement around producer or injector wells, identification of active salt movements, and more accurate imaging and monitoring of complex structures around the wells.

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Local migration with extrapolated VSP Green’s functions

Geophysics ◽

10.1190/1.3026619 ◽

2009 ◽

Vol 74 (1) ◽

pp. SI15-SI26 ◽

Cited By ~ 14

Author(s):

Xiang Xiao ◽

Gerard T. Schuster

Keyword(s):

Velocity Model ◽

Seismic Profile ◽

Imaging Method ◽

Local Velocity ◽

Dynamic Effects ◽

Vertical Seismic Profile ◽

Data Set ◽

Numerical Tests ◽

Vsp Data ◽

Backward Propagation

We have developed a novel vertical seismic profile (VSP) imaging method that requires only a local velocity model around the well. This method is denoted as a “local migration,” where the model-based forward-propagation and backward-propagation operators are computed using a local velocity model between the well and the target body. The velocity model for the complex overburden and salt body is not needed, and the source-side statics are automatically accounted for. In addition, kinematic and dynamic effects, including anisotropy, absorption, and other unknown/undefined rock effects outside of this local velocity model, are mostly accounted for. Numerical tests on an acoustic 2D Sigsbee VSP data set, an elastic salt model, and offset 2D VSP data in the Gulf of Mexico partly validate the effectiveness of this method by accurately imaging the sediments next to the vertical well.

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Determination of salt proximity by wave‐field imaging of transmitted energy

Geophysics ◽

10.1190/1.1442547 ◽

1988 ◽

Vol 53 (8) ◽

pp. 1109-1112 ◽

Cited By ~ 6

Author(s):

George A. McMechan ◽

Liang‐Zie Hu ◽

Douglas Stauber

Keyword(s):

Acoustic Waves ◽

Seismic Profile ◽

Reverse Time ◽

Reverse Time Migration ◽

Vertical Seismic Profile ◽

Wave Fields ◽

Time Migration ◽

Vsp Data ◽

Field Imaging

Prestack reverse‐time migration for acoustic waves has recently been developed for vertical seismic profile (VSP) data (Chang and McMechan, 1986) and for cross‐hole (CH) data (Hu et al., 1988). Both sets of authors use the same migration software and produce images from the scattered (reflected and diffracted) energy in the recorded wave fields.

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Traveltime inversion of both direct and reflected arrivals in vertical seismic profile data

Geophysics ◽

10.1190/1.1442576 ◽

1989 ◽

Vol 54 (1) ◽

pp. 49-56 ◽

Cited By ~ 9

Author(s):

Edward L. Salo ◽

Gerard T. Schuster

Keyword(s):

Least Squares ◽

Velocity Structure ◽

Seismic Profile ◽

Profile Data ◽

Vertical Seismic Profile ◽

Data Set ◽

Traveltime Inversion ◽

Sonic Log ◽

Vsp Data

Traveltimes from both direct and reflected arrivals in a VSP data set (Bridenstein no. 1 well in Oklahoma) are inverted in a least‐squares sense for velocity structure. By comparing the structure from inversion to the sonic log, we conclude that the accuracy of the reconstructed velocities is greater than that found when only the direct arrivals are used. Extensive tests on synthetic VSP data confirm this observation. Apparently, the additional reflection traveltime equations aid in averaging out the traveltime errors, as well as reducing the slowness variance in reflecting layers. These results are consistent with theory, which predicts a decrease in a layer’s slowness variance with an increase in the number and length of terminating reflected rays. For the Bridenstein data set, 130 direct traveltimes and 399 primary reflection traveltimes were used in the inversion.

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Q estimation from vertical seismic profile data and anomalous variations in the central North Sea

Geophysics ◽

10.1190/1.1441937 ◽

1985 ◽

Vol 50 (4) ◽

pp. 615-626 ◽

Cited By ~ 54

Author(s):

S. D. Stainsby ◽

M. H. Worthington

Keyword(s):

North Sea ◽

Pulse Width ◽

Spectral Ratio ◽

Seismic Profile ◽

Seismic Attenuation ◽

Recording Equipment ◽

Vertical Seismic Profile ◽

High Attenuation ◽

Vsp Data ◽

Central North Sea

Four different methods of estimating Q from vertical seismic profile (VSP) data based on measurements of spectral ratios, pulse amplitude, pulse width, and zeroth lag autocorrelation of the attenuated impulse are described. The last procedure is referred to as the pulse‐power method. Practical problems concerning nonlinearity in the estimating procedures, uncertainties in the gain setting of the recording equipment, and the influence of structure are considered in detail. VSP data recorded in a well in the central North Sea were processed to obtain estimates of seismic attenuation. These data revealed a zone of high attenuation from approximately 4 900 ft to [Formula: see text] ft with a value of [Formula: see text] Results of the spectral‐ratio analysis show that the data conform to a linear constant Q model. In addition, since the pulse‐width measurement is dependent upon the dispersive model adopted, it is shown that a nondispersive model cannot possibly provide a match to the real data. No unambiguous evidence is presented that explains the cause of this low Q zone. However, it is tentatively concluded that the seismic attenuation may be associated with the degree of compaction of the sediments and the presence of deabsorbed gases.

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Specular interferometric imaging of vertical seismic profile data

Interpretation ◽

10.1190/int-2014-0251.1 ◽

2015 ◽

Vol 3 (3) ◽

pp. SW57-SW62 ◽

Cited By ~ 3

Author(s):

Yunsong Huang ◽

Ruiqing He ◽

Chaiwoot Boonyasiriwat ◽

Yi Luo ◽

Gerard Schuster

Keyword(s):

Ray Tracing ◽

Field Data ◽

Seismic Profile ◽

The Other ◽

Interferometric Imaging ◽

Profile Data ◽

Vertical Seismic Profile ◽

Ghost Image ◽

Primary Image ◽

Vsp Data

We introduce the concept of seminatural migration of multiples in vertical seismic profile (VSP) data, denoted as specular interferometric migration, in which part of the kernel is computed by ray tracing and the other part is obtained from the data. It has the advantage over standard migration of ghost reflections, in that the well statics are eliminated and the migration image is no more sensitive to velocity errors than migration of VSP primaries. Moreover, the VSP ghost image has significantly more subsurface illumination than the VSP primary image. The synthetic and field data results validate the effectiveness of this method.

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PRACTICAL USE OF BOREHOLE SEISMIC IN EXPLORATION

The APPEA Journal ◽

10.1071/aj83034 ◽

1984 ◽

Vol 24 (1) ◽

pp. 429

Author(s):

F. Sandnes W. L. Nutt ◽

S. G. Henry

Keyword(s):

Seismic Data ◽

Seismic Profile ◽

Seismic Survey ◽

Vertical Seismic Profile ◽

Direct Signal ◽

Seismic Fault ◽

Time Calibration ◽

Vsp Data ◽

Borehole Seismic ◽

Processing Techniques

The improvement of acquisition and processing techniques has made it possible to study seismic wavetrains in boreholes.With careful acquisition procedures and quantitative data processing, one can extract useful information on the propagation of seismic events through the earth, on generation of multiples and on the different reflections coming from horizons that may not all be accessible by surface seismic.An extensive borehole seismic survey was conducted in a well in Conoco's contract area 'Block B' in the South China Sea. Shots at 96 levels were recorded, and the resulting Vertical Seismic Profile (VSP) was carefully processed and analyzed together with the Synthetic Seismogram (Geogram*) and the Synthetic Vertical Seismic Profile (Synthetic VSP).In addition to the general interpretation of the VSP data, i.e. time calibration of surface seismic, fault identification, VSP trace inversion and VSP Direct Signal Analysis, the practical inclusion of VSP data in the reprocessing of surface seismic data was studied. Conclusions that can be drawn are that deconvolution of surface seismic data using VSP data must be carefully approached and that VSP can be successfully used to examine phase relationships in seismic data.

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Vertical seismic profile migration using the Kirchhoff integral

Geophysics ◽

10.1190/1.1442514 ◽

1988 ◽

Vol 53 (6) ◽

pp. 786-799 ◽

Cited By ~ 28

Author(s):

P. B. Dillon

Keyword(s):

Wave Equation ◽

Wave Field ◽

Near Field ◽

Synthetic Data ◽

Real Data ◽

Seismic Profile ◽

Processing Strategies ◽

Receiver Array ◽

Vsp Data ◽

Kirchhoff Integral

Wave‐equation migration can form an accurate image of the subsurface from suitable VSP data. The image’s extent and resolution are determined by the receiver array dimensions and the source location(s). Experiments with synthetic and real data show that the region of reliable image extent is defined by the specular “zone of illumination.” Migration is achieved through wave‐field extrapolation, subject to an imaging procedure. Wave‐field extrapolation is based upon the scalar wave equation and, for VSP data, is conveniently handled by the Kirchhoff integral. The migration of VSP data calls for imaging very close to the borehole, as well as imaging in the far field. This dual requirement is met by retaining the near‐field term of the integral. The complete integral solution is readily controlled by various weighting devices and processing strategies, whose worth is demonstrated on real and synthetic data.

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