VSP CASE HISTORY, KANPA 1A, THE WESTERN OFFICER BASIN

1985 ◽  
Vol 25 (1) ◽  
pp. 254
Author(s):  
T.J.C. Prudence ◽  
J. Flentri
Keyword(s):  
Seismic Profile ◽  
Field Configuration ◽  
Synthetic Seismogram ◽  
Target Interval ◽  
Seismic Section ◽  
Temporal Sampling ◽  
Consistent Field ◽  
Vsp Data ◽  
Tube Wave ◽  
Zero Phase

The Kanpa 1A Vertical Seismic Profile (VSP) was conducted for Shell by Schlumberger and incorporated variable time and depth sampling, different source offsets and recording in cased and uncased hole. Processing was performed using Shell proprietary programs, with particular attention to:Editing and resampling of the data setSeparation of upgoing and downgoing waves using FK and median filtersComparison of gain recovery based on modelling the amplitude decay of direct arrivals with an averaging process (AGC)Sensitivity of the final VSP stack to blanking of residual tube wave noiseZero-phase whitening of the VSP traceStacked VSP traces for Kanpa 1A were compared with a zero-phase seismic section and synthetic seismogram at the well. The VSP/seismic match is good and, due to poor synthetic/seismic correlation, was the basis for the final seismic/well tie. Interpretation of deep VSP data enabled the estimation of formation boundaries below the total depth of the well.It is concluded that VSPs can be invaluable in establishing well ties where seismic is poor or when detailed correlation is required (e.g. stratigraphic traps). Reflectors "ahead of the bit" can be interpreted from VSPs based on assumed velocities and VSP/seismic tie, and the predicted thickness and seismic character of the target interval. A consistent field configuration is recommended for acquisition with attention to tube wave suppression and adequate spatial and temporal sampling. Previous processing experience is advantageous if quick and reliable VSP results are required for decisions while drilling.

Synthetic vertical seismic profile

Geophysics ◽  
1981 ◽  
Vol 46 (6) ◽  
pp. 880-891 ◽  
Author(s):  
K. Dautenhahn Wyatt
Keyword(s):  
Seismic Profile ◽  
Synthetic Seismogram ◽  
Domain Model ◽  
Vertical Seismic Profile ◽  
Seismic Section ◽  
The Earth ◽  
Sonic Log ◽  
Wave Propagation Problem ◽  
Layering Effect ◽  
Insight Into

A time‐domain model has been developed for calculation of a synthetic vertical seismic profile (SVSP) from a sonic log recorded in a borehole. The SVSP has proven to be extremely useful in the interpretation of seismic data since it allows the interpreter to analyze the propagation of the source pulse through the earth in depth as well as time. Previously, the synthetic seismogram technique allowed analysis of the earth’s response to the source pulse at the surface only. However, the development of the SVSP allows insight into the entire wave propagation problem since the calculation shows the response of the earth to the source pulse at any depth point in the subsurface. For example, the synthetic seismogram can be used to identify an event on the seismic section as a multiple, whereas, the SVSP cannot only identify a multiple, but can also show which path the source pulse took through the earth layers to create the multiple. The SVSP can also be used to analyze the change in character of the source pulse due to the layering effect of the earth, for example, effects of a thin bed sequence; to study amplitude variations due to transmission losses; and to examine the effects of different source pulse bandwidths on the final surface seismogram, etc. As interpreters gain experience in analyzing the SVSP, many more applications are expected to appear.

scholarly journals Experimental testing of semirigid corrugated baffles for the suppression of tube waves in vertical seismic profile data

Geophysics ◽  
2019 ◽  
Vol 84 (3) ◽  
pp. D131-D149 ◽  
Author(s):  
Andrew Greenwood ◽  
J. Christian Dupuis ◽  
Anton Kepic ◽  
Milovan Urosevic
Keyword(s):  
Wave Attenuation ◽  
Experimental Testing ◽  
Low Cost ◽  
High Amplitude ◽  
Seismic Profile ◽  
Vertical Seismic Profile ◽  
Vsp Data ◽  
Scale Experiment ◽  
Tube Wave ◽  
The Cost

Multichannel borehole hydrophone strings are a low-cost, low-risk, alternative to borehole clamping geophones. Vertical seismic profile (VSP) data collected with hydrophones, however, suffer from high-amplitude coherent tube-wave noise. This reduces the usable data to the first arrivals and traveltimes for check-shot surveys. To significantly reduce tube-wave noise from VSP data acquired with hydrophones, we have designed and tested a novel tube-wave attenuation baffle. The effectiveness of the baffle was first verified in a laboratory-scale experiment and then in a borehole drilled into a hardrock environment. The laboratory experiments tested the performance of four different baffle topologies, whereby the best performing topology was the semirigid corrugated pipe baffle. This design reduced the amplitude of the tube wave with more than 40 dB and was logistically easy to deploy. The field experiment investigated the effectiveness of three different semirigid corrugated pipe baffle topologies in a PQ (123 mm) diamond drillhole in Western Australia. Here, we found that the semirigid corrugated pipe baffle was effective in disrupting tube-wave propagation. The 100 mm diameter baffle achieved an impressive 60 dB of tube-wave attenuation, whereas the 50 mm baffle had a modest attenuation of 10–15 dB. This suggests that the performance of this new type of baffle is best when the diameter of the baffle is closely matched to the diameter of the borehole. The results of these experiments have significant implications because hydrophone arrays with a large number of receivers are comparatively inexpensive and simpler to deploy than borehole geophone counterparts. The development of hydrophone arrays that are free of interfering borehole modes could allow VSPs to be acquired in situations in which seismic-polarity information is not required and could help VSP gain traction in cases in which the cost of acquisition has precluded its use until now.

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

Geophysics ◽  
1985 ◽  
Vol 50 (4) ◽  
pp. 615-626 ◽  
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.

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

Geophysics ◽  
2003 ◽  
Vol 68 (6) ◽  
pp. 1782-1791 ◽  
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.

Specular interferometric imaging of vertical seismic profile data

2015 ◽  
Vol 3 (3) ◽  
pp. SW57-SW62 ◽  
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.

PRACTICAL USE OF BOREHOLE SEISMIC IN EXPLORATION

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.

Vertical seismic profile migration using the Kirchhoff integral

Geophysics ◽  
1988 ◽  
Vol 53 (6) ◽  
pp. 786-799 ◽  
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.

Antialiasing condition and filter for the reciprocity equation of correlation type

Geophysics ◽  
2010 ◽  
Vol 75 (6) ◽  
pp. WB219-WB224 ◽  
Author(s):  
Weiping Cao ◽  
Gerard T. Schuster
Keyword(s):  
Seismic Data ◽  
Seismic Profile ◽  
Numerical Results ◽  
Numerical Implementation ◽  
Vertical Seismic Profile ◽  
Vsp Data ◽  
And Migration

An antialiasing formula has been derived for interferometric redatuming of seismic data. More generally, this formula is valid for numerical implementation of the reciprocity equation of correlation type, which is used for redatuming, extrapolation, interpolation, and migration. The antialiasing condition can be, surprisingly, more tolerant of a coarser trace sampling compared to the standard antialiasing condition. Numerical results with synthetic vertical seismic profile (VSP) data show that interferometry artifacts are effectively reduced when the antialiasing condition is used as a constraint with interferometric redatuming.

Automatic phase correction of common‐midpoint stacked data

Geophysics ◽  
1987 ◽  
Vol 52 (1) ◽  
pp. 51-59 ◽  
Author(s):  
S. Levy ◽  
D. W. Oldenburg
Keyword(s):  
Phase Correction ◽  
Well Logs ◽  
Seismic Section ◽  
Measured Velocity ◽  
Residual Phase ◽  
Automatic Phase ◽  
Frequency Independent ◽  
Independent Constant ◽  
Non Gaussian ◽  
Zero Phase

The residual wavelet on a processed seismic section is often not zero phase despite all efforts to make it so. In this paper we adopt the convolutional model for the processed seismogram, assume that the residual phase shift can be approximated by a frequency‐independent constant, and use the varimax norm to generate an algorithm to estimate the residual phase directly. Application of our algorithm to reflectivities from well logs suggests that it should work in the majority of cases so long as the reflectivity is non‐Gaussian. An application of our algorithm to stacked data enhances the interpretability of the seismic section and leads to an improved match between the recovered relative acoustic impedance and a measured velocity log.

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