Study of the leaking channel modes of in‐seam exploration seismology by means of synthetic seismograms

Geophysics ◽  
1985 ◽  
Vol 50 (3) ◽  
pp. 414-424 ◽  
Author(s):  
G. R. Franssens ◽  
P. E. Lagasse ◽  
I. M. Mason
Keyword(s):  
Seismic Data ◽  
Numerical Evaluation ◽  
Fourier Integral ◽  
Synthetic Seismograms ◽  
Dispersion Characteristics ◽  
Mode Dispersion ◽  
Period Equation ◽  
Exploration Seismology ◽  
Channel Mode ◽  
Layered Models

If the dispersion characteristics of coal‐seam channel guides do not extend smoothly at frequencies below cut‐off, the number of parameters required to process inseam seismic data increases. Unwanted modes become more difficult to suppress, the arriving pulses from targets become more difficult both to identify and to pulse compress. The connection between leaking and normal channel mode dispersion is established here by first synthesizing and then analyzing theoretical in‐seam seismograms. Calculation of synthetic seismograms is based on numerical evaluation of the spatial Fourier integral for elastic displacements in the complex wavenumber plane. Theoretical seismograms are presented for three‐layered models. Phase velocity characteristics are recovered from these signals and compared with those obtained from the zero loci of the period equation in the complex wavenumber plane. Under cut‐off the former method yields smooth extensions of the normal mode dispersion characteristics, in contrast to the velocity curves obtained from the period equation only. It is found that the dispersion characteristics obtained from analyzing the seismograms can be used to recompress the dispersed arrivals.

Honoring volunteers and sharing knowledge on the SEG Wiki

2019 ◽  
Vol 38 (1) ◽  
pp. 69-72 ◽  
Author(s):  
Andrew Geary
Keyword(s):  
Data Analysis ◽  
Seismic Data ◽  
The Public ◽  
Applied Geophysics ◽  
Exploration Seismology ◽  
Encyclopedic Dictionary

The SEG Wiki serves as a key foundation of the Society to engage the membership, the geoscience community, and the public in all-things applied geophysics. The wiki's main mission is to supply scientific material to the geoscience community and the public through online books, geophysical tutorials, geoscience articles, and biographies of geoscientists. SEG's two best-selling books are provided open and free of charge on the wiki. They include the Encyclopedic Dictionary of Applied Geophysics by Robert E. Sheriff and Seismic Data Analysis by Öz Yilmaz. A third book, Problems in Exploration Seismology and Their Solutions by L. P. Geldart and Robert E. Sheriff, will be added soon.

scholarly journals High-resolution coherency functionals for velocity analysis: An application for subbasalt seismic exploration

Geophysics ◽  
2013 ◽  
Vol 78 (5) ◽  
pp. U53-U63 ◽  
Author(s):  
Andrea Tognarelli ◽  
Eusebio Stucchi ◽  
Alessia Ravasio ◽  
Alfredo Mazzotti
Keyword(s):  
High Resolution ◽  
Seismic Data ◽  
Field Data ◽  
Signal To Noise Ratio ◽  
Synthetic Seismograms ◽  
Seismic Exploration ◽  
Velocity Analysis ◽  
Signal To Noise ◽  
Geologic Setting ◽  
Analytic Signals

We tested the properties of three different coherency functionals for the velocity analysis of seismic data relative to subbasalt exploration. We evaluated the performance of the standard semblance algorithm and two high-resolution coherency functionals based on the use of analytic signals and of the covariance estimation along hyperbolic traveltime trajectories. Approximate knowledge of the wavelet was exploited to design appropriate filters that matched the primary reflections, thereby further improving the ability of the functionals to highlight the events of interest. The tests were carried out on two synthetic seismograms computed on models reproducing the geologic setting of basaltic intrusions and on common midpoint gathers from a 3D survey. Synthetic and field data had a very low signal-to-noise ratio, strong multiple contamination, and weak primary subbasalt signals. The results revealed that high-resolution coherency functionals were more suitable than semblance algorithms to detect primary signals and to distinguish them from multiples and other interfering events. This early discrimination between primaries and multiples could help to target specific signal enhancement and demultiple operations.

Use of seismic stratigraphy for Minnelusa exploration, northeastern Wyoming

Geophysics ◽  
1984 ◽  
Vol 49 (6) ◽  
pp. 715-721 ◽  
Author(s):  
Reverend Francis D. Raffalovich ◽  
Terrell B. Daw
Keyword(s):  
Seismic Data ◽  
Seismic Stratigraphy ◽  
Synthetic Seismograms ◽  
Powder River Basin ◽  
Paper Briefly ◽  
Seismic Attribute ◽  
Seismic Line ◽  
Processing Techniques ◽  
Sonic Logs ◽  
Section Form

While Minnelusa sands have yielded significant reserves in Wyoming’s Powder River Basin, geologic complexities have made these sands an elusive target. This paper briefly describes the development of a technique which was used successfully in the exploration of Minnelusa sands. This tehnique can be applied to many stratigraphic exploration programs. Sonic logs, which are key logs in defining Minnelusa sands, in the C-H field were used to construct synthetic seismograms. These synthetics were then organized in cross‐section form to define whether a change in Minnelusa sands would yield an identifiable change on the synthetics. The “idealized” seismic response did show an obvious lateral change from upper sand to no upper sand conditions, and a pilot seismic line was shot using a Vibroseis® source. This line, which was shot through the C-H field, successfully showed the updip limits of the upper Minnelusa sands. A subsequent seismic program was acquired and other leads and prospects were identified, including prospects that were drilled and successfully completed in the Rozet area. However, a number of other wells conformed to Murphy’s law. In addition to standard processing techniques, high‐resolution processing and seismic attribute processing was done on some of the seismic data, yielding differing degrees of success. By closely coordinating geologic and geophysical principles, a useful stratigraphic‐seismic methodology was developed which has application to a wide variety of exploration problems. ™Trade and service mark of Conoco Inc.

Full‐waveform processing and interpretation of kilohertz cross‐well seismic data

Geophysics ◽  
1993 ◽  
Vol 58 (9) ◽  
pp. 1248-1256 ◽  
Author(s):  
Ashraf A. Khalil ◽  
Robert R. Stewart ◽  
David C. Henley
Keyword(s):  
Oil Recovery ◽  
Seismic Data ◽  
Shear Waves ◽  
Synthetic Seismograms ◽  
Oil Field ◽  
S Wave ◽  
Sonic Log ◽  
The Cross ◽  
Interval Velocities ◽  
The Individual

High‐frequency, cross‐well seismic data, from the Midale oil field of southeastern Saskatchewan, are analyzed for direct and reflected energy. The goal of the analysis is to produce interpretable sections to assist in enhanced oil recovery activities ([Formula: see text] injection) in this field. Direct arrivals are used for velocity information while reflected arrivals are processed into a reflection image. Raw field data show a complex assortment of wave types that includes direct compressional and shear waves and reflected shear waves. A traveltime inversion technique (layer stripping via ray tracing) is used to obtain P‐ and S‐wave interval velocities from the respective direct arrivals. The velocities from the cross‐well inversion and the sonic log are in reasonable agreement. The subsurface coverage of the cross‐well geometry is investigated; it covers zones extending from the source well to the receiver well and includes regions above and below the source/receiver depths. Upgoing and downgoing primary reflections are processed, in a manner similar to the vertical seismic profiling/common‐depth‐point (VSP/CDP) map, to construct the cross‐well images. A final section is produced by summing the individual reflection images from each receiver‐gather map. This section provides an image with evidence of strata thicknesses down to about 1 m. Synthetic seismograms are used to interpret the final sections. Correlations can be drawn between some of the events on the synthetic seismograms and the cross‐well image.

Reflectivity randomness revisited

Geophysics ◽  
1999 ◽  
Vol 64 (5) ◽  
pp. 1630-1636 ◽  
Author(s):  
Ayon K. Dey ◽  
Larry R. Lines
Keyword(s):  
Seismic Data ◽  
Real Data ◽  
Seismic Profile ◽  
Synthetic Seismograms ◽  
Seismic Exploration ◽  
Well Log ◽  
Simple Test ◽  
Vertical Seismic Profile ◽  
Seismic Reflectivity

In seismic exploration, statistical wavelet estimation and deconvolution are standard tools. Both of these processes assume randomness in the seismic reflectivity sequence. The validity of this assumption is examined by using well‐log synthetic seismograms and by using a procedure for evaluating the resulting deconvolutions. With real data, we compare our wavelet estimations with the in‐situ recording of the wavelet from a vertical seismic profile (VSP). As a result of our examination of the randomness assumption, we present a fairly simple test that can be used to evaluate the validity of a randomness assumption. From our test of seismic data in Alberta, we conclude that the assumption of reflectivity randomness is less of a problem in deconvolution than other assumptions such as phase and stationarity.

Wrap‐around removal from one‐dimensional synthetic seismograms

Geophysics ◽  
1989 ◽  
Vol 54 (7) ◽  
pp. 911-915 ◽  
Author(s):  
Hans Thybo
Keyword(s):  
Frequency Domain ◽  
Computational Methods ◽  
Time Domain ◽  
Synthetic Seismograms ◽  
Seismic Exploration ◽  
One Dimensional ◽  
Borehole Logs ◽  
The Time Domain ◽  
Layered Models

One‐dimensional (1-D) synthetic seismograms are important tools in seismic exploration. They play an important role in the correlation of recorded seismograms with borehole logs and also permit the estimation of delay‐type attenuation in finely layered models. Existing computational methods for computing 1-D seismograms can be grouped according to whether the calculations are performed in the time domain or in the frequency domain.

scholarly journals Synthetic seismograms through synthetic Franciscan: Insights into factors affecting large-aperture seismic data

1997 ◽  
Vol 24 (24) ◽  
pp. 3317-3320 ◽  
Author(s):  
Christof Lendl ◽  
Anne M. Tréhu ◽  
John A. Goff ◽  
Alan R. Levander ◽  
Bruce C. Beaudoin
Keyword(s):  
Seismic Data ◽  
Synthetic Seismograms ◽  
Factors Affecting ◽  
Large Aperture
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