PreviousNext No AccessGEOPHYSICSVolume 82, Issue 3Comment on: “Survey design for coal-scale 3D-PS seismic reflection” (S. Strong and S. Hearn, Geophysics, 81, no. 6, P57–P70)Authors: Gijs VermeerGijs Vermeer3DSymSam — Geophysical Advice, Voorschoten, The Netherlands. E-mail: .Search for more papers by this authorEmail the author at [email protected]https://doi.org/10.1190/geo2016-0709.1 SectionsAboutFull TextPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail REFERENCESStrong, S., and S. Hearn, 2016, Survey design for coal-scale 3D-PS seismic reflection: Geophysics, 81, no. 6, P57–P70, doi: 10.1190/geo2015-0560.1.AbstractWeb of ScienceGoogle ScholarVermeer, G. J. O., 2012, 3D seismic survey design, 2nd ed.: SEG.AbstractGoogle ScholarWe thank Gijs Vermeer for expanding on this topic, and we appreciate the additional insight provided.In the following, we restate important concepts from the paper and provide additional clarification on specific points.Our methodology recognizes that practical survey design will invariably involve compromises between geophysical and economic considerations. We believe that plots of fold, offset, and azimuth provide a useful visual indication of the effect of relaxing ideal design parameters. Vermeer correctly observes that such plots are based on discrete shot-receiver pairs. It is true that in raw form, these plots can be complex and misleading.One way to improve the validity of this type of presentation is to allow for the smoothing effects of limited bandwidth. In our paper, we have followed the spatial filtering approach of Cary and Lawton (2003). This yields distributions that are generally simpler and arguably more meaningful. Of course, it is important to also recognize the dependence of such plots on assumed earth parameters (e.g., P- and S-velocities), particularly in the case of PS modeling. We typically examine a series of plots covering a reasonable range of earth parameters.We also agree that there is an element of subjectivity in assessing such distributions. However, other factors being equal, we consider that an “even” distribution of fold, azimuth, and offset is more desirable than an “uneven” distribution. The final designs considered for our survey produced distributions (Figures 11, 12, and 13) that were compromises away from the ideal (e.g., Figure 8) but that were considered “acceptable” in terms of the variability in fold, offset, and azimuth.The specific 3D-PS survey considered here was funded by a research grant, with in-kind contractor support.The spacings used were accepted as being larger than ideal. Nevertheless, this is quite applicable to coal-industry seismic reflection in which we are often forced to use larger spacings than ideal. Our PS surveys are often done as an extension of a P survey, and parameters may be biased by the demands of the primary exercise.Unfortunately, receiver spacings are not always designed from first principles, being commonly influenced by client experience and budgets. However, a useful guide for bin sizes, and hence receiver intervals, is provided by the expected resolution limits.For the 3D survey described in the paper, we have used the equations provided by Chen and Schuster (1999) to deduce a nominal resolution of order 10–15 m at the target depth. We have used this as a guide for designing the receiver interval.We agree with Vermeer that when compromises need to be made, finer inline spacing is generally more important than crossline. This is especially true in the shallow coal environment and, as pointed out, tends to allow for better coherent-noise removal and improved spatial imaging. Our production P and PS surveys generally do use spacings that are finer in the inline direction and sparser in the crossline direction. For the particular survey discussed in the paper, one of the primary goals was to investigate the influence of azimuthal variation on the seismic data. The reduced crossline spacings used were aimed at improving azimuthal distributions in the raw data.Despite the design constraints, this survey provided a data set that enabled the overall project goals to be achieved.Again, we thank Vermeer for his insightful contribution to this topic. REFERENCES Cary, P. W., and D. C. Lawton, 2003, Bandlimited design and stacking of P-P and P-S surveys: 73rd Annual International Meeting, SEG, Expanded Abstracts, 842–845. AbstractGoogle Scholar Chen, J., and G. T. Schuster, 1999, Resolution limits of migrated images: Geophysics, 64, 1046–1053, doi: 10.1190/1.1444612.GPYSA70016-8033 AbstractWeb of ScienceGoogle ScholarFiguresReferencesRelatedDetails Volume 82Issue 3May 2017Pages: 1MJ-Z23ISSN (print):0016-8033 ISSN (online):1942-2156 publication data© 2017 Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryReceived: 28 Dec 2016Accepted: 02 Feb 2017Published Online: 21 Mar 2017Published in print: 01 May 2017 CITATION INFORMATION Gijs Vermeer, (2017), "Comment on: “Survey design for coal-scale 3D-PS seismic reflection” (S. Strong and S. Hearn, Geophysics, 81, no. 6, P57–P70)," GEOPHYSICS 82: X1-X3. https://doi.org/10.1190/geo2016-0709.1 Plain-Language Summary PDF Download Metrics Loading ...
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