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Postsurvey calibration of 3D seismic results to presurvey modeling predictions

PGS Technology, Perth, Australia

Corresponding author: andrew.long@pgs.com

The first 20% of the full text of this article appears below.

Presurvey planning of marine 3D seismic surveys has evolved to be a rigorous pursuit of 1D, 2D, and 3D elastic modeling exercises complemented where appropriate with the reprocessing of available 2D and 3D field data. It is often the case that the resulting recommendations for acquisition parameterization have expensive implications, and a significant emphasis must be placed upon the credibility of the modeling results.

I demonstrate with several multistreamer case studies that presurvey planning studies can be applied with great accuracy. Emphasis is on the quantification of the crossline acquisition footprint, the quantification of long-offset requirements for both AVO and imaging requirements, the interrogation of 3D illumination study diagnostics, and the quantification of the target frequency bandwidth and resolution. Despite the inherent approximations of the earth model and the modeling scheme itself, elastic 3D modeling of the crossline acquisition footprint compares favorably with measured amplitude variations; at worst, it is within one standard deviation, and consistently erring on overestimation. Therefore, such modeling serves as a valuable presurvey constraint on maximum acceptable streamer spread width for a given survey location. Offset requirements can be robustly predicted using relatively simplistic interval P-wave velocity models. However, I also demonstrate how more complex 3D velocity models can be used to accurately predict a host of 3D illumination scenarios, useful for the planning of shooting templates, the planning of infill management, and the optimization of 4D time-lapse acquisition strategies. Again, postsurvey results compare favorably to presurvey modeling predictions. Finally, it is easily demonstrated that the recoverable frequency bandwidth can be accurately predicted throughout each stage of multichannel processing.

Overall, the collective case study results presented here demonstrate the value and accuracy of careful presurvey planning for addressing all possible acquisition parameter decisions.

The following sections provide examples on the quantification of acquisition footprint, offset requirements, . . . [Full Text of this Article]