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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 68 (1984)

Issue: 4. (April)

First Page: 465

Last Page: 466

Title: Shear and Compressional-Previous HitWaveNext Hit Surface and Downhole Tests in Southern Louisiana: ABSTRACT

Author(s): Robert J. Corbin, David W. Bell, Stephen H. Danbom


Shear- and compressional-Previous HitwaveNext Hit seismic tests using the Vibroseis system were performed near a well in south-central Louisiana to study acquisition, processing, and interpretation problems typically encountered in low-velocity, relatively uncompacted Gulf Coast sediments. The primary objectives envisioned for these tests were to improve S-Previous HitwaveNext Hit data quality by studying surface noise patterns to optimize source and receiver arrays, provide a direct correlation of P- and S-Previous HitwaveNext Hit seismic data by using vertical seismic profiles (VSP), and measure the decay of P- and S-Previous HitwaveNext Hit seismic energy with depth by using a downhole geophone.

To achieve these objectives, an expanding reflection profile (ERP), a walkaway noise analysis, and a VSP were recorded with both S- and P-Previous HitwaveNext Hit sources. The S-Previous HitwaveNext Hit ERP shows reasonable data quality although it was very band-limited (5-12 Hz). In contrast, the P-Previous HitwaveNext Hit data quality is excellent. The difference in data quality is primarily due to strong, source-generated

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noise from the S-Previous HitwaveNext Hit vibrators. Time-depth data available from the S- and P-Previous HitwaveNext Hit VSPs were used to convert the time sections to depth, and hence provide the best visual tie of common reflecting horizons. The accuracy of the ties is mainly limited by the poor signal-to-noise ratio and narrow bandwidth of the S-Previous HitwaveNext Hit data.

Finally, energy decay measurements from first breaks on VSP data show that S waves have a higher loss than P waves in the near surface. However, below 3,000 ft (915 m), the slopes of the energy decay curves are similar, thus implying S-Previous HitwaveNext Hit data quality will not deteriorate faster than P-Previous HitwaveTop data quality at greater depths.

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Copyright 1997 American Association of Petroleum Geologists