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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 68 (1984)

Issue: 4. (April)

First Page: 522

Last Page: 522

Title: Bright Spot Validation Using Comparative P-Previous HitWaveNext Hit and S-Previous HitWaveNext Hit Seismic Sections: ABSTRACT

Author(s): James D. Robertson, William C. Pritchett


Coincident P-Previous HitwaveNext Hit and S-Previous HitwaveNext Hit CDP lines were shot across the Willow Slough and Putah Sink fields, Yolo County, California, by the 1977-78 Conoco P-Previous HitWaveNext Hit/Shear-Previous HitWaveNext Hit Group Shoot. The fields produce gas from pay sands in the Cretaceous Starkey and Winters formations. Several of the thicker pay sands correlate with amplitude anomalies on the P-Previous HitwaveNext Hit sections, and these amplitude anomalies are true seismic "bright spots." The equivalent events on the S-Previous HitwaveNext Hit sections are much lower in relative amplitude when the overall gains of the P and S sections are balanced. The difference in the P and S responses is consistent with laboratory experiments which show that introducing gas into the pore space of a liquid-saturated rock dramatically lowers P velocity but minimally affects S veloc ty. The experimental lines demonstrate that comparison between the amplitudes of P and S is a diagnostic technique that can be sued to distinguish gas-liquid contacts from lithologic interfaces. An S-Previous HitwaveNext Hit section validates a P-Previous HitwaveNext Hit bright spot attributed to gas saturation when there is no anomalous amplitude at the equivalent S-Previous HitwaveTop event.

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Copyright 1997 American Association of Petroleum Geologists