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9th International Congress of the Brazilian Geophysical Society
- Conference date: 11 Sep 2005 - 14 Sep 2005
- Location: Salvador, Bahia, Brazil
- Published: 11 September 2005
461 - 462 of 462 results
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Offset VSP in a deviated well to get converted shear waves
This paper presents a case history in which the main objective of the borehole seismic survey was to obtain information about converted shear waves, in order to support the evaluation of feasibility for an OBC project in a Tertiary reservoir, Offshore Brazil. The Offset VSP has shown a large degree of P to S conversion, at different layers. The well trajectory in combination with the source position allowed to get Shear velocities, and also to generate P and S images that provided an additional tool to evaluate the degree of P to S conversion.
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Seismic phase and amplitude calibration deep-water Brazil using VSP data
Authors Rafael Guerra, Carlos Rodriguez and Scott LeaneyIn this paper we review a case study where borehole seismic data acquired in a deep-water field offshore Brazil, was used to build a 1.5D-anelastic model that accurately predicts the seismic amplitude attenuation versus time and offset, due to the combined effects of geometrical spreading, transmission losses and anelastic attenuation (Q-factor). This borehole calibrated model is ray-traced to compute a seismic amplitude gain function that can be applied directly to surface seismic pre-stack gathers and the results compared to the geometrical spreading correction conventionally used. The Q(z) profile derived from the VSP data provides also very useful information for high-frequency enhancement of seismic data. Finally, we show the use of VSP data in assessing
the phase of different vintages of surface seismic data and their degree of well tie.
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