Seismic phase and amplitude calibration deep-water Brazil using VSP data

In 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<br>the phase of different vintages of surface seismic data and their degree of well tie.