VSP survey assists in the reservoir characterization of deep-water turbiditic reservoir offshore Brazil

Abstract

In this case study we review the main results from a rigsource VSP survey, acquired in a deep-water deviated well drilled offshore Brazil. The primary goal for the VSP was to illuminate the lateral variation of thin sand and shale bodies, with higher resolution than available with surface seismic data. This was achieved initially by 2D migration of the VSP data and later, through acoustic impedance inversion of the VSP data.New surface seismic data is being acquired in the area and the VSP results will be used to quantitatively assess the data processing and the well tie quality. Seismic parameters such as phase, true amplitude and anelastic attenuation are readily available from the VSP measurements. The anelastic attenuation is quite important in this area as the overburden is dominated by highly cyclic siliciclastic deposition, which results in strong attenuation of the seismic data.Finally, we present some advanced VSP data processing techniques, such as migration of surface related multiples and far field signature estimation for Q-factor computations, which added value to the VSP results.