VERTICAL SEISMIC PROFILE IN A DESVIATED WELL TO IMAGE RESERVOIR WITH LOW DIP STRUCTURES USING CONVERTED WAVES

Abstract

After cementing and casing a deviated well, the acquisition of a Vertical Seismic Profile (VSP) was considered to map a reservoir, imaging the zone below and around the hole using shear waves (PS). Environmental restrictions on the area limited the possible survey geometries.

The main objective of this paper is to define and apply the methodology to select the appropriate VSP survey in a deviated well and also establish the parameters and VSP data processing sequence to provide an image on which to map and delimit laterally the top and base of the hydrocarbon reservoir.

Using sonic and density logs, a synthetic seismogram was built and tied to a migrated seismic section along the well path. With ray tracing modeling, different geometrical surveys were simulated in a 2D geologic model built through sonic and density logs, providing several imaging scopes from which the optimal configuration was chosen. By simulating the optimal VSP survey in the 2D geologic model, a synthetic VSP dataset was supplied and processed. A VSP survey with the optimal configuration was run, providing a dataset that, after processed with the same sequence applied to synthetic VSP data, confirmed the subsoil model and imaged the target zone.