Borehole Geophysics: New Directions

One of the major chalenges in borehole geophysics is reservoir analysis. What information about reservoirs one can get measuring seismic arrivals in boreholes? When we talk about reservoirs, we are trying to obtain knowledge about porosity, saturation, viscosity, anisotropy and permeability. These parameters mainly dictate the reservoir characteristics which are important for oil production. In this presentation, we will discuss a possibility for direct mapping of the Vp/Vs ratio which is an important indicator for the petroleum reservoir. In reservoirs with relatively high porosity in sands, this ratio can be substantially higher than in the surrounding host rocks. The proposed technique is a two step procedure. First, we separate compressional and shear arrivals and then compute compressional and shear wave velocities separately using tomographic inversion of first arrivals.