| The amplitudes of reflected seismic waves contain substantial petrophysical information on changes in the properties of materials in the earth. To extract this information correct amplitude processing is required, especially in the analysis of the variation of reflection strength with angle of incidence as measured in well bore seismic experiments. However, current VSP amplitude gain techniques involve $Tsp{n}$ scaling down the trace. This practice originates in the need to improve the visibility of weaker events diminished by geometrical spreading of a wavefront. This method is crude and does not properly take into account for geometry and geology in amplitude decay. As an alternative we propose a model based amplitude correction. Amplitude correction curves are derived on the basis of ray tracing through a reasonable geologic model; the resulting correction curves can then be applied to the VSP data to restore the amplitudes. Tests on synthetic VSP arrival curves demonstrate the superiority over the empirical based correction. Six different amplitude attributes are calculated for the down-going primary wavelet of a shallow zero offset VSP and the application of the method to this data set is attempted. |
