Abstract

The theory and practical utilization of simplification of the original general expressions for the reflection of compression and shear waves at a boundary as a function of the densities and velocities of layers in contact are presented in this paper. The original general expressions are highly non-linear and presumed to defy physical insight. Elimination of the properties of V_s and ΔV_s in favour of  and Δ enabled the success of a two-term approximation and revealed the surprising effects of Poisson’s ratio on P-wave reflection coefficient which was a neglected elastic constant. The simplified equation was further expressed in terms of angular reflections to obtain first order reflectivity expression in terms of R_p and R_s. The number of unknown parameters is thus reduced by assuming that the fractional changes in material parameters are small across layer interfaces. Simplification of the equation has brought into existence the Amplitude Variation Offset (AVO) attributes with successful practical utilization in hydrocarbon delineation in many oil fields including the Niger Delta Slope. Determination of the terms of the linearized equation from rock properties and seismic events remains of vital value in practice as demonstrated in the evaluation of hydrocarbon potential in North-Built field.

Key words: Compressional and shear waves, densities, velocities, Poisson’s ratio, amplitude variation offset (AVO) attributes, hydrocarbon.