Parameterisation for Reservoir Oriented AVO Inversion

In this paper we discuss the subsurface parameters that can be extracted from seismic by AV O inversion over a target interval. It is argued that, while people are very much used to invert for impedances (P and S), or combinations of impedances (e.g. Extended Elastic Impedance), the conventional AVO equations can be formulated directly in terms of bulk modulus and shear modulus, which are much more closely related to hydro-carbon saturation and porosity than impedances or velocities.

It is also demonstrated that linear AVO techniques, like the ones based on primary reflection coefficients, have their limitations, due to the fact that there is much more internal multiple scattering and mode conversion than one would usually expect. These problems can be solved by adopting a wave equation based inversion approach, where the non-linear character of the relationship between the data and the property representation to invert for, is fully honoured.

Examples are given that demonstrate the increased sensitivity of the bulk modulus to hydro-carbon saturation, over acoustic impedance.