Practical application of Wave Equation Based AVO Inversion

This talk demonstrates a wave-equation based method to extract unique reservoir properties from seismic data. Genuine seismic data will always have some degree of non-primary energy such as interbed multiples. Using Wave Equation Based AVO Inversion (WEB-AVO) we consider primary reflections, together with interbed multiples, mode conversions and transmission effects. Notably different to conventional AVO inversion methods that assume primary reflections, an elusive seismic reality. A significant differentiator for WEB-AVO is the ability to work with a wider range of seismic gathers. possibly coming out of processing immediately after migration, without special conditioning. The WEB-AVO results differ from conventional methods being layer properties of compressibility and shear compliance, rather than interface properties such as P and S impedance. Compressibility; the inverse of bulk modulus and shear compliance; the inverse of shear modulus, provide a natural separation between fluid and lithological effects, that is required for robust reservoir properties prediction. This separation is key when deriving porosity, saturation, and lithology products. The scope will include the fundamentals of the WEB-AVO method, important steps in a WEB-AVO project and a number of examples. The examples are drawn from onshore and offshore Australia considering common challenges such as coal and marl in a classic sand-shale sequence. In each situation the primary wavefield at the target reservoir is being contaminated by scattered energy arriving from the overburden. This normally first presents as an unsatisfactory well-to-seismic tie and is traditionally tackled through seismic data conditioning or well log editing. However, in our examples we build alternative elastic synthetics that consider the overburden and unravel how the wavefield at the reservoir is actually formed.