DUG Spike - Constrained Sparse Spike Inversion

The DUG Spike tool is used to simultaneously invert for P-Impedance, S-Impedance and density at every trace location, using any number of input seismic angle stacks. The inversion quantifies the rock properties that result in the observed AVO present in the seismic data. The inversion can be used to derive bandlimited (or relative) and absolute impedance. Laterally and time-varying wavelets are supported for each angle stack. Other rock property derivatives can also be calculated including Vp/Vs, Poisson's ratio, Lambda-Rho and Mu-Rho. Obtaining reliable density information is dependent on the input data (how many stacks, the quality of the data, and the angle ranges).

The seismic data is modelled as a convolution of an inverted reflection coefficient series with the derived wavelets. The Shuey 3-term approximation is used to constrain the inverted AVO coefficients and thus the resultant reflectivities and elastic parameters. The inversion optimises the solution based on two major constraints (seismic match and sparsity) which are calibrated using known well information. The optimisation engine uses a proprietary algorithm based on recent advances in the field of wavelet transform theory. Lateral continuity constraints (honouring the dip of seismic events), can also be utilised.

A state of the art, multi-offset, Bayesian wavelet derivation program is used to estimate the wavelet(s) and their uncertainty (seismic noise level). It features a fully-integrated Bayesian approach to the coupled uncertainties in wavelet estimation, a process which is critical in an inversion study. The wavelet extraction provides maximum likelihood estimates of the wavelet, as well as multiple realisations (stochastic) from the posterior, highlighting the uncertainly in the wavelet scaling and extent. A proprietary proven method for building the low frequency models is also available. Using advanced geostatistics, it incorporates all available information, producing a stable model away from the well while honouring the well information.

DUG Spike has been developed for successful service delivery over six years, and DownUnder GeoSolutions plans to make it available in 2010.