Acoustic Non-Linear Full-Waveform Inversion Application on an Outcrop-Based High-Resolution Geological and Petrophysical Model (Book Cliffs, Utah)

Geological outcrops are often used to develop predictive models and provide quantitative parameters that describe the architecture and facies distribution at a sub-seismic scale, which is used in the development of exploration and production strategies. In the oil- and gas-industry, the inversion of seismic data is well-known technique used for obtaining the reservoir geometries and properties. It often uses well data and external knowledge such as outcrop analogues as guiding constraints. The goal of this study is to build a synthetic seismic data-set that provides detailed, realistic geological and petrophysical reservoir information and use these data for a multi-parameter (P-wave velocity (compressibility) and bulk density) acoustic full-waveform inversion.

As a basis for the geological and petrophysical modeling we used published work of a regional section of the Book Cliffs outcrops (Utah, USA) with a continuous exposure of mostly shallow-marine deposits over 120 km. A subset of this data set is used and populated with representative layer properties. The so-called ‘Kennett invariant embedding method’ was used for the forward modeling of a synthetic acoustic full wavefield. We apply the recently introduced target-oriented non-linear full-waveform acoustic inversion technique (Gisolf and Van den Berg, 2010) on the resulting synthetic pre-stack seismic data set. This approach keeps the acoustic inversions to a manageable size and therefore looks promising for commercial implementation.

The main result is that the two media parameters (P-velocity and bulk density) could be successfully recovered from the seismic synthetic data set that provides detailed reservoir information at a resolution higher than the shortest seismic wavelength. In addition, a wide band reconstruction of the compressibility was achieved, well outside the spatial bandwidth commensurate with the seismic temporal bandwidth. These were possible because the inversion exploits the non-linear nature of the relationship between recorded data and the medium contrast properties. Non-linear inversion is taking full advantage of this by which meaningful density information can be extracted. The quality of fit between the broadband predictions and the actual model is outstanding for the compressibility, and good for the bulk density. Moreover, the inversion results make it possible to understand and interpret which geological features can be resolved from seismic data.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California