A one-step Bayesian inversion framework for 3D reservoir characterization based on a Gaussian mixture model-A Norwegian Sea demonstration

• Published in: GEOPHYSICS
• Main Authors: Fjeldstad, Torstein, Avseth, Per Åge, Omre, Henning
• Format: Article in Journal/Newspaper
• Language: English
• Published: Society of Exploration Geophysicists (SEG) 2021
• Subjects: Norwegian Sea
• Online Access: https://hdl.handle.net/11250/3032132; https://doi.org/10.1190/geo2020-0094.1

We have developed a one-step approach for Bayesian prediction and uncertainty quantification of lithology/fluid classes, petrophysical properties, and elastic attributes conditional on prestack 3D seismic amplitude-variation-with-offset data. A 3D Markov random field prior model is assumed for the lithology/fluid classes to ensure spatially coupled lithology/fluid class predictions in the lateral and vertical directions. Conditional on the lithology/fluid classes, we consider Gauss-linear petrophysical and rock-physics models including depth trends. Then, the marginal prior models for the petrophysical properties and elastic attributes are multivariate Gaussian mixture models. The likelihood model is assumed to be Gauss-linear to allow for analytic computation. A recursive algorithm that translates the Gibbs formulation of the Markov random field into a set of vertical Markov chains is proposed. This algorithm provides a proposal density in a Markov chain Monte Carlo algorithm such that efficient simulation from the posterior model of interest in three dimensions is feasible. The model is demonstrated on real data from a Norwegian Sea gas reservoir. We evaluate the model at the location of a blind well, and we compare results from the proposed model with results from a set of 1D models in which each vertical trace is inverted independently. At the blind well location, we obtain at most a 60% reduction in the root-mean-square error for the proposed 3D model compared to the model without lateral spatial coupling. acceptedVersion