Journal Article

Bayesian inversion of marine CSEM data from the Scarborough gas field using a transdimensional 2-D parametrization

Anandaroop Ray, Kerry Key, Thomas Bodin, David Myer and Steven Constable

in Geophysical Journal International

Volume 199, issue 3, pages 1847-1860
ISSN: 0956-540X
Published online October 2014 | e-ISSN: 1365-246X | DOI: https://dx.doi.org/10.1093/gji/ggu370

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We apply a reversible-jump Markov chain Monte Carlo method to sample the Bayesian posterior model probability density function of 2-D seafloor resistivity as constrained by marine controlled source electromagnetic data. This density function of earth models conveys information on which parts of the model space are illuminated by the data. Whereas conventional gradient-based inversion approaches require subjective regularization choices to stabilize this highly non-linear and non-unique inverse problem and provide only a single solution with no model uncertainty information, the method we use entirely avoids model regularization. The result of our approach is an ensemble of models that can be visualized and queried to provide meaningful information about the sensitivity of the data to the subsurface, and the level of resolution of model parameters. We represent models in 2-D using a Voronoi cell parametrization. To make the 2-D problem practical, we use a source–receiver common midpoint approximation with 1-D forward modelling. Our algorithm is transdimensional and self-parametrizing where the number of resistivity cells within a 2-D depth section is variable, as are their positions and geometries. Two synthetic studies demonstrate the algorithm's use in the appraisal of a thin, segmented, resistive reservoir which makes for a challenging exploration target. As a demonstration example, we apply our method to survey data collected over the Scarborough gas field on the Northwest Australian shelf.

Keywords: Inverse theory; Probability distributions; Non-linear electromagnetics; Marine electromagnetics; Australia

Journal Article.  12148 words.  Illustrated.

Subjects: Geophysics ; Oceanography and Hydrology