3D land CSEM inversion in noisy environment with a single transmiter: inversion approach and application for geothermal water prospection

François Bretaudeau (1) , Sebastien Penz (1) , Nicolas Coppo (1) , Pierre Wawrzyniak (1) , Mathieu Darnet (1)

1 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)

Anthropogenic noise, cost and logistical constrains generaly limit to the use of land CSEM to a few transmiter positions for the deep imaging of the electrical conductivity. The 3D inversion of CSEM data in the near field using a single transmiter position suffers from critical sensitivity singularities. We proposed a robust inversion framework adapted to this ill-conditioned inversion problem. The framework relies specificaly on a robust Gauss-Newton solver, model parameter transformations to compensate the heterogeneous sensitivies, and on the reformulation of the near field CSEM data under the form of a pseudo-MT tensor. We describe the approach used for modeling and inversion implemented in our code POLYEM3D and show the advantages of pseudo-MT tensor formulation. The strategy have been tested on a pathologic synthetic case inspired from grayver et al (2013), and then was successfully applied to a real CSEM dataset acquired in the context of thermal water prospection in a noisy environnement.

Mots clés: 3D inversion; land CSEM; noisy environment; single transmiter; sensitivity singularities; thermal water prospection

Domaines: Géophysique [physics.geo-ph]; Optimisation et contrôle [math.OC]

François Bretaudeau, Sebastien Penz, Nicolas Coppo, Pierre Wawrzyniak, Mathieu Darnet. 3D land CSEM inversion in noisy environment with a single transmiter: inversion approach and application for geothermal water prospection. International Symposium in Three-Dimensional Electromagnetics (3DEM), Gerald W Hohmann Memorial Trust, Mar 2017, Berkeley, United States. ⟨hal-01458151⟩