3D TTI Gauss-Newton inversion, data step-change in imaging of CSEM data

In areas with high electric anisotropy and/or steep bedding dip angles, TTI effects in the sub-surface can lead to imaging artefacts in VTI inversion results. A 3D Gauss-Newton inversion for TTI media has been developed capable of inverting large CSEM datasets. Unlike previously published gradient-based inversion schemes with TTI medium description, the inversion can update the bedding azimuth and dip angle from a start model containing no information on the structure. This enables the use of the inversion in areas with little or no reliable structural information. The presented field data examples illustrate the importance of the TTI inversion process to avoid possible misinterpretation of the CSEM data. Benefits of the TTI 3D Gauss-Newton demonstrated by the case examples are that imaging artefacts are removed, dip and azimuth angles can be inverted for, structurally meaningful models are reconstructed and that the inversion can typically be started from a simple start model. A showcased example from the North Sea in Norway clearly demonstrates the importance in this area to use a TTI approach in imaging.