Foothills structural model de-risking with 3D magnetotellurics

Geophysical imaging in the foothills environment is typically hampered by complex structure, and the high cost of data acquisition in poorly accessible, rugged topography. Seismic imaging is particularly difficult due to poor signal penetration, steeply dipping structures and irregular data coverage. The use of magnetotellurics (MT) has become a successful complementary tool, due to good sensitivity to the deep resistive targets typically encountered below folded sequences of more conductive units. Due to non-uniqueness and resolution limitations, MT 3D inversion requires additional constraints in order to recover a reliable image. These usually come from geological interpretation of available seismic and well data, however it is often the case that several competing structural models can be derived. In this abstract we propose a workflow that employs magnetotelluric inversion to assess the validity of such structural models, by examining whether they are compatible with the electromagnetic observations. We further apply 3D non-linear uncertainty estimation to address the reliability of the inversion results, obtaining a bounding envelope of the resistive anomaly.