Subsalt Imaging with Full-tensor Electromagnetics in the Red Sea

Three blocks in the Red Sea were acquired with coincident wide azimuth seismic (WAZ), full tensor gravity gradiometry (FTG), magnetotelluric (MT) and controlled-source electromagnetic (CSEM) data. The CSEM data acquisition was designed with long inline and broadside offsets to measure electromagnetic components that are sensitive to the horizontal resistivity, and that are required to image the expected subsalt sedimentary section. The 3D inversion of the MT and CSEM datasets recovered the general geologic framework. Both MT and CSEM show high sensitivity to the salt overburden structures, including the base of salt, and to the conductive subsalt sediments. MT inversion also recovered the basement structures that are characterized by tilted and faulted blocks, typical of a rift margin. A comparison of the 3D CSEM and MT inversion results with the depth migrated seismic and corresponding interval velocity model shows consistency with the seismic and FTG data in all blocks and addresses the problem of de-risking subsalt exploration with multiple geophysical measurements. The completeness and redundancy of the acquired dataset opens the road to the development of robust multi-geophysics integration workflows and introduces concepts new to the industry such as the use of tensor CSEM for subsalt structural imaging.