Resistivity imaging of shallow salt with magnetotellurics as an aid to prestack depth migration

Currently NAM (Nederlandse Aardolie Maatschappij B.V.) is undertaking a large Pre-Stack Depth Migration (Pre-SDM) campaign over several salt-related prospects in the Netherlands, two of which, Broek and Ommelanderwijk, are located in fig. 1. To build proper Pre-SDM models of salt domes it is essential to have accurate knowledge of the geology in the shallow subsurface. Using data acquired in a conventional 3D seismic acquisition geometry, with typical 400-500 m line spacing, it is often difficult to image the top of shallow salt domes accurately in the 0-500 m depth range. This problem can be seen clearly in Fig. 2, where a seismic section through the Broek salt dome is displayed.