A few case histories of subsurface imaging with EMAP as an aid to seismic processing and interpretation¹

The electromagnetic array profiling (EMAP) exploration method can be combined with a direct one‐dimensional inversion process for conversion to depth to produce a subsurface resistivity cross‐section. This cross‐section may then be interpreted in parallel with a seismic cross‐section to enhance the prediction of rock type and structure. In complex thrust environments and areas of shallow carbonate rocks, the EMAP method is often used to provide additional data either to help the seismic processor and/or to aid the seismic interpretation. In particular, the electromagnetic (EM) data can be used to build an independent seismic velocity file for depth migration.

Three EMAP test areas in the western United States are used to demonstrate such a use of EMAP as an expioration tool. The first shows how a velocity file is estimated from resistivity data for seismic depth migration processing in a complex thrust environment. In the second example, the method is applied in layer‐cake geology with high seismic velocity rocks at the earth's surface. The third example is another complex thrust environment, but in this case the velocity file derived from the resistivity data is used for stacking the seismic data.