In recent years the importance of combining diverse geophysical datasets in multiphysics workflows has become clear. Controlled Source ElectroMagnetic (CSEM) methods, which measure the electrical resistivity of the seafloor, are used to complement other geophysical approaches across a range of applications.

The towed streamer EM system uses a high powered horizontal electric dipole source towed behind a survey vessel to transmit EM fields through the seawater column and into the seafloor. The resulting signals are recorded by an array of electric fields receivers, also towed behind the survey vessel. This configuration provides a fast and efficient way of acquiring high resolution CSEM data at significantly lower cost and with lower environmental impact than other EM methods, paving the way for large area surveys in parallel with seismic programs.

Multiphysics workflows which combine electromagnetic data with other sources of information such as seismic, well logs or gravity/magnetics, can then lead to improved imaging and more robust characterisation of rock and fluid properties of the sub-surface. In the upstream oil and gas industry, approaches that integrate seismic and electromagnetic data have been used successfully to improve imaging in areas of complex geology (for example around basalt or salt), leading to greater understanding of structure and stratigraphy. Similarly, rock physics driven workflows combining pre-stack seismic and controlled source electromagnetic data have been used to distinguish commercial from sub-commercial hydrocarbon accumulations, something that is notoriously challenging using seismic alone, leading to better exploration decision making.