Basics

What is offshore electromagnetic (EM) investigation? Find here below is a short summary of the differences between the seismic and the EM exploration methods. 

The traditional exploration method, seismic, relies on the transmission of acoustic waves through the various geological layers at the speed of sound according to the density of those layers.

The EM method makes use of the diffusion of electromagnetic fields.

Seismic works with rock density, EM works with rock resistivity.

While seismic defines the structures of the geological formations, EM measures their resistive content and may therefore indicate the presence of oil and gas.