PGS’ Towed Streamer EM technology measures changes in resistivity in the sub-surface. The system is designed to operate optimally in water depths up to ~500m, and recover resistivity up to ~3,000m below mudline.

3D EM as a stand-alone service could be acquired over existing or planned 3D seismic. 2D GeoStreamer seismic and EM data could be also acquired simultaneously using a single vessel. Acquisition speed is between 4-5 knots resulting in a step-change is marine CSEM acquisition efficiency compared to traditional sea floor node methods.

Current is injected into a dipole source that generates an EM field. The field penetrates the sub-surface and is distorted by the presence of resistive bodies. Measurements (voltage) are made by the receivers at various offsets from the source.

Amplitude and phase responses of the Earth which are recovered can be transformed into sub-surface resistivity models through a process of inversion. Hydrocarbons are typically characterized by high resistivity

Acknowledgments.
We thank PGS for providing towed streamer EM examples. Special thanks to Joshua W. May for giving us the opportunity to include the example in our e-book.