as Controlled Source Electromagnetics, or CSEM, that involves towing an electric transmitter underwater to generate stronger electromagnetic signals in subsea rock.
In either case, the sensors sitting on the ocean bottom are used to detect these faint electric currents and identify the formations with the highest resistance—offering a new source of data that can help scientists infer which formations are the most likely to contain oil and gas deposits.
“This is a complement to seismic surveys that use acoustics to image the density of subsea rock,” Eiskamp says. The electromagnetic data can help confirm the likelihood of oil and gas deposits by helping to eliminate other possible explanations for a low-density geological formation, such as volcanic activity. “With that and good modeling of the geology that you get with seismic data, you should have a pretty good picure,” Eiskamp says.
Quasar Geophysical is a relatively new division of Quasar Federal Systems, a privately held R&D contractor that bills itself as a world leader in extremely low-frequency electromagnetic sensing systems (frequencies between 0.01 Hz to 5 MHz). Quasar was developing its underwater sensing technology to detect submarines and underwater mines when the team realized the potential commercial applications for the technology.
There are still challenges to using electromagnetic sensing in oil and gas exploration, of course. Much of the undiscovered deposits in the Gulf of Mexico, for example, are hidden under vast salt domes, which render seismic surveys more-or-less useless by reflecting nearly all of the sound waves. Whether electromagnetic sensing alone can pinpoint oil and gas deposits beneath salt domes is another question. But Eiskamp remains hopeful, saying, “We’re at some level of discussion with just about every offshore exploration company.”
