Towed Streamer EM Acquisition
The electromagnetic streamer system deploys a receiver cable at down to 100 m depth and a powerful horizontal dipole source at 10 m depth. A specially coded broadband source creates an electromagnetic field which penetrates the earth. The highly sensitive receiver electrodes housed in the streamer detect fluctuations in the field from which subsurface resistive anomalies can be derived. Vessel speed is comparable to 2D seismic, so the acquisition efficiency is very high, especially for regional surveys.
Simultaneous Acquisition of EM and GeoStreamer®
For the ultimate in exploration efficiency and risk mitigation, the PGS Towed Streamer EM system can be towed simultaneously with GeoStreamer. This makes it possible to acquire both broadband 2D seismic data and high-density 3D EM data from a single vessel, at an acquisition speed of 4 - 5 knots.
Both datasets are QC'd and processed onboard to produce inversion-ready field data, which can be inverted and then integrated for interpretation on a regional or prospect scale (or both). PGS has demonstrated the efficiencies gained using simultaneous acquisition projects in the Celtic Sea to the South of Ireland, and separately in the Barents Sea during 2013 and 2015.
Simultaneous EM and GeoStreamer acquisition
EM only acquisition
PGS' Towed Streamer Electromagnetic system can also be utilized for EM only surveys, this strategy is generally employed in mature areas where seismic data already exists. In 2014 PGS used a third-party vessel to acquire high-density EM data in the Barents Sea, highlighting the ease of deployment flexibility of the EM system and the platform flexibility.
Notice how similar the system looks to a towed streamer seismic layout. The degree to which a seismic vessel needs to be adapted to operate the EM system is minimal, therefore specialized vessels are not required.
EM only acquisition