What is EM?
EM (electromagnetic) technology is a wide term and refers to a number of different things. When Rocksource uses the term, we refer to a specific methodology called CSEM (controlled source electromagnetic sounding) which is a remote surveying technique that enables measurements of resistivity contrasts in the subsurface.
In relation to oil and gas exploration, hydrocarbons are resistive while surrounding rocks are typically, but not always, conductive. This creates a resistivity contrast that can be mapped using CSEM techniques. EM data are complimentary to seismic data. Whereas seismic data can identify structures that may contain hydrocarbons, EM data tells us something about the fluids within the structures.
In marine settings, EM receivers containing electric antennas and magnetic coils are placed on the seabed. A source is towed above the receivers, emitting electromagnetic energy with low frequency. Energy from the source propagates (diffuses) into the subsurface. If there are no resistivity contrasts present, the energy will gradually be attenuated and disappear. If resistivity contrasts are present (such as that caused by an oil-filled sandstone), EM energy will propagate back to the sea floor where it is recorded by receivers. The recorded information can be processed to create detailed charts of subsurface resistivity distribution.
Contact Information
Address:
Thormøhlensgate 53 D
Postboks 994 Sentrum
N-5808 Bergen
Norway
| Phone: | +47 05369 |
| From abroad: | +47 21 49 32 69 |
| Fax: | +47 55 36 87 98 |
Per Anders Muri
VP Corporate Communications
Phone: +47 91 11 61 21
per.anders.muri@rocksource.com