Resistivity logging is fundamental in formation evaluation because hydrocarbons do not conduct electricity while all formation waters do. Therefore, a large difference exists between the resistivity of rocks filled with hydrocarbons and those filled with formation water. For almost 80 years, wellbore resistivity logs have provided evidence of the presence of hydrocarbons in the subsurface.

The kick on the resistivity log is always exciting news. But, there is one big problem with a resistivity log: you need to drill a well before you get this vital piece of information. Wouldn't it be very useful to get resistivity information before drilling a well?

In the late 1990's, two Statoil researchers, Svein Ellingsrud and Terje Eidesmo, were pondering this problem. They studied the physics of what happens when you probe the subsurface with the electric field from a strong low-frequency electric dipole source. Svein and Terje found, as was excellently described in Lars Løseth's talk today on EM for dummies, that the electric field will "survive" over long distances where it can travel laterally in high-resistive hydrocarbon layers. Simply said, by measuring the electromagnetic response at long source-receiver distances, they could infer whether hydrocarbons were present or absent.

Even though other people had been working on the same problem on how to map hydrocarbons with electromagnetic fields, no one had figured out this innovative solution to the problem. They were the first persons to realize this fact, and prove the principles.

In 2000, Svein and Terje acquired data over a producing field offshore Angola and proved the concept of seabed logging. Two years later, the revolutionary seabed logging technology was made vailable to the industry through the formation of EMGS. The company was lead by Eidesmo and Ellingsrud, who were joined by Ståle Johansen.

As senior vice president for EMGS research and technology department, Svein was responsible for developing the next generation seabed logging technologies: improved source technology, improved sensor technology, and improved data processing and interpretation technology. Over the past few years, we have witnessed that seabed logging has moved from single 2D lines to grids and 3D surveys. The data must be processed and interpreted by tools such as 3D inversion, integrated with other geophysical data.

What started out as a science project led by Svein and Terje 10 years ago for using low-frequency electromagnetics to identify hydrocarbons has - as we have seen here today - developed into a global industry that has changed oil exploration. Seabed logging, in proper use, is the first truly independent predrilling measurement of reservoir properties since the development of seismic technology.

For being instrumental in the technology development of seabed logging, or CSEM, for hydrocarbon mapping, NGF is honoring Terje Eidesmo and Svein Ellingsrud.