Demonstrating the Full Potential of Controlled-Source Electromagnetic (CSEM) Technology for Hydrocarbon Exploration: A Case Study of a Deep Gas Discovery from the Upper Cretaceous of the Norwegian Sea

Jonny Hesthammer, Alexander Verechtchaguine, Roy Davies, Peter Gelting, Mikhail Boulaenko, and Torolf Wedberg
Rocksource ASA, Bergen, Norway

Whilst 2D and 3D seismic methods are now widely accepted and considered as proven technology for hydrocarbon exploration and reservoir characterization, the use of controlled-source electromagnetic (CSEM or EM) surveying is still in its infancy and is often met with scepticism by geologists, geophysicists and managers. This is at least partly due to the existence of a number of negative case studies that are frequently cited as evidence for the technology being unreliable.

The Luva gas discovery in the Norwegian Sea is one such example. It has gained a reputation as being a significant gas discovery that shows only a very small and enegmatic EM response, in spite of a proven hydrocarbon column in excess of 150 metres thick. This “false-negative” response could easily have lead to the discovery being missed by a company that was using CSEM to guide “drill-or-drop” decisions.

Recent advances in acquisition technology, processing algorithms and the development of advanced workflows for integrated processing of EM and seismic data have greatly improved the power of CSEM technology. In this case study we present the workflow and results from a recent reprocessing of the Luva dataset, which has not only explained the reasons for the apparent false-negative response, but also revealed a clearly visible EM anomaly that can be correlated with seismic DHIs.

This study illustrates that many CSEM data sets that have previously been dismissed as being “unresolvable”, may yet yield valuable information, and demonstrates that the oil-industry still has a long way to go before mastering CSEM technology.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas