Challenges presented by late uplift, erosion and other factors have made evident the need for new types of data and better exploration ideas.
Historically, CSEM was used to test individual prospects but in 2008, EMGS pioneered the use of 3D EM on a regional scale and gave explorationists a new tool against uncertainty in the Barents Sea.
Case study- the Hoop area
The last three licensing rounds in the Barents Sea, much emphasis has been placed on the northern part of the structural element called the Bjarmeland Platform. Moreover, a total of 15 blocks have been awarded in an area commonly referred to as “Hoop” (from the Hoop Fault Complex.
One of the main targets in the Hoop area has been the lower Jurassic Realgrunnen Subgroup, which is quite shallow. The main risk for this target was seal integrity, as faults were seen extending up to the Quaternary section, with an associated high risk of leakage.
In this case example, the integration of CSEM and seismic resulted in the upgrading of a new prospect.
In September 2013 an oil discovery was made in license PL537 on the
Wisting prospect in Lower- to Middle Jurassic reservoir rocks. The discovery, located at a very shallow depth (∼300 mbml), was associated with a significant EM anomaly as well as a seismic AVO response.
The CSEM anomaly seemed to conform to structure and matched well both in depth and lateral extent with the seismic amplitude anomaly, an example of why CSEM data should be considered when planning for other wells targeting similar prospects in the area.
The Wisting oil discovery as imaged by 3D CSEM inversion (vertical
resistivity), displayed on a 2D seismic line (seismic courtesy of TGS). The black line indicates the well location.
The most important result of the Wisting discovery from a commercial and CSEM perspective is probably the fact that it was (light) oil, thereby demonstrating that in areas with highly resistive background, hydrocarbons, and in particular oil, can be seen using CSEM.
EMGS has acquired nearly 50,000 km2 of 3D EM data in the Barents Sea. The data library covers all significant discoveries in the region and demonstrates excellent agreement with well results.
- Improved regional geological understanding, and supported workflow development for seismic depth migration
- Oil is imaged with CSEM , also in areas with highly resistive backgrounds
- Havis has resistive anomalies corresponding with the discovery and 3D EM correctly showed 7219/9-1 as dry
- Several E&P companies were successful using multi-client 3D EM to gain a competitive advantage in the 20th, 21st and 22nd rounds and in the APA licensing rounds