Accelerated Frontier Exploration using 3D EM

Pål Gabrielsen

Exploration in frontier areas, and especially in the arctic, is a delicate matter as minimal impact on the environment is crucial. Exploration strategies therefore need to consider not only geological and commercial aspects, but also important environmental constraints. We would like to challenge the traditional exploration methodology and propose that controlled source electromagnetics (CSEM) and marine magnetotellurics (MMT) should be an important tool in the screening and evaluation of frontier areas. A joint 3D CSEM and MMT acquisition at an early stage in the exploration phase can significantly improve the structural understanding by combining these data with sparse 2D seismic. Furthermore, the identification of prospective areas based on electromagnetic (EM) data can guide future 3D seismic- and drilling activity faster to areas with the highest chance of commercial success. Overall this will minimize the total activity and lead to fewer dry holes in these vulnerable regions. We will demonstrate how EM can be used in early exploration by real data case examples mainly from the Barents Sea. We will show several case examples where both 3D CSEM and MMT data exhibit structural information. These data combined and calibrated with a sparse 2D seismic grid can fill in the structural gaps between the individual 2D seismic lines. The electromagnetic data is also capable of imaging below basalt and salt layers where seismic typically struggles. EM can therefore be of particular importance in regions where a high resistive basement, basalt layer or salt is present which is typical for large parts of the vast regions of the Barents Sea, Greenland and Jan Mayen. Despite a very good statistical record for CSEM in predicting the outcome of exploration drilling, the technology is not widely applied as an important exploration tool. In this presentation we will demonstrate several case examples from the Barents Sea where using CSEM data can help to assess the prospectivity. 30 years of exploration in the Norwegian Barents Sea has so far resulted in only one field in production and a handful of significant discoveries, despite nearly 100 drilled wells. However, a large proportion of the wells have encountered shows or minor volumes of hydrocarbon. This proves that there is indeed a working hydrocarbon system, but also that the challenge of finding commercial volumes of hydrocarbons has not yet been solved for most of the area. We propose that a new exploration strategy, including 3D EM acquisition, will significantly improve and accelerate the success in arctic frontier areas such as the Barents Sea in an environmentally benign way.