Regional Mapping of Sand Probability in Submarine Fans Offshore mid Norway

Lars Eikum and Erlend M. Jarsve
Fugro Multi Client Services, Oslo, Norway.

During the last decade, deep water exploration in the Møre and Vøring basins offshore Mid-Norway has lead to a number of world class gas discoveries in good quality homogeneous deep marine sandstones of Cretaceous and Tertiary age. These exploration successes came together with a series of disappointing wells that failed to encounter reservoir quality sands or movable hydrocarbons in commercial quantities.

The presence of reservoir sands of Paleocene and Cretaceous age varies along the margin through time. Delineation of individual sand depositional systems and the probability of finding these sands is one of the key risk factors in deep water exploration.

Detailed mapping of submarine fans and their sand content requires uniform and high quality long offset seismic data, which is often only provided by 3D data. Such data is rarely available in frontier exploration areas and the regional context is often absent due to the lack of uniform data coverage.

The string of dry holes without reservoir quality sandstones demonstrates our industry’s lack of ability to identify reservoirs based on the seismic data available at the time, along with poor calibration with well results. The pre-existing 2D and 3D seismic coverage has been limited either by patchy and scarce long offset 2D data (10,000m+) or insufficient offset.

Based on detailed mapping of more than 50,000km of uniform 2D data with 10,000 metres offset and 200,000km data with 3-6,000 metres offsets in the Norwegian Sea, we see a distinct pattern in seismic response in the Cretaceous and Paleogene. Well correlation and ties suggest that the long offset data is an excellent tool to delineate and map out the facies believed to be more sand prone. The integration of seismic response (AVO) and regional geological knowledge makes it possible to reduce the reservoir risk in frontier basins such as the deep water parts of the Norwegian Sea.

AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia