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Geochemically Driven Exploration Models in Uplifted Areas: Examples from the Norwegian Barents Sea

Ohm, Sverre E.1; Karlsen, Dag A.2; Austin, Tim J.1
1 Exploration, ConocoPhillips Norge, North Sea Business Unit, Stavanger, Norway.
2 Institute for Geosciences, University of Oslo, Oslo, Norway.

The Norwegian Barents Sea with multiple source rock intervals represents a prime example of an overfilled petroleum system. However, several episodes of uplift and erosion from the Paleocene until the Plio-Pleistocene have caused depletion of hydrocarbon accumulations in the region. It is important to realize that these uplift events were not only potentially catastrophic but have also caused the redistribution of the remaining oil and gas over laterally large distances in the Barents Sea region. This redistribution directed petroleum to distal parts of the various hydrocarbon generating basins, thus charging traps, which otherwise would not have been reached. It is therefore, to be expected that discoveries will be made in distal basin settings, particular in traps with partly leaking cap-rocks which can bleed-off gas and thereby retain oil. Many oil accumulations in the region represent various mixtures of oils from a number of different stratigraphic source intervals. This suggests that Triassic and Paleozoic oils may be trapped below the presently drilled targets, which are mostly of Jurassic age in the Hammerfest Basin and older to the north and eastwards. Deeper exploration targets also stand a higher chance of containing oil as the amount of gas being released from oil during uplift, erosion and subsequent pressure release is lower. Uplift and erosion is followed by a reduction in temperature. This is why hydrocarbon generation is believed to have ended in uplifted areas. Some discoveries in this dataset suggest, however, a significant fresh gas charge.

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009