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AAPG Bulletin

Abstract

AAPG Bulletin, V. 92, No. 9 (September 2008), P. 1191-1223.

Copyright copy2008. The American Association of Petroleum Geologists. All rights reserved.

DOI:10.1306/06180808028

Geochemically driven exploration models in uplifted areas: Examples from the Norwegian Barents Sea

S. E. Ohm,1 D. A. Karlsen,2 T. J. F. Austin3

1ConocoPhillips Norge, North Sea Business Unit, P.O. Box 220, 4098 Tananger, Norway; and Institute for Geosciences, P.O. Box 1047, University of Oslo, Blindern N-0316, Oslo, Norway; [email protected]
2Institute for Geosciences, P.O. Box 1047, University of Oslo, Blindern N-0316, Oslo, Norway
3ConocoPhillips Norge, North Sea Business Unit, P.O. Box 220, 4098 Tananger, Norway

ABSTRACT

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 Pliocene-Pleistocene have caused the depletion of hydrocarbon accumulations in the region. 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. Therefore, we expect that discoveries will be made in distal basin settings, particularly 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 several different stratigraphic source intervals. This suggests that Triassic and Paleozoic oils may be trapped below the presently drilled targets, which are mostly Jurassic in the Hammerfest Basin and older to the north and east. Deeper exploration targets also stand a higher chance of containing oil because the amount of gas being released from oil during uplift, erosion, and subsequent pressure release is lower. Uplift and erosion are followed by a reduction in temperature. This is why hydrocarbon generation is believed to have ended in uplifted areas. Some discoveries in this data set suggest, however, a significant fresh gas charge.

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