The Impact of the High-Arctic Large Igneous Province on the Barents Sea Basin: Development and Petroleum System

Stephane Polteau¹, Sverre Planke¹, Jan Inge Faleide², Henrik Svensen³, Reidun Myklebust⁴, Fernando Corfu², Ivar Midtkandal², and Mikal G. Trulsvik^1
1Volcanic Basin Petroleum Research AS, Oslo, Norway.
²Department of Geosciences, University of Oslo, Oslo, Norway.
³Physics of Geological Processes, University of Oslo, Oslo, Norway.
⁴TGS-NOPEC, Asker, Norway.

The rapid thermal alteration of organic-rich sediments in contact aureoles around sill intrusions can produce large volumes of hydrocarbons that can be trapped or vented to the atmosphere. We have mapped an extensive sill complex in organic-rich sedimentary basins in the northern and eastern Barents Sea based on offshore geophysical data and onshore exposures. The 700 000 km² large sill complex intruded Permo-Triassic sequences in the East Barents Basin and on Svalbard. The assessment of the impact of the intrusive event on the basin development, the petroleum system, and the global environment requires precise information about the age and duration of the magmatism. We have collected dolerite samples from outcrops and boreholes on Svalbard during field work in April 2010, and from one borehole on Franz Josef Land, to date this igneous event. In addition, marine shales and a tuff layer were sampled in the Svalbard boreholes spanning the early Cretaceous Rurikfjellet, Helvetiafjellet, and Carolinefjellet formations. A comprehensive analysis program of these samples includes geochronology (Ar/Ar and zircon U/Pb), biostratigraphy (palynology), and geochemistry (ICP-MS, RockEval, TOC, δ¹³C). The geochronology shows that the sills were injected at 124.5 Ma on Svalbard and 120.3 Ma on Franz Josef Land. The volcanism was coeval with regional uplift and erosion in the north, documented by the dominantly marginal marine Barremian Helvetiafjellet Formation on Svalbard. We estimate that about 150 000 km³ of Permo-Triassic sediments were thermally altered by the intrusion of 75 000 km³ of magma in the Eastern Barents Basin. Our calculations show that up to 9000 Gt of carbon gases (82 trillions of BOE if the gas is methane) were potentially produced in the contact aureoles during the Barremian-Aptian igneous event. The aureole gases may still be trapped, and could partly fill giant gas fields directly overlying the sill complexes (e.g., the Stockmann gas field). However, a large proportion of the aureole gases was likely released. Even though no hydrothermal vent complexes have been identified, the near synchronicity between the oceanic anoxic Selli event (OAE1a) and the East Barents Sea magmatism points towards a possible causal mechanism between the Barents Sea intrusive event and the OAE1a.

 

AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.

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