Control of the Mode of Basin Formation on Petroleum Systems in the Central and East Barents Sea: Insight from Thermo-mechanical Modelling

Sebastien Gac

The Central and East parts of the Barents Sea are until now poorly explored regions but are highly promising regarding their oil and gas potential (Henriksen et al., 2011). It is well known that oil and gas accumulation in a sedimentary basin is a product of petroleum systems. The petroleum system concept embodies all the geological elements (source rock, reservoir rock and seal) and processes (hydrocarbon generation, migration and trap formation) required for effective oil and gas accumulation. Those elements and processes are controlled by the tectonic and thermal history of the sedimentary basin. The East Barents Sea is characterized by one of the deepest sedimentary basins in the world. Two competing hypotheses have been proposed for the formation of the deep East Barents Sea basin: 1) Permian-Triassic lithospheric extension (O’Leary et al., 2004) and 2) Permian-Triassic lithospheric shortening/buckling accompanied by metamorphism of mafic crustal heterogeneities (Artyushkov, 2005; Gac et al., 2012; 2013). Those two modes of basin formation might have different controls on petroleum systems. Extension and thinning of the lithosphere is accompanied by large heat input in the sediments followed by thermal cooling. Conversely, shortening/buckling of the lithosphere is accompanied by downwards advection of isotherms followed by warming-up of the sediments due to thermal relaxation. Those contrasting thermal histories of source rocks would result in different maturation patterns for kerogen. Furthermore, stress (extensional or compressional) accompanying deformation would largely influence the porosity of source and reservoir rocks. At last, folding accompanying shortening could provide traps for hydrocarbons. In order to evaluate the influence of the mode of basin formation on petroleum systems in the Central and East Barents Sea, 2D forward thermo-mechanical models of continental deformation based on the finite element method are developed. Consistent sedimentation is included. Different models are run, characterized by different modes of basin formation (extension or shortening/buckling). For each model, elements and processes forming the petroleum system (vitrinite reflectance of kerogen, oil/gas ratio, porosity of sediments and trap formation) are computed and compared with data issued from observed petroleum systems in the Barents Sea.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013