Timing and Quantification of Significant Uplift and Erosion Resulting from 1D Basin Modelling Optimizations. Possible or Impossible?

Birger Dahl¹, George Butenko², and Ivar Meisingset^3
1University of Bergen, Bergen, Norway
²Sagex AS, Oslo, Norway
³Aker Kvaerner Geo AS, Oslo, Norway

The presented work from the North Viking Graben was carried out in 1989 in connection with the 13th Concession Round application. During 1D basin modelling optimisation of wells, the match between simulated and observed maturity parameters suggested that the known Neogene stratigraphy was incomplete. The data presented in well completion reports indicated a continous subsidence in Late Tertiary time. The best match to maturity data suggested an hiatus of 17 ma that included an initial fast sedimentation in Late Oligocene-Miocene filling the basin, followed by a rapid uplift and erosion in the Late-Miocene. The most significant uplift and erosion was estimated to be 600 700 m in Block 35/3. This event was synchronous with an important phase of the Alpine Orogeny in Central Europe, but its effects so far north were not referred to in the literature. Review of regional seismic data suggested that this phase of uplift and erosion in the North Viking Graben was associated to a broad bulge in the basin and a possible sea level fall without reactivation of the main fault system.
Several years later, mapping of the Miocene erosional surface in the north eastern part of the Viking and Sogn Graben Areas revealed erosion canyons with a relief of more than 100 ms These canyons had directions consistent with the uplift map produced during the 1 D optimalization work. Also, later studies (e.g. Løseth and Henriksen, 2005) document similar events and suggest that the Mid-Late Miocene compressional regime resulted in the domal features observed in the Møre and Vøring Basins which were not open to exploration in 1989.
Results of 3D basin modelling indicate that the hydrocarbon generation ceased during the Late Miocene uplift, but was reactivated by the rapid westward progradation of the Pliocene-Pleistocene sedimentation with deposition of over 1000m of sediments.
The Late Miocene uplift and erosion might have resulted in seal breach and/or tilting of some of the existing petroleum traps and larges quantities of petroleum may have been lost. Fluid inclusion and reservoir geochemistry studies show evidence of fossil OWC's. In certain “kitchen areas” where the uplift and erosion was larger than the Pliocene-Pleistocene sediment wedge hydrocarbon generation was not restarted. Areas where hydrocarbon generation has not occurred since Mid Miocene time should be regarded as less prospective.
A similar approach to understand and quantify erosional events have been successfully applied to other parts of the Norwegian Shelf, e.g. the Vøring Basin and the Barents Sea.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece