The effects of uplift and erosion on the petroleum systems in the southwestern Barents Sea: Insights from seismic data and 2D petroleum systems modelling

Abstract

In the past three decades, the hydrocarbon prospectivity has been enigmatic in the southwestern Barents Sea as gas discoveries have dominated over oil. However, more recent discoveries indicate oil potential, especially in the Polheim Platform and Hoop Complex areas. Cenozoic uplift and erosion episodes are critical because they control the duration and depth of maximum burial of source rocks and the reduction of porosity of reservoir rocks due to diagenetic processes at larger depth and increased temperatures. Modelling of interpreted horizons from the southwestern Barents Sea provide a best-fit realization of the basin-scale sedimentary filling from the post-rifting in the Jurassic until the Last Glacial Maximum. 2D basin modelling was performed across one regional seismic section crossing the southwestern Barents Sea. For calibration of the 2D model, 1D modelling was performed for a selected number of wells in the region by integrating different estimates of net apparent erosion (velocity inversion of wells, interpreted profiles and structure maps as well as from temperature and vitrinite reflectance data) in order to assess the burial, thermal and maturity history of the source rocks at various well locations as well as along the 2D profile. Simulation results show that the Upper Jurassic source rock is immature to marginal mature in the central and eastern parts of the Norwegian Barents Sea. The western part is characterised by high chargeability of traps associated with rich source kitchens and porous reservoir rocks. Although not proven by commercial discoveries, there are evidences that the Permian Ørret and the Lower-Middle Triassic basal Klappmyss and basal Kobbe shales may be important gas-prone source rocks in the eastern Norwegian Barents Sea. Consequently, the exploration must rely on the Triassic and/or Palaeozoic source rocks in the eastern area.