Question of oil-gas prospects in northern regions of the Barents-Kara shelf (Franz-Viktor Trough)

Abstract

The significant hydrocarbon potential of the shelf areas of the Barents and Kara Seas has been demonstrated by the discovery of very large gas and gas condensate fields in their southern areas. Against this background the increase in oil reserves has not been so significant. Nevertheless there is a geologic basis for predicting large zones of oil accumulation in the north of the Barents-Kara basin, which is an area of border highs. First of all, the depth to source beds is not great, and this provides for the generation of mostly liquid hydrocarbons. The neotectonic environment was also more favourable for formation and preservation of oil pools. Areas of this type are characterised by large zones of oil and bitumen accumulation related to lateral migration of hydrocarbon fluids from more subsided parts of oil-gas basins. All this is substantiated by much geochemical data derived from study of bitumen shows on Franz Josef Land and bottom samples from the surrounding offshore areas. The bitumen shows are largely viscous and solid natural bitumens. Their content in host rock is comparatively insignificant at fractions of a percent. All this indicates migration of predominantly liquid hydrocarbons from deeper horizons of the sedimentary cover as well as absence of significant surface precipitation accompanying destruction of oil pools. In this light the region may be regarded as favourable for oil. It is therefore important that geochemical anomalies be recognised in areas of local positive structures in the north of the Barents-Kara shelf. Information has been gathered in recent years in the Franz-Viktor Trough that indicates a large swell-like structure of north-south trend in its southern part (see Figures 1 & 2). It is designated as the Ladin High in connection with recovery of sediments of the Ladin Stage at station 52 (Figure 2). Reflection and common depth point seismic profiling show the Ladin High as clearly expressed in the relief of the Precambrian (Vendian) basement. Its dimensions are 110 km x 20-40 km. Its base is outlined by the 3 km structure contour, and the crest is at a depth of 1.5-1.7 km. Ladin High retains its inherited form in the Phanerozoic cover, although more gentle, particularly in its upper part. Small cupolas that measure 10-20 km in cross section and with amplitudes of 0.4-0.6 km have been mapped on the reflection profiles. These coincide in direction with the trend of the Ladin High (See Figure 3).