Hydrocarbon potential of The Norwegian-Danish Basin
More than 4,700 cuttings samples from the pre-Upper Cretaceous succession in 33 wells widely distributed in the Danish Basin and Fennoscandian Border Zone have been analysed (TOC determination and Rock-Eval pyrolysis).
The main task of the project is to investigate the most significant risk factor in hydrocarbon exploration in the Norwegian-Danish Basin the presence of good and mature source rocks. This will be achieved by developing a conceptual model for the development of the Mesozoic succession with special attention on the extension and quality of source rocks. The model will be based on a combined Geological/Geophysical/Geochemical study. The study will compile existing data and incorporate and produce new data. The main task will be mapping of recognizable sequence stratigraphic units combined with a study of their source rock potential. Further more it will be attempted to outline potential oil kitchens. The study will be carried out on released material. If new data becomes available during the project period they will be incorporated if permissions is granted. The results will be attempted published in relevant international magazines and presented on meetings and exhibitions
The screening data indicate that the only significant potential source rocks occur within the Toarcian (F-III and F-IV members of the Fjerritslev Formation). The Silurian Nøvling Formation and the Lower-Middle Triassic units in the Rønde-1 well are contaminated with drilling mud additives precluding source rock evaluation. The previously reported high TOC and HI values in the Upper Triassic-Jurassic succession in Felicia-1 are not confirmed by new GEUS analyses. In one well the Gassum Formation shows good potential source rocks; their formation seems to have been dependent on local depositional conditions in rim-synclines. Locally in the Fennoscandian Border Zone occur some good to excellent source rocks in the Frederikshavn Formation (Upper Jurassic-Lower Cretaceous), but burial depth is insufficient for thermal maturation. The Toarcian potential source rocks occur in distinct and local pods at three different stratigraphic levels. Their formation were related to the well-known regional oceanic anoxic event, basin-wide sea-level fluctuations, and local depressions that favoured primary organic production and preservation possibly facilitated by local banes. Their distribution is further limited by post-depositional erosion related to regional early Middle Jurassic uplift of most of the basin. An optimistic depth to the oil window is set at 3,250 m (corresponding to 0.6 %R_#omicron#) based on numerous vitrini reflectance data corrected for Late Cretaceous Early Cenozoic inversion and Late Cenozoic regional exhumation. In all the sections drilled sofar, the burial depth of the Toarcian before uplift was less than 3.250 m. The Toarcian is therefore thermally immature, and has not generated hydrocarbons in the known sections. Seismic mapping support the relatively shallow burial depth in the study area. It is thus concluded that the absence of mature source rocks is the major risk for successful hydrocarbon exploration in the Danish Basin and Fennoscandian Border Zone. A regional, mature source rock has not been found. Exploration should therefore be directed towards areas where an increased subsidence and/or heat flow have occurred, such as local fault-bounded grabens or rim-synclines developed near salt diapirs
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Contact
Øster Voldgade 10
DK-1350 København K, Denmark
Bidstrup, Torben (seniorforsker), 38142000, GEUS@GEUS.DK
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