An Interpretation of Vitrinite Reflectance Data From the Southern North Sea Basin

Abstract

Summary Vitrinite reflectance data for the Carboniferous in 68 Southern North Sea Basin wells have been used to determine a maturity-depth relationship for the basin and to provide an estimate of basement inversion. The derived maturity-depth relationship is comparable with maturity gradients in other Paleozoic coal and gas basins known to have had similar geothermal histories. The earliest onset of gas generation in the Southern North Sea was in the late Jurassic following the accumulation of ± 11700 ft (3500 m) of sediment above the Carboniferous source beds. Estimates of inversion of the Sole Pit area using vitrinite data are similar to those based on shale velocity methods (± 1500 m maximum). In some areas the amount of inversion of the Carboniferous basement apparently exceeds that of the post-Zechstein section which may be attributed to removal of significant amounts of late Carboniferous strata during late Hercynian times; these areas are also associated with the principal gas discoveries in the basin.