Abstract

Thermal history and oil generation have been modelled for selected sites in the southern Egersund Basin using a total of six conceptual models, comprising three heat flow histories and two source rock profiles from wells 9/4-4 and 18/10-1. The different heat flow models lead to peak heat flow during rifting of between 46 and 65 milliwatts per square metre. (mW/m²) Present-day model maturities reflect these differences unsatisfactorily. Maximum temperatures were first reached in the Upper Cretaceous or lower Tertiary. Present-day model temperatures differ by hardly more than ±5°C. Neither maturity nor temperature can therefore satisfactorily distinguish between the different heat flow options. Oil generation has been modelled using available organic-geochemical source rock data and empirical oil generation and maturity models. In contrast to the central North Sea, only a minor proportion of the oil is generated from the equivalent of the Upper Jurassic “Kimmeridge Clay Formation” (Tau Formation); up to 90% is generated from underlying Jurassic rocks. Peak oil generation sets in during Late Cretaceous (model B) or Oligocene (models A and C). Oil generation from the Tau Formation reaches a peak during Oligocene (model B) or Subrecent (models A and C). Depending on the heat flow history used, oil generation has been going on at a constantly declining rate since Early (Mid) Tertiary.