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The AAPG/Datapages Combined Publications Database

CSPG Special Publications


Sedimentary Basins and Basin-Forming Mechanisms — Memoir 12, 1987
Pages 75-85
Extensional Basins

Hydrocarbon Generation and Thermal Evolution in Parts of the Egersund Basin, Northern North Sea

Ulrich Ritter, T. Leslie Leith, Cedge M. Griffiths, Liv Schou


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.

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