Modelling of Hydrocarbon Generation Patterns in the Egersund Sub-Basin, North Sea.

摘要

Hydrocarbon generation in the Egersund Sub-Basin on the Norwegian continental shelf has been using empirical (Lopatin-type) and kinetic models and two protoptypes of source rocks from wells 9/4- 4 and 18/1-1. The amount of oil generated changes with initial heat flow, type of generation model, activation energies and source rock richness but does not follow a straigthforward pattern. For example at lower thermal histories the amount of oil generated up to the present changes exponentially with initial heat flow; variation due to change of activation energy distribution is linear to exponential, depending on heating rate; and variation due to source rock potential is linear. The empirical model for oil generation is less sensitive to temperatu- re and more sensitive to time than the kinetic models and appears to overestimate the amount of oil generated at low heating rates but underestimates it at high heating rates. Hydrocarbon yields predicted by the empirical model are usually 4 to 5 times higher than those predicted by the kinetic models. For the drainage area of well 9/2-1 variation of initial heat flow between 1.15 and 1.25 hfu (heat flow units) results in a variation of output yield by a factor three. If a minimum oil saturation of the pore volume of 10% is required for long-distance migration, the empirical model should have resulted in accumulations or oil shows also in the marginal drainage areas. Although not unambigous, the present hydrocarbon distribution can be explained best by generation from the kinetic model thermal histories represented by initial heat flows between 1.20 and 1.30 hfu. 25 refs., 8 figs., 3 tabs.