Geodynamic and hydrodynamic evolution of the Broad Fourteens Basin and thedevelopment of its petroleum systems: an integrated 2D basin modelling approach

Results of integrated 2D basin modelling indicate that both sedimentary loa ding and gas generation play an important role in the overpressure history of the Broad Fourteens Basin. We analysed the influence of time-dependent p ermeability of faults on the overpressure history and evolution of petroleu m systems. We favour time-dependent permeability of faults as the most like ly option to explain the present-day near-hydrostatic conditions in the bas in, the known location of oil fields, and the location and characteristics of the gas occurrences. The model results further show that the difference in timing of oil charging of the P9 and Q1 Lower Cretaceous oil reservoirs, explains the observed differences in geochemical composition of the accumu lated oils. The biodegraded and water-washed nature of the pre-inversion ch arged Q1 oil reservoir is consistent with the concentrated topography-induc ed groundwater flow through the Lower Cretaceous reservoir units during the Late Cretaceous inversion period. Late charging of the oil reservoir in th e P9 area explains the non-biodegraded character of the accumulated oils. P resent-day conditions in the Broad Fourteens Basin are near-hydrostatic. In general, this paper shows that paleohydrodynamic conditions and time-depen dent permeability of the hydrogeological framework have influenced signific antly the petroleum systems in the basin. (C) 2000 Elsevier Science B.V. Al l rights reserved.