The Effect of Improved Palaeobathymetry Estimation in Hydrocarbon Migration Modelling

By

 Tomas Kjennerud¹, Oyvind Sylta¹, Martin Hamborg¹, Stein Tore Wien¹

(1) SINTEF Petroleum Research, Trondheim, Norway

 Palaeobathymetry is a crucial input in the modelling of hydrocarbon migration through geological time, as even small changes in the basin morphology may affect the amount of trapped hydrocarbons. Commonly, palaeo-water depth in basin models is either ignored or treated as a flat surface with fixed water depth. Considerations of 2D or 3D bathymetry though geological time are rare. Palaeobathymetry is in the present work estimated in 3D by combining relevant information from depositional geometries, sedimentological indicators of shallow or zero water depth and micropalaeontological interpretation from cores and cuttings. In addition, decompaction and flexural isostasy are accounted for. Several tests on data from the Norwegian continental shelf have been carried out in order to quantify the significance of palaeobathymetry in modelling. In each test a separate scenario was carried out, whereby palaeobathymetry was ignored. It has been shown that constrained palaeobathymetry may change the hydrocarbon migration direction through geological time, indicating that both the hydrocarbon fill history and phase trapping history will be different. There are no easy way of determining which hydrocarbon traps in a basin that are sensitive to palaeobathymetric input and which are not, except for modelling the whole system.