Abstract: Hydrodynamic Flow in the Central Graben, North Sea

David Darby, Campbell Fleming, Stuart Haszeldine, Gary Couples

We present a model of pressure distribution in the Central Graben of the North Sea based on the concept of a hydraulically continuous flow system.

The sub-Cretaceous levels of the Central Graben can be divided into several pressure cells. These overpressured cells are in a state of disequilibrium; the system will seek to re-equilibrate at hydrostatic pressure by releasing pore fluids. We have identified cells in the Central Graben where hydrodynamic flow of pore fluids is predominantly lateral. Other cells have restricted lateral flow due to structural position in the hydrodynamic flow system, and fluid flow is predominantly vertical. We have identified pathways of potential pressure-driven flow towards a regional leak point where upward release of fluid into the overlying normally-pressured regime is favoured by structural position and the absence of effective vertical barriers. The importance of this leak point has been identi ied from pressure cell definition and potentiometric mapping coupled to simulated regional overpressure evolution. Fluid flow from deep overpressured cells into the high causes an important heat flow anomaly over this regional leak point. Our model demonstrates a direct relationship between the position and characteristics of the pressure seal and the cell position in the hydrodynamic system.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994