Hydrodynamic Pressure Cell Systems in the Central Graben, North Sea
David Darby, Stuart Haszeldine, Cambell Fleming, Gary Couples
The sub-Cretaceous levels of the Central Graben can be divided into several
pressure cells. These cells are in a state of geological disequilibrium; the
basin will seek to re-equilibrate at hydrostatic pressure by releasing port
fluids. We have identified cells in the Central Graben where flow 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 located on an eroded intra-basinal high.
Upward release of pore fluid from the leak point into the overlying
normally-pressured regime is facilitated by the reduced thickness and elevated
unit permeability of the pressure seal
. The importance of this leak point has
been identified through pressure cell definition and potentiometric mapping
coupled to simulated regional overpressure evolution. Fluid flow from very deep
overpressured cells into the high causes an important temperature anomaly over
the leak point. Our model demon-rates 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 #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995