Lateral transfer: a source of additional overpressure?

Overpressure generated by disequilibrium compaction can be enhanced at stru ctural crests by the lateral transfer of fluids from deep, overpressured pa rts of a basin along laterally extensive inclined aquifers. Fluid flow mode lling shows that the effect of an inclined aquifer ranges from being minima l to being a significant contributor (>10 MPa) to crestal pore pressures de pending on the style of structural evolution, the burial rate and the aquif er relief. Dynamic fluid flow models show that the Centroid Concept, a meth od for estimating crestal pressures based on a static view of subsurface fl uid pressures, does not in general predict the pressure distribution associ ated with a dipping aquifer. A case study is presented from the Central Nor th Sea where the Pre-Cretaceous reservoir forms part of an aquifer with 2.5 km of relief from the structural crest to the low point. The inclined aqui fer is covered by a ubiquitous low permeability layer and has undergone ext remely rapid recent burial (> 500 m/ Ma). As expected from the generic mode lling analysis, this combination of factors means that lateral transfer has a minor effect on the pressure development in the case study. (C) 2000 Els evier Science Ltd. All right's reserved.