Dual hydraulic behaviour of the Chalk in the Netherlands North Sea

Information on the sedimentary development, seismic stratigraphy and burial compaction of the Chalk Group in the Netherlands North Sea was combined with pressure data and basin modelling to investigate the hydraulic behaviour of the Chalk Group in the Central Graben and Schill Grund High. The preliminary results of this integrated study indicate that the undercompacted Chalk of reduced thickness (0–300 m) in the inverted Central Graben behaves as an aquifer. In contrast it was found that the normally compacted, mostly pelagic, Chalk of thickness 600–1200 m on the adjacent Schill Grund High acts as an aquitard with permeabilities comparable to those of shales.