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Significant amounts of gas and oil have been produced in the Dutch on/offshore over the last 50 years. The extraction of large volumes of gas has resulted in major pressure depletion of the originally overpressured to highly overpressured gas reservoirs. The impact of local pressure depletion on the virgin pressure systems of aquifers connected to those reservoirs has not been studied in detail. This paper presents and discusses a new approach to assess the distribution and magnitude of such pressure changes in time and space in and around gas fields. The focus will be on Rotliegend gas fields since most gas fields in the Netherlands occur in Rotliegend reservoirs.

Shallow gas in the Dutch offshore predominantly occurs in shallow marine to continental deposits of the Plio-Pleistocene Eridanos delta (Fig. 1). This delta was fed by an ancient fluvio-deltaic system that prograded through Northwestern Europe due to simultaneous uplift of the Fennoscandinavian Shield and accelerated subsidence of the North Sea Basin. The dimensions of its drainage area and the thickness of the deltaic deposits make it one of the largest deltas and complex in the world. The origin of the shallow gas may be deep subsurface thermogenic sources or biogenic sources in shallower strata. It is either structurally trapped in anticlines associated with rising salt domes or occurs in stratigraphic or depositional traps.