Sedimentology and diagenesis as ‘hydrocarbon exploration tools’ in the Late Permian Zechstein-2 Carbonate Member (NE Netherlands)

Hydrocarbon exploration in The Netherlands has a chequered history from serendipitous oil shows via chance oil/gas discoveries to finding the largest continental European oil field in 1943, followed by finding the largest gas field in the world in 1959. The present contribution traces the development of moderate to good porosity/permeability trends in depositional facies of Zechstein Stassfurt carbonates in a ‘gas play’ intermediate in significance between the above two plays but all in the northern part of The Netherlands. Various depositional facies in the Stassfurt carbonates were turned into ‘carbonate fabric units’ by diagenetic processes creating or occluding the porosity/permeability. This formed moderate to good gas reservoirs in barrier-shoal, open-marine shelf and proximal-slope carbonates in the subsurface of the province of Drenthe in the NE Netherlands. The diagenetic models forming these carbonate fabric units are linked to the variety of facies in a depositional model which shows explain and predicts the reservoir trends. Such depositional/diagenetic facies are ‘translated’ into characteristic petrophysical values recognisable on wire line logs in uncored wells, and in characteristic seismic expressions that show these trends in undrilled areas. This approach has been proven to be effective in delineating porosity trends, visualised by 3-D seismic in the Collendoornerveen field, and thus provides a new exploration ‘tool’ in hydrocarbon exploration