producing hydrocarbons onshore the Netherlands. This paper aims at comprehensively describing these relatively unknown reservoirs and speculating on additional play potential outside of the current production areas. The Muschelkalk formation consists of partially porous Lower and Upper Muschelkalk carbonates separated by tight Middle Muschelkalk evaporites. The 100 meter thick Lower Muschelkalk holds 1.9 bcm gas in the De Wijk field. The reservoir is a limestone-dolomite-marl succession producing from several decimetres thick calcisilitic dolo-mudstones encased in tight lime-mudstones. The reservoir shows a layer-cake-type architecture composed of sixteen cycles with thin, but laterally continuous porous units. Good reservoir facies is concentrated in the upper third of these cycles. Porosities vary from 6 to 27%, (average of 12%) and permeabilities range from 0.01 to 32 mD (average 0.06 mD). The reservoir rocks represent inner ramp sediments of a storm-dominated epeiric ramp. The 50 metres thick Upper ...