How cementations affect the reservoir properties of the Bunter Sandstone Formation onshore Denmark

Abstract

The reservoir quality of the Early Triassic Bunter Sandstone Formation in southern Denmark is generally good, but locally variations in mineralogy and diagenesis may lower the porosity and permeability drastically. The reservoir properties are influenced by both the composition of the originally deposited sediment (the detrital mineralogy) and by the subsequent dissolution-precipitation processes resulting in various types of cementations (the authigenic mineralogy). Iron oxide/hydroxide coatings are commonly present, and they help preserve the primary porosity. Anhydrite, carbonate and halite cements, as well as clay clasts and intra-granular clay, reduce the reservoir quality in different degrees. There is an overall trend of positive correlation between grain size, porosity and permeability.