The Diagenetic Fingerprint of Rotliegend Sandstones in the Groningen Gas Field

Permian Rotliegend sandstones in the Groningen gas field of the northeastern Netherlands were deposited in an arid continental setting and form Europe's largest onshore gas reservoir. Previous studies have documented aspects of their diagenetic evolution, yet the regional distribution and paragenetic relationships of authigenic minerals across the field have remained poorly constrained. This study presents the first field wide petrographic inventory of authigenic mineral assemblages, their paragenesis, and their regional distribution. During early diagenesis, hematite, clay coatings, and pervasive dolomite and anhydrite cements formed, stabilizing the grain framework while reducing porosity. Subsequent burial diagenesis involved feldspar dissolution and the precipitation of kaolinite, illite, chlorite, and limited quartz cement, with the latter commonly inhibited by clay coatings during precipitation. Authigenic mineral assemblages vary systematically along a south-north proximal-distal trend across the field, with illite and chlorite dominating in more distal, playa-influenced northern intervals, whereas kaolinite prevails in more proximal southern sandstones. These patterns reflect depositional control on early pore-water conditions and clay-coating development, which in turn controlled subsequent diagenetic pathways, while burial conditions acted as a secondary influence (e.g. for quartz cement and late illite–chlorite formation). Later uplift and reburial contributed little additional cementation, suggesting that most mineral growth occurred during the initial burial stage. Early dolomite was the most significant dominant porosity-reducing phase (5-40%), whereas radial illite was volumetrically minor (<6%) and had little impact. Overall, the observed authigenic mineral assemblages reflect the interplay between depositional setting and internal diagenetic processes with little indication of large-scale external fluid influx. The results provide a framework for predicting spatial heterogeneity and assessing reservoir performance in Rotliegend sandstones.