The Diagenetic Fingerprint of Rotliegend Sandstones in the Groningen Gas Field

Abstract. Permian Rotliegend sandstones form the main reservoir of the Groningen gas field, where reservoir quality is strongly influenced by diagenesis. This study presents the first field wide petrographic inventory of authigenic minerals, , their paragenesis, and spatial variations. Eodiagenesis under arid conditions formed hematite, clay coatings, and pervasive dolomite and anhydrite cements that stabilized the framework but reduced porosity. Mesodiagenesis involved feldspar dissolution and the precipitation of kaolinite, illite, chlorite, and limited quartz cement, with quartz growth commonly inhibited by clay coatings. Illite and chlorite are more abundant in northern playa margin facies, while kaolinite prevails in the south and is linked to feldspar alteration. Later uplift and reburial contributed little additional cementation and gas charge likely restricted large-scale fluid flow, limiting further cementation while localized influx from overlying and underlying strata may have occurred. Early dolomite was the most significant dominant porosity-reducing phase, whereas radial illite was volumetrically minor and had little impact. Overall, reservoir quality reflects the interplay of depositional environment, burial conditions, and local diagenetic processes. The results provide a framework for predicting spatial heterogeneity and assessing reservoir performance in Rotliegend sandstones.