Porosity and permeability variability across a chalk reservoir in the Danish North Sea: Quantitative impacts of depositional and diagenetic processes

The Upper Cretaceous to Lower Paleocene Chalk Group in the North Sea comprises important reservoir targets for hydrocarbon and energy storage. quantitative impacts of mineralogy, chalk diagenesis oil saturation on petrophysics are often based general trends that cannot be directly applied engineering. present study aims at identifying quantitatively individual effects compaction cementation, porosity permeability by means detailed samplings mineralogical petrophysical analyses from base top Kraka reservoir. Special attention is brought visual inspection rock fabric its variations across order better constrain interpretations establish relationships within an otherwise scattered dataset. Porosity categorised into two trends, a diagenetic trend, which can both form tight rock. For containing >7% quartz > 4% clay, decreases linearly 35% 21% 0.5 mD 0.07 with increasing content. amount rather than clay appears as effective tool estimate properties impure chalk. Below 7% cementation decrease steps along transects oil- water-bearing intervals. A first step predominantly mechanical reducing >41% 37% 3 3.5 1.5–2.5 mD, respectively, followed phase chemical further deteriorates properties. In Ekofisk Fm., stylolitised deposits located adjacent chert horizons display singular do not fit observed trends. outliers likely result phases local early associated formation. Porosity-permeability functions uncertainty also proposed different controlling factors scales observation. instrumental building more realistic models assist geoscientists interpreting upscaling large geological data collected fields.