EAGE

Kopenhagen

11.-14.Juni

Busch B, Hilgers C, Adelmann D

Busch B

earthdoc.eage.org

Reservoir quality in deeply buried sandstone reservoirs (>4000 m burial depth) is often controlled by clay minerals, as cements and replacements. However, the presence of clay minerals in sandstones can also improve reservoir properties if the minerals are present as grain coatings, inhibiting or reducing syntaxial quartz overgrowth cementation. If e.g. illite is present at grain contacts however, reservoir properties might again be deteriorated, due to an increase in chemical compaction (or pressure solution). This complex interaction of geochemical, depositional, and mechanical processes need to be understood and accounted for in reservoir quality modelling. In the presented case study from the Permian Rotliegendes in northern Germany, a complex reservoir setting is introduced, which is affected by a complex interaction of aforementioned processes. Especially illite grain coating textures affect the compaction and permeability development in the reservoir interval. Three different grain coating characteristics (i.e. tangential, radial, and short radial) can be optically distinguished. Tangential grain coatings, present at grain contacts, enhance chemical compaction, whereas both radial phases contribute less to chemical compaction. Reservoir quality benefits most from short radial grain coatings, whereas radial and tangential types do not show a definitive impact on petrophysical data.