Sandstone Oseberg Formation

Diagenetic carbonate cement in reservoir sandstones of the Oseberg Formation (Brent Group) in the Oseberg field, Norwegian North Sea, occurs as disseminated siderite and ankerite, and as massively calcite-cemented intervals. Other diagenetic features include extensive feldspar dissolution and K-feldspar, quartz, kaolinite and dickite cements. Conditions of carbonate cementation are constrained on the basis of textural, geochemical and fluid inclusion evidence. 

Analytical data from 21 samples of carbonate-cemented sandstones of the Oseberg Formation are examined in this paper. These were selected from a set of 13 cores (157 thin sections) investigated as part of an integrated study of the diagenesis in the Oseberg Formation (Girard, 1995 Girard et al., 1995). The carbonate-cemented samples described here come from nine wells located in the Alpha... 

Lundegard, P.D. (1994) Mixing zone origin of C-depleted calcite cement Oseberg Formation sandstones (Middle Jurassic), Veslefrikk field, Norway. Geochim. Cosmochim. Acta, 58, 2661-2675. 

Plate 4. Patchy calcite cementation merging downwards to form an almost pervasively cemented interval. Mouth bar sandstone from the Middle Jurassic Oseberg Formation in the Veslefrikk Field, Norwegian North Sea. Width of core is 14 cm calcite-cemented areas are light grey. 

Isotopically light poikilotopic calcite was also reported by Walderhaug et al. (1989) in the Jurassic sandstones of the Fensfjord Formation in the nearby Brage field. Late diagenetic calcite, which seems to be volumetrically minor in Veslefrikk, constitutes the main, and apparently only, calcite generation in the Oseberg field. 

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