--> Abstract: Milking the Goat: Revised Reservoir Characterisation of the Åre Formation, Heidrun Field, Offshore Mid-Norway, by Camilla Thrana, Mali Brekken, Arve Næss, Simon Leary, and Stuart Gowland; #90082 (2008)

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Milking the Goat: Revised Reservoir Characterisation of the Åre Formation, Heidrun Field, Offshore Mid-Norway

Camilla Thrana1, Mali Brekken1, Arve Næss1, Simon Leary1, and Stuart Gowland2
1StatoilHydro ASA, NO-7501 Stjørdal, Norway
2Ichron Limited, Cheshire, United Kingdom

The Jurassic reservoirs of the Heidrun Field, offshore Mid-Norway, have so far produced over 114 MSm3 of oil. The oil recovery of the fluviodeltaic (Rhaetian-Sinemurian) Åre Formation is the lowest among the reservoir formations, which makes this an important stratigraphic interval when it comes to remaining reserves and IOR potential. In order to address challenges related to stratigraphic correlation and detailed reservoir modelling, a major core and wireline log based reservoir characterisation study of the Åre Formation has been performed. Main results from this study include a new facies analysis and a revised stratigraphic reservoir zonation. This new stratigraphic framework defines seven main zones, reflecting an overall transgressive development of the formation; from non-marine coastal plain in the lowermost part (Åre 1-2), marginal-marine lower delta plain in the middle (Åre 3-5) and tidally-dominated estuarine and open marine in the uppermost part (Åre 6-7). These reservoir zones represent packages of genetically linked facies, bounded by field-wide, correlateable candidate flooding surfaces. Based on this constrained stratigraphic framework, better and more accurate predictions of the distribution and geometry of hydrocarbon bearing facies can be made.

The implementation of the new reservoir zonation was completed in 2007. All the 90 wells with Åre Formation stratigraphy have been re-interpreted, and the new stratigraphic framework has been applied in a recent update of the full-field geological model. This reservoir zonation scheme has proven to be more robust than previous models and has provided a good platform for improved stratigraphic control during drilling operations. Long-term benefits would also include more precise production forecast, better drainage strategies and well solutions.

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