The Mittelplate oil field

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The Mittelplate oil field with its 600 × 10 6 BOIP is Germany’s largest oil field and lies offshore Germany in coastal tidal flats about 100 km northwest of Hamburg at the mouth of the River Elbe estuary, some 25km northeast of Cuxhaven. It is located in the Westholstein Jura Trough with its flanking salt walls, Oldensworth and Heide. The discovery well Mittelplate 1 was drilled in 1980 by the consortium RWE Dea AG and Wintershall AG. The prospects targeted by the Mittelplate 1 well were Middle Jurassic Dogger sandstone reservoirs. At the time only 2D data was available to the group and only a few seismic lines defined the play. The discovery well encountered two separate oil columns within the Middle Jurassic ‘Mittelplate’ sands which, when tested, flowed low gravity oil from four sandstone reservoir horizons at a depth of 2136–2743m below sea level. In 1981 three appraisal wells were drilled, confirming the structure with initial recoverable reserves estimated to be at around 200 × 10 6 BO. The distance of the field to the coast is between 7 and 13 kmwith a N–S extension of more than 10km straddling the western flank of the Büsum salt dome. After building an artificial drilling and production island in 1985, 15 wells have been drilled since 1986 from the Mittelplate-A platform draining the central part of the field. Along with the acquiring of new 3D seismic in 1997 in the area between the appraisal wells Mittelplate 2 and Mittelplate 3, a pilot project was initiated to develop the field through extended reach wells from onshore. Three wells were drilled from the Mittelplate island to the salt dome to verify geology and drilling requirements. At the same time one well, the Dieksand 1, was drilled from the shore to investigate the situation from the onshore side. After only half a year of engineering time, the first extended reach drilling (ERD) well, Dieksand 2, was spudded, drilled more than 3600m horizontally through the Büsum salt dome and was successfully completed at a TD of 7727min 1998. Since then a further six ERD wells have been drilled from onshore reaching a maximum length of 9275mMD. After 17 years of undisturbed and accident-free operation, the Mittelplate group is now planning to investigate the development of the southern and northern part of the field with horizontal wells of more than 8km from the Mittelplate-A platform location.