The field was discovered in 1981 through the Mittelplate 1 well, which confirmed that the reservoir contained of crude oil. As early as the 1950s, geologists suspected the presence of oil off the German coast. Preliminary test drilling in the 1960s did indeed turn up indications of oil, though not in economically profitable quantities. The oil crisis of 1973 and 1979raised awareness of indigenous oil sources. In 1980 and 1981, exploration wells in the Mittelplate vicinity found oil in several sandstone layers. Due to the location of the field in an ecologically sensitive area, hydrographic, hydrodynamic and meteorological studies modelling storm, wave and ice-flow conditions were done, with the result that an artificial island holding a drilling and production facility was built in 1985.
Geology
The oil in the Mittelplate field is trapped in Dogger sandstones of uppermost Aalenian to lowermost Callovian in age. The five main sandstone reservoir units, known from oldest to youngest as the alpha-sand, beta-sand, gamma-sand, delta-sand and epsilon-sand, are separated by intervening sandy claystones, not of reservoir quality. The trap is formed on the flank of the Büsumsalt dome, with the hydrocarbons sealed up-dip by the edge of the salt dome. The overall top seal is provided by Lower Cretaceous mudstones. The source rock for the oil found at Mittelplate is thought to be the underlying Lower Jurassic Liassic organic-rich claystone.
Technical features
The island is protected by sheet piling measures at. The western section of the field includes 18 production wells. The first oil came onstream in 1987 and was delivered ashore on double hull barges. A new redevelopment plan included the construction of a land-based facility in Dieksand from which extended-reach production wells were to tap into the eastern part of the field. As per the development program, a pilot well and seven high-tech extended-reach well measuring at,,,,,, and a section cutting through the Büsum salt diapir were to ensure a faster exploitation of the field. The redevelopment plan also included construction of pipelines from the island to Friedrichskoog-Spitze and a pipeline to the Dieksand Land Station. This was expected to enable the Mittelplate consortium to transport up to 1 million tonnes or of oil a year. Oil is pumped ashore and water extracted during processing is then routed back by the second pipeline for reinjection into the lower section of the reservoir. The modified island facility now contains living accommodation for up to 96 people.
Ownership
The Mittelplate Consortium is operated by RWE Dea, but both RWEDea and Wintershall AG have 50% shares in the venture. Out of a total capital spending of €670 million by the consortium, €100 million was spent on construction of the pipeline transporting crude oil ashore and €50 million was spent on construction of a new T-150 drilling rig. Being an operator of the consortium, RWE Dea accounts for nearly 60% of total domestic oil production in Germany.
Production
Starting from October 1987, the field has been tapped in several sandstone layers at depths reaching. The size of the deposit was adjusted upward to over 100 million tons, of which 15 million tons were extracted by June 2005. The annual production of Mittelplate Island amounts to 900,000 tons of oil. Under prevailing conditions, about 40 million tons are still economically extractable. Since 2000, nearly horizontal wells have been extracting from the eastern part of the field directly from land on Dieksand / Friedrichskoog. The oil is piped from there to Brunsbüttel and onward to oil refineries in Hemmingstedt.
Safety and environmental protection
The companies developing the field spent a substantial part of €670 million already invested over 20 years into industrial safety and environmental protection programs due to unique location of the field in Wattenmeer tidelands. Pipe-laying in the area and production in the field have been in accord with National Parks Law. However, Greenpeace along with World Wildlife Fund have been active critics of the field development in Wattenmeer. The national park is home to nearly 4,000 species, 250 of which do not exist anywhere in the world but Wattenmeer. Up to 12 million migratory birds use the park rich of mussels, worms, snails, shrimp as a resting place. Nearly 200,000 shelducks are believed to gather around the Elbe river estuary each summer.
