Optimised production of the oil reserves
By optimising the drilling, production and transportation concept our highly-qualified employees have set international standards within the sector. Reliable drilling and optimised production of the oil reserves are the results of this team effort.
Until October 2005, specially constructed twin-hull ships were used to transport the oil to the port of Brunsbüttel, with its refinery connections. The Mittelplate extraction quantity was limited, however, by the tide-and-weather-sensitive ship transportation.
Secure pipeline installations improved the environmental balance sheet and the processing capacity
Since 2005, the oil has no longer been transferred by ship, but has been pumped through a pipeline from the Mittelplate Drilling and Production Island to the processing facilities of the Dieksand Land Station. This permits transportation that is independent of the weather and the tides. The throughput capacity of the process-technology plant located on land was more than doubled to 2.5 million tons a year with the commissioning of the pipeline. We invested more than 100 million euros in the construction of the pipeline and the extension of the processing facilities. The overall ecological benefit of the project is considerable. Each year there are approx. 2,000 fewer ship transfers, these having previously transported the oil from the Mittelplate island.
The technically demanding pipeline-laying concept was developed by geologists, engineers and environmental protection specialists and was then realised in keeping with the strict nature-conservation stipulations.
Two pipelines were laid under the mud flats and out to the Mittelplate Island, over a distance of 7.5 kilometres. On the land side a further 2.8 kilometres of piping led to the Dieksand processing plant. The piping for transportation of the crude oil has a diameter of 250 millimetres and the return-transport piping for the reservoir water is 150 millimetres. The water separated in the purification plant is returned to the reservoir to retain the pressure there and to help ensure an optimum production rate.
The sea pipelines were prefabricated in six sections and were drawn into parallel horizontal wells. This type of installation minimised the encroachment area in the mud environment. The pipes were placed at a depth of up to 20 metres to ensure that they would safely pass below the tidal creeks in the North Sea tidelands and the dykes. The weld connections of the drill strings were made in six building pits at a depth of five metres in each case. All laying work was completed according to plan and the pipeline went into operation in October 2005.
High-tech increases the production rate of Mittelplate oil
The target area in the reservoir lies at a depth of around 2,000 metres. To also be able to reach this from land (from Friedrichskoog), very long extended-reach drillings of up to 9,000 metres and more were made. A total of eight drillings since June 2000, as well as an onshore processing plant meanwhile allow around 372,000 tons of oil a year to be extracted. The drilling lengths achieved are some of the longest in the world.
Onshore production operations are controlled from the Dieksand Land Station. The processing plant, which separates Mittelplate oil into clean oil, natural gas and condensate and removes the accompanying water, is located here. The pipeline connection to Mittelplate and the additional processing of the oil required considerable modifications of the land station. The flow rate of the processing facilities was more than doubled from 1.2 to 2.5 million tons a year.
The high investments were worthwhile. The initial estimates of the Mittelplate reserves were steadily corrected upwards during the implementation of the project. To the 30 million tons of oil already extracted a further 20 to 25 million tons is currently estimated as being technically and economically recoverable.