Offshore wells reach a depth of 3,000 meters

Drilling operations on Mittelplate Drilling and Production Island have also been incident-free since production began in 1987. Operating in an area with a minimal footprint, 25 wells have meanwhile been drilled to develop the western sections of the oil field. They penetrate to depths of up to 3,000 meters and are deviated in various directions – in some cases running horizontally through the reservoir. Annual production volumes have steadily increased. Due to the advanced exploitation stage of the reservoir, signs of a production decline have been evident in recent years. By June 2010, 14 million mt of crude oil had been produced from these offshore wells.

Heavy-duty electrically operated high-tech drilling rig

The offshore field development is now being conducted with a new, heavy-duty electrically operated high-tech drilling rig that has been in action since end-2005.

Rolling cutter rock bit   At a cost of around € 50 million, the T-150 rig is one of the most modern drilling rigs of its kind in Europe. It features special equipment to allow it to operate in the ecologically sensitive Wattenmeer tidelands without harming the environment. With its drilling lengths of approx. 8,000 meters, the T-150 is capable of developing the Mittelplate oil field by sinking additional wells.

First multilateral well produces oil

In October 2010, Germany’s first multilateral well started producing oil from the Mittelplate field. The high-tech well A23 will counter the natural decline in production from the oil field. The results are positive: some 700 cubic metres of crude are produced on a daily basis.

Engineering

The A23 is a so-called dual-lateral well: in an already completed well, a hole is cut in the casing as a starting point for a lateral branch. Depending on the type of reservoir and the type of junctions put in place, it is possible to drill several lateral branches extending from a parent well – this is referred to as a “multilateral well”. This technique allows multiple targets within a reservoir to be tapped through a single well. .

Structure of the A23 dual-lateral well 

Drilling path halved

In the case of the A23 well, applying this method meant that the 4,000 metres down to the reservoir located in the Dogger Beta sandstone formation had to be drilled once only in order to reach three separate targets. Two of the targets were reached through the main well, and the third by drilling a 1,300-metre lateral branch. Instead of requiring three separate wells with a combined length of about 14 kilometres, the total length of the drilling paths in the A23 well is only 7,300 metres. Yet another advantage is that up on the surface, only one borehole is needed to accommodate two production lines in the rig cellar on Mittelplate Drilling and Production Island.

It is a long-term objective to ramp up the use of multilateral wells in the continued development of the Mittelplate reservoir.