The Ostsee Anbindungsleitung Subsea Pipeline is located in Germany. (Credit: GASCADE Gastransport GmbH)
Gascade completed the construction of the pipeline in January 2024. (Credit: GASCADE Gastransport GmbH)
Drone photo of Castoro 10 vessel. (Credit: © ABL Group)

The Ostsee Anbindungsleitung (OAL) is a nearly 50km-long offshore pipeline in Germany that connects the planned liquefied natural gas (LNG) terminal in the port of Mukran on the island of Rügen with the pipeline network in Lubmin.

Gascade Gastransport, a natural gas and oil transportation services provider, completed the construction of the pipeline in January 2024.

German transmission system operator Fluxys Deutschland acquired a 25% share in OAL in April 2024.

The pipeline is expected to commence transporting gas in February 2024.

Ostsee Anbindungsleitung Route

The OAL pipeline consists of four sections: the Lubmin land section; the sea section from Lubmin to Kilometre Point 26 (KP 26); the sea section from KP 26 to Mukran; and the land section in Mukran.

The construction of each section required independent approvals from mining authority Bergamt Stralsund.

The Lumbin land section was approved in February 2023, and the sea section from Lumbin to KP 26 in August 2023.

Sea section from KP 26 to Mukran was approved in October 2023, followed by the green light for the land section in Mukran in August 2023.

OAL Construction Details

The 48-inch offshore OAL Pipeline is a high-strength steel pipe with a diameter of 1.2m and a wall thickness of at least 26.8mm.

The pipeline is provided with a concrete casing of 90mm to ensure stability. It is buried with a covering ranging from 0.5m to 2.55m depending upon the local conditions.

The process of laying the pipeline comprised three steps- construction of a pipe trench; welding and laying of the pipe string; and backfilling and restoration of the seabed.

A pipe trench was built with the use of dredging equipment and the pipeline was laid on the bottom of the pipe trench. The dredged material was transported via hopper barges to an underwater storage facility.

The individual pipes were welded together to create a pipe string, which was laid into the trench on the seabed in a controlled S-curve. This is known as the S-lay process, a method of laying big offshore pipelines over long distances at average water depths.

In the final laying step, called Above-Water-Tie-In (AWTI), all individual pipe strings are joined together. During the construction of the OAL pipeline, two AWTIs were conducted.

After laying the pipeline, the pipe trench was backfilled with a sand-gravel mixture as the first layer and the original material from the trench as the second layer.

Benefits of OAL

The OAL subsea pipeline will strengthen the supply security of Germany by feeding the re-gasified LNG into the German Gas Grid.

The LNG terminal in the port of Mukran will include two Floating Storage and Regasification Units (FSRUs).

The LNG terminal will be developed by Deutsche ReGas. Gascade, as the transmission system operator, will connect the terminal to the gas transmission system of Germany.

In future, the OAL pipeline can be converted to support green hydrogen transport. It can feed green hydrogen into the German Hydrogen Core Network through the entry point in Mukran.

The green hydrogen will be transported southwards to the industrial consumption centres located in the eastern and southern Hesse and Baden-Württemberg, as part of the Flow-Making Hydrogen Happen Project.

According to Gascade, the OAL pipeline, along with the EUGAL and OPAL long-distance pipelines, would provide substantial transport capacities from the Lumbin coast in the northeast to the main consumption centres in Germany and Central and South-Eastern Europe.

Contractors Involved

In February 2024, energy and marine consultancy ABL carried out the marine warranty survey scope associated with the OAL subsea pipeline. The company oversaw the transportation and installation (T&I) operations related to the pipeline.

Gascade completed the construction of the offshore pipeline with StreamTec Solutions in 18 months. Italian oilfield services company Saipem was also associated with the project and supported the installation of a 48-inch gas pipeline using its pipelay vessel Castoro 10.