Tideway (DEME’s Dutch subsidiary) was tasked with work including trenching, dredging, backfilling and pipe pulling, as well as the construction of a cofferdam for a Black Sea Gas Pipeline, which brings gas from Russia to Turkey via two 24-inch pipelines. The client, Saipem, is a joint venture between the Russian state company Gazprom and Italy’s ENI Group.
Linking the gas network of the Krasnodar region in southern Russia to the Turkish grid in Ankara is extremely difficult given that it is a 1,250 km-long connection, which includes a 386 km sea crossing between Russia and Turkey.
The seabed is not only ultra-deep, falling to a record depth of 2,141 metres, but also the profile of the seabed is very uneven.
The two pipelines had to withstand a pressure of 200 bar and had to be stabilised by special techniques. For this particular purpose Tideway brought in a dynamically positioned combined derrick lay vessel.
As always, the landfalls were the most crucial parts of the contract.
On the Turkish side, the shallow beach made pulling operations possible from the shore through a cofferdam. However, at Djugba in Russia, the high cliffs were difficult to access and there were no sandy beaches as in Turkey, making landfall operations much more complicated.
A Cutter Suction Dredger had to dig a trench in the rock and pulling was carried out from a barge. Although the techniques deployed at both shores were very different and represented difficult challenges, the project was carried out successfully in both countries.