The TurkStream Offshore Pipeline is one of the last decade's most challenging projects in the offshore oil and gas industry. It is a major gas-transmission system that is pivotal to the transport of natural gas from the large Siberian reservoirs to the Turkish and European markets. The system consists of two subsea pipeline strings of more than 900 km each that cross the Black Sea through water depths of up to 2,200 m. Its large outer diameter of 32 inches makes it possible to transport a massive amount of 31.5 bcm natural gas per year from the Russian to the Turkish shore. A very thick wall of 39 mm is needed to ensure structural integrity.
The sheer size of the system and the conditions it will be operating in have come with many challenges. Several are discussed in this paper. Available technologies had to be advanced to the next level on many fronts to realise this project.
The work reported in this paper was carried out between 2010 and 2019.
The TurkStream Offshore Pipeline is a major gas-transmission system that is currently in operation and comprises two pipeline strings in up to 2200 m water depth. It connects large gas reservoirs in Russia to the Turkish gas-transportation network via the Black Sea, as shown in Fig. 1. The system currently has an annual capacity to transport 31.5 bcm of natural gas over approximately 940 km. The line pipe is longitudinally welded with a nominal outer diameter (D) of 813.0 mm (i.e., 32 inches) and wall thickness (t) of 39.0 mm. The material grade is DNV SAWL 450 with supplementary requirements F, D, U and (light) S as per DNV-OS-F101 (2010) plus project specifications.
The line pipe is externally coated using a three-layer polypropylene (3LPP) anti-corrosion coating. A liquid-epoxy flow coating has been applied on the inside to reduce the frictional pressure loss during operation, and more importantly, ease pre-commissioning and commissioning. Concrete weight coating is applied merely in shallow water to ensure on-bottom stability.
