TECHNICAL CONDITIONS OF CONSTRUCTION AND OPERATION OF THE GAS PIPELINE ON THE BOTTOM OF THE BALTIC SEA INVESTMENT DESIGN

1. TECHNICAL CONDITIONS OF CONSTRUCTION AND OPERATION OF THE GAS PIPELINE ON THE BOTTOM OF THE BALTIC SEAINVESTMENT DESIGN ASSUMPTIONS Prof. Bolesław Mazurkiewicz – Technical University in Gdańsk

2. ISSUES 1. Undersea pipeline design process 2. Laying of the undersea pipelines 3. Protection of the undersea pipelines 4. Intersection of the undersea pipelines and their connection to the offshore platforms

3. UNDERSEA PIPELINE DESIGN PROCESS I Stages: an initial stage measurement and investigation stage and data collection stage of design works laying stage II An initial or preliminary stage: type of transported medium outer diameter design pressure maximal and minimal design temperatures Scheduled pipeline route anticipated operation period type and quality of the pipeline structure, ballasting and protecting materials anticorrosive protection systems pipeline wall thickness, ballasting jacket thickness, weight in immersed condition and depth under sea bottom

4. IIIMeasurement and test stage and data collection geophysical investigations  bathymetrical investigations  geotechnical investigations  oceanographical investigations IV Design work stage an initial designfor justification of advisibility of selected route or necessity to change it technical design being basis for the pipeline implementation on selected route. Pipeline division into design sections differing definitely in bathymetry, design wave, geotechnical conditions and environment risks. Decision on necessity to immerse pipeline below the sea bottom. Determination of design safety coefficient within pipeline stability and strength. V Laying stage

5. Actions on undersea pipeline

6. Dangers threating the sea pipelines

7. Laying of the undersea pipelines • legend: • Pływaki = floats • Układanie rurociągów za pomocą.... = Pipeline laying by means of: • barge up to 25.0 m depth; • semi-submersible pipeline laying platform up to 300 m; • pipeline laying vessel up to 3 000 m (depending on type of stinger’s type).

8. INTERACTION DURING LAYING • LEGEND: • siły pionowe = vertical forces • barka = barge • siła ciągnienia = tension force • wysięgnik = stinger • siły poziome = horizontal forces • dno morza = sea bottom • profil prądów …. = crosswise current profile • węzłów = knots

11. Preventive activity in case of dangers threatening undersea pipelines

12. Current requirements concerning large diameter pipeline burying (> 750 mm)

14. Pipeline protection methods • Not protected pipeline rests on the bottom • Ballasted pipelines • Pipelines on stakes • Pipelines on supports (saddles) • Anchoraged pipeline • Rinsed out pipeline • Immersed pipeline – natural backfilling • Immersed pipeline – backfilling ( cover) of rock blocks • Immersed pipeline - concrete cover

15. Methods of undersea pipeline burying below sea bottom • Stream method (hydraulic loosening) • Sandy soil liquefaction method • Mechanical cutting method (deepening) • Plowing method (plowing)

16. Evaluation of trench deepening

17. Damage risk of the undersea pipelines

18. Intersection of the undersea pipelines • Types of the pipeline intersection solutions: • existing pipeline, • new pipeline • concrete supports, • Bags with injection mortar laid in piles, • begs with sand and cement laid in piles • hard rubber saddles • separator • injection • pipes for mortar injection • pipeline clamped with clamping ring fixed to support • support made with framework consisting of pipes • conection of support of bottom by means of ground anchors

19. Connection of the undersea pipelines to the offshore platforms • Connection of the pipelines with conventional type riser: • hinge connection using rotational connectors; • connection with use of dog’s leg type pipe section; • connection by means of hyperbaric welding; • connection with use of a straight section; • deck; • platform base.