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  1. 1. Overview to Subsea System Sandeep S Rangapure R 160206025 M.Tech ƛ Pipeline Engineering
  2. 2. Well head Platform Riser Process Platform Pipeline crossing Expansion Spool Piece To shore Grouted Supporting bag Export lines Well head Existing line Subsea mainfold Tie in Riser Flowlines or Pipelines Well head Figure 1.1 Subsea System & Flowlines
  3. 3. Introduction Subsea Pipelines are used for the transportation of offshore Hydrocarbons from one Platform to another and or Platform to Shore
  5. 5. Pipelines are used for a number of purposes in the development of offshore hydrocarbon resources These include e.g.: Export (transportation) pipelines Pipeline bundles. Flowlines to transfer product from a platform to export lines Water injection or chemical injection Flowlines Flowlines to transfer product between platforms Subsea manifolds and satellite wells;
  6. 6. SUBMARINE PIPELINE SYSTEMS PIPELINE Pipeline is defined as the part of a pipeline system which is located below the water surface at maximum tide (except for pipeline risers) Pipeline may be resting wholly or intermittently on, or buried below, the sea bottom PIPELINE COMPONENTS Any items which are integral part of pipeline system such as flanges, tees, bends, reducers and valves PIPELINE SYSTEM An inter connected system of submarine pipelines, their risers, supports, isolation valves, all integrated piping components, associated piping system and the corrosion protection system
  7. 7. Risers A Riser is a conducting pipe connecting sub-sea wellheads, templates or pipelines to equipment located on a buoyant or fixed offshore structure. Types of riser Rigid riser - for shallow water Catenary steel riser - for deep water Flexible riser - for deep and shallow water Riser clamp Riser are supported/guided from the jacket members through clamps Types of Clamp Hanger clamp Fixed clamp Adjustable clamp
  8. 8. Riser Clamp (Welding to Jacket member)
  9. 9. Restrained lines Pipelines which cannot expand or contract in the longitudinal direction due to fixed supports or friction between the pipe and soil Unrestrained lines Pipelines without substantial axial restraint. (Maximum one fixed support and no substantial friction). Platform Platform FL 1 FL 3 FL 4 Hanger clamp level Sea surface level Riser 1 FL 21 FL 20 FL 19 Riser 2 73.5 m 74 m FL 5 0.00 m 2 m FL 2 7.5 m 7.5 m 2 m 7.5 m 7.5 m FL 22 1:7 1:7 FL 18 Sea bed 14 m 112 m FL 6 FL 7 562.5 m FL 8 500 m x 6 nos FL 9 to 14 Concrete CTE coating Monel coating Paint 562.5 m 112 m 14 m FL 15 FL 16 FL 17
  10. 10. SUBSEA PIPELINE DESIGN ACTIVITIES Pipeline Sizing Pipeline Material Selection Pipeline Mechanical Design Pipeline Stability Analysis Pipeline Span Analysis Pipeline Crossing Design Pipeline Cathodic Protection System Design
  11. 11. PIPELINE SIZING In general it means fixing up the pipeline nominal diameter (6Ɛ,10Ɛ etc.,) which deals with the important aspects like...   MAXIMUM FLOW RATE CONDITION   CHECK FOR THE FLOW CONDITION (pressure drop flow velocity)   CHECK FOR SECONDARY CRITERIA like Ʀ. # Flow regime (mix of hydro carbon, single/multi phase flow) # Temperature profile # Erosion velocity
  12. 12. D t
  13. 13. PIPELINE MATERIAL SELECTION The governing parameters for the particular type of material to be used are   Temperature   Pressure   Surrounding Environment. Environment.   Corrosive elements (CO2 and H2 S) Carbon steel (Carbon - Manganese Steel) C.S.Nace, C.R.A. Steel) p API - 5L of Grade Ranges From X - 42 to X - 80 p X-80 - Toughness and Weldability are limitations p API - 5L X- 52 ,60 65 Grades are commonly used. used.
  14. 14. PIPELINE MECHANICAL DESIGN The mechanical design of the pipeline is carried to with stand factors like Internal pressure External Pressure Do Hydrostatic Collapse Di Buckle initiation Buckle Propagation Po Po Po Pi W W ho ho
  15. 15. PIPELINE SPAN ANALYSIS Causes of the Pipeline Spans are Uneven Seabed on Selected route Pipeline Crossing seabed rock outcrop Sand Waves Scour All these result in spanning and cause Excessive yielding (Results in High Bending Moments) Buckle Initiation and there by Propagation Longitudinal loads Unsupported length
  16. 16. PIPELINE STABILITY Pipeline once installed at the sea bed should be sufficiently stable to avoid any overstressing, deterioration of coating etc., due to wave and current generated movements PIPELINE STABILITY Vertical stability Lateral stability
  17. 17. Vertical stability Sinking in to the sea bed during maximum fluid density condition. Floating of Buried Pipeline during Empty condition Soil Liquefaction. The Pipe sinkage is determined as the depth at which the applied pipe pressure equals the soil bearing resistance. Soil deformation(pipe sinkage)H,is given by: sinkage)H H = D/2-[(D/2)2 ± (B/2)2]1/2 D/2- Where, D = Overall pipe outside diameter including pipe coatings B = Projected contact area between pipe and soil =P/qu Where, qu = CNC +1/2BK NK +1/2BK qu = Ultimate bearing capacity of soil P = Pipe submerged weight including pipe coatings and in water filled condition per unit length.
  18. 18. Lateral stability It is the capacity to resist the lateral forces due to Environmental loads. Forces to be considered for Lateral stability analysis Submerged weight WS Lateral resistance R Friction Q Drag force FD Lift force FL
  19. 19. The stability criterion is expressed as (Ws - FL) Q u (FD + FI) S Where, S Ws FL FD FI Q = = = = = = safety factor (1.1) submerged weight of pipeline/unit length, for nominal wall thickness (t), N/m hydrodynamic lift force, N/m hydrodynamic drag force, N/m hydrodynamic inertia force, N/m lateral coefficient of friction between pipe and seabed.
  20. 20. Methods of Pipeline stabilization Increase Pipeline wall thickness Provide Concrete Weight Coating Lay the Pipeline in Open trench Trench and bury the Pipeline Provide Concrete Mattress over Pipeline Stabilize Pipeline by Rock dumping
  21. 21. Increase in Pipewall thickness Providing Concrete coating
  22. 22. Sea bed Tren h all Natural fill Buried pipe- Natural Fill Jetted in pipe Tremie concrete rmor rock Back fill Bedding Buried pipe- Armor Cover Bedding Buried pipe- Concrete Cover Stabilization Methods for buried Submarine pipeline
  23. 23. Trenching Concrete Mattress
  24. 24. Rock dumping
  25. 25. PIPELINE CROSSING ANALYSIS Crossings are designed to Give a Physical separation Between The Proposed Line Existing Line. To Avoid Interfacing Of Cathodic Protection Between The Two Lines A min of 300mm gap is Provided b/w the lines as per the DNVDNVCode.
  26. 26. Crossing analysis methodology » Pipeline Crossing Span Calculation. Pipeline Dynamic Span Calculation » Number of Supports to be Provided. » Pipeline Crossing Flexibility analysis » Pipeline Crossing Support design against, » Bearing capacity Over turning Sliding Settlement
  27. 27. PIPELINE CATHODIC PROTECTION SYSTEM DESIGN The Subsea pipelines are provided with sacrificial anodes made of Aluminum or Zinc to protect against marine corrosion Important parameters for Anode Design * Surface area of the Pipeline * Fluid and Anode temperature * Break down * Design service life of Anodes
  28. 28. MAJOR DESIGN CODES AND STANDARDS DNV 1981 DNV 2000 - Rules for submarine pipeline system - Submarine pipeline system API 5L - Specification for line pipe BS 8010 - Code of practice for pipeline NACE RP 0169 - Recommended practice,control of external corrosion on underground or submerged metallic piping. OISD 141 - Design and construction requirements for cross country hydrocarbon pipeline. ASME B 31.8 system. -Gas transmission and distribution piping ASME B 31.4 - Pipeline transportation systems for liquid hydrocarbon and other liquids