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

1
TECHNICAL CONDITIONS OF CONSTRUCTION AND
OPERATION OF THE GAS PIPELINE ON THE BOTTOM OF
THE BALTIC SEAINVESTMENT DESIGN ASSUMPTIONS

• Prof. Boleslaw Mazurkiewicz Technical
  University in Gdansk

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
III Measurement and test stage and data
collection ? geophysical investigations ?
bathymetrical investigations ? geotechnical
investigations ? oceanographical investigations

• IV Design work stage
• an initial design for 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
Type of interaction Cause
Weights Gravity forces
Lift Hydrostatic forces Liquefaction
Resistance forces Velocity of fixed currents Oscillatory velocities in wave motion tearing off of whirls
Lift and tear off forces (crosswise) Velocity of steady currents Oscillatory velocities in wave motion tearing off of vortexes
Forces of inertia Oscillatory of molecule acceleration in wave motion
Tensile forces Pipe laying vessel tension trension cable pipe laying vessel motions internal medium pressure thermal shrinkage
Compressive forces Gravity forces Pushing out during pipe laying pipe laying-vessel motions thermal expansion
Twisting Pipe laying vessel motions Connection of hanging loops
Outer pressure Hydrostatic forces Ground
Internal pressure Medium pressing Stroke of pressed medium
6
Dangers threating the sea pipelines
Danger Prevailing type of ground, region Geometrical and physical characteristics
Lanslides of the bottomsrunoffs of the bottoms Soft clays of the delta regions (water depthe less than 60 m) Width, length, strength and thickness shear strength and other geotechnical data expected translocations of considered region or zone
Turbidity currents Soft clays Phenomenon range, equivalent fluid velocities and densities, ground strength and other geotechnical data
Clotted bottoms Mouth deposits Changes of width and level in zone shear strength and other geotechnical data of caking and surrounding deposits
Intrusions of crystallized salt Mouth deposits Width and expected uplift (elevation), ground shear strength and other geotechnical data
Slopes Regions with seismic danger Width and expected slope translocation, strength and other ground properties
Liquefaction Interaction of wave and sea bottom -loads resulting from the earthquake Sands , clays Sands, clays Width and thickness of the liquefied zone , strength and other ground properties
Local erosion Soft clays and sands Depth and width of the local erosion zone
Lack of pipeline support Sands receptive to erosion hollow properties Scope between supporting places, ground strength
Sand waves Debris currents strong bottom currents Wave height and range of threaten region
7
Laying of the undersea pipelines

• legend
• Plywaki floats
• Ukladanie rurociagów za pomoca.... 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 stingers type).

8
INTERACTION DURING LAYING

• LEGEND
• sily pionowe vertical forces
• barka barge
• sila ciagnienia tension force
• wysiegnik stinger
• sily poziome horizontal forces
• dno morza sea bottom
• profil pradów . crosswise current profile
• wezlów knots

9
(No Transcript)
10
(No Transcript)
11
Preventive activity in case of dangers
threatening undersea pipelines
Environmental danger Preventive actions Preventive actions Preventive actions Preventive actions Preventive actions
Environmental danger Pipeline burying Pipeline uplift Ballasting jacket Pipeline anchorage Heavier pipeline
Hydrodynamical forces Tearing off of wortexes Local erosion and lack of support Sand waves Creeps and runoffs of the bottom deposits Turbidity currents Pipeline floating Deposit caking crystallization of salt Slopes, earthquakes - - - - - - - - - - - - - - - - - - - - - - - - -
Ground liquefaction The pipeline should be designed in such way, so that its unit weight would be as much as possible approximate to the unit weight of the liquefied ground and the pipeline is to be burried below the liquefaction level or to anchor it. The pipeline should be designed in such way, so that its unit weight would be as much as possible approximate to the unit weight of the liquefied ground and the pipeline is to be burried below the liquefaction level or to anchor it. The pipeline should be designed in such way, so that its unit weight would be as much as possible approximate to the unit weight of the liquefied ground and the pipeline is to be burried below the liquefaction level or to anchor it. The pipeline should be designed in such way, so that its unit weight would be as much as possible approximate to the unit weight of the liquefied ground and the pipeline is to be burried below the liquefaction level or to anchor it. The pipeline should be designed in such way, so that its unit weight would be as much as possible approximate to the unit weight of the liquefied ground and the pipeline is to be burried below the liquefaction level or to anchor it.
12
Current requirements concerning large diameter
pipeline burying (gt 750 mm)
Pipeline laying zone Existing dangers / risks Current requirements Future probable immersion practice Remarks
Coastal zone water depth lt10 m Waves, currents, bottom erosion, mud landslides, dredging outlets ? 3 m Burying as deeply as possible
Ports and anchorage Waves, currents, drawing works, anchoring 3 m Burying as deeply as possible Burying may turn out to be insufficient. It should be considered change of the route or other protecting methods.
Coastal zone and small water depth zone. Distance from the coast ? 50 km or water depth ? 30 m Waves, currents, fishery, anchoring ? dredging works ? variable Burying required usually only due to stability respects.. Immersion level determined for each specific case. It should be examined navigation and emergency anchorage statistics.
13
Pipeline laying zone Existing dangers / risks Current requirements Future probable burying practice Remarks
Open sea, average water depth. 30 m lt water depth ? 100 m. Distance to the coast ? 50 km Waves, currents, fishery, 1m Sinking can be necessary due to stability respects Protection against fishery can be made by means of suitable concrete jacket
Deep waters, water depth gt 100 m Waves, fishery 1 m Sinking is not required Protection against fishery with suitable concrete jacket
Areas close to platform. Distance to platform lt 5 km Currents, fishery, anchorage of the ocean technical vessels 3 m Sink as deep as possible backfilling Burying may turn out to be insufficient. Other protecting methods should be considered.
14
Pipeline protection methods

1. Not protected pipeline rests on the bottom
2. Ballasted pipelines
3. Pipelines on stakes
4. Pipelines on supports (saddles)
5. Anchoraged pipeline
6. Rinsed out pipeline
7. Immersed pipeline natural backfilling
8. Immersed pipeline backfilling ( cover) of
   rock blocks
9. 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
Liquefacting units Conventional Hydraulical cultivation (towed cradles) Undersea equipment and vehicles Plowing after laying Plowing before laying
Sandy bottom - - - - effective - not effective
Clayey bottom - effective -not effective
Method interrelation on equipment on the sea surface - - dependent -independent
Impacts of the sea current - - - - small impact -big impact
Method development conducting, lowering lifting - - - - Not difficult difficult
Costs - - - - less expensive - expensive
Water depth - - - deep -shallow
Previous experience - - there are experiences -no experiences
Required development and tests - - - lack of development - development exists
Power consumption - - - minor demand - big demand
Productivity - large - small
Forces acting on the pipeline - - - small -large _
17
Damage risk of the undersea pipelines
Anchorage resulting from machine failure Anchorage resulting from collision of two vessels Running of the vessels at the bottom of the sea Total number of events
Annual frequency and period of repeated damage (including pipeline getting torn) 3.9 10-3 256 years gt 4.5 10-5 lt 22220 years 2.74 10-4 3650 years 4.22 10-3 237 years
Frequency is defined as the number of events for year and pipeline kilometer ( km) Note In case of laying of the pipeline laying with concrete cover , risk of the pipeline damage caused by fishing tool drawing is not taken into consideration. Frequency is defined as the number of events for year and pipeline kilometer ( km) Note In case of laying of the pipeline laying with concrete cover , risk of the pipeline damage caused by fishing tool drawing is not taken into consideration. Frequency is defined as the number of events for year and pipeline kilometer ( km) Note In case of laying of the pipeline laying with concrete cover , risk of the pipeline damage caused by fishing tool drawing is not taken into consideration. Frequency is defined as the number of events for year and pipeline kilometer ( km) Note In case of laying of the pipeline laying with concrete cover , risk of the pipeline damage caused by fishing tool drawing is not taken into consideration. Frequency is defined as the number of events for year and pipeline kilometer ( km) Note In case of laying of the pipeline laying with concrete cover , risk of the pipeline damage caused by fishing tool drawing is not taken into consideration.
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 dogs leg type pipe
  section
• connection by means of hyperbaric welding
• connection with use of a straight section
• deck
• platform base.