design of offshore pipelines_shore approach
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DESIGN OF OFFSHORE PIPELINESShore Approach Design
Shore Crossing
Typical Offshore Field Development
Why Are Shore Approaches Challenging?
• Environmental Conditions Most Severe• Often Complex Geology• Environmental Value Highest• Greatest Exposure to the Public• Survey, Construction and Inspection Access Difficult• In Most Cases No Reference Available• Common Failure Location
Shore Approach Design
• Site Data Collection• Pipeline Shore Approach Routing Selection• Landfall Site Selection• Construction Method Definition• Pipeline Mechanical Design (Installation & Operation)• Pipeline Hydrodynamic Stability Design (Inst. & Op.)• Shoreline Environment Protection Design
Site Data Collection• Topographic and Bathymetric Surveys• Geophysical and Geotechnical Surveys and Studies• Metocean Data Collection Surveys and Studies• Weather Data Collection Surveys and Studies• Seismic Data Collection Surveys and Studies• Environmental Surveys and Studies (Flora & Fauna)• Cultural and Heritage Surveys and Studies• Land and Water Use (Ports, Shipping, Tourism, Etc)
Site Visit
Site Visit
Acquisition of Seabed Data• Bathymetry data• Top 3-5m of Seabed• Composition (Soil/Rock)• Engineering Properties
Acquisition Method• Geophysical Surveys (Seismic) • Geotechnical Surveys
Lead Line
Multi Beam Echo Sounder (MBE)
LIDAR (Light Detection and Ranging)
Water Depth Contour Lines
Geophysical Survey Systems
• Side Scan Sonar• Shallow Seismic Reflection (Sub Bottom Profiler) • Seismic Refraction• Electric Resistivity
Side Scan Sonar
Side Scan Sonar
Seismic Refraction/Reflection
Geotechnical Techniques
• Cone Penetration Tests • Vibro Coring • Drop Core/Piston Core• Rotary Coring
Laboratory Testing
Nearshore Core Sampling
Nearshore Core Sampling
Jack-Up Barge
Scenic Coastline
Populated Area / Coastal Erosion
Coastal Erosion
Severe Wave Climate
Perfect Beach?
Turtle Tracks
High Strength Igneous Rock
EXISTING DUMPING GROUND
EXISTING SHIPPING CHANNELS
EXISTING PIPELINES
Pipeline Mechanical Design
• Onshore (AS 2885) and Offshore (OS F101) Standards
• Wall Thickness, Corrosion Protection, Abrasion Protection
• Mechanical Protection (Human Activity, Shipping Traffic, Fishing, Dredging)
Hydrodynamic Stability Design
• Shoaling / Breaking Waves
• Weight Coating Design (Balance btw Ease of Installation and Need for Stability)
• Design to Account for Scour and Liquefaction Phenomena
Hydrodynamic Stability Design
Shoreline Environment Protection
• Avoid Accelerated Erosion• Flora & Fauna Protection• Heritage Protection• Continuous Dialogue with Stakeholders
Dune Erosion
Shore Approach Construction
• Open-Cut and Cover
• Horizontal Directional Drilling
• Tunnelling
Open-Cut and Cover
• Pre-Lay Trenching
• Pipeline Installation
• Trench Backfill
Open-Cut and Cover
Open-Cut and Cover
Backhoe Dredge
Backhoe Dredge
Cutter Suction Dredge
Cutter LadderSpuds
Cutter Head
Cutter Suction Dredge
Trailer Suction Hopper Dredge
Trailer Suction Hopper Dredge
Drag Head (TSHD)
Onshore Excavation
Shore Pull
Tow-Out
Open-Cut and Cover
• Conventional Method
• All Ground Conditions
• Requires Friendly Seastate
• Relatively High Environmental and Social Impact
Horizontal Directional Drilling(HDD)
HDD
HDD Rig
HDD Spread
HDD
• High Risk (if not well designed, prepared and managed)
• Relatively Low Environmental and Social Impact
• Up to 2 - 2.5 km length in Favourable Site Conditions
Tunnelling
• Vertical Shaft or Launching Pit Construction
• Exit Point Preparation
• Tunnelling
• Pipeline Installation
Tunnelling
Tunnelling
Tunnel Launching Shaft
Tunnelling
• High Risk (if not well designed, prepared and managed)
• Relatively Low Environmental and Social Impact
• Up to several kms in Favourable Site Conditions, however, diameter increases with tunnel length
Tunnelling Risk