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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