Subsea LNG pipelines

Where they are used

The main application for subsea LNG pipelines is for tanker loading/unloading where the liquefaction plant is on a coast with a gently sloping seabed.  This can mean that the tanker berth may need to be 15 km offshore in order to have sufficient water depth for the draft of the LNG carrier.  The conventional solution is to construct a long jetty and/or to dredge and maintain a channel for the carriers to come nearer the shore.  For distances over 5 km the subsea pipeline to a jetty head offers significant cost savings and avoids disruption to navigation.

Jee technology and experience
Jee has been working in this field since 1995 and has accumulated experience and developed technological solutions in the following areas:

• Flow:  diameter and pump sizing, design pressures, transient analysis
• Thermal:  power and insulation requirements, optimisation
• Design:  avoidance of bellows and expansion loops, in-house limit state pipeline technology

• Mechanical:  wall sizing, bulkheads and pre-tensioning, FE analysis
• Stability:  on-bottom stability, thermal buckling
• Materials:  insulation, pipe, carrier, weld selection
• Construction:  cost-efficient fabrication and construction techniques
• Operations:  risk assessment, control,  start up, integrity monitoring, repair
• SRA:  structural reliability assessment.
• Commercial:  Cost and time estimates, track record and case studies
• Tests:  materials, component and system tests

What Jee offers

• Feasibility:  evaluation of the subsea LNG pipelines to the point of showing that they meet the client’s business goals:  will they work, will they meet timescales and budgets, what are the main drivers and risks.

• Pre-FEED:  design and costing of the various subsea LNG pipeline options to select a preferred one:  cross section sizing, materials selection, stability, construction, tie-ins, costs and time estimates, definition of scope of work for Feed.
• FEED:  Working up the detail of the design sufficient for EPC tendering and to allow project sanction:  design optimisation, materials/component/system tests, interfaces with process/survey/vessel, project management and tendering, etc
• Technical support:  Support to clients on technical and managerial issues in the field of subsea LNG pipelines at all phases of the design life:  this is often focussed in front end loading studies in the research and design phase, and then operations support and integrity management during the operations phase.