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Browse Concept Pipelay Analysis

Upon discovery of the offshore Pluto Gas Field in 2005, operator Woodside Energy Ltd engaged Atteris to ass

Browse Trunkline Installation Analysis

Benefits
Atteris’ assessment of installation feasibility in the early stages of the project identified a number of potential impacts on the pipeline design which might affect installation requirements. Understanding these impacts and constraints on the trunkline design enabled an optimised wall thickness design and reduced CAPEX.
Background
Woodside’s Browse trunkline, if installed, will be the largest diameter pipeline installed in water depths up to 500m. As the pipeline is optimised for the in-place condition, the wall thickness is minimised. The effects of collapse pressure on the reduced wall thickness, combined with bending in the sagbend during installation required investigation. It is important to assess the installation feasibility in the early stages of project definition to identify any impacts the pipeline design might have on the installation requirements. Pipeline installation has a significant impact on CAPEX as vessel production rates, pipelay tensions and the contractor’s risk profiles are altered.
Work Performed by Atteris

As part of the concept definition phase of work, Atteris conducted pipeline installation analyses using Orcaflex to identify potential installation issues. A number of models with varied water depths and pipe properties were analysed for the reference case mechanical design to assess the static utilisations for representative locations along the length of the trunkline. Given the criticality of the lower sagbend, dynamic analysis was also performed.
Outcomes from the investigation included the below:

  • Installation feasibility assessed.
  • Minimum acceptable wall thickness determined.
  • Pipelay tension requirements for updated design.
  • Stinger radius advice including sensitivity.
  • Guidance provided on actual safety margin in sagbend.
  • Assessment of 42” to 36” transition installation.
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