Concept Engineering Studies – Laverda Development Concept Select

Background

Hydrocarbons from the Woodside Energy Laverda (oil) and Ragnar (gas) Fields were planned to be tied back to the Laverda FPSO via subsea flowlines and flexible risers. The FPSO, located in 830 m of water offloads to oil tankers via a floating hose. Sales gas will be exported to the mainland via a 113 km subsea trunkline and tied into an existing gas sales pipeline via a 6 km or 15 km onshore pipeline to Tubridgi or Macedon gas plants. An option for fuel and gas cap recharge for the Ngujima‑Yin FPSO and Vincent reservoir via an interfield pipeline from a subsea branch in the Laverda Gas Trunkline was also considered.

Work Performed by Atteris

Atteris were nominated the Pipeline and Flowline Study and executed the scope using a team comprising of members from all of the consortium partners. Comprising of the Ragnar flowline in 1150 m water to the Laverda FPSO, the Laverda Gas Trunkline to shore and interfiled line, shore crossing, and onshore pipeline options. Interfacing with flow assurance and subsea teams, the following activities were performed:

  • Pipeline routing development and assessment
  • On-bottom roughness assessment
  • Preliminary mechanical design
  • Support to environmental approvals process
  • Development of geophysical and geotechnical survey scopes
  • Basis of design (Mechanical, Metocean, and Geotechnical)
  • Shore crossing method selection
  • Tie-in option study
  • Deterministic cost estimate
  • Identification of project risks

All work was undertaken in collaboration with the Woodside team and adhered to the project’s inherent safety principles.

Benefit

Using limited data, the project team was able to quickly develop and select a robust concept for further economic analysis by Woodside. Utilising Atteris’ local knowledge and expertise an aggressive baseline cost estimate which included no secondary stabilisation allowance for the large trunkline was assured. The application of Woodside’s Justify-In policy, employed in all of Atteris’ engineering, ensured for a fully optimised design which was relevant to the data available to hand.