Alvheim FPSO and Subsea Infrastructure Decommissioning Study for Marathon Norway

RESL completes 6-month decommissioning study for Alvheim FPSO and complex subsea infrastructure for Marathon Oil Norway AS. 

The work scope covered AACE Class 5 cost estimate for FAS 143 compliance for a complex offshore subsea installation tied back to the Alvheim FPSO.  The scope required a detailed review of all relevant data and the development of outline methodologies for cleaning and disconnection the FPSO, removal of the associated mooring system, the decommissioning of multiple subsea facilities, export and in-field pipelines, flexible & rigid risers, mid water arches umbilicals etc. Facilities included in the study:

  • FPSO: complete with Turret / Swivel / Mooring, STP buoy and associated moorings
  • Risers: multiple production, gas lift and water disposal dynamic flexible risers
  • Subsea Facilities: 5 subsea centres, 29 production manifolds, PLEM &riser bases
  • Review of Alvheim & Volund Field Data
  • 33 pipelines
  • 18 wells- Decommissioning of subsea structures included, well P&A excluded 

In order to address the scope of work as set forth in the scope of work, RESL created specific report sub-sections to address the following topics:

  • Review of International & Norwegian Law & Regulation
  • Review of Alvheim & Volund Field Data
  • Cost Estimating (CE) Methodology
  • Method Statement& CE- Cleaning systems & pipelines
  • Method Statement& CE – Disconnection of FPSO from TMS
  • Method Statement& CE – Disconnection of risers & umbilicals fro STP buoy
  • Method Statement& CE – Disconnection of mid water arch system
  • Method Statement& CE – Removal of TMS/STP system
  • Method Statement& CE – Removal of subsea equipment
  • Method Statement& CE – Decommissioning of pipelines & umbilicals
  • Summary of Cost Estimates


Please contact us if you would like more information.