Repairs completed to the Maari oil field’s floating production vessel Raroa and its mooring assembly last year achieved a number of industry firsts.
The USD $70 million project involved a workforce of more than 500 and saw 68,000 man-hours completed with no lost-time accidents.
The ship’s 45-tonne replacement swivel was freighted in the world’s second-largest cargo aircraft and installed at Port Nelson - the first time such a highly technical change-out was completed at a local port.
Detailed numerical models had to be developed of the mooring and riser systems - the sub-sea architecture - to plan the disconnection and reconnection of the Raroa and the mooring repairs themselves.
The short-term repair made to the mooring system was also an industry first, being completed within days of the first cable failure and while the Raroa was still moored. Innovative sub-sea pulling equipment also had to be developed and built in Taranaki to complete the longer-term repairs in the tight timeframes available.
OMV says a high level of commitment, belief, flexibility and innovation was required across multiple organisations to turn a major risk to the Maari asset into an opportunity.
A seal failure was identified in the Raroa’s water injection swivel in November 2011 and planning started for an on-station replacement in 2016.
Due diligence conducted prior to the venture’s purchase of the vessel in March 2013 then identified anomalies in four of the eight wire legs of the mooring system.
The venture installed an emergency anchor to improve the resilience of the mooring lines pending longer-term repairs. But an unexpected and complete failure of a swivel bearing in August 2013 brought forward the timetable for both streams of work.
Earlier planning and options assessment meant the project team was able to quickly adapt their plans, and switch to a disconnection of the FPSO from the sub-sea architecture and have the swivel installed in port. At the same time, the mooring lines would be repaired on-station, while other upgrades and plant certification would be carried out on the Raroa, bringing forward work that would otherwise have been carried out in later years.
OMV says the ‘fast-tracked’ mooring repairs, the decision to order a replacement swivel a year prior to failure and the flawless swivel installation - completed under budget and without accidents - meant full production was restored after only five months.
Had the field’s sub-sea architecture been damaged at any time, production could have been halted for at least 16 months, it says.
The Energy Project of the Year category is sponsored by ITL