With many years experience in the conversion of oil tankers to FPSO or FSO units, SBM Offshore re-applied core skills developed over many decades to refurbish and convert a double hulled tanker, the Okha, to serve as an FPSO offshore from Australia.
Prior to the conversion, Okha was operated as an FSO close to Sakhalin Island, Russia, so we understood the vessel’s capabilities well enough to know that the main issue needing to be addressed to convert it to an FPSO unit was the under deck welds. Induced fatigue analysis confirmed that these would not be strong enough to support FPSO topside modules.
Designing a refurbishment program
The project provided a great opportunity for our topsides structural group, vessel naval group and Singapore team to pool their expertise in search of the most appropriate conversion solutions, taking into account the client’s stringent requirements and the existing regulatory framework.
On completion, Okha would replace the FPSO Cossack Pioneer, which was installed in 1995. Once in place it would connect to the Riser Turret Mooring (RTM) column, subsea risers and anchoring system already in place for the Cossack Pioneer – becoming our very first complete FPSO project and our sixth RTM design for use in Australia.
Meeting new challenges
As the project progressed it became clear that the biggest challenge faced was to achieve a near perfect alignment between the fluid connector flanges on the original RTM Colum and those on the Okha’s newly designed turret. Only following a series of detailed discussions, risk assessments and technical surveys was this alignment achieved – with no costly design modifications required.
Now in place, the bow-mounted RTM on the FPSO Okha allows it to weathervane in response to normal conditions and disconnect to sail to calmer waters during severe cyclones. The new FPSO constitutes a high quality technical solution – achieved on time and on specification with an outstanding safety record of more than 10,000,000 manhours without a single lost time incident.