SBM Offshore has won a major order today from Shell to supply and lease a new Floating Production Storage and Offloading (FPSO) for the Stones development project located in the Gulf of Mexico. Once installed, the Stones FPSO will be the world’s deepest floating production facility and will have an asset value of around USD $1 billion.
As a converted Suezmax tanker, this new FPSO would join the Petrobras-contracted BW Pioneer in the Walker Ridge area approximately 320km (200 miles) offshore in 2,896m (9500ft) of water.
The initial period of the charter contract is for 10 years with future extension options up to a total of 20 years.
The FPSO will have a storage capacity of 800,000 bbls of oil and be outfitted with a turret with a disconnectable buoy (Buoyant Turret Mooring or BTM) allowing it to weathervane in normal conditions and disconnect from the FPSO upon the approach of a hurricane. SBM Offshore notes that the FPSO is a generation 2 design with a processing facility capacity of 60,000 barrels of oil per day (bopd) and 15 mmscfd of gas treatment and export. No water injection facilities are specified.
Disconnectable Turret Advantages
According to a paper by Jingyun Cheng, and Peimin Cao from SBM Offshore, disconnectable FPSOs have significant advantages over permanently moored FPSOs in that, “the mooring system does not have to be designed to accommodate the economically penalizing severe loadings associated with hurricane and typhoon conditions. It allows rapid vessel removal for maintenance or upgrade. It also enables phased development due to production uncertainty, which reduces reservoir risk.”
The BTM will be configured with Steel Lazy-Wave Risers (SLWR) which will be a first application for a disconnectable FPSO. Riser specialists, 2H Offshore describe these Lazy-Wave Risers:
“A lazy-wave catenary riser (LWR) is a special SCR [steel catenary riser] with a segment of its length equipped with external buoyancy modules, where its upward buoyancy force in water is greater than its downward gravity force and thus an equivalent negative “gravity” force. A typical LWR consists of three segments, each segment a catenary, namely the hang-off catenary (hanging and jumper sections), the buoyancy catenary (lift and drag sections) and the touchdown catenary,” as illustrated below.
The mooring system will also incorporate the ability to adjust line tension during operations by use of an In-Line Mooring Connector (ILMC).
In March 2012, Shell and SBM Offshore signed an Enterprise Framework Agreement (EFA) for the supply of medium and small FPSOs on a lease and operate basis. The Stones FPSO is the first Shell project to award contracts utilizing the EFA.
SBM Offshore and Shell have been engaged in front-end development work for the Stones FPSO solution for the past two years.