A few months ago E&P featured the pioneering FPSO vessel that helped change the way oil companies approach small- and medium-sized field developments—the Petrojarl I [See the August issue’s Vessel Spotlight].

But the next few months will witness another pioneering FPSO set a new industry standard that few would have believed possible 30 years ago when the Petrojarl I—then known simply as the “Production Test Ship”—began operations offshore Norway in 100 m (328 ft) of water.

The new kid on the block is Shell’s Turritella FPSO, which, despite being “only” a converted Generation 2 design, will be remarkable in that it will become the world’s deepest offshore production facility of any kind when it starts flowing oil for operator Shell on its Lower Tertiary Stones Field in Walker Ridge Block 551. It will sit 2,896 m (9,500 ft) above the seabed.

The leased floater, converted and retrofitted from a Suezmax tanker into an FPSO vessel at the Keppel Shipyard in Singapore by SBM Offshore, is to work initially for Shell for 10 years, with extension options for up to 20 years. The vessel left Keppel’s yard in November 2015 to transit to the Gulf of Mexico (GoM), with production startup planned during first-half 2016.

The Turritella has a disconnectable internal buoyant turret and processing capacity of 60,000 bbl/d of oil and 424.7 Mcm/d (15 MMcf/d) of gas treatment and export. As demonstrated by other weathervaning FPSOs, the ability to be able to quickly disconnect and move location in case of potential hurricane conditions was a major factor in the concept’s selection by Shell.

Other innovations will see the vessel’s turret and disconnectable buoy configured with flexible steel lazy-wave risers, the first ever application of this on an FPSO vessel. An arch bend will absorb the motion of the FPSO unit and boost riser performance at extreme depths. The mooring system, using a lightweight combination of polyester rope and chain, also will incorporate the ability to adjust line tension during operations by use of an inline mooring connector.

The Stones Field has recoverable reserves currently estimated at more than 250 MMboe, with more than 2 Bboe of oil in place. An initial two subsea wells will be tied back to the Turritella, with up to a further six to follow in later phases and also employing multiphase pumping.

With the venerable Petrojarl I recently revamped and set to continue producing for at least another 15 years, the Turritella has a tough reputation to live up to.

Vessel Facts:

Sector: Floating production

Owner: SBM Offshore/Mitsubishi/Nippon Yusen Kabushiki

Converted: Keppel Shipyard, Singapore (2013 to 2015)

Deadweight: 159,113 tons

Length/Breadth: 274.5 m by 48 m (900.5 ft by 157 ft)

Transit Speed: 11 knots

Mooring Type: Disconnectable internal turret/buoy

Riser Type: Steel lazy wave

Total Topsides Weight: 7,000 tons

Production Capacity: 60,000 bbl/d oil, 0.42 MMcm/d (1.4 Bcf/d) gas

Storage Capacity: 800,000 bbl

Water depth: 2,896 m (9,501 ft)

First Location: Stones Field, GoM

Offshore