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system. The turret will comply with a reduced mooring offset envelope for more onerous speci- fed weather conditions, with the existing riser arrangement and

Production new overall subsea production system layout. This includes design requirements for up to 28 riser slots, against 24 for the

Schiehallion FPSO, and for the anchor legs to be grouped into four clusters of fve mooring lines each, to suit the existing subsea infrastructure.

The turret system’s arrangement will allow anchor lines and risers installation to be diverless – an enhanced safety feature, compared with previous designs. The turret structure has been designed for a minimum 25-year service life.

Swivel seals change-out will be possible in-situ, without interrup- tion to production, due to SBM

Scafold access for extensive steel

Offshore’s technology. The bogie- renewals at height.

bearing weathervaning system can signifcant wave height of about also be repaired, and main compo- 13m. As a result of experiences on nents, such as wheels, replaced in-

Schiehallion over the last 15 years, situ, were this ever to be necessary. the design maturity of the moor- This system operated for 15 years ing line components, such as steel on the Schiehallion turret and the wire rope and chain, is now quite bogies performed their function advanced for the water depth. without incident.

Future Atlantic Frontier develop- In addition to handling the full ments will be further west in even crude production, water injection deeper waters, which will present and water injection, gas lift, export new challenges to the industry. The and import fows, the swivel sys- combination of deepwater (deeper tem will provide for all ancillary than 1000m) and the extremely services required on the turret harsh environment will represent a fxed part, including electric power frst-ever for the mooring industry, and control, chemical injection, requiring tailored modifcations. water deluge, and air, for turret

For example, in some countries, equipment room pressurization.

the wire rope component will have “This 10,000-tonne Quad 204 to be replaced by polyester rope. turret is the most critical com-

Although polyester ropes have ponent of the FPSO,” stated Jeff been used for more than 10 years Mace, BP’s turret delivery manager. in the deep waters of Brazil, the The next important milestone, after

The turret mooring system. Quad 204 sea conditions are signifcantly less delivery of the manifold and gantry stringent there, compared with the structures in Korea, will be the area west of Shetland. recovery of the old mooring system and mechanical completion of the integrated

BP awarded the contract for the dis- installation of the new FPSO anchoring turret, planned for Q3 2014. BP will man- connection of the Schiehallion and the system, including the 20 new piles and age this process with the assistance of installation of the new FPSO to Technip chain and spiral strand wire mooring SBM Offshore.

UK. Technip UK in turn awarded SBM system. Phase III includes Schiehallion’s Safety standards based on systematic

Offshore an additional subcontract in tow to feld and the mooring of the in-depth analysis and improved reliabil-

November 2012, which includes phases new FPSO, to be carried out in 2015. ity for operations are the key enhance-

I-III. Phase I consists of the disconnection Schiehallion was decommissioned earlier ments of the Quad 204 turret mooring and removal of the existing Schiehallion this year. system over the original Schiehallion. and mooring lines and its subsequent The new turret design will provide Some key improvements are the riser tow to Rotterdam, now currently on- suffcient space for process sub-systems top-mounted emergency shutdown going. Phase II, occurring in 2014, is the and utility support for the subsea control valves and wind shielding, which could

December 2013 | OE oedigital.com 42 040_OE1213_ProdOps_StrucIntegrity.indd 42 11/22/13 6:31 PM