Jennifer Pallanich Hull
Gulf of Mexico Editor
The satellite services platform (SSP) combines many typical characteristics of production solutions into an inexpensive, easily installable unit for deepwater. The OPE-designed unit, suited for any water depth, will really shine in a marginal field, said Nicolaas J. Vandenworm, vice president for business development.
OPE, which developed the patented concept, sees the floating buoy as an alternative to FPSOs, Spars, and TLPs in areas where the fields are distant from the pipeline grid.
OPE noted that several independents are combining Spars and mini-TLPs with subsea tiebacks, and the company believes that the SSP will provide solutions for control buoys and reusable floating structures, giving independents even more field development leverage. The company expects that within the next 10 years, almost all production facilities in deepwater and ultra-deepwater will likely be floaters, with many tied back to subsea wells.
The mid-size SSP unit can act as a gathering platform for up to six subsea wells, and it would provide first-stage separation for satellite fields.
The SSP as an FPSO. The purpose-built vessel is designed to support different or modular deck equipment configurations.
A 1:85 scale model of the SSP wet tree design was tank tested in Delft University of Technology Model Basin in Delft, Holland, for several locations, including the Gulf of Mexico and off West Africa. The unit, fine-tuned over five years, also was tested for 100-year storm conditions. Det Norske Veritas has approved the design in concept.
The hull size and deckload can increase in this low-cost design.
"It's a very scalable unit," Vandenworm said of the design.
He attributes materials and the construction of frames as the factors that keep construction costs down with the SSP. The SSP itself has design features akin to a ship, in that it is more plated than rolled plate, he said.
Vandenworm said the hull form is a wave-riding design, although the heave and roll are well within the industry's accepted motion envelope.
In addition, the hull form length itself can be scaled for multiple field scenarios, giving it an advantage over the current systems. The hull supports techniques for developing small fields with relatively high gas content, capable of supporting early production in order to maximize profitable recovery, OPE said.
OPE sees the unit as working as a control buoy and compression station in ultra-deep-water for compressed natural gas (CNG).
"That would be useful for CNG," Vandenworm said.
Vandenworm expects the unit to be useful also for direct-connect for multi-tanker offloading.
The scalable feature would also come in handy for compression of LNG off West Africa. He said the unit can speed up the time to first oil or gas as well.
Deploying the platform
The entire unit is fabricated at the quay, in contrast with a Spar, which is fabricated in pieces and installed in a horizontal up-ending fashion on the field. The SSP can be towed out from the quay in a fully functional mode in conventional tow-out methods, eliminating the need for offshore vessels to lift equipment. In the ballasting mode, no additional stability tanks are required, and there are no extra survival draft issues, OPE said.
The unit, designed for manned or unmanned conditions, includes a center column assembly, which can be raised to allow access to a dock in shallow water and can be lowered for stability offshore (Offshore, August 1999).
Once the mooring is attached, the SSP can remain in the field without vessel support. OPE believes synthetic mooring is suitable for the units, as long as they are omitted from the first few hundred feet below the water line to prevent sea life abrasion and the first few hundred feet above seabed to prevent soil abrasion.
In the unit design, the deck structure is incorporated into the main hull, a factor OPE asserts is attractive in its size versus total deck payload.
OPE designed the unit to be:
- Capable of installation near deepwater subsea wells
- Easy to fabricate in most areas of the world
- Able to use conventional and synthetic mooring systems
- Highly mobile with re-deployment capabilities
- Able to work in potentially unlimited water depths
- Economic and flexible in its field development capabilities.
OPE is also designing a variation on the SSP with a dry tree solution that will have extremely low heave and low rolls but high payload, Vanden- worm said.