Poetry in motion

Jennifer Pallanich
Thursday, March 4, 2010

Banking on customer desire for a round floater that offers drilling, storage, and/or production along with dry tree capabilities, SSP Offshore has made its SSP320+ Plus design ready for the market. Jennifer Pallanich looks at the latest refinements to this concept and the results of its recent Brazilian model test program.

The need to accommodate dry trees, steel catenary risers, and exploration or drilling capability provided the key considerations as SSP Offshore honed its plans for the Satellite Services Platform (SSP) 320 base case plus (SSP320+ Plus) design, an upgrade to the existing SSP320 base case design (OE January 2009).

The SSP concept has been around since the mid-1990s but ownership of OPE's proprietary platform technology transferred to a new corporate entity, SSP Offshore, in early 2009 following the break up of OPE Holdings and the sale of its separate offshore engineering division to Foster Wheeler. The move served to intensify concept development efforts, reports Nico Vandenworm, SSP Offshore senior vice president for worldwide commercial and corporate strategy.

The round floater design, he says, presents a more simplistic offloading system, equivalent to offloading a large CALM buoy. ‘We have a system that can accommodate almost everything a spar does, but we have storage.' It also has the motions of a spar, he adds.

The SSP Offshore team returned from Rio de Janeiro late last year confident that they had the model test results to back up the company's statements about the design's motions. The tank tests – featuring a 1:60 scale model of the SSP320+ Plus connected to six steel catenary risers (SCRs) – were conducted in Rio's Lab Oceana basin from September through December 2009. ‘They have a great understanding of round floaters already,' even in a wave spectra of 18.5s that SSP tested, Vandenworm explains.

A secondary draw to the facility was his company's desire to enter the Brazilian market. ‘Brazil is a very serious focus for us, particularly because of the pre-salt challenges where we feel we are a differentiator, where we can provide technical solutions for them,' Vandenworm notes. He also sees West Africa as a strong market for the design.

According to Vandenworm, the testing confirmed SSP Offshore's numeric analysis of 13 different environmental global spectra for one-year, ten-year and 100-year storms, as well as a 1000-year post-Katrina storm for the Gulf of Mexico. With the test results indicating a unit in the Gulf would not have to disconnect during extreme weather conditions, Vandenworm says: ‘We could leave, but we don't have to leave.'

The SSP motions have similar motion characteristics in all directions, according to the company, and eliminate yaw roll and pitch excitation. A natural heave period of 23 seconds and a natural pitch of 33 seconds were among the test outcomes Vandenworm says his company found most pleasing. Another test simulated offloading to a spot market tanker/shuttle tanker during a West African squall. Describing the test results as very encouraging, he points out they are in line both with the numerical analysis and the SSP contribution to the current Offloading Study JIP.

Companies involved in the Lab Oceano basin testing include SSP Offshore, Marin, and Oceanica Offshore, a Brazilian consultancy company experienced in naval and offshore requirements.

Base and plus
A ‘hybrid floating real estate platform' is how SSP Offshore describes its SSP320 product line design.

One of the first steps the company took was to add mass to the SSP320 base design, which provided the desired motions and meant the earlier design could hold 1.2 million barrels while the SSP320+ Plus design could hold 1.6 million barrels. The optimal ways to achieve 20+ second heave period motions, Vandenworm says, are to add heave plates or extend the bottom. SSP Offshore opted for the latter course, adopting an inclined hull shape to eliminate vortexinduced motions and waste slamming while also contributing to improved stability.

‘We have a permanent draft,' Vandenworm explains. ‘We compensate. Whatever [volume] comes in comes out,' he says. ‘We wanted a motion that is consistent. We wanted to stay at one draft.'

The SSP320 design can accommodate only wet trees, while the enhanced SSP320+ Plus can be set up for wet or dry trees and can handle any combination of drilling, production and storage, Vandenworm says. The SSP320 cannot use SCRs in pre-salt or harsh environments, but the SSP320+ Plus can. ‘Yes, we think so. Well, we know so,' he adds.

The tanker of choice for the round floater, the VLCC, can queue up at an SSP Offshore-patented single point of offloading from either design. The offloading design does not require a CALM buoy as a secondary offloading system or turret mooring. Instead, the company says, the units have the benefits of CALM buoys ‘built into' them, which allows offloading via tankers of opportunity.

The spread-moored system for the round floater is not limited by water depth, and the unit can be dynamically positioned for drilling if desired, Vandenworm notes. Scalable up or down, it is compliant with ABS and DNV standards.

‘The principle of how to fabricate the floater is the same' for both designs, Vandenworm says. For instance, fabrication of the unit does not require a graving dock. ‘That will be a significant differentiator compared to a traditional ship-shape floater' with comparable capacity, he adds.

Quayside integration in 9-10m of water is a key feature of the design's ‘buildability,' as is the fact that it is flat plated and can be built in sections. In Vandenworm's words, it ‘can be done in segmented pizza slices' weighing up to 150 tons. ‘The methodology is modular. It's flat plated. The structure is laborfriendly from a welding and pipefitting point of view,' he says.

Additionally, the fabrication of the units can be done largely with local content. ‘We have a product that can provide local content. That makes it a strong enabler for any operator,' he adds.

SSP Offshore also did some legwork on fabrication of the design last year shortly before going to the test basin. The company worked with a Malaysian representative to obtain quotes to fabricate the SSP320+ design. Based on that information, Vandenworm says, the company is confident it is offering a cost-effective price compared to shipshaped FPSOs. With comparable storage, he says, the SSP 320+ Plus design is about 35% less expensive based on steel requirements. The SSP320 design would require 29,000-33,000 tons of steel, while the SSP320+ Plus would require some 47,000-52,000 tons. A newbuild FPSO would exceed SSP320+ Plus in terms of steel weight.

Vandenworm sees the round unit as preferable for several reasons: ‘FPSOs don't have fantastic motions,' he says, noting they also cannot accommodate SCRs or dry trees.

SSP Offshore considers both of its designs to be part of the SSP320 product line. As it stands, Vandenworm says, both designs are ready for tendering. The company is focused on project opportunities and bidding. OE

Categories: FPSO South America System Design

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