Ice management dominates Shtokman platform planning Spar, FPU in frame for first production phase

Map shows location of Shtokman in the central sector of the Russian Barents Sea.

The contracts were issued by the newly formed Shtokman Development Co. AG (SDAG), led by Gazprom subsidiary Sevmorneftegaz (51%), Total (25%), and StatoilHydro (24%). All FEED work should be completed by mid-2009, with a final investment decision expected a few months later.

Shtokman, discovered in 1988, contains an estimated 3.8 tcm (134 tcf) of gas and 37 MMtons of gas condensate. Under Phase 1, SDAG plans to produce 23.7 bcm/yr (837 bcf/yr) of gas, with pipeline deliveries starting early in 2013, and first LNG the following year.

Conceptual studies for the offshore production system actually began three months before the official contract award in late March, but this was not Doris’ first acquaintance with the project. In 2005, when Gazprom first invited foreign oil companies to submit development proposals, the Paris-based contractor worked on numerous concepts for floating structures for Total, in particular TLPs.

Gazprom gave Total the lead role in FEED awards “because of its strong capability in the management of large development projects,” says Doris’ Sales & Marketing Vice-President Michel Deguen. “They have seen Total’s expertise in quickly mobilizing resources for all aspects of a project, and they were also impressed by the company’s track record both in the deepwater area, and as a big gas producer.”

Doris accepted its invitation, although the company’s president, Loïc des Déserts, insisted on teaming up rapidly with a Russian partner. This led to the association with Rubin, an engineering group established in St Petersburg since 1905, best known as a designer of military submarines. In recent years, however, the company has diversified into other industrial sectors, providing technical assistance for the Prirazlomnoye and Sakhalin offshore projects.

“They have good engineering expertise, although they do not speak English or French,” says Deguen. “This created a problem initially, as all documents for this project must be prepared in English and Russian. But we have since appointed a permanent interpreter to work with us in Paris – their own interpreters are extremely good, and know exactly what they are talking about.”

Under the terms of the FEED award, the two parties are sharing the workload on a 50-50 basis. Rubin is focusing on the platform hull, Doris on the subsea engineering, while topsides design responsibilities will be shared. “Officially they are our subcontractors, but effectively we are partners,” explains Deguen. “Today the joint venture has around 40 people based in Paris – this number will eventually rise to 100, with a further 100 in St Petersburg.

“What we have learned is that for the Russians, this project is really a key part of their plan to develop their internal expertise. For the second phase of Shtokman, they will try to do it themselves.”

Platform concepts

Doris started its studies last September. Much of their early work was flow assurance analysis – how to transfer produced gas and condensate onshore, via a single-phase or multi-phase pipeline.

The two front-runner concepts for the platform are a spar – the preferred choice at the start of the project – and a turret-moored floating production unit (FPU). Either solution must be suitable for assembly in Russian shipyards, although Technip has a spar construction site nearby in Finland. Doris is working on topsides requirements and installation costs for both cases.

But according to des Déserts, the real issues are pack ice, which builds very quickly in this part of the Barents Sea, and huge roving icebergs weighing up to 10,000 tons (9,072 metric tons). “In emergency situations,” he says, “you would want to disconnect the platform quickly, but with ice forming quickly, this could prove difficult – more so, in my view, for a spar than an FPU.”

There are no harsh environment precedents to draw on, he adds, not even off eastern Canada. “No icebergs have been seen around the Hibernia platform since it was installed 10 years ago. As for the Terra Nova FPSO, that has only had to disconnect once – not because of ice, but for maintenance.

“Ice management in that region has proven to be much more efficient than foreseen. But pack ice around Shtokman is much thicker – up to 3 m (9.85 ft), compared to 1.5 m (4.9 ft) for Terra Nova, with 100% coverage. And if you are surrounded by ice, in a location 600 km (373 mi) offshore, how do you manage a quick escape in case of a fire? For this reason, icebreaker vessels will probably be stationed permanently around the platform. This was an obvious solution for the FPU, now it’s also under review for the spar.

“Another issue we have to deal with is ice formation on the topsides and in seawater, so green water ingress becomes green ice. We will have to address this via winterization of the facilities, involving some form of enclosure in the HVAC solution. Doris is working on it with Rubin, although it’s not yet defined how this particular study will be split between the hull and the topsides.”

Processing of the gas should present fewer problems, he says. “But we don’t know yet how to treat the condensate, which comprises a low percentage of well stream. It would be better if the condensate content were higher, then it would make more money for the partners. Whatever the solution, the condensate will be sent to shore. There will be no storage onboard the platform.”

Doris has just started work on Shotkman’s subsea layout, although this will likely be the easier part of the project, according to des Déserts. “It’s only in 400 m (1,312 ft) water depth. The platform will probably be disconnectable, which means placing the risers in the central part of the spar or the turret of the FPU. Ice build-up will not be possible in these locations.”

Some form of heating may be needed for flow assurance, to avoid hydrate build-up caused by temperature cooling during disconnects or shutdowns. “But by depressurizing the flowlines, we should be OK.”

Design of the export risers will be more complicated, he says. “Shtokman will have a large diameter trunkline, so several risers will need to be connected. The subsea investment is huge,” Deguen adds, “comparable in size with big deepwater projects when you add in the trunkline.”

FEED work must be completed by April 2009. SDAG may then decide that one or both concepts are technically acceptable. The partners would then have to take a commercial decision, with the major construction awards likely to follow relatively quickly to ensure project schedules are met.