Jeremy Beckman
Editor, Europe
Work on the Shtokman project in the Barents Sea is progressing largely according to plan, with completion of FEED phase expected early in 2010.
Doris Engineering and Russia’s Central Design Bureau for Marine Engineering (Rubin) are completing preparatory design work on the offshore production facilities. Their remit encompassed the platform, the subsea production system, and overall flow assurance from the wells to the onshore slug catcher.
JP Kenny has worked on the parallel subsea export lines which will extend 550 km (342 mi) to onshore reception facilities at Teriberka, 120 km (74.6 mi) east of Murmansk. Technip has FEED responsibility for this complex, which will include a pipeline terminal, a gas treatment plant, and an LNG train producing 7.5 MM metric tons/yr (8.27 MM tons/yr) for export.
Gazprom, one of the SDAG partners along with Total and StatoilHydro, also aims to send the other half of the gas produced from Shtokman through a spur line connecting to the Nord Stream trunkline to northern Europe.
Shtokman was discovered in 1988 in the central part of the Russian sector of the Barents Sea shelf. The location is around 600 km (373 mi) northeast of Murmansk, in water depth of around 340 m (1,115 ft). Gazprom estimates reserves at around 3.8 tcm (134 tcf) of gas and 37 million tons (33.5 million metric tons) of condensate. Phase 1 of the development should produce around 23.7 bcm/yr (837 bcf/yr) of gas and 205,000 tons/yr (185,972 metric tons/yr) of condensate.
Sevmorneftegaz, a Gazprom subsidiary, has the license to explore for and produce hydrocarbons from the Shtokman field. However SDAG, formed in February 2008, will own the first-phase infrastructure during the first 25 years of production. SDAG – Gazprom 51%, Total 25%, StatoilHydro 24% – also will bear all financial, geological, and technical risks associated with the development and LNG production.
Design review process
Doris and Rubin began the design studies in September 2007, initially focusing on flow assurance and topsides issues. The FEED contract was awarded formally in December 2007, with a flexible scope to allow the team to cope with screening studies run in parallel, says Nicolas Parsloe, technical manager of Surface Production at Doris’ Paris headquarters.
This was due to myriad issues that had to be addressed for operations this far north, at the same time as SDAG was putting an organizational structure in place. “Things were evolving fast from the beginning,” Parsloe points out. “At the kick-off meeting, the scope of work changed from the negotiated basis. Thereafter, many things were happening in parallel, such as ice studies and model tests.
“Initially, one company did conceptual work for a platform, while another worked on a spar, with the aim of producing a technical dossier for the launch of the CCFT (Compensated Call for Tender). The process had to be as open as possible, and then restrictions came in towards the end of the program following the selection of a floating production unit (FPU) and the switch to dual export lines. As a result of these changes, all design documents had to be revised in the first five months of 2009, including the complete process design documentation.”
Although front-end design is finished, Doris continues to support SDAG for presentation of the design documentation to Russian authorities, all of which must be prepared in English and Russian. A three-month review process is under way involving numerous local and government organizations, including the Civil Defense and Industrial Safety authorities.
“In parallel,” Parsloe adds, “Doris and Rubin have also performed an extensive comparative analysis of international and Russian norms in order to establish the codes and standards to which the offshore part of the project will be designed. No Russian codes exist for the subsea portion, so we have defined a set of rules that will be submitted to the authorities for approval.”
The FPU must comply with the requirements of the Russian Maritime Register of Shipping. “The definition of the Hull Class is RMRS ARC 5,” says Parsloe. “The hull shape and dimensions are for the CCFT to define. However, we have made an estimate of size, and we are talking about one of the largest FPUs ever designed.”
The size is governed by the amount of equipment needed onboard due to remoteness and the harsh environment. “Lay-down areas will be larger than normal,” he adds, “owing to the fact that logistics deliveries will not always be possible during the ice period.” Second year pack ice in the Shtokman area can build to thicknesses up to 3 m (9.85 ft).
In this part of the Barents Sea, roving icebergs weighing up to 8.8 million tons (8 million metric tons) represent a major threat. The FPU will be moored via what will probably be a larger-than-average turret, with the ability to disconnect while under full load. Doris drew on its experience with theTerra Nova FPSO off Newfoundland to identify design issues, although its scope for the FEED was limited to the turret’s main functional, process, and safety requirements.
“In our studies we have defined a 4 x 5 mooring line pattern, capable of resisting the ice loads,” Parsloe says.
“The subsea production spread will comprise three drill centers, each with two four-slot templates in a daisy chain. A production loop consisting of two 16-in. (40.6-cm) rigid flowlines runs from each drill center to the riser base. Two flexible risers connect each riser base to the FPU (i.e. six production risers). On the export side, there are four 14-in. (35.6-cm) flexible risers from the FPU to the trunkline riser base, then rigid jumpers to the two export pipeline end manifolds. Water depth is only 340 m (1,115 ft), so the subsea equipment is quite conventional.”
Safety/evacuation procedures
As for influences on vessel motion, wind speeds in the area reach up to 39 m/s (128 ft/s), comparable with extremes in the North Sea. “The speeds off the northern North Sea and on the Atlantic Margin are slightly higher. Currents in this region are moderate.”
As with offshore Sakhalin Island, the FPU’s various process and utility areas have to be sheltered to sustain operations in severe weather.
“Winterization is very layout dependent, and hence a CCFT activity,” says Parsloe. “A study was performed to compare enclosed areas to individual equipment winterization in order to define the winterization philosophy.
“There is a trade-off between safety/explosion risks and heating/tracing requirements. In general, the areas requiring maintenance have to be enclosed since personnel cannot stay outside for lengthy periods of time – in winter, for 69% of the time work is limited to one hour. Normal operation is permitted down to -24° C (-11° F), shutdown at temperatures below -32° C (-25.6° F), with -38° C (-36.4° F) the allowable working limit for critical equipment.”
However, in the event of gas build-up on the platform, the enclosures may have to be minimized to ensure easy access to escape routes. “The primary means of evacuation will be to standby vessels due to Shtokman’s remoteness from land. Otherwise, the safety systems are those found on standard FPSOs with the exception of the integration of two levels of emergency disconnection of the turret in a very short period of time.”
Action also may be needed to evacuate the crew by air, should a serious incident arise during the ice formation season. According to Parsloe, this may entail a larger than normal helideck area on the FPU that can accommodate several of the special helicopters adapted to transport greater numbers of passengers. A search and rescue helicopter may be stationed permanently on the FPU, which could be a world first. Another problem to be addressed is satellite reception this far north, which can hamper communication between vessels.
Shtokman’s wellstream contains a relatively low proportion of condensate. On arrival at the platform, liquids will be separated, with water removed from both gas and condensate. Following compression of the gas, the condensate will be re-injected into the gas for export through the trunklines to mainland Russia. Process equipment also will include facilities for MEG injection to prevent hydrate build-up in the subsea production system during shutdown or disconnection.
Emissions are an issue yet to be resolved. “Rather strict environmental conditions will likely apply. The issue is getting approvals from the authorities, as there has never been offshore production in this region.”
The FPU will need dedicated icebreaker vessels in attendance at all time, but the design and capabilities should be no different from those of ice-class vessels currently navigating the Barents Sea. “Ice build-up around Shtokman is very similar to conditions around the Snøhvit field – other areas in the Barents and Pechora seas have more ice cover. The problem with pack ice formation in this region is that it can change direction at any time, and suddenly. Hence, a moored vessel needs to have the pack-ice broken all around it so that large loads are avoided due to a change in direction of flow.”
For maintenance and inspection purposes, the intention is to have an ROV on one of the permanently stationed vessels. To minimize maintenance requirements, the FEED team avoided novel technical solutions as much as possible.
At peak periods during the FEED campaign, Doris and Rubin supplied over 200 staff to this project. The St. Petersburg Technical University contributed specialized studies for ice dynamic loads.
“As expected by its customer, Doris has demonstrated its ability to perform a major piece of engineering in a very flexible way. It has also been able to transform, in a timely manner, its alliance with a Russian engineering partner in a significant success,” says D. Bertrane, SDAG Offshore deputy director.
“Once the development has been approved,” Parsloe adds, “Doris may be involved in the team following up on detailed design and construction activities. We also hope our involvement in Shtokman will lead to other work in the region: we are interested in building a relationship with Rubin to carry on in this part of the world.”
