Prirazlomnaya reaches Murmansk
January 18, 2011
Gazprom has performed a complex operation on the ice-resistant platform towing.
In late November 2010 Gazprom finalized a complex operation on delivering the Prirazlomnaya offshore ice-resistant stationary platform from Severodvinsk to Murmansk.
The experts faced a tough challenge – the platform was to be delivered from the water area of Sevmash Production Association, where the main parts of it had been produced (caisson, topsides and accommodation module) to the Shipyard No.35 in Murmansk. It was necessary to deliver the platform because the ballasting operations were to take place in the deepwater ice-free Kola Bay. There, the platform will be loaded with 130 thousand tons of ballast to increase its draft from 7.7 to 15.7 meters. The port water area, the tow-out and seaway channels of Severodvinsk are simply not deep enough to perform such operations.
The platform had to be carried to the distance of nearly 450 miles or over 800 kilometers by sea from Severodvinsk to Murmansk. 6 Russian-flagged high-powered tugboats were engaged in transportation of this large-tonnage construction, namely, EEMS tug/supply vessel, Vladislav Strizhov versatile icebreaker, Pasvik tug/supply vessel, Neftegaz 57 tug/supply vessel, Neftegaz 61 tug/supply vessel and Captain Martyshkin tug/supply vessel. Towing of such a big object nearly 140 meters wide and long with the weight of some 120 thousand tons (net of concrete ballast) was unprecedented in Russia.
The experts had to deliver the platform before the end of the ice-free season, so they were very short in time – intense ice formation starts in the Severodvinsk port water area in mid-November. It was resolved not to postpone the towing till spring as concreting of the platform in Murmansk would take 1.5 to 2 months and a similar time period will be required to fill the berm with chipping and pebbles as a preventive measure against soil erosion after stationing the platform. According to expert calculations, it would be impossible to complete all the offshore operations during one navigation season before the storm and ice season.
The Prirazlomnaya platform towing operation started on November 18, 2010. 4 high-sea tugboats and 4 port tugboats were involved in mooring and towing in the Severodvinsk port. At end of the channel two more towing vessels joined the 4 high-sea tugboats. The towing project was elaborated by Krylov Shipbuilding Research Institute, while the experts of Gazprom neft and Sevmash Production Association prepared Prirazlomnaya for offshore operations. Experts from Gazprom neft shelf and Gazprom dobycha shelf took part in the platform transportation as well.
Prior to the offshore operations, it was necessary to obtain permits from the Russian Maritime Register of Shipping, the Arkhangelsk and Murmansk port authorities, insurance companies and the Northern Fleet. The work was also done to examine and prepare the Shipyard No.35 water area where the platform would be stationed.
A favorable long-term weather forecast (5 to 10 days) is required for offshore operations especially in the White and Barents Seas with their rapidly varying weather conditions. Data has to be obtained from at least three independent meteorological centers so as to ensure that the weather forecast is most accurate. The forecast showed that the weather conditions were favorable for the operation startup. But the forecast is no guarantee of a really good weather.
On November 21, the third day of the operation, the weather rapidly changed for the worse when the platform was at the end of the White Sea Throat. The wind intensified to 15–17 m/s sometimes gusting to 25 m/s and could possibly reach 35 m/s. The towing operation leader resolved to keep the vessels from the storm in a shelter. The platform and the accompanying vessels retraced the course. The platform was hidden from the wind offshore the Kola Peninsula near Kandalaksha. On the next day, once the wind strength decreased and favorable weather forecasts were received, the vessels laid the course to Murmansk again.
In a couple of days another trouble occurred – the engine of the Neftegaz 57 tug/supply vessel broke down and it had to be withdrawn from the list of towing vessels. However, there was no need for extra assistance – 5 remaining tugboats redistributed the towing load and continued towing the Prirazlomnaya platform.
On November 27, nine days after the operation startup, the platform arrived in Murmansk and was stationed near Shipyard No.35 and connected to 10 anchor lines on November 29.
Major challenge ahead
The platform construction is to be completed this winter with concrete ballasting to start in early spring 2011. In late June – early July, an even more complex operation will begin: the platform will be towed from Murmansk to the Prirazlomnoye field located on the Pechora Sea shelf after the field area is completely freed from ice. The platform with increased draft is to cover a longer distance – some 550 miles or 1,000 kilometers.
After placing the platform in the center of the field, where the sea depth is nearly 19 meters, a safety berm will be laid around it. Simultaneously, preparations for drilling will be initiated. It is expected to begin oil production from the Prirazlomnoye field in the fourth quarter of 2011. The platform will allow for the required year-round process operations: well drilling, oil production, storage and loading to tankers as well as heat and power generation.