MANDEL A. Y., SHIBAKIN S.I., PINCHUK V.YU.
«Sevmorneftegaz Ltd, Russia

The Shtokman gas condensate field of the Barents Sea region is the most prepared field for development. It is located in the central part of the Barents Sea, north-east from the city of Murmansk city.

The depth of the sea in the area of the field is from 300 up to 350 m. The distance from the field to the shore (Teriberka) is about 550 km.

The below are the basic engineering solutions for the Shtokman field development:
- Subsea well completion;
- High well flow rates;
- Disconnectable floating technological platforms;
- Two-phase extended pipeline;
- Natural-gas liquefaction plant with high production trains.

In accordance with technical and engineering solutions, natural gas is to be produced using subsea production complex, then gas shall be transported via intrafield pipelines to the offshore ice-resistant technological platform.

The platform receives and treats the gas condensate mixture for its further transportation as two-phase flow to onshore via subsea pipeline.
The two-phase flow comes, via the subsea pipeline, to the onshore facilities that support the offshore facilities, where its primary treatment is made (separation of two-phase flow into gas and unstable hydrocarbon condensate).

Gas treatment and liquefaction as well as the storage of liquefied gas is carried out at LNG plant with total annual capacity of 30 mln tons of liquefied gas (nominal) (when achieving the designed output, the gas amount delivered to LNG plant will make 60% of the total amount).

It is expected to produce 71.1 bln m3/year of natural gas while developing the Shtokman gas condensate field. 56 production wells will be required to achieve the designed production rates. Well drilling is expected to be performed from the floating semi-submersible drilling rigs.

Seven subsea production modules will be used for drilling and construction of the whole well stock. The project is considered to be developed in several phases (III phases), each phase to be of 23,7 bln m3/year production capacity. Each phase is designed to have a separate technological platform, subsea production systems, pipelines.

Thus, the subsea project facilities include three floating technological platforms, which can be disconnected from the mooring anchor systems and raisers in case of possible collision with large ice blocks. Three pipelines are planned to be constructed for hydrocarbons transportation. The length of each 42” . pipeline from the offshore ice-resistant platform to onshore facilities is about 542 km.

Currently two options of the floating technological platform are under consideration:

- Type «SPAR»;
- Type «FPU».

The main specific feature of these platform types is that they are designed with regard to possible encounter with ice floe and availability of drifting icebergs in the area of the facility location.

The world expertise for offshore field development has never evidenced such a combination of ice formations affecting the platform. In view of this, for the first time in the world practice, the disconnecting elements for the mooring anchor systems and raisers have been designed for «Spar» type platform, in order to move the platform away, in case of possible collision with an iceberg.

As for «FPU» type platform, the special shape of the hull and key ship dimensions have been designed, which agree with ice-breakings vessels and which meet the requirements for the unit operation both in open water and in ice conditions. Its specific design elements also include propulsion units and azipod propulsive system in the aft of the vessel in order to ensure its self-propulsion and keeping in the position, as well as mooring turret installation in the fore end.

The final technical and engineering solutions on Shtokman field development will be taken at project stages of FEED and the Feasibility Study.

Oil and gas of Arctic shelf 2008