The installation of the modules that collectively constitute Åsgard subsea gas compression has commenced on the Åsgard field. Innovative technology at a depth of 300 metres will create 282 million extra barrels from the Åsgard field.

A total of 22 modules will be installed and connected. These comprise two identical compressor trains weighing 1,500 tonnes each.

During the summer this unique technology will be put in place in the large subsea frame that was installed on the field in summer 2013.

The installation work is being carried out by the North Sea Giant vessel, which was rebuilt for the purpose.

All the modules are provisionally stored at Vestbase in Kristiansund, from where they are shipped following commissioning and testing in Egersund.

Safety and efficiency with a special crane

The modules comprising the subsea gas compression plant vary in size. The smallest modules are being installed via the vessel's so-called "moonpool", a large opening in the bottom of the hull through which the modules are lowered. Modules with a maximum weight of up to 70 tonnes can be installed in this way.

Several of the modules to be installed in the subsea plant are too large to be lowered through the ship's moonpool. Thus, the ship's crane system has been modified to incorporate a so-called special handling system (SHS).

This lifting system is designed to carry a load of up to 420 tonnes and can operate in up to nine-metre high waves. Each module is lowered into the sea via a crane and guided into place with a ROV and cables.

"This crane system makes the installation work safer and more efficient. To ensure quality at every stage of the process, all operational crew have practised the operations in a specially designed simulator.

"We have also performed a number of sea trials prior to installation," says project director Torstein Vinterstø.

Tags: Statoil