ATMoS (Attachable Turret Mooring System) is a patented submerged turret mooring system that can be attached to any of Stena’s drillships without structural modifications to the hull. It has been designed to address the challenges of drilling in shallow water, where the dynamic positioning (DP) system alone may not be sufficient for small offset requirements. Combining ATMoS with the drillship´s DP system creates a thruster-assisted mooring system and significantly increases station-keeping capability. It is a widely applicable solution, designed for service in water depths from 100m up to 1000m.
ATMoS consists of two main parts; an upper part and a lower part. The upper part is installed on the underside of the drillship by means of a patented attachment system and includes the turret which allows the ship to weathervane. The lower part incorporates winches with attached mooring lines and is pre-laid on location. The upper part connects to the lower part when the drillship arrives on location. It is possible to disconnect the mooring system and move off from location without retrieving the riser.
The ATMoS concept has been successfully proven during a comprehensive programme of model testing, both in open water and in ice. The concept has Approval in Principle from DNV.