Confirming its growing profile as a market leader in specialist offshore engineering solutions, Aquaterra Energy has successfully completed the design, supply and installation of a platform supported dewatering riser system for a platform in the Southern North Sea.

Approached initially by Petrofac to conduct a FEED study ensuring the feasibility of a dewatering riser system, Aquaterra Energy’s subsequent demonstration of engineering experience, creative in-house design and the ability to provide customised solutions, secured the company the full scope contract.

The new Aquaterra Energy dewatering riser system comprises four flanged riser sections, complete with integral centraliser fins and landing shoulders, and allows for the controlled drainage of water from the unmanned platform’s degasser unit to the sea.

As a specialist supplier of Offshore Risers, the company had the design knowledge and skills to develop an optimised solution for Petrofac, working within several design constraints.

Firstly, Petrofac required a dewater riser system with a minimum design life of 10 years, that would withstand the bending moments encountered by the tidal and environmental conditions of the Southern North Sea, with little on-going maintenance requirement.

To ensure this longevity, all riser sections were sprayed with a corrosion resistant coating and the two subsea riser sections were covered with an additional marine friendly Anti-fouling coating, containing no biocides or harmful toxins, to prevent substantial marine growth.

Several major obstacles had to be overcome during installation of the new system.  There was no air supply or welding facilities onboard the platform, and the platform crane was unable to support the full weight of the riser system.  So, Aquaterra Energy devised an alternative efficient installation procedure, in the form of a uniquely designed and fabricated ‘A’ frame hoist system, to lift the dewatering riser.  In its design, consideration was also given to allowing it to be used on future Xmas tree and wellhead utility work, where crane access or working load limits are an issue.

Aquaterra Energy also designed and manufactured a Cellar Deck Assembly which was used as a support structure for swift and safe assembly and installation of the riser system joints. The dewatering riser system proceeded to be run through a spare platform slot, positioned via the existing conductor guides to secure the system in place.

Ben Cannell, Project Manager at Aquaterra Energy said: “We have teams of experienced and highly creative engineers, focused on solving offshore challenges and this project posed several issues for us to work through.  Our experience of tackling a project with no immediate off-the-shelf solution put us in a positive position to be able to design, supply and install a high quality, long-life dewatering riser system for Petrofac, that met all their requirements and deadlines.”

Karim Ouaddane, Project Manager at Petrofac said: “I would like to congratulate Aquaterra Energy for their teamwork, solution focused approach, and their commitment to Petrofac safety culture”.