NORWICH, UK – Aquaterra Energy has completed the design, supply, and installation of a platform-supported dewatering riser system for Petrofac’s unmanned Kilmar platform in the UK southern North Sea.
The equipment comprises four flanged riser sections, with integral centralizer fins and landing shoulders, and allows for controlled drainage of water from the platform’s degasser unit to the sea.
Among the design constraints, Petrofac specified a dewater riser system with a minimum design life of 10 years. This would be needed to withstand the bending moments brought on by tidal and environmental conditions in the region.
All the riser sections were sprayed with a corrosion-resistant coating. The two subsea riser sections were covered with an additional anti-fouling coating, which contains no biocides or harmful toxins, to prevent substantial marine growth.
Among the installation challenges were the absence of air supply or welding facilities onboard the Kilmar platform, and the inability of the platform crane to support the full weight of the riser system.
Aquaterra devised an alternate installation procedure that involved design and fabricating an “A” frame hoist system to lift the dewatering riser. Consideration also was given to allow deployment on future christmas tree and wellhead utility work, where crane access or working load limits are an issue.
Additionally, the company designed and manufactured a cellar deck assembly, used as a support structure for fast and safe assembly and installation of the riser system joints. The dewatering riser system was run through a spare platform slot, positioned via the existing conductor guides to secure the system in place.