Kizomba ‘A’ TLP FMD Inspection of Tendons

Angola, West Africa, 2004

In 2004 FoundOcean’s HydraScope Flooded Member Detection System was utilised by Oceaneering International, on behalf of Esso Exploration Angola, to perform an FMD inspection of the recently installed Kizomba ‘A’ TLP (Tension- Leg Platform). The platform was located approximately 370 km northwest of Luanda, Angola in a water depth of 3940ft (1200m) and was the first TLP to be installed in the West Africa region.

The HydraScope FMD System is more commonly used to inspect members on steel jacket structures, in water depths of only a few hundred meters, but on this occasion the Client required 8 no. steel tendons to be checked for any through-wall cracking or corrosion.

The platform was anchored to the seabed via eight steel tendons of 32" (813mm) OD, two at each of the four corners. Each tendon terminated inside a driven pile on the seabed and was held in place by means of a locking mechanism, and a gripper secured the top of each tendon to the platform. The tendons were of hollow design, and were to be totally free of any seawater. The FMD inspection was required to be carried out as close as possible to the top of each pile to ensure that even the smallest quantity of water would be detected.

The HydraScope FMD System was mounted on the manipulator arm of an Oceaneering SCV31 Work-Class ROV (Remotely Operated Vehicle), with data from the subsea detector unit transmitted to the surface computer via the ROV fibre-optic umbilical. The FMD system successfully obtained several readings at each location in water depths ranging from 3884ft (1184m) to 3891ft (1186m).

Several factors were important in successfully completing the project quickly, accurately and efficiently.

• FoundOcean were able to provide the complete HydraScope FMD system in two trunks, with radioactive source and frame, for air freighting to Angola at relatively short notice.
• The inspection was completed in a single dive, which was important, given the water depth and subsequent transfer time between surface and work-site.
• The HydraScope FMD equipment proved to be both robust and reliable in very deep water.

The data gathered from the readings taken on each tendon was able to confirm with 100% reliability that no seawater was present, and therefore demonstrated that no through-wall cracking had occurred on any of the tendons. This was an important step for oil & gas production in West Africa’s deep-water fields as it utilised a new platform design in untried water depths.