Boskalis Subsea Services executed multi-year subsea structural reinforcement campaign on Maersk Oil operated Dan Bravo Complex which came on stream in 1972.

The Dan Bravo Complex was expected to produce for 25 years, but now, thanks to a reinforcement campaign involving the installation of 136 tonnes of new steel, over more than 200 diving days, the life of the complex’s wellhead platform Dan A is expected to be doubled to total 70 years.

The project involved a large subsea photogrammetry campaign, preparation work and the installation of temporary cranes on vertical platform members to help maneuver the new steel into place – all while the platform was in production, Boskalis said.

The main scope was to reinforce Dan A’s jacket, using so called K-node clamps, and to install a new conductor guide level.

One of the challenges was mapping the existing structure, which had been extended over the years, by assessing existing inspection data and acquiring new data.

A photogrammetry exercise was carried out beneath the waves. Air and saturation divers first cleaned and marked out the structure, using 3,000 magnetic, coded markers, and then some 20,000 high-definition, overlapping photographs were taken by WROV, Boskalis explained.

The photographs were then converted into an exact geometric 3D model, using the information from the markers, from which the K-nodes and conductor level guide could be designed and fabricated onshore.

The project has been executed during 2013 up to 2015 and it is completed using Boskalis Subsea’s Diving Support Vessels “Constructor” and “Protea”.