Deconstruction of an Oil Rig

Germany's first offshore oil field "Schwedeneck-See" is situated 1,500 meters below water level in Kiel bay. A total of nearly 3.5 million tonnes (mt) of crude oil was produced from two offshore platforms (A and B) and transported via subsea pipelines and cables to onshore facilities where the crude was treated. After 16 years of troublefree operations, however, more water than oil emerged from the maritime sources, and the production stopped in June 2000.

The platforms including the substructures, or caissons, were to be dismantled in a safe and environmentally compatible manner. 

Platform A in the port of Eckernförde was sealed with the help of WEBAC PU injection foam resins before the deinstallation started. Before deinstalling the floating body, it was necessary to prevent water from penetrating the concrete substructures. To this end, the flexible pipes entering the floating body of the production platform had to be sealed. A steel lid was first welded to the pipes' ends and a water-reactive PU Injection Foam Resin (WEBAC_® 151) injected into the cavities. The wells were located approx. 16 m deep underneath the platforms. A 60 m high-pressure hose and a suitable injection pump were used to inject the foam into the pipes. Approx. 50 kg of WEBAC_® 151 were needed for each well. Due to the long injection path, the relatively low temperatures (10-12 °C water temperature and approx. 3 °C air temperature) and the relatively high air humidity (drizzle) at wind force 5-7, the injection procedure turned out to be extremely difficult.

Thanks to the team's relentless effort and commitment the injection of platform A could be successfully completed after 4 days. A total of almost 700 kg of WEBAC_® 151 was injected, 16,000 t of reinforced concrete were salvaged offshore, dismantled safely and in an environmentally sound manner, and prepared for recycling.