Cofferdam Set Up

This photographs show UMC setting up the biggest cofferdam system they have ever been involved. The cofferdam will allow repair to the leg wells and ultimately install the three legs of a jack up rig in Oman, which was damaged during Hurricane Katrina in the Gulf of Mexico, in 2005. SeaTec developed the detail design of the cofferdam from the outline design required by UMC, the finished product coming in at just over 100 metric tonnes with an overall diameter larger than 18 meters.

So far the cofferdam construction and testing has been completed, including the special seal system that will ultimately allow the cofferdam to be drained down and result in a massive maximum buoyancy upthrust of 1500 tonnes on the structure.  The challenge was to create a dry working environment around the giant support feet (known as spudcans) of a jack up oil rig so that repairs could be undertaken on the top surfaces of each foot whilst the unit was afloat.  The cofferdam system will completely enclose each of the spudcans in turn and seal against the underside of the rig hull, and when in position the area around the spudcan can be drained down thus allowing surface workers to carry out the necessary repairs.  This in-water repair system provides a cost-effective and practical alternative to docking.