Risk-Based Verification in Decommissioning

DNV has been awarded a contract that involves safety, health, environmental and structural verification of the engineering and planning of the removal of the Ekofisk Tank’s topside in the North Sea. Risk-based verification methods will be employed in this decommissioning project and this will take place prior to any offshore deconstruction or removal. The project, which involves the dismantling and removal of approximately 24,000 tonnes of topside facilities, is currently in its engineering and planning phase and is due to start offshore during the summer of 2005.

A risk-based verification approach aims at balancing the efforts to control the operational and technological risks. It also provides for cost and time savings by focusing on criticality. The high-risk elements are described in a verification plan together with the method of examination and verification. This methodology ensures that the focus is on critical elements through the whole deconstruction and removal project. The removal contractor will basically use excavators to cut steelwork and process equipment into suitable pieces for container transport to shore and then to recycling. The Ekofisk Tank was used as an oil storage tank for 25 years, starting in 1974. Since 1998, it has not been used for any specific operations. The Tank’s height - including its outside protection wall - is 106 meters while its diameter is 140 meters.