Decommissioning of Offshore Installations — Experience Related to Safety and Environment and the Philosopy: “How Clean is Clean Enough?”

This paper will give a brief presentation of experience gained over the last 5–10 years of decommissioning of offshore installations in the North Sea. Focus is given to safety and environment issues, as this is the driven factor towards decommissioning and deconstruction of offshore installations. The establishment of cleaning criteria is based on experience from The Ekofisk I Field where a number of installations should be out of production and shut down prior to final disposal. The disposal solution was not yet defined; therefore a “cold phase” was defined. The installations would stay in place for an unknown period of time. Cleaning of large storage tanks, such as Brent Spar, Maureen Alpha and The Doris Tank is a challenge due to the size and layout of the tanks and the content, such as H₂S, wax, scale, sediments, etc. Special cleaning techniques and methods are developed for each tank. Reuse of installation or part of the installation is a target. Re use of the installations to what they were originally designed for, has been a main issue, but not yet succeeded. In the North Sea, no installations so far have been re used. Lot of effort is put into risk management and waste management. Risk related to deconstruction work, both onshore and offshore, is a major concern. All statistics demonstrates challenges towards work performance in deconstruction projects. It is important for the offshore industry to maintain a good reputation and to be a reliable and orderly partner for safety and environmental aspects of the industry.