Decommissioning and removal of offshore structures represent a significant challange to the oil industry, government, offshore constructors and other parties involved. As oil and gas become exhausted associated field platform installations will be decommissioned and considered for removal in some measure to comply with the International Maritime Organization (IMO) Guidelines and Standards. The Guidelines derive from a general obligation to remove abandoned or disused offshore installations and describe the circumstances in which non-removal or partial removal may be allowed. This paper will focus upon technical, legal and economic aspects related to decommissioning and removal of offshore installations. Key Words: Decommissioning, Offshore installations, Regulations, Technology,
There are currently in excess of 6500 platforms worldwide which must be consid ered for removal after disuse. Estimates to remove all 6500 range in excess of US$ 30 billion. The offshore industry had its beginning in 1947 in 20 feet of water in the Gulf of Mexico. Technology has advanced in more than 40 years to where fixed structures now exist in water depths of about 400 metres in the Gulf of Mexico and installations are being designed for the Norwegian Sector as large as 700000 tons. These structures will be extremely costly and difficult to remove. Some may also be impossible to remove with current
Five main alternatives exists;
Complete removal of the installation. Concrete platforms are refloated with deballasting or overpressuring in the skirt chambers. Steel platforms are cut below the mud1ine. The facility is taken to land or towed out to deep water for dumping.
Toppling. The installations are removed by cutting off the legs a little above the mudline. Then it tips over and remains on the Sea bottom. This is a nearly i, mpossible method tor concrete platforms.
