Decommissioning subsea structures, moorings requires geotechnical considerations

摘要

Decommissioning activities represent an increasingly significant proportion of North Sea offshore operations and associated engineering and will continue to do so beyond 2020. According to a recent survey by Oil & Gas UK, nearly £17 billion ($25 billion) is forecast to be spent on decommissioning approximately 79 fixed and floating installations and plugging 1,200 wells in the North Sea over the next 10 years. This represents around one-sixth of the circa 470 installations that will require decommissioning between now and 2050. Nearly all offshore topsides facilities have associated subsea infrastructure. For example, wellhead protection structures, manifolds, and subsea isolation valves. These structures are designed to accommodate the specific requirements of the field, use a variety of different foundation types, and hence are essentially unique. As such, decommissioning of subsea structures and moorings presents significant challenges for engineers, particularly for structures installed prior to the 1992/1998 OSPAR agreements, where full decommissioning may not have been explicitly considered during the original design phase.