With the vision of a onSubsea Factoryon the maintenance and repair work on process equipment is movedfrom topside to subsea. Operators will still have a high regularity requirement for their process plants,meaning that they need to be prepared to perform such complex subsea operations at any time of the yearand with a minimum of time spent waiting on weather (WoW).This paper will explain the solutions chosen for the world’s first subsea compression system at theÅsgard field in the Haltenbanken area in Norway.To meet the regularity requirements for the plant the process modules had to be replaceable in weatherconditions up to significant wave heights (Hs) of 4.5m. With module dimensions exceeding vesselmoonpool sizes and weights well exceeding 300t, the traditional method for overboarding and retrievalwould be to use a large capacity crane. However, crane lifts of large, heavy and complex structures willnormally have a weather limitation in the order Hs 1.0m – 2.5m.The requirement for reaching Hs 4.5m for these large and heavy modules called for new solutions tooverboarding and retrieval of subsea structures from an installation vessel.
展开▼
