Worldwide there are more than 3000 subsea wells and, to increase the oil recovery from these wells, there is a demand for an efficient live well intervention service. This includes repair, scale removal, installation and manipulation of valves, plugs, screens, etc., perforations and re-perforations, zone isolation, fluid sampling, chemical treatment, well abandonment etc. Traditionally, this type of work has been done by drilling rigs since these were fitted with the necessary equipment for carrying out the position operation, the entering of the well and lowering of the tools into the well. However, with this approach several days of operation is required before any productive work in the well can commence due to the time required for positioning and anchoring of the rig and installing the workover riser system.
In recent years there is a trend to use light well intervention technology which makes this type of service possible from a ship-shaped well intervention vessel. The technology reduces the intervention cost to 1/3, enabling more intervention work and resulting in better exploitation of subsea wells.