Subsea well intervention has been performed extensively over at least two decades to service wells and to increase recovery from these wells.
It is a well known fact that subsea wells normally underperform platform wells in recovery between 15-20%. To a large extent, the gap in recovery is related to the high cost in access to the subsea well compared with surface or platform wells.
Efficient and low cost well intervention techniques are of the outmost importance for increased field recovery. Riserless Light Well Intervention (RLWI) is one of the tools helping to close the recovery gap.
RLWI operations are now common in shallow water depth up to 600 meter although at least one operation has been performed on 906 meter water depth.
Considerable efforts have been made to improve the RLWI system with respect to efficiency, weather sensitivity and at last – but not least – deep water compatibility.
During RLWI in deeper water, the environmental loading on the wireline from the vessel to the subsea equipment becomes the limiting factor as the wire is subjected to considerable loading from sea current.
Welltec, one of the pioneers in RLWI operation have started an R\&D program to fully understand the limitations and to provide the operator with a tool to assess if RLWI is possible based on simulated behavior and empirical data instead of merely stating that RLWI is not possible beyond a certain water depth.