Island Offshore has since 2005 been operating riserless well intervention units in the North Sea. The first unit has successfully performed more than 50 well interventions since start April 2005. Another two units have been put into operation in 2009. Both are purpose built based on experiences gathered from the first unit.
The paper will discuss the operating experiences from the first years and how these experiences have influenced two second generation well intervention units..
Further, the presentation will also discuss challenges for this type of service as well as future opportunities
Currently there are more than 5000 subsea wells world wide and the number is growing, particular in areas like West Africa and Brazil. In the North Sea there are approx. 1300 subsea wells of which about 500 are located on the Norwegian Continental shelf (NCS). The intervention frequency on subsea completed wells should in theory not deviate substantially from platform wells. Platform wells on average experience an intervention every 4th year, while subsea wells more rarely are being maintained.
There is a significant discrepancy between UOR (ultimate oil recovery) for platform wells vs. subsea completed wells; as from subsea wells UOR < 35%, platforms wells experience >50% UOR (some fields > than 70%, North Sea - Statfjord).
On the Norwegian sector of the North Sea, Statoil during 2009 did totally 25 well interventions utilizing two specialized units for RLWI. The cost benefit by these operations, according to the operator, did result in a net profit of approx. $ 2,5 billion.
During 2010, approx. 40 well interventions are scheduled utilizing the same units, while a third unit will be operating on the UKCS, West of Shetlands, (WoS) extending the operation to even harsher environment.
During 2009, two of the units, (Island Frontier and Island Wellserver), have been operating on the NCS, while the third unit Island Constructor, has been operating mainly on the UKCS, WoS.
