Vessel evaluation for inspection, maintenance and repair on the Subsea Factory

Abstract

Technical solutions for subsea field developments have seen a rapid growth in complexity over the last years. Today the oil & gas industry is getting ready for a step change by implementing subsea processing facilities. Implementing the equivalent of a topside processing facility on the seafloor brings several challenges, one being the inspection, maintenance and repair (IMR). The main objective of this thesis is to define the challenges related to IMR on a subsea processing facility and to evaluate which vessels are able perform the required IMR operations such a facility would require. The evaluation will be based on the components of the Åsgard subsea compression station. To evaluate vessels ability to perform the IMR operations the data simulation program ORCAFLEX is used. The most critical part of the operation is the splash zone crossing phase so the analysis is based around this. The results from ORCAFLEX are also combined with the weather criteria found at the location. The result of the analysis shows that the operations the vessels can perform varies greatly depending on what module is lifted with what vessel and that some modules cannot be lifted in high sea states no matter what vessel is used. The analysis also indicates that the largest vessel used in the simulation may be over dimensioned and that a smaller vessel could be used for the same operations. If medium sized vessels are able to the IMR work for the subsea processing facility, the existing IMR vessel fleet can be put to use to prevent unnecessary expenditures.