The Problem
Our client planned to tie a new development into an existing 24” export line at an in-line spool, by removing the spool and installing a new 24” wye structure. The existing line and the new development would tie in to the wye structure and tie in spools.
As part of the installation and commissioning philosophy, it was decided to utilise an isolation solution to isolate the existing pipeline during the tie-in operations. Isolation pigs were to be used to facilitate both the removal of the existing tie-in spool and the tie in of the existing line to the new wye structure.
Our objective was to determine the most suitable options for mitigation in the event of a failure to seal, or a failure to unset the isolation pigs.
The Solution
We have an excellent knowledge of pig design and pigging assurance. Using this experience, we assessed the designs of the pigs and the piggability of the system, to ascertain the likelihood of a failure of the pig as well as the possibility of pipeline component damage or a stuck pig.
We also provided a list of remediation methods that could be used in the event of a failure of the isolation plugs. These included methodologies for returning the plugs to the platform, or removal of the plugs in the event of a failure to unset.
The Benefits
By calling on our experience of subsea pigging, Jee provided the client with a comprehensive assessment, covering all credible failure scenarios, as well as delivering a detailed assessment of mitigations that could be employed to reduce the risk of failure, and remedial actions that could be used in the event a failure did occur.
We were also able to provide a cost estimate for remedial options, calling on the network of suppliers and contacts built up as an independent consultancy. This allowed the client to make decisions based on the actual risk and cost of failures of the isolation plugs.
