Throughout the months of September and October 2023, Prism Energy oversaw a complex Pipeline Pigging scope in the Irish sea. Project challenges were heightened with the primary asset normally having an unmanned status.
The project was centred around a double block & monitor (DBM) isolation tool pigging run, to facilitate the replacement of a topside valve.
Project
Prism Energy’s role was to manage the supply and hire of an isolation tool and temporary pumping spread to provide a suitable double block & monitor (DBM) isolation. The isolation tool was to be launched, and set, in the main 34” export pipeline to the onshore processing terminal. The DBM, provided by the isolation tool, would allow the execution of the critical path TAR scope, upgrading the existing export valve to a 24” valve.
The scope included the management of the isolation tool provider, the temporary pumping spread provider, Lessons Learned session, facilitation of HAZID & HAZOP sessions, attending FAT, reviewing vendor documentation and writing the overarching launching, and retrieval, operating procedure.
Challenges
Low operating pressures within the gas export pipeline deemed it necessary to pre-pack the pipeline, prior to launching the pig, with export gas reaching approximately three times the normal operating pressure but well within the original pipeline design capabilities. In addition to the low pipeline pressure, the facilities on the host platform were originally designed for pig launching only and not receiving. On the short 50m journey from the pig launcher, the isolation tool had to navigate 2 large bore isolation valves, 2 vertical back-to-back 5D bends and a 24” production tee. Preparations for the scope execution had to be carefully planned, and co-ordinated, as the scope was being executed on a normally unmanned installation (NUI).
The chosen primary set location for the isolation tool was immediately upstream of the riser ESDV (failsafe valve) therefore to gain better control of pigging the tool to isolation location, fluid was the chosen pigging medium. The recovery of the pigging fluid was a specific request from the client, due to the pipeline primarily transporting gas when operational.
Long-Term Benefits
The success of the project has allowed the platform operator to upgrade a system valve that now provides a more flexible approach to the future operation, and maintenance, of the installation.
