The FPSO should provide pig launcher/receiver facilities for the gas export pipeline and all production/test fluid transfer lines (FTLs) connected to the tension leg wellhead platform (TLWP). Pig traps should be fitted with pig detectors and type approved quick opening closures with interlocks.
Regular pigging is required for production and well clean-up/test FTLs to clear potential asphaltenes, sand, wax and sludge build up. The TLWP should facilitate round trip pigging of the production FTLs from the FPSO. The TLWP should provide facilities to launch pigs in the well clean-up/test FTL from the TLWP to the FPSO.
Operation should demonstrate the pigging loops are piggable with operation pigs and for commissioning pigging.
Pigging launchers and receivers should allow pig trains of up to two pigs to be inserted and have the ability to have chemicals injected between the pigs. The driving mean for pigging of the FTL’s should be pressurized as required to propel the pig (train) through the FTLs in series during the return trip; a dedicated pump should be provided for this operation. During injection of chemicals between the pigs the most forward pig will move into the pipe work and crude will be pumped in behind the last pig as the driving medium providing forward momentum. The flow of crude should be adjustable in order to achieve the required pigging speed. The pig receiver should have adequate online draining connections allowing both pigs to be captured in receiver prior to isolation and opening.
Pigging of the export gas pipeline will not be a normal operation. Gas pipeline pigging should be performed with equipment temporarily installed on the FPSO. Space and provisions for temporary installation of the necessary utility and safety equipment should be provided for intelligent pigging operations.
Production FTL pigging operations should be round trip from the FPSO to the TLWP and vice versa.
Non-penetrating pig indicators should be provided on each side of the production pigging loop full bore valve.
A minimum pigging loop bend radius of 3 outer diameters should be provided.
Well Clean-up / Test Pigging
The well clean-up/test line pig launcher should be designed to allow for a pig train of up to two pigs to be inserted and have the ability to have chemicals injected between the pigs. During injection of chemicals between the pigs, the most forward pig will move into the piping and motive fluid should be pumped in behind the last pig as the driving medium providing forward momentum.
Two means should be provided for pigging driving medium:
- Production from the well flowing through the test manifold, using the choke for flow control
Non-penetrating pig indicators should be installed on well clean-up/test line pig launching system.
The test FTL pig receiver should have the same functionality as the production FTL pig receiver.
The pig launcher should be fitted with a type approved quick opening closure with interlocks.
The pig launcher area should include working areas for pigging operations, including layout, manual handling and lifting. The area around the quick opening closure should be bunded.