Jee undertook a recovery operation utilising gel pigs after a client’s cleaning pig became stuck in a pipeline.
Jee’s client operates a multi-diameter crude oil pipeline which is typically pigged on a bi-weekly basis to manage wax dropout in the system. The same pig design had been used in the system for the last five years, however following launch and the expected transit of one of the pigs through the line, the pig was not located within the receiver.
The client made several attempts to recover the pig, including increasing flowrates and utilising low viscosity gel slugs – however were unable to recover the pig. Two previous attempts were made by other companies to retrieve the tool, but also failed. Following this, the client approached Jee to support with recovery of the routine cleaning pig.
Jee had previously produced a stuck pig guidance document for the system which had been followed by the client when the pig had not initially been found in the receiver. Jee had also previously created a pipeline boremap for the system and carried out assurance activities for an ILI tool a couple of years prior to the incident and therefore had a good understanding of the system from the outset.
Jee’s expert pigging team reviewed the available data to identify potential locations susceptible to pig hold-up within the system, and subsequently assessed the various recovery pig options to determine the risks and likelihood of success within each
It was then agreed with the client to perform pigging trials utilising a high viscosity “firm” gel pig to assess the following:
The testing was performed with multiple densities of gel pig to assess the best option (lowest risk with highest likelihood of success) for the client as it was not possible to definitively state the behaviour of each of the gel pigs with the routine pig, and the required pressure for the gel pig to break apart and bypass the routine pig without the testing.
Following the pigging trials, the client requested that Jee take on a project management / engineering role for the attempted recovery of the stalled pig. This included liaising with client integrity and process engineers to determine schedule, creation of offshore execution plan and review of pumping vendor procedures to ensure suitability for the campaign.
Following Jee’s support with pigging trials and project management, the client was able to successfully recover the stalled routine pig from the line to enable root cause analysis to be performed and routine pigging for wax management to recommence.
For more information, visit www.jee.co.uk/pigging, or call +44 (0)1732 371 371.