The problem
A client operating a multi diameter crude oil pipeline carried out routine pigging every two weeks to manage wax deposition within the system. A cleaning pig design that had been used successfully for five years failed to arrive at the receiver following launch, indicating that the pig had become stalled within the pipeline.
The client undertook several recovery attempts, including increasing flow rates and deploying low viscosity gel slugs. Two additional recovery campaigns by external contractors were also unsuccessful. As a result, the client approached Jee for specialist support to recover the stalled pig and minimise disruption to pipeline operations.
Jee had previously supported the asset through the development of a stuck pig guidance document, creation of a pipeline bore map and assurance activities for an in line inspection tool. This prior knowledge provided a strong understanding of the system and its potential constraints, allowing the team to rapidly assess the situation and identify suitable recovery options.
The solution
Jee’s pigging specialists reviewed the available operational data to identify pipeline locations that could be susceptible to pig hold up. The team then assessed a range of recovery approaches to understand their associated risks and likelihood of success.
Following this evaluation, Jee recommended a programme of pigging trials using high viscosity firm gel pigs. The trials were designed to assess two key scenarios:
- Whether a gel pig could drive the stalled cleaning pig through the pipeline while remaining within system operating limits.
- Whether the gel pig could break apart and bypass the stalled pig if it was located in a position that prevented recovery.
Multiple gel pig densities were tested to establish the lowest risk solution with the greatest probability of success. This testing was essential because the interaction between the gel pigs and the stalled pig could not be determined with confidence without practical assessment.
Following completion of the trials, Jee took on a project management and engineering role for the recovery campaign. This included coordinating with integrity and process engineering teams, developing the offshore execution plan and reviewing pumping contractor procedures to ensure they were suitable for the operation.
Conclusion
Jee’s technical assessment, pigging trials and project management support enabled the client to successfully recover the stalled cleaning pig from the pipeline.
Recovery of the pig allowed the client to undertake root cause analysis and restart routine pigging activities for wax management. By combining previous knowledge of the asset with specialist pigging expertise, Jee delivered a practical and low risk solution that restored pipeline operations and reduced the risk of prolonged production impacts.
To contact Jee’s Head of Pigging, Sean Tucker, email sean.tucker@jee.co.uk.