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The 6” MOL A to B pipeline was built in 2013. The characteristics of the fluid flowing through this pipeline contain sand and wax. Throughout its operational period, weekly cleaning pigging was routinely conducted. The problem is, in 2023, regular pigging activities were halted due to operational issues, leading to restricted fluid flow within the pipeline and reduced production capacity due to debris buildup.

Based on analysis, the remaining inside diameter (ID) of the pipeline due to debris accumulation was only 4 inches from nominal ID 5.625”. To increase production capacity, progressive pigging is needed and should be conducted safely. Progressive pigging is a series of activities involving inserting pigs into the pipeline to restore its internal diameter to its original condition (by removing debris from within the pipeline). Progressive pigging starts with under sized and the least aggressive type of pig then gradually progresses to the pipe actual size and most aggressive type. During the progressive pigging activity on the 6” MOL A to B pipeline, an undersized pig stalled. Based on flow assurance simulation, it was found that there was a local narrowing at the pig stall position, with a bypass of about 25% of the pipeline’s diameter, requiring a rescue pig.

Flow assurance simulation helped the pigging engineer decide to conduct a rescue pig or kick-back process. With the support of flow assurance simulation, progressive pigging was safely conducted, and the 6” MOL A to B pipeline is now back in operation with its internal diameter restored to design specifications. The production rate prior to progressive pigging was 1007 BFPD (509 BOPD), while after progressive pigging there is 35 BOPD production gain with 74% increase of flow rate (1749 BFPD equal to 544 BOPD).