Identifying Optimal Pigging Frequency for Oil Pipelines Subject to Non-Uniform Wax Deposition Distribution

Wax deposition in oil pipelines causes reduced throughput and other associated problems. Periodical pigging program can effectively minimize the cost of wax deposition. This paper shows a typical pigging case study for a field pipeline subject to non-uniform wax deposition distribution by using a developed wax deposition model. The model prediction results prove that the wax is distributed in a short, localized accumulation along the first half pipeline. The resultant pressure drop along the pipeline was examined to reveal the effects of non-uniform wax deposition distribution on the pipeline production. In extreme case, the pressure drop of severe localized section increases by 50%, while this value between pump stations is merely 3%. A maximum wax thickness of 2–4 mm is used as a criterion to determine an optimal pigging frequency. The case study pipeline is recommended to be pigged at a frequency of 10 to 15 days, using by-pass pigs.