(28g) Paraffin Deposition in Stratified Gas and Oil Production Lines

As the global energy demand continues to increase, the oil and gas industry has had to expand its operation to ultradeep water and extreme environments. This has introduced many challenges to flow assurance, making ensuring products' profitable and safe flow a greater challenge. Wax deposition is one such major challenge to flow assurance, as wax crystals are prone to precipitate and deposit as the oil temperature drops below the wax appearance temperature. Understanding this phenomenon and how to prevent or mitigate it is crucial to minimize associated risks and losses to production. While most of the work in this area is focused on single (liquid) phase conditions, wax deposition could occur in multiphase as well. The difference in hydrodynamic and heat transfer in multiphase and their dependence on flow regime could affect the wax deposition and mitigation strategies.

This work investigates wax deposition in stratified gas and oil flow in pipes. It was found that, while in stratified smooth deposition occurred at the bottom section of the pipe only, as the flow transitioned to stratified wavy, deposition in the top was observed due to liquid contact with the top section of the pipe. Here, three stages to explain the deposition in the stratified flow regime were observed. Stage 1 represents the initial deposition at the bottom of the pipe due to direct contact between the cold pipe wall and the liquid phase. Stage 2 starts as the deposition starts to appear at the upper portion of the pipe wall. Lastly, stage 3 defines the slowing in wax deposition growth and increase in hardness as the complete pipe wall is covered. These findings will aid in developing better prediction models and establishing guidelines to minimize the effect of wax deposition issues in multiphase flow.