Abstract

Ice may form in pipelines where ambient temperature is below freezing point of water. It was reported that ice delayed the restart of the Poplar pipeline system which gathers crude from Montanan and North Dakota (Sunne, 2015). Concerns of ice also exist in the Trans-Alyeska Pipeline System. The declining throughput makes the oil get colder much faster. If oil temperature is below the freezing point, ice forms, which may coat critical valves, accumulate in the pipe and restrict flow (APSC, 2011).

This paper investigates the mechanisms of ice formation, its behaviors and impacts on oil transportation systems. A 2-inch inner diameter carbon steel flow loop was instrumented to measure pressure, temperature, and differential pressure. The effects of pipeline components, fluid properties, and water fractions were analyzed using the experimental setup. The experimental results show that ice formation can restrict flow at the low sport in front of the flow meter, the inserted thermocouples, and the perforated plate. Annular ice deposition was found at the pipe wall. The morphology of the deposition on the pipe wall was rime ice, indicating the deposition was due to small ice crystals sticking to the pipe surface. In addition, the formation of annular deposition requires a negative temperature gradient. The mechanisms for ice deposition along the pipe are discussed.

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