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Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

Numerical Simulation Study of Multiphase Subsea Pipeline Sand Deposition Law
Wenxin Zhang , Hongju Chen, Liangsheng Zhou
CNOOC Research Institute Ltd.
Beijing, China

ABSTRACTThe depositional sands formed inside the multiphase subsea pipeline
will result in reduction of pipeline flow area as well as the inhibitor
efficiency, and may lead to severe PIG block accidents. The sanddeposition law in subsea pipeline has a very important influence on thedistribution of corrosion inhibitor and pigging frequency, however
there is little research on sand deposition law in multiphase flow atpresent. This paper performs numerical simulations by FLUENT toinvestigate the sand deposition law of horizontal and bend section ofsubsea pipeline associated with different parameters.

(a)

(b)

Fig.1 Diagram of Leakage Points
Note: (a) Leakage point of inner pipeline(b) Position diagram of leakage points(c) Leakage point of outer pipeline

KEY WORDS: Sand; deposition; simulation; FLUNET; bend(c)Therefore, the deposition law of sand particles in subsea pipeline has avery important influence on the distribution of corrosion inhibitor andpigging frequency. At present, studies (Zhang, 1997; Zhang, 2005; Fei,1994) on pipeline transport sand deposition mainly focus on slurrytransport, that is, horizontal pipeline transport with large sand content(more than 10%), while there are few studies on fluid transport withlow sand content (less than 1%) and the bend part of subsea pipeline.
Therefore, in this paper, FLUENT is used to numerically simulate thesand deposition law of horizontal pipe section and curved pipe under
low sand content of subsea pipeline to demonstrate the feasibility ofnumerical simulation, so as to predict the time and location of sanddeposition, guide the determination of pigging cycle and reduce thecorrosion risk caused by sand deposition.

INTRODUCTION
Depositional sands as well as wax and so on will be formed inside themultiphase subsea pipeline in operation for some time, which will be aserious threat to pipeline operation safety and should be cleaned
regularly.
The design life of the multiphase subsea pipeline from Platform A toplatform B of offshore oil and gas field is 15 years, but many leakage
points appeared in less than 5 years, which seriously affected thenormal production of the oil field. Leakage points are shown in Fig 1.
New and old leakage points appear for more than 40 times in total.
Leakage points of the inner pipe mostly occur in the middle and back of
the subsea pipeline and the outlet section. The thickness of sanddeposition is only a few millimeters, which has little influence on theflow area of the pipeline (less than 1%). However, it was noted(Jia,2013) that the sand covers the inner surface of the pipeline,
preventing the corrosion inhibitor from covering the metal surface,making the actual concentration of the corrosion inhibitor on the metal
surface less than the injected concentration, affecting the efficiency ofthe corrosion inhibitor (only 20%).

The research results can be used to formulate pigging operation plan for
multiphase subsea pipeline containing sand oil, gas and water, and lay afoundation for studying the distribution and efficiency of corrosion
inhibitor.

ESTABLISHMENT OFDEPOSITION MODEL

SUBSEAPIPELINE

SAND

Model Establishment
In this paper, the subsea sand deposition law is studied by numericalsimulation. The sand-containing pipe flow is a typical liquid-solid twophase flow with low phase holdup. The Mixture model proposed by Yu

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