Journal of Shanghai Jiao Tong University ›› 2021, Vol. 55 ›› Issue (7): 878-890.

Special Issue: 《上海交通大学学报》2021年12期专题汇总专辑 《上海交通大学学报》2021年“工程力学”专题

### Numerical Simulation of Critical Oil Velocity Required to Completely Remove Water Lump Deposited in Hilly Oil Pipelines

LI Yansong1,4, DING Dingqian2, HAN Dong1, LIU Jing3, LIANG Yongtu1()

1. 1. Beijing Key Laboratory of Urban Oil and Gas Distribution Technology, China University of Petroleum-Beijing, Beijing 102249, China
2. Department of Mechanical and Aerospace Engineering, University of California, San Diego 92093-0411, USA
3. South China Branch of Sinopec Sales Co., Ltd., Guangzhou 510000, China
4. Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
• Received:2020-01-16 Online:2021-07-28 Published:2021-07-30
• Contact: LIANG Yongtu E-mail:liangyt21st@163.com

Abstract:

Removing the trapped water lump from the pipelines by using the hydraulic pigging (HP) method can effectively reduce the attenuation of oil quality. It is of great practical significance to study the critical oil velocity required to completely remove the water lump trapped in hilly oil pipelines. First, the flow patterns of water expelled by oil stream in an upward inclined pipeline are analyzed when the oil velocity in pipelines reachs the critical value required to completely remove the water. It is found that the flow process of the water removed by oil stream belongs to oil-water two phase stratified wavy flow. Next, the numerical model governing the flow of water expelled by oil is established in the bipolar coordinate system based on the flow pattern aforementioned, and the numerical solution method is also proposed. Finally, the numerical model is validated through the comparison of the results calculated by the model with the data from the literature. The flow of water lump expelled by diesel in an upward inclined pipeline is numerically studied, and the characteristics of the oil flow and water lump mobilization during the HP process are analyzed in detail. The results show that the water lump is mainly influenced by gravity pressure drop. The friction pressure drop could be neglected compared to the gravity pressure drop. When the oil velocity in the pipe is small, the water phase near the interface is carried downstream by the oil stream, while that near the pipe wall flows back to the bottom of the pipeline due to gravity. The postion of the minimum velocity in the water phase will shift to the pipe wall with the oil velocity increasing. When the minimum water velocity appears at the pipe wall for the first time, the oil velocity in pipelines can be regarded as the critical oil velocity required to completely remove the water lump in the pipelines.

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