Study on Wax Removal During Pipeline-Pigging Operations
- Weidong Li (China Universiyu of Petroleum, Beijing) | Qiyu Huang (China Universiyu of Petroleum, Beijing) | Wenda Wang (China Huanqiu Contracting & Engineering Co., Ltd.) | Yijie Ren (China University of Petroleum, Beijing) | Xue Dong (China University of Petroleum, Beijing) | Qi Zhao (China University of Petroleum, Beijing) | Lei Hou (China University of Petroleum, Beijing)
- Document ID
- Society of Petroleum Engineers
- SPE Production & Operations
- Publication Date
- February 2019
- Document Type
- Journal Paper
- 216 - 231
- 2019.Society of Petroleum Engineers
- pigging, wax removal efficiency, wax breaking force, model development, nondimensional analysis
- 4 in the last 30 days
- 262 since 2007
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Widely used as it is, pipeline pigging still holds ambiguities in its mechanisms. In this paper we explore the nature of the wax removal process with a unique pigging facility. Solid wax content, yield stress, viscoelasticity, and microscopic characteristics of wax samples are thoroughly studied with differential-scanning-calorimetry (DSC) trials, rheological tests, and microscopic observations. We found that the relative solid wax content is approximately linearly dependent on temperature, and yield stress can be well-fitted with wax content in an exponential format. An investigation on wax-breaking force indicates that it increases with solid wax content. Wax removal efficiency increases with wax thickness and pipe-wall temperature, decreases with a wax-mixing ratio and solid wax content, and it varies irregularly vs. the scraping-element hardness in the pig. Furthermore, a prediction model of wax removal efficiency was developed on the basis of nondimensional analysis. The absolute average deviation of verification experiments against this model is 5.22%. This model might benefit in estimating the wax-scouring capacity of the wax-in-oil slurry and, therefore, helps to avoid wax blockage and to arrange the pigging program.
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