Session: 11-08-01 Production Systems and Subsea Operations

Paper Number: 79456

79456 - Influence of Pigging Velocity on the Wax Removal Process in Subsea Pipelines 

Wax deposition has been a significant concern in flow assurance. Mechanical pigging is the most common technique used to remediate wax deposition in subsea pipelines. Although researchers have revealed the wax removal process of pipe pigs, it is still unclear whether the pigging velocity has an effect on the pigging process. The lack of understanding of the wax removal process makes the field pigging operation rely heavily on rules of thumb, resulting in frequent blockage accidents. 
In this work, the effect of pigging velocity on the wax removal process of cup pigs and disk pigs was investigated using the indoor pigging facility. The experimental results show that the wax removal process of both pipe pigs at high and low pigging velocities can be divided into four phases. However, the wax breaking force at high pigging velocity is about 2-4 times higher than that at low pigging velocity. Also, the wax breaking force of the disk pig is higher than that of the cup pig under the same pigging conditions. 
The mechanism behind this phenomenon is due to the rheological properties of wax deposits. Since the wax deposit exhibits rheomalaxis elasto-viscoplasticity, it is subjected to a higher shear rate at high pigging velocity,  which leads to the higher dynamic yield stress of the yielded wax layer. And, the difference in wax breaking force between cup pigs and disk pigs results from the geometric characteristics of the pipe pigs. This work can provide theoretical guidance for field pigging operations in subsea pipelines.

Presenting Author: Xun Zhang China University of Petroleum (beijing)

Authors:

Xun Zhang China University of Petroleum (beijing)
Qiyu Huang China University of Petroleum (Beijing)
Wei Chen China University of Petroleum (Beijing)