Pigging has been recognized as the most cost-effective method for preventing flow restriction by wax deposits in subsea flowlines. However, the pigging mechanics for wax removal in pipelines is still very poorly understood. A unique test facility was designed and constructed for experimental studies on the mechanics of wax removal in pipelines. The test facility consisted of a test section, a support structure, an apparatus to pull the pig through the test pipe, and a computer-based data acquisition system. The test section was long and was made from inner diameter schedule-40 steel pipe. The mixture of commercial wax and mineral oil was cast inside the test section at different wax thickness and oil contents. A series of experiments was performed to investigate the wax removal mechanics with three different types of conventional pigs, i.e., cup, disc, and foam pigs. The experiments showed that a typical wax removal process using a pig followed four distinct phases, namely, wax breaking, plug formation, accumulation, and production phases. Wax accumulation can be very significant and is expected to be the dominating factor for the force required for moving a pig in long pipelines. As wax thickness and hardness increases, the required force to move the pig increases. The shape and material of the pig have a profound effect on the wax removal performance. While the disc pig provides the most efficient wax removal, the force requirement is excessive, especially for thicker and harder wax deposits. The wax removal performance of a cup pig is very similar to that of a disc pig. However, the cup pig can withstand higher load without mechanical damages than the disc pig. The foam pig offers the poorest wax removal performance.
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December 2005
Research Papers
An Experimental Study on Mechanics of Wax Removal in Pipeline
Qian Wang
Qian Wang is a Research Associate in the Tulsa University Fluid Flow Projects (TUFFP) and Paraffin Deposition programs at The University of Tulsa. She holds Ph.D. degree in Mechanical Engineering from Xi’an Jiaotong University. She served as Assistant Research Professor and Associate Research Professor in Chinese Academy of Sciences (1990–1999) where she worked on projects in the United Nations Developing Program and studied circulated fluid bed combustion. She also worked on the Deepstar project for Mechanics of Wax Removal at Penn State University (2000).
Qian Wang
TUFFP,
The University of Tulsa
, Tulsa, OK 74104
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Cem Sarica
Cem Sarica, Professor of Petroleum Engineering at The University of Tulsa (TU), holds a Ph.D. in petroleum engineering from TU. He has worked for Istanbul Technical University (ITU) as an Assistant Professor of Petroleum Engineering, TU as Associate Director of Tulsa University Fluid Flow Projects (TUFFP), and The Pennsylvania State University as Associate Professor of Petroleum and Natural Gas Engineering at the Energy and Geo-Environmental Engineering Department. He is currently serving as the director of TUFFP and Tulsa University Paraffin Deposition Projects. He served as an Associate Editor of Journal of Energy Resources Technology for six years.
Cem Sarica
TUFFP,
The University of Tulsa
, Tulsa, OK 74104
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Tom X. Chen
Tom X. Chen holds a Ph.D. degree in mechanical engineering and has experience in research, development, and application of multiphase and flow assurance technologies. He has published 50 technical articles in referred journals and international conferences. He is a subsea engineer focusing on novel deepwater production systems with Shell International Exploration and Production Inc. in Houston, Texas. Prior to joining Shell in 2003, he worked for Tulsa University Fluid Flow Projects (TUFFP), Texaco Upstream Technology, and ExxonMobil Upstream Research Company.
Tom X. Chen
Texaco Inc.
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Qian Wang
Qian Wang is a Research Associate in the Tulsa University Fluid Flow Projects (TUFFP) and Paraffin Deposition programs at The University of Tulsa. She holds Ph.D. degree in Mechanical Engineering from Xi’an Jiaotong University. She served as Assistant Research Professor and Associate Research Professor in Chinese Academy of Sciences (1990–1999) where she worked on projects in the United Nations Developing Program and studied circulated fluid bed combustion. She also worked on the Deepstar project for Mechanics of Wax Removal at Penn State University (2000).
Cem Sarica
Cem Sarica, Professor of Petroleum Engineering at The University of Tulsa (TU), holds a Ph.D. in petroleum engineering from TU. He has worked for Istanbul Technical University (ITU) as an Assistant Professor of Petroleum Engineering, TU as Associate Director of Tulsa University Fluid Flow Projects (TUFFP), and The Pennsylvania State University as Associate Professor of Petroleum and Natural Gas Engineering at the Energy and Geo-Environmental Engineering Department. He is currently serving as the director of TUFFP and Tulsa University Paraffin Deposition Projects. He served as an Associate Editor of Journal of Energy Resources Technology for six years.
Tom X. Chen
Tom X. Chen holds a Ph.D. degree in mechanical engineering and has experience in research, development, and application of multiphase and flow assurance technologies. He has published 50 technical articles in referred journals and international conferences. He is a subsea engineer focusing on novel deepwater production systems with Shell International Exploration and Production Inc. in Houston, Texas. Prior to joining Shell in 2003, he worked for Tulsa University Fluid Flow Projects (TUFFP), Texaco Upstream Technology, and ExxonMobil Upstream Research Company.
J. Energy Resour. Technol. Dec 2005, 127(4): 302-309 (8 pages)
Published Online: January 7, 2005
Article history
Received:
November 26, 2001
Revised:
January 7, 2005
