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A NEW APPROACH TO MODEL FRICTION LOSSES IN THE WATER-ASSISTED PIPELINE TRANSPORTATION OF HEAVY OIL AND BITUMEN
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- Author / Creator
- Rushd, M M A Sayeed
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Water lubricated pipe flow technology is an economic alternative for the long distance transportation of viscous oils like heavy oil and bitumen. The lubricated flow regime involves an oil-rich core surrounded by a turbulent water annulus. Energy consumption associated with this type of pipeline transportation system is orders of magnitude lower than comparable systems used to transport oil alone. In industrial applications of this technology, a thin oil film is always observed to coat the pipe wall. The natural process of wall coating during the lubrication is often referred to as “wall-fouling”. A wall-fouling layer can result in ultra-high values of hydrodynamic roughness (~ 1 mm). A detailed study of the hydrodynamic effects produced by wall-fouling is critical to the design and operation of oil/water pipelines, as the viscous layer can increase the pipeline pressure loss (and pumping power requirements) by 15 times or more. However, the hydrodynamic effects of wall-fouling in modeling the frictional pressure loss of water lubricated pipelines have not been addressed previously. In the first phase of this research, the wall-fouling layer was replicated by coating a wall of a customized flow cell with a thin layer of viscous oil. The hydrodynamic effects of the wall-coating layer were experimentally investigated. The hydrodynamic roughness was determined in terms of Nikuradse sand grain equivalent by predicting the measured pressure gradients using commercial CFD software (ANSYS CFX 13.0). The CFD-based simulation process was validated using data produced as part of the current research as well as data obtained from the literature. In addition, the physical roughness was characterized by surface measurement, which was also used to corroborate the hydrodynamic roughness determined with the CFD simulation. This investigation brings previously unknown hydrodynamic effects of viscous wall-coating to light. Next a parametric investigation of the hydrodynamic effects caused by the wall-coating of viscous oil was conducted. The controlled parameters included the thickness of the wall-coating layer, oil viscosity and water flow rate. For each set of test conditions, the pressure loss across the test section was measured and the hydrodynamic effect of the wall-coating on the pressure loss was determined. The CFD procedure that was developed previously was used to determine the hydrodynamic roughness produced by each different wall-coating. The same procedure was also applied for a set of pipeloop test results published elsewhere. Thus, the effects of wall-coating thickness, oil viscosity and water flow rate on the hydrodynamic roughness were evaluated. An interesting outcome of this parametric study is a novel correlation for the roughness produced by a wall-coating layer of viscous oil. In the final phase of this research, a new method to model pressure loss in a water-assisted pipeline was introduced based on the results of the previous two phases. The hydrodynamic effects produced by the wall-fouling layer were incorporated in the new model as input parameters. The most important of these parameters were the thickness of wall-fouling layer and the equivalent hydrodynamic roughness it produces. The current CFD model was developed on the ANSYS-CFX platform. It captures the dominant effects of the thickness of the wall-fouling layer and the water hold-up, i.e., the in situ thickness of the lubricating water-annulus on frictional pressure loss. It was validated using test data obtained from tests conducted at the Saskatchewan Research Council’s Pipe Flow Technology Centre using 100 mm and 260 mm pipelines. Compared to existing models, the new model produces more accurate predictions. The results of the current research are directly applicable to pipeline systems in which a viscous wall-coating is produced, including water lubricated bitumen transport in the oil sands industry, Cold Heavy Oil Production with Sand (CHOPS) and Steam Assisted Gravity Drainage (SAGD) surface production/transport lines. Other potential beneficiaries of this work are the pharmaceutical and polymer industries, as flow systems in these industries can involve viscous wall-fouling. It will also be useful for industries that deal with bio-fouling on walls like oceanic shipping (ships’ bodies and hulls) and hydropower industries (pipes and channels). Most importantly, this research is expected to be immediately adopted in the non-conventional oil industry for pipeline design, operations troubleshooting and incorporation in pipeline leak detection algorithms.
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- Graduation date
- Spring 2016
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.