474838 Hydrate Blockage Risk Assessment in Gas-Dominant Pipelines

Tuesday, November 15, 2016: 2:55 PM
Union Square 22 (Hilton San Francisco Union Square)
Thomas Charlton1,2, Zachary M. Aman2, Carolyn A. Koh1, Michael L. Johns2 and Eric F. May2, (1)Chemical and Biological Engineering Department, Colorado School of Mines, Golden, CO, (2)University of Western Australia, Crawley, Australia

Hydrate formation in subsea gas pipelines is a critical design and operating risk, where the complete hydrate avoidance via thermodynamic inhibition can significantly increase the value of offshore production systems. A reduction in the injection rate of hydrate inhibitors, or the use of hydrate management approaches including kinetic inhibition, relies on understanding a comprehensive mechanism for hydrate blockage formation. The development of this conceptual mechanism for gas-dominant pipelines remains an outstanding objective, which has recently been advanced through the collection of laboratory- and flowloop-scale experimental data. This presentation will introduce a new blockage mechanism based on single-pass gas-dominant flowloop experiments collected in Perth, Western Australia and available data from industrial field trials. The new gas-dominant mechanism for hydrate blockage highlights the importance of liquid water entrainment in the gas phase, where aerosolized water droplets can convert to hydrate particles at kinetic rates. The subsequent sedimentation of these particles then enables severe wall build-up and sloughing events, which have been visually confirmed in flowloop experiments and field trials. This new conceptual mechanism suggests that the surface area of water in the gas pipeline is a critical operating parameter, with small diameter pipe segments being at particularly high risk of blockage due to the enhanced liquid droplet entrainment associated with increased gas velocities, and/or due to gas bubble entrainment in liquid collection associated with the bathymetry.

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