The formation of gas hydrates in subsea oil and gas flowlines is a major concern since this can cause production interruptions, and environmental and safety problems. Under gas hydrate formation conditions, hydrates can create flow restrictions, that may then lead to plugging of the flowline. The risks associated with hydrate formation in subsea flowlines increases significantly as the reservoir matures and the amount of produced water increases. The oil and gas industry recognizes the need for the investigation, development and implementation of better hydrate management strategies covering the gaps in current practices.
In helping to develop better hydrate management strategies, hydrate formation in partially dispersed multiphase flow conditions were previously investigated using a high pressure industrial-scale flowloop (Vijayamohan et al. 2016). In our recent tests using the same flowloop, the effect of hydrate volume percent on the pressure drop of the system was evaluated. The amount of hydrate formed in the system was limited by systematically controlling system temperature and gas available for hydrate formation.
In recent flowloop tests, it was also hypothesized that hydrate deposition on the pipe surface can contribute significantly to a rapid increase in the pressure drop (Grasso 2015). As such, an investigation into hydrate deposition mechanisms and their detection was performed. Deposition mechanisms were investigated using a high pressure lab-scale flowloop (Grasso 2015). In this part of the work, hydrate deposition mechanisms were evaluated by varying parameters such as liquid loading, water cut, subcooling, and liquid/gas phase velocity. The results from these laboratory-scale investigations show that both liquid and gas phase velocities have a high impact on the amount of hydrate formed in this system.
The results from the investigations presented in this paper provide new insights into hydrate formation and deposition mechanisms. It is anticipated that such investigations can lead to new possibilities for more advanced hydrate management strategies for the flow assurance community.