As production moves towards harsher operating conditions, the conventional strategy of complete hydrate avoidance may not be economically viable. In the past two decades, the development of new technologies, such as low-dosage hydrate inhibitors and active pipeline heating, have enabled new management strategies where limited quantities of hydrate may be allowed to form without endangering the flowline. While this strategy may result in cost savings for long-distance tiebacks, its success hinges on accurate predictive capabilities for hydrate formation and transportability.
In this extended abstract, the authors present a new freeware Hydrate Flow Assurance Simulation Tool (HyFAST), where the risk of hydrate plug formation can be directly predicted in subsea flowlines for use in flow assurance concept selection and process engineering. This tool is based on deterministic hydrate plug formation stages—including phase dispersion, hydrate growth rate and particle agglomeration—developed in the international engineering community in the past 20 years.
HyFAST expands this conventional paradigm by introducing a new probabilistic engine to account for dynamic hydrate nucleation. This expanded capability enables flow-assurance engineers to directly quantify the risk of plug formation as a function of:
flowline length;
insulation thickness;
produced water concentration;
the amount of thermodynamic inhibitor injected; and,
the amount of low-dosage hydrate inhibitor injected.
An open discussion of all models and assumptions underlying the tool is presented, and the use of this tool to quantify hydrate plug formation risk is demonstrated.
A study of hydrate plug formation in a subsea natural gas pipeline using a novel high-pressure flow loop