An Evaluation of Risk of Hydrate Formation at the Top of a Pipeline

Water condensation and/or hydrate formation at the top of pipelines are serious design/operation considerations in pipelines with stratified flow. Water condensation could result in top-of-the-line corrosion, particularly in sour-gas systems. Hydrate formation is believed to be another serious risk if the inhibitor in the aqueous phase cannot protect against hydrate formation at the top of the pipeline. In this paper, we report the results of some preliminary tests conducted in a new experimental setup constructed for investigating gas-hydrate risks in various operational scenarios (e.g., top of pipelines, deadlegs/jumpers, startups, shutdowns). The reported three series of tests conducted in the new experimental setup address hydrate-formation risks at the top of pipelines or deadlegs caused by temperature gradient, and the risk of hydrate formation in the gas phase in the presence of kinetic hydrate inhibitors (KHI) during pipeline cool down and startup. The results provide a better evaluation of the risks involved in various systems and provide guidelines for avoiding the associated problems.