Comparison of Laboratory Results on Hydrate Induction Rates in a THF Rig, High‐Pressure Rocking Cell, Miniloop, and Large Flowloop

Abstract

This paper compares experimental data obtained on three high‐pressure devices and one atmospheric apparatus that measure hydrate formation onset and dissociation temperatures. The high‐pressure devices are rocking sapphire tubes, a 0.5‐inch diameter miniloop, and a 4‐inch diameter flowloop. High‐pressure miniloop results are compared to atmospheric pressure, tetrahydrofuran (THF) rig results in which chemically similar inhibitors ranked in different order. Although high‐pressure, stirred tank apparatus is considered by many to be effective in obtaining data of this kind, this paper does not include any stirred‐tank data. Many kinetics experiments are insensitive to the high‐pressure apparatus used. However, results of kinetic experiments obtained in different types of screening apparatus may not agree if the methods of hydrate detection are different. An example of a gas/condensate/brine system that would be difficult to characterize in a rocking‐cell or stirred‐tank apparatus is discussed.

Kinetic Hydrate Inhibitor Studies for Gas Hydrate Systems: A Review of Experimental Equipment and Test Methods

“…or larger. For example, Reed et al 104 and Talley et al 105 from Exxon Upstream Research Company constructed stainless steel hydrate flow loops with 1/2 and 4 in. i.d.…”

“…6 10−15 Reed et al;104 Talley et al;105 Klomp and co-workers;83,111 Peytavy et al;116 Turner et al 194 mini/micro flow loop 100−1000 ∼10 Talaghat and co-workers; 195,196 Cook et al…”

Kinetic Hydrate Inhibitors Performance

“…Miniloop and 4-in flowloop results (reported in Talley, Mitchell, and Oelfke, 1999) are only representative of turbulent, flowing tests. If the flow regime in any of the loops is stratified flow or wavy flow, the onset subcoolings will be unpredictably different, usually trending toward less subcooling.…”

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A study (Talley, Mitchell, and Oelfke, 1999) was conducted to determine the hydrate onset subcooling of several KHIs of differing chemical structure in a 0.5-in miniloop, ½-in rocking cells and a 4-in flowloop.The tests were all carried out at the same cooling rate of 6 F per hour. The KHI concentrations were all 0.5 weight % active polymer.

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“…A study (Talley, Mitchell, and Oelfke, 1999) was conducted to determine the hydrate onset subcooling of several KHIs of differing chemical structure in a 0.5-in miniloop, ½-in rocking cells and a 4-in flowloop.…”