Hydrate Induction Time with Temperature Steps: A Novel Method for the Determination of Kinetic Parameters

Abstract

Gas hydrate formation usually occurs with a certain delay after a system composed of water and a hydrate-forming gas is put under suitable thermodynamic conditions of pressure and temperature. This delay period is called the “induction time”, and because of its large variability within a single experimental setting, hydrate formation is often referred to as a stochastic process. The evaluation of induction times, together with other measurements, is taken as an indication for the efficiency of hydrate inhibitors, and they are usually carried out by simply putting the experimental system under chosen P/T conditions and then waiting for the hydrate to form and measuring the time elapsed. In this paper, we present an improved procedure by which the variability of hydrate induction times can be remarkably reduced, while keeping a good correlation of measured induction times with the respective temperatures as obtained by a constant cooling method. In this procedure, temperatures are lowered by 0.5 °C after each time span of 3 h with no hydrate formation. Induction times obtained in this way show a remarkably lower coefficient of variation as compared to a standard induction time measurement.

A Simple and Direct Route to High-Performance Acrylamido-Based Kinetic Gas Hydrate Inhibitors from Poly(acrylic acid)

“…23−26 This allows the reader to compare the results to many other classes of additives tested in our laboratories. A study recently showed that the slow ramped cooling experiments gave good reproducibility and recommended lowering the temperature by 0.5 °C every 3 h. 27 However, KHI experiments at this rate could take several days for good additives. We believe the cooling rate (1 °C/h) in our method is a good enough compromise to screen new additives.…”

“…We used our standard slow constant-cooling (SCC) test method, which we have used in many previous studies with this equipment. − This allows the reader to compare the results to many other classes of additives tested in our laboratories. A study recently showed that the slow ramped cooling experiments gave good reproducibility and recommended lowering the temperature by 0.5 °C every 3 h . However, KHI experiments at this rate could take several days for good additives.…”

Review of Kinetic Hydrate Inhibitors Based on Cyclic Amides and Effect of Various Synergists

“…A constant cooling rate procedure , was followed in all of the experiments, which allowed the system to gradually move from the hydrate unstable region to the hydrate stable region after having the system temperature fall below the three-phase equilibrium temperature (20.1 °C). Hydrate formation was noticed at a temperature when there was a sudden pressure drop in the system as the gas got trapped inside the hydrate cages forming hydrates.…”

Fully Coupled Numerical Model and Its Application in Natural Gas Hydrate Reservoir

“…Yin et al , extracted key intrinsic kinetic parameters that can be directly used in the hydrate dissociation model and formed a spatially homogeneous hydrate bearing sediment by investigating the kinetic behavior of MH formation in sandy medium. Canale et al raised a novel method, which is evaluating hydrate induction time, to determine kinetic parameters. Based on the production data of the Shenhu area, South China Sea, Sun et al established a two-dimensional model to study the effects of burden permeability on the depressurization process.…”