Gas hydrate growth kinetics is largely ascribed to three main controlling mechanisms: intrinsic kinetics, mass transfer, and heat transfer. In this work, gas hydrate growth has been analyzed on the basis of heat transfer during stirred laboratory cell experiments at a constant pressure using pure methane as the hydrate former (structure I). For this, a heat balance model has been developed. The hydrate growth rate was related to measured gas inflow to maintain pressure in the cell constant. Produced heat from hydrate formation is estimated using the heat balance model, and then the amount of hydrate formed is estimated through the enthalpy of methane hydrate formation. The simulated results from the model give a fair representation of the main growth parameters, gas flow/hydrate growth rate, and cumulative growth/gas consumption. Heat transfer through the hydrate slurry changes with increasing the hydrate content. The analysis suggests inclusion of the transient nature of the heattransfer coefficient for accurate prediction of hydrate growth when modeling based on heat transfer. Taking the transient effect into consideration, good correlation between estimates and measurements were obtained.

Gas hydrate growth kinetics was studied at a pressure of 90 bars to investigate the effect of temperature, initial water content, stirring rate, and reactor size in stirred semi-batch autoclave reactors. The mixing energy during hydrate growth was estimated by logging the power consumed. The theoretical model by Garcia-Ochoa and Gomez for estimation of the mass transfer parameters in stirred tanks has been used to evaluate the dispersion parameters of the system. The mean bubble size, impeller power input per unit volume, and impeller Reynold's number/tip velocity were used for analyzing observed trends from the gas hydrate growth data. The growth behavior was analyzed based on the gas consumption and the growth rate per unit initial water content. The results showed that the growth rate strongly depended on the flow pattern in the cell, the gas-liquid mass transfer characteristics, and the mixing efficiency from stirring. Scale-up effects indicate that maintaining the growth rate per unit volume of reactants upon scale-up with geometric similarity does not depend only on gas dispersion in the liquid phase but may rather be a function of the specific thermal conductance, and heat and mass transfer limitations created by the limit to the degree of the liquid phase dispersion is batched and semi-batched stirred tank reactors.

Gas hydrates are the foremost flow assurance issue in deep water operations. Since heat transfer is a limiting factor in gas hydrate formation processes, a better understanding of its relation to hydrate formation is important. This work presents findings from experimental study of the effect of gas hydrate content on heat transfer through a cylindrical wall. The experiments were carried out at temperature conditions similar to those encountered in flowlines in deep water conditions. Experiments were conducted on methane hydrate, Tetrahydrofuran hydrate, and ethylene oxide hydrate respectively in stirred cylindrical high pressure autoclave cells. Methane hydrate was formed at 90 bars (pressure), and 8°C, followed by a cooling/heating cycle in the range of 8°C → 4°C → 8°C. Tetrahydrofuran (THF) and ethylene oxide (EO) hydrates were formed at atmospheric pressure and system temperature of 1°C in contact with atmospheric air. This was followed by a heating/cooling cycle within the range of 1°C → 4°C → 1°C, since the hydrate equilibrium temperature of THF hydrate is 4.98°C in contact with air at atmospheric pressure. The experimental conditions of the latter hydrate formers were more controlled, given that both THF and EO are miscible with water. We found in all cases a general trend of decreasing heat transfer coefficient of the cell content with increasing concentration of hydrate in the cell, indicating that hydrate formation creates a heat transfer barrier. The hydrate equilibrium temperature seemed to change with a change in the stoichiometric concentration of THF and EO. While the methane hydrate cooling/heating cycles were performed under quiescent conditions, the effect of stirring was investigated for the latter hydrate formers.

The thermodynamics and kinetics of clathrate hydrate formation processes are topics of high scientific interest, especially in the petroleum industry. Researchers have made efforts at understanding the underlying processes that explicate the macroscopic observations from experiments and other research methods of gas hydrate formation. To achieve this, they have employed theories founded upon force related intermolecular interactions. Some of the theories and concepts employed include hydrogen bonding, the Leonard Jones force principle, and steric interactions. This paper gives a brief review of how these intermolecular interaction principles have been understood, and used as tools, in explaining the inaccessible microscopic processes, that characterize clathrate hydrate formation. It touches upon nucleation, growth, and inhibition processes.