Features of Thermodynamic Conditions of the Formation and the Gas Composition in Natural Gas Hydrates Obtained in a Dispersed Medium with Aqueous Calcium Chloride

Results are given for a study of the thermodynamic conditions of the natural gas hydrates formation in a dispersed medium saturated with water, polymer solutions and their mixtures with aqueous CaCl2 as well as the gas composition in the resultant hydrates. Natural gas in all studied systems is found to form a mixture of hydrates of methane (first-stage hydrates with cubic structure I) and of natural gas (second-stage hydrates with cubic structure II). The equilibrium conditions of the second-stage hydrates formation are shifted toward higher temperatures by 0.5-1 degrees C relative to the calculated equilibrium curve, this is probably caused by the concentration of C2-C4 hydrocarbons in the hydrate. The presence of CaCl2 leads to a shift of the equilibrium conditions of the second-stage hydrates formation in comparison to the calculated curves toward higher temperatures and lower pressures with an increase of C2-C4 components in the hydrates. No specific effect was found for CaCl2 on the thermodynamic conditions of natural gas hydrate formation in a dispersed medium in a mixture with polymer solutions since these data obtained for the equilibrium conditions of the natural gas hydrates formation are identical with the data obtained upon hydrate formation in solutions of CaCl2 and water.