Research into thermobaric processes of methane gas hydrates formation

Abstract

Based on experimental studies, the paper deals with the dynamics of the methane gas hydrates formation, influenced by the organized media, such as surface-active agents (surfactants, SAA), namely, dibutylphenol treated with ethylene oxide, as well as ethoxylated alcohols. The stalagmometric method with automatic photoelectronic drops counting, a conductometric method, a Wheatstone bridge, potentiometer, as well as laboratory setup with varying thermobaric parameters of the hydrate formation process are used. The molecular dynamics method and the Monte Carlo method are applied to the process of methane gas hydrates formation. New experimental dependences of the gas hydrates formation have been determined on thermobaric conditions with and without of organized media. It has been set that under normal conditions of hydrate formation, the hydrate formation thermobaric curve consists of two identical dependences, which is caused by formation of the KS-II structure hydrates with different degrees of filling the crystal lattice cavities: from 275.0 to 279.2 K - small cavities, and above - larger ones. When applying a surfactant, water structuring with formation of immediately large cavities in the gas hydrate crystal lattice are observed, due to which the methane content in the hydrate increases. It has been revealed that the gas hydrates formation process occurs stepwise, by replacing old bondsb with new ones with a gradual change in the coordination number of reacting surface atoms. It has been found that surface clustering in the presence of organized media facilitates the gas hydrate formation process by means of micellar catalysis. The dependences have been determined of the gaseous methane amount contained in the cluster upon the temperature in the dissociation of obtained gas hydrate samples. The amount of methane in a unit volume of gas hydrate has been determined: without adding the surfactant at a maximum pressure of 18 MPa - 120 m3; by adding the surfactant with the same thermobaric parameters - 160 m3.