DECOMPOSITION OF METHANE GAS HYDRATE DURING CARBON DIOXIDE INJECTION INTO A NEGATIVE-TEMPERATURE BED

The article presents a mathematical model of the injection of gaseous carbon dioxide into a porous bed that contains methane and its gas hydrate at a negative (Celsius scale) temperature, accompanied by its decomposition into a gas and ice. It is shown that, depending on the injected gas parameters, the formation of the carbon dioxide hydrate can occur in four modes. The fi rst mode is characterized by decomposition of CH₄ hydrate into ice and methane and by formation of CO₂ hydrate from carbon dioxide and ice. The second mode involves the decomposition of CH₄ hydrate into ice and methane, the melting of ice, and the formation of CO₂ hydrate from carbon dioxide and melt water. Moreover, at high values of pressure and temperature of injection, the existence of a mode is possible when methane hydrate decomposes into water and gas, and the formation of carbon dioxide hydrate occurs from CO₂ and water. The mode with the replacement of methane in the hydrate by carbon dioxide is considered as the limiting case of the fi rst mode, when the region containing methane and ice degenerates into a frontal surface of infi nitesimal thickness. Self-similar solutions have been constructed, and critical conditions separating the four modes of the course of the process have been obtained.
   
Author:  M. K. Khasanov and M. V. Stolpovskii
Keywords:  gas hydrate, fi ltration, porous medium, heat and mass transfer, phase transitions, methane, carbon dioxide, ice
Page:  213