Conversion of CH4 Hydrate to CO2 Hydrate during Boiling of Liquid Carbon Dioxide in a Depleted Gas Field

Abstract The problem of methane hydrate conversion into carbon dioxide hydrate during injection and boiling of liquid carbon dioxide in a formation containing methane and its hydrate is studied. Estimates show that the substitution reaction at the contact of methane hydrate and liquid carbon dioxide is impossible due to the low enthalpy of the liquid phase CO 2 . A mathematical model of the conversion is proposed, which assumes preliminary gasification of carbon dioxide. In this case, the formulated model contains two unknown moving boundaries of phase transitions separating three regions of different states of the components. Similarity solution is found, reducing the problem to a numerical study of a system of seven transcendental equations. The results of calculations of characteristic regimes of the process under consideration are presented. It is shown that with a decrease in the initial temperature of the reservoir or hydrate saturation, methane substitution by carbon dioxide does not occur.