Injection of boiling liquid carbon dioxide into a stratum, accompanied by replacement of methane in hydrate by carbon dioxide

Abstract

On the basis of equations of the mechanics of multiphase media, a mathematical model of injection of carbon dioxide into a porous medium saturated with methane and its gas hydrate is constructed. The case is considered where on two moving frontal surfaces separating a porous stratum into three regions, boiling of carbon dioxide and replacement of methane by carbon dioxide gas in the initial gas hydrate take place. For the axially symmetric problem, self-similar solutions describing the pressure distribution in each of the three percolation regions are constructed. The dynamics of the two moving phase transition boundaries as a function of mass injection rate, the initial pressure, and permeability of the porous medium is investigated. It has been established that the extent of the region saturated with liquid carbon dioxide increases with growth of the injection rate and the initial pressure and lowering of the permeability, and the velocity of the front of methane replacement in the hydrate by carbon dioxide gas increases with increase in the injection rate and permeability and lowering of the initial pressure. It has been shown that boiling of carbon dioxide as a consequence of a corresponding decrease of its viscosity promotes acceleration of the front of methane replacement in the hydrate by carbon dioxide gas.