Numerical solution of the problem of CO2 hydrate generation in a porous medium initially saturated with methane hydrate

Abstract

The relevance of the discussed issue is caused by theoretical investigation of gas hydrate generation in porous medium with regard to production, transportation and conservation of hydrocarbon raw material. The main aim of the study is, to consider in axisymmetric formulation the replacement of methane hydrate, initially contained in a porous formation, by carbon dioxide hydrate, on the basis of the mathematical model, and to reveal the regularities of dynamics of gas hydrate generation in porous media of finite extent while injecting gas through its left boundary, with the other boundary being open to gas flow. The methods used in the study: multiphase system mechanics together with computational method of Stefenґs generalized problem. Results of the study. The paper introduces the mathematical model and numerical calculation of carbon dioxide injection into porous formation, initially saturated with methane and its hydrate in the axisymmetric formulation. The authors have used the numerical method of tracking the front node in the spatial grid to solve the problem of finding pressure and temperature distribution, and the boundary of phase transmission. The acquired numerical solutions were compared with analytical self-similar solutions. It was ascertained that gas hydrate displacement is followed by little pressure drop and reservoir temperature increase. It was shown that the temperature at the phase border depends on injected gas pressure. If the pressure is high it tends toward its cutoff value which depends on initial gas hydrate saturation in the reservoir. The authors studied as well the relation of methane total displacement from the reservoir as a function of its permeability and injected gas pressure.

Keywords

• gas hydrates
• porous medium
• temperature increase
• formation and decomposition of hydrates
• Stefanґs problem
• phase transitions