Estimation of the parameters of carbon dioxide injection into a saturated porous reservoir with heterogeneous permeability in the presence of hydrate formation

One of the effective methods of combating the increase in the concentration of carbon dioxide in the atmosphere is its sequestration in porous media in the solid gas hydrate form. The unique properties of gas hydrates, such as their high gas capacity, low permeability and natural stability, make them an attractive option for long-term disposal of carbon dioxide. In the context of considering the problem of organizing geological gas hydrate storages of carbon dioxide, a mathematical model is written down that allows a theoretical study of the process of carbon dioxide hydrate formation during its injection into a reservoir whose pores are initially saturated with methane and water. The proposed mathematical model takes into account zonal heterogeneity of a porous reservoir, the flow in it in the presence of phase transformations (hydrate formation and solubility of carbon dioxide in water) of the gas (СН 4 and/or СО 2 ) and liquid (water and dissolved CO 2 ) phases, heat transfer from the considered region of a reservoir to the surrounding rocks; the hydrate formation process is considered as an equilibrium phase transition. Calculation equations for the studied process are presented and numerical solutions of the problem are constructed, describing the distribution of parameters (temperature, pressure, phase saturations) in a reservoir. It has been shown by calculations that when CO 2 is injected into a reservoir, several characteristic zones can form in it, differing in the composition of the fluids saturating them. It has been demonstrated that it is necessary to take into account such factors as heat released during phase transitions, the Joule-Thomson effect, and heat exchange between the porous reservoir and its surrounding rocks when describing the temperature field in the reservoir formed when carbon dioxide is injected into it. The results of computational experiments are presented and analyzed when placing an injection well in a high- or low-permeability zone of a porous reservoir. The conducted numerical study showed that for the organization of effective gas hydrate storage of carbon dioxide, porous media with sufficiently high permeability values are required.