ВЛИЯНИЕ ДАВЛЕНИЯ НА ГРАНИЦАХ ПЛАСТА НА РЕЖИМЫ ОБРАЗОВАНИЯ ГИДРАТА СО2

The paper numerically examines the problem of formation of carbon dioxide gas hydrate (CG) in a methane-saturated reservoir of finite dimensions when exposed to weakly compressible CO2. A closed mathematical model has been developed that takes into account the thermodynamics of phase transitions, as well as the hydrodynamics of the flow in a porous medium. This allows us to correctly assess the mutual influence of thermal effects and pressure drops on the evolution of phase zones, as well as the distribution of the main parameters of the system, such as temperature and pressure. The model considered in the study takes into account that as a result of injection, a three-zone structure is formed in the formation. The system of basic equations consists of the laws of conservation of mass and energy, Darcy's law, as well as the equation of state, and is complemented by mass and heat balance conditions on the fronts of the phase transition, as well as initial and boundary conditions. The numerical solution is implemented by an implicit finite-difference method with catching fronts in the nodes of the spatial grid. Based on the results of a numerical study, it was found that the geometry of the regions forming in the formation is determined, in particular, by the pressure ratio at the external boundaries of the system. An increase in the injection rate (or corresponding pressure) leads to a decrease in the size of the zone containing the initial components (methane and water), in the extreme case, until it completely disappears. In this case, the process goes into the mode of direct direct substitution of HG methane with HG carbon dioxide without the formation of an intermediate two-phase region. In addition, a limit value of injection pressure is determined, which separates flow modes both with and without a two-phase methane-water zone. A dependence of this pressure on the value of the initial formation pressure p0 was obtained, which, as shown by calculations, increases with its increase. The results obtained can serve as the basis for the selection of technological parameters for injecting CO2 into hydrate-saturated formations, allowing to prevent unwanted gas breakthroughs or excessive hydrate saturation, which reduces reservoir permeability.