On the Riemann problem for supercritical CO2 injection into an aquifer

The classical self-similar Riemann problem is considered for the process of supercritical CO2 injection into a permeable reservoir saturated by water. In an asymptotic approximation, the solution of the problem is constructed using the equations for nonisothermal multiphase flows in a porous medium. The qualitatively different solutions are determined depending on initial reservoir temperature and injection parameters. The wave pattern propagating from CO2 injection well in the aquifer consists of up to six nonlinear rarefaction (simple) waves and shock waves (phase discontinuities). The influence of the pressure increase around CO2 injection well on the wave pattern is investigated. The accuracy of the asymptotic solution is evaluated by its comparison with the results of direct numerical simulations.