INJECTION OF SALTY WATER INTO HOT ROCK, SATURATED WITH SUPERHEATED VAPOUR

We consider salty water injection into depleted geothermal reservoir saturated with superheated vapour. If the water temperature and pressure reach a boiling point then liquid evaporates and boiling front migrates away from the injection well. Water vaporization increases salt concentration in the liquid zone and excess salt may precipitate at the vaporization front. Behind the vaporization front salt in solid state occupies some part of the volume of the porous space and an extended domain arises in which solid salt coexists with the saturated solution. As initial salt concentration of the salty water is less than the solubility value, then the dissolution front develops between the vaporization front and injection well. The dissolution front also migrates in the same direction as the vaporization front. A family of self-similar solutions that describes salty water boiling, salt precipitation and dissolution of solid salt was derived. It was found that this family of self-similar solutions is multi-valued. At some critical values of parameters these solutions converge. Beyond the critical point, there is no similarity solution and this behavior of the solutions means that the rock becomes fully sealed through precipitation at the vaporization front