Instabilities during Liquid Migration into Superheated Hydrothermal Systems

Hydrothermal systems typically consist of hot permeable rock which contains either liquid or liquid and saturated steam within the voids. These systems vent fluids at the surface through hot springs, fumaroles, mud pools, steaming ground and geysers. They are simultaneously recharged as meteoric water percolates through the surrounding rock or through the active injection of water at various geothermal reservoirs. In a number of geothermal reservoirs from which significant amounts of hot fluid have been extracted and passed through turbines, superheated regions of vapour have developed. As liquid migrates through a superheated region of a hydrothermal system, some of the liquid vaporizes at a migrating liquid-vapour interface. Using simple physical arguments, and analogue laboratory experiments we show that, under the influence of gravity, the liquidvapour interface may become unstable and break up into fingers.