Chemical composition of deep hydrothermal fluids in the Ribeira Grande geothermal field (São Miguel, Azores)

The geothermal wells exploit three different aquifers, the lower of which is liquid and slightly colder than the upper ones. The intermediate is a two-phase aquifer with a steam fraction up to 0.081. The upper aquifer is probably of steam phase. The main differences between the aquifers are the temperature and boiling; both enthalpy and flashing increase as aquifer depth decreases.