A secondary mineral phase whose stability is defined by a lower and sometimes an upper temperature threshold. Common mineral geothermometers comprise clays, zeolites and epidote, with crystal structures that contain a hydroxyl (OH–) or water (H2O) molecule. The temperature ranges of mineral geothermometers are calibrated from investigations of a large number of drilled geothermal resources where mineral zonations and temperature gradients have been determined.
Brine In producing geothermal fields, this term refers to the hot water that is produced from wells. It is rarely as salty as implied. Instead, the salinities of most natural hot waters are commonly less than seawater, but they contain a wide range of rock-forming...
Cap Rock A poorly permeable or impermeable layer that overlies a geothermal reservoir. The term is borrowed from the oil industry and was once considered an essential feature of a producing geothermal resource in confining the flow and pressure of hot water....
Casing Shoe In geothermal wells, this is the bottom of the cemented casing string. Below the casing shoe, the well may be unprotected and open to the surrounding rock or lined with a slotted liner. The depth of the casing shoe generally coincides with the top of the...
