Adularia Hydrothermal potassium bearing feldspar that forms in volcanic hosted geothermal reservoirs and is a favorable indicator of boiling and permeable conditions.
Geothermal Glossary
Word of the Week – Aquifer
Aquifer Porous and permeable rock unit or unconsolidated layer in the subsurface in which all the pores and voids are filled with water. Water supply for wells comes from aquifers.
Word of the Week – Basalt
Basalt Dark grey fine grained volcanic rock composed of plagioclase, pyroxene and olivine, with relatively low silica (45-52 wt %). The composition reflects an upper mantle origin. Basalt...
Word of the Week – BHA
BHA Refers to Bottom Hole Assembly, which is the system of tools at the bottom of the drill string that is used for drilling directional wells. The BHA includes the drill bit, mud motor,...
Word of the Week – Binary Cycle Power Plant
Binary Cycle Power Plant A power plant in which the produced geothermal fluid passes through a heat exchanger and heats a low boiling point liquid, commonly an organic compound such as...
Word of the Week – Breccia
Breccia Angular to sub-angular fragments of broken rock that are cemented together that are highly permeable and form on the surface due to sedimentary or igneous processes or in fault...
Word of the Week – Brine
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...
Word of the Week – Cap Rock
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...
Word of the Week – Casing Shoe
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...
Word of the Week – Cement Bond Log
Cement Bond Log A geophysical well log that is obtained using a sonic-type tool on a wireline. The result helps to confirm the integrity of the hardened cement that was injected to form a...
Word of the Week – Chemical Geothermometer
Chemical Geothermometer A temperature that is calculated based on the chemical composition of a hydrothermal fluid and involves knowing a ratio (e.g., Na/K) or knowing the absolute...
Word of the Week – Chlorite
Chlorite A micaceous mineral that is commonly green-colored, composed of iron and/or magnesium, and forms due to hydrothermal alteration of amphiboles, pyroxenes, and feldspars.