Before it became the world’s largest geothermal power-producing site, The Geysers was known as the “Gates to Hades,” drawing visitors with its healing waters, steam vents, and wild legends.

Calculated thermal energy stored in a volume of hot rock. It is calculated using the rock volume, porosity, rock density, specific heat of rock, and the difference between the reservoir temperature and the background temperature given by the geothermal gradient outside the resource area.
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 bond between well casing and the adjacent rock formation.
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 concentration of a species (e.g., SiO2). Temperature is computed using a simple...
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.