Conduction For geothermal applications, this refers to heat transfer in solids where thermal energy flows via microscopic-submicroscopic collisions of particles, which at a macro level is...

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.

Convection Refers to heat transfer by fluid circulation in permeable rocks where thermal energy is transported with the flow of hot fluid (water or steam).

Cooling Tower Plant equipment that is used to dissipate heat into air rather than into a river. Cooling is induced in two different ways. For binary plants, dry cooling towers use fans to...

Cyclone Separator A large cylindrical vessel attached to two-phase production pipelines in geothermal fields that is used to separate dry steam from a fast-moving two-phase fluid. Steam...

DAS Distributed Acoustic Sensor. Involves the deployment of fiber optic cable on the surface or in a well, and the detection of small variations in the refractive index of the fiber based...

Directional Drilling The practice of steering the trajectory of a well during drilling from vertical to a deviated angle, including horizontal drilling used for oil and gas production from...

Drill Bit A tool that is placed on the end of a string of pipe to drill a well. Rotary drill bits are commonly used in oil and gas and geothermal drilling. Coring bits are used to obtain...

Drill Core Intact cylindrical shaped sample of rock obtained during drilling with a special coring bit. Although commonly narrow in diameter (e.g., 1-4" or 25-100 mm), it preserves a...

DFIT Diagnostic Fracture Injection Test. A subsurface well test in which pressure is monitored as a small volume of fluid is injected into a reservoir to develop a hydraulic fracture....

Drill Cuttings Small chips of rocks (e.g., <1/8 inch or <3 mm) obtained during drilling with a rotary bit that are continuously returned to the surface by the circulation of mud....