PDC Drill Bit Polycrystalline diamond compact drill bits have been long used in oil and gas drilling, and only recently have they been used in geothermal drilling. The PDC cutters are known...

Peak Load Generation The amount of power required to maintain an electric grid for short-lived periods (e.g., morning, late afternoon and evening) in response to high demand. Thermal power...

Perforation The process of punching holes through the steel casing liner in a well in order to inject fluid into or produce fluid out of the reservoir rock. Perforations are achieved...

Piezometric Surface The imaginary surface to which groundwater rises under hydrostatic pressure in wells or springs.

Proppant Sand-sized solid grains that are injected in a fluid suspension and used to hold open stimulated fractures in a geothermal reservoir.

Propylitic Alteration A term borrowed from studies of hydrothermal ore deposits that refers to an assemblage of secondary hydrothermal minerals which forms in igneous rocks. This assemblage...

Rhyolite Light colored fined grained volcanic rock composed of glass, quartz, K-feldspar and plagioclase, with relatively high silica (69-77 wt %). The composition reflects partial melting...

Scale Refers to deposition of minerals (e.g., calcite, silica, anhydrite, clays) in the well and reservoir that reduce permeability and block fluid channels.

Seismometer An instrument that records ground movement most often caused by earthquakes, volcanic eruptions and quarry or mine blasts. Short period seismometers detect seismic events that...

Shear Fracture A pre-existing joint or fracture that accommodates shear displacement due to frictional slippage, wherein the rough surfaces on the fracture surface create permeability due...

Silica Sinter Horizontally banded deposit of amorphous silica that precipitates around neutral pH hot springs that are close to boiling temperature.

Slickwater Water that is injected during reservoir stimulation. It is modified with low concentrations of chemical additives, including polyacrylamide, that reduce friction and enhance...