borehole

A borehole is a deep, narrow shaft drilled into the ground to access subsurface resources or to collect samples. Boreholes range from a few meters to several kilometers in depth and may be drilled for water supply, mineral exploration, waste disposal, geothermal energy, or monitoring.

Construction and equipment: Boreholes are formed with drill rigs that advance a drill string and bit. Drilling fluids or air are used to cool the bit, carry cuttings to the surface, and stabilize the hole. As drilling progresses, steel or plastic casings are inserted to prevent collapse and isolate aquifers; the annulus between casing and borehole may be cemented to seal off unwanted water paths. Screens or slotted liners may be installed at the bottom to allow fluid entry while filtering solids.

Applications: Groundwater boreholes supply drinking water and irrigation; in hydrocarbon exploration, boreholes (wells) locate reservoirs and allow production or injection. Geothermal systems use boreholes to circulate working fluids for heat extraction or storage. Boreholes are also used for environmental sampling, geotechnical testing, and monitoring groundwater quality or subsidence.

Design and regulation: The depth and diameter depend on purpose and geology. Proper design includes casing, grout, borehole sealing, and abandonment plans. Drilling activities require permits, environmental controls, and adherence to safety standards. Decommissioning involves removing equipment and sealing the borehole to prevent contamination or instability.