A borehole is a narrow, deep hole drilled into the ground for the purpose of extracting water, oil, gas, or minerals, or for scientific investigation. Boreholes are critical in hydrogeology for accessing groundwater and in the oil and gas industry for exploration and production. They also provide valuable data on subsurface geology, including rock strata, porosity, and fluid content.
Reference: Driscoll, F. G. (1986). Groundwater and Wells. Johnson Filtration Systems Inc.