The purpose of drilling is also varied and may, for example, depend on environmental or performance considerations. Boreholes have in common that their depth is usually given in metres in Iceland, while their diameter is most often given in inches.
Icelandic names for boreholes. The list is compiled by ÍSOR's staff:
- A production well is drilled to obtain hot water or steam.
- A high-temperature well, also called a steam well, is a production well for reaching steam used in electricity generation.
- A sea well is a production well for pumping up geothermal seawater, which sometimes lies beneath fresh water.
- A cold-water well is a production well for obtaining drinking water or water for industry.
- A low-temperature well, also called a hot-water well, is a production well for obtaining hot water for a district heating system or other use.
- A percussion-drilled well. The word is derived from the type of drill rig used to drill the hole, the so-called percussion drill. In percussion drilling a heavy weight hanging from a wire rope is repeatedly dropped onto the bottom of the hole, gradually crushing the rock.
- An injection well, or reinjection well, is a hole of varying depth used to return water to the ground, either by pumping or by self-flow.
- A swallow well is a shallow hole for disposing of drilling fluid from the drill or from other operations into the ground.
- A drilling-fluid well is a special hole drilled down into water to obtain drilling fluid while drilling is under way.
- A disposal well is a shallow hole for returning water from a particular operation to the ground, for example from health baths.
- An exploration well, sometimes called a prospecting well, is a hole drilled for research purposes.
- A temperature-gradient well, or search well, is an exploration well drilled specifically to determine the geothermal gradient.
- A core hole is a sampling well drilled with a diamond bit (2-4")
- A directional well is a borehole that is drilled vertically at first but is then steered toward a particular target. This is done for environmental and performance reasons.
- An inclined well is a borehole that is not vertical, but drilled at an angle to seek out and intersect fractures.
- Groundwater well
- Monitoring well