Drilling rig is a building with equipment to drill into the underground reservoir for water, oil, or gas, or mineral deposits underground. Drilling rig could be above ground (on shore) or on the sea / offshore (off shore) depends for its future use. Although the offshore rig can drill down to the bottom of the sea to search for minerals, technology and economics of undersea mines can not be done commercially. Therefore, the term “rig” refers to the collection of equipment used to drill on the surface of the Earth’s crust to take samples of oil, water, or mineral.

Drilling rigs of oil and gas can be used to define the geological properties of the reservoir and also to create holes that allow retrieval content of an oil or gas from the reservoir.

Drilling rig can be sized:

- Small and portable, such as those used in mineral exploration drilling

- Large, capable of drilling up to thousands of meters into the Earth’s crust. Large mud pumps used for circulating drilling mud through the drill bit and casing (sheath), to cool at the same time taking “the land of the cut” for wells drilled.

Pulley on the rig can lift hundreds of tons of pipe. Other tools can encourage acid or sand into reservoirs to take samples and mineral oils; accommodation for the crew that could amount to hundreds. Offshore rig can operate hundreds to thousands of kilometers from the beach.