Oilwell

An oil well, sometimes written as oilwell, is a bored or drilled hole beneath the surface of the earth designed to bring petroleum to the surface. Most oil wells are drilled to intersect a hydrocarbon-bearing reservoir rock and are completed with casing and tubing to provide a conduit for fluids.

Construction and operation: Drilling uses a drill bit attached to a drill string. Drilling fluid (mud) stabilizes the borehole, cools the bit, and carries cuttings to the surface. Once the well reaches the target formation, it is cased with steel pipe and cemented to prevent collapse and fluid migration. Production tubing is installed to convey oil and gas to the surface, where equipment such as a Christmas tree controls flow. A blowout preventer provides a last line of defense against uncontrolled release.

Offshore wells may be drilled from ships or fixed or floating platforms and often involve subsea trees and risers. Onshore wells are drilled from land rigs.

Production: In primary recovery, natural reservoir pressure and artificial lift (pumps) bring hydrocarbons to the surface. Produced fluids are separated into oil, gas, and water and treated for market use. Wells may be stimulated with hydraulic fracturing or other methods to increase output.

Uses and safety: Oil wells are central to petroleum supply chains but pose risks including spills, subsidence, and blowouts. Regulation, monitoring, and safety systems such as BOPs are standard components of modern operations.