Relief well

A relief well is a well drilled to intersect an oil or gas well

Oil well

An oil well is a general term for any boring through the earth's surface that is designed to find and acquire petroleum oil hydrocarbons. Usually some natural gas is produced along with the oil. A well that is designed to produce mainly or only gas may be termed a gas well.-History:The earliest...

 that has experienced a blowout

Blowout (well drilling)

A blowout is the uncontrolled release of crude oil and/or natural gas from an oil well or gas well after pressure control systems have failed....

. Specialized liquid, such as heavy (dense) drilling mud followed by cement, can then be pumped down the relief well in order to stop the flow from the reservoir in the damaged well.

The first use of a relief well was in Texas in the mid 1930s when one was drilled to pump water into an oil well that had cratered and caught on fire.