A mixture of liquid hydrocarbons of different molecular weights.

Drilling mud with which crude oil has been unintentionally mixed. 

An oil field is a geographic area under which an oil reservoir lies. An oil field consists of a reservoir in a shape that will trap hydrocarbons and that is covered by an impermeable or sealing rock. 

An estimated measure of the total amount of oil contained in a reservoir. 

A strip-mining process involving the removal and subsequent processing of tar sand from shallow reservoirs containing heavy, viscous oil.

A mud in which the external phase is a product obtained from an oil, such as diesel oil or mineral oil.

A producing well with oil as its primary commercial product. Oil wells almost always produce some gas and frequently produce water. Most oil wells eventually produce mostly gas or water.