Hydrocarbon producers, or oil companies, may choose to drill into underground formations they know only hold light hydrocarbons which are commonly referred to as natural gas wells. They include methane, which is what is sold by natural gas utility companies, and other natural gas liquids (NGLs). NGLs are ethane, propane, butanes and natural gasoline.
Oil companies also drill for heavy hydrocarbons. The wells that produce heavy hydrocarbons are known as oil wells. But oil wells almost always have some light hydrocarbons with them that include methane and all the NGLs.