Non-associated gas, also called non-associated petroleum gas, dry gas, free gas, and well gas, is natural gas that is found and produced from underground reservoirs that do not contain significant quantities of crude oil. These are typically dedicated gas reservoirs or gas fields where the hydrocarbons exist primarily or entirely in the gaseous phase under reservoir conditions, without being dissolved in or in direct contact with substantial volumes of liquid petroleum.
By contrast, associated gas is natural gas that occurs in conjunction with crude oil reservoirs, either as free gas in a gas cap above the oil column or as gas dissolved in the oil under reservoir pressure and temperature. Non-associated gas is extracted from wells drilled specifically into gas-bearing formations, where little to no crude oil is present in the reservoir. It may still contain natural gas liquids such as condensate in some cases, but the defining characteristic is the absence of meaningful crude oil volumes in the same accumulation. Production from these reservoirs tends to be simpler at the surface because there is no requirement for extensive oil-gas separation equipment that is routinely needed for associated gas streams.
Non-associated gas reservoirs are commonly found in conventional geologic settings where the source rock, migration path, and trap conditions favored the accumulation of primarily gaseous hydrocarbons without accompanying liquid petroleum.
