A wet gas is any gas with a small amount of liquid present.[1] The term "wet gas" has been used to describe a range of conditions varying from a humid gas which is gas saturated with liquid vapour to a multiphase flow with a 90% volume of gas. There has been some debate as to its actual definition,[2] and there is currently no fully defined quantitative definition of a wet gas flow that is universally accepted.
Wet gas is a particularly important concept in the field of flow measurement, as the varying densities of the constituent material present a significant problem.
A typical example of wet gas flows are in the production of natural gas in the oil and gas industry. Natural gas is a mixture of hydrocarbon compounds with quantities of various non-hydrocarbons. This exists in either a gaseous or liquid phase or in solution with crude oil in porous rock formations. The number of hydrocarbons present in the liquid phase of the wet gas extracted depends on the reservoir temperature and pressure conditions, which change over time as the gas and liquid are removed. Changes in the liquid and gas content also occur when a wet gas is transported from a reservoir at high temperature and pressure to the surface where it experiences a lower temperature and pressure. The presence and changeability of this wet gas can cause problems and errors in the ability to accurately measure the gas phase flowrate.
It is important to be able to measure these wet gas flows accurately to quantify production from individual wells and to maximise the use of equipment and resources which will assist with the reduction of costs.