When we refer to hydrocarbon measurement in the production segment of the petroleum industry, we're normally referring to the measurement of one or more fluids. Those fluids are natural gas, natural gas liquids (NGLs), condensate, and crude oil. All of these fluids are primarily (or completely) composed of molecules containing a carbon backbone with hydrogen atoms attached...hence the name hydrocarbon.
Within a reservoir, hydrocarbons exist as a gas, as a liquid, as both gas and liquid, or as a dense phase (supercritical) fluid. Hydrocarbons produced to the surface normally are in two separate phases – gas and liquid. The gas produced to the surface is called natural gas. The liquid produced to the surface is called crude oil if it existed as a liquid in the formation, and wellhead condensate if it existed as a single dense phase in the formation. Condensate which results from changes in temperature and pressure once the fluid reaches the surface is referred to as pipeline condensate. If a gas stream is cooled by artificial means to below ambient temperature, any liquid hydrocarbons produced are NGLs.
Because of the varying nature of these produced fluids, optimal measurement requires the use of different types of primary measurement elements; e.g., orifice, turbine, coriolis, ultrasonic, etc.To determine the proper selection and configuration of measurement equipment to maximize accuracy, it's highly recommended that you consult with a hydrocarbon measurement specialist.
"A wise man will make more opportunities than he finds."
~ Francis Bacon, British author and statesman