The first step in processing the well stream is to separate the crude oil, natural gas and water phases into separate streams. Oil and gas fields utilize two-phase gas/oil and gas/condensate separators as well as three-phase gas/oil/water separators. Units are classified according to horizontal or vertical configuration, operating pressure, turbulent or laminar flow, and test or production separation.
Interface level measurement will actuate a valve to adjust vessel level. An emulsion layer along the oil/water interface can contaminate the oil with water or the water with oil. Foaming along the gas/liquid interface, if entrained, can cause liquid carryover or gas blow-by.