Abstract: A method and apparatus for separating a wellhead fluid mixture containing oil and gas phases obtained from hydrocarbon production systems into its constituent parts employs a pressure vessel having an inlet for entry of the wellhead fluids mixture and an outlet for exit of a separated gas referred to as export gas. A primary centrifugal separator is provided in the pressure vessel for centrifugally separating a first portion of the oil from the wellhead fluids mixture to produce a wet gas containing some remaining oil. A second centrifugal separator is also provided in the vessel and performs a second centrifugal separation operation on the wet gas to remove substantially all of the remaining oil from the wet gas to produce the export gas which is conveyed out of the pressure vessel. The oil and remaining oil separated from the wellhead fluids mixture is conveyed from the pressure vessel via another outlet.