Abstract: A mobile separator system for oil and gas well production fluids consisting of a sled supporting a horizontal three phase separator vessel having an upright vessel or blowcase, with an upper section open to a lower section through a check valve, and a vertical two phase vessel mounted beside each other and seated within the horizontal vessel. A direct fired heater in the horizontal vessel provides the required heating for all three vessels. Production fluids tangentially enter the upper section of the upright vessel with gas rising and the fluid descending through a check valve to the lower section and then transferred into the horizontal vessel. The rising gas outlet is connected to the suction of a compressor and discharged under pressure to the intake of the vertical vessel. Separated gas from the horizontal vessel also is directed to the intake of the compressor. Oil and water separated in the horizontal vessel are transferred into storage or pipelines.