an oil / water emulsion , such as oil well production , is treated to recover its oil phase at pipe line specifications by passing the emulsion through an emulsion treater tank to an oil recovery zone in the tank . the emulsion flow path is through successive horizontal emulsion preheating , direct heating , post heating and settling zones of the tank while removing vapor from the top of the zones and water from the bottom of the zones . water and gas are thus removed from the emulsion in the preheating zones prior to direct heating of the emulsion in the direct heating zone to reduce heat loss and fouling of the emulsion heating means in the direct heating zone , and additional separation of the emulsion phases occurs in the post heating zone prior to final phase separation in the settling zone to improve the settling action . the heating and settling zones have a unique , horizontally folded , generally sinuous configuration which provides a maximum emulsion flow path length through the zones and hence maximum phase separation in the zones for a given tank size .