as the oil is geothermally heated vapors rise through duct 16 and heat the downwardly flowing oil in annulus 24 and proceed to the surface for further treatment such as fractionation non boiling residue is removed through pipe 30 by means of pump 31 if the temperature in the unit 18 is high suitably above 700 u00b0 f some thermal cracking may occur in the geothermal refining unit of fig2 distillation of the crude oil 59 is conducted by means of a pipe still 32 the well head 42 contains ports for sealingly receiving a water conduit 34 crude conduit 36 and vapor stack 47 communicating with outlet 40 the outlet 35 of the water conduit extends into a steam boiler section 37 the steam generated by the geothermal heat from zone 13 enters the pipe still and heats the body of oil 59 to vaporize fractions having a boiling point below the temperature in the zone 13 the still 32 may have a steam outlet 44 the steam injected into the oil 59 can extract some miscible components by steam distillation and serves to entrain higher boiling residue components the generated vapors and the steam and entrained liquid rise through the annulus 38 through outlet 40 and stack 47 into separator 46 from which steam and water are removed and then into fractionator condenser 48 referring now to fig3 generation of steam by injecting water from the surface may not be required if the bottom portion of well 10 containing the distillation unit.