No oil is injected in the compression chamber: no lubrication.
As the rotors neither come into contact with each other nor with the compressor housing, no particular lubrication is required in the compression chamber.
Oil is used tor lubrication of bearings and gears: Compleate separation of compression chamber and bearings / gears by using seal rings on the shafts.
Separate oil system with oil pump is used to lubricate and to cool the bearings and gears.