gas lift without introduction of gas however it is to be understood that the invention can be used together with gas lift in order to reduce the need for lifting gas this for those cases wherein a further increase of the production is wanted or possible in fig2 there is illustrated a second example of a petroleum well wherein the present invention can find its application and wherein gas lift can also be used possible lifting gas will here be supplied to the production tubing 103 via a tubing 105 which runs on the outside of the production tubing 103 said lifting gas being controlled by means of an appropriate upper valve 104 the gas can appropriately be introduced in the production tubing 103 just above the perforations 108 towards the oil reservoir 106 fig3 illustrates further example of the invention used in connection with further auxiliary devices also here there is from an oil reservoir 206 supplied gas and liquid to the production tubing string 203 in a petroleum well said gas and liquid being transported via the well head 209 to a separator line 210 by means of said auxiliary devices in fig3 there will in the separator line 210 he created a moderate sub pressure or vacuum which together with the use of said discussed mixing elements n 1 nn in connection with fig1 will further contribute to the liquid lifting effect for petroleum wells given by the gas bubbles in the liquid containing little gas even moderate vacuum will create a u201c champagne u201d effect in the wells in question which can be utilised to a maximum by the mixing elements n 1 nn in order to reduce the pressure head resistance fig3 illustrates also that said separator line 210 is connected with.