back of fluid through the coiled tubing forming the maintenance tubing in a manner known per se the hydroejector 3 is inserted with the aid of an obturator connector 4 shown in fig5 of the drawings this connector 4 comprises a quarter turn valve 4a housed in a bore 4b and adapted to be oriented by means of a pin 4c this type of connector also comprises a plurality of seals 4d and an outer surface having a curvilinear profile into the indentations of which the tubular parts of the members to be connected are crushed by force fig5 the lock chamber is reconnected the jaws of the blow out preventer are opened and the lowering of the coiled tubing joined to the hydroejector 3 by means of the connector 2 likewise of 38 mm 11 2 inch is continued so as to form the tubular part designated 1 in fig1 and 2 of the drawings when the stuffing box 6 reaches the level of the hydraulic separation position l and is thus engaged in the well bottom landing nipple 12 pumping of the working liquid into the annular space between the production tubing 10 and the maintenance tubing 1 2 3 4 5 6 and 7 can start the pressure of the working liquid enables the stuffing box 6 to bear perfectly against the seat 12a of the landing nipple 12 and to be locked thereon in respect of translation hydraulic separation is achieved and the part of the production tubing situated below the hydraulic separation designated lb and consequently also the well bottom are isolated from the annular space under elevated pressure lh situated above the hydraulic separation this hydraulic separation constitutes an important feature of.