Abstract: Method and apparatus for performing operations in a well near the surface of which is a blowout preventer stack. The apparatus includes a bell nipple assembly extending upwardly from the blowout preventer stack and a lubricator assembly for central disposition within the bell nipple assembly. The bell nipple assembly includes a flange member for attachment to the blowout preventer stack having locking pins radially movable between retracted positions and extended positions in which the pins penetrate the flange bore. The lubricator assembly includes a tubular mandrel which may be lowered and locked in the bore of the bell nipple flange member in nonsealing engagement therewith by the locking pins thereof. At least one flow passage through the body of the mandrel assures that no pressure seal is established in the annular spaces between the bell nipple assembly and the lubricating assembly.