TWIN DRILL STEM Russian patent published in 2002 - IPC

FIELD: drilling of geologic prospecting holes with use of twin drill stems, cleaning of sand obstacles in wells of oil fields by means of built-in apparatuses sunk on twin tubing. SUBSTANCE: twin drill stem includes twin drill pipes. Each twin drill pipe has internal and external pipes placed concentrically, their ends being fixedly joined to nipple and coupling. Recesses forming internal cylindrical protrusions are made in butt surfaces of nipple. One protrusion is fixedly joined to end of internal pipe, the other protrusion, on side of thread in nipple contacts free end of another internal pipe while twin drill pipes are screwed into stem. Longitudinal conduits connecting recesses are made in body of nipple. EFFECT: enhanced functional reliability of twin drill stem thanks to improved sealing and increased strength of twin drill stem. 3 dwg