EXTENDABLE WELL REAMER Russian patent published in 2008 - IPC E21B7/28 

FIELD: oil and gas well drilling, particularly equipment for well diameter increase used instead of drilling bits.

SUBSTANCE: reamer comprises central body 1 with through channel receiving hollow shaft 3 with piston 4. The shaft is spring-loaded with spring 5. Lower shaft end has tooth-like extensions engaging blade 6 extensions. Bush 2 is arranged between body 1 and hollow shaft 3. Upper end of bush is closed with lid having orifices. Needle 8 is connected to lid center. Shaft 7 bush made of hard-alloy material is arranged inside shaft 3. Body 1 has longitudinal grooves for blade 6 advancing and flushing orifices provided with replaceable water-jet hard-alloy heads 13. Cutting surfaces of blades 6 are reinforced with diamond-insert plates and/or PDC-bits. Centrators 11, 12 are secured to upper and lower reamer parts.

EFFECT: increased structural strength, especially for holes having low diameters, increased accuracy of well reaming beginning time and, as a result, extended service life.

3 cl, 1 dwg