首页|Torsion and vibration reduction mechanism of roller PDC hybrid bit
Torsion and vibration reduction mechanism of roller PDC hybrid bit
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NSTL
In directional drilling, torque fluctuation generates a big shock when using polycrystalline diamond compact (PDC) bits, causing problems such as instability in vibration tools. This study presents a new type of composite bit with a roller on the blade. The mechanism of torsion reduction and vibration of the roller PDC hybrid bit is studied through a rock breaking experiment on the roller unit and a comprehensive drilling experiment on the composite bit. Six roller contour shapes, different pressures into the depth of the roller, six roller radial positions and the relative height of roller teeth, and PDC cutters that affect the novel hybrid torsion on bit (TOB) and weight on bit (WOB) are investigated. The equivalent friction coefficient of the roller and axial force per unit depth is used to evaluate the torsional and vibration reduction ability of the Roller. The results show that the equivalent friction coefficient of different contour Rollers is lower than that of PDC cutters, and the torsion reduction ability of the Rollers is higher than that of PDC cutters. The vibration reduction in the roller teeth in different radial positions was 1.59-9.17 times higher than that of PDC cutters, The torque of the roller PDC hybrid bit is 71.72%-98.33% of the conventional PDC bit. The roller shares 1.59%~(-2)3.06% of the WOB of the whole bit. As the cutter teeth and the PDC cutter's relative height decreases, the compound drilling torque decreases, the roller bit's weight proportion gradually increases, the torsional capacity decreases, and the damping capacity increases.
NSTL
