Experimental research on torque characteristic and weight distribution of the polycrystalline diamond compact-roller hybrid bit

On the basis of structural features and working principle of polycrystalline diamond compact- roller hybrid drill bit, a detachable experiment device with adjustable structural parameters are designed and manufactured for the hybrid bit, and accordingly, drilling experiments under different working conditions are conducted. The experiment results show that, first, the introduction of cones is beneficial to increasing the penetrating ability of the polycrystalline diamond compact cutters in hard formation, which is significant to improve the rock- breaking efficiency. Second, torque of the hybrid bit is obviously lower than the polycrystalline diamond compact bit of the same size, while roughly equal to that of the cone bit, which means the hybrid bit has a favourable drilling stability and is good for tool- face control in directional drilling. Third, as cone extrudes higher than the polycrystalline diamond compact cutters, the weight on the cone and the torque on the bit are both larger, but the larger fluctuation of the weight on bit is more severe. Fourth, with the decrease in hardness and increase in brittleness of the rock, the weight on the cone will increase accordingly. In conclusion, the hybrid bit has obvious technical advantages when drilling in hard and inhomogeneous formation as well as in directional and horizontal drilling.