Theoretical analysis of rock breaking technology with diamond composite coreless bit.

The impact rock breaking technology of diamond composite coreless bit mainly includes two aspects: axial impact and torsional impact. Its characteristic is to combine axial impact and torsional impact, and make use of the weakness of high brittleness and non impact resistance of hard rock to change the traditional shear rock into impact + shear rock, so as to improve the rock breaking efficiency.
The diamond composite coreless bit is impact pre crushed to form a crushing pit, and then the torque output of the screw motor is increased through the torsional impact module to cut the crushing pit formed by axial impact. At the same time, the torsional impact also balances the stick slip vibration in the circumferential direction of the drill pipe and reduces the circumferential torque accumulation of the diamond composite coreless bit The function of improving the service life of diamond composite coreless bit, and finally realize the continuous torque input of bit and high-frequency axial impact rock breaking, so as to improve the rock breaking efficiency of bit.
The combination of axial impact and torsional impact completes the bottom hole rock breaking of diamond composite chip coreless bit. Therefore, the frequency of these two types of impact is the main factor affecting the rock breaking efficiency. If it is assumed that the circumferential stick slip vibration frequency of the drill pipe is f, the axial impact frequency applied by the impactor is f and the torsional impact frequency is f. Ideally, the torsional impact frequency of the impactor can completely offset the stick slip vibration frequency of the drill pipe, and the axial impact frequency of the impactor should not only fully cover the bottom of the well when the bit teeth impact and break the rock, but also not cause the repeated breaking of rock cuttings at the bottom of the well, including the distance between the teeth and the center of the bit, the axial impact velocity and the angular velocity of the diamond composite coreless bit. In the real drilling process, the stick slip vibration frequency of drill pipe is related to rock properties, rock buried depth, hole depth and other factors. The only controllable parameters are the axial impact frequency and torsional impact frequency of the impactor. Therefore, the ideal rock breaking state can be achieved by adjusting the impact frequency of the impactor.

The above is the theoretical analysis of rock breaking technology with diamond composite coreless bit.