Research On Rock Breaking Mechanism Of Ring-grooved Diamond Bit

For the existing diamond bits used in drilling industry,there exist several disadvantages.On one hand,size of the rock debris generated by the bit is too small for engineers to analyze the formation lithology,on the other,the rate of penetration(ROP)is quite low and the service life of the bit is short.Aiming at solving these problems,a novel bit,i.e.the ring-grooved diamond bit,is put forward in this paper.On the novel diamond bit,several sunken sections are set in the crown profile so that ring grooves will be shaped on the wing-blade around the bit center.Accordingly,ring shaped rock protrusions will be formed in the bottom-hole when the bit drills,which is brittle and tend to be fractured volumetrically.Thus,the size of rock debris is enlarged and the rock-breaking efficiency of the bit is improved.To study the structure characteristics and working principles of the bit,unit experiments,which including static pressing of individual tooth and cutting of PDC cutter,are conducted in conditions of different rock types and different sizes of rock protrusions.Furtherly,a full-size ring-grooved PDC bit is designed and manufactured,and accordingly contrast experiment between the novel PDC bit and the conventional PDC bit is conducted.Moreover,finite element method is used to analyze the rock-breaking mechanism of the novel bit.To study the ring-grooved PDC bit,structure characteristics,rock-breaking mechanism,drilling efficiency and stability of the bit are respectively researched.Both theoretical and experimental analyzing results show that the novel PDC bit is more stable than the conventional one,and that rock-breaking efficiency of the novel PDC bit is obviously higher with much larger sized rock debris generated.On the other hand,unit experiments in aspects of different rock properties,different sized rock protrusions and different side angles of the PDC cutter are conducted.Simulation and experiment results show that generation of the rock protrusions can,on one hand,significantly improve the penetrating ability and rock-breaking efficiency of the cutter,on the other,is high rock breaking efficiency of the bit.On basis of experiment and FEM simulation,rock-breaking mechanism of ring-grooved diamond bit is researched,which not only revealed the breaking mechanism of the rock protrusion and the influencing law of the protrusion size on rock-breaking,but also proved the feasibility and practicability of the ring-grooved diamond bit,thus providing significant theoretical basis and experimental foundation for further design of the bit,which has proved the research to be of high theoretical value and great engineering significance.