Research On Rock-breaking Mechanism Of Stinger Cutters And New Bits Development

Low drilling speed is one of the main technical bottlenecks that restrict the speed and efficiency of reservoir exploration and development.There exist many problems in the available drilling methods,such as low ROP and short life of drilling tools for utilization.Plow-Crushing PDC bits,whose stinger cutters have positive cutting angle,are designed for the hard formation,showing good results in some field and lab tests at home and abroad.However,the rock-breaking mechanism and laws of the stinger cutter with positive cutting angle are unknown,which restrict the application of stinger cutter.To address this issue,a new stinger cutter was developed in this paper,and the rock-breaking mechanism and laws were analyzed by experiment and numerical simulation.Furthermore,a plow-crushing PDC bit was designed and applied to a series of field tests.The results manifested that it is a highly efficient tool for hard formation drilling.The influence of stinger cutter's structural parameters on the mechanical properties,including the drilling ability,the shock resistance,the abrasion resistance and the structural strength,were studied through impact and wear tests and numerical simulation.A stinger cutter with good performance was developed,which provided a new rock-breaking components.The rock-breaking process of stinger cutter was simulated based on explicit dynamic software LS-DYNA,and the crack formation and stress state of rock were obtained.The results showed that the stinger cutter breaks rock by means of tensile failure,and it has good effect on breaking the hard rocks compared with the conventional PDC cutter.The best cutting angle of stinger cutter was determined by analyzing the effects of cutting angle and WOB on the rock-breaking efficiency of stinger cutter through cutter rock-breaking test.Furthermore,we compared the influence of WOB on rock-breaking efficiency of stinger cutter and conventional PDC cutter,which provided a theoretical basis for cutter distribution design.The bits with different cutter arrangement were designed and processed.The influence of cutter arrangement on rock-breaking efficiency were analyzed by indoor bench tests.Combined the above research results,the plow-crushing mixed PDC bit was designed and processed.This new mixed bit with PDC cutters as the main working components and stinger cutters as the secondary element breaks rock in shearing and plowing way,and it has achieved a good effect in hard and heterogeneous formation.