Study On The Law Of Rock Cutting With Conical PDC Cutter

Conventional PDC cutter is a rock breaking tool widely used in drilling operations in oil and gas industry.Its performance determines the drilling cost and production efficiency.With the increase of drilling depth,the rock breaking efficiency of conventional PDC cutter is limited,and the special structure and rock breaking mode of conical PDC cutter provide a new idea for rock breaking in deeper strata,which is of great significance to improve the exploitation efficiency of oil and gas.Therefore,this thesis takes the conical PDC cutter as the research object,aiming at the problems of rock breaking mode,cutting parameters and geometric structure of conical PDC cutter,and carries out research from three aspects of theoretical analysis,discrete element numerical simulation and experimental study.The main research contents are as follows:(1)On the basis of rock strength theory and mesoscopic damage mechanics,it is pointed out that the internal damage of rock reaches the limit state in detail as the extension of the internal main crack;The force analysis of conical PDC cutter is carried out,and it is pointed out that the conical PDC cutter is suitable for cutting rock samples at the pre-dip Angle through theoretical deduction,and the factors that affect the cutting load of conical PDC tcutter are: the mechanical properties of rock,the cutting parameters of cutting rock samples and the geometric parameters of conical tooth.(2)Using PDC single cutter rock breaking experiment platform,taking blue sandstone as the test object,the influence of cutting depth,rake Angle and rock stress state on horizontal cutting force of conical PDC cutter was studied based on control variable experiment method.The cuttings produced in the cutting experiment were screened and weighed,and the mass distribution of cuttings in the process of rock breaking by tapered PDC cutter was studied.It was found that the particle size of cuttings generated in the experiment would change under different cutting parameters.Using mechanical specific work(MSE)as measuring standard,the mechanical specific work of conical PDC cutter was calculated under different cutting angles.It was found that the mechanical specific work of conical PDC cutter decreased with the increase of cutting depth and lateral pressure of rock samples in a certain range.(3)blue sandstone sample model is established by PFC,and the conical PDC cutter broken rock simulation analysis,through the analysis of conical gear in the process of cutting sample sample the number of internal crack growth and its extended rule,reveals the tensile mechanism of rock fragmentation of conical teeth,and studied the influence of cutting parameters on the conical gear cutting load,The comparison between the numerical simulation and the experimental results shows that the discrete element numerical simulation is feasible under the condition of qualitative research.By comparing the crack formation and propagation in the process of simulated rock breaking under different conditions,the influence of different cutting Angle,cutting depth,cone tip Angle and cone tip radius on the crack formation and propagation was pointed out.The results provide a reference for the optimal design of conical PDC cutter and the design of new drill bits based on conical PDC.