CBM Drilling Rock Breaking Simulation And Drilling Parameters Optimization Research

As a new type of clean and environment-friendly energy in the future,coal-bed methane(CBM)has been actively exploited by various countries in recent years.CBM drilling rigs play an important role in drilling.The drilling rig parameters are important factors that influence and restrict the drilling speed,cost and quality.Optimizing the combination of drilling parameters can increase ROP,reduce bit wear and drilling costs.Therefore,in this thesis,some problems,such as long drilling cycle,low drilling efficiency,high drilling cost and lacking of experimental study on drilling rig working process were studied.Starting from the constitutive model of rock,a dynamic rock breaking simulation model of PDC bit cutting teeth was established.A multi-objective optimization model of drilling rig drilling parameters was established.The intelligent optimization algorithm was used to optimize the drilling parameters of the drilling rig.The optimization results can provide a theoretical basis for drill down in engineering practice.The main contents were as follows:(1)According to the rock damage theory and the physical and mechanical characteristics,constitutive model and damage characteristic equation of the rock under two kinds of loading conditions were established.The uniformity of the model was verified by comparison.The whole process stress-strain curve of coal seam due to variable axial force under the confining pressure of three-axis were obtained.Based on this,the rock breaking mechanism analysis of cutter cutting teeth was carried out.The whole process of bit cutting rock was analyzed.(2)The dynamic simulation model of bit breaking rock breaking process was established.The temperature field in rock breaking process was analyzed.The main influencing rules of cutting bit rate,cutting depth and tooth rake angle on PDC bit temperature rise were obtained.Based on the above model,the thermal deformation of PDC bit cutting teeth was analyzed.The coupling model of thermal stress and temperature was established,and the influence of temperature and cutting force on the deformation of cutting teeth was simulated.(3)Based on the simulation results,a mathematical model of temperature rise of PDC bit with cutting speed,depth of cut,and rake angle was established by using hyperbolic response method,and the deformation model of cutting tooth considering temperature rise and external force were established.The cutting tooth deformation was taken as the optimization goal to optimize the structural parameters of the cutter and the cutting process parameters.(4)Based on the classic drilling rig mechanical drilling speed and bit life model,taking mechanical drilling speed and bit life as optimize target,taking drill-pressure and bit speed as decision variables,the multi-objective optimization of drilling parameters for CBM drilling rig was achieved by using bio-geography optimization method with the goal of reaching high mechanical drilling speed and bit life.(5)The thesis was obtained under the condition that the cutting tooth deformation constraint was 0μm-0.1084μm.A set of optimal parameters of cutting speed,depth of cut and tooth rake angle.Under the precondition that the mechanical drilling speed was limited to Om/h-1Om/h and the bit life was limited to 0h-100h,multi-group optimization parameter combination of drill-pressure and bit speed.