Research And Application Of Integrated Coal Seam Coring Equipment Based On PDC Open And Close Bit And Double Channel Drill Pipe

Drilling core to determine coal seam gas content is a routine underground operation,especially in the current trend of coal mining to the deep development,strengthen the prevention and control of coal and gas outburst,the implementation of two "four in one" comprehensive anti-outburst measures become the focus of coal mine safety production.In view of the important role of coring in the prediction of outburst risk and the shortcomings of traditional coring mode such as complex operation,heavy workload and long time consumption,this thesis proposes an integrated coring equipment based on PDC open-closed bit and double-channel drill pipe,aiming at fundamentally optimizing the coring process,reducing the coring time and ensuring the safety of coal mine production.It mainly includes the following contents:(1)The stress of the suspension section and the bottom section of the drill pipe in the process of drilling is analyzed,as well as the thrust loss and torque loss on the section under the two states.Secondly,the force analysis of the shear rock breaking process of the cutter is carried out,and it is concluded that the normal force σ and shear force τ mainly influence the area and cutting Angle under compression.Three main failure modes of PDC bit are analyzed,which are the fracture of cutter,the wear of cutter and the loss of cutter.(2)Developed integrated coring equipment based on PDC open-closing bit and double-channel drill pipe.The equipment is mainly composed of PDC open and close drill bit,double channel drill pipe,core assembly device and special water tail,etc.The structural characteristics and working principle of each part of the equipment are introduced.The finite element analysis method is used to simulate the bit part.The results show that the maximum displacement deformation of the bit is 0.197 mm near the composite piece after applying the load,and the maximum deformation of the groove position is 0.15 mm.The allowance should be kept according to the deformation during the design of the bit.The maximum stress of the bit is located at the joint of the ends of the four wings,and the size is 219.71 MPa,which is far less than the yield limit of 45# steel 355 MPa.The results show that the bit meets the rigidity requirements and has high reliability in the working process.(3)The mechanical parameters of raw coal samples at 110503 working face in Yushutian Coal Mine are determined.The results show that the average compressive strength of coal samples is 11.55 mpa,the maximum compressive strength is 16.15 mpa,the average elastic modulus is 1.36 GPa,and the average Poisson’s ratio is 0.19.According to the test results,similar materials were prepared.Finally,the test block with sand/cement ratio of 2:1 and cement/gypsum ratio of 3:7 was closest to the test results of raw coal mechanical parameters,and similar materials were prepared with this ratio for ground simulation coring test.In the simulation experiment,the equipment operated smoothly and the sampling effect was in line with expectations.(4)The underground coring experiment scheme was developed,and the results were analyzed after the on-site coring was completed.It was concluded that compared with traditional coring,the coring while drilling device could save more than 1/3 time,and the sampling effect was stable.The weight of coal sample was mainly between 300-400 g,which could meet the sampling requirements.At the same time,the gas content of the coal sample was measured,and compared with the traditional coring method,the error of gas content is less than 5%,the coring effect is better.This thesis contains 50 figures,10 tables and 83 references.