Research On Rock Breaking Mechanism And Design Of PDC-Roller Compound Bit

In oil drilling engineering,the drill bit is the main rock-breaking tool,and its design has greatly affected the drilling cost and drilling efficiency.However,with the rapid reduction of shallow oil,drilling began to face more and more complex formations,deep wells,ultra-deep wells,and difficult-to-drill formations,so it also put forward higher and higher requirements on the design and use of drill bits.In recent years,with the successful application of the PDC-roller compound drill bit in foreign drilling sites,the excellent drilling data obtained has indicated a certain path for the development of the drill bit.For domestic,some manufacturers of drill bits are also eager to obtain high-performance and practical composite drill bits,so as to break the foreign technology monopoly and establish their own composite drill bit manufacturing technology and system.At present,the PDC-roller compound drill bit,as a new rock-breaking tool,has the advantages of high drilling efficiency,stable deflection,and long drill bit life in hard formations,dense formations,highly abrasive formations and directional drilling.Although some researches on composite drills have been carried out in China and certain research results have been achieved,the rock-breaking mechanism and design techniques of composite drills still need to be thoroughly studied and improved.To this end,this article carried out the following research on composite drills,mainly including:(1)The research on the structure and working principle of the PDC-roller compound drill bit was carried out,and the rock breaking mechanism and failure form of the PDC-roller compound drill bit were deeply analyzed,and the rock breaking advantages of the compound drill bit compared with the conventional drill bit;(2)The design-related factors of the PDC-roller compound drill bit are proposed:the composite of two sets of cutting structures,the shape of the roller cone,the tooth profile,the crown profile,and the gauge design method.The individual design of the composite drill bit for hard formations,uneven formations and directional drilling is discussed.According to the characteristics of complex and difficult-to-drill formations,a 121_1/4in composite drill bit was designed with a structure of three blades+three cones;(3)Using the finite element dynamic analysis software ANSYS to simulate the dynamic rock breaking process of the PDC-roller compound drill bit,the rock-breaking effect and the rock-breaking efficiency of the PDC-roller compound drill bit in the hard formation,as well as the bottom hole and well The distribution of the stress field of the wall rock;(4)According to the geometry and kinematics of the cone and the geometry and kinematics of the PDC fixed cutting blade,the geometry and kinematics of the PDC-roller composite bit are discussed and analyzed.Based on the geometry research,the bottom hole trajectory simulation software was compiled,and the simulated bottom hole trajectory of the bit was drawn.The theoretical research and design technology research done in this paper provide a reference for the design,evaluation and optimization adjustment of the PDC-roller compound drill bit.