Dynamic Simulation Of Journal Bearing System Of Roller Cone Bit

As drilling continues to move towards deep wells,ultra-deep wells and extended reach horizontal wells,the drilling process often encounters soft formations,hard formations,irregular soft and hard formations alternating and strong abrasive formations,which undoubtedly affects the drill bit,especially the bearing system demands higher performance requirements.In order to improve drilling efficiency,the bearings are required to keep running well for a longer time under high WOB and high ROP.However,due to the limitation of the bottom hole space,the design size of the roller bit structure is limited,and the space for tooth arrangement,the design of the cone shell and the journal size cannot be too large,which often results in strong transient impact,high WOB and high speed.Excessive wear of the bearing leads to failure.Therefore,the dynamic simulation study of roller cone bit journal bearing under the established boundary conditions and dimensions is helpful to grasp the mechanical behavior characteristics of the bearing in bottom hole operation,and it is also helpful to provide theoretical guidance for its structural optimization.This paper takes a certain (8 1/2)?type of three-cone bit journal bearing as the research object,and conducts dynamic simulation research on it.The specific research contents are as follows:(1)First,analyze the structure and force characteristics of the sliding bearing of the tri-cone bit,find the first loaded cone that fails,and take the largest loaded cone as the analysis object,and use Creo to establish the leg,journal,and cone.The three-dimensional model of the drill bit is appropriately simplified.(2)Secondly,using the ANSYS-Workbench transient dynamics analysis module,applying transient impact load to the drill bit,studying the law of bearing equivalent stress,elastic strain and radial vibration displacement over time,and proposing to modify the busbar convexity of the journal,Optimized design method for end round corner modification and cone inner hole arc modification.(3)Thirdly,by comparing and analyzing the distribution of stress and radial displacement of optimized and non-optimized bearings under transient impact load,it is concluded that the optimized bearing stress concentration has been improved,and the ability of resisting transient impact has been enhanced.(4)In addition,the influence of the clearance between the large and small journals and the cone on the stress distribution is studied,and the optimal matching clearance is found.(5)Then,the ANSYS/LS-DYNA explicit dynamics module is used to perform dynamic simulation on the simplified roller cone bit,and the law of the equivalent stress on the bearing changing with time is obtained.And further study is the change law of bearing stress and vibration displacement when the load and speed of the drill bit change.(6)Finally,combining the advantages and disadvantages of journal bearings,rolling bearings and floating sleeve bearings,a new type of bearing was designed and introduced into the cone bit.With conventional sliding bearings as the reference object,the dynamic stress of the new bearing structure and the cones were studied.The rules of nodal dynamic stress and journal vibration displacement with time provide a theoretical basis for the design and application of new bearings.