Research On Variable Stiffness Method Of Shock Absorber In Deep Well Drilling

In oil and gas drilling,severe drill string vibration will cause damage to the drill bit and the drill string.Therefore,research on the causes of drill string vibration,vibration forms,and corresponding drill string vibration suppression techniques has been a hot topic at home and abroad.Drill string shock absorbers can effectively reduce the vibration.The stiffness of shock absorbers has a significant impact on its function of reducing the drill string vibration and avoiding the resonance of the drill string.Therefore,the realization of variable stiffness of the shock absorber has a very important significance.This article mainly carried out the following research work and achieved some results:1.The related theories and influencing factors of drill string three-dimensional vibration are systematically analyzed.The numerical simulation of example wells is carried out using ANSYS finite element software.The longitudinal vibration model of the drill string,such as the length of drill string and the stiffness of shock absorbers,is actually calculated and analyzed.The effect of the vibration damping method was further summarized and the mechanics of the shock absorber was discussed.2.This article studies and analyzes the types,structures and working principles of various drill shock absorbers.It also analyzes the realization of the variable stiffness of the shock absorber,which is of great significance for improving the effect of the shock absorber.A method of varying the stiffness of various types of shock absorbers was proposed.3.This article analyzes the characteristics and application of different types of metal springs and liquid springs.The variable stiffness characteristics of the disc spring damper design were analyzed by changing the disc spring series,selecting different disc spring sizes,and combinations.And a set of example disc spring calculations were performed.The effects of different types of liquid springs and different length of the liquid spring cavity on the hydraulic shock absorber were analyzed.A variable stiffness scheme for a combination mechanical shock absorber with upper and lower two-stage springs is proposed.Two kinds of disc spring combinations are selected,and the variable stiffness characteristics of the spring are calculated and analyzed as the compression amount changes.4.This article proposes a variable stiffness design for a dual-chamber hydraulic shock absorber with a floating seal block.The effect of different types of liquid springs and volumes on the stiffness of the upper and lower chambers is analyzed.Using ADINA finite element software to establish a model,a numerical simulation of four working conditions was performed on a dual chamber hydraulic shock absorber with a floating seal block.Through the calculation of ADINA finite element software,the flow field displacement,pressure and velocity distribution characteristics of the liquid spring in the double cavity were analyzed,and the deviation between the calculation result of the stiffness and the theoretical value was verified.An adaptive analysis was performed for the proposed hydraulic variable stiffness shock absorber.The research in this paper has important application value and significance for the design of variable stiffness drill string shock absorber and the realization of variable stiffness.