| Since traditional shallow well drilling can no longer meet the demand of China's oil and gas resources consumption,it is urgent and necessary to develop deep well and ultra-deep well drilling technology.However,with the increase of the number of deep wells in deep wells,due to the deep high abrasive formation,high temperature and high pressure and other factors,there are problems such as serious damage to the downhole tools,low rock breaking efficiency and slow drilling speed.Therefore,studying the working characteristics and failure mechanism of downhole tools in deep well high temperature environment is an effective way to ensure the efficient operation of downhole tools in high temperature environment of deep wells,improve the drilling speed of deep wells and reduce drilling costs.The screw drilling tool has become one of the most widely used downhole power drilling tools in China and even the world with its advantages of high torque,low speed,simple structure and high reliability.However,in the deeper and deeper well conditions of deep wells and deep wells,the performance of the screw drills deteriorates rapidly and the life is significantly shortened.The stator bushings are particularly vulnerable parts.According to the field statistics,the stator rubber lining The failure of the screw drill caused by the failure of the sleeve accounted for more than 30%of the total.Therefore,in order to improve the life of the stator rubber bushing,it is an urgent problem to extend the effective drilling time and drilling efficiency of the screw drill.At present,many scholars have carried out detailed research on two common stator bushing structures(conventional stator bushings and equal wall thickness stator bushings),and have obtained a lot of research results,but in the research of stator bushings,The maximum temperature involved is 120?,which does not reach the working ambient temperature of the bushings in deep wells and ultra-deep wells.Therefore,it is necessary to study the mechanical behavior and fatigue failure mechanism of the stator bushing rubber at higher temperatures.This paper will carry out the following research work on the above issues:(1)The basic theory of the fixed-rotor cycloidal line type of screw drilling tools is studied.By comparing the advantages and disadvantages of various motor equidistant line types,the inner and outer cycloidal normal-type stator bushings are selected as the research object.(2)The uniaxial tensile test of the hydrogenated nitrile rubber commonly used in the current stator bushing material was carried out,and the heat aging effect at a maximum temperature of 150? was considered,and the stress-strain curve at five temperatures was obtained;Comparing the numerical simulation results with the experimental data,the constitutive model which can more accurately describe the constitutive relation of hydrogenated nitrile rubber is selected.(3)The influence of formation temperature field,drilling fluid pressure,interference and eccentricity on the dynamic meshing behavior of conventional stator bushings and equal wall thickness stator bushings is studied,and this is analyzed by a single decoupling method.Thermal hysteresis effect of both bushings.(4)The fatigue test of hydrogenated nitrile rubber at normal temperature and high temperature was carried out,and the fatigue parameters of the material were obtained.Based on the analysis method of Abaqus+Fe-safe,the fatigue life prediction value of stator bushing was given and drilling The field data is relatively accurate and the predicted value is more accurate.Combined with the work done in this paper,the working mechanics characteristics of the stator bushings have a deeper understanding.The proposed fatigue life prediction method provides a more accurate evaluation index for the optimization and improvement of the bushing. |
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