Analysis Of The Vibration Mechanics Of Drill String In Deep Wells

Since the 21 st century,China’s exploration and development of deep oil and gas resources have become increasingly thorough,and deep oil and gas have become an important direction in China’s oil and gas resource strategy.However,due to the expansion of deep well drilling,the frequency of drilling column failures has correspondingly increased,leading to a rapid increase in drilling costs.Additionally,during deep well drilling,drilling columns often experience vibration,which severely damages the drilling tools,reduces drilling efficiency,and increases drilling costs.Therefore,it is necessary to conduct research on the dynamic characteristics of deep well drilling columns,which has been done in the following ways:Firstly,the axial stress was used to determine the strength conditions of the drilling column under normal working conditions,and a theoretical calculation formula for the maximum working depth of the drilling column was derived.The impact factors that restrict the depth limit of the drilling column were also studied and discussed.The safety of the drilling tool combination of Cheng tan 1 well was verified,laying the foundation for the mechanical analysis of the drilling column of Cheng tan 1 well later.Secondly,a vibration dynamics model of deep well drilling columns was established,and the longitudinal,transverse,and torsional vibrations were theoretically analyzed using the linear element method,obtaining the drilling column’s inherent vibration frequency formula.The phenomenon of vortex-induced and viscous sliding vibrations of deep well drilling columns was analyzed,and the kinematics of drilling column vortex was analyzed.Based on the sliding friction and rolling friction of the drilling column,the energy loss equation of the drilling column vortex was derived,and the influence of various parameters on the energy loss during drilling column vortex was calculated and analyzed.Then,the theoretical equation of the drilling column vortex trajectory was established using the cycloid equation,and the ideal vortex trajectory of the drilling column was fitted through MATLAB.A viscous sliding vibration model of the drilling column system was established,and the drilling head’s viscous sliding vibration motion equation was derived,and the influence of various parameters on the viscous sliding vibration was analyzed.By plotting the trajectory of the drilling head’s motion relative to the turntable,the viscous sliding state of the drilling column system was studied.Thirdly,Utilizing the ANSYS limited element analysis software,a limited element model will be developed for the deep well drilling system of the Chengtou-1 well.Static analysis of the drilling column was conducted using this model to study the influence of drilling pressure and turntable torque on the equivalent stress of the drilling column,and the distribution law of the drilling column’s equivalent stress was obtained.Modal analysis was carried out on the deep well drilling column to obtain the distribution law of the inherent vibration frequency in the longitudinal,transverse,and torsional directions and to study the relationship between the inherent vibration frequency of the deep well drilling column and different drilling parameters.After that,harmonic response analysis was conducted on the longitudinal and torsional vibrations of the deep well drilling column,and the frequency-displacement spectrum curve of the drilling column at different depths was obtained through simulation and analysis of the drilling column’s vibration response at specific frequencies.Through this curve,the vibration characteristics of the drilling column at different frequencies were understood,providing more accurate data and guidance for vibration control and optimization during drilling.