According to the statistical data of oil and gas exploration and development,stick-slip vibration frequently occurs during deep well drilling,accounting for more than 50%of the drilling time,seriously affecting the downhole drilling safety,prolonging the drilling cycle and increasing the drilling costs.Due to the complex structure of deep well drill strings,mud motors are widely used,but there is a lack of in-depth research on the impact of them on the stick-slip vibration of bottomhole bits,and no scholar has proposed a full-scale dynamic model for drill string under the influence of mud motors in deep wells.In this paper,based on the lumped mass principle of spring,a stick-slip vibration simulation model including mud motor and an output parameter calculation model of the PDM(positive displacement motor)are built to study the influence of PDM,torsional impactor and their combination on the stick-slip vibration of bit.Moreover,field drilling cases are analyzed based on the models.The results show that when a PDM is used to conduct combined drilling,the rotation speeds of the rotary table and the PDM have a significant influence on the stick-slip vibration:the higher the composite rotation speed,the more favorable it is to eliminate stick-slip vibration;the larger the WOB and bit size,the higher the rotation speed required to eliminate stick-slip vibration.Under the condition that hydraulic parameters are guaranteed,the higher torque and rotation speed of PDM can effectively suppress the stick slip of bit.Under the condition that the torsional impactor and the PDM are used in combination,when the output parameters of the PDM are insufficient to suppress stick-slip vibration,the increase of the impact torque and frequency of the torsional impactor can reduce the critical speed of the PDM and suppress bottomhole stick-slip vibration.It is concluded that the dynamic model can provide effective technical support for the rational use of mud motors,avoiding stick-slip vibration and improving the rate of penetration in deep wells,and the new theoretical understanding has an important practical significance in guiding rig site drilling,improving drilling efficiency and reducing drilling costs.
关键词
深井/钻柱振动/粘滑振动/动力学/井下动力钻具/顺北区块/螺杆钻具/扭力冲击器
Key words
Deep well/Drill string vibration/Stick-slip vibration/Dynamics/Mud motor/Shunbei Block/PDM/Torsional impactor
维普
万方数据