Mechanical Analysis Of Dynamic Point-the-bit Rotary Steerable Bottomhole Assembly And Key Component Design

With the development of deep formation,deepwater and unconventional oil and gas production,more complex geological features are encountered,and well types are evolving.The proportion of complex structural wells such as ultra-deep wells,large displacement wells,ultra-thin horizontal wells,multi-branching wells,and difficult directional wells is increasing,making it more difficult to control well trajectory.So there is an urgent need for rotary steering technology that can achieve high precision targeted drilling.However,domestic mainly focus on static push-the-bit system,which has a big gap with foreign countries.In some areas,tool reliability,build-up-rate,temperature resistance,and wellbore trajectory control accuracy cannot meet field requirements,so it relies on expensive leasing for a long time,which greatly increases the production cost.Therefore,to achieve cost reduction and efficiency improvement,this paper makes a breakthrough from two aspects of structural reliability and deviation performance.Carry out research on design of rotary steerable actuator,mechanical analysis of bottom hole assembly(BHA),design and check of key components.Firstly,based on the investigation and characteristic analysis of existing rotary steerable tools,a new dynamic point-the-bit rotary steerable actuator was designed,which innovatively adopted discontinuous shaft structure to improve the service life and deflection performance.The kinematic relation between eccentric ring and shaft was deduced and the regulation method of well inclination and azimuth was expounded.Secondly,based on the generalized continuous beam-column theory,the BHA mechanical model of dynamic point-the-bit rotary steerable tool was established to calculate the bit side force and angle.Based on the limit curvature method,the build-up rate was also predicted.The influences of BHA structure parameters,drilling parameters and stabilizer position on the bit side force and the build-up rate were analyzed.After the relevant parameters were selected,the tool deflection performance was verified by comparative analysis.Then based on the mechanics analysis model of BHA,the mechanical analysis software of dynamic directional rotary steerable tools was developed by the compilation platform,which is convenient to apply the mechanical calculation model and method to the production practice.Finally,guided by the overall tool structure and mechanical analysis of the tool,the key transmission parts and lower sealing parts were designed.Based on the fourth strength theory,the finite element method was used to check the structural strength of the transmission components under different working conditions,which concluded there was no structural damage.Based on virtual work principle and Mooney-Rivlin constitutive model,the static seal simulation analysis of the lower seal O-ring under conventional drilling and deviation was carried out,and the seal structure was stable and reliable.The work done has provided theoretical support for the domestic rotary steerable tools to achieve performance improvement and break the technological blockade.