Mechanical model and lateral force factors of lower drilling tools

This study develops bottomhole assembly (BHA) mechanism to investigate the factors influencing lateral forces during the drilling process. The key drilling parameters, such as WOB (weight on bit), and borehole wall conditions are considered in this outside diameter to describe the mechanical property of BHA. The lateral force is decomposed and analysed using triple bending moment equations. The results demonstrate that the well inclination angle and borehole enlargement rate significantly influence the lateral force, and the former exhibiting particularly high sensitivity. However, the change of WOB has merely effect on the azimuthal force. But increasing the outer diameter of the drill collar presents advantages of lateral force decrease and disadvantages of azimuthal force increase. Furthermore, the formation-induced bending moment substantially impacts lateral and azimuthal forces, which can indicate the direction of borehole bending. These findings provide a theoretical foundation for optimising drilling trajectories through the appropriate selection and control of tool parameters.