STUDY ON SPINDLE OFFSET FORCE AND DEFLECTION PERFORMANCE OF POINT-BIT STEERABLE TOOL¹⁾

In order to study the influence of the installation position of weight on bit (WOB) transfer device on the spindle offset force and deflection performance of point-bit steerable tool, a mechanical model of spindle considering axial load is developed based on the mechanical model of transverse bending beam and the bending beam with combined axial and lateral load. The beam element assembly method is used to solve the string mechanics by using the general solution of differential equation. The geometric equation and mechanical equation of spindle are derived. And the effects of the position of WOB transfer device on the spindle offset fore and deflection performance parameters such as bit side force and bit inclination are investigated. The results show that when increasing the position of the WOB transfer device from the bit, the offset force required for tool spindle deflect will be reduced, and the bit-side force and bit inclination will be increased.