Drilling system, biasing mechanism and method for directionally drilling a borehole

摘要

A drilling system for directional drilling of a borehole includes a biasing mechanism having a pivot associated with a lower bearing assembly, an offset mechanism associated with an upper radial bearing assembly, and a toolface controller, whereby the angular relationship of a drill bit and its toolface angle may be actively managed.

主权项

1. A biasing mechanism comprising:
a bearing section, including a housing having a lower end and a longitudinal axis, including a lower bearing assembly and an upper radial bearing assembly within the housing, wherein the housing is non-sealed to permit a drilling fluid to lubricate the lower bearing assembly and the upper radial bearing assembly; an offset shaft, having a longitudinal axis, an upper end, and a lower end, independently rotatable within the housing, the offset shaft having a first portion, including the lower end of the offset shaft, extending outwardly from the lower end of the bearing section housing, a second portion disposed within the bearing section housing associated with the lower bearing assembly, and a third portion disposed within the bearing section housing associated with the upper radial bearing assembly; and a biasing assembly associated with the bearing section to bias the offset shaft to be angularly displaced to permit directional orientation of a downhole assembly, the biasing assembly including: a pivot having a mid-point, the pivot being associated with the lower bearing assembly of the bearing section and comprising a spherical bearing through which passes the second portion of the offset shaft; and an offset mechanism associated with the upper radial bearing assembly of the bearing section, which can selectively vary an angular relationship between the longitudinal axes of the housing and the offset shaft.