| 摘要 |
A well borehole is prevented from deviating from its intended vertical path as it is being drilled by use of a sub assembly which is eccentrically weighted with respect to its axis of rotation. Such a sub assembly can comprise a straight tubular member weight relieved along one side by, for example, forming a cavity within the heavy walls of the tubular member along the side of the collar. Thus, the eccentric weight is imposed upon the drill bit without providing any protrusions or elbows which are designed to bear on the wall of the borehole. Additionally, as the cavity is contained within the heavy walls of the tubular member, drilling fluids containing various debris cannot inhabit the cavity, thus maintaining a constant eccentric weight upon the drill bit.
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