| 摘要 |
An improved drill collar for forming relatively straight holes in crooked hole type formations. One or more hydraulic drill collars are connected in series relationship within a drill string above a rotary bit at the point of tangency. Each drill collar includes at least one outwardly opening, longitudinally extending slot formed on the exterior thereof. The slot includes a back wall connected to confronting sidewalls and opposed end walls. One lower end of a slot commences in spaced relationship to the lower pin end of the collar. As the drill string is rotated, drilling fluid forms a cushion between the slot and the nearest sidewall of the borehole, thereby kicking or forcing the drill collar away from the borehole sidewall, which in turn forces the drill bit to penetrate in a downwardly direction back towards a vertical position. The borehole meanders a very small amount, as for example 3-4 degrees, rather than uncontrollably leaving the vertical and forming an excessively crooked hole. Various configurations and arrangements of slots are disclosed in the collar.
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