| 摘要 |
A variable angle directional drilling "sub" provides a shifting end portion which allows the sub to be rotated from a first, in-line, axially straight orientation with the drill string to a selected second, angled or "bent" position, which second position is normally assoicated with conventional bent "subs" which are permanently structured in the bent position. The tool provides a multiple choice of varying angles to the sub in its bent position to satisfy differing directional drilling situations. A first embodiment (FIGS. 1-7) is manually set and varied at the surface by positioning two angularly marked sections temporarily rotatable with respect to each other until the desired angle set is matched up, while a second embodiment (FIGS. 8-9) is motor driven to allow varying the angle direction while "down in the hole". The device rotatably shifts about an off-set axis of rotation from the first (in-line) position to the second (bent) position either (in the first manually adjustable embodiment) upon the application of torsional force thereto, which torsional force can be applied, for example, by the actuation of a "turbodrill" (normally attached in operation), or (in the second motorized embodiment) by an electrical signal from the surface to a built-in motor contained within the tool. The axially aligned first position allows easy entry of the drill string, sub, and turbodrill into the well hole, while the second bent position is used down in the hole to commence directional dirlling at the desired off-set or deviated angle. In the first embodiment, the sub will return gradually to its original axially aligned position when the device is withdrawn from the wellhole, as such position is the path of minimum resistance for the withdrawing drill string and torsion is not present to hold the sub in the bent position; while in the second embodiment the built-in motor is merely backed off to its original position.
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