Boring or penetrating the earth – Means traveling with tool to constrain tool to bore along...
Patent
1989-02-15
1990-08-14
Dang, Hoang C.
Boring or penetrating the earth
Means traveling with tool to constrain tool to bore along...
175325, E21B 708, E21B 710
Patent
active
049479440
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concers a device for steering a drill bit and/or a drill string For performing drilling operations consisting of an Internal pipe connectable to the drilling tool or a drill string, and an outer pipe rotatably supported on the same and provided with steering shoes.
BACKGROUND OF THE INVENTION
Devices of this type serve the function of stabilizing the drill tool or the drill string in the drilled hole and to counteract deviations of the drill bit from the preset drilling direction. Undesirable deviations occur particularly in the transition zones between harder and softer layers in deep-hole drilling, especially if the drill crosses these layers at an acute angle.
Up to now it has been known to achieve stabilization of the drill tool through the incorporation of steering devices, so-called course indicator rods or stabilizers. These are rod-type pipes mounted with steering shoes, the outer diameter of which corresponds to the drilling diameter, and follow the drill bit, steering it in a concentric manner. Such devices are available in various designs, for example rigid designs, where the stabilizing shoes are rigidly connected to the multiple drill rod unit and rotate in the drill hole, or those of the type first mentioned, where the stabilizing shoes are provided on a separate outer pipe in which the multiple drill rod unit is positioned for rotation. Target drill rods are already available for vertical drilling, with built-in automatic vertical steering utilizing gravitational force and using the pressure of the flushing fluid or the rotation of the drill rods to develop steering pressure
Known rigid steering devices have the disadvantage that they counteract the deviation of the drill tool from the drilling direction only to an insufficient extent. A reason for this is the fact that the diameter of the drilling tool must always be dimensioned a little larger than the diameter of the steering device in order to avoid jamming of the steering device in the drill hole. This is important above all because the diameter of the drill hole may diminish because of the wear of the drill bit. Therefore, known steering devices are not always urged tightly against the drill hole wall during the drilling process, so that the drilling tool may wander off course.
OBJECTS OF THE INVENTION
An object of the present invention is to create a steering device of the type mentioned first, which permits precise steering of the drill tool and drill string in operation and where the risk of jamming in the drill hole is avoided.
SUMMARY OF THE INVENTION
According to the invention this object is attained by providing the steering shoes in a radially movable manner in slotlike recesses in the outer pipe of the device and by providing, between the floor of the recesses and the bottom side of the steering shoes means of changeable position or shape, with which the steering shoes can be pressed against the hole wall In this way the steering shoes can be firmly pressed against the hole wall because their relative positions can be adjusted to variations of the drill hole diameter. Therefore, the steering shoes remain constantly in contact with the drill hole wall and in this manner provide sufficient stabilization of the drill tool and thereby more exact observance of the preset drilling direction.
Preferably the means for pressing the steering shoes against the hole wall consist of prestressed compression springs which are provided between the bottom side of the steering shoes and the floor of the recess in the outer pipe. The compression springs may be cup springs, spiral springs or flat springs. Furthermore, according to the invention the steering shoes may be kept in position in the recesses by screws which engage in tapped holes in the outer pipe and the heads of which are arranged in countersunk manner in stepped or shoulder holes in the steering shoes. With the aid of these screws it is possible to limit the largest possible outer diameter up to which the outer sides of the steering sho
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Coltman Trevellyn M.
Fletcher Alfred E. W.
Prevedel Bernhard
Dang Hoang C.
Dubno Herbert
Preussag Aktiengesellschaft
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