Importance

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Abstract

A downhole adjustable stabilizer and method are disclosed for use in a well bore and along a drill string having a bit at the lower end thereof. A plurality of stabilizer blades are radially movable with respect to the stabilizer body, with outward movement of each stabilizer blade being in response to a radially movable piston positioned inwardly of a corresponding blade and subject to the pressure differential between the interior of the stabilizer and the well bore. A locking member is axially movable from an unlocked position to a locked position, such that the stabilizer blades may be locked in either their retracted or expanded positions. In the preferred embodiment of the invention, the stabilizer may be sequenced from a blade expanded position to a blade retracted position by turning on and off a mud pump at the surface. The stabilizer position may be detected by monitoring the back pressure of the mud at the surface, since the axial position of the locking sleeve preferably alters the flow restriction at the lower end of the stabilizer. High radially outward forces may be exerted on each stabilizer blade by one or more radially movable pistons responsive to the differential pressure across the stabilizer, and the stabilizer is highly reliable and has few force-transmitting components.

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First Claim