Adjustable stabilizer

摘要

A downhole adjustable blade stabilizer is disclosed for varying the position of stabilizer blades to provide an increased ability to control the direction of drilling. The adjustable blade stabilizer includes a plurality of blades mounted in an angled track to permit axial and radial movement of the blades. The blades are driven by a piston in response to a pressure differential created by a sufficient flow of drilling mud through the stabilizer. The stabilizer blades are retracted by a spring when the pressure differential is eliminated. A positioning piston limits blade extension to a desired position. The positioning piston moves in response to a command signal, and remains in place until a new command signal is received. By maintaining the positioning piston in a locked position, the position of the blades can be reset to the prior position after the loss of pressure differential. A measuring device is provided in association with the positioning piston to enable precise measurement of blade position.