| 摘要 |
A downhole tool including a purely mechanical stabilizer is disclosed. The stabilizer includes a plurality of fixed blades, each of which includes at least one automatically extendable and retractable piston. In use, a balance of forces determines the radial position of each piston; a hydraulic force urging the piston outward, a spring force urging the piston inward, and external forces acting on the tool (e.g., the force of the borehole wall urging the pistons inward). The stabilizer is further configured such that a balance of forces between the pistons causes the tool to be advantageously automatically and continuously centered during rotation of the tool in the borehole. As such, the invention is suitable for use in boreholes that rapidly change size and shape.
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