| 摘要 |
Method and apparatus for recovering a stuck element from deep in a well. The lower end of an elastic steel column is attached to the upper end of the stuck element. The upper end of the column extends above the top of the well and is attached to a reaction mass lying vertically thereabove through (1) an accelerometer and then (2) vertically mounted compression springs in parallel with a vertically mounted servo-controlled hydraulic cylinder-piston assembly. A substantially constant upward load is applied to the reaction mass, and the piston of the hydraulic assembly is reciprocated under servo control to apply vertical vibration to the upper end of the column. This vertical vibration is adjusted through the servo control to an appropriate resonant frequency for the column in the range of 1/2 Hz to 25 Hz, and the frequency is maintained at resonance by a feedback system relying on maintaining a phase difference of 90 DEG between a displacement signal developed from the accelerometer and a pressure-differential signal related to the pressure difference between the opposite sides of the piston.
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