| 摘要 |
In accordance with an illustrative embodiment of the present invention, a restriction sub apparatus for use during well cementing operations includes a tubular body having an internal annular recess, and a plastic restriction sleeve mounted in the recess, such sleeve having an inner diameter which is less than the inner diameter of the body so that when a drive plate on a cement displacement plug encounters the inner portion of the sleeve during downward movement, such inner portion is progressively deformed and bulged inward until the bulge dissipates into a recessed region near the bottom end of the sleeve. The resistance afforded by the plastic sleeve to downward movement of the plug provides a positive pressure surge indication at the surface that the plug is located at a particular depth in the casing.
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