| 摘要 |
In accordance with illustrative embodiments of the present invention, restriction subs for use in setting cement plugs in wells include a tubular threaded adapter having an internal annular recess, and a metal restriction sleeve mount in such recess. In one embodiment, the sleeve has a corrugation that extends into the bore of the adapter to provide a deformable restriction; in another embodiment the sleeve has curved resilient tabs whose free ends extend into such bore. The restrictions are cooperable with a displacement plug having a metal expander member on its nose so that a distinct pressure is required to cause the expander member and plug to be forced through the restriction. |
