| 摘要 |
A combination cementing shoe and basket, comprising a substantially tubular mandrel having a cement basket disposed thereabout, the cement basket being maintained in a collapsed mode by an annular overshot at the bottom of a coupling at the top of the mandrel. A flapper valve assembly is located within the mandrel, being maintained in an open mode by the presence of a fillup tube disposed in the valve orifice. The bottom of the fillup tube is secured to a slidable ball seat located below the flapper valve assembly. The ball seat is initially secured in place by attachment through a plurality of shear rods to a tubular activating sleeve disposed around the mandrel and under the cement basket, the activating sleeve being maintained in its initial position by contact with the bottom of the cement basket, which is fixed to the mandrel by a shear screw. To operate the apparatus, a tripping ball is pumped down the casing to the ball seat, whereupon the casing pressure would cause the basket shear rods, acted upon by the activating sleeve, to shear, the basket moving downward and out from under the coupling overshot. Continued application of pressure causes the activating sleeve screw to shear, allowing the ball seat to move to the bottom of the mandrel, and removing the fillup tube from the flapper valve orifice, permitting the flapper to close.
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