| 摘要 |
The present invention relates to a plug-dropping container for releasing plugs or other objects into a wellbore during fluid circulation procedures. In one aspect, the plug-dropping container is used as part of a cementing head. The plug-dropping container comprises an elongated housing, and a canister disposed co-axially within the housing. The canister is movable from a lower position to an upper position. In its lower position, a fluid bypass area is defined above the canister. When a dart is retained within the canister, fluid is diverted through the bypass and around the canister within an annular area defined between the canister and the housing. In one aspect, the canister is moved by rotation of a plug-retaining device below the canister. In its plug-retained position, the plug-retaining device is oriented so that the wall of the plug-retaining device is blocking the downward path of the dart. In the plug-released position, the plug-retaining device raises the canister to its upper position, substantially shutting off the bypass. A channel in the plug-retaining device is thus aligned with a channel in the canister for receiving the plug, and for release into the wellbore.
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