| 摘要 |
A sub-surface release plug assembly for use in cementing an outer casing annulus around a well casing. The assembly includes a top plug releasably connected to a drill string by a collet mechanism and including a swivel connector and a vent thereabove. A sleeve assembly extends through the top plug, and a bottom plug is releasably attached thereto. A vent is provided in the sleeve assembly between the top and bottom plugs, and this vent may be closed prior to releasing the bottom plug. The construction of the inner sleeve assembly provides that no high pressure from the drill string is applied to inner portions of either the top or bottom plugs. Thus, the plugs may be made of relatively soft, easily drillable material, even including plastic. When the lower plug is released and pumped to the bottom of the well casing, additional pressure opens a valve so that a flow passageway is provided therethrough. A slidable, sealing sleeve prevents fluid in the drill string from being in contact with the collet mechanism prior to releasing the top plug. |
