| 摘要 |
<p>A sub-surface release plug assembly (10) for use in cementing an outer casing annulus around a well casing includes a top plug (150) releasably connected to a drill string (14) such as by a collet mechanism (130) and preferably including a swivel connector (82) and a vent (56) thereabove. A bottom plug (232) is releasably attached to the top plug (150). A vent (220) is provided between the top and bottom plugs, and this vent may be closed prior to releasing the bottom plug. An inner sleeve assembly (257) is preferably provided so 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.</p> |
