| 摘要 |
An intermittent lift plunger includes at least one seal mandrel, a bottom sub and an upper valve assembly. The valve assembly is closed by a well bottom stop which inserts into the lift plunger and opened by a lubricator stop at the top of the well. The seal mandrel includes a sleeve seal formed from an elastomeric rubber or plastic, which inflates to engage the well bore surface when the valve is closed and a pressure differential exists.
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