Importance

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Abstract

A wiper plug launching tool includes a body arranged to be lowered into a liner on a running string, the body having a tubular upper portion and a cylindrical lower portion, upper and lower wiper plugs loaded into the lower portion, each of the plugs having upwardly facing elastomer cups that are reduced in diameter during loading, a drive rod movably mounted in the upper portion of the body, a first piston or dart that is pumped down the running string and into engagement with the drive rod so that pressure applied to the first dart forces the rod downward to cause ejection of the lower wiper plug into the liner where cups of the plug expand to provide a moving seal at the lower end of a column of cement, and a second piston or dart that is pumped down into engagement with the first dart to force the rod further downward and cause ejection of the upper wiper plug into the liner where the cups of this plug expand to provide a moving seal at the upper end of the column of cement. A slidable valve is provided adjacent the upper end of the drive rod and is effective to close lateral flow ports upon downward movement of a dart and initial engagement with the drive rod. The drive rod has a piston mounted within a cylinder for cushioned movement upon metering of hydraulic fluid between the piston and cylinder during downward movement of the drive rod. A modification of the invention shown in FIGS. 9-11 utilizes three wiper plugs for sealing the liner.

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First Claim