Method, apparatus and system for selective release of cementing plugs

A well surface operated system for remotely deploying wiper plugs into a well casing comprising:

• a running tool having an axially extending tubular mandrel, said mandrel having an axially extending flow passage for conducting fluid axially through said well casing,
• a first plug carried by said mandrel, said first plug having an outside sealing diameter for sealing with an internal surface of said well casing and further having an axially extending flow passage cooperating with said axially extending flow passage of said running tool for conducting fluids axially through said well casing,
• a first release mechanism carried by said mandrel, said first release mechanism being operable from a well surface with a release mechanism actuator to actuate said first release mechanism to release said first plug from said mandrel, and
• a first flow passage closure device, separate from said release mechanism actuator, carried by said first plug, said first flow passage closure device being operable when said first plug is released from said mandrel to seal said flow passage extending through said first plug.

A method for releasing plugs in a well casing for cementing said well casing in a wellbore comprising:

• locking multiple plugs on a tubular mandrel of a running tool carried at the end of a well conduit,
• positioning said running tool and plugs within said well casing,
• flowing fluid through said well conduit and through said mandrel and plugs into said casing below said running tool,
• inserting a release actuator mechanism into said well conduit at the well surface,
• engaging said release actuator with an axially movable sleeve carried by said running tool,
• applying fluid pressure from the well surface to said release actuator to move said sleeve axially through said running tool for opening a flow passage from said mandrel into said casing and unlocking one of said wiper plugs from said mandrel, and
• applying fluid pressure across an area substantially equal to the full lateral cross-sectional area of said unlocked plug to produce a pressure induced force to move said unlocked plug axially for release from said mandrel.

An apparatus for deploying plugs used in cementing a casing string from a well surface comprising:

• a running tool adapted to be connected to the end of a tubular well pipe;
• a thin wall, tubular mandrel in said running tool, said mandrel having a central flow passage extending axially through said mandrel and first and second flow passages extending laterally through said mandrel wall into said casing string,
• first and second plugs having first and second central flow passages, respectively, coaxially mounted on said tubular mandrel,
• first and second release sleeves coaxially mounted with said tubular mandrel for temporarily locking said first and second plugs, respectively, to said mandrel and for temporarily sealing, respectively, said first and second lateral flow passages, and
• first and second sealing members carried on said first and second plugs, respectively, for sealing said first and second central flow passages, respectively, when said plugs are released from said mandrel.