Cementing plug launching mandrel

Claim 2

In cementing plug apparatus for use in cementing a well pipe in a well bore, comprising: a mandrel, means for connecting said mandrel to the well pipe with said mandrel extending longitudinally in the well pipe, said mandrel having a passage therethrough for the flow of fluid into said well pipe through said mandrel, cementing plug means having a passage for the flow of fluid from said mandrel passage into said well pipe, said plug means having means cooperative with a closure in the fluid for closing said passage in said plug means, releasable means connecting said plug means to said mandrel and releasable by the pressure of fluid in said mandrel upon closure of said passage through said plug means, the improvement wherein said mandrel has fluid pressure operated piston means operable upon closure of said passage in said plug means to assist in the release of said releasable means.

Claim 3

In cementing plug apparatus as defined in claim 1, said releasable means comprising shearable means connecting said plug means to said mandrel, said piston means including an annular piston chamber in said mandrel, an annular piston reciprocable in said chamber and extending from said chamber into engagement with said plug means, and fluid inlet means in said mandrel leading from the passage in said mandrel into said piston chamber.

Claim 4

In cementing plug apparatus as defined in claim 1, said mandrel also having means defining a surge chamber communicating with said passage in said mandrel for absorbing the shock pressure caused by closure of said passage in said plug means to prevent release of said releasable meanS by such shock pressure.

Claim 5

In well-cementing apparatus as defined in claim 1, said plug means including a top plug and a bottom plug, said releasable means connecting said top plug to said mandrel, and including additional releasable means connecting said bottom plug to said top plug, said bottom plug having a passage for the flow of fluid therethrough into said well pipe from said passage of said top plug, and means in said passage in said bottom plug cooperative with a closure in the fluid flowing through said latter passage to close the same and effect release of said bottom plug from said top plug.

Claim 6

In well-cementing apparatus as defined in claim 1, said mandrel having port means for balancing the pressure across said plug means until said passage through said plug means is closed.

Claim 7

In well-cementing apparatus as defined in claim 1, said piston means comprising a sleeve disposed about said mandrel in spaced relation thereto and defining with said mandrel an annular piston chamber, fluid inlet means leading from the passage through said mandrel into said piston chamber, and an annular piston in said chamber and projecting therefrom to engage said plug means.

Claim 8

In well-cementing apparatus as defined in claim 1, said piston means comprising a sleeve disposed about said mandrel in spaced relation thereto and defining with said mandrel an annular piston chamber, fluid inlet means leading from the passage through said mandrel into said piston chamber, and an annular piston in said chamber and projecting therefrom to engage said plug means, said sleeve and said piston having cooperative stop means to prevent displacement of said piston from said chamber prior to assembly of said plug means with said mandrel.

Claim 9

In well-cementing apparatus as defined in claim 1, said piston means comprising a sleeve disposed about said mandrel in spaced relation thereto and defining with said mandrel an annular piston chamber, fluid inlet means leading from the passage through said mandrel into said piston chamber, and an annular piston in said chamber and projecting therefrom to engage said plug means, said sleeve having an elongated extension spaced from said mandrel and having sealing engagement with said mandrel in spaced relation to said piston means to form an elongated surge chamber communicating with said passage in said mandrel through said fluid inlet means to said piston chamber.

Claim 10

In cementing plug apparatus as defined in claim 1, said releasable means comprising shearable means connecting said plug means to said mandrel, said piston means including an annular piston chamber in said mandrel, an annular piston reciprocable in said chamber and extending from said chamber into engagement with said plug means, and fluid inlet means in said mandrel leading from the passage in said mandrel into said piston chamber, said mandrel also having means defining a surge chamber communicating with said passage in said mandrel for absorbing the shock pressure caused by closure of said passage in said plug means to prevent release of said releasable means by such shock pressure.

Claim 11

In well-cementing apparatus as defined in claim 9, said surge chamber communicating with said passage in said mandrel through said fluid inlet means.

Claim 12

In cementing plug apparatus for use in cementing a well pipe in a well bore, comprising: a mandrel, means for connecting said mandrel to the well pipe with said mandrel extending longitudinally in the well pipe, said mandrel having a passage therethrough for the flow of fluid into said well pipe through said mandrel, cementing plug means having a passage for the flow of fluid from said mandrel passage into said well pipe, said plug means having means cooperative with a closure in the fluid for closing said passage in said plug means, releasable means connecting said plug means to said mandrel and releasable by the pressure of fluid in said mandrel upon closure of said passage through said plug means, the improvement wherein said mandrel inCludes means defining a surge chamber communicating with the fluid passage through said mandrel for absorbing the shock pressure wave caused by closure of said passage through said plug means.

Claim 13

In cementing plug apparatus for use in cementing a well pipe in a well bore, comprising: a mandrel, means for connecting said mandrel to the well pipe with said mandrel extending longitudinally in the well pipe, said mandrel having a passage therethrough for the flow of fluid into said well pipe through said mandrel, cementing plug means having a passage for the flow of fluid from said mandrel passage into said well pipe, said plug means having means cooperative with a closure in the fluid for closing said passage in said plug means, releasable means connecting said plug means to said mandrel and releasable by the pressure of fluid in said mandrel upon closure of said passage through said plug means, the improvement wherein said mandrel inCludes means defining a surge chamber communicating with the fluid passage through said mandrel for absorbing the shock pressure wave caused by closure of said passage through said plug means.

Claim 14

In cementing plug apparatus as defined in claim 11, said means defining a surge chamber including an elongated sleeve connected at its opposite ends to said mandrel and defining with said mandrel an elongated annular space, and port means leading into said space from said fluid passage through said mandrel.

Claim 15

In cementing plug apparatus as defined in claim 11, said mandrel having port means for balancing the pressure across said plug means, said port means being located to be closed by said closure when said closure closes the fluid passage through said plug means to confine fluid to said passage.