System containing expendible isolation valve with frangible sealing member, seat arrangement and method for use

A frangible, ceramic valve flapper means comprising:

• a. a radially inwardly sloping sealing surface on one side;
• b. a thickened center section;
• and
• c. an integrally molded hinge means having a hinge pin bore therethrough adjacent said thickened center section.

An extrusion resistant valve seat assembly for use with a machinable, frangible flapper means comprising:

• a. a cylindrical seat member with an opening therethrough and an annular retaining groove formed around said opening;
• b. a resilient seal means with a mating surface to fit within said retaining groove;
• c. a first support shoulder provided by a portion of said retaining groove;
• d. a second support shoulder formed on a resilient seal means for engagement with said first support shoulder when said resilient seal means is disposed within said annular retaining groove;
• and
• e. a valve seating surface on said resilient seal means formed to engage said sealing element to block fluid flow through said opening.

In a gravel pack system consisting of, in combination:

• a. a packer having slips and seals;
• b. a closing sleeve threadedly connected to said packer;
• c. a retrievable, expendable isolation valve assembly having a flow bore therethrough threadedly connected to said closing sleeve;
• d. a shear sub threadedly connected to said isolation valve assembly;
• e. a service seal unit disposed within said closing sleeve;
• f. one or more sand screens threadedly connected to each other and to said closing sleeve;
• g. a seal bore sub threadedly connected to one of said sand screens;
• h. a tell-tale screen threadedly connected to said seal bore sub;
• and
• i. said tell-tale screen stabbed into a sump packer wherein said retrievable, expendable isolation valve assembly contains the improvements of a machinable, frangible flapper means having integrally molded frangible hinge means rotatably mounted therein and an extrusion resistant valve seat assembly fixedly mounted in flow registration with the flow bore.

The method of pressure testing a subterranean well and preserving well completion fluids from loss to the producing formation comprising the steps of:

• a. assembling a production tubing string with a work string concentrically disposed therein;
• b. running said assembled production and said work string as a unit to the desired depth in the hole;
• c. manipulating a packer setting tool to set said packer in the well casing and to seal said packer to said well casing;
• d. gravel packing said well by conventional means;
• e. pulling said work string from within said production tubing until a no-go locator on said work string comes into contact with a no-go shoulder within the bore of a protector tube which is shearably mounted in flow registration within the flow bore of a flapper valve having a machinable, frangible sealing element;
• f. applying sufficient upward force to break shear screws thereby releasing said protector tube and allowing its withdrawal from the bore of said valve;
• g. removing said protector tube thereby allowing said sealing element to rotate to the closed position;
• h. manipulating said work string to move a closing sleeve from an open position to a closed position;
• i. allowing completion fluids to collect in said production tubing above said valve means and removing said collected completion fluids by conventional means;
• j. pressure testing said tubing;
• k. lowering a blind box hammer having a toothed striking face into striking engagement with said frangible sealing element thereby shattering said sealing element;
• l. removing said blind box hammer from the well bore;
• and
• m. placing said well into production.