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A cup tool for use with a mandrel of a wellhead isolation tool has a substantially right-angled stepped shoulder over which an elastomeric sealing element is forced by elevated fluid pressures. A top end of the elastomeric sealing element is inhibited from extrusion past the stepped shoulder during

A cup tool for use with a mandrel of a wellhead isolation tool has a substantially right-angled stepped shoulder over which an elastomeric sealing element is forced by elevated fluid pressures. A top end of the elastomeric sealing element is inhibited from extrusion past the stepped shoulder during the insertion of the mandrel, thereby reducing the risk of damaging the sealing element before the mandrel is fully inserted through the wellhead. Once the sealing element is exposed to elevated fluid pressures, the top end of the elastomeric sealing element is forced upwardly over the stepped shoulder, and extruded into an annulus between the mandrel and a well casing or production tubing to provide a high-pressure fluid seal.

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1. A cup tool for providing a high-pressure fluid seal in an annulus between a high pressure mandrel and a casing or a production tubing in a wellbore, comprising:a cup tool tube having a threaded upper end for connection to the high-pressure mandrel; a stepped shoulder at an upper end of the cup to

1. A cup tool for providing a high-pressure fluid seal in an annulus between a high pressure mandrel and a casing or a production tubing in a wellbore, comprising:a cup tool tube having a threaded upper end for connection to the high-pressure mandrel; a stepped shoulder at an upper end of the cup tool tube, the stepped shoulder including at least two substantially right-angled steps; and an elastomeric sealing element that is slidably received on the cup tool tube, the elastomeric sealing element having a top end with a square top edge that engages the stepped shoulder when the elastomeric sealing element is forced upwardly over the cup tool tube by fluid pressure; whereby the top end of the elastomeric sealing element is adapted to be forced upwardly and over one or more of the right-angled steps when the elastomeric sealing element is exposed to elevated fluid pressures, thereby extruding into the annulus in order to provide the high-pressure fluid seal. 2. A cup tool as claimed in claim 1 wherein each of the substantially right-angled steps comprises a radial surface, an axial surface and a rounded edge between the radial and the axial surfaces.3. A cup tool as claimed in claim 1 wherein the elastomeric sealing element is bonded to a cylindrical metal ring having an inner diameter that is sized to slide over an outer diameter of the cup tool tube.4. A cup tool as claimed in claim 3 wherein the cylindrical metal ring includes a groove in an inner periphery thereof that receives an O-ring, which provides a fluid seal between the metal ring and the cup tool tube.5. A cup tool as claimed in claim 4 wherein the elastomeric sealing element comprises a unitary elastomeric cup.6. A cup tool as claimed in claim 5 wherein the unitary elastomeric cup comprises a single elastomer of a consistent durometer.7. A cup tool as claimed in claim 3 wherein the cup tool tube comprises a stop member to restrain downward movement of the elastomeric sealing element on the cup tool tube.8. A cup tool as claimed in claim 1 wherein the cup tool tube has a bottom end that terminates in a bull nose for guiding the cup tool into the tubing.9. A cup tool as claimed in claim 1 wherein the stepped shoulder is integrally formed with the cup tool tube.10. A cup tool as claimed in claim 1 wherein the stepped shoulder is machined into an outer periphery of a gauge ring that is detachable from the threaded upper end of the cup tool tube.11. A cup tool as claimed in claim 10 wherein the gauge ring further comprises a groove in an inner periphery thereof, which accommodates an O-ring for providing a seal between the cup tool tube and the gauge ring.12. A cup tool as claimed in claim 1 further comprising a second cup tool tube, the cup tool comprising first and second axially spaced-apart stepped shoulders and first and second elastomeric sealing elements.13. A gauge ring for a cup tool, comprising:an outer periphery that includes a stepped shoulder having at least two substantially right-angle steps that respectively include a radial surface and an axial surface oriented at a right angle with respect to each other, the right angle steps being mounted above an elastomeric sealing element slidably surrounding a cup tool tube of the cup tool, the right angle steps being configured to inhibit upward movement of the elastomeric sealing element until the elastomeric sealing element is exposed directly or indirectly to fluid pressure high enough to force a square top end of the elastomeric sealing element upwardly over at least one of the right angle steps. 14. The gauge ring as claimed in claim 13 further comprising an inner periphery that includes an annular groove for supporting an O-ring adapted to provide a fluid seal between the gauge ring and a cup tool tube that supports the gauge ring.15. The gauge ring as claimed in claim 13 further comprising an inner periphery that includes a spiral thread adapted to engage a complimentary spiral thread on an outer periphery of one of a cup tool tube and a connector sub adapted to connect the cup tool tube to a high pressure mandrel.16. A cup tool for providing a high-pressure fluid seal in an annulus between a high pressure mandrel and a casing or a production tubing in a wellbore, comprising:a first cup tool tube having a threaded upper end for connection to the high-pressure mandrel; a first stepped shoulder at an upper end of the first cup tool tube, the first stepped shoulder including at least two substantially right-angled steps; a first elastomeric sealing element that is slidably received on the first cup tool tube, the first elastomeric sealing element having a top end with a square top edge that engages the first stepped shoulder when the first elastomeric sealing element is forced upwardly over the first cup tool tube by fluid pressure; a second cup tool tube having a threaded upper end for connection to the first cup tool tube; a second stepped shoulder at an upper end of the second cup tool tube, the second stepped shoulder including at least two substantially right-angled steps; and a second elastomeric sealing element that is slidably received on the second cup tool tube, the second elastomeric sealing element having a top end with a square top edge that engages the second stepped shoulder when the second elastomeric sealing element is forced upwardly over the second cup tool tube by fluid pressure; whereby the top end of the respective first and second elastomeric sealing elements is adapted to be forced upwardly against and over one or more of the respective right-angled steps when the elastomeric sealing element is exposed to elevated fluid pressures, thereby extruding into the annulus in order to provide the high-pressure fluid seal. 17. A cup tool as claimed in claim 16 wherein the elastomeric sealing elements are unitary elastomeric cups.18. A cup tool as claimed in claim 17 wherein the elastomeric sealing elements are bonded to respective cylindrical metal ring sized to slide reciprocally on the respective first and second cup tool tubes, the cylindrical metal rings respectively including an inner peripheral groove adapted to support an O-ring for providing a fluid seal between the elastomeric sealing element and the respective cup tool tube.19. A cup tool as claimed in claim 17 wherein the unitary elastomeric cups comprise a single elastomer of a consistent durometer of hardness.20. A cup tool as claimed in claim 16 further comprising a bullnose that terminates the second cup tool tube, the bullnose being adapted to guide the cup tool through a wellhead as the high pressure mandrel is inserted therethrough.21. A cup tool as claimed in claim 16 wherein the first and second stepped shoulders at a top end of the respective first and second cup tool tubes comprises a gauge ring that is detachably supported at a top of the respective first and second cup tool tubes.