Mid-seal for expandable connections
View Patent ↗An expandable tubular connection includes a pin member and a box member. The pin member includes a pin thread formed on a small step and a large step and a first seal surface formed between the small step and the large step. The box member includes a box thread formed on a small step and a large step and a second seal surface formed between the small step and the large step. The pin thread and the box thread are wedge threads. Upon a selected make-up of the pin member with the box member a selected gap exists between the first seal surface and the second seal surface. The gap is selected such that, when plastically radially expanded by a selected amount, a seal is formed between at least a portion of the first seal surface and the second seal surface.
1. An expandable tubular connection, comprising:
a pin member comprising a pin wedge thread formed on a small step and a large step;
a box member comprising a box wedge thread formed on a small step and a large step;
a first seal surface formed between the small step and the large step of the pin thread;
a second seal surface formed between the small step and the large step of the box thread;
wherein, upon selected makeup of the pin member with the box member, a selected gap exists between the first seal surface and the second seal surface.
2. The expandable tubular connection of claim 1 , wherein upon plastic radial expansion of the tubular connection, the first and second seal surfaces are configured so that a contact seal is formed therebetween.
3. The expandable tubular connection of claim 1 , wherein the small step and the large step of both the pin member and the box member are formed on a single taper.
4. The expandable tubular connection of claim 1 , further comprising:
a gap between a pin thread crest and a box thread root at the selected make-up.
5. The expandable tubular connection of claim 4 , wherein the gap between the pin thread crest and the box thread root is configured such that a desired interference is formed therebetween upon plastic radial expansion of the expandable tubular connection.
6. An expandable tubular connection comprising:
a pin member comprising,
a pin thread formed on a small step and a large step, and
a first seal surface formed between the small step and the large step;
a box member comprising,
a box thread formed on a small step and a large step, and
a second seal surface formed between the small step and the large step;
wherein the pin thread and the box thread are wedge threads,
a selected gap located between the first seal surface and the second seal surface upon a selected make-up of the pin member with the box member; and
wherein contact between the first and the second seal surfaces forms a seal after plastic radial expansion of the expandable tubular connection.
7. The expandable tubular connection of claim 6 , further comprising a sealing element disposed between the small step and the large step of one of the pin member and the box member, wherein the elastomeric sealing element provides a seal at the selected make-up.
8. The expandable tubular connection of claim 6 , wherein the pin thread and the box thread have a trapped thread form.
9. The expandable tubular connection of claim 6 , wherein one of the first seal surface and the second seal surface is frustoconical and the other is curved.
10. The expandable tubular connection of claim 6 , wherein one of the first seal surface and the second seal surface comprises two surfaces that intersect to form a sealing line.
11. The expandable tubular connection of claim 6 , further comprising:
a gap between a pin thread crest and a box thread root upon selected make-up of the pin member with the box member; and
wherein the pin thread crest and the box thread root are in contact and form a seal after plastic radial expansion of the expandable tubular connection.
12. The expandable tubular connection of claim 6 , wherein one of the first seal surface and the second seal surface is cylindrical.
13. The expandable tubular connection of claim 6 , wherein the first seal surface and the second seal surface are frustoconical and have different angles relative to a central axis of the connection.
14. The expandable tubular connection of claim 6 , further comprising:
a strain focusing groove formed on an outer diameter of the box member at an overlapping axial position with the second seal surface.
15. The expandable tubular connection of claim 6 , wherein the small step and the large step of both the pin member and the box member are formed on a single taper.
16. The expandable tubular connection of claim 15 , wherein the single taper is less than about 10 degrees.
17. The expandable tubular connection of claim 16 , wherein the single taper is between about 2 degrees and about 5 degrees.