HIGH INTEGRITY HANGER AND SEAL FOR CASING
Casing segments and an expansion cone are positioned and cemented within a new section of a wellbore with a lower casing segment in an overlapping relationship with an upper casing segment. The lower casing segment is radially expanded such that an upper end of the lower casing segment comes into contact with the interior wall of the upper casing segment at the overlap region. The upper casing segment has an inward facing profile at the overlap region that includes a set of wickers that are driven into the lower casing exterior when it is expanded. This forms a metal-to-metal seal between the upper and lower casing segments at the overlap region.
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This invention relates in general to wellbore casing or liner and in particular to a high integrity hanger and seal used in casing while drilling operations.
BACKGROUND OF THE INVENTIONIn conventional well drilling, several casings 12, 14 are installed in the well borehole 10 to maintain the integrity of the borehole wall, as shown in
The casing 14 to be installed in a lower segment may be hung at the wellhead 16 as shown in
To try and remedy the issues with the nested casing arrangement, expandable tubulars have been employed for the sections of casing, or liner, below the upper section of casing. The subsequent expandable tubular is lowered into a portion of the well drilled out below the upper casing. Once in place, the tubular is expanded radially such that the bore diameter is approximately slightly less that of the upper casing. An overlap exists between the upper and lower casing segments that creates a seal between the segments when the tubular is expanded. However, due to well pressure and thermal growth, the seal may lose integrity.
A need exists for a technique that addresses one or more of the limitations of the existing procedures for forming new sections of casing in a wellbore. The following technique may solve these problems.
SUMMARY OF THE INVENTIONIn an embodiment of the present technique, a casing may be comprised of a plurality of casing segments joined approximately end to end, with each casing segment comprising a wicker profile formed on the interior surface at one end of the casing segment. Once the casing segment is cemented in place within the well borehole, a subsequent casing segment having a smaller diameter than that of the cemented casing may be lowered on a drill string through the initial, cemented casing. The drill string may extend past the lower end of the subsequent, lower casing where a bottom hole assembly (“BHA”) is attached to the drill string. The BHA may comprise a drilling head and an underreamer. The drilling head and underreamer rotate during drilling operations to drill a desired length below the end of the initial casing segment. Once the drilling operation is complete, the BHA may be retrieved and the subsequent casing is cemented in place in a conventional manner such that a portion of the subsequent casing segment overlaps with the wicker profile of the initial, upper casing segment.
In an illustrated embodiment, a pig or expandable cone may then be run into the bore of the lower, subsequent casing on a string to radially expand the lower casing along its length. As the lower casing segment is radially expanded by the pig, the portion of the lower casing segment that overlaps with the wicker profile of the upper casing is deformed onto the wicker profile to form a metal-to-metal seal. The wicker profile bites into the exterior surface of the subsequent casing segment In addition to forming a high integrity metal to metal seal, the wicker mechanism can function as a casing hanger while the cement cures. The procedure described above may be repeated until the desired length of casing is installed.
The combination of the wicker profile, and the radial expansion of each subsequent casing segment to form a metal-to-metal seal against the wicker profile, improves sealing between casing segments while reducing the telescoping and borehole reduction effect.
Referring to
An overlap region, tubular seal section, or packoff 32, shown in more detail in
Referring to
During casing operations as shown in
The wellbore will be drilled deeper, either with a drill pipe string or by liner drilling. Continuing to refer to
As shown in
The exterior surface 38 of the lower casing may be formed of a softer metal than that of the wickers 40 or wickers 40 may contain an inlay of soft metal. Further, the wickers 40 may be formed from a different type of metal that is harder than that of the rest of the upper casing 28, such as Inconel® 725. The yield strength of carbon steel casing is approximately 55 to 110 ksi, depending on the application. The wickers may have 120 ksi minimum yield strength and a hardness can vary between roughly less than 20 Rockwell C (“HRC”) to greater than roughly 37 HRC. The higher hardness of the wickers 40 ensures biting into the lower casing 28 overlap region. In addition, any portion of the lower casing segment 28 that remains above the overlap region 32 may be cut-off and removed, if desired. No additional sealing or pachoffs are required. The procedure described above may be repeated to install additional liner strings. Further, each metal-to-metal seal formed may be tested by pressurizing the interior of the casing and observing any drop in pressure.
While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention.
Claims
1. An apparatus for forming a wellbore casing in a well, comprising:
- an upper casing segment cemented within the well;
- a wicker profile formed at an interior end of the upper casing segment;
- a lower casing segment installed within the well; and
- an upper end on the lower casing segment that overlaps with and is radially deformed into the wicker profile on the upper casing segment, to create a metal-to-metal seal.
2. The apparatus of claim 1, further comprising a circumferential recess formed adjacent to wicker profile on the interior of the initial casing segment, and a portion of the upper end of the lower casing segment is radially deformed into the recess.
3. The apparatus of claim 2, wherein the wicker profile comprises a plurality of parallel, circumferential grooves, each of the grooves being triangular in configuration.
4. The apparatus of claim 1, wherein after being radially deformed, the upper end of the lower casing segment has an inner diameter substantially equal to a nominal inner diameter of the upper casing segment.
5. The apparatus of claim 1, further comprising an upper and a lower circumferential recess formed above and below the wicker profile on the interior of the initial casing segment, and a portion of the upper end of the lower casing segment is radially deformed into the recesses.
6. The apparatus of claim 1, wherein a full length of the lower casing segment is radially expanded to a nominal inner diameter equal to a nominal inner diameter of the upper casing segment.
7. The apparatus of claim 1, wherein an outer surface on the end of the lower casing segment is fabricated from a metal that is softer than the wicker profile.
8. The apparatus of claim 1, wherein the wicker profile comprises a plurality of parallel, triangular shaped grooves, the grooves being fabricated of a harder metal than that of the upper casing segment, the wicker profile being joined to the upper casing segment.
9. The apparatus of claim 1, wherein the upper casing segment is cemented within the well at the approximate location where the end on the subsequent casing segment overlaps with the wicker profile.
10. An apparatus for forming a wellbore casing in a well, comprising:
- an upper casing segment cemented within the well;
- a wicker profile formed at an interior end of the upper casing segment, wherein the wicker profile comprises a plurality of parallel, circumferential grooves, each of the grooves being triangular in configuration, and wherein the grooves are fabricated of a harder metal than that of the upper casing segment, the wicker profile being joined to the upper casing segment;
- a lower casing segment installed within the well, wherein an outer surface on the end of the lower casing segment is fabricated from a metal that is softer than the wicker profile; and
- an upper end on the lower casing segment that overlaps with and is radially deformed into the wicker profile on the upper casing segment, to create a metal-to-metal seal.
11. The seal assembly of claim 10, further comprising a circumferential recess formed adjacent to wicker profile on the interior of the initial casing segment, and a portion of the upper end of the lower casing segment is radially deformed into the recess.
12. The apparatus of claim 10, wherein after being radially deformed, the upper end of the lower casing segment has an inner diameter substantially equal to a nominal inner diameter of the upper casing segment.
13. The apparatus according to claim 10, further comprising an upper and a lower circumferential recess formed above and below the wicker profile on the interior of the initial casing segment, and a portion of the upper end of the lower casing segment is radially deformed into the recesses.
14. The apparatus of claim 10, wherein a full length of the lower casing segment is radially expanded to a nominal inner diameter equal to a nominal inner diameter of the upper casing segment.
15. The apparatus of claim 10, wherein the lower casing segment is cemented within the well at the approximate location where the end on the lower casing segment overlaps with the wicker profile.
16. A method of creating a wellbore casing in a well, comprising:
- forming a wicker profile at an interior end of an upper casing segment;
- installing and cementing the upper casing segment in the wellbore;
- installing a lower casing segment at a lower depth than the upper casing segment so that an end of the lower casing segment overlaps with the wicker profile on the upper casing segment; and
- radially expanding at least a portion of the subsequent casing segment to create a metal-to-metal seal between the upper and lower casing segments at the point where the upper and lower casing segments overlap.
17. The method of claim 16, further comprising the steps of:
- drilling a predetermined depth below the end of the upper casing to create an open hole that accommodates the lower casing segment;
- cementing the lowert casing segment prior to radially expanding the lower casing segment; and
- pressurizing the bore of the casing to test for leakage at the metal-to-metal seal.
18. The method of claim 16, wherein radially expanding at least a portion of the lower casing segment is by an expansion tool.
19. The method of claim of 16, wherein forming a wicker profile comprises forming the wicker profile of a harder metal than a metal of the upper end of the lower casing segment.
Type: Application
Filed: Jun 17, 2010
Publication Date: Dec 22, 2011
Applicant: VETCO GRAY INC. (Houston, TX)
Inventor: Stephen Paul Fenton (Balmedie)
Application Number: 12/817,986
International Classification: E21B 43/10 (20060101); E21B 33/14 (20060101); E21B 47/10 (20060101); E21B 47/00 (20060101); E21B 23/01 (20060101); E21B 17/00 (20060101);