Plug for a coiled tubing string

A combination of a coiled tubing string, a tubing plug, and a setting tool is provided. The tubing plug has an inner mandrel with a movable, first stop toward a first end and a fixed second stop at a second end. As the first stop moves toward the second stop first and second seal ramps cause first and second elastomeric seals to seal against an inner surface of the coiled tubing string, and anchor ramps cause expandable anchors to expand and engage the inner surface of the coiled tubing string.

TECHNICAL FIELD

This relates to a plug for a tubing string, and in particular, a plug for a coiled tubing string.

BACKGROUND

Tubing strings are often used to convey fluids at high pressure in downhole operations. In some cases, it may become necessary to seal the tubing string at a location along its length. To seal the tubing string, tubing plugs may be inserted into the string, lowered to the desired location, and activated from a collapsed state to a sealing state. U.S. Pat. No. 3,412,803 (Stachowiak) entitled “Well tool anchors” describes an example of a tubing plug. U.S. Pat. No. 7,631,693 (Tong et al.) entitled “Retrievable plug system and methods of use” describes an example of a plug system designed for use in coiled tubing.

SUMMARY

According to an aspect, there is provided, in combination, a coiled tubing string having an inner surface that comprises a longitudinal seam and a tubing plug for sealing the interior of the coiled tubing string, the tubing plug comprising an inner mandrel having a first end, a second end, and a longitudinal axis that extends between the first end and the second end, the inner mandrel having a setting tool connection at the first end, a first stop slidably mounted to the mandrel toward the first end, and a second stop fixedly mounted to the mandrel toward the second end, a seal ramp section carried by the inner mandrel, the seal ramp section comprising a first seal ramp that slopes inward and toward the first end of the inner mandrel, and a second seal ramp that slopes inward and toward the second end of the inner mandrel, a first elastomeric seal adjacent to the first seal ramp and a second elastomeric seal adjacent to the second seal ramp, the first elastomeric seal and the second elastomeric seal each having a first end facing toward the seal ramp section and a second end facing away from the seal ramp section, a first anchor ramp adjacent to the first elastomeric seal toward the first end of the inner mandrel, and a second anchor ramp adjacent to the second elastomeric seal toward the second end of the inner mandrel, and a first expandable anchor between the first stop and the first anchor ramp, and a second expandable anchor between the second stop and the second anchor ramp, wherein, as the first stop moves toward the second stop along the inner mandrel the first elastomeric seal and the second elastomeric seal move along the first seal ramp and the second seal ramp, respectively, such that the seal ramp section causes the first elastomeric seal and the second elastomeric seal to expand outward into sealing engagement with the inner surface of the coiled tubing string and the longitudinal seam of the inner surface, the first anchor ramp and the second anchor ramp cause the first expandable anchor and the second expandable anchor, respectively, to move out and engage the inner surface of the coiled tubing, and a setting tool for setting the tubing plug, the setting tool being connected to apply a force to move the first stop toward the second stop.

According to other aspects, the second end of each of the first elastomeric seal and the second elastomeric seal may be tapered, and the tubing plug may further comprises a first anti-extrusion assembly adjacent to the tapered end of the first elastomeric seal between the first elastomeric seal and the first anchor ramp, and a second anti-extrusion assembly adjacent to the tapered end of the second elastomeric seal between the second elastomeric seal and the second anchor ramp, the first anti-extrusion assembly and the second anti-extrusion assembly being movable relative to the inner mandrel, as the first stop moves toward the second stop along the inner mandrel, the tapered end of the first elastomeric seal and the tapered end of the second elastomeric seal may cause the first anti-extrusion assembly and the second anti-extrusion assembly, respectively, to expand outward toward the inner surface of the coiled tubing string, the first anti-extrusion assembly and the second anti-extrusion assembly forming a chamber that contains and prevents extrusion of the first elastomeric seal and the second elastomeric seal, the elastomer ramp section may comprise a central apex between the first seal ramp and the second seal ramp, the first anti-extrusion assembly and the second anti-extrusion assembly may each comprise overlapping petalloid extensions, the first anti-extrusion assembly and the second anti-extrusion assembly may each further comprise an elastomeric support positioned between the overlapping petalloid extensions and the first elastomeric seal and the second elastomeric seal, and the elastomeric support may have a hardness greater than the first elastomeric seal and the second elastomeric seal, and an outer surface of the inner mandrel may further comprise a ratcheting surface and the first stop comprises a ratchet engagement profile that permits movement of the first stop toward the second stop and prevents movement of the first stop away from the second stop.

According to an aspect, there is provided a method of sealing a coiled tubing string comprising a longitudinal seam, the method comprising the steps of providing a tubing plug for sealing the interior of the coiled tubing string, the tubing plug comprising an inner mandrel having a first end, a second end, and a longitudinal axis that extends between the first end and the second end, the inner mandrel having a setting tool connection at the first end, a first stop slidably mounted to the mandrel toward the first end, and a second stop fixedly mounted to the mandrel toward the second end, a seal ramp section carried by the inner mandrel, the seal ramp section comprising a first seal ramp that slopes inward and toward the first end of the inner mandrel, and a second seal ramp that slopes inward and toward the second end of the inner mandrel, a first elastomeric seal adjacent to the first seal ramp and a second elastomeric seal adjacent to the second seal ramp, the first elastomeric seal and the second elastomeric seal having a first end facing toward the seal ramp section and a second end facing away from the seal ramp section, a first anchor ramp adjacent to the first elastomeric seal toward the first end of the inner mandrel, and a second anchor ramp adjacent to the second elastomeric seal toward the second end of the inner mandrel, and a first expandable anchor between the first stop and the first anchor ramp, and a second expandable anchor between the second stop and the second anchor ramp, positioning the tubing plug at a location to be sealed within the coiled tubing string, and applying a force to move the first stop toward the second stop such that: the first elastomeric seal and the second elastomeric seal move along the first seal ramp and the second seal ramp, respectively, such that the seal ramp section causes the first elastomeric seal and the second elastomeric seal to expand outward into sealing engagement with the inner surface of the coiled tubing string and the longitudinal seam of the inner surface, and the first anchor ramp and the second anchor ramp cause the first expandable anchor and the second expandable anchor, respectively, to move out and engage the inner surface of the coiled tubing.

According to other aspects, the second end of each of the first elastomeric seal and the second elastomeric seal may be tapered, and the tubing plug may further comprise a first anti-extrusion assembly adjacent to the tapered end of the first elastomeric seal between the first elastomeric seal and the first anchor ramp, and a second anti-extrusion assembly adjacent to the tapered end of the second elastomeric seal between the second elastomeric seal and the second anchor ramp, the first anti-extrusion assembly and the second anti-extrusion assembly being movable relative to the inner mandrel, wherein as the first stop moves toward the second stop along the inner mandrel, the tapered end of the first elastomeric seal and the tapered end of the second elastomeric seal may cause the first anti-extrusion assembly and the second anti-extrusion assembly, respectively, to expand outward toward the inner surface of the coiled tubing string, the first anti-extrusion assembly and the second anti-extrusion assembly forming a chamber that contains and prevents extrusion of the first elastomeric seal and the second elastomeric seal, the seal ramp section may comprise a central apex between the first seal ramp and the second seal ramp, the first anti-extrusion assembly and the second anti-extrusion assembly may each comprise overlapping petalloid extensions, the first anti-extrusion assembly and the second anti-extrusion assembly may each further comprise an elastomeric support positioned between the overlapping petalloid extensions and the first elastomeric seal and the second elastomeric seal, and the elastomeric support may have a hardness greater than the first elastomeric seal and the second elastomeric seal, and an outer surface of the inner mandrel may further comprise a ratcheting surface and the first stop comprises a ratchet engagement profile that permits movement of the first stop toward the second stop and prevents movement of the first stop away from the second stop.

In other aspects, the features described above may be combined together in any reasonable combination as will be recognized by those skilled in the art.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A tubing plug, generally identified by reference numeral10, will now be described with reference toFIG. 1 through 7. Tubing plug10is designed to be inserted into a length of coiled tubing50, where it is activated by a setting tool70to sealingly engage an inner surface52of coiled tubing50. Coiled tubing50is generally used as a spoolable, continuous tubing string and therefore may be any length. Due to the way in which coiled tubing is manufactured, it generally has a longitudinal seam54, shown inFIG. 5, which extends along the length of coiled tubing50and typically protrudes inward away from inner surface52of coiled tubing50. Coiled tubing50is typically cylindrical with a diameter of between 1 and 3.25 inches, although it may be manufactured with other diameters, depending on the intended application. It will be understood that the relative dimensions of tubing plug10will be selected to correspond with those of coiled tubing50. As will be described below, tubing plug10is designed to be generally cylindrical and to seal within coiled tubing50against inner surface52and longitudinal seam54, as shown inFIG. 7, and to accommodate and seal against the uneven profile resulting from longitudinal seam54.

Referring toFIG. 2, tubing plug10is supported by an inner mandrel12, which has a first end14, a second end16, and a longitudinal axis19that extends between first and second ends14and16. Inner mandrel12has a setting tool connection15at a first end14, and carries a first stop17and a second stop18. Second stop18is fixedly mounted to inner mandrel12toward second end16of inner mandrel, while first stop17is slidably mounted to inner mandrel12toward first end14of inner mandrel12. Second stop18may be machined as an integral part of mandrel12or it may be attached to mandrel12after being manufactured. Various sleeves are slidably mounted coaxially on mandrel12between first stop17and second stop18. As will be described below, the sleeves each have specific characteristics and are used to set and seal plug10when activated.

As shown, setting tool connection15is a threaded, shearable component that allows setting tool70to set plug10by application of a setting force to first stop17relative to inner mandrel12, and then disconnect from plug10upon application of a breakaway force that causes connection15to break away from the remainder of inner mandrel12. Different types of connections may also be used as will be known in the art that allow setting tool70to set plug10, and preferably, to disconnect thereafter for retrieval. This may be done using either longitudinal or rotational forces. The depicted example does not include the details of setting tool70, as various designs are well known in the art that are capable of applying a differential force between setting tool connection15and first stop17to activate plug10to the sealed state. For example, setting tool70may have an outer sleeve that applies a force to first stop17, while an inner connection point is secured to setting tool connection15to hold it in place as first stop17moves along longitudinal axis19toward second stop18to set tubing plug10. It is common to accomplish this using hydraulics to apply a differential pressure that causes the sleeve to slide downward, however other designs may use other motive forces.

Referring toFIGS. 4 and 6, first stop17includes a ratchet nut42that is used to hold first stop17in place after plug10is actuated. Referring toFIG. 3, ratchet nut42has an inner profile that engages a ratcheting surface40on mandrel12that allows movement toward second stop19, while resisting movement in the opposite direction. Designs of suitable ratchets are known in the art and will not be described further.

Referring toFIG. 2, the slidable sleeves are symmetrically and slidably positioned along longitudinal axis19on either side of a seal ramp section22. Seal ramp section22is a rigid sleeve that has a raised section24in its middle and two seal ramp sections25and27that taper down and away from the middle section. As shown, ramp sections25and27are in the form of two frusto-conical sections that meet at a central apex26with the circumference of the raised section continuously decreasing from apex26toward both first end14and second end16of inner mandrel12, as depicted inFIG. 1. Elastomeric seals21and23are positioned axially above and below seal ramp sections25and27, such that a first elastomeric seal21is adjacent to first seal ramp25and second elastomeric seal23is adjacent to second seal ramp27. Elastomeric seals21and23are made of an elastomeric material capable of forming a sealing engagement between inner surface52and elastomer ramp section22. Elastomeric seals21and23may be required to seal around longitudinal seam of inner surface52, if present. When an activation force is applied and a compressive force applied to the slidable sleeves, first and second elastomeric seals21and23will slide along seal ramp sections25and27, causing them to push outward and form a compressive seal between raised section24and inner surface52that is capable of withstanding pressures applied within coiled tubing string50. It will be understood that each elastomeric seal21or23may be made as a single piece, or may be made from multiple distinct pieces of elastomeric material that make up elastomeric seals21and23. Elastomeric seals21and23may, for example, be composite seals formed of elastomers of differing hardness in order to provide different sealing dynamics. This may allow a suitable seal to be manufactured that interacts differently, for example, with ramp sections25and27, with inner surface52of coiled tubing string50, and/or with anchor ramps31and33described below, or that has a different density and material characteristics within the core of elastomeric seals21and23.

First and second anchor ramps31and33are provided opposite elastomeric seals21and23relative to seal ramp section22. Anchor ramps31and33may have a first end34towards elastomeric seals21and23, and a second end36opposite first end34towards first or second end14or16of mandrel14, respectively, where first end34has a smaller diameter than second end36. Anchor ramps31and33have a sloped surface37positioned between first end34and second end36. Sloped surface37preferably has a slope that continuously decreases. Anchor ramps31and33may also include a flat portion adjacent to sloped surface37, as shown.

First and second expandable anchors39and41are positioned adjacent and opposite to anchor ramps31and33relative to ramp section22, such that first expandable anchor39is between first stop17and first anchor ramp31, and second expandable anchor41is between second stop18and second anchor ramp33. When tubing plug10is set, expandable anchors39and41move over top of anchor ramps31and33, respectively, and expand outward to engage inner surface52of coil tubing50. When engaged with inner surface52, expandable anchors39and41have an outer profile that resists movement along longitudinal axis19such that tubing plug10is secured against lateral movement within coil tubing50. As shown, expandable anchor39has an engagement profile that resists movement in the opposite direction of expandable anchor41.FIG. 6shows tubing plug10in its set state, with expandable anchors39and41and seals21and23engaged with coiled tubing50. Referring toFIG. 7, where coiled tubing50has inner seam54, elastomeric seals21and23deform around inner seam54of coiled tubing50to provide a fluid impermeable seal capable of withstanding high pressures in coiled tubing50.

Referring toFIG. 6, anti-extrusion surfaces30may be positioned axially above and below elastomeric seals21and23to protect elastomeric seals21and23against extrusion that may occur with expandable anchors39and41. When tubing plug10is set, anti-extrusion surfaces30engage the upper and lower edges of elastomeric seals21and23, preventing the elastomeric material from extruding away from elastomer ramp section22. Anti-extrusion surfaces30may include either a ring that engages elastomeric seals21and23, petalloid extensions that engage elastomeric seals21and23, or a combination of both a ring and petalloid extensions. In order to further reduce extrusion of elastomeric seals21and23, there may also be two elastomeric supports29provided axially above and axially below seals21and23, as shown inFIG. 4. As elastomeric supports29are more likely to be exposed to the high pressure fluid in coiled tubing50, they may be formed from an elastic material that is resistant to extrusion, such as an elastomer that has a greater hardness than the elastomer that forms elastomeric seals21and23. Seals29may be provided to act between anti-extrusion surfaces30, where seals29are sufficiently stiff to resist extruding through or around anti-extrusion surfaces30, but soft enough to expand and prevent seals21and23from extruding around seals29. Anti-extrusion surface30and seal29may be used together to form an anti-extrusion assembly. After being set, elastomeric supports29may be compressed between inner seals21and23and anti-extrusion surfaces30. Anchor ramps31and33may be positioned axially above, axially below, and adjacent to anti-extrusion surfaces30and engage anti-extrusion surfaces30when tubing plug10is set.

Referring toFIG. 3, in addition to connection15, inner mandrel12has a locking mechanism that restrains first stop17once actuated. As shown, the locking mechanism is a ratcheting surface40near first end14, adjacent to connection15, and positioned between connection15and second end16that engages a ratchet nut42. This allows first stop17to be locked into place at a location along ratcheting surface40to set tubing plug10and hold the various components in a compressed state along the axis of tubing plug10, causing the components to expand outward.

Tubing plug10is set by setting tool70, which may be threadably connected to tubing plug10at connection15of first end14of inner mandrel12. Setting tool70may be run on a suitable elongate member that fits within coiled tubing50, such as a tubing string, and allows an operator to position tubing plug10within coiled tubing50and set tubing plug10. Setting tool70applies a force to first stop17of tubing plug10and compresses the slidable sleeves to set tubing plug10. When setting tool70is activated, it will provide a force that compresses the slidable sleeves axially together between stops17and18, such that expandable anchors39and41expand as they move along anchor ramps31and33to engage inner surface52of coiled tubing string50. Anchor ramps31and33may engage anti-extrusion surfaces30, if provided, and anti-extrusion surfaces30may engage seals21and23, such that seals21and23overlie raised section24of elastomer ramp section22and sealingly engage inner surface52. Seals21and23may also be directly engaged by anchor ramps31and33. Anti-extrusion surfaces30may prevent seals21and23from extruding back toward anchor ramps31and33. In the depicted example, the slidable sleeves are held in the deployed state by stop18at second end16and first stop17and ratchet nut42that is locked into place along ratcheting surface40.FIG. 3shows ratchet nut42and how it may be locked into place on ratcheting surface40. The slidable sleeves may also be held in the compressed state by other types of locking mechanisms, as are known in the art.

The method for sealing coiled tubing50has the following steps: tubing plug10, described above, is provided and has setting tool70connected to its first end14. Tubing plug10is inserted into coiled tubing50and positioned at a location within coiled tubing50that is to be sealed, and setting tool70is activated, causing the plurality of slidable sleeves to be compressed together, as described above and depicted inFIG. 6. As first stop17is slidable and allows for compression of the slidable sleeves, while second stop18is fixed relative to inner mandrel12, first and second stop17and18are moved closer together, which causes elastomeric seals21and23to move along seal ramp section22, forcing them outwards towards inner surface52. Expandable anchors39and41move along anchor ramps31and33and expand outwards towards inner surface52. The compression of the slidable sleeves results in elastomeric seals21and23sealing the interior of coiled tubing50, providing a high pressure tolerant, fluid impermeable seal that accommodates seam54, as depicted inFIG. 7, while expandable anchors39and41are engage inner surface52of coiled tubing50, and anchor tubing plug10in a fixed location. Expandable anchors39and41may, for example, have a plurality of ridges or teeth, as shown inFIG. 1, that are capable of engaging inner surface52sufficiently to prevent movement of tubing plug10in high pressure scenarios. For example, the ridges or teeth may bite into or deform the inner surface52sufficiently to provide an engagement surface that resists movement of tubing plug10.

The scope of the following claims should not be limited by the preferred embodiments set forth in the examples above and in the drawings, but should be given the broadest interpretation consistent with the description as a whole.