Method and apparatus for expanding a liner patch

This invention relates to downhole sealing, and to an apparatus and method for use in forming an arrangement to allow creation of a downhole seal. In particular, but not exclusively, the invention relates to the provision of a seal or packer between concentric downhole tubing, such as bore-lining casing and production casing.

In the oil and gas exploration and production industry, bores are drilled to access hydrocarbon-bearing rock formations. The drilled bores are lined with steel tubing, known as casing, which is cemented in the bore. Oil and gas are carried from the hydrocarbon-bearing or production formation to the surface through smaller diameter production tubing which is run into the fully-cased bore. Typical production tubing incorporates a number of valves and other devices which are employed, for example, to allow the pressure integrity of the tubing to be tested as it is made up, and to control the flow of fluid through the tubing. Further, to prevent fluid from passing up the annulus between the inner wall of the casing and the outer wall of the production tubing, at least one seal, known as a packer, may be provided between the tubing and the casing. The tubing will normally be axially movable relative to the packer, to accommodate expansion of the tubing due to heating and the like. The packer may be run in separately of the tubing, or in some cases may be run in with the tubing. In any event, the packer is run into the bore in a retracted or non-energised position, and at an appropriate point is energised or "set" to fix the packer in position and to form a seal with the casing. A typical packer will include slips which grip the casing wall and an elastomeric sealing element which is radially deformable to provide a sealing contact with the casing wall and which energises the slips. Accordingly, a conventional packer has a significant thickness, thus reducing the available bore area to accommodate the production tubing. Thus, to accommodate production tubing of a predetermined diameter, it is necessary to provide relatively large diameter casing, and thus a relatively large bore, with the associated increase in costs and drilling time. Further, the presence of an elastomeric element in conventional packers limits their usefulness in high temperature applications.

US 4083408 describes a well completion apparatus in which two seal assemblies are used. Each comprises a polished bore receptacle and anchoring system.

US 3282346 describes an expandable packing and anchoring element.

It is among the objectives of embodiments of the present invention to provide a means of sealing production tubing relative to casing which obviates the requirement to provide a conventional packer, by providing a relatively compact or "slimline" sealing arrangement which does not require the provision of slips and elastomeric elements to lock the arrangement in the casing.

In accordance with one aspect of the present invention there is provided a method of providing a downhole seal in a wellbore having a lined portion, the method comprising:

• running a first tubular into a wellbore, the first tubular having a polished bore portion and an expandable portion, the expandable portion having a thinner wall than the polished bore portion;
• suspending the first tubular at a selected depth within the wellbore, wherein at least the expandable portion of the first tubular is in an overlapping relationship with the lined portion of the wellbore; and
• expanding the expandable portion of the first tubular into frictional engagement with the lined portion of the wellbore.

The invention thus permits the formation of a seal between inner and outer tubing without requiring the provision of a conventional packer or the like externally of the inner tubing.

In accordance with a second aspect of the present invention there is provided a tubular for use in a wellbore, comprising an expandable portion expandable by a radial outward force applied from an interior thereof, and a polished bore portion having a polished bore receptacle formed therein, the expandable portion having a thinner wall than the polished bore portion.

Further aspects and preferred features are set out in claim 2 et seq.

These and other aspects of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

• Figures 1 to 5 are schematic sectional views of apparatus for use in forming a downhole arrangement for permitting sealing between inner tubing and outer tubing utilising an intermediate tubing section, and showing stages in the formation of the downhole arrangement;
• Figure 6 is an enlarged perspective view of the apparatus of Figure 1;
• Figure 7 is an exploded view corresponding to Figure 6;
• Figure 8 is a sectional view of the apparatus of Figure 6; and
• Figures 9 and 10 are schematic sectional views of apparatus for use in forming a downhole sealing arrangement.

Reference is first made to Figures 1 of the drawings, which illustrated apparatus in the form of an expander device 10 for use in forming a downhole arrangement 12 (Figure 5) for permitting provision of a seal between inner tubing, in the form of production tubing 11 (Figure 5), and outer tubing, in the form of bore-lining casing 16, utilising an intermediate tubing section 18. In Figure 1 the device 10 is illustrated located within the tubing section 18 and is intended to be run into a casing-lined bore, with the section 18, on an appropriate running string 20. A running mandrel 22 extends from the lower end of the device 10, and extends from the lower end of the tubing section 18.

The general configuration and operation of the device 10, and the "setting" of the tubing section 18, will be described initially with reference to Figures 1 to 5 of the drawings, followed by a more detailed description of the device 10.

The device 10 comprises an elongate body 24 which carries three radially movable rollers 26. The rollers 26 may be urged outwards by application of fluid pressure to the body interior, via the running string 20. Each roller 26 defines a circumferential rib 28 which, as will be described, provides a high pressure contact area. The device 10 is rotatable in the bore, being driven either from surface via the string 20, or by an appropriate downhole motor.

The tubing section 18 comprises an upper relatively thin-walled hanger seal portion 30 and, welded thereto, a thicker walled portion 32 defining a polished bore 34. Once the tubing section 18 has been set in the casing 16, the polished bore 34 allows an appropriate section of the production tubing 11, typically carrying sealing bands, to be located within the bore 34 and form a fluid-tight seal therewith.

The seal portion 30 carries three axially-spaced seal rings or bands 36 of ductile metal. Further, between the bands 36, the seal portion 30 is provided with grip banding 37 in the form of carbide grit 38 held in an appropriate matrix.

To set the tubing section 18 in the casing 16, the device 10 and tubing section 18 are run into the casing-lined bore and located in a pre-selected portion of the casing 16, as shown in Figure 1. At this point the tubing section 18 may be coupled to the device 10, running mandrel 22 or running string 20, by an appropriate releasable connection, such as a shear ring. The outer diameter of the tubing section 18 and the inner diameter of the casing 16 where the section 18 is to be located are closely matched to provide limited clearance therebetween.

Fluid pressure is then applied to the interior of the device body 24, causing the three rollers 26 to extend radially outwardly into contact with the inner surface of the adjacent area of the seal portion 30. The rollers 26 deform the wall of the seal portion 30 (to a generally triangular form) such that the outer surface of the tubing section 18 comes into contact with the inner surface of the casing 16 at three areas corresponding to the roller locations. Further, the pressure forces created by the rollers 26 may be sufficient to deform the casing 16, thus creating corresponding profiles to accommodate the radial extension of the intermediate tubing section 18. The carbide grit 38 carried by the sealing section 30 is pressed into the softer material of the opposing tubing surfaces, keying the surfaces together.

This initial deformation of the intermediate tubing section 18 is sufficient to hold the tubing section 18 against rotation relative to the casing 16.

The device 10 is then rotated relative to the tubing section 18 with the rollers 26 in rolling contact with the inner surface of the sealing portion 30, to create an annular extension 40a in the sealing portion 30 and a corresponding profile 42a in the casing 16, as shown in Figure 2. The deformation of the sealing portion 30 is by rolling expansion, that is the rollers 26 are rotated within the sealing portion 30 with the ribs 28 in rolling contact with an internal face of the portion 30, with the sealing portion 30 being restrained by the relatively inflexible casing 16. Such rolling expansion causes compressive plastic deformation of the portion 30 and a localised reduction in wall thickness resulting in a subsequent increase in diameter. In the illustrated embodiment this increase in diameter of the sealing portion 30 also deforms the adjacent casing 16, to form the profile 42a, by compression.

The device 10 is initially located in the intermediate tubing section 18 such that the roller ribs 28 are located adjacent one of the grip bands 37, such that on extension of the rollers 26 and rotation of the device 10, the area of greatest deformation at the extension 40a corresponds to the grip band location. Following the creation of the first extension 40a, the fluid pressure in communication with the device 10 is bled off, allowing the rollers 26 to retract. The device 10 is then moved axially by a predetermined distance relative to the tubing section 18 before being energised and rotated once more to create a second extension 40b and casing profile 42b, as shown in Figure 3. If desired, this process may be repeated to create subsequent extensions. The deformation at the two tubing section extensions 40a, 40b continues into the seal bands 36, such that the bands 36 are brought into sealing contact with the casing inner surface, between the areas of greatest deformation of the tubing section 18, and flow or deform as the bands 36 and the casing surface are "squeezed" together; this creates fluid tight seal areas at least between the tubing section 18 and the casing 16.

Following creation of the second extension 40b, the device 10 is retrieved from the bore, as illustrated in Figure 4, leaving the deformed tubing section 18 fixed in the casing 16.

The production tubing 11 is then run into the bore, as shown in Figure 5, a lower section of the tubing being of corresponding dimensions to the polished bore 34 of the tubing section 18 and provided with appropriate seal bands to provide a seal between the production tubing and the intermediate tubing section 18.

The "set" intermediate tubing section 18 may thus be seen to act in effect as a permanent packer, although the configuration and "setting" procedure for the tubing section 18 is quite different from a conventional packer.

It is apparent that the set tubing section 18 may only be removed by milling or the like, however the absence of large parts of relatively hard materials, such as is used in forming the slips of conventional packers, facilitates removal of the tubing section 18.

Reference is now made to Figures 6, 7 and 8 of the drawings, which illustrate the device 10 in greater detail. The device body 24 is elongate and generally cylindrical, and as noted above provides mounting for the three rollers 26. The rollers 26 include central portions each defining a rib 28, and taper from the central portion to circular bearing sections 50 which are located in radially extending slots 52 defined in body extensions 54 provided above and below the respective roller-containing apertures 56 in the body 24.

The radial movement of the rollers 26 is controlled by conical roller supports 58, 59 located within the body 24, the supports 58, 59 being movable towards and away from one another to move the rollers radially outwardly and inwardly. The roller supports 58, 59 are of similar construction, and therefore only one support 58 will be described in detail as exemplary of both, with particular reference to Figure 7 of the drawings. The support 58 features a loading cone 60 having a conical surface 62 which corresponds to the respective conical surface of the roller 26. The cone 60 is mounted on a four point axial load bearing 64 which is accommodated within a bearing housing 66. A piston 68 is coupled to the other end of the bearing housing 66, and has a stepped profile to accommodate a chevron seal 70. The piston 68 is located in the upper end of the body, below a connection between the body 24 and a crossover sub 72.

Accordingly, increasing the fluid pressure in the running string 20 produces an increasing pressure force on the piston 68, which tends to push the loading cone 60 in the direction A, towards and beneath the roller 26. Similarly, a fluid line leads from the upper end of the body 24 to the area beyond the other roller support 59, such that an increase in fluid pressure tends to urge the other loading cone 61 in the opposite direction. Accordingly, this forces the rollers 26 radially outwardly, and into contact with the inner surface of the intermediate tubing section 18.

This arrangement allows creation of very high pressure forces and, combined with the rolling contact between the roller ribs 28 and the intermediate tubing section 18, and the resulting deformation mechanism, allows deformation of relatively heavy materials, in this case providing deformation of both the tubing section 18 and the surrounding casing 16. Further, the nature of the deformation is such that the deformed wall of the intermediate tubing section 18 features an inner thickness of metal which is in compression, and an outer thickness of metal which is in tension. This creates a rigid and stable structure.

Reference is now made to Figures 9 and 10 of the drawings which illustrate an alternative expander device 110 for use in forming downhole arrangements 112, 113 for permitting provision of a seal between inner tubing, in the form of production tubing (not shown), and outer tubing, in the form of bore-lining casing 116, utilising an intermediate tubing section 118. The form of the tubing section 118 is substantially the same as the section 18 described above and in the interest of brevity will not be described in detail again. However, these embodiments of the present invention utilise a different form of expander device 110, as described below.

The device 110 comprises an elongate hollow body 124 which carries three radially movable rollers 126. The rollers 126 may be urged outwards by application of fluid pressure, via the running string 120, to the body interior. The device 110 is rotatable in the bore, being driven either from surface via the string 120, or by an appropriate downhole motor. The rollers 126 are rotatably mounted on relatively large area pistons such that, on application of elevated fluid pressures to the body interior, the 126 rollers are urged radially outwardly into contact with the tubing section 118.

The deformation of the section 118a as illustrated in Figure 9 is carried out in substantially the same manner as the deformation of the section 18 described above, that is by deforming or crimping the tubing section 118 at two locations 140a, 140b. However, the deformation of the section 118b as illustrated in Figure 10 is achieved by deforming or crimping the section 118 along an extended axial portion 140c. This may be achieved in a step-wise fashion, or alternatively by locating the device 110 in the upper end of the section 118, activating the device 110, and then rotating the device 110 and simultaneously applying weight to the device 110 to move the device 110 downwards through the section 118.

It will be clear to those of skill in the art that the above-described embodiments of the invention provide a simple but effective means of allowing the annulus between production tubing and casing to be sealed, using a metal-to-metal seal, the intermediate tubing section acting as a "slimline" replacement for a conventional packer, without requiring the provision of slips and elastomeric seals.

It will also be apparent to those of skill in the art that the above-described embodiments are merely exemplary of the present invention, and that various modifications and improvements may be made thereto without departing from the scope of the invention. For example, the above-described embodiment features an arrangement in which the casing is subject to plastic deformation. In other embodiments, the casing may only be subject to only minor, if any, elastic deformation, sufficient to form a secure coupling between the intermediate tubing section and the casing; where heavy gauge casing is securely in a bore cemented it may not be desirable or even possible to deform the casing to any significant extent. In other aspects of the invention, an intermediate tubing section may be provided for purposes other than creating a seal between inner and outer tubing; the tubing section may provide a sealed mounting for a valve or other device in the outer tubing.