Downhole apparatus and associated methods

Abstract

A centraliser includes a number of members extending between two collars for mounting the centraliser on a casing. The members are configured to contact a wall of the bore and centraliser the casing in the bore. The members are radially moveable between the casing and the bore wall. The members further include an intermediate portion and end portions, the end portions being relatively more flexible than the intermediate portion.

Claims

1. A centraliser for centralising tubing in a bore, comprising: end collars connected by members, wherein the members are integral with the collars, the members and the collars forming a one-piece construction, wherein the members comprise an intermediate portion and end portions for connecting the intermediate portion to the end collars, wherein the centraliser is configurable between a larger diameter configuration in which the intermediate portion assumes a radially outer position with respect to the centraliser and a smaller diameter configuration in which the intermediate portion assumes a radially inner position, wherein the end portions are configured to permit movement of the intermediate portion between the radially outer and inner positions, and the intermediate portion is relatively less flexible than the end portions, wherein the intermediate portion comprises a curved section, defined in a direction along the members, defining a first radius of curvature, the intermediate portion defining a convex outer surface, and wherein the end portions comprise a curved section, defined in the direction along the members, defining a second radius of curvature, the second radius of curvature being greater than the first radius of curvature defined by the intermediate portion, the end portions defining a concave outer surface.

2. The centraliser of claim 1, wherein the end portions each comprise at least two connectors for connecting the respective end portion to the respective end collar, the connectors of each end portion diverging from the intermediate portion so as to be spaced apart at the end collars.

3. The centraliser of claim 2, wherein the connectors comprise or define curved edges.

4. The centraliser of claim 1, wherein the end portions comprise a curved section, defined in a direction across the member, wherein the curved section defined in the direction across the member is proximal to the respective end collar and distal to the intermediate portion and provides the curved section with relatively less flexibility than another part of the end portions.

5. The centraliser of claim 1, wherein the intermediate portion comprises or defines a curved or convex outer surface in a direction defined across the members or defined between adjacent members of the centraliser.

6. The centraliser of claim 1, comprising at least one support element for restricting flexing or deformation of the members, to prevent the centraliser assuming a diameter smaller than a threshold diameter and to ensure at least partial recovery of the centraliser to a diameter larger than the threshold diameter.

7. The centraliser of claim 6, wherein at least one of: the at least one support element is configurable to abut the tubing upon flexing or deformation of at least one of the members; the at least one support element is configured to support at least one of the intermediate portion and the end portions; and the at least one support element is configured to apply a force on or resist a force applied by the members.

8. The centraliser of claim 6, wherein the at least one support element comprises a concave outer surface.

9. The centraliser of claim 6, wherein the at least one support element extends from one end portion or one of the end collars to the intermediate portion.

10. The centraliser of claim 6, wherein the at least one support element is positioned along the members so as to be located proximal to one end collar of the centraliser and distal to the other end collar of the centraliser.

11. The centraliser of claim 6, wherein the at least one support element comprises at least one arcuate spring element.

12. The centraliser of claim 6, wherein the at least one support element extends at least partially along a central portion of at least one of: the intermediate portion and the end portions.

13. The centraliser of claim 6, wherein the at least one support element extends at least partially along an edge of at least one of: the intermediate portion and the end portions.

14. The centraliser of claim 1, wherein the members comprise or are formed of a metal.

15. The centraliser of claim 1, comprising at least one contact surface for contacting a wall of the bore, the contact surface comprising a friction-reducing coating.

16. The centraliser of claim 2, wherein the connectors define a forked or split connector for transferred force between the end portions and the end collars.

17. The centraliser of claim 16, wherein the space between the connectors defines an aperture.

18. The centraliser of claim 17, wherein the aperture defines a teardrop or triangular shape.

19. The centraliser of claim 1, wherein the end portions each define a transition portion between a curved section of the intermediate portion and a curved section of the respective end collar, the transition portion comprising a larger radius of curvature than at least one of: the curved section of the intermediate portion; and a curved section of the respective end collar.

20. The centraliser of claim 1, wherein the end portions comprise or define at least one of: a curved, convex, concave or flat outer surface in a direction defined across the member.

21. The centraliser of claim 1, wherein the at least one support element is flexible or deformable.

22. The centraliser of claim 6, wherein the at least one support element is configured to apply a force on or resist a force applied by the members, wherein the at least one support element is configured to provide support for the intermediate portion, and wherein the at least one support element is centred or symmetric about the intermediate portion.

23. The centraliser of claim 15, wherein the friction-reducing coating comprises at least one of polytetrafluoroethylene and graphene.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other examples of the disclosure will now be described by way of example only and with reference to the accompanying drawings, in which:

(2) FIG. 1 is a schematic illustration of a casing in a non-central position in a horizontal section of a bore where a centraliser for supporting the casing has partially deformed e.g. due to the weight of the casing;

(3) FIG. 2 is a schematic illustration of a casing supported in a central position in a horizontal section of a bore by a centraliser in accordance with an example of the present disclosure;

(4) FIG. 3 is a side view of a centraliser in accordance with an example of the present disclosure;

(5) FIG. 4a is an axial view of the centraliser of FIG. 3;

(6) FIG. 4b is an expanded view of part of the centraliser of FIG. 4a schematically illustrated within a bore;

(7) FIG. 5 is a side view of a member of the centraliser of FIG. 3;

(8) FIG. 6 is a perspective view of a member of the centraliser of FIG. 3;

(9) FIG. 7 is a partial side view of the centraliser of FIG. 3;

(10) FIG. 8 is a side view of a centraliser in accordance with an example of the present disclosure;

(11) FIG. 9 is an axial view of the centraliser of FIG. 8;

(12) FIG. 10 is a partial side view of a member of the centraliser of FIG. 8;

(13) FIG. 11 is a perspective view of a member of the centraliser of FIG. 8;

(14) FIG. 12 is a side view of a centraliser in accordance with an example of the present disclosure;

(15) FIG. 13 is an axial view of the centraliser of FIG. 12;

(16) FIG. 14 is a perspective view of a member of the centraliser of FIG. 12;

(17) FIG. 15 is a perspective view of another example of a member; and

(18) FIG. 16 is a side view of the member of FIG. 15;

DETAILED DESCRIPTION OF THE DRAWINGS

(19) FIG. 1 illustrates a casing 10 supported by a centraliser 12 in a horizontal section of a drilled bore 14. An (asymmetric) annulus 16 is defined around the casing 10 and a wall 15 of the bore 14. Settable material such as cement is circulated between the bore wall 15 and the casing 10. The centraliser 12 in this example includes eight circumferentially spaced-apart members 18 extending between two axially spaced apart end collars 20 that are mounted on the casing 10. The weight applied onto the centraliser 12 by the casing 10 can be significant which sometimes results in the centraliser 12 deforming or collapsing such that the casing 10 is liable to move to a non-coaxial, lower, position in the bore 14. As illustrated by FIG. 1, one of the members 18 at a lower portion in the bore 14 has been flexed, radially compressed or deformed such that the spring bias in the member 18 is unable to maintain the casing 10 in a central or coaxial position within the bore 14. In such a situation, the settable material such as cement which is circulated between the casing 10 and the bore wall 15 is unlikely to be evenly (or symmetrically) distributed circumferentially around the casing 10.

(20) Referring next to FIGS. 2-7, various views and parts of a centraliser 112 are illustrated. The reference signs for like or similar features of the centraliser 112 and associated features have been incremented by 100 compared with the centraliser 12.

(21) In contrast to FIG. 1, FIG. 2 illustrates a centraliser 112 that has not substantially deformed (or has at least partially recovered from a previous deformation) such that the casing 110 adopts a substantially central (e.g. coaxial) position within the bore 114. It will be appreciated that in all likelihood there will be a certain degree of deformation of any centraliser, particularly in horizontal sections of the bore where the weight of the casing is liable to cause deformation of the members on the lower side of the bore 114, which can be recognised with reference to both FIGS. 1 and 2. The substantially central position of the casing 110 illustrated by FIG. 2 may permit an approximately even distribution of settable material to be circulated through the annulus 116 defined between the casing 110 and the bore wall 115.

(22) As the centraliser 112 is moved through the bore 114, at least one member 118 of the centraliser 112 may flex or deform in response to passing through restrictions in the bore 114 and may return, at least substantially, to their first or initial (e.g. a non-flexed, non-compressed or non-deformed) condition. Each member 118 includes an intermediate portion 119 and end portions 121 for connecting the intermediate portion 119 to the end collars 120. The centraliser 112 is configurable between a larger diameter configuration in which the intermediate portion 119 assumes a radially outer position with respect to the centraliser 112 and a smaller diameter configuration in which the intermediate portion 119 assumes a radially inner position (e.g. to permit passage of the centraliser 112 through a bore restriction). The end portions 121 are configured to permit movement of the intermediate portion 119 between the radially outer and inner positions. The intermediate portion 119 is relatively less flexible than the end portions 121. In this example, the intermediate portion 119 is relatively less flexible than the end portions 121 due to the intermediate portion 119 being relatively more curved (e.g. has a smaller radius of curvature) than the end portions 121.

(23) Each member 118 has an outer surface 128 that is oriented to face the bore wall 115. The outer surface 128 includes a contact surface 130 for contacting the bore wall 115, the contact surface 130 extending at least partially along the outer surface 128 and includes a crest 132 of the member 118. As best illustrated by FIG. 5, the crest 132 defines a high (or radially outermost) point of the member 118 and is located at a mid-portion 134 between the two collars 120. With reference to at least FIGS. 5 and 6, the intermediate portion 119 includes a convex outer surface 128 defined in a direction along the member 118 and the end portions 121 include a concave outer surface 128 also defined in the direction along the member 118. It will be appreciated that there may be a flat surface defined between the convex and concave outer surfaces of the member 118.

(24) The intermediate portion 119 includes a curved section 123 defining a first radius of curvature (e.g. in a direction defined between adjacent members 118 or across the members 118) for providing the intermediate portion 119 with relatively less flexibility than the end portions 121. In this example, the end portions 121 include a non-curved section 125 provided along a length of the end portion 121 for permitting movement of the intermediate portion 119 between the radially outer and inner positions. The non-curved section 125 is relatively more flexible than the curved sections (e.g. of the intermediate portion 119).

(25) The end portions 121 each include two connectors 136 for connecting the respective end portion 121 to the respective end collar 120. The connectors 136 of each end portion 121 diverge from the intermediate portion 119 so as to be spaced apart at the end collars 120.

(26) The two connectors 136 of each end portion 121 each include a curved section 137 proximal to the respective end collar 120 and distal to the intermediate portion 119 for providing the curved section 137 with relatively less flexibility than another part of the end portions 121 (such as the non-curved section 125).

(27) The non-curved section 125 at least partially defines a transition portion between the intermediate portion 119 and the respective end collar 120. The intermediate portion 119 includes a convex outer surface and the end portions 121 include a concave outer surface defined in a direction between the end collars 120 of the centraliser 112. The intermediate portion 119 also defines a convex outer surface in a direction defined between adjacent members 118 of the centraliser 112. The end portions 121 include both a convex (e.g. at least the curved section 137) and a flat outer surface (e.g. the non-curved section 125) in a direction defined between adjacent members 118 of the centraliser 120.

(28) A teardrop-shaped aperture 138 is defined between the connectors 136 and the end collar 120. Each member 118 includes edges 140 extending along the length of the member 118. The edges 140 include arcuate sections, including parts having a convex or concave form. The curved form of at least one part of the members 118 provides a degree of stiffness, or less flexibility, than at least one other part of the members 118.

(29) As best illustrated by FIG. 4b, the bore wall 115 defines a first radius of curvature (e.g. circumferentially around the bore 114). The contact surface 130 of the member 118 defines a second radius of curvature (e.g. circumferentially around the centraliser 112 or across the member 118), the second radius of curvature in this case being less than the first radius of curvature. The outer surface 128 (including the contact surface 130) of the member 118 is convex when viewed in an axial or downhole direction (as best illustrated by FIGS. 4a-b). The radius of curvature of the contact surface 130 being less than the radius of curvature of the bore wall 115 may reduce friction between the member 118 and the bore wall 115 as the centraliser 112 moves through the bore 114 (i.e. compared to a member having a contact surface that has a radius of curvature that is more than the radius of curvature of the bore wall 115, e.g. if the contact surface of such a member is flat (or non-curved) when viewed in the axial or downhole direction). The contact surface 130 includes a central portion 154 that is contactable with the bore wall 115 and edge portions 155 that are not contactable with the bore wall 115 if the centraliser is in a non-deformed or partially-deformed condition, which may reduce friction as the centraliser 112 moves through the bore 114. The member 118 may experience less drag, wearing or deformation during passage through the bore 114 due to this reduced friction property.

(30) Optionally, the contact surface 130 includes a friction-reducing coating such as polytetrafluoroethylene (e.g. Teflon™), graphene, or the like, e.g. for easing the movement of the centraliser 112 through the bore 114.

(31) The end collars 120 each include eight casing engagement elements 142 for axially restricting the range of movement of the centraliser 112 on the casing 110. The casing engagement elements 142 are in the form of axially extending protrusions 144 disposed between each of the members 118 and extending from each collar 120 and facing towards corresponding casing engagement elements 142 on the other collar 120. The casing engagement elements 142 are configured to engage a stop collar (not shown) mounted on the casing 110 so as to permit a limited degree axial movement of the centraliser 112 along the casing 110 but to prevent the centraliser 112 from slipping substantially along the casing 110 during movement of the casing 110 through the bore 114. Thus, the centraliser 112 is partially free to move relative to the casing 110 but will not significantly deviate from the position defined by the stop collar.

(32) Referring next to FIGS. 8-11, various views and parts of a centraliser 212 are illustrated. The reference signs for like or similar features of the centraliser 212 and associated features have been incremented by 100 compared with the centraliser 112. The following description highlights the features which are different to those features already described in relation to FIGS. 2-7.

(33) The centraliser 212 of FIGS. 8-11 has generally a similar form to the centraliser 112 of FIGS. 2-7. The centraliser 212 includes members 218 for contacting the bore wall 115. The members 218 are radially moveable or deformable between the casing 110 and the bore wall 115 from an initial, non-deformed, condition into a deformed condition to permit movement of the centraliser 212 through restrictions in the bore 114.

(34) The members 218 have edges 240 including a convex and concave form that extends along the members 218. With reference to e.g. FIG. 8, it will be recognised that some of the edges 240 include straight edges as well as curved edges. The member 218 includes apertures 238 (similar to the apertures 138 of members 118) which are in the form of a rounded-corner triangle.

(35) However, each of the members 218 also include a support element 248 for restricting deformation of the elements 218 (e.g. which may occur when the centraliser 212 passes through restrictions in the bore 114 and/or in response to weight applied on the centraliser 212 by the casing 110).

(36) The support element 248 is in the form of an arcuate spring element 250 that extends substantially across a portion (e.g. from one end portion 221 to the other end portion 221) of each of the members 218. The support element 248 is partially cut out from a central portion 254 defined within an intermediate portion 219 of each of the members 218 and extends from extends from the first end portion 221 to the second end portion 221 of the members 218. The first end portion 221 is provided between the aperture 238 at one end of the member 218 and the crest 232 of the member 218. The second end portion 221 is provided between the aperture 238 at the other end of the member 218 and the crest 232. The first end portion 221 and second end portion 221 each define a transition which joins the member 218 to both ends of the support element 248. Accordingly, each member 218 includes two contact surfaces 230 extending along (and radially outwardly of) the support element 248.

(37) Radial compression of the member 218 may result in an inner surface 260 of the support element 248 abutting the casing 110. Upon abutting the casing 110, the support element 248 may resist further radial compression of at least one of the members 218. The support element 248 restricts deformation of the corresponding member 218 to prevent the centraliser 212 assuming a diameter smaller than a threshold diameter to ensure an at least partial recovery of the centraliser 212 to a diameter larger than the threshold diameter. If the centraliser 212 is deformed to assume a diameter that is less than the threshold diameter, the members 218 may have been excessively deformed to the extent that the centraliser 212 may not sufficiently recover to its initial, non-deformed, condition (e.g. after passing through a restriction in the bore 114). The support element 248 is symmetric about the crest 232 and is arranged to restrict deformation of the members 218 in response to a radial compression of the members 218.

(38) As best illustrated by FIG. 10, the member 218 includes a convex outer surface 228 when viewed from the side. In contrast, the support element 248 includes a concave outer surface 262 (correspondingly, the inner surface 260 is convex). Thus, the member 218 is curved radially outwardly so as to be contactable with the bore wall 115 whereas the support element 248 is curved radially inwardly and is not generally contactable with the bore wall 115.

(39) Referring next to FIGS. 12-14, various views and parts of a centraliser 312 are illustrated. The reference signs for like or similar features of the centraliser 312 and associated features have been incremented by 100 compared with the centraliser 212. The following description highlights the features which are different to those features already described in relation to FIG. 2-7 or 8-11.

(40) The centraliser 312 of FIGS. 12-14 has generally a similar form to the centraliser 212 of FIGS. 8-11. The members 318 each include four support elements 348, each of which has similar functionality to the members 218 and support element 248 of FIGS. 8-11. However, the arrangement of the members 318 and support elements 348 is different in this example.

(41) The members 318 include an outer surface 328 and extend between the two end collars 320, including a central portion 354 extending along a length of the member 318 between the two end collars 320.

(42) The support elements 348 in this example include a number of arcuate spring elements 350 (in this example four in total per member 318). Two of the arcuate spring elements 350 extend between one of the end collars 320 and a mid-way point 334 along the member 318. Each of the arcuate spring elements 350 extend at least partially along an edge 340 of the member 318. The two arcuate spring elements 350 at each end of the member 318 are spaced apart from each other with the part of the member 318 extending between the collars 320 being disposed between the two spaced apart arcuate spring elements 350.

(43) The members 318 are arcuate and include a convex outer surface 328 substantially along their entire length between the end collars 320. The arcuate spring elements 350 include a concave outer surface 362 substantially along their entire length between their respective collars 320 and the mid-way point 334. An identical (or symmetric) arrangement is provided for the other two arcuate spring elements 350 for joining the other collar 320. In contrast to previous examples, the members 318 are connected to each collar 320 using three connectors 336 instead of two connectors. The arcuate spring elements 350 include two of the three connectors 336 (at each end of the member 318) for connecting the arcuate spring elements 350 to the end collar 320.

(44) The member 318 includes the other of the three connectors 336 (at each end of the member 318).

(45) The arcuate spring elements 350 are positioned so as to apply a reaction force that acts to ensure that the mid-way point 334 of the members 318 defines a radially outermost part of the members 318. The arcuate spring elements 350 are configured to abut the casing 110 in response to a radial compression of the members 318 similar to the example of FIGS. 8-11 but in contrast to the example of FIGS. 8-11 in which the arcuate spring element 250 are deformable for abutting the casing 110 at a mid-way point 234 between the end collars, the arcuate spring members 350 in the present example are deformable for abutting the casing 110 either side of the mid-way point 334. Two of the arcuate spring elements 350 extend along the member 318 so as to be located proximal to a first end collar 320 of the centraliser 312 and distal to a second end collar 320 of the centraliser 312. Equally, the other two arcuate spring elements 350 are positioned in an equivalent way in relation to the second end collar 320 but proximal thereto.

(46) Referring next to FIGS. 15-16, there is illustrated an example of a member 418 suitable for a centraliser. The reference signs for like or similar features of the member 418 and associated features have been incremented by 100 compared with the member 318. The following description highlights features that are different to those features already described in relation to FIGS. 12-14.

(47) The member 418 has a number of similarities to the member 318. However, the member 418 has a number of features which can be considered to be inverted compared to the member 318.

(48) The member 418 is arcuate and includes a convex outer surface 428 substantially along its entire length. However, in contrast to the previous example where the four arcuate spring elements 350 defined the support elements 348 of the member 318, the corresponding components in this example are now inverted so as to form part of the member 418 and now include the convex outer surface 428 instead of a concave outer surface.

(49) Further, in contrast to the previous example where parts of the member 318 extend between the spaced-apart arcuate spring elements 350 and the end collars 320, these parts are now inverted so as to form the support element 448 and now each include a concave outer surface 462. Thus, these two parts now take the form of arcuate spring elements 450. Therefore, in this example, two support elements 448 are defined, each support element 448 extending between a respective collar (e.g. similar to collar 320) and a mid-way point 434 along the member 418. The support elements also extend at least partially along a central portion 454 of the members 418.

(50) Various modifications may be made to any of the disclosed examples. At least one feature of one example may replace, be combined with or used to modify at least one feature of another example.

(51) Although some of the examples illustrate members which are integral with the collars (e.g. to form one-piece components), it will be appreciated that the members and/or centraliser can be constructed in any appropriate way. For example, the members could be provided as separate components and then connected to the collars (e.g. by welding, or the like). At least one example of a centraliser of the present disclosure may be formed as a one-piece component, for example, by laser cutting or the like a single-piece of material which can be formed into the one-piece centraliser. It will be appreciated that the members and end collars may be provided as separate components and subsequently connected together in any appropriate way. The intermediate and end portions may be provided as separate components and subsequently joined together. The centraliser may be at least partially constructed or formed using an additive or reductive manufacturing process, which may be performed in any appropriate way.

(52) Although some of the examples illustrate centralisers having eight members, it will be appreciated that any appropriate number of members may be provided.