Downhole patch

Abstract

The invention relates to a downhole patch comprising a tubular body having an upstream end, a downstream end, and an intermediate section extending from the downstream end to the upstream end, wherein the intermediate section has an exterior surface comprising a helical structure configured to guide fluid along the length of the intermediate section. The invention also relates to a method for patching a downhole structure.

Description

DESCRIPTION

[0001] The present invention relates to a downhole patch. In particular, the present invention relates to a tubular patch for downhole operations. The invention also relates to a method for patching a downhole structure.

[0002] A patch is used downhole as a tool to reline a borehole casing or tubing. Such patch can be arranged to repair damaged casing sections, corrosion or leaks, or to isolate unwanted perforations of the surrounding structure.

[0003] When a well tubular structure becomes perforated or has sprung leaks, there may be a need to close the leak or perforations in order to close all fluid communication between an annulus and the interior of the well tubular. Such patching has often been done using metal patches, where a packer assembly may be introduced into the well tubular structure, and an expandable tubular element may be inflated in order to expand the metal patch towards the inner face of the well tubular metal structure to close the leak or the perforation.

[0004] While patches are commonly used, problems may arise if fluid is trapped outside the patch, thereby preventing the desired expansion of the patch.

[0005] Based on this, there is a need for an improved downhole patch that solves the above-mentioned problems.

[0006] An idea of the present invention is to provide a downhole patch that allows fluid present outside of the patch to be guided away from the patch length as the patch expands. In this way, expansion of the patch may be performed in a desired manner, thus forming a seal against the surrounding tubular structure.

[0007] It is an object of the present invention to wholly or partly overcome the disadvantages and drawbacks of the prior art. More specifically, an object of the invention is to provide a downhole patch, comprising a tubular body having an upstream end, a downstream end, and an intermediate section extending from the downstream end to the upstream end, wherein the intermediate section has an exterior surface comprising a helical structure configured to guide fluid along the length of the intermediate section.

[0008] The helical structure will effectively guide any fluid present on the exterior of the side along the patch, thereby ensuring proper expansion of the patch even if fluid is present. Thus, it is possible to set the patch inside a metal structure such as a casing, a liner, tubing, etc., without trapping fluid between the patch and the metal structure.

[0009] Moreover, the helical structure may comprise one or more helical ridges extending radially outwards from the exterior surface of the intermediate section. This is advantageous in that the flow-guiding characteristics may be optimised, while still ensuring proper contact between the patch and the surrounding tubular structure.

[0010] Also, at least one of the upstream end and the downstream end may comprise a radial seal portion. This is advantageous in that the patch may effectively seal against the surrounding tubular structure of the wellbore, while it also contributes to maintaining the position of the patch.

[0011] The radial seal portion is an annular sealing element. The radial seal portion is a ring-shaped sealing element providing an endless seal, i.e., a non-helical seal.

[0012] By having a helical path along the intermediate section of the patch and seal portions at the upstream end and the downstream end, the patch can be expanded within a metal casing without trapping fluid between the patch and the casing as then the intermediate section can be expanded first, after which at least one of the seal portions is expanded, providing the more efficient seal of the patch.

[0013] Alternatively, one of the downstream or upstream ends will start to expand to seal against the surrounding tubular structure. The intermediate section will then start to expand, and any fluid present outside of the intermediate section will be allowed to escape through the yet unsealed end. Only when the intermediate section is fully expanded, the other one of the upstream or downstream end will expand to seal against the surrounding tubular structure.

[0014] In a prior art solution, the sealing element forms part of the helically structured path, and thus the fluid may escape during expansion, but the patch does not provide a seal. Thus, by having the seal portion as an annular sealing element in a separate seal portion, the patch provides a proper circumferential, endless seal, and the fluid cannot flow past the seal portion but can escape during expansion along the helical path, which means that the fluid is not trapped but only prevented from leaking over the seal portion.

[0015] Furthermore, the width of the helical ridge may be in the range of 2-25mm, preferably in the range of 5-20mm, more preferably in the range of 8-12mm. This improves the flow-guiding properties of the patch, while still ensuring proper operation of the patch.

[0016] In addition, the height of the helical ridge may be in the range of 0.1-3mm, preferably in the range of 0.2-1mm, more preferably in the range of 0.4-0.6mm. This is advantageous in that the flow-guiding characteristics may be optimised, while still ensuring proper contact between the patch and the surrounding tubular structure.

[0017] Further, the helical structure may comprise a plurality of parallel helical ridges. This allows the pitch of each helical ridge to be relatively large, still ensuring the desired flow-guiding properties.

[0018] Moreover, the plurality of helical ridges may be angularly offset from each other. This allows all portions of the fluid guide to be substantially equal along the patch, thereby ensuring uniform properties of the patch along its longitudinal direction.

[0019] Also, the axial distance between two adjacent helical ridges may be in the range of 20–60mm, preferably in the range of 30-50mm, more preferably in the range of 35-45mm. This is advantageous in that the flow-guiding characteristics may be optimised, while still ensuring proper contact between the patch and the surrounding tubular structure.

[0020] Furthermore, the pitch of the helical structure may be in the range of 100-140mm, preferably in the range of 110-130mm, more preferably in the range of 115-125mm. This improves the flow-guiding properties of the patch, while still ensuring proper operation of the patch.

[0021] In addition, the radial seal portion may comprise two spaced-apart radial protrusions, and wherein the axial space formed between the radial protrusions is configured to accommodate an O-seal. This allows manufacturing of the patch as a single-piece component and ensures simple addition of the O-seal.

[0022] Further, at least one of the upstream end and the downstream end may comprise a plurality of axially spaced-apart radial seal portions. This further improves the seal against the surrounding tubular structure of the wellbore, while it also improves the maintaining of the position of the patch.

[0023] Moreover, the diameter of the upstream end and / or downstream end may be less than the diameter of the intermediate section. This allows the patch to be easily mounted to a packer assembly.

[0024] Also, the helical structure may extend along the entire length of the intermediate section. This ensures proper guiding of fluid along the entire longitudinal extension of the intermediate section.

[0025] Furthermore, the helical structure may form a continuous fluid passage between the upstream end and the downstream end. This also assists in proper guiding of fluid along the entire longitudinal extension of the intermediate section.

[0026] The invention also relates to, a method for patching a downhole structure, comprising:

[0027] arranging a patch radially outwards of a packer assembly downhole,

[0028] initiating expansion of at least one expandable tubular of the packer assembly, thereby causing a corresponding expansion of the patch, and

[0029] continuing expansion of the patch such that the patch expands radially into contact with a surrounding structure, while simultaneously guiding fluid present between the patch and the surrounding structure along the patch via a helical structure of the patch.

[0030] Accordingly, any fluid that is present outside of the patch may escape as the patch expands through the fluid passages formed by the helical structure, whereby proper expansion of the patch is ensured.

[0031] The invention and its many advantages will be described in more detail below with reference to the accompanying schematic drawings, which for the purpose of illustration show some non-limiting embodiments and in which:

[0032] FIG. 1 is a cross-sectional view of a borehole comprising a downhole patch in an original state and in an expanded state, according to an example,

[0033] FIG. 2 is a side view of a downhole patch according to an example,

[0034] FIG. 3 is a side view of an enlarged section of a downhole patch according to an example,

[0035] FIG. 4 is a cross-sectional view of a part of a downhole patch according to an example,

[0036] FIGS. 5-7 are cross-sectional views of a borehole comprising a downhole patch during positioning of the downhole patch according to one example,

[0037] FIG. 8 is a cross-sectional view of a borehole comprising a downhole patch according to a further example, and

[0038] FIG. 9 is a schematic view of a method for patching a downhole structure according to one example.

[0039] Various exemplary embodiments and details are described below, with reference to the figures when relevant. It should be noted that the figures may or may not be drawn to scale and that elements of similar structures or functions are represented by like reference numerals throughout the figures. It should also be noted that the figures are only intended to facilitate the description of the embodiments. They are not intended as an exhaustive description of the disclosure or as a limitation on the scope of the disclosure. In addition, an illustrated embodiment need not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practised in any other embodiments even if not so illustrated, or if not so explicitly described.

[0040] Starting in FIG. 1, the principle of a downhole patch 1 is schematically shown. The patch 1 has a longitudinal extension and an initial diameter D1. The initial diameter D1 is selected such that the patch 1 can be moved downhole to its intended position, using any suitable transportation as will be further exemplified below. When the patch 1 is at its desired position downhole, the initial diameter D1 is expanded to an enlarged diameter D2. The patch 1 is then in close contact with a circumferential structure 100 surrounding the patch 1. During expansion, the patch 1 is configured such that any fluid positioned radially between the patch 1 and the circumferential structure 100 will be guided longitudinally along the patch 1, thereby preventing the fluid from getting trapped, which could prevent the patch 1 from expanding properly. The patch 1 is sealed against the circumferential structure 100 surrounding the patch 1 at its longitudinal ends. By allowing at least one of the longitudinal ends to remain non-expanded (or at least in a condition where it does not seal against the circumferential structure 100) until the end of the expansion process, the fluid that is present outside of the patch 1 will be allowed to escape through the non-sealed end. In prior art patches, the patch is equipped with annular sealing along the length of the patch, and if the patch is not expanded simultaneously along the entire length, fluid will be trapped between the patch and the circumferential structure, which prevents full expansion of the patch. In such case, the not fully expanded patch will decrease the inner diameter of the circumferential structure, which may prevent full access of other tools later, and the tool may become stuck in the patch, as a result of which the patch may be loosened from the circumferential structure again. Furthermore, when the known patches are not fully expanded, they are not sealing properly and thus do not provide the intended sealing of a perforated zone or leak in the metal casing. Accordingly, the result may be that the known patch is only partly expanded, thereby limiting access and not sealing as intended.

[0041] In FIG. 2, the patch 1 is shown in further detail, in a non-expanded condition. The patch 1 is formed as a tubular body 3 having an upstream end 5, a downstream end 7, and an intermediate section 9 extending from the downstream end 7 to the upstream end 5. The tubular body 3 is preferably formed by a metal, such as stainless steel or similar material. The wall thickness of the tubular body 3 is preferably selected such that the desired structural rigidity is obtained, while still allowing the tubular body 3 to expand radially. In one example, the wall thickness of the patch 1 is 2-4mm, such as 3mm.

[0042] In order to guide fluid longitudinally along the patch 1, the intermediate section 9 has an exterior surface 11 comprising a helical structure 13 configured to guide the fluid present on the exterior side of the patch 1. In the shown example, the helical structure 13 extends along the entire length of the intermediate section 9. The helical structure 13 may thus form a continuous fluid passage 15 between the upstream end 5 and the downstream end 7.

[0043] The longitudinal ends of the patch 1 form an upstream end 5 and a downstream end 7. Each one of the upstream end 5 and the downstream end 7 comprises at least one radial seal portion 19 which is an annular sealing element 19. When the patch 1 expands, at least one of the upstream end 5 and the downstream end 7 is left non-expanded until the intermediate section 9 has expanded fully. This allows any fluid present radially outside of the patch 1 to escape along the helical structure 13 and out through the non-sealed end(s) 5, 7. At least one of the upstream end 5 and the downstream end 7 is not completely expanded until the intermediate section 9 is fully expanded.

[0044] In a prior art solution, the sealing element forms part of the helically structured path, and thus the fluid may escape during expansion, but the patch does not provide a seal. Thus, by having the seal portion as an annular sealing element in a separate seal portion, the patch provides a proper circumferential, endless seal, and the fluid cannot flow past the seal portion but can escape during expansion along the helical path, which means that the fluid is not trapped but only prevented from leaking over the seal portion. The helical path can both provide fluid passage and an anchoring effect as the helical path can be made with at least one ridge 13a.

[0045] Now turning to FIGS. 3 and 4, further details of the patch 1 will be described. In FIG. 3, only the downstream end 7 is shown. However, it should be realised that in preferred examples the upstream end 5 is similar, or even identical, to the downstream end 7. As can be seen in FIG. 3, the tubular body 3 has a varying diameter. The downstream end 7 has a smaller diameter than the intermediate section 9. The downstream end 7 has a proximal section 17 interfacing with the intermediate section 9. The diameter of the proximal section 17 is gradually increasing towards the intermediate section 9, such that the proximal section 17 forms a connection between the downstream end 7 and the intermediate section 9. The downstream end 7 comprises at least one radial seal portion 19. In the shown example, the radial seal portion 19 is formed as a circumferential groove. In the shown example, two grooves 19 are present. However, any suitable number of grooves 19 may be considered. Each groove 19 extends around the entire perimeter of the downstream end 7 and is formed as an axial and radial space 21 occurring between two adjacent radial protrusions 23a-b. Each radial protrusion 23a-b may have a triangular shape, with one sidewall facing the space 21 being fully aligned with the radial direction of the patch 1. Each groove 19 is configured to accommodate a seal, such as an O-ring (not shown). The groove 19 may also comprise a back-up element arranged to abut the seal portion 19 in order to back up the seal so that the seal is not pushed out of the groove 19 when subjected to pressure. The back-up element may be in the form of a key ring able to at least partly unwind as the expansion of the patch 1 occurs.

[0046] The helical structure 13 preferably comprises a plurality of helical ridges 13a-c. Each helical ridge 13a-c extends radially outwards from the exterior surface 11 of the intermediate section 9. The helical ridges 13a-c may be parallel and angularly offset from each other. In the shown example, there are three helical ridges 13a-c spaced apart by 120°.

[0047] An axial distance AD between two adjacent helical ridges 13a-c may be in the range of 20–60mm, preferably in the range of 30-50mm, more preferably in the range of 35-45mm. Further, a pitch P of the helical structure 13 may be in the range of 100-140mm, preferably in the range of 110-130mm, more preferably in the range of 115-125mm. Hence, when three helical ridges 13a-c are present, the pitch P will correspond to the axial distance AD between three adjacent ridges 13a-c. However, any number of helical ridges 13a-c may be considered.

[0048] In FIG. 4, further details of the helical ridges 13a-c are shown. A width W of each helical ridge 13a-c may be in the range of 2-25mm, preferably in the range of 5-20mm, more preferably in the range of 8-12mm. A height H of each helical ridge 13a-c may be in the range of 0.1-3mm, preferably in the range of 0.2-1mm, more preferably in the range of 0.4-0.6mm. The helical ridge 13a may extend radially away from the exterior surface 11 of the patch 1 by slanted surfaces 13d, whereby the slanted surfaces 13d are connected by a flat portion 13e.

[0049] While the helical structure 13 has been described as having helical ridges 13a-c, in some examples the helical ridges 13a-c are instead helical grooves. In some examples, the helical structure 13 comprises a combination of helical ridges 13a-c and helical grooves.

[0050] The space between the helical ridges 13a-c forms a continuous fluid passage 15. Even though the helical ridges 13a-c will press against the circumferential downhole structure 100 surrounding the patch 1, the continuous fluid passage 15 will guide any trapped fluid to escape along the patch 1.

[0051] From the above description of the downhole patch 1, it is understood that the patch 1 may be operable in a wide range of ways. In one example, as being shown in FIGS. 5-7, the patch 1 is arranged in a well 90 downhole inside a well tubular metal structure 100 using a packer assembly 110. The packer assembly 110 comprises a first expandable tubular element 112 and a second expandable tubular element 114 axially spaced apart from the first expandable tubular element 112.

[0052] While the packer assembly 110 is here shown as a wireline tool, it should be readily understood that the patch 1 may be operated by any suitable component, such as coiled tubing or a drill pipe. In such example, the pressure required to cause expansion of the patch 1 can be provided from the surface instead of using downhole pumps or other pressurising components.

[0053] The patch 1 is mounted to surround the first expandable tubular element 112 and the second expandable tubular element 114.

[0054] In a first operational state, shown in FIG. 5, the first expandable tubular element 112 is arranged at a first distance X1 from the second expandable tubular element 114. The first operational state of the packer assembly 110 may be seen as an operational state where the packer assembly 110 is conveyed into the borehole, where the first expandable tubular element 112, the second expandable tubular element 114 and the metal patch 1 have a first radial extension. The first radial extension is smaller than the inner diameter of the well tubular metal structure 100, allowing the packer assembly 110 to be conveyed safely into a position inside the well tubular metal structure 100, where the packer assembly 110 is to be deployed by expanding the metal patch 1 to e.g. patch a leak and / or a perforation in the well tubular metal structure 100.

[0055] In the first operational state, the metal patch 1 may be held in its position via frictional forces between the first expandable tubular element 112 and the second expandable tubular element 114.

[0056] FIG. 6 shows the packer assembly 110 in an intermediate operational state, where the first expandable tubular element 112 and the second expandable tubular element 114 have been expanded, e.g. by introducing fluid into them in any way known in the art. The first expandable tubular element 112 and the second expandable tubular element 114 expand the metal patch 1 into contact with the well tubular metal structure 100. Furthermore, the intermediate section 9 of the patch 1 may be expanded by introducing fluid into the radial space formed between the patch 1 and the packer assembly 110, including the first expandable tubular element 112 and the second expandable tubular element 114.

[0057] When the patch 1 has been expanded into this particular state, it can be seen that the upstream end 5 and the downstream end 7 of the patch 1 still have a smaller diameter than the intermediate section 9 of the metal patch 1, indicating that the upstream end 5 and the downstream end 7 do not yet seal against the circumferential structure 100 surrounding the patch 1. Hence, fluid outside of the patch 1 may still be allowed to escape through the upstream end 5 and the downstream end 7, while the intermediate section 9 expands to its fully expanded state. In that way, the fluid opposite the intermediate section 9 is not trapped during expansion as it can escape through the ends 5, 7. To finalise the expansion of the patch 1, the packer assembly 110 may be operated in a second operational state as shown in FIG. 7.

[0058] Here, the first expandable tubular element 112 and the second expandable tubular element 114 have been moved axially away from each other to an axial distance X2. This increase in axial distance AD allows the first expandable tubular element 112 to expand the upstream end 5 of the metal patch 1 and the second expandable tubular element 114 to expand the downstream end 7 of the metal patch 1. Consequently, the upstream end 5 and the downstream end 7 will expand fully and seal against the circumferential structure 100 surrounding the patch 1. Following this, the packer assembly 110 can be moved away from the patch 1 by deflating the first and second expandable tubular elements 112, 114.

[0059] As is shown in FIG. 8, the patch 1 may also be operated with a packer assembly 110 having a single expandable tubular element 112. In the shown example, the single expandable tubular element 112 is axially aligned with the downstream end 7 of the patch 1. Upon expansion of the expandable tubular element 112, the downstream end 7 of the patch 1 will expand accordingly and seal against the circumferential structure 100 surrounding the patch 1. The remaining portion of the patch 1 may be expanded by moving the packer assembly 110 upwards, such that the expandable tubular element 112 will force the patch 1 to expand. Consequently, as the patch 1 expands, fluid present outside of the patch 1 will not be allowed to escape through the sealed downstream end 7, but it will instead be allowed to flow along the helical structure 13 of the intermediate section 9 and out through the still open upstream end 5. Since the upstream end 5 will expand lastly, the intermediate section 9 will always be allowed to expand fully even if fluid is present outside of it.

[0060] In FIG. 9, a method 200 for patching a downhole structure is schematically shown. The method 200 comprises arranging 202 a patch radially outwards of a packer assembly downhole. The method 200 further comprises initiating expansion 204 of at least one expandable tubular of the packer assembly, thereby causing a corresponding expansion of the patch. The method also comprises continuing expansion 206 of the patch such that the patch expands radially into contact with a surrounding structure, while simultaneously guiding fluid present between the patch and the surrounding structure along the patch via a helical structure of the patch. As has been described above, one of the upstream end or downstream end is expanded lastly, such that fluid can flow out from the space formed between the patch 1 and the circumferential structure 100 surrounding the patch 1. Considering the upstream end 5, the intermediate section 9, and the downstream end 7 of the patch, the intermediate section 9 will always expand fully before at least one of the upstream end 5 and the downstream end 7 expands fully and seals against the circumferential structure 100 surrounding the patch 1.

[0061] The use of the terms “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary”, etc., does not imply any particular order, but are included to identify individual elements. Moreover, the use of the terms “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary”, etc., does not denote any order or importance, but rather the terms “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary”, etc., are used to distinguish one element from another. Note that the words “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary”, etc., are used here and elsewhere for labelling purposes only and are not intended to denote any specific spatial or temporal ordering.

[0062] Furthermore, the labelling of a first element does not imply the presence of a second element and vice versa.

[0063] It is to be noted that the word ”comprising” does not necessarily exclude the presence of other elements or steps than those listed.

[0064] It is also to be noted that the words ”a” or ”an” preceding an element do not exclude the presence of a plurality of such elements.

[0065] It should further be noted that any reference signs do not limit the scope of the claims.

[0066] By “fluid” or “well fluid” is meant any kind of fluid that may be present in oil or gas wells downhole, such as natural gas, oil, oil mud, crude oil, water, etc. By “gas” is meant any kind of gas composition present in a well, completion or open hole, and by “oil” is meant any kind of oil composition, such as crude oil, an oil-containing fluid, etc. Gas, oil and water fluids may thus all comprise other elements or substances than gas, oil and / or water, respectively.

[0067] By “casing” or “well tubular metal structure” is meant any kind of pipe, tubing, tubular, liner, string, etc., used downhole in relation to oil or natural gas production. In the event that the tool is not submersible all the way into the casing, a downhole tractor can be used to push the tool / downhole system all the way into position in the well. The downhole tractor may have projectable arms having wheels, wherein the wheels contact the inner surface of the casing for propelling the tractor and the tool forward in the casing. A downhole tractor is any kind of driving tool capable of pushing or pulling tools in a well downhole, such as a Well Tractor®.

[0068] Although the invention has been described above in connection with preferred embodiments of the invention, it will be evident to a person skilled in the art that several modifications are conceivable without departing from the invention as defined by the following claims.

Claims

1. A downhole patch, comprising a tubular body having an upstream end, a downstream end, and an intermediate section extending from the downstream end to the upstream end,wherein the intermediate section has an exterior surface comprising a helical structure configured to guide fluid along the length of the intermediate section, wherein at least one of the upstream end and the downstream end comprises a radial seal portion.

2. The downhole patch according to claim 1, wherein the helical structure comprises one or more helical ridges extending radially outwards from the exterior surface of the intermediate section.

3. The downhole patch according to claim 2, wherein the width of the helical ridge is in the range of 2-25mm, preferably in the range of 5-20mm, more preferably in the range of 8-12mm.

4. The downhole patch according to claim 2, wherein the height of the helical ridge is in the range of 0.1-3mm, preferably in the range of 0.2-1mm, more preferably in the range of 0.4-0.6mm.

5. The downhole patch according to claim 2, wherein the helical structure comprises a plurality of parallel helical ridges.

6. The downhole patch according to claim 5, wherein the plurality of helical ridges are angularly offset from each other.

7. The downhole patch according to claim 5, wherein the axial distance between two adjacent helical ridges is in the range of 20–60mm, preferably in the range of 30-50mm, more preferably in the range of 35-45mm.

8. The downhole patch according to claim 1, wherein the pitch of the helical structure is in the range of 100-140mm, preferably in the range of 110-130mm, more preferably in the range of 115-125mm.

9. The downhole patch according to claim 1, wherein the radial seal portion comprises two spaced-apart radial protrusions, and wherein the axial space formed between the radial protrusions is configured to accommodate an O-seal.

10. The downhole patch according to claim 1, wherein at least one of the upstream end and the downstream end comprises a plurality of axially spaced apart radial seal portions.

11. The downhole patch according to claim 1, wherein the diameter of the upstream end and / or downstream end is less than the diameter of the intermediate section.

12. The downhole patch according to claim 1, wherein the helical structure extends along the entire length of the intermediate section.

13. The downhole patch according to claim 1, wherein the helical structure forms a continuous fluid passage between the upstream end and the downstream end.

14. A method for patching a downhole structure, comprising: arranging a patch radially outwards of a packer assembly downhole,initiating expansion of at least one expandable tubular of the packer assembly, thereby causing a corresponding expansion of the patch, andcontinuing expansion of the patch such that the patch expands radially into contact with a surrounding structure, while simultaneously guiding fluid present between the patch and the surrounding structure along the patch via a helical structure of the patch and through at least one longitudinal end of the patch.

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