Reduced profile alloy-based downhole tool for use in the deployment of alloy within a downhole target region

Abstract

The present invention provides an alloy-based downhole tool, such as a casing patch or a straddle, for use in the deployment of alloy within a downhole target region with a reduced profile. The reduced profile being achieved by forming one or more alloy receiving recesses in the outer surface of the tool's heater receiving tubular body. The recesses can receive low melting alloys that have a melting point of 300°C or less, such as bismuth based alloys. Also provided is a method of manufacturing the downhole tool.

Description

[0001] REDUCED PROFILE ALLOY-BASED DOWNHOLE TOOL FOR USE IN THE DEPLOYMENT OF ALLOY WITHIN A DOWNHOLE TARGET REGION

[0002] Field of the Invention

[0003] The present invention relates to downhole tools capable of deploying alloy within downhole target regions, such as an oil and / or gas wells, so as to facilitate the formation of alloy based plugs and / or seals in said downhole target regions.

[0004] Background of the Invention

[0005] In order to access oil and gas deposits located in underground formations it is necessary to drill bore holes into these underground formations and deploy production tubing to facilitate the extraction of the oil and gas deposits.

[0006] During the creation, operation and abandonment of oil and gas wells there is often the need to deploy a plug within the well or seal off a portion of the well. This can involve securing a tool in position within a downhole target region.

[0007] One common downhole task is the repair of existing well tubing which, due to the downhole environment, can develop fractures / leaks over time. Another common task is to isolate (whether temporarily or semi-permanently) a region of a well from the rest of the production tubing.

[0008] Various downhole tools are currently employed in such tasks. Some of the most commonly used downhole tools include: bridge plugs, patches, scab and straddles. In order to secure the downhole tool within a well, such tools are typically provided with hydraulically actuated means that can be operated to engage with the surface of a surrounding tubing (e.g., a well casing, well liner or production tubing).

[0009] A plurality of these engagement means, which are commonly referred to as ‘dogs’ or ‘slips’, are normally provided on a downhole tool so that once the tool is in place they can be actuated to lock the tool in position relative to the surrounding tubing.

[0010] Once the required task has been completed by the downhole tool, the ‘dogs’ or ‘slips’ can be retracted and the tool can be retrieved from the well.

[0011] Although the ‘dogs’ or ‘slips’ are capable of retaining a downhole tool in position within a well, they do not form a gas tight seal with the surrounding tubing. In view of this, on occasions where a gas tight seal is required the downhole tool is provided with additional sealing means, such as rubber seals. This can increase the possibility of a malfunction of the downhole tool.

[0012] An alternative approach, which has been developed by the applicant, utilises the interesting properties of certain alloys such as eutectic alloys and / or bismuth containing alloys, to help securely locate tools within downhole target regions.

[0013] In particular, published International PCT application No. WO2016 / 024123 discloses a variety of different options for using eutectic / bismuth based alloys provided on the exterior walls of a tubular tool to secure the tool within a downhole target region.

[0014] In operation, a heat source is inserted into the tubular tool and positioned at a point within the tool that is adjacent to the externally mounted alloy. Once in position the heat source is used to melt the alloy, which flows a short distance before it begins to cool and turn back into a solid.

[0015] Through this process the alloy can form a connection between the tubular tool and a nearby surrounding structure, which will typically be a well casing or tubing but could also be the surrounding formation in which the well has been formed.

[0016] In cases where the surrounding structure is a well casing / tubing, the alloy forms a metal to metal connection between the tubular tool and the surrounding well casing / tubing. Once the tubular tool has been secured in place, the heater is retrieved leaving the interior of the secured tool clear. In situations where a plug is required, the lower end of the tubular tool can be capped or blocked off.

[0017] One common problem faced during the above described downhole operations is the step of actually delivering the downhole tool to the target location within the well so that it can be secured in place. This is because the passage of the tool into the well can be impaired by obstacles in the well and / or bends in the well (e.g., deviated wells).

[0018] In order to provide downhole tools with improved manoeuvrability the applicant has developed various ways of reducing the outer diameter of the downhole tool during its delivery down hole. This helps to maximise the clearance between the downhole tool and the wellbore or well casing / tubing, without necessarily sacrificing the tool’s ability to form a metal to metal connection between the tool and the surrounding casing / tubing. With a view to addressing this problem, European Patent No 2935764, which is one of the applicant’s earlier cases, provides a eutectic / bismuth alloy based plugging tool that is provided with a compressible plug portion.

[0019] The compressible plug portion of the described tool is resiliently biased towards a larger outer diameter than the rest of the plug. The compressible plug portion can thereby reduce its outer diameter when it reaches an obstruction within a well and then spring back to its original, larger diameter once it has passed the obstruction. The compressible plug portion thus serves to reduce the clearance between the tool and the surrounding casing / tubing, such that it provides a platform that directs the melted alloy towards the surrounding casing / tubing.

[0020] Also, in order to help minimise the outer diameter of the tool, this earlier tool employs an in-line dump bailer to deliver the alloy into the downhole target region once the tool and its heater are in place rather than having the alloy cast on the outside of the tool.

[0021] Summary of the Invention

[0022] The present invention seeks to provide an alternative solution to the technical problem of delivering sufficient alloy downhole in order to facilitate the formation of the required alloy plug and / or seal within a downhole target region that may have restricted access due to obstructions in the well bore. To this end, the present invention provides an alloy-based downhole tool in accordance with claim 1 .

[0023] The present invention provides an alloy-based downhole tool for use in the deployment of alloy within a downhole target region, said tool comprising a tubular body with alloy provided on the outer surface thereof and wherein the tubular body has an internal space configured to receive heating means capable of melting the alloy; and wherein the outer surface of the tubular body is provided with one or more recesses, said one or more recesses being at least partially filled with the alloy.

[0024] It has been found that, by selectively providing one or more recesses in the outer surface of the tubular body, it is possible to limit the extent to which the overall outer diameter of the tool increases as the quantity of alloy provided on the tubular body is increased. Essentially, pre-forming recesses in the outer surface of the tubular body creates receptacles capable of accommodating alloy within the footprint of the tubular body, which allows for more alloy to be accommodated without proportionally increasing the tool’s outer diameter.

[0025] In the broadest sense of the present invention, the volume of additional alloy storage provided by the recesses is only limited by the need to maintain the structural integrity of the tubular body; both during delivery of the tool downhole and also when the tool is subjected to increased temperatures during the subsequent operation of heating means to melt the alloy.

[0026] By way of an example, it is noted that in the case of tubular bodies formed from mild steel (i.e. , carbon steel), which is a commonly employed material in downhole tubulars, the depth of each recess may extend to a depth of up to 50% into outer surface without negatively impacting the tubular body’s structural integrity.

[0027] However, it is envisaged that the use of alternative structurally stronger materials, such as titanium, may accommodate the use of deeper recesses (e.g., extending up to 80% into the outer surface) without the structural integrity of the tool being compromised.

[0028] Similarly, it is envisaged that up to 80% of the tubular body’s outer surface may be covered in recesses when mild steel is used, whilst tubular bodies formed from titanium may be able to accommodate almost 100% coverage of their outer surface with recesses without compromising their structural integrity.

[0029] It will be appreciated that reducing the overall outer diameter of the downhole tool facilitates an easier passage of the tool down wellbores that may have restricted access (e.g., obstructions in the wellbore and / or a deviated wellbore path).

[0030] Preferably at least one of said one or more recesses may be a groove. It is envisaged that the groove may or may not have a consistent cross-sectional profile, with a profile shape that is rounded, rectangular or triangular.

[0031] It is considered particularly preferable that each alloy receiving groove may have a rounded cross-sectional profile. It is envisaged that forming the groove without internal comers reduces the extent to which the tubular body is structurally weakened by the removal of material in order to form said groove. As noted above, mitigating the weakening impact of the recesses formed in the outer surface of the tubular body is an important consideration in the operation of the present invention. Preferably, said groove may run along the outer surface of the tubular body in a direction that runs parallel to the central axis of the tubular body. It is envisaged that a plurality of such grooves may be provided spaced apart around the outer circumference of the tubular body.

[0032] Alternatively or additionally, said groove may run around the outer circumference of the tubular body in plane that is perpendicular to the central axis of the tubular body. Again, it is envisaged that a plurality of such circumferential grooves may be provided spaced apart along the length of the tubular body’s outer surface.

[0033] It is envisaged that as providing alloy within a circumferential groove increases the prospects of a continuous annular alloy seal being formed around the tubular body, such grooves are considered particularly suitable for downhole tools used to form an annular seal with a surrounding well tubing.

[0034] It is also noted that providing a continuous ring of alloy around the outer surface of the tool enables the quantity of alloy provided on the tubular body to be optimised whilst still achieving an annular alloy seal between the tool and a surrounding well tubing.

[0035] In a further preferred arrangement, said groove may run along the outer surface of the tubular body in a clockwise and / or counterclockwise spiral around the central axis of the tubular body.

[0036] It is envisaged that multiple grooves may be provided in the outer surface of the tubular body to increase the amount of alloy received within the footprint of the tubular body. The grooves may run in parallel to one another on the outer surface of the tubular body.

[0037] Alternatively, the grooves may cross over one another to form a grid-like pattern. To this end, it is envisaged that different groove configurations (i.e., straight groove, circumferential groove, spiral groove) can be used in combination.

[0038] Alternatively or additionally, at least one of said one or more recesses may be a pit. It is envisaged that a variety of shapes and sizes can be used for the pits without departing from the general concept of the present invention. That being to provide receptacles for accommodating additional alloy on the outside of the tool. Examples of possible pit shapes include: square, rectangular, circular, oval and triangular; although it is appreciated that other suitable shapes may be employed without departing from the general concept of the present invention provided they can accommodate alloy.

[0039] Preferably, the tool comprises a plurality of pits arranged in an array on the outer surface of the tubular body; and wherein further preferably the pits in the array may be arranged in a grid formation that extends around the entire outer circumference of the tubular body.

[0040] Again it is envisaged that providing a continuous covering of alloy, received within pits around the outer surface of the tool enables the quantity of alloy provided on the tubular body to be optimised whilst still achieving an annular alloy seal between the tool and a surrounding well tubing.

[0041] As noted above, the depth of each recess is preferably in the range of 50 to 80% of the tubular body. Ultimately, however, the depth of recesses - whether in the form of grooves or pits - will be determined by the material used to form the tubular body and material’s ability to retain its structural integrity once a proportion of tubular body’s outer surface has been cut away or otherwise removed to form the recesses.

[0042] Similarly, recesses may be provided on up to 100% of the outer surface. Although again, the total recess coverage will be determined by the material used to form the tubular body and its ability to retain its structural integrity once a proportion of its outer surface has been removed to form the recesses.

[0043] In order to maximise the space saving effect of the recesses, said one or more recesses may be completely filed with the alloy. Whilst it envisaged that, in some embodiments of the present invention, the alloy may fill the recesses without extending beyond the outer diameter of the tubular body (see Figures 5a and 5b), in some embodiments alloy is preferably cast around the entire outer circumference of the tool’s tubular body.

[0044] Preferably the alloy may be cast along the entire length of the tool. This arrangement is considered suitable for embodiments of the tool that are used in the delivery of alloybased plugs to downhole target regions. This is because larger quantities of alloy are required for these operations. In alternative embodiments the alloy may only be cast at specific locations along the length of the outer surface of the tool. Said specific locations at which the alloy is cast may preferably be selected from: a leading end of the tool; a trailing end of the tool; a mid-point on the tool; and combinations thereof. Such alternative embodiments are considered suitable for downhole operations such as casing patch tools and straddle tools.

[0045] When the positioning of the alloy is focused to specific locations on the tubular body, it is appreciated that the use of circumferential alloy receiving grooves is preferable.

[0046] It is envisaged that although the advantages offered by the present invention are applicable in a variety of downhole alloy deploying tools, casing patch tools and straddle tools are particularly suitable. This is because alloy seals only need to be formed at the ends of the tubular bodies and not along the entire length of these types of tools.

[0047] As such, it is envisaged that the entire quantity of alloy required to form the alloy seals and hold the casing patch or straddle in place can be accommodated within one or more recesses formed in the outer surface of the tubular body. In such embodiments, the alloy has no impact on the overall outer diameter of the tool when it is delivered downhole.

[0048] In preferred arrangement, the tool may comprise a groove that runs around the outer surface of the tubular body at a leading end thereof; and wherein the tool further comprises an open-ended skirt portion extending from the leading end thereof.

[0049] It is envisaged that locating an open-ended skirt portion downhole of the alloy receiving recess(es), such as a groove, helps to quickly facilitate the cooling and re-solidification of the alloy by allowing well fluids to enter the skirt portion and cool the molten alloy more efficiently.

[0050] Although not necessarily essential to the operation of the tool of the present invention, it is envisaged that preferably the alloy may be a eutectic and / or bismuth based alloy. Low melting alloys, which have a melting point of 300°C or less, are also considered suitable for use with the present invention. These low melting alloys are sometimes also referred to as fusible alloys. With that said, it will be appreciated that in order for the alloy to be capable of forming a solid alloy plug within the target region the melting point of the alloy must not be lower than the normal temperature in the downhole target region, which is typically 5 to 50°C.

[0051] Preferably the alloy may be provided in the form of a bismuth based alloy. It is envisioned that the bismuth based alloys may be eutectic or non-eutectic in nature and may also qualify as low melting alloys. Bismuth is particularly preferable because its alloys tend to contract upon melting and expand upon re-solidification, which is considered beneficial when forming alloy plugs / seals.

[0052] Preferably the tubular body of the downhole tool is formed from a metal selected from a group consisting of: mild steel, mild steel (i.e. , carbon steel), stainless steel, titanium, Monel, Inconel, nickel alloys and aluminium. Alternatively, the tubular body is formed from a non-metal selected from a group consisting of: glass reinforced epoxy (GRE) and carbon fibre (high temperature composite).

[0053] The present invention also provides a method of manufacturing an alloy-based downhole tool in accordance with claim 15. It is envisaged that all of the features described with reference to the downhole tool of the present invention also apply to the method of the present invention.

[0054] Brief Description of the Drawings

[0055] The present invention will now be described with reference to the drawings, wherein:

[0056] Figure 1 a shows a diagrammatic cross-sectional view of a known arrangement of downhole tool with alloy cast on the tubular body of the tool;

[0057] Figure 1 b shows a diagrammatic end view of the tool of Figure 1 a;

[0058] Figure 2a shows a diagrammatic cross-sectional view of a downhole tool provided with an alloy in accordance with the present invention;

[0059] Figure 2b shows a diagrammatic end view of the tool of Figure 2a;

[0060] Figure 3 shows a diagrammatic view of another embodiment of the downhole tool of the present invention;

[0061] Figure 4 shows a diagrammatic view of a further embodiment of the downhole tool of the present invention; Figure 5a shows a diagrammatic cross-sectional view of a downhole tool provided with an alloy in accordance with a preferred embodiment of the present invention; and

[0062] Figure 5b shows a diagrammatic end view of the tool of Figure 5a.

[0063] Detailed Description of the Preferred Embodiments

[0064] The present invention relates to downhole tools that are used to deliver alloy down wellbores and other underground conduits as a key stage of deploying an alloy-based seal or plug within a downhole target region. Eutectic alloys, and in particular bismuth based alloys, have been found to form particularly effective seals and plugs in downhole environments, such as in oil and gas wellbores.

[0065] This is due, in part, to the relatively low melting points of these alloys and the unusual negative expansion characteristics expressed by bismuth based alloys, wherein these alloys tend to contract on melting and then expand again upon cooling. These characteristics make bismuth based alloy particularly effective at forming seals / plugs within downhole target regions.

[0066] In order to set downhole alloy seals / plugs, a heater and a quantity of alloy need to be delivered downhole to the target region. Although it is known to deploy the heater and the alloy downhole separately, there are various benefits to delivering the heater and the alloy downhole in the form of a single tool assembly.

[0067] A common configuration of these assemblies is to provide a tubular body, into which a heater is received, with a quantity of bismuth alloy provided on the outer surface thereof. In use, the heater, the tubular body and the alloy are delivered downhole as a single assembly and, once in position with a downhole target region, the heater is operated to melt the alloy, which then cools and expands as it flows away from the heat source to form an alloy seal / plug within the target region.

[0068] As will be appreciated from the example of a pre-existing alloy downhole hole tool 1 shown in Figures 1 a and 1 b, providing the alloy 4 on the outer surface 2a of the tubular body 2 increases the overall diameter d1of the tool 1 .

[0069] For the sake of clarity, alloy 4 is only shown provided around a first end of the tool 1 , which is an arrangement that is commonly employed in downhole operations employing thermally deformable annular packers (TDAPS) such as those described by the current applicant in WO2016 / 024122 A2. However, it should be appreciated that in other alloy delivering tools (e.g., alloy based plugging tools), the alloy may be provided along a greater portion, and possibly all, of the tubular body’s outer surface.

[0070] With that said, regardless of the extent to which the outer surface is covered with an alloy, the internal space 3 of the tubular body 2 is configured to receive a heating tool (not shown) that can be operated to melt the alloy 4 in the formation of an alloy seal or plug.

[0071] The quantity of alloy required for a particular sealing / plugging operation will vary from one operation to the next, with more or less alloy being provided on the outer surface of the tubular body to meet the requirements of any given job. However in cases where there is limited access to the downhole target region, (e.g., due to obstructions in the well bore or simply the fact that the well bore is deviated from the vertical), the freedom to increase the quantity of alloy carried on the tool is limited by a maximum outer diameter of the tool.

[0072] In the past, these restrictions on a tool’s maximum outer diameter have led to alternative approaches for delivering the required alloy to a downhole target region; such as the use of dump bailer located up-hole of the target region to deliver the alloy (see European Patent No 2935764). Whilst dump bailers are an effective way of increasing the quantity of alloy that can be delivered to a downhole target region that has restricted access, is it considered economically beneficial to provide downhole tools with less components.

[0073] The downhole tools of the present invention were developed within this aim in mind. Turning now to Figure 2a and 2b, the technical solution for increasing the alloy capacity of a downhole tool provided by the present invention will now be described.

[0074] As with the downhole tool shown in Figures 1 a and 1 b, the downhole tool 10 of the present invention comprises a tubular body 12 with an internal cavity 13 that is configured to receive a heating tool (not shown). On the outer surface 12a of the tubular body 12 there is provided a quantity of alloy 14, which is preferably a bismuth based alloy. Once again, for the sake of clarity, the alloy 14 is only shown being provided at one end of the tubular body 12. However, it is envisaged that the alloy may extend along a greater portion of the tubular body’s outer surface 12a and possibly even along its entire length.

[0075] Alternatively, as in the case of casing patches and straddles, alloy may be provided at discrete locations adjacent the ends of the tubular body. Ultimately, the extent to which the alloy covers the tubular body 12 is dictated by the type of downhole operation that is to be carried out.

[0076] Similarly, whilst the tubular body 12 is shown as being open at both ends, it is envisaged that in some operations (e.g., the formation of an alloy plug) the leading end (i.e., the end that enters the wellbore first) may be closed such that the tubular body 12 and the alloy 14 combine to plug the wellbore.

[0077] Returning now to the preferred embodiment shown in Figures 2a and 2b, it will be appreciated that the outer surface 12a of the tubular body 12 is provided with a plurality of recesses, which take the form of grooves 15 running parallel to the central axis of the tool 10. Although the grooves 15 are shown as having a triangular cross section, it is envisaged that the grooves may alternatively have other cross-sectional shapes, such as square, rectangular or rounded.

[0078] As can be seen from Figure 2b, forming the grooves 15 in the outer surface 12a of the tubular body 12 enables a larger quantity of alloy 14 to be mounted on the tool 10 within a smaller overall footprint. This space saving is best appreciated by comparing the tool end views shown in Figures 1 b and 2b, which demonstrate the presence of similar quantities of alloy on tools with clearly different outer diameters d1and d2.

[0079] It is envisaged that a variety of different recess configurations can be used in the downhole tools of the present invention to accommodate additional alloy. The total volume of additional alloy that is accommodated within the tubular body recesses depends on the number of recesses and their depth (i.e., how far the recesses extend into the tubular body).

[0080] The quantity of recesses and their respective depths is limited by the need for the tubular body to retain its structural integrity. Whilst casting the alloy on the outer surface of the tubular body may provide structural support during the pre-deployment handling of the tool and its delivery downhole, in many operations (e.g., alloy plug formation) it is important that the tubular body retains its structural strength in the absence of the alloy.

[0081] It is also considered important that the recesses do not weaken the tubular body in such a way that it fails when it is subjected to the heat generated by the heating tool that is received within in the tubular body’s inner cavity.

[0082] Typically the tubular bodies of downhole tools that are used to deploy alloy seals and / or plugs are formed from mild steel, which is capable of retaining its structural strength and heat resilience even when recesses have been provided in its outer surface.

[0083] With that said, by way of a preferred example of a tool with a mild steel tubular body having a typical wall thickness of >2 to % inch (12.7 to 16.9mm), it is envisaged that up to 80% of the outer surface 12a might be provided with recesses. With said recesses having a maximum depth of 50%, that is up to % to % inch (6.35 to 8.45mm).

[0084] However, it is envisaged that using alternative, stronger and / or heavier metals to form the tubular body may facilitate the provision of a greater number of recesses and / or deeper recesses (both of which increase the alloy retaining capacity of the tool) without fatally weaking the tubular body’s structure.

[0085] Further, it is envisaged that the provision of the recesses, which are filed with the lighter alloy instead, serves to make heavier metals more suitable for use in these downhole operations than might have previously been the case (i.e., due to weight restrictions).

[0086] Examples of suitable metal alternatives to mild steel (e.g., J55, N80, L80, C90, C95, T95, P110, Q125) for forming the tubular body of the downhole tool include: titanium (e.g., grades 2, 5, 6, 12), stainless steel (e.g., L80 13Cr, super 13Cr, 22% duplex, 25% super duplex), nickel alloys (e.g., Monel 400, Inconel 718, alloy 925, Hastelloy C-276) and aluminium.

[0087] Non-metal alternatives for the tubular body include glass reinforced epoxy (GRE) and carbon fibre (high temperature composite). It is also envisaged that the shape and spacing of the recesses in the outer surface of a tubular body may optimise the space created for receiving the additional alloy. Figures 3 and 4 show two alternative preferred embodiments of the downhole tool of the present invention, which show different arrangements of the alloy receiving recesses. Once again, for the sake of clarity, the alloy is not shown covering the entire tool so that the recesses can be seen. Preferably, although not essentially, the recesses and the entire outer surface may be covered in alloy.

[0088] In the downhole tool 20 shown in Figure 3, the tubular body 22 is provided with a continuous groove 25 that spirals around the tubular body along its entire length. Alloy 24 is then received within the groove 25. Again, although not shown, it is envisaged that the alloy would fill the entire groove 25 and also cover the outer surface of the tubular body 22.

[0089] In the downhole tool 30 shown in Figure 4, the tubular body 32 is provided with a plurality of pits 34 arranged in an array in the outer surface of the tubular body. It is envisaged that by forming the recesses as a plurality of spaced apart pits 34 the tool’s capacity to receive additional alloy can be increased without impairing the structural integrity of the tool. Although the pits 34 are shown as being lozenge shaped, it is envisaged that a variety of other shapes could be employed without departing from the general concept of the present invention.

[0090] Also, although the pits 34 are shown in an ordered array, it is envisaged that the pits may be arranged in an alternative, possibly random, configuration without departing from the present invention.

[0091] As demonstrated in the preferred embodiment shown in Figures 2a and 2b, the provision of grooves in the outer surface enables the outer diameter of the tool to be reduced (see comparison between Figures 1 b and 2b) whilst maintaining a significant quantity of alloy on the exterior of the tubular body.

[0092] As noted above, it is envisaged that in some embodiments of the present invention, such as casing patches and straddle tools, the quantities of alloy required for the downhole operation is less than in other downhole operations, such as well plug formation. It is envisaged that in such embodiments, an example of which is shown in Figures 5a and 5b for the purposes of comparison, the required payload of alloy 44 can be completely received entirely within the recesses 43 formed in the outer surface of the tubular body 42 of the tool 40. This has the effect of reducing the outer diameter d3of the tool 40 to that of the tubular body 42.

[0093] Once again, although the recesses 15 are shown as grooves with a triangular cross section, it is envisaged that the grooves may alternatively have other cross-sectional shapes, such as square, rectangular or rounded.

Claims

Claims1 . An alloy-based downhole tool for use in the deployment of alloy within a downhole target region, said tool comprising a tubular body with alloy provided on the outer surface thereof and wherein the tubular body has an internal space configured to receive heating means capable of melting the alloy; and wherein the outer surface of the tubular body is provided with one or more recesses, said one or more recesses being at least partially filled with the alloy.

2. The downhole tool of claim 1 , wherein at least one of said one or more recesses is a groove.

3. The downhole tool of claim 1 , wherein each groove has a rounded cross- sectional profile.

4. The downhole tool of claim 2 or 3, wherein said groove runs along the outer surface of the tubular body in a direction that runs parallel to the central axis of the tubular body.

4. The downhole tool of claim 2, wherein said groove runs along the outer surface of the tubular body in a clockwise and / or counterclockwise spiral around the central axis of the tubular body.

5. The downhole tool of any one of the preceding claims, wherein at least one of said one or more recesses is a pit.

6. The downhole tool of claim 5, comprising a plurality of pits arranged in an array on the outer surface of the tubular body; and wherein preferably the pits in the array are arranged in a grid formation that extends around the entire outer circumference of the tubular body.

7. The downhole tool of any one of the preceding claims, wherein said one or more recesses are completely filed with the alloy.

8. The downhole tool of any one of the preceding claims, wherein the alloy is cast around the entire outer circumference of the tubular body.

9. The downhole tool of any one of the preceding claims, wherein the alloy is cast along the entire length of the tool.

10. The downhole tool of any one of claims 1 to 8, wherein the alloy is only cast at specific locations along the length of the outer surface of the tool.11 . The downhole tool of claim 10, wherein said specific locations at which the alloy is cast are selected from: a leading end of the tool; a trailing end of the tool; a mid-point on the tool; and combinations thereof.

12. The downhole tool of any of the preceding claims, wherein the alloy is a low melting alloy that has a melting point of 300°C or less and preferably a eutectic and / or bismuth based alloy.

13. The downhole tool of any one of the preceding claims, wherein the tool is an alloy-based well plugging and / or sealing tool.

14. The downhole tool of any one of the preceding claims, wherein the tool is a casing patch tool or a straddle configured to form alloy seals adjacent to the ends of the tubular body.

15. A method of manufacturing an alloy-based downhole tool for use in the deployment of alloy within a downhole target region, comprising: providing a tubular body with one or more recesses on an outer surface thereof; casting an alloy on the outer surface of the tubular body such that the alloy is received within said recesses.

16. The method of claim 15, wherein the tool is a casing patch or a straddle and the recesses are provided adjacent to either end of the tubular body before the alloy is cast into said recesses.

Images