DOWNHOLE WELL TOOLS AND METHODS OF USING SUCH

Abstract

A downhole tool for use in a gas or oil well is provided. The tool comprising a length of tubing having at least one annular sealing means mounted on the outer surface thereof. The annular sealing means, which are formed from a eutectic/bismuth based alloy, serve to secure the downhole tool in position within an oil or gas well during so that the tool can carry out its function.

Claims

1. A downhole tool for use in a gas or oil well, said tool comprising a length of tubing having at least one annular sealing means mounted on the outer surface thereof and wherein said at least one annular sealing means is formed from a eutectic/bismuth based alloy.

2. The downhole tool of claim 1, wherein the annular sealing means comprises with one or more conduits running substantially parallel to the tubing.

3. The downhole tool of claim 2, wherein the conduits are provided as channels in the inner and/or outer circumferential surface of the annular sealing means.

4. The downhole tool of claim 2, wherein the conduits are provided as through holes in the main body of the annular sealing means.

5. The downhole tool of any of the preceding claims, wherein said at least one annular sealing means comprises multiple component parts which are combinable to form the complete annulus when mounted on the tubing.

6. The downhole tool of any of the preceding claims, further comprising tool engagement means located within the tubing.

7. The downhole tool of claim 6, wherein the tool engagement means are located on the inner surface of the tubing that is proximate to the externally mounted annular sealing means.

8. The tubing of claim 6 or 7, wherein the tubing further comprises a weak point that in use is just above the ‘slump’ line of the set alloy.

9. A well tool deployment adaptor comprising the downhole tool of any of claims 6 or 7.

10. A method of manufacturing a downhole tool for use in a gas or oil well, said method comprising: providing a length of tubing; and mounting at least one eutectic/bismuth based annular sealing means on the outer surface of the tubing.

11. The method of manufacturing a downhole tool of claim 10, wherein the annular sealing means is provided in the form of multiple component parts and the step of mounting the annular sealing means to the tubing involves securing the component parts together around the circumference of the tubing to complete the annulus.

12. The method of manufacturing a downhole tool of any of claim 10 or 11, further comprising providing multiple conduits in said at least one annular sealing means.

13. The method of manufacturing a downhole tool of claim 12, wherein the conduits are provided in the form of channels in the inner and outer surface of the annular sealing means.

14. The method of manufacturing a gas or oil well tubing of claim 12, wherein the conduits are provided in the form of through holes running through the main body of the sealing means.

15. A method of sealing a leak in a completed oil/gas well using the downhole tool according to any of claims 1 to 8 by heating the eutectic/bismuth based annular sealing means in situ to melt the alloy and seal the leak.

16. The method of sealing a leak in a completed oil/gas well of claim 15, wherein a heating tool is deployed down the well to apply heat to the annular sealing means and cause it to melt.

17. The method of sealing a leak in a completed oil/gas well of claim 15, wherein the tubing further comprises heating means that can be activated remotely to melt the alloy.

18. The method of sealing a leak in a completed oil/gas well of claim 17, wherein the heating means are provided by a chemical heat source.

19. A breakable eutectic/bismuth based alloy well plug, said plug comprising: an open-ended tubular plug body having eutectic or other bismuth based alloy mounted on the outside thereof; and wherein passage through the tubular plug body is blocked by a breakable plugging member.

20. The breakable eutectic/bismuth based alloy well plug of claim 19, wherein the breakable plugging member is provided in the form of a burst disc.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The various aspects of the present invention will now be described with reference to the drawings, wherein:

[0061] FIG. 1 is a diagrammatic representation of the key stages of the deployment and operation of the oil/gas well tubing of an embodiment of the first aspect of the present invention;

[0062] FIG. 1a is a diagrammatic representation of an alternative deployment of the tubing with an annular packer;

[0063] FIG. 1b is a diagrammatic representation of a second alternative deployment of the tubing with an annular packer;

[0064] FIG. 2 shows a perspective view of an annular packer being used as a annular sealing means mounted on the outer surface of tubing which can form the basis for a downhole tool in accordance with the present invention;

[0065] FIG. 3 shows an end view of one variant of the annular sealing means shown in FIG. 2;

[0066] FIG. 4 shows an end view of a second variant of the annular sealing means shown in FIG. 2;

[0067] FIG. 5 shows a diagrammatic cross-sectional representation of a well tool deployment adaptor according to the second aspect of the present invention;

[0068] FIG. 5a shows a diagrammatic representation of the key stages of the deployment and operation of a further enhanced embodiment of the second aspect of the present invention;

[0069] FIG. 6 shows a diagrammatic cross-sectional representation of the key stages of the deployment of a straddle downhole tool according to the present invention.

DETAILED DESCRIPTION OF THE VARIOUS ASPECTS OF THE PRESENT INVENTION

[0070] The various aspects will now be described with reference to the Figures, which provide a collection of diagrammatic representations of embodiments of the each aspect of the present invention to aid the explanation of their key features.

[0071] One of the central features of a number of the aspects of the present invention is formation of prefabricated oil/gas tubing with a eutectic/bismuth based alloy annular packer mounted to the said tubing. Although the term annular packer is used it is appreciated that the terms annular sealing means, annular seal and thermally deformable annulus packer may also employed depending on the context of the embodiment being described. The terms can therefore be used interchangeably.

[0072] The term prefabricated is intended to cover situations where the annular packer/annular sealing means is mounted on the tubing either in a factory or on site, but always before the tubing is deployed down a well bore. This is clearly distinct from existing uses of alloy as a sealant, wherein the alloy is deployed separately from the tubing at a later stage—which is usually after completion of the well.

[0073] It will be appreciated that, unless otherwise specified, the materials used to manufacture the components of the various apparatus described hereinafter will be of a conventional nature in the field of oil/gas well production.

[0074] The downhole tools of the present invention utilise alloy annular packers or annular sealing means rather than more traditional mechanical means (e.g. ‘dogs’ or ‘slips’) to retain the tools in position within a well. In order to better understand the annular packers upon which the annular sealing means present invention is based such will now be described with reference to FIGS. 1-4.

[0075] FIG. 2 shows an oil/gas well tubing 1 suitable for use with the downhole tools of the present invention in the form of a length/section of pipe 2 with a eutectic/bismuth based alloy annular packer 3 mounted on the outside thereof.

[0076] Although not shown in the Figures it is envisioned that the externally mounted annular packer might preferably be formed from multiple component parts that combine to surround the length of production pipe 2 so that the process of mounting (and possibly remounting) the annular packer is made easier.

[0077] As will be appreciated from FIG. 1 the diameter of the annular packer 3 is sufficient to provide a close fit with the outer wall of the well 5, which may be provided by a rock formation 4 or as appropriate a well casing or lining.

[0078] In order to explain the use of the tubing 1 reference is made to FIG. 1, which shows three key stages in the working life of the tubing 1. In the first stage the tubing 1, which comprises the section of tubing 2 with the annular packer 3 mounted on the outer surface, is attached to tubing 6 and delivered down the well bore 5 that has been created in the underground formation 4 using conventional means.

[0079] It is appreciated that tubing 1 and 6 are typically connected together above ground and then deployed down the well. However in order to clearly illustrate that tubing 1 and 6 are initially distinct they are initially shown in FIG. 1 as being separate.

[0080] In the reference Figures the tubing 1 is attached to the top of the tubing 6 that is already secured in the well 5. It is envisioned that advantageously the tubing 1 of the present invention may be connected to existing production tubing 6 using a collar joint, for example.

[0081] Once the production pipework, which comprises tubing 1 and 6, has been deployed within the well 5 cement 7 can be poured or pumped into the annular space between the formation 4 and the pipework (or, if appropriate, between a well casing/lining and the pipework). Once set the cement 7 will seal the well 5 so that the only access to the oil/gas deposit is via the production tubing 1, 6.

[0082] In the event that a crack or gap develops in the cement seal and forms a leak a heater 8 can be deployed down the well using a wire line 9 or coil tubing, for example, to a target region inside the tubing 1 that is proximate to the eutectic/bismuth based alloy annular packer 3. Once in place the heater 9 can be activated to melt the alloy 3, which causes it to turn into a liquid and flow into the cracks/gaps in the cement plug 7.

[0083] When the alloy 3 of the annular packer cools it expands and plugs the cracks/gaps and reseals the cement plug 7 and stops the leak.

[0084] It is appreciated that various annular spaces are created during the formation of a well and it is envisioned that the present invention can therefore be usefully employed in variety of different arrangements without departing from the scope of the present invention.

[0085] In the referenced Figures the cement is poured (or pumped) into the annular space after the tubing 1, with its annular packer 3, has been deployed within the well.

[0086] In arrangements where the diameter of the annular packer 3 is close to the internal diameter of the rock formation 4 (or well casing/lining—not shown) it is considered advantageous to provide the annular packer 3 with conduits to facilitate the passage of cement through and around the annular packer 3 so that it can reach the lower regions of the well 5.

[0087] It is envisioned that rather than being deployed above the level of the cement the tubing 1 may also be completely surrounded by and embedded within the cement 7. FIGS. 1a and 1b show such arrangements.

[0088] The embodiment of the tubing shown in FIG. 1a has an annular packer 3 of a reduced diameter that does not extend all the way to the outer formation (or casing). In is envisioned that such embodiment is suitable for sealing micro annuli leaks; such as those formed by constant expansion and contraction of the production tubing (see above).

[0089] The embodiment shown in FIG. 1b has an annular packer 3 with a diameter that extends to the surrounding formation (or casing). It is envisioned that this embodiment is more suitable for repairing cracks that extend across the entire cement seal.

[0090] FIG. 3 shows a first variant of the annular packer 3, which is provided with a plurality of through holes 10, that could be employed as an annular sealing means in the downhole tools of the present invention. The through holes 10 are arranged to permit the passage of wet cement through the main body of the annular packer 3.

[0091] FIG. 4 shows a second variant of the annular packer 3, which is provided with a plurality of channels 11 in the outer surface of the annular packer 3. It is envisaged that both variants might be employed as annular sealing means in the downhole tools of the present invention, however the provision of conduits is not considered crucial to the operation of the downhole tools.

[0092] Turning now to FIG. 5, in which is shown an embodiment of a downhole tool of the present invention in the form of a well tool deployment adaptor 12 according to a second aspect of the present invention. It will be appreciated that the main components of the adaptor 12 are essentially the same as the tubing shown in FIGS. 1-4, in that it comprises a length/section of tubing 13 with a eutectic/bismuth based annular packer 14 mounted on the outside thereof.

[0093] However the adaptor 12 further comprises tool engaging means 15 located inside the adaptor. The tool engaging means 15 can be of any form provided they are capable of securely engaging/locating a complementary tool within the tubing 13.

[0094] In use the adaptor 12 is deployed within an existing well tubing structure (e.g. production tubing) and is maintained in place by heating the region of the adaptor proximate to the eutectic/bismuth based alloy and then allowing the alloy cool and fix the adaptor in place within the well by the force of the expanded alloy pressing against the existing well tubing (not shown).

[0095] The adaptor is provided with a skirt or ‘cool area’ 18 to slow the flow of the melted alloy 14 so that it is not lost down the well but instead cools in the target region. Further details of suitable skirting can be found in International PCT Application No. WO2011/151271. It is appreciated that the well fluids will act to quickly cool the heated alloy ensuring that it is not is a flowing state for very long.

[0096] Although not shown, it is envisaged that the skirt may further comprise a swellable or intumescent material that is caused to expand when exposed to heat. This further enhances the ability of the skirt to check the flow of the molten alloy so that it can cool in the target region.

[0097] Once the adaptor is secured in place within the well a complementary tool 16 (examples of which include a valve, a flow rate meter or even a temporary, breakable plug) can be delivered down the well using delivery means 17 (e.g. wire line).

[0098] When the time comes to remove the adaptor 12 a heater can be deployed down the well to engage with the tool engaging means 15, heat the alloy and retrieve the adaptor 12.

[0099] FIG. 5a shows a preferred embodiment of the adaptor 12 with the tool engagement means hidden to simplify the diagram. The tubular body of the adaptor is provided with a weakened point 19. During deployment of the adaptor 12 the weakened point is covered by alloy, this gives additional structural support to the adaptor.

[0100] Once in situ, and the alloy has been melted to secure the adaptor in place, the weakened point 19 is revealed by the alloy 14. This enables the top portion 12a of the adaptor 12 to be broken off and removed. The removal of the top portion 12a makes any subsequent operations to remove the adaptor 12 easier due to the reduced amount of tubing that needs to be milled out.

[0101] It is appreciated that the technical benefit achieved by providing the weakened point in the adaptor tubing could also be utilised in other aspects of the present invention—such as the breakable eutectic/bismuth based alloy plug according to the third aspect of the present invention, for example.

[0102] Another embodiment of a downhole tool of the present invention in the form of a straddle 171 will now be described with reference to FIG. 6, which show the key stages of a straddle deployment operation.

[0103] The straddle 171 is configured to be deployable within a well tubing 170 (e.g. a well casing, well lining or other production tubing). The straddle 171, which essentially comprises a length of tubing, is provided with two eutectic/bismuth based annular sealing means 172, 173.

[0104] The annular sealing means 172, 173 are located at the leading and trailing end regions of the straddle. However it is envisaged that additional annular sealing means may be provided at points along the length of the straddle's outer surface as required (i.e. when the straddle is of an extended length.

[0105] Once the straddle reaches the target region within the well a heater 174 can be operated to heat the annular sealing means so that annular seals can be formed between the outer surface of the straddle 171 and the inner surface of the outer tubing 170.

[0106] In FIG. 6 the embodiment shown has uses a heater that has two separate heating modules 175, 176. In this way the straddle can be deployed by the heater in a single deployment (i.e. without having to retrieve the heater from the well and recharge the heat source. It is envisaged that the heating modules are preferably chemical heat sources, although it is appreciated that alternative heat sources could also be employed without departing from the scope of the present invention.

[0107] Once the first heating module 175 is aligned with the annular sealing means 172 located at the trailing end of the straddle 171 the heat is activated and the alloy of the annular sealing means 172 is melted and allowed to sag. As the alloy sags and cools an annular seal is formed between the straddle 171 and the outer tubing 170.

[0108] Although not shown in figures it is envisioned that the heater and the straddle are preferably deployed down the well as a single unit in which the first heating module 175 is aligned with annular sealing means 172.

[0109] Once the first heating module 175 has finished and the upper annular seal 172a has been formed, and the straddle is secured in position in the well, the heater 174 can be detached from the straddle 171 by partially retrieving the heater using the wire line.

[0110] Once the heater has been released from the straddle it can be deployed further down the well via the internal cavity of the straddle 171. As will be appreciated although the heater 174 can be delivered using standard delivery means such as a wire line, alternative systems can be used without departing from the present invention.

[0111] Once the second heating module 176 is aligned with lower annular sealing means 173 the heating module can be activated and the process of forming an annular seal is repeated at the lower end of the straddle to form the annular seal 173a.

[0112] Once the second annular seal 173a has been set the heater 174 is retrieved from the well using the wire line, for example.

[0113] Although the straddle shown in FIG. 6 is provided with two annular sealing means it is envisioned that additional annular sealing means may be provided on the outer surface thereof. It is further envisioned that the heater used to deploy such straddles would advantageous be provided with a corresponding number of heater modules so that the straddle can be fully deployed by the heater in a single visit.