Downhole tool

Abstract

A fishing tool is provided. The fishing tool comprises a drive end to be connected to an associated running structure, and an engagement end configured to engage with a fish located downhole, wherein the engagement end comprises a rotationally self-aligning guiding structure.

Description

[0001] DOWNHOLE TOOL

[0002] The present invention relates to a downhole tool. In particular, the present invention relates to a downhole tool configured to intervene with fish located in a borehole.

[0003] Downhole tools have been developed for fishing purposes. Within the context of this application, a fish is any object left downhole. For example, a fish may consist of junk metal, a hand tool, a length / part of a drill pipe or drill collars, an intervention tool, a straddle, a plug, or an expensive MWD and directional drilling package. Once the component is lost, it is properly referred to as simply "the fish". A fish is thus anything put into the hole, which is accurately measured and sketched so that appropriate fishing tools can be selected if the item must be fished out of the hole.

[0004] Existing fishing tools are lowered downhole until they reach the position of the fish. Upon engagement, the fishing tool may be withdrawn from the wellbore, thus carrying the fish to the surface. One such example is described in US4124245.

[0005] While existing fishing tools have proven to be useful, problems may arise if the fish is not centrally aligned in the borehole. In such cases, the fishing tool may not be able to connect to the fish, thus preventing proper removal. This problem is specifically noted in horizontally drilled wellbores, where gravity cannot be used to assist the fishing tool to align with the fish.

[0006] In view of the above, there is a need for improvements.

[0007] An object of the present invention is to provide a new type of fishing tool which is improved over prior art and which eliminates or at least mitigates the drawbacks discussed above. More specifically, an object of the invention is to provide a fishing tool that automatically aligns with the fish. These objects are achieved by the technique set forth in the appended independent claims with preferred embodiments defined in the dependent claims related thereto.

[0008] P2928PC00 According to a first aspect, a fishing tool is provided. The fishing tool comprises a drive end to be connected to an associated running structure and an engagement end configured to engage with a fish located downhole. The engagement end comprises a rotationally self-aligning guiding structure.

[0009] Moreover, the engagement end may be configured to engage and disengage with the fish.

[0010] Furthermore, the running structure may be a wireline.

[0011] The guiding structure may be rotationally self-aligning in relation to the drive end. This is advantageous in that any undesired twisting or rotation of the fishing tool will have no effect on the guiding structure, as this automatically rotates into alignment with the fish.

[0012] The fishing tool may further comprise a support body extending between the drive end and the engagement end. The support body may comprise a grappling device. This allows for the fish to be easily caught by the fishing tool, ensuring a robust connection until the fish is extracted from the well. Another benefit is that the grappling device does not interfere with the guiding structure.

[0013] The grappling device may comprise a conical drive part, and at least one grapple may be arranged to slide on the conical drive part. This provides for facilitated yet robust actuation of the grappling device.

[0014] The grapples may be in the form of axially moving latching dogs which are configured to slide on the conical drive part.

[0015] The latching dogs may be arranged on the ends of latching fingers which allow the latching dogs to move radially when sliding on the conical drive part.

[0016] The guiding structure is rotationally non-symmetrical. This allows the guiding structure to be designed with a desired orientation, thereby ensuring proper engagement even for large radial distances between the fishing tool and the fish.

[0017] P2928PC00 The engagement end may comprise a support shaft. The guiding structure may be rotationally supported on said support shaft. This provides for simple mounting of the guiding structure to the fishing tool.

[0018] The support shaft may be arranged centrally in said fishing tool. This provides for increased simplicity, using the symmetry of the support shaft.

[0019] In addition, the fishing tool may have a longitudinal axis.

[0020] Also, the fishing tool may have a centre axis extending along the longitudinal axis.

[0021] Moreover, the support shaft may extend along the longitudinal axis or the centre axis.

[0022] Additionally, the fishing tool may be any kind of intervention tool.

[0023] Furthermore, the fishing tool may have the drive end and the engagement end, the drive end of the tool being connected with the running structure, and the drive end of the tool comprises an electric motor powered through the running structure in the form of a wireline.

[0024] In addition, the drive end of the fishing tool may comprise a pump driven by the electric motor.

[0025] Also, the fishing tool may be a wireline fishing tool.

[0026] Moreover, the drive end of the fishing tool may comprise a driving unit such as a conveyance unit, e.g. a tractor.

[0027] Further, the motor may rotate a rotating shaft.

[0028] Additionally, the fishing tool may comprise a rotation-to-linear converter for converting the rotation of the motor to an axial movement for sliding the grapple along the conical drive part and thus into engagement with the fish.

[0029] Furthermore, the rotating shaft may be provided with a threaded section. On the threaded section of the rotating shaft, there is arranged a nut. The threaded section

[0030] P2928PC00 and the nut form a rotation-to-linear converter, which converts the rotary movement of the electric motor into a liner movement for sliding the grapple along the conical drive part and thus into engagement with the fish.

[0031] In addition, the linear movement of the nut may be parallel to a longitudinal axis of the tool.

[0032] Moreover, the pump may form the rotation-to-linear converter.

[0033] The guiding structure may have a centre of mass located off-centre in relation to a longitudinal axis of the fishing tool. This allows the guiding structure to self-align using gravity only, thus requiring no additional biasing members or parts.

[0034] The rotationally self-aligning guiding structure may be arranged further away from the drive end than a middle part of the fishing tool.

[0035] The guiding structure may comprise an apex. The apex may be efficient in entering the fish, thereby also guiding the fishing tool further into the fish for proper engagement.

[0036] The apex may be located at an angle of 160° - 200° from the centre of mass, i.e. vertically above the longitudinal axis. This provides efficient engagement for fish arranged vertically above the fishing tool.

[0037] Moreover, the apex may be located at an angle of 160° - 200° from the centre of mass along a circle, such as a circumference of the guiding structure, having a circle centre coincident with the centre axis of the fishing tool.

[0038] The apex may be located -20° - +20° from the centre of mass, i.e. to the side of the longitudinal axis. This provides efficient engagement for fish arranged to the side of the fishing tool.

[0039] Furthermore, the apex may be located at an angle of -20° - +20° from the centre of mass along a circle, such as a circumference of the guiding structure, having a circle centre coincident with the centre axis of the fishing tool.

[0040] P2928PC00 The apex may be located at an angle of 70° - 110° from the centre of mass, i.e. vertically below the longitudinal axis. This provides efficient engagement for fish arranged vertically below the fishing tool.

[0041] Moreover, the apex may be located at an angle of 70° - 110° from the centre of mass along a circle, such as a circumference of the guiding structure, having a circle centre coincident with the centre axis of the fishing tool.

[0042] The guiding structure may comprise a hollow portion. This allows for the efficient, simple and cost-effective provision of an eccentric centre of mass.

[0043] According to a second aspect, a method for providing a fishing tool is provided. The method comprises providing a guiding structure having an eccentric centre of mass and rotationally supporting the guiding structure at an engagement end of the fishing tool such that the guiding structure is self-aligning.

[0044] According to a third aspect, a method for operating a fishing tool is provided. The method comprises providing the fishing tool according to the method of the second aspect, engaging the fishing tool with a downhole fish, and extracting the fishing tool and the engaged fish from downhole.

[0045] Embodiments of the invention will be described in the following; references being made to the appended diagrammatical drawings which illustrate non-limiting examples of how the inventive concept can be reduced into practice.

[0046] Fig. 1 is a schematic view of a borehole with a fishing tool approaching a fish according to one example,

[0047] Fig. 2a is a cross-sectional side view of a fishing tool prior to engaging a fish according to an embodiment,

[0048] Fig. 2b is a cross-sectional side view of the fishing tool shown in Fig. 2a arranged in position to engage the fish,

[0049] Fig. 2c is a cross-sectional side view of the fishing tool shown in Figs. 2a-b when engaged with the fish,

[0050] P2928PC00 Fig. 3 is an isometric view of a part of a fishing tool according to an embodiment,

[0051] Fig. 4 is a cross-sectional side view of a guiding structure of a fishing tool according to an embodiment,

[0052] Figs. 5a-c are front views of a guiding structure according to different embodiments,

[0053] Fig. 6 is a schematic flow chart of a method for providing a fishing tool according to an embodiment, and

[0054] Fig. 7 is a schematic flow chart of a method for operating a fishing tool according to an embodiment.

[0055] Hereinafter, certain embodiments will be described more fully with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention, such as it is defined in the appended claims, to those skilled in the art.

[0056] In Fig. 1, a drilled well 1 is shown. The well 1 consists of a drilled borehole 3 leading down into the bedrock to extract gas and / or oil. The well 1 may be reinforced and / or cased or lined as is well-known in the art.

[0057] Fig. 1 shows the well 1 in a position where it is subjected to a submerged fishing tool 100. The fishing tool 100 is configured for intervening with a fish 200 left downhole.

[0058] The fishing tool 100 is connected to a running structure such as a wireline 20, i.e. a cable adapted to follow the fishing tool 100 up and down the well 1. The wireline 20 is attached to the fishing tool 100 at one end, while the other end of the wireline 20 is connected to some equipment above the well 1. In this way, the position of the fishing tool 100 in the well 1 can be controlled by manoeuvring the wireline 20.

[0059] P2928PC00 In addition to mechanically guiding the fishing tool 100, the wireline 20 may be electrically coupled to the fishing tool 100 so that the fishing tool 100 can be powered via the wireline 20. The wireline 20 thus provides the fishing tool 100 with the necessary power so that the fishing tool 100 can perform its intended fishing operation downhole.

[0060] In the shown example, the wireline 20 forms a running structure used to follow the fishing tool 100 up and down a borehole 3 and to pull the fishing tool 100 out of the well 1. It should, however, be realised that the running structure 20 may be implemented in many different ways, such as by coiled tubing, etc.

[0061] Now turning to Figs. 2a-c, further details of the fishing tool 100 are shown and especially during a fishing operation. The fishing tool 100 has a drive end 102 arranged closest to the surface and an engagement end 104 arranged closest to the fish 200. Hence, the drive end 102 is a proximal end, while the engagement end 104 is a distal end. Typically, the drive end 102 is in direct connection with the running structure 20, or it may be indirectly connected to the running structure 20 via one or more downhole tools such as an anchoring unit, a stroking unit, a driving unit or a conveyance unit, e.g. a tractor, etc. The stroking unit provides an axial force for pulling the fish, the anchoring unit or conveyance unit provides an anchoring of the fishing tool 100 downhole, and the driving unit or conveyance unit propels the fishing tool 100 forward in the well 1, especially during a horizontal part of the well 1.

[0062] A support body 106 extends between the drive end 102 and the engagement end 104. The length of the support body 106 may be of any suitable magnitude, but preferably the support body 106 is as short as possible while still providing an axial length required to accommodate various functions of the fishing tool 100, as will be described later.

[0063] In the shown example, the borehole 3 is substantially horizontal. The fishing tool 100 is arranged at the vertical bottom of the borehole 3, which may be cased with a tubing. As is also shown in Fig. 2a, the fish 200 is arranged centrally in the borehole 3, which means that the fishing tool 100 is non-aligned with the fish 200. The fishing tool 100 may also be off-centre of the borehole 3 / tubing, and the fish may be arranged more coincident with the centre of the borehole 3 / tubing.

[0064] P2928PC00 In Fig. 2a, the fishing tool 100 is shown in a position approaching the fish 200. The engagement end 104 of the fishing tool 100 comprises a guiding structure 110. The guiding structure 110 is preferably non-symmetrical and configured to guide the fishing tool 100 into an engagement position relative the fish 200.

[0065] The guiding structure 110 is spear-shaped, i.e. it comprises an apex 112. The apex 112 is arranged off-centre in relation to a longitudinal axis L of the fishing tool 100. The guiding structure 110 is further oriented such that the apex 112 is aligned with the fish 200, i.e. the location of the apex 112 is such that the apex 112 will meet the fish 200.

[0066] As is indicated in Fig. 2a, when the fishing tool 100 reaches the fish 200, the apex 112 of the guiding structure 110 will be received by an opening in the fish 200. A conical shape (or rather an oblique conical shape) of the guiding structure 110, i.e. slanted side walls 114, will guide the front part of the fishing tool 100 further into the fish 200, thereby causing the front part of the entire fishing tool 100 to move vertically upwards in the horizontal borehole 3. Hence, in order to engage with the fish 200 it is required that the apex 112 will actually be aligned with the opening of the fish 200. Appropriate location of the entire fishing tool 100 is achieved by the fishing tool 100 driving further into the fish 200 and using the slanted side walls 114 of the guiding structure 110 to move the fishing tool 100.

[0067] Immediately behind the guiding structure 110, a grappling device 120 is provided. At least the grappling device 120 of the front part of the fishing tool 100 will enter the fish 200 to a position indicated in Fig. 2b.

[0068] The grappling device 120 preferably forms part of the support body 106, optionally it may form part of the engagement end 104. The grappling device 120 comprises a conical drive part 122 and one or more moveable grapples 124 arranged on the exterior side of the conical drive part 122. The conical drive part 122 extends along the longitudinal axis L to the guiding structure 110, at which interface the conical drive part 122 has a maximum diameter. Hence, the conical drive part 122 forms an end part of the support body 106. The grapple(s) 124 are in the form of axially moving latching dogs which are configured to slide on the conical drive part 122. The latching dogs may be arranged on the ends of latching fingers which allow the latching dogs to move radially when sliding on the conical drive part 122.

[0069] P2928PC00 The idle position of the grapple(s) 124 is defined by a stop flange 126, behind which the grapple(s) 124 cannot move. The diameter of the stop flange 126 is further dimensioned to be greater than the fish 200, such that the stop flange 126 will also form a stop for the fishing tool 100 when it enters the fish 200.

[0070] For robust engagement with the fish 200, the grapple(s) 124 will be actuated to move forward, i.e. towards the guiding structure 110. For this, any kind of actuator 130 can be used, such as an electrically powered actuator, a hydraulic actuator, or an electromechanical actuator. Optionally, the grapple(s) 124 may be self-actuated by providing a pushing force on the stop flange 126 caused by the fishing tool 100 being urged to move further into the fish 200.

[0071] The actuator 130 may be a rotation-to-linear convertor converting rotation of an electric motor to an axial movement for sliding the grapple(s) 124 along the conical drive part 122 and thus into engagement with the fish 200. The rotating shaft is provided with a threaded section. On the threaded section of the rotating shaft, a nut is arranged. The threaded section and the nut form a rotation-to-linear converter which converts the rotary movement of the electric motor into a liner movement for sliding the grapple(s) 124 along the conical drive part 122 and thus into engagement with the fish 200. The linear movement of the nut is parallel to the longitudinal axis L of the tool 100. The pump may also form the rotation-to- linear converter.

[0072] An engagement position of the grapple(s) 124 is shown in Fig. 2c. In this position, the grapple(s) 124 has / have been urged forward, moving along the conical drive part 122, thereby extending the diameter of the grapple(s) 124 until it / they come(s) into contact with the interior of the fish 200. The grapple(s) 124 may be provided with grooves or teeth 128 in order to create a robust engagement with the fish 200. Upon proper engagement with the fish 200 after the grapple(s) 124 has / have been brought into engagement, the fishing tool 100 can be pulled up, thereby bringing the fish 200 to the surface.

[0073] To further explain the fishing tool 100, it is realised that the location of the fish 200 can be off-centre with regard to the longitudinal axis L of the fishing tool 100. It is further realised that a symmetrical fishing tool 100 having the apex 112 of the guiding structure 110 coinciding with the longitudinal axis L of the fishing tool 100 may fail to engage with the fish 200.

[0074] P2928PC00 The guiding structure 110 is therefore configured as an oblique cone, which is shown in Fig. 3. It should be noted that in the figure, the grapple(s) and the stop flange are omitted. This means that the apex 112 will be displaced radially in relation to the longitudinal axis L. In the shown example, which also corresponds to the embodiment described with reference to Figs. 2a-c, the apex 112 is located vertically above the longitudinal axis L. Further, in order to ensure the correct orientation of the guiding structure 110, the guiding structure 110 is rotationally self-aligning. Preferably, the guiding structure 110 is rotationally self-aligning with regard to the rest of the fishing tool 100, such as the drive end 102. This means that even if the fishing tool 100 gets twisted or starts to rotate, the desired position of the apex 112 will always be ensured. The rotationally self-aligning guiding structure 110 is arranged further away from the drive end 102 than a middle part of the fishing tool 100.

[0075] Self-aligning of the guiding structure 110 is preferably accomplished by allowing the guiding structure 110 to be rotationally supported on the engagement end 104, and by designing the guiding structure 110 such that its centre of mass causes an automatic rotation of the guiding structure 110. The guiding structure 110 is thus rotationally non-symmetrical due to its oblique shape.

[0076] The eccentric centre of mass may be achieved in various ways, for example, by using different materials or densities across the guiding structure 110 or a mass arranged in the guiding structure 110 to provide extra weight in that part and ensure the position of the centre of mass. The mass may be made of a material having a higher density than the material of the remaining part of the guiding structure 110. In the shown example, the guiding structure 110 comprises a hollow portion 116. While the bottom part of the guiding structure 110 is solid, the upper part, at which the apex 112 is located, is formed by substantially less material. In fact, the upper part of the guiding structure 110 comprises a frame structure 118 forming a robust and rigid definition of the apex 112, although being of substantially less weight than the bottom portion of the guiding structure 110.

[0077] In Fig. 4, the fishing tool 100, in particular the engagement end 104, is shown in cross-section. The engagement end 104 comprises a support shaft 140. The guiding structure 110 is rotationally supported on the support shaft 140, and a bearing may be arranged therebetween. Preferably, the support shaft 140 is

[0078] P2928PC00 arranged centrally in the fishing tool 100, such that the support shaft 140 extends symmetrically along the longitudinal axis L. A key part 142 is axially clamped on the support shaft 140, and the guiding structure 110 is attached to the key part 142, for example, using a screw 144. The axial clamping of the key part 142 prevents the guiding structure 110 from moving axially off the support shaft 140. Notably, the key part 142 is free to rotate around the support shaft 140. Axial clamping of the key part 142 may, for example, be accomplished by providing a radial groove in the support shaft 140.

[0079] Now turning to Figs. 5a-c, some examples of the guiding structures 110 will be described. As explained above, the guiding structure 110 has a centre of mass M located off-centre in relation to the longitudinal axis L of the fishing tool 100.

[0080] In Fig. 5a, a guiding structure 110 is shown where the apex 112 is located vertically above the centre of mass M. Preferably, as measured from the longitudinal axis L, the apex 112 is arranged at an angle of 160° - 200°, preferably around 180°, from the centre of mass M. Thus, the apex 112 is located at an angle of 160° - 200° from the centre of mass M along a circle, such as a circumference of the guiding structure 110, and the circle having a circle centre coincident with the centre axis of the fishing tool 100.

[0081] In Fig. 5b, a guiding structure 110 is shown where the apex 112 is located vertically above and sideways of the centre of mass M. Preferably, as measured from the longitudinal axis L, the apex 112 is arranged at an angle of 70° - 110°, preferably around 90°, from the centre of mass M.

[0082] In Fig. 5c, a guiding structure 110 is shown where the apex 112 is located vertically above the centre of mass M but vertically below the longitudinal axis L. Preferably, as measured from the longitudinal axis L, the apex 112 is arranged at an angle of -20° - +20°, preferably around 0°, from the centre of mass M.

[0083] In Fig. 6, a method 300 for providing a fishing tool 100 is schematically shown. The method 300 comprises providing 302 the guiding structure 110 having an eccentric centre of mass M and rotationally supporting 304 the guiding structure 110 at the engagement end 104 of the fishing tool 100 such that the guiding structure 110 is self-aligning.

[0084] P2928PC00 The centre of mass M may be provided by a mass, such as the key part 142. Even though not shown, the mass may be rotationally arranged within the guiding structure 110, and the angle along circumference of the guiding structure 110 may be controlled by a control unit so as to move the centre of mass M, e.g. from a position shown in Fig. 5a to a position shown in Fig. 5b or 5c. The control unit may be controlled from the surface, or the fishing tool 100 may be preprogrammed to try different angles between the apex 112 and the centre of mass M downhole if not successful in the pre-set position, i.e. if the fish 200 is not arranged off-centre as predicted. By changing the position of the mass, the centre of mass M is also changed, and the guiding structure 110 is still self-aligning.

[0085] In Fig. 7, a method 310 for operating a fishing tool 100 is schematically shown. The method 310 comprises providing 300 the fishing tool 100 according to the method 300 described with reference to Fig. 6. The method 310 further comprises engaging 312 the fishing tool 100 with a downhole fish 200 and extracting 314 the fishing tool 100 and the engaged fish 200 from downhole.

[0086] Modifications and other variants of the described embodiments will come to mind to one skilled in the art having benefit of the teachings presented in the foregoing description and associated drawings. Therefore, it is to be understood that the embodiments are not limited to the specific example embodiments described in this disclosure, and that modifications and other variants are intended to be included within the scope of this disclosure.

[0087] Furthermore, the labelling of a first element does not imply the presence of a second element and vice versa.

[0088] It is to be noted that the word "comprising" does not necessarily exclude the presence of other elements or steps than those listed.

[0089] 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.

[0090] It should further be noted that any reference signs do not limit the scope of the claims.

[0091] P2928PC00 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.

[0092] Although features have been shown and described, it will be understood that they are not intended to limit the claimed invention, and it will be made obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the claimed invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense. The claimed invention is intended to cover all alternatives, modifications, and equivalents.

[0093] P2928PC00

Claims

Claims1. A fishing tool (100) comprising a drive end (102) to be connected to an associated running structure (20), and an engagement end (104) configured to engage with a fish (200) located downhole, characterized in that the engagement end (104) comprises a rotationally self-aligning and non-symmetrical guiding structure (110).

2. A fishing tool according to claim 1, wherein the guiding structure (110) is rotationally self-aligning in relation to the drive end (102).

3. A fishing tool according to claim 1 or 2, further comprising a support body (106) extending between the drive end (102) and the engagement end (104), and wherein the support body (106) comprises at least one grappling device (120).

4. A fishing tool according to claim 3, wherein the grappling device (120) comprises a conical drive part (122), and wherein at least one grapple (124) is arranged to slide on the conical drive part (122).

5. A fishing tool according to any of the preceding claims, wherein the engagement end (104) comprises a support shaft (140), and wherein the guiding structure (110) is rotationally supported on said support shaft (140).

6. A fishing tool according to claim 5, wherein the support shaft (140) is arranged centrally in said fishing tool (100).

7. A fishing tool according to any of the preceding claims, wherein the guiding structure (110) has a centre of mass (M) located off-centre in relation to a longitudinal axis (L) of the fishing tool (100).

8. A fishing tool according to any of the preceding claims, wherein the guiding structure (110) comprises an apex (112).

9. A fishing tool according to claims 7 and 8, wherein the apex (112) is located at an angle of 160° - 200° from the centre of mass (M).P2928PC0010. A fishing tool according to claims 7 and 8, wherein the apex (112) is located at an angle of -20° - +20° from the centre of mass (M).

11. A fishing tool according to claims 7 and 8, wherein the apex (112) is located at an angle of 70° - 110° from the centre of mass (M).

12. A fishing tool according to any of the preceding claims, wherein the guiding structure (110) comprises a hollow portion (116).

13. A method for providing a fishing tool (100), comprising :- providing a guiding structure (110) having an eccentric centre of mass (M) and being rotationally non-symmetrical, and- rotationally supporting the guiding structure (110) at an engagement end (104) of the fishing tool (100) such that the guiding structure (110) is self-aligning.

14. A method for operating a fishing tool (100), comprising :- providing the fishing tool (100) according to the method of claim 13,- engaging the fishing tool (100) with a downhole fish (200), and- extracting the fishing tool (100) and the engaged fish (200) from downhole.P2928PC00

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