Technical Field

[0001] The present invention relates to a wellbore fishing tool with a novel design.

Background Art

[0002] Various types of wellbore fishing tools are known. Many use a set of flexible arms to move the gripping elements between the engaged and non-engaged state, for engaging and disengaging a fish inside a wellbore.

[0003] An example of such a fishing tool is presented in WO2019035726, where a set of flexible arms are bent or flexed by engagement with a coned surface.

[0004] An object of the present invention is to provide a fishing tool that is enabled to receive a large-diameter fish.

[0005] A further object may be to provide a fishing tool that is able to grip a small fish, even when exhibiting a large receiving diameter.

[0006] In some situations, a wire can be present in addition to the fish, typically together with the engagement interface of the fish. Such a wire may unintentionally be given slack, such that it falls over and lands partly on the side of the fish. This will add thickness, so that the fishing tool will require additional capability to engage the fish. Thus, conventional fishing tools may then not be able to engage the fish. An object of the present invention may be to provide a fishing tool that is able to engage a fish even where a wire is arranged together with the fish.

[0007] A further object may be to enable release of the fishing tool from the fish after engaging it. Such functionality is typically advantageous if the fish is stuck in the well and the fishing tool is unable to pull the fish.

[0008] Another object may be to provide a fishing tool that may also be used as a running tool for various other wellbore tools.

[0009] Moreover, an even further object may be to provide a fishing tool that can be engaged with a wellbore fish without requirement for axial force against the fish to actuate the engagement. Summary of invention

[0010] According to the present invention, there is provided a wellbore fishing tool configured for engaging and retrieving a fish in a subterranean well. The fishing tool comprises an actuation motor and an actuator member operated in an axial direction by the actuation motor. It further comprises an engagement assembly, wherein the engagement assembly comprises a main body, gripping elements configured to be moved between a non-engaged and an engaged state, and said actuation member between the actuator motor and the gripping elements. The gripping elements connect to the actuation member via a connection hinge.

[0011 ] Various embodiments and advantageous features appear from the dependent claims.

[0012] With the term subterranean well is meant both onshore wells and subsea wells.

[0013] With the term connection hinge is meant that the two elements connected via the connection hinge are two distinct, separate parts that are mutually rotatable with respect to each other. Thus, according to this definition, a flexible element that bends does not fall under this definition.

[0014] It shall be clear to the skilled reader that the term " via a connection hinge" means that the connection hinge is arranged between the gripping elements and the actuation member. Thus, there may also be additional elements arranged between the gripping elements and the actuation member, to transfer an actuation force between the two components.

[0015] Advantageously, the engagement assembly can be spring-less. By stating that the engagement assembly is spring-less is meant that the movement of the gripping elements between the non-engaged and the engaged states is not based on bending components of the engagement assembly. In other embodiments, however, the engagement assembly can be provided with springs. Thus, the engagement assembly may comprise a spring in addition to the connection hinge. [0016] Preferably, the actuation member comprises actuation arms extending parallel to the longitudinal direction of the wellbore fishing tool. In some embodiments, the actuation arms are embedded in arm slots arranged in the main body.

[0017] In some embodiments, the engagement assembly further comprises actuation links that connect to the actuation member with a first connection hinge and to the gripping element with a second connection hinge. This solution enables a translational and partially radial movement of the gripping elements between the nonconnected and connected states. The actuation member can be moved in an axial direction to transmit a moving force onto the gripping elements via the actuation links.

[0018] In some embodiments, as will be discussed in detail further below, the engagement assembly can have only two second inclined guide faces, wherein the said flat planes of which are symmetric about an axially extending center line.

[0019] Preferably, the second sliding faces also extend along respective flat planes. These planes of the respective second inclined guide faces and the respective second sliding faces can advantageously be parallel.

[0020] Advantageously, when in said non-engaged state, the respective actuation links can be arranged at least partially inside the respective arm slots.

[0021 ] Notably, the wellbore fishing tool discussed herein can be made without resilient springs, which are often used in prior solutions. Instead, solid components are used, which can be moved between the non-engaged and engaged state without relying on bending of the components.

Detailed description of the invention

[0022] While various features of the invention have been discussed in general terms above, some more detailed, and non-limiting examples of embodiment will be presented in the following with reference to the drawings, in which

Fig. 1 is a perspective view of a portion of a wellbore fishing tool according to the invention;

Fig. 2 is a cross section side-view through the fishing tool of Fig. 1 ; Fig. 3 is a schematic illustration of a fish situated in a (not shown) well;

Fig. 4, Fig. 5, and Fig. 6 are cross section side-views showing the movement from a non-engaged to an engaged state;

Fig. 7 and Fig. 9 are perspective views showing the non-engaged and the engaged state, respectively;

Fig. 8 and Fig. 10 are front views corresponding to the situations shown in Fig. 7 and Fig. 9, respectively;

Fig. 11 and Fig. 12 are different perspective views, where the gripping elements have been removed for illustrational purpose;

Fig. 13 is a cross section side-view of a portion of the wellbore fishing tool; and

Fig. 14 is a perspective view of an actuator element and actuation member.

[0023] Fig. 1 depicts a wellbore fishing tool 1 according to an embodiment of the present invention. The fishing tool 1 comprises an actuation arrangement 3 that comprises an actuator motor 5. The actuator motor 5 is indicated in the cross-section side-view of Fig. 2. In the shown embodiment, the actuator motor 5 is an electric motor. However, the actuator motor 5 can also be of any other suitable type, for instance a hydraulic motor.

[0024] The actuator motor 5 is configured to provide a linear movement of an actuator element 7.

[0025] In the shown embodiment, the actuator motor 5 connects to the actuator element 7 over a mechanic connection 9. The mechanical connection 9, which transfers actuation movement between the actuator motor 5 and the actuator element 7 can be designed in various ways. One such design is presented in publication WO2019035726. In embodiments where the actuator motor 5 is a rotary motor, the mechanic connection 9 comprises a rotational-to-linear converter 6.

[0026] An axially extending center line A is indicated in Fig. 2.

[0027] The fishing tool 1 has at its front portion an engagement assembly 10, which is configured to engage a fish 15 (Fig. 3). [0028] The actuator element 7 can be moved back and forth along the axial extension of the fishing tool 1 , by operation of the actuator motor 5.

[0029] In the cross-section side-view of Fig. 2 there is shown an outer housing 11 , which in Fig. 1 has been omitted for illustrational purpose.

[0030] The fishing tool 1 further comprises gripping elements 13. The gripping elements 13 are configured to be moved radially inwards for engagement with the fish 15 inside a wellbore. As will be discussed in more detail below, the gripping elements 13 are actuated by operation of the actuator motor 5.

[0031 ] A fish 15 is schematically illustrated in Fig. 3. The fish 15 has a tool-facing end portion with a trumpet-like form. In other words, the fish 15 may typically have been damaged, such that to retrieve the fish 15, the fishing tool 1 must be able to grip over the trumpet-like end portion to obtain a solid grip on the fish 15.

[0032] In another situation, the fish could for instance exhibit different diameters, such that the fishing tool 1 must move over and beyond a large-diameter portion of the fish to engage with a smaller-diameter portion of the fish.

[0033] Fig. 4 to Fig. 6 depict the engagement assembly 10 of the wellbore fishing tool 1 when being moved towards, receiving, and engaging with a fish 15 inside a wellbore (not shown).

[0034] In Fig. 4, the fishing tool 1 is moved towards the fish 15. The fish 15 may for instance be a damaged pipe end, where the end has been squeezed substantially flat, such that the end has a dimension significantly larger than the outer diameter of the pipe.

[0035] The fishing tool 1 has two gripping elements 13. The gripping elements 13 have an inwardly facing gripping surface 13a. The gripping surface 13a may advantageously be provided with a jagged or toothed face for enhancing the engagement with the outer face of the fish 15.

[0036] Preferably, the gripping surface 13a has a curved shape, as appears from the front view of Fig. 10. [0037] The front portion of the fishing tool 1 , which is shown in Fig. 4, has a main body 17. The main body 17 has a front aperture 19, through which the fish 15 passes as the fish 15 is received in the fishing tool 1 .

[0038] Fig. 5 shows the fishing tool 1 in a situation where the fish 15 has entered the fishing tool 1 . The fishing tool 1 comprises an abutment face 21 , against which the fish 15 abuts, as shown in Fig. 5.

[0039] The fishing tool 1 further has an actuation member, in the shown embodiment in form of two actuation arms 23. The actuation member, i.e. the actuation arms 23, connect to the actuator element 7 and can thus be moved back and forth along with the actuator element 7.

[0040] The actuation arms 23 extend parallel to the axial extension of the fishing tool 1 . Moreover, they are arranged within arm slots 25 of the main body 17.

[0041] At a front portion, the actuation arms 23 connect to a respective actuation link 27 with a first connection hinge 29.

[0042] The actuation links 27 connect further to the respective gripping elements 13 with a second connection hinge 31 .

[0043] Advantageously, the first connection hinge 29 can comprise a first connection hinge pin 29a. Moreover, the second connection hinge 31 can comprise a second connection pin 31 a.

[0044] The gripping elements 13 are arranged between a first inclined guide face 33 and a second inclined guide face 35. In the shown embodiment, the first and second inclined guide faces 33, 35 are part of the main body 17. Moreover, the first and second inclined guide faces 33, 35 are parallel with respect to each other.

[0045] The first inclined guide face 33 and the second inclined guide face 35 both extend in a flat plane. In other words, the faces are without curves (extending in two dimensions only). It shall be clear that in other embodiments, the first and/or the second guide face 33, 35 can comprise a curved shape. Moreover, in other embodiments they need not be parallel with respect to each other.

[0046] Furthermore, the gripping elements 13 comprise a first sliding face 37 and a second sliding face 39. The first sliding face 37 abuts against the first guide face 33, while the second sliding face 39 abuts against the second guide face 35. As the skilled person will appreciate by inspection of the drawings, the sliding faces 37, 39 are configured to slide against the guide faces 33, 35 when the actuation arms 23 are actuated back and forth.

[0047] As shown in Fig. 6, when the actuation arms 23 are moved forwards, the gripping elements 13 slide along the opposite and parallel first and second guide faces 33, 35. This movement of the gripping elements 13, continues until they contact the fish 15. Once the gripping elements 13 have made contact with the fish 15, the entire wellbore fishing tool 1 is pulled upwardly (i.e. towards the top of the not-shown well). The second sliding face 39 will then engage with the second guide face 35, which results in an increased radially inwardly directed force from the gripping elements 13 against the fish 15. This provides a secure engagement between the fishing tool 1 and the fish 15, which now can be pulled.

[0048] As appears by comparing Fig. 5 and Fig. 6, in Fig. 6 the position of the fish 15 with respect to the fishing tool 1 is somewhat less inserted. While the fish 15 collided with the abutment face 21 when being inserted into the fishing tool 1 , the fish has moved a distance in the reverse direction as the gripping elements 13 engage the surface of the fish 15.

[0049] Notably, the actuation links 27 pivot with respect to the actuation arms 23, about the first connection hinge 29. The actuation links 27 also pivot with respect to the gripping elements 13, about the second connection hinge 31 . Notably, with the shown embodiment, the gripping elements 13 do not pivot. Instead, the gripping elements 13 are only moved with a translational movement.

[0050] It shall also be noted that when the gripping elements 13 are moved between the non-engaged state, as shown in Fig. 4, and the engaged state, as shown in Fig.

6, no bending occurs. This is different from known solutions, where the gripping elements typically will be arranged on the ends of flexible, bending arms.

[0051] Referring to Fig. 6, there is shown a pulling gap 8a between a part of the actuation arm 23 and a part of the actuator element 7. As discussed above, in this situation the gripping elements 13 are configured to be engaged with the fish 15. When the wellbore fishing tool 1 starts to pull the fish 15, the gripping elements 13 may be forced somewhat into the material of the fish 15. During this engagement- enhancing movement, the pulling gap 8a will ensure that the pulling force can still be transmitted through the main body 17 and not through the actuation arms 23.

[0052] Similarly, in Fig. 4 there is indicated a pushing gap 8b, which enables the pushing gap 8a to be provided when engaging the fish 15.

[0053] Fig. 7 and Fig. 9 depict, with perspective views, the situations shown in Fig. 4 and Fig. 6, respectively. For illustrational purpose, the fish 15 and the outer housing 11 have been omitted in Fig. 7 and Fig. 9.

[0054] Fig. 8 and Fig. 10 illustrate the fishing tool 1 and the fish 15 with a front view, in the situations corresponding to Fig. 7 and Fig. 9. In Fig. 8, the damaged end portion of the fish 15 is illustrated.

[0055] While the embodiment shown inter alia in Fig. 10 is configured to grip onto the cylindrical part of the fish 15, the gripping elements 13 may be designed differently. For instance, the gripping surface 13a may be arranged such that they abut each other when in the engaged state. As the skilled person will appreciate, the gripping surface 13a will then extend radially inwards beyond the part of the gripping elements 13 that abuts against the landing faces 34.

[0056] As perhaps best shown in Fig. 7 and Fig. 9, arranged between the first inclined guide face 33 and the second inclined guide face 35, there is a landing face 34. In the shown embodiment, the landing face 34 is part of the main body 17.

[0057] When the gripping elements 13 have moved a maximum distance radially inwards, they collide with the respective landing faces 34, such that the movement is halted. In the shown embodiment, the landing faces 34 extend axially, i.e. parallel to the longitudinal extension of the engagement assembly 10.

[0058] The shown embodiment involves four landing faces 34, wherein the respective pairs of landing faces 34 each define a force-transmitting bar 36 between each landing face 34 of each pair.

[0059] Fig. 11 and Fig. 12 depict the main body 17 with different perspective views for a better illustration of the first and second guide faces 33, 35, and the landing faces 34. As shown in Fig. 12, the first inclined guide face 33 is interrupted by the arm slot 25. [0060] It should be noted that when pulling the fish 15, the substantial part of the pulling force is not transmitted through the actuation arms 23 and the actuation links 27. Instead, the force is transmitted from the fish 15, through the gripping elements 13, and into the main body 17 via the second guide face 35. In particular, the pulling force is transmitted through the two force-transmitting bars 36. Consequently, the actuation arms 23 and the actuation links 27 need merely be dimensioned for actuation of the gripping elements 13 from the non-engaged state into the engaged state.

[0061 ] At the front end of the fishing tool 1 and attached to the main body 17, there is a front sleeve 41 . The front sleeve 41 has an inwardly facing, circular coned face 41 a that is flush with a circular coned face 17a of the main body 17.

[0062] As appears from the perspective views of Fig. 11 and Fig. 12, the main body 17 has a tubular or cylindrical shape with an inner bore 17b.

[0063] Fig. 13 depicts a portion of the wellbore fishing tool 1 , without the engagement assembly 10. Fig. 14 shows the actuator element 7 with the actuator arms 23 connected to it.

[0064] While the embodiment disclosed above each only includes two gripping elements 13, it shall be clear to the skilled reader that other embodiments may include more, such as three or four gripping elements 13. The two gripping elements 13 of the above embodiments are distributed 180 degrees apart. Embodiments involving three grippers 13 may advantageously be distributed 120 degrees apart, while embodiments with four grippers 13 may be distributed 90 degrees apart. Such angle distribution will, as the skilled person will appreciate, also apply to the respective inclined guide faces and sliding faces.