Tool, system and method for performing fishing operations

Abstract

A fishing tool (1) for performing a fishing operation to recover an object (2) in a subterranean well (3), comprising: an outer shell segment (100); an inner shell segment (200); wherein the tool (1) is configured to be moveable between: a scooping configuration wherein the outer shell segment (100) and the inner shell segment (200) are at least partially overlapping and form an open chamber (1200B) for receiving the object (2) into in use; and a closed configuration wherein the outer (100) and inner (200) shell segments form a closed chamber (1200A) for trapping the object (2) therein in use; wherein the tool (1) is configured to scoop the object (2) into the open chamber (1200B) in use by rotation of the outer (100) and / or inner (200) shell segments; and wherein the tool (1) is configured to move between the scooping configuration and the closed configuration by relative rotation of the outer (100) and inner (200) shell segments.

Description

[0001] TOOL, SYSTEM AND METHOD FOR PERFORMING FISHING OPERATIONS

[0002] FIELD

[0003] The present invention relates to tools, systems and methods for performing fishing operations to retrieve a lost object in a well, for example an oilfield well. More specifically, the present invention relates to retrieving a lost object in a deviated well or a horizontal well.

[0004] BACKGROUND

[0005] In well operations, such as in oil wells, wellbores are drilled deep into the earth. It is highly undesirable to drop tools, equipment, debris or other objects unintentionally into the wellbore.

[0006] In most cases, the object, commonly referred to as a “fish”, must be removed by a process known as “fishing”, such that the fish does not impair functionality of the wellbore, block the wellbore and / or cause damage to equipment installed in the wellbore. By way of example, a fish could be a bolt, pin, nut, hand tool or similar, or a part, valve or instrument dislodged within the well.

[0007] The resting position of the fish may vary depending on the well design - i.e. vertical, deviated, horizontal or complex well trajectory.

[0008] Fishing tools are specialised tools specifically designed to recover lost or stuck objects in the wellbore.

[0009] The wellbore environment is characterised by high pressures, temperatures, and varying borehole geometries, making fishing operations, particularly at deep depths or in complicated well sections, challenging. Conventional fishing tools include overshots, spears, magnets, and junk baskets. If the fish is magnetic, a correspondingly magnetic fishing tool may be used to retain the fish such that it can be brought out of the wellbore. There are some drawbacks to utilising magnetic fishing tools. In some wellbores, such as those comprising significant amounts of ferrous debris, magnetic interference can pose problems when using magnetic fishing tools. Additionally, use of magnetic tools in environments with electronic instrumentation can lead to operational challenges and potential damage to sensitive equipment. Possibly the biggest challenge is that not all dropped objects are magnetic, rendering magnetic tools useless for recovering nonmagnetic objects. Non-magnetic objects that may end up in the wellbore may be made of materials such as aluminium or metal alloys. A considerable drawback of existing fishing tools is that they rely on the object being capable of providing some resistance force such that the tool can grip the object. A loose object is not capable of providing such forces, therefore loose objects will simply be pushed further into the bore hole without being gripped.

[0010] During drilling operations, a drilling cooling and lubrication fluid, commonly called ‘mud’, is circulated which can be used to collect the fish using various techniques. In oil producing well, the reservoir fluids (i.e. oil and / or other fluids such as well stimulation fluids) may be utilised to collect the fish using various techniques. Prior art techniques of using liquids include flushing or sucking the fish into a secure location such that the fish can be retrieved.

[0011] In gas producing wells it is more challenging to retrieve the fish, since there is no liquid in the well which can be used to carry or suck the fish.

[0012] Oilfield wells commonly require mechanical plugs to be set temporarily to allow various well operations to be performed therein. Such well operations may include well testing, well stimulation or similar. Having completed such a well operation, the plug is retrieved to surface or relocated within the well for further well operations. One or more running tools are commonly used to run, set, operate (if necessary) and retrieve the plug. This is typically done via wireline or a tubular work string. The retrievable plug is furnished with a neck, connector or other suitable connecting device capable of being releasably attached to, or separated from, a corresponding connecting device on the running tool.

[0013] A significant problem may arise if an object is dropped or dislodged (unintentionally) into the well so as to block or impede access to the plug. This may render retrieval or relocation of the plug difficult or impossible.

[0014] In a vertical well, the fish may drop until it stops on the plug itself. In a deviated well, the fish may drop until it levels out at a less steep point of the well trajectory, for example at the heel of a horizontal well, or at a point where the fish is caught in sticky material or similar. This may leave some distance between the fish and the plug. Either way, the fish represents an obstacle to the successful connection and retrieval of the plug.

[0015] In vertical wellbores, the fish can often be gripped from above. In horizontal or inclined wellbores, the fish rests on the low side of the wellbore and is difficult to grip onto with equipment travelling along the wellbore. The fishing equipment is advanced using wireline, coil tubing or drill pipe. The skilled person will be aware that a problem with using coil tubing is that “coil tubing lockup” or “compressive lockup” can occur when the tubing becomes so compressed that it can no longer be pushed further into the well. This typically happens because the tubing reaches a critical buckling point due to the combined effects of axial compressive forces and the helical buckling of the coiled tubing. When the tubing can no longer sustain additional compression, it may suddenly release or snap back to relieve the built- up stress, often accompanied by a rapid and uncontrolled movement, commonly known as “release” or “snap-back”.

[0016] When using coil tubing in a horizontal well bore with the fish resting on the low side of the wellbore, the coiled tubing may release close to the fish. Such sudden and powerful release can cause the fish to be “kicked” much further into the wellbore. Furthermore, it may be challenging and time consuming to relocate the fish after it has been kicked further into the wellbore. Using a wireline tractor mitigates this risk, as the tool is then not exposed to such sudden rapid advancements, however advancement of the tool by wireline tractor is more time consuming.

[0017] Most equipment which can be lost inside a wellbore comprises some kind of “fishing neck”. A fishing neck is a preconfigured connection interface which is located at the up-hole end of the tool such that if the tool is lost in the wellbore, a fishing tool may make connection with the known connection interface to pull the tool to the surface. Of course, objects unintentionally dropped into or dislocated in the wellbore are not configured with such fishing necks.

[0018] For the avoidance of doubt, in the present disclosure, the term “fish” refers to any object to be fished from the well, and includes objects dropped into the wellbore as well as objects detached from equipment or tubulars within the wellbore. The term therefore covers components comprising a fishing neck and those not comprising a fishing neck. The term “fish” is intended to cover magnetic and non-magnetic fish.

[0019] Patent document WO2016 / 028155A1 discloses a sealing apparatus, i.e. a plug, designed by the applicant. The document describes a sealing apparatus for use in a well pipe, a system comprising the apparatus and a well pipe, and a method for using the apparatus, the apparatus comprises: -a mandrel arranged around a centre axis through the apparatus; - a radially movable gripping device arranged around the mandrel; - a radially movable packer element arranged around the mandrel; and - an axially movable activation device designed to set up axial forces for activating the apparatus, the apparatus further comprises a radially movable centralizer arranged around the mandrel for centring the apparatus; and - the activation device being operatively connected to the gripping device, the packer element and the centralizer for the respective activation and radial movement of these, via power transmission of said axial forces, between retracted, passive positions and expanded, active positions relative to the centre axis of the apparatus.

[0020] Patent document WO2015047102A1 discloses an electrical manipulation tool for setting, operating, disconnecting and retrieving / relocating the above-mentioned sealing apparatus. It will be understood by a person skilled in the art that the electrical manipulation tool described in W02015047102A1 may also be used to run and operate myriad other tools.

[0021] The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.

[0022] The object is achieved through features, which are specified in the description below and in the claims that follow.

[0023] SUMMARY

[0024] The invention is defined by the independent patent claims. The dependent claims define advantageous embodiments of the invention.

[0025] According to a first aspect of the invention, there is provided a fishing tool for performing a fishing operation to recover an object in a subterranean well, comprising: an outer shell segment; an inner shell segment; wherein the tool is configured to be moveable between: a scooping configuration wherein the outer shell segment and the inner shell segment are at least partially overlapping and form an open chamber for receiving the object into in use; and a closed configuration wherein the outer and inner shell segments form a closed chamber for trapping the object therein in use; wherein the tool is configured to scoop the object into the open chamber in use by rotation of the outer and / or inner shell segments; and wherein the tool is configured to move between the scooping configuration and the closed configuration by relative rotation of the outer and inner shell segments.

[0026] The outer and / or inner shell segments may be segments of shells only at a portion of their longitudinal extent, i.e. they are not necessarily shell segments across their entire length and instead may be complete shells at portions across their longitudinal extent. It will be understood that the outer and inner shell segments are arranged relative to each other such that the non-complete sections are at the same point along the longitudinal axis of the tool.

[0027] The outer shell segment and the inner shell segment may share a central rotational axis.

[0028] The outer shell segment may comprise a cylindrical shell segment. The inner shell segment may comprise a cylindrical shell segment.

[0029] The outer shell segment may comprise a substantially hemicylindrical shell segment. The inner shell segment may comprise a substantially hemicylindrical shell segment.

[0030] In the closed configuration the outer shell segment and inner shell segment may together form a radial wall around the object in use.

[0031] The outer shell segment may comprise an outer shell segment top face. The inner shell segment may comprise an inner shell segment top face. In the closed configuration the outer shell segment top face and / or the inner shell segment top face may at least partially form the closed chamber.

[0032] The outer and / or inner shell segments may comprise a biasing means configured to bias the object towards the open chamber when the object is scooped by the outer and / or inner shell segment in use.

[0033] The fishing tool may further comprise a counter hold sleeve configured to house part of the outer and part of the inner shell segments.

[0034] The counter hold sleeve may further comprise a counter hold sleeve holding portion configured to be held to prevent rotation of the counter hold sleeve in use.

[0035] The counter hold sleeve holding portion may comprise counter hold splines.

[0036] The inner shell segment may protrude from an up-hole end and a down-hole end of the counter hold sleeve. The outer shell segment may protrude from the down-hole end of the counter hold sleeve.

[0037] The fishing tool may further comprise a first friction coupling arranged between the counter hold sleeve and the inner shell segment.

[0038] The fishing tool may further comprise a second friction coupling arranged between the counter hold sleeve and the outer shell segment.

[0039] The fishing tool may further comprise a ratchet device located between the counter hold sleeve and the outer shell segment, wherein the ratchet device is moveable between a locked position and an unlocked position; wherein in the locked position the ratchet device blocks rotation of the outer shell segment in one rotational direction; and in the unlocked position allows rotation of the outer shell segment in both rotational directions.

[0040] An up-hole end of the inner shell segment may comprise an inner shell segment holding portion configured to provide secure engagement for rotation of the inner shell segment in use.

[0041] The inner shell segment holding portion may comprise a plurality of inner shell segment splines.

[0042] The fishing tool may further comprise a determination means for determining if the closed chamber comprises a lost object.

[0043] The determination means may comprise a piston configured to be selectively advanced through the closed chamber.

[0044] The determination means may comprise a camera or other sensor.

[0045] In the closed configuration the piston may at least partially form the closed chamber.

[0046] The fishing tool may further comprise a manipulator configured to be rotatable to advance the piston in use.

[0047] The manipulator may comprise: a manipulator holding portion at or near an uphole end of the manipulator, the manipulator holding portion configured to provide secure engagement for rotation of the manipulator in use; and a threaded portion registered with a threaded portion of the piston, such that rotation of the manipulator advances the piston towards the down-hole end of the tool.

[0048] The manipulator holding portion may comprise a plurality of manipulator splines.

[0049] The manipulator may be arranged on a central longitudinal axis of the tool.

[0050] The fishing tool may further comprise a catching arrangement located at or near a down-hole end of the tool. The catching arrangement may be configured to allow unidirectional passing of the object to be fished in use.

[0051] The catching arrangement may comprise one or more radially outwardly biased fingers configured to move radially inwards to allow the unidirectional passing of the object and to block passing of the object in the opposite direction, in use.

[0052] The outer shell segment may be provided with first and second radially inward protrusions. The inner shell segment may be provided with first and second radially outward protrusions. The radially inward protrusions may be arranged relative to the radially outward protrusions such that in use: the inner shell segment can be rotated without the inward and outward protrusions abutting; and the inner shell segment can be rotated with the inward and outward protrusions abutting thereby also rotating the outer shell segment.

[0053] The first and second inward protrusions may be arranged around 180 degrees apart. The first and second outward protrusions may be arranged around 180 degrees apart. The first and second inward protrusions may be arranged between 170 and 190 degrees apart. The first and second outward protrusions may be arranged between 170 and 190 degrees apart.

[0054] According to a second aspect of the invention, there is provided a system for performing a fishing operation in a wellbore, the system comprising: a fishing tool according to the first aspect of the invention; a running tool; wherein the running tool is configured to attach to the fishing tool in use and advance the fishing tool into the wellbore.

[0055] The running tool may be a wireline or coil tubing tool.

[0056] The system may further comprise said wellbore.

[0057] The wellbore may be a horizontal or deviated wellbore.

[0058] The running tool may comprise an advancement means configured to advance the fishing tool along the wellbore.

[0059] The running tool may comprise a first engagement means configured to engage the inner shell segment to provide selective rotation of the inner shell segment.

[0060] The running tool may comprise a second engagement means configured to engage the outer shell segment to provide selective rotation of the outer shell segment.

[0061] The running tool may comprise a first engagement means configured to engage the inner shell segment and the outer shell segment to provide selective rotation of the inner and outer shell segments.

[0062] According to a third aspect of the invention, there is provided a method of fishing a lost object in a subterranean well, the method comprising the steps of: a. providing a fishing tool according to the first aspect of the invention; b. locating the fishing tool in a subterranean well in the scooping configuration; c. locating the open chamber above the lost object; d. rotating the outer and / or inner shell segment(s) to scoop the object into the open chamber; and e. providing relative rotation of the inner and outer shell segments to move the fishing tool to the closed configuration to capture the object.

[0063] Step b. may further comprise running the fishing tool into the well in the closed configuration and then moving the fishing tool to the scooping configuration.

[0064] Step b. may further comprise running the fishing tool into a horizontal or deviated well.

[0065] Step b. may further comprise running the fishing tool into a well on wireline or on coil tubing.

[0066] Step e. may further comprise rotating the inner shell segment whilst holding the outer shell segment stationary.

[0067] The method may further comprise a step of: f. removing the fishing tool from the subterranean well to recover the lost object.

[0068] According to a fourth aspect of the invention, there is provided a fishing tool for performing a fishing operation to recover an object from a low-side of a horizontal or deviated subterranean well, comprising: a shell segment forming an open chamber for receiving said object into in use; wherein the tool is configured to be moveable between: a high-side configuration in the wellbore wherein the shell segment is located above the object to be recovered; and a low-side configuration wherein the shell segment is located on the low-side of the wellbore; wherein the shell segment is arranged to be rotatable around a central axis of the tool such that the shell segment can scoop the object into the open chamber of the tool as the tool moves from the high-side configuration to the low-side configuration in use.

[0069] The shell segment may be a substantially hemicylindrical shell segment.

[0070] The shell segment may comprise a shell segment top face at least partially forming the open chamber.

[0071] The shell segment may comprise a biasing means configured to bias the object towards the open chamber when the object is scooped by the shell segment in use.

[0072] The fishing tool may further comprise a counter hold sleeve configured to house part of the shell segment.

[0073] The counter hold sleeve may comprise a counter hold sleeve holding portion configured to be held to prevent rotation of the counter hold sleeve in use.

[0074] The counter hold sleeve holding portion may comprise counter hold splines.

[0075] The shell segment may protrude from an up-hole end and a down-hole end of the counter hold sleeve. The fishing tool may further comprise a friction coupling arranged between the counter hold sleeve and the shell segment.

[0076] The fishing tool may further comprise a ratchet device located between the counter hold sleeve and the shell segment, wherein the ratchet device is moveable between a locked position and an unlocked position; wherein in the locked position the ratchet device blocks rotation of the shell segment in one rotational direction; and in the unlocked position allows rotation of the shell segment in both rotational directions.

[0077] An up-hole end of the shell segment may comprise a shell segment holding portion configured to provide secure engagement for rotation of the shell segment in use.

[0078] The shell segment holding portion may comprise a plurality of shell segment splines.

[0079] The fishing tool may further comprise a determination means for determining if the open chamber comprises a lost object.

[0080] The determination means may comprise a piston configured to be selectively advanced through the open chamber.

[0081] The determination means may comprise a camera or other sensor.

[0082] In the high-side configuration and / or the low-side configuration, the piston may at least partially form the open chamber.

[0083] The piston may comprise a cover portion arranged to close the chamber to secure the object within the chamber.

[0084] The piston may comprise an object engagement portion.

[0085] The fishing tool may further comprise a manipulator configured to be rotatable to advance the piston in use.

[0086] The manipulator may comprise: a manipulator holding portion at or near the uphole end of the manipulator, the manipulator holding portion configured to provide secure engagement for rotation of the manipulator in use; and a threaded portion registered with a threaded portion of the piston, such that rotation of the manipulator advances the piston towards the down-hole end of the tool.

[0087] The manipulator holding portion may comprise a plurality of manipulator splines.

[0088] The manipulator may be arranged on the central longitudinal axis of the tool.

[0089] According to a fifth aspect of the invention, there is provided a system for performing a fishing operation in a wellbore, the system comprising: a fishing tool according to the fourth aspect of the invention; and a running tool; wherein the running tool is configured to attach to the fishing tool in use and advance the fishing tool into the wellbore.

[0090] The running tool may be a wireline or coil tubing tool.

[0091] The system may further comprise said wellbore.

[0092] The wellbore may be a horizontal or deviated wellbore. The running tool may comprise an advancement means configured to advance the fishing tool along the horizontal or deviated wellbore.

[0093] The advancement means may be a wellbore tractor.

[0094] The running tool may comprise an engagement means configured to engage the shell segment to provide selective rotation of the shell segment.

[0095] According to a sixth aspect of the invention, there is provided a method of fishing a lost object in a subterranean well, the method comprising the steps of: a. providing a fishing tool according to the fourth aspect of the invention; b. locating the fishing tool in a subterranean well in the high-side configuration with the open chamber above the object; and d. rotating the shell segment to position the tool in the low-side configuration, thereby scooping the object into the open chamber.

[0096] Step b. may further comprise running the fishing tool into the well in a run-in-hole configuration and then moving the fishing tool to the high-side configuration.

[0097] Step b. may further comprise running the fishing tool into a horizontal or deviated well.

[0098] Step b. may further comprise running the fishing tool into the well on wireline or on coil tubing.

[0099] The method may further comprising a step of: e. removing the fishing tool from the subterranean well to recover the lost object.

[0100] BRIEF DESCRIPTION OF THE DRAWINGS

[0101] An embodiment of the invention will now be described with reference to the following drawings, in which:

[0102] Figure 1a shows a side view of a first fishing tool according to the invention, the fishing tool shown in the closed configuration, more specifically in the closed run-in-hole configuration;

[0103] Figure 1b shows a cross-sectional view (cross-section line shown in the end view in Figure 1 g) of the first fishing tool shown in Figure 1a; Figure 1c shows a cross-sectional view through line E-E in Figure 1b;

[0104] Figure 1d shows a cross-sectional view through line F-F in Figure 1b;

[0105] Figure 1e shows a cross-sectional view through line D-D in Figure 1b;

[0106] Figure 1f shows a cross-sectional view through line C-C in Figure 1b;

[0107] Figure 1g shows an end view of the fishing tool shown in Figure 1a;

[0108] Figure 1h shows a cross-sectional view through line G-G in Figure 1b;

[0109] Figure 1i shows a perspective view of the fishing tool shown in Figure 1a;

[0110] Figure 2a shows a side view of the fishing tool shown in Figure 1a, the fishing tool now shown in the scooping configuration, more specifically in the high-side scooping configuration;

[0111] Figure 2b shows a cross-sectional view (cross-section line shown in the end view in Figure 2g) of the first fishing tool shown in Figure 1a;

[0112] Figure 2c shows a cross-sectional view through line E-E in Figure 2b;

[0113] Figure 2d shows a cross-sectional view through line F-F in Figure 2b;

[0114] Figure 2e shows a cross-sectional view through line D-D in Figure 2b;

[0115] Figure 2f shows a cross-sectional view through line C-C in Figure 2b;

[0116] Figure 2g shows an end view of the fishing tool shown in Figure 2a;

[0117] Figure 2h shows a perspective view of the fishing tool shown in Figure 2a;

[0118] Figure 3a shows a side view of the fishing tool shown in Figure 1a, the fishing tool shown in the scooping configuration, more specifically in the low-side scooping configuration;

[0119] Figure 3b shows a cross-sectional view (cross-section line shown in the end view in Figure 3g) of the first fishing tool shown in Figure 1a;

[0120] Figure 3c shows a cross-sectional view through line E-E in Figure 3b;

[0121] Figure 3d shows a cross-sectional view through line F-F in Figure 3b;

[0122] Figure 3e shows a cross-sectional view through line D-D in Figure 3b;

[0123] Figure 3f shows a cross-sectional view through line C-C in Figure 3b;

[0124] Figure 3g shows an end view of the fishing tool shown in Figure 3a;

[0125] Figure 3h shows a perspective view of the fishing tool shown in Figure 3a;

[0126] Figure 4a shows a side view of the fishing tool shown in Figure 1a, the fishing tool shown in the closed configuration, more specifically in the caught closed configuration;

[0127] Figure 4b shows a cross-sectional view (cross-section line shown in the end view in Figure 4g) of the first fishing tool shown in Figure 1a; Figure 4c shows a cross-sectional view through line E-E in Figure 4b;

[0128] Figure 4d shows a cross-sectional view through line F-F in Figure 4b;

[0129] Figure 4e shows a cross-sectional view through line D-D in Figure 4b;

[0130] Figure 4f shows a cross-sectional view through line C-C in Figure 4b;

[0131] Figure 4g shows an end view of the fishing tool shown in Figure 4a;

[0132] Figure 4h shows a perspective view of the fishing tool shown in Figure 4a;

[0133] Figure 5a shows a side view of the fishing tool shown in Figure 1a, the fishing tool shown in the closed configuration, more specifically in the locked closed configuration;

[0134] Figure 5b shows a cross-sectional view (cross-section line shown in the end view in Figure 5g) of the first fishing tool shown in Figure 1a;

[0135] Figure 5c shows a cross-sectional view through line E-E in Figure 5b;

[0136] Figure 5d shows a cross-sectional view through line F-F in Figure 5b;

[0137] Figure 5e shows a cross-sectional view through line D-D in Figure 5b;

[0138] Figure 5f shows a cross-sectional view through line C-C in Figure 5b;

[0139] Figure 5g shows an end view of the fishing tool shown in Figure 5a;

[0140] Figure 5h shows a perspective view of the fishing tool shown in Figure 5a;

[0141] Figure 6a shows a side view of the fishing tool shown in Figure 1a, the fishing tool shown in the closed configuration, more specifically the confirmation closed configuration;

[0142] Figure 6b shows a cross-sectional view (cross-section line shown in the end view in Figure 6g) of the first fishing tool shown in Figure 1a;

[0143] Figure 6c shows a cross-sectional view through line E-E in Figure 6b;

[0144] Figure 6d shows a cross-sectional view through line F-F in Figure 6b;

[0145] Figure 6e shows a cross-sectional view through line D-D in Figure 6b;

[0146] Figure 6f shows a cross-sectional view through line C-C in Figure 6b;

[0147] Figure 6g shows an end view of the fishing tool shown in Figure 6a;

[0148] Figure 6h shows a perspective view of the fishing tool shown in Figure 6a;

[0149] Figure 7a shows the fishing tool of Figure 1a in the closed configuration, more specifically the closed run-in-hole configuration, deployed into a horizontal wellbore;

[0150] Figure 7b shows the fishing tool of Figure 1a in the scooping configuration, more specifically the high-side scooping configuration, deployed into a horizontal wellbore and approaching the lost object to be recovered;

[0151] Figure 7c shows the fishing tool of Figure 1a in the scooping configuration, more specifically the high-side scooping configuration, deployed into a horizontal wellbore and located adjacent the lost object to be recovered;

[0152] Figure 7d shows the fishing tool of Figure 1a in the scooping configuration, more specifically moving between the high-side scooping configuration and the low-side scooping configuration, with the lost object being scooped inside the open chamber of the tool;

[0153] Figure 7e shows a cross-sectional view through the cross-section line shown in Figure 7d;

[0154] Figure 7f shows the fishing tool of Figure 1a in the scooping configuration, more specifically the low-side scooping configuration, with the lost object inside the open chamber of the tool;

[0155] Figure 7g shows the fishing tool of Figure 1a in the closed configuration, more specifically the caught closed configuration, with the lost object inside the chamber of the tool;

[0156] Figure 7h shows the fishing tool of Figure 1a in the closed configuration, more specifically the locked closed configuration, with the lost object inside the chamber of the tool;

[0157] Figure 7i shows the fishing tool of Figure 1a in the closed configuration, more specifically the confirmation closed configuration, with the lost object inside the chamber of the tool;

[0158] Figure 8a shows a side view of the fishing tool of Figure 1a connected to an optional manoeuvring and control tool;

[0159] Figure 8b shows a perspective view of the fishing tool of Figure 1a connected to the optional manoeuvring and control tool shown in Figure 8a;

[0160] Figure 9a shows a side view of a second fishing tool according to the invention in the run-in-hole configuration;

[0161] Figure 9b shows a cross-sectional view (cross-section line shown in the end view in Figure 1g) of the second fishing tool shown in Figure 9a;

[0162] Figure 9c shows a cross-sectional view through line E-E in Figure 9b;

[0163] Figure 9d shows a cross-sectional view through line F-F in Figure 9b;

[0164] Figure 9e shows a cross-sectional view through line D-D in Figure 9b;

[0165] Figure 9f shows a cross-sectional view through line C-C in Figure 9b;

[0166] Figure 9g shows an end view of the fishing tool shown in Figure 9b;

[0167] Figure 9h shows a cross-sectional view through line G-G in Figure 9b; Figure 9i shows a perspective view of the fishing tool shown in Figure 9a;

[0168] Figure 10a shows a side view of the fishing tool shown in Figure 9a, in the high- side configuration;

[0169] Figure 10b shows a cross-sectional view (cross-section line shown in the end view in Figure 10g) of the first fishing tool shown in Figure 9a;

[0170] Figure 10c shows a cross-sectional view through line E-E in Figure 10b;

[0171] Figure 10d shows a cross-sectional view through line F-F in Figure 10b;

[0172] Figure 10e shows a cross-sectional view through line D-D in Figure 10b;

[0173] Figure 10f shows a cross-sectional view through line C-C in Figure 10b;

[0174] Figure 10g shows an end view of the fishing tool shown in Figure 10a;

[0175] Figure 10h shows a perspective view of the fishing tool shown in Figure 10a;

[0176] Figure 11a shows a side view of the fishing tool shown in Figure 9a, in the low- side configuration;

[0177] Figure 11b shows a cross-sectional view (cross-section line shown in the end view in Figure 11g) of the second fishing tool shown in Figure 9a;

[0178] Figure 11c shows a cross-sectional view through line E-E in Figure 11b;

[0179] Figure 11d shows a cross-sectional view through line F-F in Figure 11b;

[0180] Figure 11e shows a cross-sectional view through line D-D in Figure 11b;

[0181] Figure 11f shows a cross-sectional view through line C-C in Figure 11b;

[0182] Figure 11g shows an end view of the fishing tool shown in Figure 11a;

[0183] Figure 11 h shows a perspective view of the fishing tool shown in Figure 11a;

[0184] Figure 12a shows a side view of the fishing tool shown in Figure 9a, in the confirmation configuration;

[0185] Figure 12b shows a cross-sectional view (cross-section line shown in the end view in Figure 11g) of the second fishing tool shown in Figure 9a;

[0186] Figure 12c shows a cross-sectional view through line E-E in Figure 12b;

[0187] Figure 12d shows a cross-sectional view through line F-F in Figure 12b;

[0188] Figure 12e shows a cross-sectional view through line D-D in Figure 12b;

[0189] Figure 12f shows a cross-sectional view through line C-C in Figure 12b;

[0190] Figure 12g shows an end view of the fishing tool shown in Figure 12a;

[0191] Figure 12h shows a perspective view of the fishing tool shown in Figure 12a;

[0192] Figure 13a shows the fishing tool of Figure 9a deployed into a horizontal wellbore, in the run-in-hole configuration;

[0193] Figure 13b shows the fishing tool of Figure 9a deployed into a horizontal wellbore and approaching the lost object to be recovered;

[0194] Figure 13c shows the fishing tool of Figure 9a deployed into a horizontal wellbore and located adjacent the lost object to be recovered, the fishing tool in the high-side configuration;

[0195] Figure 13d shows the fishing tool of Figure 9a deployed into a horizontal wellbore with the lost object being scooped;

[0196] Figure 13e shows a cross-sectional view through the cross-section line AM-AM shown in Figure 13d;

[0197] Figure 13f shows the fishing tool of Figure 9a deployed into a horizontal with the lost object secured in the tool, the tool in the confirmation configuration;

[0198] Figure 14a shows a side view of the fishing tool of Figure 9a connected to an optional manoeuvring and control tool; and

[0199] Figure 14b shows a perspective view of the fishing tool of Figure 9a connected to the optional manoeuvring and control tool shown in Figure 14a.

[0200] For clarity reasons, some elements may in some of the figures be without reference numerals. A person skilled in the art will understand that the figures are just principal drawings. The relative proportions of individual elements may also be distorted.

[0201] DETAILED DESCRIPTION OF THE DRAWINGS

[0202] It should be noted that the cross-hatching shown in Figures 1 b, 1c, 1d, 1e, 1f, 1 h, 2b, 2c, 2d, 2e, 2f, 3b, 3c, 3d, 3e, 3f, 4b, 4c, 4d, 4e, 4f, 5b, 5c, 5d, 5e, 5f, 6b, 6c, 6d, 6e, 6f, 7a, 7b, 7c, 7d, 7e, 7f, 7g, 7h and 7i is shown without different patterns, angles or directions of hatching lines indicating different components, as is standard convention. With this in mind, the skilled person will fully understand the drawings provided.

[0203] Figure 1a shows a first fishing tool 1 according to the invention. The fishing tool 1 is for performing a fishing operation to recover an object (not shown in Figure 1a) in a subterranean well (not shown in Figure 1a). The fishing tool 1 comprises an outer cylindrical shell segment 100 and an inner cylindrical shell segment 200 arranged around a shared central rotational axis. The outer 100 and inner 200 cylindrical shell segments are each substantially hemicylindrical shell segments and are arranged such that they are rotatable relative to each other in use, as will be described in more detail later.

[0204] The fishing tool 1 is configured to be moveable between two general configurations: a scooping configuration and a closed configuration. Within each of the scooping configuration and closed configuration there are various sub-configurations, as will be explained. Each sub-configuration is named with a prefix before “scooping” or “closed”, thereby indicating that the sub-configuration belongs to either of the general configurations (scooping or closed).

[0205] The fishing tool 1 comprises an up-hole end 1A and a down-hole end 1B. It will be understood that when performing a fishing operation in a wellbore, the up-hole end 1A is connected to equipment configured to deliver and control the fishing tool 1 in the wellbore.

[0206] In some examples the fishing tool 1 may be run on a wireline assembly or on coiled tubing. The wireline assembly may comprise a wireline tractor to advance the fishing tool 1 in a deviated or horizontal wellbore. It will be understood by a person skilled in the art that there is a plurality of possible commercially available tools that can be connected to fishing tools. It will be apparent to a person skilled in the art that the actual connections and interfaces at the up-hole end 1A of the tool 1 used with specific delivery equipment, for example coiled tubing or wireline equipment, may vary in alternative examples from what is shown in the presently described example.

[0207] Figure 1b shows a cross-sectional view through the fishing tool 1 of Figure 1a. It will be understood through reference to later Figures that the aforementioned outer 100 and inner 200 cylindrical shell segments each comprise a complete cylindrical hollow shaft section towards the up-hole end 1A. That is to say, the outer 100 and inner 200 cylindrical shell segments are segments of cylindrical shells only at a portion of their longitudinal extent, i.e. they are not necessarily cylindrical shell segments across their entire length and instead may be complete cylindrical shells at portions across their longitudinal extent. It will be understood that the outer 100 and inner 200 cylindrical shell segments are arranged relative to each other such that the non-complete cylindrical sections are at the same point along the longitudinal axis of the tool 1.

[0208] The provision of a hollow entirely cylindrical section at the up-hole portions of the inner cylindrical shell segments 200 provides a complete circular cross-section for the tools used to run and control the fishing tool 1 to grip onto and perform manipulation of the inner cylindrical shell segment 200, i.e. rotation thereof. Furthermore, the hollow entirely cylindrical section provides strength and stability to the tool 1.

[0209] Still referring to Figure 1b, the tool 1 further comprises a counter hold sleeve 300. The outer 100 and inner 200 cylindrical shell segments extend longitudinally within the counter hold sleeve 300. The counter hold sleeve 300 provides a housing for the outer 100 and inner 200 cylindrical shell segments. The inner cylindrical shell segment 200 extends and protrudes from the counter hold sleeve 300 at both the up-hole end 1A and the down-hole end 1 B, while the outer cylindrical shell segment 100 extends and protrudes from the down-hole end 1 B of the counter hold sleeve 300, as can be seen in Figure 1b.

[0210] The counter hold sleeve 300 comprises a plurality of counter hold splines 310 at the up-hole end 1A. The plurality of counter hold splines 310 are configured such that a correspondingly splined running tool can be used to rotationally lock the counter hold sleeve 300, i.e. stop the counter hold sleeve 300 from rotating. Providing a non-rotating counter hold sleeve 300 provides that the outer 200 and inner 100 cylindrical shell segments can be frictionally engaged against the counter hold sleeve 300, thereby stopping rotational movement of the outer 200 and inner 100 cylindrical shell segments unless a sufficient rotational force is applied to overcome the frictional engagement, as will be explained later.

[0211] The counter hold sleeve 300 comprises a fishing neck 320 configured such that the fishing tool 1 can be easily fished from the wellbore should it become lost. The fishing neck 320 may also be used as a shoulder for attaching to the running tools latch mechanism (not shown).

[0212] As explained previously, the inner cylindrical shell segment 200 protrudes from the counter hold sleeve 300 at the up-hole end 1 A, wherein the inner cylindrical shell segment 200 comprises a plurality of inner shell segment splines 210. The plurality of inner shell segment splines 210 are configured such that a correspondingly splined tool can be used to rotate the inner cylindrical shell segment 200, as will be explained later.

[0213] Still referring to Figure 1b it can be seen that the fishing tool 1 further comprises a manipulator 400 arranged in threaded connection with a confirmation piston 500. The manipulator 400, here in the form of a partially hollow shaft, comprises a plurality of manipulator splines 410 configured such that a correspondingly splined tool can be used to rotate the manipulator 400. The confirmation piston 500 comprises a threaded portion 510, visible in Figure 1f showing the cross-sectional view through cross-section C-C in Figure 1b. The threaded portion 510 engages corresponding manipulator threads 420.

[0214] Still referring to Figure 1f it can be seen that the outer cylindrical shell segment 100 comprises inward facing first 101 and second 102 outer shell splines arranged to mate in use with outward facing first 201 and second 202 inner shell splines on the inner cylindrical shell segment 200. In the presently described example, the first 101 and second 102 outer splines are arranged 180 degrees apart around the outer cylindrical shell segment 100. Similarly, the first 201 and second 202 inner splines are arranged 180 degrees apart around the inner cylindrical shell segment 200. It will be understood that other angles of separation may be provided in alternative examples not described herein in the interest of brevity.

[0215] It will be understood that the above-described splines allow the outer cylindrical shell segment 100 to be rotated by rotation of the inner cylindrical shell segment 200 with the inner shell splines 201 , 202 engaging the outer shell splines 101 , 102.

[0216] Referring now to Figure 1 h, in the cross-section view through cross-section G-G in Figure 1b, it can be seen that the confirmation piston 500 comprises first 520 and second 521 longitudinal slots for receiving corresponding first 220 and second 221 longitudinal splines provided on the inner cylindrical shell segment 200. The mating of the first 220 and second 221 splines in the first 520 and second 521 slots stops rotation of the piston 500 when the manipulator 400 is rotated, i.e. the longitudinal splines 220, 221 force the piston to advance longitudinally towards the up-hole 1A or down-hole 1B end of the tool 1.

[0217] Referring again to Figure 1b, the tool 1 further comprises first 600 and second 700 friction couplings. The first friction coupling 600 is provided between the counter hold sleeve 300 and the inner cylindrical shell segment 200. The first friction coupling 600 applies a frictional force between the counter hold sleeve 300 and the inner cylindrical shell segment 200. Applying a frictional force ensures that the inner cylindrical shell segment 200 does not rotate of its own accord, or is not rotated undesirably, for example by other components in the wellbore. Since the frictional force applied by the first friction coupling 600 is known (as it is predetermined), it is known what force is required to rotate the inner cylindrical shell segment 200 to overcome the force of the first friction coupling 600. Said another way, to rotate the inner cylindrical shell 200 relative to the counter hold sleeve 300, a rotational force greater than the frictional force of the first friction coupling 600 is applied.

[0218] The second friction coupling 700 is provided between the counter hold sleeve 300 and the outer cylindrical shell segment 100. The second friction coupling 700 applies a frictional force between the counter hold sleeve 300 and the outer cylindrical shell segment 100. Applying a frictional force ensures that the outer cylindrical shell segment 100 does not rotate of its own accord, or is not rotated undesirably, for example by other components in the wellbore. To rotate the outer cylindrical shell 100 relative to the counter hold sleeve 300, a rotational force greater than the frictional force is applied.

[0219] In the presently described example, the second friction coupling 700 provides a force of around 50% of the first friction coupling. It will be understood that in alternative examples the force of the second friction coupling 700 relative to the first friction coupling 600 may be different from in the presently described example. In the presently described example, the second friction coupling 700 is provided with a force of 50% smaller than the first friction coupling 600 such that, as will become apparent later, the operator, i.e. human and / or computer, can monitor the force required to rotate the inner cylindrical shell segment 200. When only the inner cylindrical shell segment 200 is engaged and rotating, a rotational force greater than the force applied by the first friction coupling 600 is required. When the inner cylindrical shell segment 200 is engaged with the outer cylindrical shell segment 100 such that both the inner cylindrical shell segment 200 and outer cylindrical shell segment 100 are rotating then a rotational force greater than the force applied by the first friction coupling 600 and the second friction coupling 700 is required, i.e. 150% of the force applied by the first friction coupling 600 in the presently described example. This provides feedback to the operator, human and / or computer, regarding whether only the inner cylindrical shell segment 200 is being rotated (100% force required) or both the inner cylindrical shell segment 200 and the outer cylindrical shell segment 100 are being rotated (150% force required).

[0220] It will be understood that in alternative examples other frictional force values may be provided.

[0221] As can be seen in the cross-sectional view through cross-section line E-E in Figure 1c and the cross-sectional view through cross-section line F-F in Figure 1 d, the first friction coupling 600 is provided as a disc friction clutch as shown. In the interest of brevity and clarity, the operation of a disc friction clutch is not explained in full, as it will be known to a person skilled in the art.

[0222] Although not shown in cross-sectional views, the second friction coupling 700 is provided as a disc friction clutch.

[0223] In alternative examples not shown herein, alternative friction couplings may be used.

[0224] Referring again to Figure 1 b, the tool 1 further comprises a ratchet device 800 moveable between a locked position and an unlocked position. A cross-sectional view through cross-section line D-D is shown in Figure 1e with the ratchet device 800 in the locked position. The ratchet device 800 comprises a spring 810 arranged to bias a pawl 820. The pawl 820 has a wedge-shaped profile 821 such that it can engage a correspondingly shaped groove 103 and arrest movement in one direction and allow movement in the opposite direction (when the ratchet device 800 is in the locked position). In the unlocked position, the pawl 820 is pushed against the bias of the spring 810 and the spring 810 is compressed. The wedge-shaped profile 821 is moved out of engagement with the correspondingly shaped groove 103, such that the outer cylindrical shell segment 100 is free to rotate in both directions (i.e. clockwise and counterclockwise).

[0225] Referring again to the locked position shown in figure 1e, it can be seen that the outer cylindrical shell segment 100 can be rotated clockwise (looking down the longitudinal axis of the tool 1 from the up-hold end 1A of the tool 1) as the rotation of the outer cylindrical shell segment 100 clockwise will push the pawl 820 inwards against the bias of the spring 810, thereby moving the ratchet device 800 from the locked position to the unlocked position. On the other hand, from the locked position shown in Figure 1e the outer cylindrical shell segment 100 cannot be rotated counter-clockwise, since the wedge-shaped profile 821 arrests the rotational movement of the outer cylindrical shell segment 100.

[0226] Referring again to the side view shown in Figure 1a, it can be seen that the tool 1 further comprises a catching arrangement 900 provided at the down-hole end 1 B of the tool 1 . The catching arrangement 900 is, in the presently described example, a separate component from the outer 100 and inner 200 cylindrical shell segments. However, in alternative examples, the catching arrangement 900 may be integrally formed with the outer 100 and / or inner 200 cylindrical shell segment. In the presently described example, the catching arrangement 900 is secured by bolts (not visible in Figure 1a, visible in Figure 2b) to the outer cylindrical shell segment 100. The catching arrangement 900 is arranged to catch a lost object (i.e. the object to be recovered in the fishing operation) as the lost object passes from the down-hole end 1 B of the tool towards the up-hole end 1A. The catching arrangement 900 is provided with a plurality of radially outwardly biased fingers 901 attached near the down-hole end 1 B of the tool 1.

[0227] For completeness, an end view from the up-hole end 1A of the tool 1 is shown in Figure 1g, with the section line B-B marked, this being the section view shown in Figure 1 b. Operation of the first fishing tool 1 to recover a lost object in a wellbore is now described with reference to Figures 1a to 6h, wherein Figures 1a to 1i show the tool 1 in a closed run-in-hole configuration, Figures 2a to 2h show the tool 1 in a high-side scooping configuration, Figures 3a to 3h show the tool 1 in a low-side scooping configuration, Figures 4a to 4h show the tool 1 in the caught closed configuration, Figures 5a to 5h show the tool 1 in the locked closed configuration, Figures 6a to 6h show the tool in the confirmation closed configuration.

[0228] As can be best seen in the perspective view in Figure 1i (without the wellbore shown) and in the cross-sectional view of the tool in Figure 7a (with the wellbore 3 shown), the tool 1 is run into the wellbore 3, to perform a fishing operation, in the closed run-in-hole configuration.

[0229] In the closed run-in-hole configuration, the outer 100 and inner 200 cylindrical shell segments form a closed chamber 1200A (not visible in Figure 1 i, visible in Figures 1b and 7a) for trapping the object to be recovered therein in use. In this connection, the outer cylindrical shell segment 100 comprises an outer shell segment top face 100A which is the presently described example helps to form the closed chamber 1200A at the down-hole end of the closed chamber 1200A.

[0230] In the closed run-in-hole configuration shown, the first friction coupling 600 and second friction coupling 700 are each arresting rotational movement of the inner 200 and outer 100 cylindrical shell segments relative to the counter hold sleeve 300, such that the inner 200 and outer 100 cylindrical shell segments do not rotate open while running in hole.

[0231] Before the tool 1 is run in hole, the inner cylindrical shell segment 200 is rotated counter-clockwise until the pawl 820 of the ratchet device 800 engages with the correspondingly shaped groove 103, at which point further counter-clockwise rotation of the inner 100, and therewith the outer 200, cylindrical shell segments is not possible.

[0232] The ratchet device 800 is in the locked position, that is to say, the wedge-shaped profile 821 of the pawl 820 of the ratchet device 800 is engaged within a correspondingly shaped groove 103 in the outer cylindrical shell segment 100 (shown in the detailed view in Figure 1 e), thereby arresting rotational counter-clockwise movement (when viewed down the longitudinal length of the tool 1 from the up-hole end 1 A) of the outer cylindrical shell segment 100 relative to the counter hold sleeve 300. This provides a reference point for the operator before and during advancement of the tool 1 in the wellbore. Further, counter-clockwise rotation to the position wherein the ratchet device 800 is in the locked position, the outward facing first inner shell splines 201 is engaged with the inward facing first outer shell spline 101 and the second outer shell spline 102 is engaged with the outward facing second inner shell spline 202, allows the operator to confirm that this position has been reached by receiving large mechanical resistance when the operator attempts to continue rotating counter-clockwise.

[0233] It will be understood that in the presently described example, the tool 1 is arranged such that counter-clockwise rotation leads to locking of the ratchet device 800, however the tool 1 may be arranged in other examples with the ratchet device 800 provided in the opposite direction, such that clockwise rotation leads to locking of the ratchet device 800.

[0234] The tool 1 can be advanced through the wellbore 3 by, as non-limiting examples, wireline or coiled tubing. In the interest of clarity, no delivery means is shown in the Figures currently referred to, however it will be understood by a person skilled in the art that the tool 1 is to be attached to a delivery means.

[0235] Regardless of the delivery means, the tool 1 is advanced in the closed run-in- hole configuration until the tool 1 is in the vicinity of the object to be collected. The closed run-in-hole configuration may provide a complete body to the tool 1 such that the tool 1 does not become undesirably stuck on objects in the wellbore while advancing the wellbore. Furthermore, the complete or closed body stops debris or other foreign objects from undesirably entering the tool 1 while it advances the wellbore 3. The tool 1 may be brought within, for example, 1 meter to 10 meters of the object 2 to be collected.

[0236] When the tool 1 is close to the object 2 to be collected, or as the tool 1 approaches the object 2, the tool 1 is moved to a high-side scooping configuration (Figures 2a to 2h). In the high-side scooping configuration the outer cylindrical shell segment 100 and inner cylindrical shell segment 200 are overlapping and form an open chamber 1200B for receiving the object 2 into.

[0237] Two steps are performed to move the tool 1 from the closed run-in-hole configuration (Figures 1a to 1 i) to the high-side scooping configuration (Figures 2a to 2h). In a first step, the inner cylindrical shell segment 200 is rotated clockwise relative to the outer cylindrical shell segment 100 such that the closed chamber 1200A becomes an open chamber 1200B for receiving the object 2. Rotation of the inner cylindrical shell segment 200 is performed by applying a sufficiently high rotational force to the inner cylindrical shell segment 200 to overcome the force applied by the first friction coupling 600. Since the inner cylindrical shell segment 200 is rotated clockwise, the outward facing first inner shell spline 201 is disengaged from the inward facing first outer shell spline 101 and the second outer shell spline 102 is disengaged from the outward facing second inner shell spline 202, allowing the inner cylindrical shell segment 200 to rotate without also rotating the outer cylindrical shell segment 100.

[0238] For the avoidance of doubt, the second friction coupling 700 continues to apply a frictional force, such that the outer cylindrical shell segment 100 does not move while the inner cylindrical shell segment 200 is rotating. In this connection, the inner cylindrical shell segment 200 is rotated 180 degrees clockwise such that the first inner shell spline 201 moves from being adjacent the first outer shell spline 101 (Figure 1f) to being adjacent the second outer shell spline 102 (Figure 2f). At the same time, second inner shell spline 202 moves from being adjacent the second outer shell spline 102 (Figure 1 f) to being adjacent the first outer shell spline 101 (Figure 2f). In a second step, starting at the point where the first inner shell spline 201 and second outer shell spline 102 meet and the second inner shell spline 202 and the first outer shell spline 101 meet, continued rotation of the inner cylindrical shell segment 200, now with a force greater than the combined force of the first friction coupling 600 and second friction coupling 700, causes the outer cylindrical shell segment 100 to rotate together and thus trail along with the inner cylindrical shell segment 200, due to the aforementioned engaged splines 101 / 102 and 102 / 201. Since the rotation is clockwise and therefore is not rotationally restricted by the ratchet device 800, the outer cylindrical shell segment 100 is free to rotate. That is to say, the outer cylindrical shell segment 100 pushes on the wedge-shaped profile 821 (Figure 1 e) which is forced inward against the bias of the spring 810 (as shown in Figure 2e). The tool 1 is now in the high-side scooping configuration, referred to as such because the tool 1 sits on the high-side of the wellbore 3 (Figure 7b). The first 600 and second 700 friction couplings apply, as always, their respective frictional forces to ensure that the inner 200 and outer 100 cylindrical shell segments do not rotate without being intentionally rotated by the operator applying a sufficient rotational force to overcome the respective frictional forces provided. The tool 1 can then be advanced within the wellbore 1 and the outer 100 and inner 200 cylindrical shell segments will not rotate while the tool 1 is advanced.

[0239] As shown in Figures 7b and 7c, the tool 1 approaches and passes over the object 2. That is to say, the aforementioned catching arrangement 900 advances over the object 2 and catches the object 2 within the tool 1 by means of the radially outwardly biased fingers 901 passing over the object 2 and allowing the object 2 to pass the radially outwardly biased fingers 901 in one direction only. When the object 2 has passed the radially outwardly biased fingers 901 , the tool 1 is located over the object, i.e. the outer 100 and inner 200 cylindrical shell segments are located over the object 2, as shown in Figures 2a to 2h and in Figure 7c.

[0240] The catching arrangement 900 ensures that the object 2 is maintained under the tool 1 for the subsequent steps to perform retrieval. The catching arrangement 900 may assist in overcoming the aforementioned problem of “kicking” the object further into the wellbore 3 when approaching the object 2 with the tool 1. As previously mentioned, this problem is particularly prevalent when utilising coil tubing tools due to the “release” or “snap-back” previously discussed. The provision of a catching arrangement 900 is optional, as it will be understood that the tool 1 may function to retrieve a lost object 2 without necessarily requiring a catching arrangement 900 at the down-hole end 1B.

[0241] Locating the object 2 under the tool 1 with the tool 1 in the position shown in Figures 2a to 2h and Figure 7c allows the object to be scooped and recovered using the tool 1 as will now be described.

[0242] To scoop the object 2 into the open chamber 1200B, the outer 100 and inner 200 cylindrical shell segments are rotated 180 degrees from the high-side scooping configuration shown in Figures 2a to 2h and Figure 7c to the low-side scooping configuration shown in Figures 3a to 3h and Figure 7f. Figures 7d and 7e show cross- sectional and end-views, respectively, of the tool during transition from the high-side scooping configuration to the low-side scooping configuration.

[0243] Firstly, starting at the high-side scooping configuration shown in Figures 2a to 2h and Figure 7c, and specifically referring now to Figure 2f, the inner cylindrical shell segment 200 is rotated clockwise with sufficient rotational force to overcome the first friction coupling 600 and second friction coupling 700, thereby also rotating the outer cylindrical shell segment 100 by the first inner shell spline 201 engaging the second outer shell spline 102 and the second inner shell spline 202 engaging the first outer shell spline 101. In this way, the outer 100 and inner 200 cylindrical shell segments are rotated 180 degrees clockwise thereby moving the tool 1 from the high-side scooping configuration shown in Figure 7c to the low-side scooping configuration shown in Figure 7f. As can be most clearly seen in Figure 7d and the cross-sectional view in Figure 7e through the cross-section line marked in Figure 7d, the outer 100 and inner 200 cylindrical shell segments scoop the object 2 by firstly pushing the object up the inner wall of the wellbore 3 and then allowing the object 2 to fall into the open chamber 1200B. Since the rotation of the outer cylindrical shell segment 100 is clockwise, the ratchet device 800 does not engage and the outer cylindrical shell segment 100 can therefore be rotated clockwise indefinitely, if required. If the scooping of the object 2 is not successful, it may be desirable to make several attempts to scoop the object 2, therefore it is highly advantageous that the ratchet device 800 allows for unlimited rotation in one direction, i.e. clockwise in the presently described example.

[0244] Provided in the presently described example, although not essential, the outer 100 and inner 200 cylindrical shell segments are provided with first 100B and second 200B chamfers, respectively. The first 100B and second 200B chamfers help to direct the object 2 into the open chamber 1200B as the outer 100 and inner 200 cylindrical shell segments rotate as previously described.

[0245] Now that the object 2 is located in the open chamber 1200B it is desired to close the open chamber 1200B such that the object 2 is securely retained within the chamber and can be brought to the surface. That is to say, the tool 1 is moved from the low-side scooping configuration shown in Figures 3a to 3h and Figure 7f to the caught closed configuration shown in Figures 4a to 4h and Figure 7g.

[0246] In this connection, starting from the low-side scooping configuration shown in Figures 3a to 3h and Figure 7f, and specifically referring to Figure 3f, the inner cylindrical shell segment 200 is rotated counter-clockwise around 180 degrees until the first inner shell spline 201 abuts the first outer shell spline 101 and the second inner shell spline 202 abuts the second outer shell spline 102 (shown in Figure 4f), thereby closing the open chamber 1200B (as shown in Figure 4b and 7g) with the object 2 caught inside. It will be understood that the rotational force required to rotate only the inner cylindrical shell segment 200 must overcome only the frictional force of the first friction coupling 600. It can be seen in the cross-sectional view through the ratchet device 800 shown in Figure 4e that in the caught closed configuration shown the outer cylindrical shell segment 100 is not locked by the ratchet device 800, as is performed in the next step now described.

[0247] Starting from the caught closed configuration shown in Figures 4a to 4h and Figure 7g, and specifically referring to Figure 4f, the inner cylindrical shell segment 200 is further rotated counter-clockwise. Since the first inner shell spline 101 and second inner shell spline 102 are abutting the first outer shell spline 201 and second outer shell spline 202, respectively, the inner cylindrical shell segment 200 is rotated counterclockwise thereby also rotating the outer cylindrical shell segment 100 counter- clockwise. It will be understood that to rotate the inner 200 and outer 100 shell segments together, the rotational force applied must again overcome the combined frictional forces provided by the first friction coupling 600 and the second friction coupling 700.

[0248] Since both shell segments 100, 200 rotate together, the closed chamber 1200A remains closed such that the object 2 does not escape. The shell segments 100, 200 are rotated around 270 degrees counter-clockwise (as shown in Figure 5f) until the ratchet device 800 moves to the locked position as shown in Figure 5e. With the ratchet device 800 in the locked position, the outward facing first inner shell splines 201 engaged with the inward facing first outer shell spline 101 and the second outer shell spline 102 is engaged with the outward facing second inner shell spline 202, the operator can confirm that this position has been reached by receiving a large mechanical resistance when the operator attempts to continue rotating counterclockwise.

[0249] In the locked closed configuration shown in Figures 5a to 5h and Figure 7h, the outer 100 and inner 200 shells are rotationally locked and the object 2 is securely held within the closed chamber 1200A.

[0250] To confirm that the object 2 has been successfully caught within the closed chamber 1200A, an optional confirmation step is provided, as now described. The confirmation step moves the tool 1 from the locked closed configuration shown in Figure 5a to 5h and Figure 7h to a confirmation closed configuration shown in Figures 6a to 6h and Figure 7i. Starting from the locked closed configuration, the first 600 and second 700 friction couplings are still applying their respective frictional forces, thereby preventing relative movement of both the outer 100 and inner 200 cylindrical shell segments relative to the counter hold sleeve 300 in the absence of an applied rotational force on the inner cylindrical shell segment 200 by the operator. The ratchet device 800 is maintained in the locked position as shown in Figure 6e. Referring to the side view shown in Figure 6a, the cross-sectional view shown in Figure 6b, the end view shown in Figure 6g and the cross-sectional view shown in Figure 7i, it can be seen that, as previously discussed, the tool 1 comprises a manipulator 400 comprising manipulator splines 410 and arranged in threaded connection with a confirmation piston 500. To check that the object 2 has been caught in the closed chamber 1200A, the manipulator 400 is rotated (i.e. either clockwise or counter-clockwise depending on the arrangement of the threaded portion), thereby advancing the piston 500 towards the down-hole end 1 B of the tool 1. Continued rotation of the manipulator 400 causes the piston 500 to abut the object 2 within the closed chamber 1200A. The distance of travel of the piston 500 can be calculated by utilising the number of rotations of the manipulator 400 and the thread arrangement provided between the manipulator 400 and the piston 500. In this connection, the operator will be able to tell if the piston 500 has reached the down-hole end of the closed chamber or if the piston 500 has stopped advancing when reaching the trapped object 2, as shown in Figure 7i.

[0251] In alternative examples not described herein, the distance the piston 500 has advanced in the closed chamber 1200A may be measured in alternative ways, such as but not limited to, one or more of: a pressure sensor; a light sensor; a laser sensor; a force sensor; a camera. Furthermore, in alternative examples, confirmation that the object 2 has been trapped within the closed chamber may be provided by alternative means.

[0252] In some alternative examples not described herein, the piston 500 may be entirely replaced by another determination means for determining if the object is caught within the chamber, such as but not limited to, for example a camera or other sensor.

[0253] If, in the confirmation closed configuration, the piston 500 can advance to the end of the closed chamber 1200A, the operator may wish to re-attempt to catch the lost object 2. In such cases, the piston 500 can be retracted by rotating the manipulator 400 in the opposite direction from the rotation causing the piston 500 to advance towards the down-hole end 1 B. When the piston 500 is fully retracted, the tool 1 will be in the closed run-in-hole configuration shown in Figures 1a to 1i and Figure 7a.

[0254] When the fishing operation is to be terminated, either with successful catching of the object 2 or not, the tool 1 can be removed from the wellbore 3. The tool 1 can be removed in the run-in-hole configuration shown in Figure 7a, for example if the fishing operation is terminated before it is attempted to catch the object 2 for example if the target depth cannot be reached. The tool 1 can be removed from the wellbore 3 in the confirmation closed configuration shown in Figure 7i, either with an object 2 located in the closed chamber 1200A or without an object 2 located in the closed chamber 1200A. The tool 1 can also be removed from the wellbore 3 in the locked closed configuration shown in Figure 7h, if the tool 1 does not comprise a means for determining if the object 2 has been caught, or if such a test is not desired. It will also be understood that the tool 1 may be removed from the wellbore 3 in various other configurations, however it is preferrable that the tool 1 is in a closed configuration, rather than a scooping configuration, when running into and out of the wellbore 3. Figures 8a and 8b shows side and perspective views, respectively, of the fishing tool of Figure 1a connected to an optional manoeuvring and control tool 4. It will be understood by a person skilled in the art that there are myriad possible manoeuvring and control tools that may be connected to the fishing tool 1 to run the tool 1 into the wellbore and operate the tool 1. By operation of the tool 1 it is intended to mean that the counter hold sleeve 300 can be held stationary by engagement of the aforementioned counter hold splines 310, the inner shell segment 200 can be rotated by engagement and rotation of the inner shell segment splines 210, and the manipulator 400 can be rotated by engagement and rotation of the manipulator splines 410. It will be understood that in some examples the manoeuvring and control tool 4 may be provided with individual means for engaging and operating the various aforementioned components of the tool 1. That is to say, in some examples, the manoeuvring and control tool 4 may be provided with multiple individually operable motors to individually rotate the individually rotatable components discussed. On the other hand, in some examples, the manoeuvring and control tool 4 may comprise a single motor which is moveable between engagement with the inner cylindrical shell segment 200 to provide rotation thereof and engagement with the manipulator 400 to provide rotation thereof, for example.

[0255] As well as engagement and, where required, rotation of the aforementioned components of the tool 1, the manoeuvring and control tool 4 is configured to securely engage the tool 1 in the longitudinal direction such that the tool 1 can be advanced into a wellbore and removed from the wellbore. It will be understood that attachment of the tool 1 to the manoeuvring and control tool 4 may be by any known means. For example, the tool 1 may be connected to the manoeuvring and control tool 4 by a threaded connection.

[0256] The manoeuvring and control tool 4 shown in Figures 8a and 8b is described in further detail in patent document WO2015047102A1.

[0257] Figure 9a shows a second fishing tool T according to the invention. The fishing tool T is for performing a fishing operation to recover an object (not shown in Figure 9a) in a subterranean well (not shown in Figure 9a). The fishing tool T comprises a cylindrical shell segment 100’ arranged around the central axis of the tool T. The cylindrical shell segment 100’ is a substantially hemispherical shell segment.

[0258] The fishing tool T comprises an up-hole end 1A’ and a down-hole end 1B’. It will be understood that when performing a fishing operation in a wellbore, the up-hole end 1A’ is connected to equipment configured to deliver and control the fishing tool T in the wellbore.

[0259] In some examples the fishing tool T may be run on a wireline assembly or on coiled tubing. The wireline assembly may comprise a wireline tractor to advance the fishing tool T in a deviated or horizontal wellbore. It will be understood by a person skilled in the art that there is a plurality of possible commercially available tools that can be connected to fishing tools. It will be apparent to a person skilled in the art that the actual connections and interfaces at the up-hole end 1A’ of the tool T used with specific delivery equipment, for example coiled tubing or wireline equipment, may vary in alternative examples from what is shown in the presently described example.

[0260] Figure 9b shows a cross-sectional view through the fishing tool T of Figure 9a. It will be understood through reference to later Figures that the aforementioned cylindrical shell segment 100’ comprises a complete cylindrical hollow shaft section towards the uphole end 1A’. That is to say, the cylindrical shell segment 100’ is a segment of a cylindrical shell only at a portion of its longitudinal extent, i.e. it need not necessarily be a cylindrical shell segment across its entire length and instead may be a complete cylindrical shell at portions across its longitudinal extent.

[0261] The provision of a hollow entirely cylindrical section at the up-hole 1 A’ portion of the cylindrical shell segment 100’ provides a complete circular cross-section for the tools used to run and control the fishing tool T to grip onto and perform manipulation of the cylindrical shell segment 100’, i.e. rotation thereof. Furthermore, the hollow entirely cylindrical section provides strength and stability to the tool T.

[0262] Still referring to Figure 9b, the tool T further comprises a counter hold sleeve 300’. The cylindrical shell segment 100’ extends longitudinally within the counter hold sleeve 300’. The counter hold sleeve 300’ provides a housing for the cylindrical shell segment 100’. The cylindrical shell segment 100’ extends and protrudes from the counter hold sleeve 300’ at both the up-hole end 1A’ and the down-hole end 1 B’, as can be seen in Figure 9b.

[0263] The counter hold sleeve 300’ comprises a plurality of counter hold splines 310’ at the up-hole end 1A’. The plurality of counter hold splines 310’ are configured such that a correspondingly splined running tool can be used to rotationally lock the counter hold sleeve 300’, i.e. stop the counter hold sleeve 300” from rotating. Providing a non-rotating counter hold sleeve 300’ provides that the cylindrical shell segment 100’ can be frictionally engaged against the counter hold sleeve 300’, thereby stopping rotational movement of the cylindrical shell segment 100’ unless a sufficient rotational force is applied to overcome the frictional engagement, as will be explained later.

[0264] The counter hold sleeve 300’ comprises a fishing neck 320’ configured such that the fishing tool T can be easily fished from the wellbore should it become lost. The fishing neck 320’ may also be used as a shoulder for attaching to the running tools latch mechanism (not shown).

[0265] As explained previously, cylindrical shell segment 100’ protrudes from the counter hold sleeve 300’ at the up-hole end 1A’, wherein the cylindrical shell segment 100’ comprises a plurality of shell segment splines 110’. The plurality of shell segment splines 110’ are configured such that a correspondingly splined tool can be used to rotate the cylindrical shell segment 100’, as will be explained later.

[0266] Still referring to Figure 9b it can be seen that the fishing tool T further comprises a manipulator 400’ arranged in threaded connection with a confirmation piston 500’. The confirmation piston 500’ comprises an object engagement portion 50T and a cover portion 502’ (visible in Figure 9a). The manipulator 400’ comprises a plurality of manipulator splines 410’ configured such that a correspondingly splined tool can be used to rotate the manipulator 400’. The confirmation piston 500’ comprises a threaded portion 510’, visible in Figure 9f showing the cross-sectional view through cross-section C-C in Figure 9b. The threaded portion 510’ engages corresponding manipulator threads 420’.

[0267] In some alternative examples not described herein, the confirmation piston 500’ may be entirely replaced by another determination means for determining if the object is caught within the chamber, such as but not limited to, for example a camera or other sensor.

[0268] Referring now to Figure 9h, in the cross-section view through cross-section G-G in Figure 9b, it can be seen that the confirmation piston 500’ comprises first 520’ and second 52T longitudinal slots for receiving corresponding first 220’ and second 22T longitudinal splines provided on the cylindrical shell segment 100’. The mating of the first 220’ and second 22T splines in the first 520’ and second 52T slots stop rotation of the piston 500’ when the manipulator 400’ is rotated, i.e. the longitudinal splines 220’, 22T force the piston 500’ to advance longitudinally towards the up-hole 1A’ or down-hole 1B’ end of the tool T. Referring again to Figure 9b, the tool T further comprises a friction coupling 600’ and a ratchet device 800’. The ratchet device 800’ is moveable between a locked position and an unlocked position. A cross-sectional view through cross-section line D-D is shown in Figure 9e with the ratchet device 800’ in the locked position. The ratchet device 800’ comprises a spring 810’ arranged to bias a pawl 820’. The pawl 820’ has a wedge-shaped profile 82 T such that it can engage a correspondingly shaped groove 103’ and arrest movement in one direction and allow movement in the opposite direction (when the ratchet device 800’ is in the locked position). In the unlocked position, the pawl 820’ is pushed against the bias of the spring 810’ and the spring 810’ is compressed. The wedge-shaped profile 82T is moved out of engagement with the wedge-shaped profile 82T, such that the cylindrical shell segment 100’ is free to rotate in both directions (i.e. clockwise and counter-clockwise). Referring again to the locked position shown in figure 9e, it can be seen that the outer cylindrical shell segment 100’ can be rotated clockwise (looking down the longitudinal axis of the tool T from the uphold end 1A’ of the tool T) as the rotation of the cylindrical shell segment 100’ clockwise will push the pawl 820’ inwards against the bias of the spring 810’, thereby moving the ratchet device 800’ from the locked position to the unlocked position. On the other hand, from the locked position shown in Figure 9e the outer cylindrical shell segment 100’ cannot be rotated counter-clockwise, since the wedge-shaped profile 82T arrests the rotational movement of the cylindrical shell segment 100’.

[0269] For completeness, an end view from the up-hole end 1A’ of the tool T is shown in Figure 9g, with the section line B-B marked, this being the section view shown in Figure 9b.

[0270] Operation of the second fishing tool T to recover a lost object in a wellbore is now described with reference to Figures 9a to 12h, wherein Figures 9a to 9i show the tool T in a run-in-hole configuration, Figures 10a to 10h show the tool T in a high-side configuration, Figures 11a to 11 h show the tool T in a low-side configuration and Figures 12a to 12h show the tool T in the confirmation configuration.

[0271] As can be best seen in the perspective view in Figure 9i (without the wellbore shown) and in the cross-sectional view of the tool T in Figure 13a (with the wellbore 3’ shown), the tool T is run into the wellbore 3’, to perform a fishing operation, in the run-in- hole configuration.

[0272] In the run-in-hole configuration, the ratchet device 800’ is in the locked position, that is to say, the wedge-shaped profile 82T of the pawl 820’ of the ratchet device 800’ is engaged within a correspondingly shaped groove 103’ in the cylindrical shell segment 100’ (shown in the detailed view in Figure 9e), thereby arresting rotational counterclockwise movement (when viewed down the longitudinal length of the tool T from the up-hole end 1A’) of the cylindrical shell segment 100’ relative to the counter hold sleeve 300’.

[0273] Before the tool T is run in hole, the cylindrical shell segment 100’ is rotated counter-clockwise until the pawl 820’ of the ratchet device 800’ engages with the correspondingly shaped groove 103’, at which point further counter-clockwise rotation of the cylindrical shell segment 100’ is not possible. This provides a reference for the operator as the tool T is run in hole.

[0274] In the run-in-hole configuration shown, the friction coupling 600’ is stopping rotational movement of the cylindrical shell segment 100’ relative to the counter hold sleeve 300’, such that the cylindrical shell segment 100’ do not rotate while running in hole. That is to say, the cylindrical shell segment 100’ cannot rotate unless a sufficient rotational force is applied to overcome the frictional engagement provided by the friction coupling 600’.

[0275] The tool T can be advanced through the wellbore 3’ by, as non-limiting examples, wireline or coiled tubing. In the interest of clarity, no delivery means is shown in the Figures currently referred to, however it will be understood by a person skilled in the art that the tool T is to be attached to a delivery means.

[0276] Regardless of the delivery means, the tool T is advanced in the run-in-hole configuration until the tool T is in the vicinity of the object to be collected. The tool T may be brought within, for example, 1 meter to 10 meters of the object 2’ to be collected.

[0277] The tool T comprises an open chamber 1200’B which can be seen most clearly in Figures 9i and 11h.

[0278] When the tool T is close to the object 2’ to be collected, or as the tool T approaches the object 2’, the tool T is moved to a high-side configuration (Figures 10a to 10h) by rotation of the cylindrical shell segment 600’ clockwise. For the avoidance of doubt, in the presently described arrangement, from the run-in-hole configuration shown in Figures 9a-9i, it is not possible to rotate the cylindrical shell segment 600’ counterclockwise, since the ratchet device 800’ is in the locked position in the run-in-hole configuration.

[0279] The high-side configuration is referred to as such because the tool T sits on the high-side of the wellbore 3’ (Figure 10b). It will be understood the location in the wellbore where the object 2’ is to be recovered from, the wellbore is deviated or horizontal. In the presently described examples, a horizontal wellbore 3’ is provided. The tool T approaches and passes over the object 2’ until the tool T is located over the object 2’, i.e. the cylindrical shell segment 100’ is located over the object 2’, as shown in Figures 10a to 10h and in Figure 13c. It can be seen most clearly in Figure 10a that in this configuration the open chamber 1200’B which the object 2’ will subsequently be scooped into is located is directly above the object 2’.

[0280] Locating the object 2’ under the tool T with the tool T in the position shown in Figures 10a to 10h and Figure 13c allows the object 2’ to be scooped and recovered using the tool T as will now be described.

[0281] To scoop the object 2’ into the tool T, the cylindrical shell segment 100’ is rotated 180 degrees clockwise from the high-side configuration shown in Figures 10 to 10h and Figure 13c to the low-side configuration shown in Figures 11a to 11h, through the scooping position shown in Figure 13d. Figure 13e shows a cross-sectional view of the tool T during transition from the high-side configuration to the low-side configuration, i.e. during scooping of the object 2’ into the open chamber 1200’B.

[0282] Referring to Figure 10f, the cylindrical shell segment 100’ is rotated clockwise 180 degrees thereby moving the tool T from the high-side configuration shown in Figure 13c to the low-side configuration through the scooping position shown in Figures 13d and 13e. The rotational force applied must overcome the frictional force provided by the friction coupling 600’. The cylindrical shell segment 100’ scoops the object 2’ by firstly pushing the object 2’ up the inner wall of the wellbore 3’ and then allowing the object 2’ to fall into the open chamber 1200’B of the tool T. In the presently described example, although not essential, the cylindrical shell segment 100’ is provided with a chamfer 100B’ as can be seen in Figure 13e. The chamfer 100B’ helps to direct the object 2’ into the open chamber 1200’B of the tool T as the cylindrical shell segment 100’ rotates as previously described. Now that the object 2’ is located in the tool T it may be desired to confirm that the object 2’ has been successfully caught within the tool T. For this purpose, an optional confirmation step is provided, as now described.

[0283] The confirmation step moves the tool T from the low-side configuration, shown in Figures 11a to 11 h, to a confirmation configuration, shown in Figures 12a to 12h and 13f. The friction coupling 600’ prevents relative movement of the cylindrical shell segment 100’ relative to the counter hold sleeve 300’ during the movement to the confirmation configuration. Referring to the side view shown in Figure 12a, the cross- sectional view shown in Figure 12b, the end view shown in Figure 12g and the cross- sectional view shown in Figure 13f, it can be seen that, as previously discussed, the tool T comprises a manipulator 400’ comprising manipulator splines 410’ and arranged in threaded connection with a confirmation piston 500’. To check that the object 2’ has been caught in the tool T, the manipulator 400’ is rotated (i.e. either clockwise or counter-clockwise depending on the arrangement of the threaded portion), thereby advancing the piston 500’ towards the down-hole end 1B’ of the tool T. Continued rotation of the manipulator 400’ causes the object engagement portion 50T of the piston 500’ to abut the object 2’ within the tool T. As can be seen in Figure 12b, the cover portion 502’ is advanced such that the cover portion 502’ closes the chamber such that the object 2’ does not fall out from the chamber. In this regard, it will be understood that the shape and configuration of the cover portion 502’ may be registered with the shape and configuration of the down-hole portion 1 B’ of the cylindrical shell segment 100’ such that the cover portion 502’ closes the chamber in use.

[0284] The distance of travel of the piston 500’ can be calculated by utilising the number of rotations of the manipulator 400’ and the thread arrangement provided between the manipulator 400’ and the piston 500’. In this connection, the operator will be able to tell if the piston 500’ has reached the down-hole 1 B’ end of the tool T or if the piston 500’ has stopped advancing when reaching the trapped object 2’, as shown in Figure 13f.

[0285] In alternative examples not described herein, the distance the piston 500’ has advanced in the tool T may be measured in alternative ways, such as but not limited to, one or more of: a pressure sensor; a light sensor; a laser sensor; a force sensor; a camera. Furthermore, in alternative examples, confirmation that the object 2’ has been trapped within the tool T may be provided by alternative means.

[0286] It will also be understood that in some examples, not shown herein, the tool T may be provided with an alternative means for confirming that the object 2’ has been trapped whilst being provided with a cover portion 502’ arranged to be advanced on a piston 500’ to close the chamber. That is to say, the tool T may utilise, for example, a light sensor or camera to determine if the object 2’ has been scooped within the tool T and utilise a piston 500’ solely for the purpose of closing the chamber, without the piston 500’ comprising an object engagement portion 50T for confirming if the object 2’ has been scooped within the chamber.

[0287] In further alternative examples not shown herein, the tool T may be provided with a piston 500’ comprising an object engagement portion 50T but without a cover portion 502’. In such cases, the object engagement portion 50T may be advanced into contact with the object 2’ and held in contact with the object 2’ while the tool T is run out of hole, thereby ensuring that the object 2’ does not fall out of the tool T while the tool T is run out of hole.

[0288] Referring again to the presently described example, if the piston 500’ can advance to the end of its predetermined maximum travel distance, the operator may wish to re-attempt to catch the lost object 2’. In such cases, the piston 500’ can be retracted by rotating the manipulator 400’ in the opposite direction from the rotation causing the piston 500’ to advance towards the down-hole end 1 B’. When the piston 500’ is fully retracted, the tool T will be in the low-side configuration shown in Figures 11a to 11 h (without the object 2’ therein). The tool T can be rotated to the high-side configuration and another attempt to catch the object 2’ can be made.

[0289] When the fishing operation is to be terminated, either with successful catching of the object 2’ or not, the tool T can be removed from the wellbore 3’. The tool T can be removed in any of the aforementioned configurations. That is to say, the tool T can be removed from the wellbore 3’ in the run-in-hole configuration shown in Figure 9i, for example if the fishing operation is terminated before it is attempted to catch the object 2’ for example if the target depth cannot be reached. The tool T can be removed from the wellbore 3’ in the high-side configuration shown in Figure 10h, for example if the fishing operation is attempted but it terminated before the cylindrical shell segment 100’ is rotated to scoop the object 2’.

[0290] The tool T can be removed from the wellbore 3’ in the low-side configuration shown in Figure 11 h, for example if the fishing operation is terminated when the object 2’ is caught. In cases where no confirmation piston is provided, or an alternative confirmation means is utilised, the object 2’ may move within the tool T as the tool T is removed from the wellbore. That is to say, in Figure 11h the object 2’ is located substantially centrally in the cylindrical shell segment 100’. It will be understood that as the tool T is withdrawn from the horizonal or deviated wellbore, the object 2’ may move towards the down-hole end 1 B’ of the cylindrical shell segment 100’. If the object 2’ has not already moved towards the down-hole end 1 B’ during retraction from the horizontal or deviated wellbore section, the object 2’ may move towards the down-hole 1 B’ end when the tool T is moved through a vertical section of the wellbore, such as for example the final upper section of the wellbore closest to the surface. It will be appreciated that in some examples (not shown) the tool T may be provided with a pocket or recess to assist in ensuring that the object 2’ does not fall out from captivity within the tool T while the tool T is run out of the wellbore. Figures 14a and 14b shows side and perspective views, respectively, of the second fishing tool of Figure 9a connected to an optional manoeuvring and control tool 4’. It will be understood by a person skilled in the art that there are myriad possible manoeuvring and control tools that may be connected to the fishing tool T to run the tool T into the wellbore and operate the tool T. By operation of the tool T it is intended to mean that the counter hold sleeve 300’ can be held stationary by engagement of the aforementioned counter hold splines 310’, the cylindrical shell segment 100’ can be rotated by engagement and rotation of the cylindrical shell segment splines 110’, and the manipulator 400’ can be rotated by engagement and rotation of the manipulator splines 410’. It will be understood that in some examples the manoeuvring and control tool 4’ may be provided with individual means for engaging and operating the various aforementioned components of the tool T. That is to say, in some examples, the manoeuvring and control tool 4’ may be provided with multiple individually operable motors to individually rotate the individually rotatable components discussed. On the other hand, in some examples, the manoeuvring and control tool 4’ may comprise a single motor which is moveable between engagement with the cylindrical shell segment 100’ to provide rotation thereof and engagement with the manipulator 400’ to provide rotation thereof, for example.

[0291] As well as engagement and, where required, rotation of the aforementioned components of the tool T, the manoeuvring and control tool 4’ is configured to securely engage the tool T in the longitudinal direction such that the tool T can be advanced into a wellbore and removed from the wellbore. It will be understood that attachment of the tool T to the manoeuvring and control tool 4’ may be by any known means. For example, the tool T may be connected to the manoeuvring and control tool 4’ by a threaded connection.

[0292] The manoeuvring and control tool 4’ shown in Figures 14a and 14b is described in further detail in patent document WO2015047102A1.

[0293] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

Claims

CLAIMS1. A fishing tool (1) for performing a fishing operation to recover an object (2) in a subterranean well (3), comprising: an outer shell segment (100); an inner shell segment (200); wherein the tool (1) is configured to be moveable between: a scooping configuration wherein the outer shell segment (100) and the inner shell segment (200) are at least partially overlapping and form an open chamber (1200B) for receiving the object (2) into in use; and a closed configuration wherein the outer (100) and inner (200) shell segments form a closed chamber (1200A) for trapping the object (2) therein in use; wherein the tool (1) is configured to scoop the object (2) into the open chamber (1200B) in use by rotation of the outer (100) and / or inner (200) shell segments; and wherein the tool (1) is configured to move between the scooping configuration and the closed configuration by relative rotation of the outer (100) and inner (200) shell segments.

2. The fishing tool (1) according to claim 1 , wherein the outer shell segment (100) and the inner shell segment (200) share a central rotational axis.

3. The fishing tool (1) according to claim 1 or 2, wherein the outer shell segment (100) comprises a cylindrical shell segment and / or the inner shell segment (200) comprises a cylindrical shell segment.

4. The fishing tool (1) according to claim 1 or 2, wherein the outer shell segment (100) comprises a substantially hemicylindrical shell segment and / or the inner shell segment (200) comprises a substantially hemicylindrical shell segment.

5. The fishing tool (1) according to any preceding claim, wherein in the closed configuration the outer shell segment (100) and inner shell segment (200) can together form a radial wall around the object (2) in use.

6. The fishing tool (1) according to any preceding claim, wherein the outer shell segment (100) comprises an outer shell segment top face (100A) and the inner shellsegment (200) comprises an inner shell segment top face (200A), wherein in the closed configuration the outer shell segment top face (100A) and / or the inner shell segment top face (200A) at least partially form the closed chamber (1200A).

7. The fishing tool (1) according to any preceding claim, wherein the outer (100) and / or inner (200) shell segments comprises a biasing means configured to bias the object (2) towards the open chamber (1200B) when the object (2) is scooped by the outer (100) and / or inner (200) shell segment in use.

8. The fishing tool (1) according to any preceding claim, further comprising a counter hold sleeve (300) configured to house part of the outer (100) and part of the inner (200) shell segments.

9. The fishing tool (1) according to claim 8, wherein the counter hold sleeve (300) comprises a counter hold sleeve holding portion (310) configured to be held to prevent rotation of the counter hold sleeve (300) in use.

10. The fishing tool (1) according to claim 8 or 9, wherein the inner shell segment (200) protrudes from an up-hole end (1A) and a down-hole end (1 B) of the counter hold sleeve (300) and the outer shell segment (100) protrudes from the down-hole end (1 B) of the counter hold sleeve (300).11 . The fishing tool (1) according to any of claims 8 to 10, further comprising a first friction coupling (600) arranged between the counter hold sleeve (300) and the inner shell segment (200).

12. The fishing tool (1) according to any of claims 8 to 11 , further comprising a second friction coupling (700) arranged between the counter hold sleeve (300) and the outer shell segment (100).

13. The fishing tool (1) according to any of claims 8 to 12, further comprising a ratchet device (800) located between the counter hold sleeve (300) and the outer shell segment (100), wherein the ratchet device (800) is moveable between a locked position and an unlocked position;wherein in the locked position the ratchet device (800) blocks rotation of the outer shell segment (100) in one rotational direction; and in the unlocked position allows rotation of the outer shell segment (100) in both rotational directions.

14. The fishing tool (1) according to any preceding claim, wherein an up-hole end (1 A) of the inner shell segment (200) comprises an inner shell segment holding portion (210) configured to provide secure engagement for rotation of the inner shell segment (200) in use.

15. The fishing tool (1) according to any preceding claim, further comprising a determination means for determining if the closed chamber (1200A) comprises a lost object (2).

16. The fishing tool (1) according to claim 15, wherein the determination means comprises a piston (500) configured to be selectively advanced through the closed chamber (1200A).

17. The fishing tool (1) according to claim 16, wherein in the closed configuration the piston (500) at least partially forms the closed chamber (1200A).

18. The fishing tool (1) according to claim 16 or 17, further comprising a manipulator (400) configured to be rotatable to advance the piston (500) in use.

19. The fishing tool (1) of claim 18, wherein the manipulator (400) comprises: a manipulator holding portion (410) at or near an up-hole end (1A) of the manipulator (400), the manipulator holding portion (410) configured to provide secure engagement for rotation of the manipulator (400) in use; and a threaded portion registered with a threaded portion of the piston (500), such that rotation of the manipulator (400) advances the piston (500) towards the down-hole end (1 B) of the tool (1).

20. The fishing tool (1) according to any of claim 18 to 19, wherein the manipulator (400) is arranged on a central longitudinal axis of the tool (1).

21. The fishing tool (1) according to any preceding claim, further comprising a catching arrangement (900) located at or near a down-hole end (1 B) of the tool (1), the catching arrangement (900) configured to allow unidirectional passing of the object (2) to be fished in use.

22. The fishing tool (1) according to claim 21 , wherein the catching arrangement (900) comprises one or more radially outwardly biased fingers (901) configured to move radially inwards to allow the unidirectional passing of the object (2) and to block passing of the object (2) in the opposite direction, in use.

23. The fishing tool (1) according to any preceding claim, wherein the outer shell segment (100) is provided with first (101) and second (102) radially inward protrusions and the inner shell segment (200) is provided with first (201) and second (202) radially outward protrusions; wherein the radially inward protrusions (101 , 102) are arranged relative to the radially outward protrusions (201, 202) such that in use: the inner shell segment (200) can be rotated without the inward (101 , 102) and outward (201, 202) protrusions abutting; and the inner shell segment (200) can be rotated with the inward (101, 102) and outward (201, 202) protrusions abutting thereby also rotating the outer shell segment (100).

24. The fishing tool (1) according to claim 23, wherein the first (101) and second (102) inward protrusions are arranged around 180 degrees apart and the first (201) and second (202) outward protrusions are arranged around 180 degrees apart.

25. A system for performing a fishing operation in a wellbore (3), the system comprising: a fishing tool (1) according to any of claims 1 to 24; a running tool; wherein the running tool is configured to attach to the fishing tool (1) in use and advance the fishing tool (1) into the wellbore (3).

26. The system according to claim 25, wherein the running tool is a wireline or coil tubing tool.

27. The system according to claim 25 or 26, further comprising said wellbore (3).

28. The system according to any of claims 25 to 27, wherein the wellbore (3) is a horizontal or deviated wellbore.

29. The system according to any of claims 25 to 28, wherein the running tool comprises an advancement means configured to advance the fishing tool (1) along the wellbore (3).

30. The system according to any of claims 25 to 29, wherein the running tool comprises a first engagement means configured to engage the inner shell segment (200) to provide selective rotation of the inner shell segment (200).

31. The system according to claim 30, wherein the running tool comprises a second engagement means configured to engage the outer shell segment (100) to provide selective rotation of the outer shell segment (100).

32. The system according to any of claims 25 to 31 , wherein the running tool comprises a first engagement means configured to engage the inner shell segment (200) and the outer shell segment (100) to provide selective rotation of the inner and outer (100) shell segments.

33. A method of fishing a lost object (2) in a subterranean well (3), the method comprising the steps of: a. providing a fishing tool (1) according to any of claims 1 to 24; b. locating the fishing tool (1) in a subterranean well (3) in the scooping configuration; c. locating the open chamber (1200B) above the lost object (2); d. rotating the outer (100) and / or inner (200) shell segment(s) to scoop the object(2) into the open chamber (1200B); ande. providing relative rotation of the inner (200) and outer (100) shell segments to move the fishing tool (1) to the closed configuration to capture the object (2).

34. The method according to claim 33, wherein step b. further comprises running the fishing tool (1) into the well (3) in the closed configuration and then moving the fishing tool (1) to the scooping configuration.

35. The method according to claim 33 or 34, wherein step b. further comprises running the fishing tool (1) into a horizontal or deviated well.

36. The method according to any of claims 33 to 35, wherein step b. further comprises running the fishing tool (1) into a well (3) on wireline or on coil tubing.

37. The method according to any of claims 33 to 36, wherein step e. further comprises rotating the inner shell segment (200) whilst holding the outer shell segment (100) stationary.

38. The method according to any of claims 33 to 37, further comprising a step of: f. removing the fishing tool (1) from the subterranean well (3) to recover the lost object (2).

39. A fishing tool (T) for performing a fishing operation to recover an object (2’) from a low-side of a horizontal or deviated subterranean well (3’), comprising: a shell segment (100’) forming an open chamber (1200’B) for receiving said object (2’) into in use; wherein the tool (T) is configured to be moveable between: a high-side configuration in the wellbore (3’) wherein the shell segment (100’) is located above the object (2’) to be recovered; and a low-side configuration wherein the shell segment (100’) is located on the low-side of the wellbore (3’); wherein the shell segment (100’) is arranged to be rotatable around a central axis of the tool (T) such that the shell segment (100’) can scoop the object (2’) into the open chamber (1200’B) of the tool (T) as the tool (T) moves from the high-side configuration to the low-side configuration in use.

40. The fishing tool (T) according to claim 39 wherein the shell segment (100’) is a substantially hemicylindrical shell segment (100’).

41. The fishing tool (T) according to claim 39 or 40, wherein the shell segment (100’) comprises a shell segment top face (100A’) at least partially forming the open chamber (1200’B).

42. The fishing tool (T) according to any of claims 39 to 41 , wherein the shell segment (100’) comprises a biasing means configured to bias the object (2’) towards the open chamber (1200’B) when the object (2’) is scooped by the shell segment (100’) in use.

43. The fishing tool (T) according to any of claims 39 to 42, further comprising a counter hold sleeve (300’) configured to house part of the shell segment (100’).

44. The fishing tool (T) according to claim 43, wherein the counter hold sleeve (300’) comprises a counter hold sleeve holding portion (310’) configured to be held to prevent rotation of the counter hold sleeve (300’) in use.

45. The fishing tool (T) according to claim 43 or 44, wherein the shell segment (100’) protrudes from an up-hole end (1 A’) and a down-hole end (1 B’) of the counter hold sleeve (300’).

46. The fishing tool (T) according to any of claims 43 to 45, further comprising a friction coupling (600’) arranged between the counter hold sleeve (300’) and the shell segment (100’).

47. The fishing tool (T) according to any of claims 43 to 46, further comprising a ratchet device (800’) located between the counter hold sleeve (300’) and the shell segment (100’), wherein the ratchet device (800’) is moveable between a locked position and an unlocked position; wherein in the locked position the ratchet device (800’) blocks rotation of the shell segment (100’) in one rotational direction; andin the unlocked position allows rotation of the shell segment (100’) in both rotational directions.

48. The fishing tool (T) according to any of claims 39 to 47, wherein an up-hole end (1A’) of the shell segment (100’) comprises a shell segment holding portion (110’) configured to provide secure engagement for rotation of the shell segment (100’) in use.

49. The fishing tool (T) according to any of claims 39 to 48, further comprising a determination means for determining if the open chamber (1200’B) comprises a lost object (2’).

50. The fishing tool (T) according to claim 49, wherein the determination means comprises a piston (500’) configured to be selectively advanced through the open chamber (1200’B).51 . The fishing tool (T) according to claim 50, wherein in the high-side configuration and / or the low-side configuration, the piston (500’) at least partially forms the open chamber (1200’B).

52. The fishing tool (T) according to claim 50 or 51 , wherein the piston (500’) comprises a cover portion (502’) arranged to close the chamber (1200’B) to secure the object (2’) within the chamber (1200’B).

53. The fishing tool (T) according to any of claims 50 to 52, further comprising a manipulator (400’) configured to be rotatable to advance the piston (500’) in use.

54. The fishing tool (T) according to claim 53, wherein the manipulator (400’) comprises: a manipulator holding portion (410’) at or near the up-hole end (1 A’) of the manipulator (400’), the manipulator holding portion (410’) configured to provide secure engagement for rotation of the manipulator (400’) in use; and a threaded portion registered with a threaded portion of the piston (500’), such that rotation of the manipulator (400’) advances the piston (500’) towards the down-hole end (1 B’) of the tool (T).

55. The fishing tool (T) according to claim 53 or 54, wherein the manipulator (400’) is arranged on the central longitudinal axis of the tool (T).

56. A system for performing a fishing operation in a wellbore (3’), the system comprising: a fishing tool (T) according to any of claims 39 to 55; and a running tool; wherein the running tool is configured to attach to the fishing tool (T) in use and advance the fishing tool (T) into the wellbore (3’).

57. The system according to claim 56, wherein the running tool is a wireline or coil tubing tool.

58. The system according to claim 56 or 57, further comprising said wellbore (3’).

59. The system according to claim 58, wherein the wellbore (3’) is a horizontal or deviated wellbore (3’).

60. The system according to any of claims 56 to 59, wherein the running tool comprises an advancement means configured to advance the fishing tool (T) along the wellbore (3’).

61. The system according to any of claims 56 to 60, wherein the running tool comprises an engagement means configured to engage the shell segment (100’) to provide selective rotation of the shell segment (100’).

62. A method of fishing a lost object (2’) in a subterranean well (3’), the method comprising the steps of: a. providing a fishing tool (T) according to any of claims 39 to 55; b. locating the fishing tool (T) in a subterranean well (3’) in the high-side configuration with the open chamber (1200’B) above the object (2’); and d. rotating the shell segment (100’) to position the tool (T) in the low-side configuration, thereby scooping the object (2’) into the open chamber (1200’B).

63. The method according to claim 62, wherein step b. further comprises running the fishing tool (T) into the well (3’) in a run-in-hole configuration and then moving the fishing tool (T) to the high-side configuration.

64. The method according to claim 62 or 63, wherein step b. further comprises running the fishing tool (T) into a horizontal or deviated well.

65. The method according to any of claims 62 to 64, wherein step b. further comprises running the fishing tool (T) into the well (3’) on wireline or on coil tubing.

66. The method according to any of claims 62 to 65, further comprising a step of: e. removing the fishing tool (T) from the subterranean well (3’) to recover the lost object (2’).

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