Patent Description:
In the field of well technology, fishing tools are used to retrieve various types of downhole equipment, which is installed or lost in the well, normally referred to as "a fish". Such equipment may for instance be a wellbore packer, a downhole pump, or other downhole tools. Such pieces of equipment are commonly provided with a profile for engagement with a fishing tool. Sometimes, however, such as after an unintended occurrence, there may be equipment stuck in the well without such a profile or with a damaged profile.

There are known various types of fishing tools, which are run by using different methods. Some are run on wireline, such as a slick line or an electric line. Performing fishing operations with a wireline is usually the most cost-efficient method. Other types of fishing tools are run on coiled tubing (CT), drill pipe, or other tubular methods.

It sometimes happens that the operator is not able to pull the fish out of the wellbore. He must then release the fishing tool from the fish to retrieve the tool. For fishing tools run on wireline, such release is performed by providing a downwardly or upwardly directed force onto the fishing tool. Typically, this force will shear off one or more shear pins, which releases the engagement between the fishing tool and the fish.

In more modern, horizontally drilled wells, it is difficult to apply such a mechanical release force onto the fishing tool. Due to friction forces, the operator cannot rely on gravity to provide the needed force. As a result, the operators need to run the fishing tool on a coiled tubing or a drill string, thus increasing complexity and cost. Alternatively, the operators may apply an additional release system above the fishing tool, but this results in a significant increase of the fish length after release.

Publication <CIT> discloses a fishing tool with a fish disconnection function. In this solution, a preloaded spring is configured to disengage the fishing tool from the fish. To activate the spring, a lug is pulled out of a spring-arresting engagement. The lug is pulled away by means of an electric motor. For this solution, the disengagement force, by which a fish engagement means shall be pulled out of engagement with the fish, is governed by the spring. Consequently, when the spring is activated, it will exert a predetermined force for disengagement. Moreover, this force can be applied only once, i.e. there it is not possible to make more than one disengagement attempt.

European patent application publication <CIT> discloses a wireline fishing tool having an electric actuator for attachment to the fish in the wellbore.

An object of the present invention may be to provide a fishing tool that can be run on a wireline and that can be used both in vertical and horizontal wells.

Another object of the present invention may be to provide a wireline fishing tool that can be disengaged from a connected fish by means of a novel fish disengagement arrangement.

An object of the invention may be to provide a wireline fishing tool that has a fish disengagement arrangement by means of which one may apply a disengagement force of varying size, and/or repeated application of a disengagement force.

According to the present invention, there is provided a fishing tool configured to retrieve a fish from a wellbore. The fishing tool has a fish engagement arrangement with fish engagement means configured to lock the fishing tool to the fish inside a well. The fish engagement means can typically be in form of latching dogs or similar components. The fishing tool further comprises an electrically actuated fish disengagement arrangement, which is configured to unlock the fishing tool from the fish. The fish disengagement arrangement has an electric actuator. The fish disengagement arrangement comprises a direct mechanical force link between the electric actuator and the fish engagement means. The direct mechanical force link is configured to connect a mechanical force from the electric actuator to the fish engagement means. The fishing tool further comprises an electric battery and a control unit, wherein the control unit is programmed to perform repeated disconnection attempts, by operating the electric actuator, in a situation where a first disconnection attempt is unsuccessful.

Thus, with such a fishing tool, the mechanical force produced by the electric actuator, such as an electric motor, is linked to the fish disengagement means, such as latching dogs.

With such a direct mechanical force link, it will be possible to re-position the fish disengagement means in the operating position with the electric actuator, after having been moved to a disengaging position.

Furthermore, the operator may in some embodiments choose the size of the disengaging force produced by the electric actuator.

Moreover, the operator may in some embodiments perform repeated attempts for disconnecting the fishing tool from the fish, in cases where the first attempt is not successful.

In some embodiments of the fishing tool according to the invention, the fish disengagement arrangement comprises a rotation to linear converter and the electric actuator is an electric rotary motor, which is functionally connected to the rotation to linear converter. In that way, a linear movement is provided by rotation of the electric rotary motor, wherein the linear movement provides disengagement of the fishing tool from the fish.

In some embodiments involving such a control unit, the control unit cab be programmed to increase a disconnection force that is output from the electric actuator in succeeding disconnection attempts. Hence, in a situation where the fish engagement means seems to be stuck, the control unit can increase the mechanical disconnection force as a measure for disconnecting the fish despite of the fish engagement means being stuck.

In some embodiments, the fish engagement arrangement of the fishing tool may advantageously comprise a cone that is axially fixed with respect to a tool housing and the fish engagement means, in the form of a plurality of latching dogs that are configured to slide against the cone when moved axially with respect to the tool housing. Furthermore, the fish disengagement arrangement may be configured to move the latching dogs with respect to the cone upon actuation.

The fishing tool may in some embodiments further comprise a mechanical disconnection arrangement having one or more shear pins. In such embodiments, the mechanical disconnection arrangement may serve as an auxiliary disconnection means. Hence, in a situation where the electric actuator or associated components malfunctions, the operator may use the mechanical disconnection arrangement as an auxiliary measure.

The mechanical disconnection arrangement can advantageously be configured to pull the latching dogs off their engagement with the cone when the shear pins are in a shorn off state.

While the present invention has been discussed in general terms above, a more detailed example of embodiment will be given in the following with reference to the drawings, in which.

<FIG> illustrates a typical scenario where a fishing tool according to the present invention is used. A piece of downhole equipment, or "a fish" <NUM>, is positioned in a subterranean well <NUM> and shall be retrieved. In the situation shown in <FIG>, the well is a subsea well. The fish <NUM> is positioned in a horizontal portion of the well. A fishing tool <NUM> is run on a wireline <NUM> from an offshore surface installation <NUM>. The operator will connect the fishing tool <NUM> to the fish <NUM>, and then pull both back up to the surface. If the operator is not able to push the fish <NUM> loose, he will disconnect the fishing tool <NUM> from the fish <NUM>, and retrieve only the fishing tool.

<FIG> depicts a wireline fishing tool <NUM> according to the invention with a cross section side view, such as the one depicted in <FIG>. At a front end, the tool <NUM> has a fish engagement arrangement <NUM>. The fish engagement arrangement <NUM> is configured to lock against radially inwardly facing walls of a bore of a fish inside a wellbore. The fish engagement arrangement <NUM> comprises fish engagement means that are configured to engage and disengage with the fish <NUM>. In this embodiment, the fish engagement means of the fish engagement arrangement <NUM> is in the form of axially moving latching dogs <NUM>, which are configured to slide on a cone <NUM> of a central stem <NUM>. The latching dogs <NUM> are arranged on the ends of latching fingers <NUM>, which allow the latching dogs <NUM> to move radially when sliding on the cone <NUM>. This will be described in closer detail further below.

At an axial distance from the front end, the tool <NUM> has an electric motor <NUM>. The electric motor <NUM> is functionally connected to a gear <NUM>, which reduces the rotational output from the motor. A rotating shaft <NUM> connects to the gear <NUM>. The rotating shaft is supported between a rear rotary bearing <NUM> and a front rotary bearing <NUM>.

At a front portion of the rotating shaft <NUM>, it is provided with a threaded section <NUM>. On the threaded section <NUM> of the rotating shaft <NUM>, there is arranged a nut <NUM>. The threaded section <NUM> and the nut <NUM> form a rotation-to-linear converter, which converts the rotary movement of the electric motor into a liner movement. The linear movement of the nut <NUM> is parallel to the axial direction of the tool <NUM>.

The nut <NUM> is connected to a pair of keys <NUM>. The keys <NUM> are positioned in two slots <NUM> and thus prevent the nut <NUM> from rotating along with the rotating shaft <NUM>. The keys <NUM> also transmit a disengagement force, as will be discussed in detail further below.

Also shown in <FIG> are a plurality of seals, which seal the tool internals from the well pressure. As the use of such seals are well known to the skilled person, they are not discussed further herein.

<FIG> is an enlarged cross section view showing a front portion of the tool <NUM> shown in <FIG>. In <FIG>, the fishing tool <NUM> is shown in a non-engaged position, i.e. it is not engaged with a fish. In position shown in <FIG>, the latching dogs <NUM> are in a forward and hence radial outer position on the cone <NUM>. This position is maintained with a spring <NUM> that bias the latching dogs <NUM> towards this forward position.

The latching dogs <NUM> are arranged on the ends of the respective latching fingers <NUM>, which extend in an axial direction from a common latching sleeve <NUM>. The latching sleeve <NUM> is configured to slide axially on a cylindrical portion of the central stem <NUM>. As now will be appreciated by the skilled person, when in a forward position, the latching dogs <NUM> will be in an outer radial position. Further, when in a retracted position, the latching dogs <NUM> will be in a radial inner position, as they slide down (radially inwards) on the cone <NUM>.

The axial extension of said spring <NUM> is in a rearward direction confined with a spring shoulder <NUM> arranged on a shaft housing <NUM>. The rotating shaft <NUM> extends through a bore <NUM> in the shaft housing <NUM>. At a front end, the spring <NUM> abuts a latching bias bottom shoulder <NUM> on an actuation member <NUM>. The actuation member <NUM> is axially fixed to the latching dogs <NUM> via a sliding sleeve <NUM>.

A tool housing, in the form of a housing sleeve <NUM>, is arranged outside the shaft housing <NUM> and the central stem <NUM>. The shaft housing <NUM> is axially fixed to the central stem <NUM>.

The fishing tool <NUM> according to the embodiment shown in <FIG> is configured to engage inside the bore of a fish. Moreover, when in the situation shown in <FIG>, the tool is prepared for entering into such engagement.

<FIG> is a cross section side view corresponding to <FIG>, however depicting the situation where the fishing tool <NUM> is entering into engagement with a fish <NUM>. The fish <NUM> has a bore <NUM>, into which a front head of the central stem <NUM> is inserted. While the central stem <NUM> fits into the bore <NUM>, the latching dogs <NUM> do not when in the situation shown in <FIG> (namely when in the radially outer position). When the latching dogs <NUM> abut the fish (at the end of the bore <NUM>), they are forced rearwards with respect to the central stem <NUM>, along with the latching fingers <NUM>, the latching sleeve <NUM>, the sliding sleeve <NUM>, and the latching bias bottom shoulder <NUM>. During this rearward movement, the spring <NUM> is compressed. Moreover, the engagement between an outer, inclined dog face <NUM> on each of the latching dogs <NUM>, and the edge of the bore <NUM>, contributes in moving the latching dogs <NUM> radially inwards.

Eventually, when sliding on the cone <NUM>, as the central stem <NUM> is moved axially forward into the bore <NUM> of the fish <NUM>, the latching dogs <NUM> will fit inside the bore <NUM>. The spring <NUM> will then push latching dogs <NUM> forward and ensure wedging of the latching dogs <NUM> between the cone <NUM> and the bore <NUM>, when the fishing tool (central stem) is pulled backwards.

Then, as the fishing tool <NUM> with its central stem <NUM> is pulled backwards, the latching dogs <NUM> will be squeezed between the bore <NUM> and the cone <NUM>. This position is shown in <FIG>. Latching teeth <NUM> arranged on the radially external face of each latching dog <NUM> will be forced into engagement with the bore <NUM>, thus ensuring a fixed connection between the fishing tool <NUM> and the fish <NUM>.

While this embodiment depicts connection of the fishing tool <NUM> to a slick bore <NUM>, other embodiments may involve connection to a fish having a locking profile. Furthermore, some embodiments of the fishing tool may be configured to connect to an external face or profile of the fish, while other embodiments may be configured to connect to the internal face (bore) or profile of the fish.

As discussed introductorily, in some cases it may happen that the operator is not able to pull the fish <NUM> loose from the wellbore. He then needs to disengage the fishing tool <NUM> from the fish <NUM>, so that he can retrieve the fishing tool <NUM>. It is common to do this by exerting a forwardly directed disengagement force on the fishing tool <NUM>.

With a fishing tool according to the present invention, however, the operator can disengage the fishing tool <NUM> from the fish <NUM> in another manner. <FIG> depicts disengagement of the fishing tool <NUM> from the fish <NUM> by means of an electrically actuated fish disengagement arrangement <NUM>. By rotation of the rotating shaft <NUM>, the nut <NUM> and the keys <NUM> are moved in an axially rearward direction. As discussed above, such rotation is accomplished by operation of the electric motor <NUM> (cf.

In this embodiment, the fish disengagement arrangement <NUM> comprises inter alia the electric motor <NUM>, the gear <NUM>, the rotating shaft <NUM> and the rotation to linear converter <NUM>, <NUM>.

The keys <NUM> extend through slots <NUM> in the shaft housing <NUM>, and are attached to a disengagement sleeve <NUM>. The disengagement sleeve <NUM> is consequently moved axially rearwards along with the nut <NUM> and keys <NUM>, when operating the electric motor <NUM>.

At a rear end of the disengagement sleeve <NUM>, there is a rearward facing disengagement shoulder <NUM>. The disengagement shoulder <NUM> is configured to abut against a forward facing disengagement face <NUM> of the actuation member <NUM>. Hence, by operation of the electric motor <NUM>, the operator pulls the latching dogs <NUM>, which are axially fixed with respect to the actuation member <NUM>, in a rearward direction, with respect to the central stem <NUM>. As a result, the latching dogs <NUM> are removed from their engagement with the cone <NUM>, and may thus be released from engagement with the fish <NUM>.

Notably, when operating the electric motor <NUM> to pull the latching dogs <NUM> in an axially rearward direction, the latching dogs <NUM> will initially remain axially fixed with respect to the fish <NUM>, while the central stem <NUM> is moved axially forward.

As the skilled person now will appreciate, there is a direct mechanical force link <NUM> between the electric motor <NUM> and the latching dogs <NUM>. In this embodiment, the direct mechanical force link <NUM> comprises the rotating shaft <NUM>, the rotation-to-linear converter <NUM>, <NUM>, the disengagement sleeve <NUM>, and the latching fingers <NUM>.

As a result of the direct mechanical force link <NUM>, a disengaging force from the electric actuator <NUM> can be transferred directly onto the fish engagement means / latching dogs <NUM>. Consequently, one is not limited to the preload of a disengagement spring, which typically will be of a significantly lower force than the force from the electric actuator <NUM>. The magnitude of the disengaging force from the electric actuator <NUM>, which is applied on the fish engagement means <NUM> (i.e. the latching dogs) will of course depend on the gear <NUM>, through which the force is transmitted. It will also depend on the pitch angle of the rotation-to-linear converter <NUM>, <NUM>.

Advantageously, embodiments according to the present invention may also comprise a mechanical disconnection arrangement. Such embodiments are configured to be disengaged by means of a mechanical disengagement force, as an auxiliary disengagement measure. With the shown embodiment, such disengagement force is transmitted to the central stem <NUM>, as shown in <FIG>. By moving the central stem <NUM> forwards, as a result of the said disengagement force, the cone <NUM> is moved away from its engagement with the latching dogs <NUM>, thus allowing the latching dogs <NUM> to disengage from the bore <NUM>. The housing sleeve <NUM> of the fishing tool <NUM> abuts the edge of the bore <NUM> of the fish <NUM>, and pulls the latching dogs <NUM> off the cone <NUM> of the central stem <NUM>. This compresses the spring <NUM>, and the central stem <NUM> and its cone <NUM> travels further into the fish. The mechanical disengagement arrangement is discussed in better detail below, with reference to <FIG>.

<FIG> depict an alternative embodiment of a fishing tool <NUM> according to the present invention. Most of the components of this embodiment correspond to the embodiment discussed above with reference to <FIG>, and their function will not be discussed again. Differing from the previous embodiment though, is the fish engagement arrangement <NUM>.

While the fish engagement arrangement <NUM> of the embodiment depicted in <FIG> is configured for latching to a slick bore of a fish, the embodiment shown in <FIG> is configured to latch with a profile <NUM> in the bore <NUM> of the fish <NUM>.

<FIG> depicts the situation before entering into the bore <NUM> of the fish <NUM>. In the situation shown in <FIG>, the central stem <NUM> and the latching dogs <NUM> have entered into the bore <NUM>. The latching dogs <NUM> have moved axially beyond the profile <NUM> in the fish. The situation in <FIG> corresponds substantially to the situation shown in <FIG>, which was discussed above.

In order to set the locking engagement between the fishing tool <NUM> and the fish <NUM>, the central stem <NUM> is pulled rearwards, so that the latching dogs <NUM> are prevented from moving radially inwards and out of their engagement with the profile <NUM>. This is shown in <FIG>.

As with the embodiment discussed with reference to <FIG>, the tool can be released, as an auxiliary measure, by applying a mechanical force onto it in the axial forward direction.

Normally however, if the operator needs to disengage the fishing tool <NUM> from the fish <NUM>, he will actuate the electric disengagement arrangement. This is, as discussed with the previous embodiment above and now depicted in <FIG>, done by operation of the electric motor <NUM>. Actuation of the electric motor <NUM> makes the disengagement sleeve <NUM> move axially rearwards. This makes the central stem <NUM> move axially forwards, so that the latching dogs <NUM> may move radially inwards and disengage from the profile <NUM> in the bore <NUM> of the fish <NUM>.

<FIG> depicts another alternative embodiment of the present invention, wherein the locking dogs <NUM> are configured to slide against an outer, thus inwardly facing cone <NUM>. In this embodiment, the fishing tool is configured to engage on the external faces of a fish (not shown). Hence, latching teeth <NUM> on the latching dogs <NUM> face radially inward, and are configured to "bite" into the external face of the fish.

<FIG> depicts a further alternative embodiment of the present invention, wherein the locking dogs are configured to engage on an outer profile of the fish (not shown).

The fishing tool according to the embodiments depicted in <FIG> may have a mechanical release arrangement. However, such a mechanical disconnection arrangement may operate in a different manner than the one discussed with reference to <FIG>, and <FIG>. Other embodiments according to the present invention, may be without a mechanical disconnection arrangement.

Corresponding to the embodiments previously discussed, by operating the electric disengagement arrangement of the fishing tool <NUM>, i.e. by operating the electric motor <NUM>, the operator may retract the latching dogs <NUM> with respect to the cone <NUM>. This will move the cone <NUM> axially forward, with respect to the latching dogs <NUM>, and hence let the latching dogs <NUM> disengage from their engagement with the fish.

When the fishing tool <NUM>, such as according to the embodiments discussed herein, or according to other embodiments falling within the scope of the present invention, is run on an electric wireline, the operator may control the electric motor <NUM> (and hence the disengagement arrangement) from the surface / topside.

The fishing tool <NUM> comprises a battery <NUM> and a control unit <NUM>, which are schematically depicted in <FIG> (at a rear portion of the tool). The operator may program the control unit <NUM> to operate the electric motor <NUM> a predetermined time after starting the control unit <NUM>. Then, should the operator not be able to retrieve the fish <NUM>, the fishing tool <NUM> will automatically disengage from the fish <NUM> after the set time. The control unit <NUM> will connect power from the battery <NUM> to the electric motor <NUM>, when the set time has lapsed.

<FIG> depict details of a mechanical disengagement arrangement present in the embodiment discussed above with reference to <FIG>. Reference is also given to <FIG>, which depicts an enlarged portion of <FIG> for better view.

A rear portion of the housing sleeve <NUM> is positioned radially outside a rear portion of the shaft housing <NUM>. In the situation shown in <FIG>, the housing sleeve <NUM> is axially fixed with respect to the shaft housing <NUM> by means of some shear pins <NUM>. The shear pins <NUM> extend through the housing sleeve <NUM> and into a threaded bore in the external face of the shaft housing <NUM>. The rear portion of the housing sleeve <NUM> is provided with a ratchet ring receiving recess <NUM>, which receives a lock ring <NUM>, this is best visible in <FIG>. The lock ring <NUM> is provided with radially inwardly directed ring ratchet profile <NUM>, which mates with oppositely shaped, outwardly directed outer ratchet profile <NUM> on the outer face of the shaft housing <NUM>. The lock ring may be a split ring.

The shaft housing <NUM> is provided with a stop shoulder <NUM> that faces axially forward (i.e. towards the fish). As shown in <FIG> and <FIG>, between the stop shoulder <NUM> and a rear edge <NUM> of the housing sleeve <NUM>, there is arranged a stop ring <NUM>. The stop ring <NUM> prevents the housing sleeve <NUM> from moving axially backwards with respect to the shaft housing <NUM>.

However, if the stop ring <NUM> is removed, the housing sleeve <NUM> may move axially backwards on the shaft housing <NUM>. Such a backwardly directed force can be provided by forcing the fishing tool <NUM> forwards, i.e. into the well. Such a situation is shown in <FIG>, where the forward edge of the housing sleeve <NUM> abuts the edges of the fish <NUM>. The housing sleeve <NUM> is consequently forced radially backwards with respect to the stem <NUM> and the shaft housing <NUM>, and the shear pins <NUM> will shear off.

When the shear pins <NUM> have been shorn off, the housing sleeve <NUM> starts to move backwards, cf. The lock ring <NUM> is then also moved backwards with respect to the shaft housing <NUM>, making the ring ratchet profile <NUM> slide over the opposite outer ratchet profile <NUM>.

A housing sleeve edge 20a moves axially towards an oppositely facing sliding sleeve edge 39a. After some movement, the housing sleeve edge 20a will abut the sliding sleeve edge 39a, so the axial backward movement of the housing sleeve <NUM> pulls the sliding sleeve <NUM> in the same direction. Consequently, the latching dogs <NUM> are pulled off the cone <NUM>, thus releasing the fishing tool <NUM> from the fish <NUM>.

Eventually, the rear edge <NUM> of the housing sleeve <NUM> will abut against the stop shoulder <NUM> of the shaft housing <NUM>. Due to the engagement of the ring ratchet profile <NUM> and the outer ratchet profile <NUM>, the housing sleeve <NUM> cannot move forward on the shaft housing <NUM>, and is thus locked in this rear position. Consequently, the latching dogs <NUM> cannot return into their locking position.

With the shown embodiment, the operator may thus choose to remove the stop ring <NUM>, so that mechanical disconnection can be performed as an auxiliary measure. If the operator chooses not to allow for such auxiliary measure, the stop ring <NUM> simply remains on the fishing tool <NUM>, as shown in <FIG>.

While some embodiments of the fishing tool according to the present invention may be configured to be disengaged by applying a forward or rearward directed mechanical disengagement force, other embodiments may be without such a feature. That is, some fishing tools according to the invention may have both an electrically actuated release and a mechanical release, while other fishing tools according to the invention may have only an electrically actuated release.

Notably, the fishing tool according to the present invention is particularly well suited for being run on a wireline, such as a slick line or an electric line. However, it may also be run on other means, such as a coiled tubing or other tubular means.

In some embodiments, which are however not claimed here, the electric actuator, i.e. the electric motor <NUM> in the embodiments described above, may be activated by a primary electric signal. Alternatively, the activation may be initiated with a primary electric signal or a secondary electric signal. The primary electric signal will then be an electric signal transmitted directly from surface through an electric line, such as through an electric wireline, and the secondary electric signal will be provided with the control unit and a battery, as discussed above. In such embodiments, one will be able to pull out the fishing tool (i.e. release the fishing tool) even if there is a defect in the electric line that prevents the use of the primary electric signal.

Claim 1:
A fishing tool (<NUM>) configured to retrieve a fish (<NUM>) from a wellbore, the fishing tool (<NUM>) comprising a fish engagement arrangement (<NUM>) with fish engagement means (<NUM>) configured to lock the fishing tool (<NUM>) to the fish inside a well, wherein the fishing tool (<NUM>) further comprises an electrically actuated fish disengagement arrangement (<NUM>), which is configured to unlock the fishing tool (<NUM>) from the fish (<NUM>), wherein the fish disengagement arrangement (<NUM>) comprises an electric actuator (<NUM>), wherein the fish disengagement arrangement (<NUM>) comprises a direct mechanical force link (<NUM>) between the electric actuator (<NUM>) and the fish engagement means (<NUM>), wherein the direct mechanical force link (<NUM>) is configured to connect a mechanical force from the electric actuator (<NUM>) to the fish engagement means (<NUM>),
characterized in that it comprises an electric battery (<NUM>) and a control unit, wherein the control unit is programmed to perform repeated disconnection attempts, by operating the electric actuator (<NUM>), in a situation where a first disconnection attempt is unsuccessful.