Introduction

The present invention relates to a device for well intervention by means of a coiled tubing and a wireline. The device comprises a cantilever adapted to be arranged on a vessel that is configured to be brought to a petroleum well at sea.

In particular, the invention relates to a device for so called light well intervention in a petroleum well. The cantilever is adapted to be mounted on a self-elevating vessel that is positioned at an offshore petroleum well so that the cantilever is projecting over the petroleum well.

Prior art and their disadvantages

Light well interventions by means of coiled tubing or a wireline may be carried out in association with a wellhead platform by suspending a feeding device from a crane on a jack-up vessel. The feeding device, also denoted injector, is placed suspended over a wellhead in which the coiled tubing, or the wireline, is fed in and out. The method is risky in terms of safety because it is necessary for personnel to work at the feeding device. In some areas or jurisdictions, the solution is not allowed according to regulatory requirements. If the wellhead platform has a sufficient carrying capacity, the feeding device may be rigged up on the wellhead platform, whereas associated reels or drums are on the vessel. Both solutions include much rigging work and are relatively costly operations. A further problem is that the feeding device is restricted to well intervention by one of coiled tubing and wireline. If the other of coiled tubing and wireline is to be used, the feeding device must be disassembled and reconfigured with the new setup, which is time consuming and accordingly a costly operation.

In connection with plugging and abandoning a petroleum well it is common, besides plugging the petroleum well, to pull up at least an upper portion of the structural pipe of the petroleum well, such as casing and conductor casing. The extent of the work is governed by regulatory requirements.

Pulling a structural pipe up from the petroleum well subjects pulling equipment to relatively great strains and it is known to use drilling vessels for the purpose. Jack-up platforms have been used as well. The jack-up platform, termed a self-elevating vessel below, is typically provided with a derrick on a cantilever. The structural pipe can be divided at its pipe joints. If this is impossible, the well pipe must be cut. It is important that the well pipe is kept laterally stable for a cutting tool not to become pinched in a cutting groove. It has turned out that known gripping arms and lifting equipment may subject the well pipe projecting upwards to forces sideways so that the cutting tool gets pinched. When lifting equipment is used, it is also a problem to bring a loosened pipe portion from a vertical position into a horizontal position in a pipe rack.

Jack-up platforms that include derricks on cantilevers are relatively large. It takes a relatively great deal of time to position them correctly at the wellhead platform and the day rates are relatively high.

US9632553B1 discloses a system for drilling and well intervention. The system comprises a dis- placeable cantilever on that comprises a mast and an injector head for running and retrieving coiled tubulars from a reel.

Summary of the invention

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. In particular, the object of the invention is to provide a device that enables improved flexibility of well intervention of a petroleum well.

This object is achieved through features, which are specified in the description below and in the claims that follow.

The invention relates more particularly to device for well intervention by means of a coiled tubing and a wireline, wherein the device comprises a cantilever adapted to be arranged on a vessel that is configured to be brought to a petroleum well at sea. The device is characterized in that the device further comprises a displacement arrangement, a first feeding device for feeding the coiled tubing and a second feeding device for feeding the wireline, which first feeding device and second feeding device are arranged in engagement with said displacement arrangement, wherein the displacement arrangement is adapted to displace the first feeding device and the second feeding device horizontally in relation to the cantilever so that one of the first feeding device and the second feeding device is positioned at the petroleum well for enabling well intervention by the coiled tubing or the wireline.

The displacement arrangement enables the first feeding device and second feeding device to be displaced in relation to the cantilever. Thereby, the device enables the first and the second feeding device to be selectively positioned at an opening to the petroleum well. For example, in the event where the petroleum well is to be subjected to well intervention by means of coiled tubing followed by wireline, this is easily achieved by mean of first displacing the first feeding device to the petroleum well and performing the well intervention by coiled tubing and thereafter displacing the second feeding device to the petroleum well and performing the well intervention by wireline. Furthermore, the device comprising the first and the second feeding device has the advantage that at the same time that one of the first and the second feeding device is in operation at a petroleum well, the other of the first and the second feeding device can be prepared for a following well intervention.

The term "petroleum well" is used as a collective term for gas and oil wells. Here, the term also covers wells that have been used for injection of e.g. water or gas into a petroleum reservoir. The term "well centre" is to be understood as the centre of a petroleum well and also the centre of a well pipe extending from the petroleum well and up above the seabed.

Accordingly, the device provide the advantage of improved flexibility of well intervention. The invention furthermore allows the time of shifting between well intervention by coiled tubing and wireline is reduced compared with prior art devices.

According to an aspect of the invention, the displacement arrangement comprises means for displacing the first feeding device and the second feeding device independently of each other.

By means of arranging the first and the second feeding device independently displaceable, the weight subjected to a respective portion of the displacement arrangement to be reduced compared to when the first and the second feeding device are displaced as a unit. This improves the flexibility in the design of the displacement arrangement. Furthermore, at the same time that one of the first and the second feeding device is in operation at a petroleum well, the other of the first and the second feeding device can be prepared for a following well intervention at a secure distance.

According to an aspect of the invention, the cantilever is adapted to be arranged at a lattice of a plurality well centres connected to one or more petroleum wells, and wherein the displacement device is adapted to enable the first feeding device and the second feeding device to be displaced between different well centres.

By applying the device at the lattice of well centres, the first and the second feeding devices can quickly be shifted between different well centres. Accordingly, the device enables the time of the well intervention to be reduced compared with prior art devices.

According to an aspect of the invention, the displacement arrangement is configured to enable the first feeding device to be arranged at a first well centre and the second feeding device to be arranged at a second well centre for simultaneous well intervention in the first well centre by coiled tubing and the second well centre by wireline.

By enabling the first and the second feeding device to be displaced independently to different well centres, well interventions by coiled tubing and wireline can be performed simultaneously at the first and the second well centre. Accordingly, the device improves the flexibility of well intervention and enables the time of the well interventions to be reduced compared with prior art devices. According to an aspect of the invention, the cantilever is adapted to be arranged at a lattice of a plurality well centres connected to one or more petroleum wells, and the first feeding device and the second feeding device are arranged as a combined unit separated from each other by a distance which corresponds to a predetermined distance between the first and the second well centre.

According to an aspect of the invention, the cantilever comprises a work opening providing access to the one or more well centres. Preferably, the work opening is arranged elongated extending perpendicular to a projecting direction of the cantilever.

According to an aspect of the invention, the cantilever comprises one or more hatches adapted to adjustable cover at least a part of the work opening at positions next to the first feeding device and the second feeding. Preferably, the one or more hatches are configured to hold the weight of movements of personnel during the well intervention but not the weight of heavy machinery for the well intervention. Thereby, the one or more hatches can be of light weight and easy to manually open and close at the work opening.

According to an aspect of the invention, the displacement arrangement comprises a guide member for guiding the horizontal displacement of the first and second feeding device, wherein the guide member is extending on the cantilever in a first direction that is perpendicular to a projecting direction of the cantilever.

According to an aspect of the invention, the device comprises a support structure for holding the first feeding device and the second feeding device in an upright position, and the displacement arrangement comprises a guide member for guiding the horizontal displacement of the support structure along the guide member. The support structure is for example a framework of a plurality of connected structural members, such as a truss.

According to an aspect of the invention, the displacement arrangement comprises drive unit for displacing the support structure along the guide member. The drive unit is adapted to transmit force for the displacement of the first and the second feeding devices.

According to an aspect of the invention, the displacement arrangement comprises means for displacing the support structure along the guide member by at least one of skidding and rolling.

According to an aspect of the invention, the support structure comprises a base member comprising at least one receiving member adapted to be received by the guide member for enabling the horizontal displacement of the first and the second feeding devices. The receiving member comprises for example a sliding shoe or a wheel.

According to an aspect of the invention, the support structure comprises a first support portion for holding the first feeding device in an upright position and a second support portion for holding the second feeding device in an upright position, wherein the first support portion and the second sup- port portion are adapted to be displaced independently of each other on the guide member. By dividing the support structure in the first and the second support portion, the first and the second feeding device are allowed to be displaced independently of each other.

According to an aspect of the invention, the device comprises a single support structure for the first feeding device and the second feeding device, which single support structure is adapted to be displaced on the guide member.

While arranging the displacement arrangement as a single support structure increase the weight subjected to a respective portion of the displacement arrangement, the complexity and the number of components of the displacement arrangement is simplified.

According to an aspect of the invention, the cantilever comprises an upper deck comprising a space on which one or more components are adapted to be arranged, wherein the device further comprises coiled tubing storage unit adapted to store the coiled tubing for the well intervention by coiled tubing, which the coiled tubing storage unit is arranged at least partly enclosed under said upper deck of the cantilever.

By arranging the coiled tubing storage unit at least partly under the upper deck, the coiled tubing storage unit and thereto provided coiled tubing are at least partly protected from interaction with the surrounding environment. Accordingly, the risk of a malfunction of the coiled tubing storage unit is reduced.

According to an aspect of the invention, the coiled tubing storage unit comprises a coiled-tubing drum for winding and rewinding the coiled tubing to/from the first feeding device.

According to an aspect of the invention, the cantilever comprises an upper deck comprising a space on which one or more components are adapted to be arranged, wherein the device further comprises a wire storage unit adapted to store the wireline, which the wire storage unit is arranged enclosed under said upper deck.

By arranging the wire storage unit under the upper deck, the wire storage unit and thereto provided wireline is protected from influence from interaction with the surrounding environment. Accordingly, the risk of a malfunction of the wire storage unit is reduced. Furthermore, valuable space on the upper deck can be used for other purposes.

According to an aspect of the invention, the wire storage unit comprises a wireline drum for winding and rewinding the wireline to/from the second feeding device.

According to an aspect of the invention, the cantilever comprises an intervention deck on which the displacement arrangement is arranged, and where the intervention deck and the upper deck is arranged on separate locations of the cantilever. According to an aspect of the invention, the intervention deck is arranged lowered in relation to the upper deck.

It is also described a device for light well intervention by means of a coiled tubing or a wireline, wherein the device includes a cantilever mounted on a self-elevating vessel, the self-elevating vessel being arranged to be placed at an offshore petroleum well, the cantilever projecting over the petroleum well, and the cantilever being provided with a feeding device for at least the coiled tubing or the wireline in a position over the wellhead of the petroleum well, and the device being characterized by the cantilever being provided with a drum.

When the cantilever is placed over the wellhead, independently of whether the wellhead is on a wellhead platform or on a seabed, the feeding device is immediately ready for use, and rigging work is thereby kept at a minimum.

The cantilever may be provided with a coiled-tubing drum or a wireline drum. By the positioning of such drums on the cantilever, the device according to the invention forms a compact and relatively simple unit for coiled-tubing and wireline operations. An operator cabin may, with advantage, be placed at the coiled-tubing drum.

The feeding device may be at least horizontally displaceable or vertically displaceable. The feeding device may thereby be moved away from the well head if it is desirable to get to the wellhead with some other equipment.

The feeding device may be at a vertical distance from a pipe-puller encircling a well pipe and being mounted on the cantilever.

It is thus unnecessary to remove any other adjacent equipment for coiled-tubing or wireline operations to be performed. The solution enables quick change-overs between different operations in, for example, neighbouring petroleum wells.

The invention also relates to a liftboat which may include a crane, and which liftboat may further include a device as described above.

According to an aspect of the invention, the crane is adapted to be used for holding equipment for a simultaneous operation at a different wellhead than the wellhead at which the feeding device is in operation. Accordingly, the crane improves the flexibility of operation at the cantilever.

According to an aspect of the invention, the crane is adapted to hold the feeding device for at least the coiled tubing or the wireline in a position over the wellhead of the petroleum well , wherein the crane is configured to provide a displacement, such as a linear displacement, of the feeding device to and from the wellhead. The crane is for example an overhead crane, a rail crane and etcetera. The crane enables the feeding device for at least the coiled tubing or the wireline to be adjustably positioned over the wellhead of the petroleum well.

In another aspect, the invention relates, more specifically, to a method for light well intervention by means of a coiled tubing or a wireline, in which a device for the purpose includes a cantilever which is mounted on a self-elevating vessel, the self-elevating vessel being arranged to be placed at an offshore petroleum well, the cantilever projecting over the petroleum well in the position of application, and the method being characterized by including:

- arranging a feeding device for at least coiled tubing or wireline on the cantilever in a position over the wellhead of the petroleum well; and

- feeding coiled tubing or wireline into and out of the petroleum well by means of the feeding device from a drum arranged on the cantilever.

The method may include coiling and uncoiling the coiled tubing or wireline onto and off a coiled- tubing drum or a wireline drum, respectively, which is arranged on the cantilever.

It is also described a use of a cantilever, as disclosed in one of the embodiments above, on a lift- boat, the liftboat further being provided with a crane, so that, in the position of application, the cantilever is projecting over a petroleum well while the crane is simultaneously holding another feeding device over another petroleum well. From the cantilever, a coiled tubing or a wireline may be fed into and out of the petroleum well by means of a feeding device. From the cantilever, at least an upper portion of the well pipe of the petroleum well, such as casing or conductor casing, may be pulled up.

An arm for handling well pipes from a petroleum well is described as well, which arm may be provided with a pipe-gripper, wherein, when the arm is in a first position, the pipe-gripper may be arranged to grip a pipe portion of the well pipe while the well pipe is in the petroleum well, and wherein, when the arm is in a second position, the pipe gripper may be arranged to grip the pipe portion when the pipe portion is at a pipe rack, the device being characterized by the fact that the arm may be provided with two legs.

In the first position of the arm, the pipe-gripper may be arranged to grip the well pipe from the opposite side of the well pipe relative to the pipe rack.

By the pipe portion being gripped from this side, the movement of the arm between the first position and the second position is simplified. In this preferred embodiment, the movement between the two positions consists of a simple rotary motion.

The arm may comprise an A-frame. An A-frame constitutes a steady structure which may be supported, at the same time, in two rotary bearings which have a distance to the well centre, thereby allowing plenty of room for other equipment such as the pipe-puller. It is beneficial that the pipe-gripper is rotatable around the well centre. It may thereby perform screwing operations, for example during pipe removal after power tongs have broken out a pipe joint.

The pipe-gripper may be axially displaceable relative to the arm. The pipe-gripper may thereby hold a pipe portion in tension when the well pipe has to be cut, which may prevent damage to cutting equipment. Cutting a well pipe may be necessary if threaded pipe joints are impossible to break out.

The arm may be rotatable around a hinge axis. The arm may be rotatable around a horizontal hinge axis. The hinge axis of the arm may be on the opposite side of the well centre relative to the pipe rack. By the hinge axis being placed in this position, the arm may extend parallel to the well pipe in its first position.

The arm may be positioned on a cantilever which is mounted on a self-elevating vessel, the self- elevating vessel being arranged to be positioned at an offshore petroleum well, wherein, in the position of application, the cantilever projects over the petroleum well and the cantilever may be provided with a pipe-puller.

The arm may thus replace a crane on the self-elevating vessel which may thereby be used for other tasks at the same time. The pipe rack consists of an area which is designed to receive pipe portions, typically for temporary storing. The deck of the cantilever forms such an area here.

A method for pulling well pipes out of a petroleum well in connection with plugging and abandoning the petroleum well is described as well, wherein the method may include:

- pulling the well pipe up from the petroleum well by means of a pipe-puller;

- gripping a pipe portion of the well pipe by means of a pipe-gripper arranged on an arm, while the arm is in a first position;

- letting the pipe-gripper apply a tensile force to the pipe portion relative to the rest of the well pipe; and separating the pipe portion from the well pipe, characterized by the method further including:

- providing the arm with two legs;

- moving the arm to a second position in which the pipe portion can be placed in a pipe rack by the arm being rotated around a hinge axis.

The method may further include rotating the arm around a horizontal hinge axis.

The method may include positioning the arm on a cantilever which is mounted on a self-elevating vessel, the self-elevating vessel being arranged to be placed at an offshore petroleum well, wherein, in the position of application, the cantilever projects over the petroleum well.

The device and method according to the invention provide for the use of lighter and more reasonable equipment and methods simpler than those known. Brief description of drawings

In the following is described examples of preferred embodiments illustrated in the accompanying drawings, wherein :

Figure 1 shows a principle drawing of a self-elevating vessel that is provided with a device comprising a cantilever according to aspects of the invention;

Figure 2A-B shows a device according to a first aspect of the invention, where figure 2A discloses a side view of the device and figure 2B a top view of the device;

Figure 3 shows a first and second feeding device of the device in figures 2A-B in further detail;

Figure 4 shows a device according to a second aspect of the invention;

Figure 5 shows a cantilever according to the invention in perspective and on a larger scale;

Figure 6 shows a section of figure 5, but on a larger scale;

Figure 7 shows a side view of the projecting part of the cantilever of figure 6, an arm being in a first position, gripping around a well pipe;

Figure 8 shows the same as figure 7, but the arm is in a second position ; and

Figure 9 shows a principle drawing of a self-elevating vessel which is provided with a cantilever according to the invention, the cantilever being over a subsea well.

General description of the invention

In the drawings, the reference numeral 1 indicates a self-elevating vessel which includes movable legs 2 and, in the case of a ship, propelling machinery 4. The self-elevating vessel 1 is shown provided with a superstructure 6, a helipad 8 and a crane 10. In the figures, vessel 1 is in the form of a ship that is also called a liftboat. Another type of self-elevating vessel 1 is known as a jack-up.

The vessel is provided with a device 3 for well intervention according to different aspects of the invention that will be explained in the following. The device 3 comprises a cantilever 12 arranged on the self-elevating vessel 1 so that it projects from the self-elevating vessel 1 in over a platform 14, here in the form of a wellhead platform 14 which has access to at least one petroleum well 16 with an associated wellhead 17 and a well centre 18. The work opening 20 of the cantilever 12 corresponds to the well centre 18.

The platform 14 extends down through the water surface 22 and stands on a seabed 24. In the position of application shown, the self-elevating vessel 1 , too, stands on the seabed 24, by the self- elevating vessel 1 having been raised above the water surface 22 by means of the legs 2. Fig. 2A and 2B show a side view and a top view of a device 3 for well intervention by means of a coiled tubing 40 and a wire line 41 according to a first aspect of the invention.

The device 3 further comprises a displacement arrangement 35, a first feeding device 38a and a second feeding device 38b. The first feeding device 38a is configured to feed coiled tubing 40 for well intervention. The second feeding device 38b is configured to feed wireline 41 for the well intervention.

The displacement arrangement 35 is arranged on the cantilever 12 so that it extends along an intervention deck 39 of the cantilever 12 in a first direction S1 that is perpendicular to a projecting direction S2 of the cantilever 12. The first feeding device 38a and the second feeding device 38b are arranged in engagement with the displacement arrangement 35 that is adapted to displace the first feeding device 38a and the second feeding device 38b horizontally in relation to the cantilever 12 on the intervention deck 39. Thereby, the displacement arrangement 35 enables one of the first feeding device 38a and the second feeding device 38b to be positioned at the well centre 1 8 for a respective well intervention.

The displacement arrangement 35 comprises a guide member 70 extending along the intervention deck 39. In the disclosed example, the guide member 70 is in the form of two guide rails 72 arranged on the intervention deck 39 so that the guide rails 72 extend in the first direction S1 perpendicular to the projecting direction S2 of the cantilever 12.

The device 3 further comprises a support structure 75 for holding the first feeding device 38a and the second feeding device 38b in an upright position on the cantilever 12. The support structure 75 comprises means for enabling displacement of the first feeding device 38a and the second feeding device 38b by for example skidding. It shall be understood that also other types of horizontal displacement can be used, such as displacement by rolling.

In the shown example in fig. 2A-B and 3, the support structure 75 is arranged as a single unit that holds the first feeding device 38a and the second feeding device 38b together as a combined unit. The device 3 enables to selectively displace the first feeding device 38a or the second feeding device 38b to the well centre 18.

According to one aspect of the invention, the first feeding device 38a and the second feeding device 38b are separated from each other by a fixed distance D. The distance D is arranged so that it corresponds to a predetermined distance between two well centers 18, such as the distance separating well centers 18 in a lattice of well centres. Thereby, the device 3 enables well intervention in a first well centre 18a by means of for example coiled tubing 40 simultaneously with well intervention in a second well centre 1 8b by means of wireline 41 .

In fig. 2A-B only the first well centre 18a and the second well centre 1 8b are indicated. However, it shall be understood that the cantilever 12 may be provided with a work opening 20 providing ac- cess to the one or more well centres 18a, 18b, such as elongated slot extending perpendicular to a projecting direction S2 of the cantilever 12. The cantilever 12 may further comprises one or more hatches adapted to adjustable cover at least a part of the work opening 20 at positions next to the first feeding device 38a and the second feeding device 38b. The hatches are arranged intended to enable movements of personnel during the well intervention but not to hold machinery or components for the well intervention. Fig. 4 discloses a second aspect of the invention. The second aspect of the invention differs from fig. 2A-B and 3 in that the displacement arrangement comprises means for displacing the first feeding device 38a and the second feeding device 38b independently of each other on the guide member 70. Furthermore, the support structure 75 comprises a first support portion 76a that holds the first feeding device 38a in an upright position and a second support portion 76b that holds the second feeding device 38b in an upright position. The first support portion 76a and the second support portion 76b are adapted to be displaced independently of each other on the guide member 70.

According to a preferable aspect of the invention, the device arranged so that when positioned at a lattice of a plurality of well centres 18, the first feeding device 38a is adapted to be displaced to a first well centre 18a for well intervention by coiled tubing 40 and the second feeding device 38b is adapted to be displaced to a second well centre 18b for well intervention by wireline 41 . Thereby, the device 3 enables well intervention in the first well centre 1 8a by means of for example coiled tubing 40 with well intervention in the second well centre 18b by means of wireline 41 . The intervention by coiled tubing 40 and wireline 41 may be carried out in sequence or it may be carried out simultaneously. The first feeding device 38a or the second feeding device 38b may be idle when the other feeding device 38a, 38b is in operation.

With reference to fig. 2A-B, the cantilever 12 comprises an upper deck 60 for attaching or storing components for the well intervention and a lower deck 61 . A protected space is formed between the upper deck 60 and lower deck 61 .

The device 3 further comprises a coiled tubing storing unit 62 comprising a coiled-tubing drum 42 for winding and rewinding the coiled tubing 40 to/from the first feeding device 38a. The coiled tubing 40 is extending from the coiled-tubing drum 42 to an upper portion of the first feeding device 38a. The first feeding device 38a comprises a guide element for guiding the coiled tubing 40 into a vertical direction towards the well centre 1 8. The coiled tubing storing unit 62 is at least partly arranged covered by an upper deck 60 of the cantilever 12. Thereby, the coiled tubing storing unit 62 is at least partly protected from the surrounding environment.

The device 3 further comprises a wire storage unit 65 comprising a wireline drum 43 for winding and rewinding the wireline 41 to/from the second feeding device 38b. The wire storage unit 65 is arranged enclosed under said upper deck 60 at a separate location from the coiled tube storing unit 62. Thereby, the wire storage unit 65 is protected from the surrounding environment. Fig. 3 shows an example where the coiled tube storing unit 62 and the wire storage unit 65 are arranged on the upper deck 60. The wire storage unit 65 is at least partly protected by a casing. The wireline 41 is extending parallel along the upper deck 60 of the cantilever 12 and is redirected to an upper portion of the second feeding device 38b by means of one or several pulleys (not shown) at a lower portion of the second feeding device 38b. The wireline 41 is redirected into a vertical direction towards the well centre 1 8 by means of a pulley at the upper portion of the second feeding device 38b.

Reference is now made to figure 5, which shows the cantilever 12 viewed at an angle from above. In this alternative embodiment, the well centre 18 is encircled by a pipe-puller 26 which is arranged to pull up a well pipe 28. The pipe-puller 26 is on the cantilever 12 over the work opening 20. The well pipe 28 may consist of any type of pipe used to construct a petroleum well 16, for example a casing or a conductor casing.

An arm 30, here in the form of an A-frame, is hinged at rotary bearings 31 and is rotatable around a hinge axis 32. The rotary bearings 31 are directly or indirectly attached to the cantilever 12. The hinge axis 32 is here on the opposite side of the well centre 18 relative to a pipe rack 34.

At a vertical distance above the work opening 20, a framework 36 is arranged, carrying a horizontally displaceable feeding device 38 for a coiled tubing 40 or for a wireline 41 . The feeding device 38 may also be vertically displaceable. In the exemplary embodiment shown, a coiled-tubing drum 42 is arranged on the cantilever 12 as well. An operator cabin 44 is arranged behind the coiled- tubing drum 42 relative to the pipe rack 34. The feeding device 38 is of a design known per se and is not described in any further detail.

The pipe-puller 26, which is of a kind known per se, is provided with grippers 46, see figure 6. The grippers 46 are displaceable in a vertical direction by means of hydraulic cylinders 48. Power tongs 50 and other equipment, not shown, for pulling pipes and dividing well pipes 28 are located at the pipe-puller 26.

The arm 30, which is rotated by means of hydraulic cylinders 51 , is provided with a pair of preferably rotatable pipe-grippers 52. The pipe-grippers 52 are displaceable along a rail 54 which is fixedly connected to the arm 30. The pipe-grippers 52 are preferably hydraulically operated. The pipe- grippers 52 with displacing equipment are known to a person skilled in the art.

When a well pipe 28 is to be pulled, the arm 30 is rotated around the hinge axis 32 into a mainly vertical position, as is shown in figure 7. The feeding device 38 has been moved away from the well centre 18.

The grippers 46 of the pipe-puller 26 grip around the well pipe 28, whereupon the hydraulic cylinders 48 lift the grippers 46 in the direction out of the petroleum well 1 6. The pulling operation is repeated until a pipe joint, not shown, is above the pipe-puller 26. After the grippers 52 of the arm 30 have gripped around the well pipe 28, the power tongs 50 are used to break out and divide the pipe joint not shown. If this cannot be done, the well pipe 28 will have to be cut. During cutting, the arm 30 holds the well pipe 28 in tension at the pipe joint, not shown, so that a cutting tool (not shown) will not be damaged during the cutting operation. When a pipe portion 56 of the well pipe 28 has been loosened from the rest of the well pipe 28, the pipe portion 56 is lifted up somewhat from the rest of the well pipe 28, whereupon the arm 30 is rotated around the hinge axis 32 until the pipe portion 56 of the well pipe 28 lies substantially horizontally at the pipe rack 34, as is shown in figure 8.

The crane 10 may be used for holding equipment for a simultaneous operation at a different wellhead 18 than the wellhead 18 at which the feeding device 38 is in operation. Accordingly, the crane 10 improves the flexibility of operation at the device 3. Alternatively, the crane 10 may be used for holding and positioning the feeding device 38 for the coiled tubing or the wireline at the wellhead 18 of the petroleum well 16, for example by means of a linear displacement to and from the wellhead 18. The crane 1 0 is for example an overhead crane, a rail crane and etcetera.

Pipe-pulling operations by means of the cantilever 12 with associated components are carried out substantially without the help of the crane 1 0 which may thereby be used simultaneously for other tasks.

By the very fact of the cantilever 12 being provided with the feeding device 38 and the coiled-tubing drum 42, coiled-tubing operations, see figure 5, may be carried out in a safe and relatively simple and, per se, known manner without the use of the crane 10 being required.

Figure 9 shows a self-elevating vessel 1 which is placed at a subsea petroleum well 1 6 which has its wellhead 17 with a wellhead valve at the seabed 24. The cantilever 12 of the self-elevating vessel 1 is designed, in the main, to be able to perform operations corresponding to those described above on subsea petroleum wells 16 as well.

The positioning of the operator cabin 44 behind the coiled-tubing drum 42 or wireline drum 43 enables an operator (not shown) in the operator cabin 44 to see along the coiled tubing 40 or the wireline 41 .

The person skilled in the art will understand that the arm 30 may be used in more connections than the embodiment shown, in which the arm 30 is placed on a cantilever 12. The arm 30 may also be used at petroleum wells 16 onshore and at petroleum wells 16 on fixed installations offshore.

A self-elevating vessel 1 , and especially a liftboat provided with a crane 10 and a cantilever 12 as described, could perform light well intervention in a particularly efficient manner. This is especially true within jurisdictions that permit the feeding device 38 to be hung from a crane 10. The feeding device 38 hanging from the crane 10 may perform well intervention in one petroleum well 16 while the feeding device 38 on the cantilever 12 is simultaneously performing well intervention on a neighbouring petroleum well 16. Correspondingly, well intervention may be performed by means of the crane 10 as described, while plugging and abandoning of another petroleum well 16 is performed simultaneously from the cantilever 12. Well intervention may also be performed from the cantilever 12 while the crane 10 is simultaneously engaged in plugging and abandoning another petroleum well 16. In relation to a jack-up, the use of a liftboat 1 also has the advantage of being brought more quickly into a working position at a wellhead platform.

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.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.