GB2578355A

GB2578355A - An apparatus and method for removing an end section of a tubular member

Info

Publication number: GB2578355A
Application number: GB1911579.9A
Authority: GB
Inventors: Richard Thomson Craig; Campbell-Smith Greg; Davidson Jack
Original assignee: James Fisher Offshore Ltd; First Subsea Ltd
Current assignee: James Fisher Offshore Ltd; First Subsea Ltd
Priority date: 2018-08-14
Filing date: 2019-08-13
Publication date: 2020-05-06
Anticipated expiration: 2039-08-13
Also published as: GB2578355B; WO2020035678A1; GB201911579D0; GB201813270D0; GB202102008D0; GB2590832A

Abstract

An apparatus for removing an end section of a tubular member, comprising: clamp means 14 configured to be releasably securable to the end section of a tubular member 10 to be removed with tubular member cutting means 18 located below the clamp means; and means for positioning the clamp means in a clamping position with respect to the 10 section of the tubular member to be removed and for removing a severed clamped end section of the tubular member. A method for cutting and removing the end of a tubular is also claimed. The cutting means may be a water-abrasive cutting, the clamp means may be balls and there may be further suspension means.

Description

An Apparatus and Method for Removing an End Section of a Tubular Member The present invention relates to an apparatus and a method for removing an end section of a tubular member and in particular, but not exclusively, for removing an end section of a "conductor" which forms part of an offshore oil or gas platform.

In offshore oil and gas installations, a "conductor" is a large diameter vertical tubular member that is set into the seabed to provide an initial stable structural foundation, and in which the well flowlines are located. Typically, several vertical conductors are provided.

When an oil or gas platform is at the end of its useful life, it is desirable to decommission it. This requires dismantling of the platform, which involves removal of the conductors amongst other items. Indeed, it is often necessary to disconnect the conductors from the superstructure of the platform to allow the superstructure to be removed as a discrete unit.

The current method of removing a conductor comprises lowering a cutting device into the conductor, cutting through the wall of the conductor, removing the cutting device from within the conductor, securing a clamp to the severed end portion and then lifting the clamped severed end portion by means of the clamp away from the remainder of the conductor.

The current method is time-consuming, and therefore expensive, since the cutting and lifting operations are separate, and in particular it is necessary to ensure that the cutting device is removed from the conductor after it has cut through the wall of the conductor, before the clamp can be engaged with the end of the severed portion of the conductor in order for the severed portion to be taken away.

In accordance with a first aspect of the present invention, an apparatus for removing an end section of a tubular member comprises: clamp means configured to be releasably securable to the end section of the tubular 30 member to be removed; tubular member cutting means located below the clamp means; and means for positioning the clamp means in a clamping position with respect to the section of the pipe to be removed and for removing a severed clamped end section of the tubular member.

By having clamp means in combination with tubular member cutting means, once the tubular member cutting means has cut through the conductor, the severed end portion of the tubular member can be lifted away from the remainder of the conductor with the clamp means and tubular member cutting means in situ. The severed end portion can then be taken to a desired location, at which point the clamp means and cutting means can be disengaged from the severed end of the conductor. In this way, the severed end of the conductor can be removed immediately after the wall of the conductor has been cut through, without the need for removing the cutting means. This reduces the number of steps required to remove an end section of the conductor, thereby reducing the time and cost of the procedure.

In a preferred embodiment, the positions of the clamp means and the tubular member cutting means within the tubular member to be removed can be determined independently of each other.

This allows the clamp means to be secured to the upper end of the conductor and allows the cutting means to be lowered to the desired cutting position. This allows much greater lengths of conductor to be severed and removed because by securing the clamp means to the upper end of the section to be removed, the centre of gravity of the removed section will always be below the clamp means.

The apparatus preferably further comprises first means for suspending the clamp means.

The apparatus preferably further comprises second means for suspending the tubular member cutting means.

The second means may conveniently pass through the clamp means.

Preferably, the second means comprises an umbilical.

Preferably, the clamp means are configured to be releasably securable to the interior of the end section of the tubular member to be removed.

The clamp means may comprise a plurality of members reversibly displaceable outwardly into engagement with the interior of the section of tubular member to be removed.

For example, the clamp means may comprise a plurality of balls reversibly displaceable outwardly into engagement with the interior of the section of the tubular member to be removed.

Preferably, the tubular member cutting means are configured to cut the tubular member outwardly from the interior of the tubular member.

In one embodiment, the tubular member cutting means comprises means for generating a high-pressure jet of liquid.

The tubular member cutting means may comprise a water-abrasive cutting system.

In one embodiment, the cutting means is suspended from the clamp means.

An underwater umbilical may be connected to the cutting means.

In accordance with a second aspect of the present invention, a method of removing an end section of a tubular member, comprises: clamping onto the end section of the portion of the tubular member to be removed; cutting through the wall of the tubular member at a location on the tubular member longitudinally inwardly of the clamping location; and removing the severed section of the tubular member while the section is still clamped.

In a preferred embodiment, the method comprises: lowering a tubular member cutting means and a clamp means into the end section of the portion of the tubular member to be removed; clamping the clamp means onto the end section of the portion of the tubular member to be removed; further lowering the tubular member cutting means into a cutting position within the tubular member; cutting through the wall of the tubular member at the cutting position; lifting the clamp means to remove the severed portion of the tubular member.

Preferably, the tubular member cutting means engages the tubular member after being lowered to the cutting position.

Preferably, the tubular member cutting means is withdrawn from the cutting position prior to the clamp means being lifted to remove the severed portion of the tubular member.

Preferably, the clamp means is clamped onto an upper end of the end section of the portion of the tubular member to be removed.

The method may comprise clamping onto the interior of the end section of the portion of the tubular member to be removed.

The method may comprise cutting through the wall of the tubular member outwardly from the interior of the tubular member.

The method may comprise cutting through the wall of the tubular member by means of a high-pressure jet of liquid and, for example, may comprise cutting through the wall of the tubular member with a water-abrasive cutting system.

The method may comprise suspending the clamp means.

By way of example only, specific embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of a first embodiment of apparatus for cutting and removing a section of vertical tubular member, in accordance with the present invention, and the steps involved for cutting and removing a section of vertical tubular member, in accordance with the present invention; Figures 2 to 6 are vertical cross-sections through a first embodiment of apparatus for cutting and removing a section of the cemented liner in accordance with the present invention, and showing the steps involved in removing a section of vertical tubular member, in accordance with the present invention; Figure 7 is a perspective view of a cutting head which forms part of the apparatus of Figures 2 to 6, shown in retractors and deployed configurations; and Figures 8(a) to 8(f) of vertical cross-sections through a second embodiment of apparatus for cutting and removing a section of cemented liner in accordance with the present invention, and showing the steps involved in removing a section of a vertical tubular member, in accordance with the present invention.

Figure 1 is a schematic illustration of the uppermost portion of a vertical subsea conductor 10 formed from a metal tubular member 11 with a cemented liner 12, the lower end (not shown) of the conductor being secured into the sea bed (not shown) and whose upper end is typically secured to an oil or gas platform. Typically, the conductor tubular member 11 will have an external diameter of around 30 inches (76.2 cm) with a wall thickness of around 1 inch (2.54 cm), but the thicknesses of the tubular member 11 and the liner 12 have been exaggerated in the drawings, for purposes of clarity. An oil or gas platform is typically mounted on the upper end of an array of vertical conductors 10 and when the oil or gas platform is at the end of its useful life, it is desirable to decommission it, which involves removal of the conductors 10 amongst other items.

As shown schematically in Figure 1, the apparatus of the first embodiment of the present invention comprises a clamp 14 which is suspended at its proximal end from an umbilical 16 which includes a suspension cable, electrical cables and hydraulic hoses. A cutting head 18 is suspended from the lower (distal) end of the clamp 14 by means of a further umbilical 20 which also includes a suspension cable, electrical cables and hydraulic hoses.

As shown in Figure 1(a), the apparatus is lowered into a section of tubular member to be removed. When the cutting head has reached the cutting location, the clamp 14 is releasably secured to the conductor 10 (shown schematically at 15) and the cutting head is actuated to cut through the conductor, as shown in Figure 1(b). When the cutting head has cut completely through the conductor 10, the apparatus is withdrawn upwardly by means of the upper umbilical 18, thereby withdrawing the severed section of the conductor 10, to which the apparatus is still secured, from the remainder of the conductor 10', as shown in Figure 1(c).

A specific embodiment of apparatus in accordance with the invention is shown in Figure 2. In this embodiment, the clamp 14 comprises a known internal clamp for tubular members, such as that described in Figure 4 of EP0156575A. The clamp 14 comprises a cylindrical body 22 having a plurality of rows of identical tapered circular apertures 24, each of which receives a respective identical cylindrical ball 26. The balls 26 are sized so that they can project partially out of their apertures 24 beyond the outer cylindrical surface of the cylindrical body 22, but so that they cannot pass completely through the apertures 24.

A mandrel (not shown) within the cylindrical body is provided with a series of ramped surfaces, and is displaceable along the longitudinal axis of the cylindrical body between a first position in which engagement of the ramped surfaces with the cylindrical balls 26 forces the balls radially outwardly into a first, clamping position in which they project beyond the outer cylindrical face of the cylindrical body 22 and a second, non-clamping position in which the balls are not forced radially outwardly.

By choosing the outer diameter of the cylindrical body 22 to be slightly smaller than the internal diameter of the conductor 10 and its liner 12, the clamp can be lowered into the conductor and can then be clamped in position by displacing the cylindrical balls 26 radially outwardly into engagement with the internal surface of the conductor 10.

In the specific embodiment shown, the cutting head 18 comprises a known water-abrasive cutting system manufactured by ANT Applied in New Technologies AG of the type disclosed in US2018/00212922A1. The cutting head 18 comprises an upper portion 28 having three identical, equally angularly spaced contact elements 30, and a nozzle head 32 rotatably mounted at the lower end of the upper portion 28.

The contact elements are movable between a first, withdrawn position illustrated in Figure 2 in which, in use, they do not engage the interior surface of the conductor 10, and a second, deployed position shown in Figures 3 and 5 in which they engage the interior surface of the conductor 10. The cutting head 18 also preferably comprises a number of sensors such as acceleration sensor (not shown) on each of the contact elements 30 and a hydrophone (also not shown) on the nozzle head 32. Signals from the sensors are used to determine whether the whole of the tubular member has been severed around the whole of its periphery, as described in the prior art.

The nozzle head 32 is rotatable with respect to the upper portion 28 by means of a motor (not shown) and has an outlet 34 from which a narrow jet 36 of extremely high-pressure water, to which an abrasive agent is added, is discharged, in a known manner. Consequently, as the nozzle head 32 is rotated, the high-pressure jet 36 cuts through the wall of the conductor 10 and its liner 12 around the whole of its periphery, as shown in Figures 3, 4 and 5.

In use, the clamp 14 is adjusted into its position in which the balls 26 are not forced radially outwardly and the contact elements 30 of the cutting head 18 are moved to their first, withdrawn position. The apparatus is then lowered into a section of conductor 10 to be removed, as shown in Figure 2.

When the nozzle head 32 has reached the desired cutting location (corresponding to a typical cut length of around 10 metres), the clamp 14 is actuated so that the balls 26 are displaced radially outwardly into contact with the inner surface of the conductor 10, thereby securing the clamp 14 in position within the conductor 10. The contact elements 30 of the upper portion 28 of the cutting head 18 are also displaced outwardly into the deployed position in engagement with the inner surface of the conductor 10.

The nozzle head 32 of the cutting head 18 is thereby secured in position with respect to the conductor 10. High-pressure water containing abrasive elements is then fed to the nozzle head 32 via the umbilicals 16, 20. In this way, a narrow jet 36 of extremely high-pressure fluid containing abrasive elements is emitted from the outlet 34, and as the nozzle head 32 is rotated the jet 36 cuts the conductor 10 around the whole of its periphery, as shown in Figures 3, 4 and 5.

When the conductor 10 has), the contact elements 30 of the upper portion 28 of the cutting head 18 withdraw inwardly so that they no longer contact the inner face of the conductor 10.

The clamp 14 is still engaged with the inner face of the conductor 10 and the severed section of conductor 10 can then be withdrawn from the remaining section 10' of conductor by pulling up the upper umbilical 16.

When the severed portion of conductor 10 has been withdrawn to the desired location, the clamp 14 can be deactuated, whereby the balls 26 of the clamp 14 are no longer forced into engagement with the inner surface of the conductor 10, thereby allowing the clamp 14 and the cutting head 18 to be withdrawn from the severed section of umbilical 10 by means of the umbilical 16.

The process can then be repeated with further sections of the conductor 10.

A second embodiment of the present invention is shown in Figures 7(a) to 7(b). The apparatus of Figure 7 is very similar to that of Figures 2 6, the main difference being that the position of the clamp and the position of the cutting head can be determined independently of one another, as will be explained.

As shown in Figures 7(a) to 7(b), the apparatus of the second embodiment of the present invention comprises a clamp 110 which is suspended by means of cables 112 from the hook of a winch 114. A cutting head 118, identical to the cutting head 18 of the first embodiment is located below the lower end of the clamp 110 and is suspended from an umbilical 120 which is fed from an umbilical winch 122 and passes over a guide 124. The umbilical includes a suspension cable, electrical cables and hydraulic hoses and passes through an elongated passageway (not shown) passing through a mandrel of the clamp 110 (see below) along its longitudinal axis.

As for the first embodiment, the clamp 110 comprises a known internal clamp tubular members, such as that described in Figure 4 of EP0156575A. The clamp 110 comprises a cylindrical body 130 having a variety of sectors of identical spherical balls 132 each located in a respective aperture. The balls 132 sized so that they can project partially out of their respective aperture is blood so that they cannot pass completely through them.

A mandrel (not shown) within the cylindrical body is provided with a series of ramped surfaces, and is disposable along the longitudinal axis of the cylindrical body between a first position in which engagement of the ramped surfaces with the cylindrical balls forces the balls were radially outwardly into a first, clamping position in which they project beyond the outer cylindrical face of the cylindrical body 130 and a second, non-clamping position in which the balls are not forced radially outwardly.

By choosing the outer diameter of the cylindrical body 130 to be slightly smaller than the diameter of the pipe 112 to be severed, the clamp can be lowered into the pipe and can then be clamped in position by displacing the cylindrical balls 132 radially outwardly into engagement with the internal surface of the pipe 112.

As explained previously, the mandrel of the clamp 110 is provided with an elongated passageway extending along its longitudinal axis through which the umbilical 120 from which the cutting head 118 is suspended passes.

In contrast to the first embodiment, the cutting head 118 is not suspended from the clamp 110 and instead the position of the clamp 110 and position of the cutting head 118 can be determined independently of one another.

In use, the clamp 110 is adjusted into its position in which the balls 132 are not forced radially outwardly and the contact elements 30 of the cutting head 118 are moved to the first, withdrawn position as illustrated in Figure 8(a). The cutting head 118 and the clamp 110 are then lowered into a section of pipe 112 to be removed, as shown in Figure 8(a). The winch 114 from which the clamp 110 is suspended and the umbilical winch 122 from which the cutting head 118 is suspended are synchronised so that the clamp 110 and the cutting head 118 are lowered simultaneously into the pipe 112.

When the clamp 110 is located at the upper end of the section of pipe to be removed, the winch 114 and the umbilical winch 122 are stopped and the clamp 110 is actuated so that the balls 132 displaced radially outwardly into contact with the inner surface of the pipe 112, thereby securing the clamp 110 in position at the top of the pipe section 112, as illustrated in Figure 8(b).

With the clamp 110 secured in position at the top of the pipe section 112, the umbilical winch 122 is actuated further to lower the cutting head 118 to the desired cutting location, as shown in Figure 8(c) (corresponding to a typical cut length of several tens of metres, up to 150 metres). When the cutting head 118 is in this position, the contact elements 30 of the upper portion 28 of the cutting head 118 or also displaced outwardly into the deployed position (as shown in Figure 8(b)). The nozzle head 32 of the cutting head 118 is thereby secured in position with respect to the pipe section 112. As for the first embodiment, high-pressure water containing abrasive elements is then fed to the nozzle head 32 via the umbilical 120. In this way a narrow jet 36 of extremely high-pressure fluid containing abrasive elements is emitted from the outlet 34, and as the nozzle head 32 is rotated the jet 36 cuts the conductor around the whole of its periphery, as shown in Figure 8(d).

When the section of pipe 112 has been severed around the whole of its periphery at the cutting location (as confirmed by the on-board sensors -not shown) the contact elements 30 of the upper portion 28 of the cutting head 118 are withdrawn inwardly so that they no longer contact the inner face of the pipe 112. The clamp 110 is still engaged with the inner face of the upper end of the pipe 112 and the umbilical winch 122 is actuated to withdraw the cutting head 118 upwardly into a so-called "docked" position immediately below the lower end of the clamp of 110, as shown in Figure 8(e).

The winch 114 can then be actuated to lift the severed section of pipe 112 away from the unsevered portion 112a, as shown in Figure 8(f). When operating the winch 114 to lift the severed section of pipe 112, the umbilical winch 122 is also actuated synchronously to retain the cutting head 118 in its "docked" position, as the position of the cutting head 118 within the pipe 112 is controlled independently of the position of the clamp 110.

When the severed section of pipe 112 has been moved to a desired location, the clamp 110 can be actuated to withdraw the balls 132 out of engagement with the inner surface of the pipe 112, allowing the clamp 110 and the cutting head 118 to be withdrawn from the severed portion of the pipe 112a.

The invention is not restricted to the details of the foregoing embodiments.

For example, the clamp 10, 110 as described is an internal clamp which engages with the inner surface of the conductor 12, 112. However, whilst this is convenient, a clamp which engages with the exterior surface of the tubular member may be used instead.

Similarly, the cutting head may be configured to cut the conductor from the outer surface inwardly.

In addition, whilst the cutting head 18, 118 has been described as being a water-abrasive cutting system which produces a high-pressure jet of water and abrasive agent, other cutting heads may be used instead, for example a mechanical cutting blade or a laser.

Moreover, although the connection between the clamp 14, 110 and the cutting head 18, 118 has been described as being flexible, a rigid connection may be used instead.

For the first embodiment, it is possible for the clamp and the cutting head to be combined into a single unit, with the cutting head mounted directly at the lower end of the clamp.

Finally, although the specific embodiments described above relate to the removal of an end section of a conductor forming part of an oil or gas platform, the present invention is equally applicable to the removal of an end section of other types of tubular members, whether arranged vertically or in some other orientation.

Claims

CLAIMSAn apparatus for removing an end section of a tubular member, comprising: clamp means configured to be releasably securable to the end section of the tubular member to be removed; tubular member cutting means located below the clamp means; and means for positioning the clamp means in a clamping position with respect to the section of the tubular member to be removed and for removing a severed clamped end section of the tubular member.
2. An apparatus as claimed in claim 1, wherein the positions of the clamp means and the tubular member cutting means within the tubular member to be removed can be determined independently of each other.
3. An apparatus as claimed in claim 2, comprising first means for suspending the clamp means.
4. An apparatus as claimed in claim 3, comprising second means for suspending the tubular member cutting means.
5. An apparatus as claimed in claim 4, wherein the second means passes through the clamp means.
6. An apparatus as claimed in claim 4 or claim 5, wherein the second means comprises an umbilical.
7. An apparatus is claimed in any of the preceding claims, wherein the clamp means are configured to be releasably securable to the interior of the end section of the tubular member to be removed.
8. An apparatus as claimed in any of the preceding claims, wherein the clamp means comprises a plurality of members reversibly displaceable outwardly into engagement with the interior of the section of tubular member to be removed.
9. An apparatus as claimed in claim 8, wherein the clamp means comprises a plurality of balls reversibly displaceable outwardly into engagement with the interior of the section of the tubular member to be removed.
10. An apparatus as claimed in any of the preceding claims, wherein the tubular member cutting means are configured to cut the tubular member outwardly from the interior of the tubular member.
11. An apparatus as claimed in any of the preceding claims, wherein the tubular member cutting means comprises means for generating a high-pressure jet of liquid.
12. An apparatus as claimed in claim 11, wherein the tubular member cutting means comprises a water-abrasive cutting system.
13. Apparatus as claimed in claim 1 or claim 2, wherein the cutting means is suspended from the clamp means.
14. A method of removing an end section of a tubular member, comprising: clamping onto the end section of the portion of the tubular member to be removed; cutting through the wall of the tubular member at a location on the tubular member longitudinally inwardly of the clamping location; and removing the severed section of the tubular member while the section is still clamped.
15. A method as claimed in claim 14, comprising: lowering a tubular member cutting means and a clamp means into the end section of the portion of the tubular member to be removed; clamping the clamp means onto the end section of the portion of the tubular member to be removed; further lowering the tubular member cutting means into a cutting position within the tubular member; cutting through the wall of the tubular member at the cutting position; lifting the clamp means to remove the severed portion of the tubular member.
16. A method as claimed in claim 15, wherein the clamp means is clamped onto an upper end of the end section of the portion of the tubular member to be removed
17. A method as claimed in claim 16, wherein the tubular member cutting means engages the tubular member after being lowered to the cutting position.
18. A method as claimed in any of claims 15 to 17, wherein the tubular member cutting means is withdrawn from the cutting position prior to the clamp means being lifted to remove the severed portion of the tubular member.
19. A method as claimed in any of claims 14 to 18, comprising clamping onto the interior of the end section of the portion of the tubular member to be removed.
20. A method as claimed in any of claims 14 to 19, comprising cutting through the wall of the tubular member outwardly from the interior of the tubular member.
21. A method as claimed in any of claims 14 to 20, comprising cutting through the wall of the tubular member by means of a high-pressure jet of liquid.
22. A method as claimed in claim 21, comprising cutting through the wall of the tubular member with a water-abrasive cutting system.
23. A method as claimed in any of claims 14 to 22, comprising suspending the clamp means and the tubular member cutting means.