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Title:
SUBSEA SEVERING OF STRINGER CASINGS
Document Type and Number:
WIPO Patent Application WO/2010/065994
Kind Code:
A1
Abstract:
A well casing severing apparatus and method provides a cutting tool (7) in a tool holder (9) arranged to rotate and radially advance (pneumatically or hydraulically driven) to cut through the side wall of the tubing (8). The cutting tool can be released to pivot or hinge (10) from an operative position to a release position to permit extraction of the tool.

Inventors:
JONES, Robert, William (6 Aspera Close, Canning Vale, Western Australia 6155, AU)
WALKER, Brett, Mitchell (2/20 Ednah Street, Como, Western Australia 6152, AU)
BURNS, Alexander, Jeffrey (16 Woolley Street, Willetton, Western Australia 6155, AU)
Application Number:
AU2009/001593
Publication Date:
June 17, 2010
Filing Date:
December 08, 2009
Export Citation:
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Assignee:
WELL OPS SEA PTY LTD (32 Poletti Road, Cockburn Central, Western Australia 6164, AU)
JONES, Robert, William (6 Aspera Close, Canning Vale, Western Australia 6155, AU)
WALKER, Brett, Mitchell (2/20 Ednah Street, Como, Western Australia 6152, AU)
BURNS, Alexander, Jeffrey (16 Woolley Street, Willetton, Western Australia 6155, AU)
International Classes:
E21B29/00; B23D21/14
Attorney, Agent or Firm:
WATERMARK PATENT AND TRADE MARK ATTORNEYS (Level 2, 302 Burwood RoadHawthorn, Victoria 3122, AU)
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Claims:
CLAIMS:

1. A well casing severing apparatus, the well casing having a side wall, the apparatus including a cutting body supporting a rotational cutting head, the rotational cutting head including a cutting tool to cut through the side wall, a cutting tool rotation mechanism arranged to rotate the cutting tool to define a circle concentric with respect to the side wall, and a cutting tool advance mechanism arranged to advance the cutting tool radially with respect to the side wall, the apparatus, in use, arranged to simultaneously rotate and advance the parting tool to cut a ring through the casing side wall to severe the casing.

2. An apparatus according to claim 1 , including a clamping mechanism to hold the body of the apparatus in place against an interior surface of the side wall of the casing that is being cut.

3. An apparatus according to claim 2, wherein the clamping mechanism includes one or more inflatable bags carried by the body, whereby, in use, the one or more bags are inflated and thereby press directly against the interior side wall of the casing or inflate to press on or more clamps against the side wall.

4. An apparatus according to claim 2 or 3, wherein the clamping mechanism includes at least one hydraulically or pneumatically driven wedge and a hydraulic/pneumatic drive/feed that moves the wedge(s) which thereby force the clamp(s) outwardly within the casing causing the clamp(s) to press against the interior surface of the casing to prevent relative movement between the body of the tool and the casing side wall.

5. An apparatus according to claim 4, wherein the at least one self release clamping wedge arranged such that when a hydraulic/pneumatic force is removed from the wedge(s) and the tool is lifted upwardly out of the casing, the wedge(s) self release(s) from the movable clamps thus allowing the clamps the contract inwardly.

6. An apparatus according to claim 2, wherein the clamping mechanism includes at least one mechanical clamp actuator.

7. An apparatus according to claim 6, wherein the at least one mechanical clamp actuator includes an over centre toggle that is self-locking when hydraulically/pneumatically actuated.

8. An apparatus according to claim 6 or 7, wherein the clamping mechanism is released by hydraulic/pneumatic actuation or high force pull.

9. An apparatus according to any one of the preceding claims, wherein the cutting tool is configured to fracture when the apparatus is withdrawn upwards out of the casing.

10. An apparatus according to any one of the preceding claims, wherein the cutting tool is retained in a tool holder, and a release mechanism is provided that releases the cutting tool or tool holder to a release position for withdrawal of the body upwards out of the casing.

1 1 . An apparatus according to claim 10, wherein the tool or tool holder is retained in an operative cutting position by one or more retaining means applying a retaining force such as a clamping force.

12. An apparatus according to claim 1 1 , wherein the retaining means includes one or more bolts or pins providing a clamping force as the retaining force.

13. An apparatus according to any one of claims 10 to 12, wherein the retaining means includes one or more bolts or pins with respective shear portions such that sufficient shear force applied to the one or more bolts or pins fractures the bolt(s)/pin(s) to release the tool/tool holder.

14. An apparatus according to any one of the preceding claims, wherein the rotational and/or advance mechanism is hydraulically or pneumatically powered.

15. An apparatus according to any one of the preceding claims, including vibration detection system arranged to detect cutting progress and/or when the cutting tool has completely cut through the casing.

16. An apparatus according to claim 15, wherein the vibration detection system includes a microphone to receive vibrational noise.

17. An apparatus according to claim 15 or 16, including vibration differentiation means to detect changes in vibrations and differentiate between various frequencies and/or amplitudes of vibration that there are present in the casing/tool itself and/or are present in the space surrounding the cutting tool.

18. A method of severing a subsea casing having a side wall, including; a) inserting a cutting body into a bore of a casing. b) positioning the cutting body at a desired position. c) rotating a cutting tool within the bore. d) advancing the cutting tool during said rotation. e) the cutting tool cutting a ring through the side wall by the rotational movement and the advancing movement to cut completely through the side wall and severe the casing into upper and lower portions.

19. A method according to claim 18, including clamping the body against the interior side wall of the casing to provide a substantially stable cutting position.

20. A method according to claim 18 or 19, including releasing clamping of the body from the side wall prior to withdrawal of the body from the severed casing.

21 . A method according to any one of claims 18 to 20, including detecting when the casing wall has been completely cut through.

22. A method according to claim 21 , wherein said detecting includes detecting a change in vibrational information between cutting and complete severing.

23. A method according to claim 22, wherein the change in vibrational information includes detecting a change in vibration amplitude and/or frequency.

24. A method according to any one of claims 18 to 23, wherein clamping is actuated by a mechanism or system independent of cutting drive.

25. A method according to any one of claims 18 to 24, wherein clamping release is actuated by a mechanism or system independent of cutting drive.

26. A method according to claim 24 or 25, wherein the mechanism or system includes at least one mechanically actuated clamp.

27. A method according to any one of claims 18 to 26, including pivoting or hinging a retained end of the cutting tool to a release position to allow the tool body to be extracted from the subsea casing.

28. A method according to claim 27, whereby upward movement of the tool body causes at least a portion of the cutting tool to be released from a retaining means.

29. A method according to claim 28, whereby release of the retaining means is by overcoming a frictional, interference or clamping force on the cutting tool or cutting tool holder.

30. A method according to claim 28 or 29, whereby release of the retaining means is achieved by shearing or fracture of one or more fasteners such as pins or bolts.

Description:
SUBSEA SEVERING OF STRINGER CASINGS TECHNICAL FIELD

The present invention relates to severing of subsea stringer casings. BACKGROUND

It is often necessary to remove part of a casing within a casing string of a subsea oil or gas well and, in many cases, where the desired cut level is below the seabed. For example, an upper section of a casing may require removal as part of a well decommissioning procedure, and severing of the upper section needs to be carried out below the seabed so that none of the upper section remains exposed on the seabed.

One known method of severing the casing is to blast the steel casing apart into two portions using an explosive charge.

However, if an insufficient amount of explosive is used in this operation, then complete severance of the casing may not occur and, consequently, in order to ensure complete severance of the casing operators tend to use more explosive than necessary.

Whilst using more explosive than necessary ensures complete severance, the remainder of the casing string can be damaged by the excessive blast.

Another disadvantage of using an explosive severing technique is that it can cause damage to the surrounding marine life and environment, and as such, is an environmentally unfriendly method.

With this in mind, it has been found desirable to provide an apparatus and method for improved subsea cutting of well casings that alleviates or avoids such problems. SUMMARY OF THE INVENTION

With the aforementioned in view, one form of the present invention provides a well casing severing apparatus, the well casing having a side wall, the apparatus including a cutting body supporting a rotational cutting head, the rotational cutting head including a cutting tool to cut through the side wall, a cutting tool rotation mechanism arranged to rotate the cutting tool to define a circle concentric with respect to the side wall, and a cutting tool advance mechanism arranged to advance the cutting tool radially with respect to the side wall, the apparatus, in use, arranged to simultaneously rotate and advance the parting tool to cut a ring through the casing side wall to severe the casing.

Thus, the apparatus does not require destructive explosives to separate the casing. There are added benefits to the present invention in that explosives typically need to be set off in daylight. The major reason for such daylight working is that a "Mammal Watch" has to be in place to ensure that no vulnerable marine wildlife (whales, dolphins etc) are in the blast vicinity. Without the need for explosives, the present invention can be utilised any time of day, thereby potentially decreasing time and associated costs (man hours, machinery hire, lost time on other projects etc) required to complete an operation.

It will be appreciated that an apparatus according to the present invention may be deployed from a vessel or rig, making it relatively quick and easy to employ.

One or more forms of the present invention may be hydraulically and/or pneumatically powered, which enhances safety and operational practicality over explosives and potentially electrically powered apparatus.

The apparatus may include a clamping mechanism to hold a body of the apparatus firmly against an interior surface of the side wall of the casing that is being cut to prevent either rotational or vertical movement of the body relative to the casing during the cutting procedure. This provides a rigid, centralised position within the bore of the casing from which to effect reliable cutting. Maintaining a centralised position, with no substantial change in position of the apparatus, means that a reliable and consistent depth of cut through the side wall can be achieved, thereby improving accuracy of cut.

The clamping mechanism may include one or more inflatable bags carried by the body, whereby, in use, the one or more bags may be inflated and thereby press directly against the interior side wall (lumen) of the casing, or inflate to press on or more clamps against the side wall, to hold the body in a desired position. It will be appreciated that the body may include a bag(s) inflation apparatus, or remote inflation means may be provided, such as an air or hydraulic feed to the bag(s). Deflation means may be provided to deflate the bag(s) prior to withdrawing the cutting tool or for repositioning the tool.

Alternatively or in addition, the clamping mechanism may include at least one hydraulically or pneumatically driven wedge and a hydraulic/pneumatic drive/feed that moves the wedge(s) which thereby force the clamp(s) outwardly within the casing causing the clamp(s) to press against the lumen surface of the casing to prevent relative movement between the fixed part of the tool (body of the tool) and the casing side wall. The at least one wedge may be arranged such that when a hydraulic/pneumatic force is removed from the wedge(s) and the tool is lifted upwardly out of the casing, the wedge(s) self release(s) from the movable clamps thus allowing the clamps the contract inwardly.

The apparatus may be connected to a suspension line attached to a vessel or other structure and then lowered into the casing that requires a portion of the casing to be removed.

The cutting tool may include a single point cutting tool (which may remain in a radially extended (advanced) position on completion of cut) or multi point cutting tool, and the cutting tool (whether single or multi point tool) may be configured to fracture when the whole apparatus is withdrawn upwards out of the casing, thus enabling the apparatus to be withdrawn from the casing without the necessity of having to retract the cutting tool. Alternatively or in addition, multiple tool holders may be employed, with either a single or multiple cutting tool. For the purposes of this specification, the term "cutting tool" refers to single and/or multiple cutting tools.

The cutting tool may be retained in a tool holder, and a release mechanism may be provided that releases the cutting tool to a release position for more effective withdrawal of the body upwards out of the casing.

The rotational and/or advance mechanism may be hydraulically or pneumatically powered.

Alternatively, mechanically operated clamps may be actuated hydraulically or pneumatically but which remain in a clamped (extended) position even if the hydraulic supply is disconnected. This arrangement may require that the either the hydraulic/pneumatic supply is reconnected to enable the clamps to be released, or alternatively, pulling the body upwards out of the casing causes the clamps to be automatically released via an auto release mechanism. Other possible clamping device(s) could include either hydraulically or air operated (rubber) packers.

A clamping mechanism may be provided to clamp the body into position within the casing bore. The clamping mechanism may include at least one mechanical clamp actuator. The at least one mechanical clamp actuator may include an over centre toggle that is self-locking, such as when hydraulically/pneumatically actuated. The clamping mechanism may be released by hydraulic/pneumatic actuation or high force pull.

The apparatus may include a vibration detection system to determine when the cutting tool has completely cut through the casing. This may include vibration differentiation means which detects changes in vibrations and differentiates between various frequencies and/or amplitudes of vibration that there are present in the casing/tool itself and/or are present in the space surrounding the cutting tool. Such a vibration detection system may include a sound microphone to capture the sounds in the area surrounding the cutting tool and output a signal (such as an audio and/or visual signal) that may be further analysed/interpreted to indicate the completion of the cutting procedure or that the rate of cutting may be varied (eg slowed) as cutting nears completion.

Rotational speed and/or rate of advance of the cutting tool may be varied together or independently. For example, rate of radial advance of the tool may be linked to rotational speed or number of revolutions such that a predictable amount of advance may be achieved. This may be by a worm drive linkage that increments advance of the cutting tool into the steel casing dependent upon number of revolutions of the cutting head or rotational speed. Alternatively, rotational speed and radial advance of the cutting tool may be independently controlled.

Another form of the present invention provides a method of severing a subsea stringer casing having a side wall, including; a) inserting a cutting body into a bore of a casing. b) positioning the cutting body at a desired position. c) rotating a cutting tool within the bore. d) advancing the cutting tool during rotation. e) the cutting tool cutting a ring through the side wall by rotational movement and advancing movement to cut completely through the side wall to severe the casing into upper and lower portions.

The method may include clamping the body against the interior side wall (lumen) of the casing to provide a substantially stable cutting position, preferably centralised within the bore. Clamping may be released prior to withdrawal of the body from the severed casing.

Clamping may be actuated by a mechanism or system independent of cutting drive. Clamping release may be actuated by a mechanism or system independent of cutting drive. The mechanism or system for clamping and/or release may include at least one mechanically actuated clamp. A high pull force release may be utilised.

Pivoting or hinging a retained end of the cutting tool to a release position may be used to allow the tool body to be extracted from the subsea casing. Upward movement of the tool body may be used to cause at least a portion of the cutting tool to be released from a retaining means. Release from the retaining means may be achieved by overcoming a frictional, interference or clamping force on the cutting tool or cutting tool holder.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a diagrammatic cross-sectional view of an apparatus according to an embodiment of the present invention positioned within the casing to be cut.

Figure 2 shows the same embodiment as in figure 1 , though with the cutting tool having completely penetrated the casing.

Figure 3 shows an embodiment of the clamping mechanism released via use of the hydraulic control lines, and the body carrying the tool being pulled upwards by the suspension line.

Figure 4 shows close up side and front views of an embodiment of a tool holder, tool and clamping mechanism. PARTICULAR DESCRIPTION

Embodiments of the present invention will now be described with reference to the accompanying figures. The generality of the present invention is not to be taken to be limited by the particularity of the following description.

Figure 1 shows the tool body 1 suspended into a casing 2 of a well by a line 3 from a vessel on the surface (not shown). Hydraulic motor 4 and clamping mechanisms (packers) 5 supply lines 6 are connected to the tool body. The hydraulic motor 4 is operatively connected to the drive shaft 1 1 via a reduction gearbox 12. Bearings 13a, 13b support the shaft for rotation. A free end of the drive shaft supports the rotational drive mechanism 14, and the rotational drive mechanism supports the cutting tool advance mechanism 15 (cutting tool slide).

The clamping mechanisms are shown in their clamped (extended) position holding the tool body 1 centralised within the bore of the casing. The cutting tool 7 is shown at its retracted position with the parting tool clear of the inner surface 8 of the casing. The tool rotation mechanism is not yet rotating.

The cutting (parting) tool 7 is held in a tool holder 9. The tool holder is pivotally or hingedly connected to a tool slide 10. In this embodiment, the tool holder is held in place so as to prevent the tool hinging free of the tool slide by a spring biased detent (not shown).

The tool slide can be constrained by radial guides that are fastened to the cutting tool rotation mechanism so that the tool slide is able to move in both an outwardly and inwardly radial direction.

Figure 4 shows close up side and front views of the tool 7, tool holder 9 and tool holder clamping mechanism 16 in close up in a clamped position (solid lines) and pivoted to a release position (broken lines) after cutting. The tool/tool holder clamping mechanism 16 includes clamp bolts 17 to retain the tool/tool holder in a generally horizontal position for cutting operations. It will be appreciated that the tool/tool holder can slide to advance the tool for cutting and preferably retract for release or after cutting. Preferably the tool, once advanced, pivots to a release position rather than retracts. The pivot/hinge 10 allows the tool holder to pivot/hinge to a released position after cutting in order to allow the tool body to be extracted upwardly.

The clamp bolts can provide sufficient clamping force to retain the tool/tool holder clamped for cutting purposes but, after cutting or as otherwise needed (e.g. early extraction of the tool due to failure or technical requirements etc), when the clamping force is released (which may be a power operated/assisted) or upward movement of the tool body causes the frictional clamping force to be overcome, the tool/tool holder pivots/hinges downwards relative to the rest of the tool body to a release position. The tool may have a weak point allowing the tool to fracture (e.g. when the tool body is extracted upwards relative to the tool) and break off allowing the remaining proximal end of the tool (the end held in the tool holder 9) to pivot/hinge downwards still held in the holder. The clamping force may be preset to a require specification so that a known amount of upward force is required before the tool is released. The tool/tool holder may be retained by shear bolts or pins having shear sections allowing the bolts/pins to shear through given sufficient force. Power operated tool/tool holder release mechanisms are also envisaged, such as including a hydraulic or pneumatic piston or electrically operated solenoid valve or drive motor.

A hydraulic motor supply and a hydraulic motor return line connected to the hydraulic motor within the tool body and their other ends go to the vessel within an umbilical and are connected to a hydraulic pump and control valves situated on the vessel.

Hydraulic pump and control valves also have further hydraulic control lines which are bundled within the umbilical to the clamping mechanisms of the tool.

The suspension line is connected to support the body within the casing.

In operation, the tool is lowered, together with the umbilical attached to the tool, from the vessel on the surface to the casing on the seabed.

The clamping mechanisms are in an undamped (retracted) position and the cutting tool is in its innermost (retracted) position.

A diver or ROV (remote operated vehicle) guides the tool into the top of the casing. The leading end of the body may have "bullet nose" features on its lowermost end to facilitate easy entry into the casing.

Once the tool is in its correct vertical position within the casing, the clamping mechanisms are actuated so that the tool body is prevented from both moving vertically and rotating in the casing.

The hydraulic motor supply line valve is opened, which causes the hydraulic motor to rotate and, consequently, the gearbox output shaft and cutting tool rotation mechanism to rotate the cutting tool.

In a preferred embodiment, the rotating cutting tool is such that as the rotating part of the apparatus rotates, the cutting tool slide moves radially outwards by a known amount for each complete revolution of the rotating tool. The amount of radial movement per revolution may be adjusted by altering the internal gearing of the rotary tool or by altering a drive connection ratio between the rotational and linear (slide) movements.

As the cutting tool commences to touch the casing, vibrations will commence in both the casing and the cutting tool assembly. Sound elements of these vibrations can be detected by the microphone 16. The output signal of the microphone is fed to equipment capable of detecting differences in both the amplitude and frequency of the output signal.

When the casing has been completely severed, the vibrations being caused by the still rotating cutting tool are different to those of it as it commenced cutting or during cutting. This difference of vibrations is an indicator that the casing has been completely severed and the control valve of the hydraulic motor is switched off thus stopping rotation of the cutting tool.

As the tool is pulled upwards the cutting (parting) tool is fractured and the hinge tool is forced from the retention detent allowing the body to be easily withdrawn from the casing.

Upon return to the vessel, a new cutting tool is clamped in the tool holder; the tool holder returned to its detent position; and the tool slide returned to its innermost position. The tool is now ready to be deployed once more when required.

It will be appreciated that the at least one clamp to hold the body in place in a casing can be actuated independent of the hydraulic/pneumatic drive for cutting operations. For example, the clamp(s) can be mechanically or electrically actuated (deployed and/or retracted) eg by none hydraulic/pneumatic actuation, or be actuated by its own dedicated hydraulic/pneumatic system. This can help isolate the clamping mechanism from the hydraulic/pneumatic cutting drive and therefore reduce/remove movement in the clamp(s) otherwise caused by the cutting forces. In this way, the clamping mechanism is isolated from the main hydraulic/pneumatic supply thereby eliminating hydraulic/pneumatic bounce that might otherwise reduce cutting efficiency/accuracy and/or longevity of the apparatus.