AU2010318780A1

AU2010318780A1 - Method and device for closing a well in the ground

Info

Publication number: AU2010318780A1
Application number: AU2010318780A
Authority: AU
Inventors: Per Lund; Svein H Solversen
Original assignee: Norse Cutting and Abandonment AS
Current assignee: Norse Cutting and Abandonment AS
Priority date: 2009-11-10
Filing date: 2010-11-08
Publication date: 2012-05-31
Also published as: NO20093308A1; EP2499329A4; EP2499329A1; WO2011059338A1; NO332901B1; US20120305251A1; BR112012011112A2

Abstract

A method and device for closing a well (1) in a formation (2) in the ground in which casing (4, 6, 8) is arranged, the method including: - moving a cutting tool (20) down into the well (1); - removing a longitudinal portion (46) of the casing (4, 6, 8) by cutting the longitudinal portion (46) into pipe wall pieces (44); - removing the cutting tool (20); and - setting a plug (48) against the formation (2) in the longitudinal portion (46) from which the casing (4, 6, 8) has been removed.

Description

WO 2011/059338 PCT/N02010/000404 METHOD AND DEVICE FOR CLOSING A WELL IN THE GROUND This invention relates to a method of closing a well in the ground. More particularly, it relates to a method of closing a well in the ground, the well being provided with casing. 5 The invention also includes a device for practising the method. When the production from 'a well in the ground, typically a petroleum well, has been terminated, it is necessary to close the well in a way that protects against future outflow of 10 well fluid from the well, among other things. Above each pressure-bearing zone it is usual to place at least two independent barriers including a suitable plugging material which is arranged to seal the well. In some cases it is necessary to remove a section in the longitudinal direc 15 tion of a casing for a barrier or a plug to be placed against the formation wall. According to the prior art, the casing material is machined away by means of a hard-metal blade which is arranged on a pipe string. The pipe string is connected to a drilling ves 20 sel or an installation with the necessary drilling equipment. Chips from the machining must be transported up to the sur face because the chips, which may be magnetic and may include relatively long chip coils, prevent tools from passing the portion if they are not removed.

WO 2011/059338 PCT/N02010/000404 Machining the longitudinal portion away from the casing by means of the prior art may take several days and is a very expensive operation. The invention has for its object to remedy or reduce at least 5 one of the drawbacks of the prior art. The object is achieved in accordance with the invention through the features which are specified in the description below and in the claims that follow. A method is provided for closing a well in a formation in the 10 ground, wherein casing is arranged, and wherein the method includes: - moving a cutting tool down into the well; - removing a longitudinal portion of the casing by cut ting the longitudinal portion into pipe wall pieces; 15 - removing the cutting tool; and - setting a plug against the formation in the longitudi nal portion from which the casing has been removed. By a cutting tool is meant, in this connection, a tool which is arranged to make cuts through the pipe wall as opposed to 20 machining tools which are arranged to remove pipe material by chipping. By cutting the longitudinal portion into pipe wall pieces, the production of voluminous chips is avoided while at the same time the pipe wall pieces are relatively easy to handle. 25 Further, the method may include cutting the longitudinal por tion by means of a fluid jet. By using a fluid jet, the fur ther induction of magnetic forces into the pipe wall pieces is avoided and the pipe wall pieces may be allowed to fall down and remain in the well. If desired, the pipe wall pieces 30 may be carried to the surface, for example by means of a mag- WO 2011/059338 PCT/N02010/000404 net. The method may further include the preparatory actions of: - filling the lower portion of the well with filler; - cutting an inner casing at a lower position in the 5 well than the position at which the longitudinal portion is located; and - removing the upper portion of the inner casing. The method may further include connecting the cutting tool to the surface by means of coiled tubing. The method thereby 10 makes it possible for the well to be shut down without the use of a drilling rig. The method can be practised by means of a cutting tool for cutting the longitudinal portion of a casing, the cutting tool including a nozzle head rotatable around its longitudi is nal axis, with at least one nozzle, the nozzle head being connected to coiled tubing, the coiled tubing extending to the surface and the cutting tool being connected to the cas ing by means of an anchor. The anchor may be a fixed anchor or a rolling anchor and the 20 cutting tool may be provided with an actuator for moving the nozzle head axially. In an embodiment in which the anchor is fixed, the actuator may be used for axial movement of the nozzle head during the cutting operation. If a rolling anchor is used, the coiled 25 tubing can be moved axially in the well without the use of a separate actuator. In a further embodiment the cutting head may be provided with a pendulum nozzle. The pendulum nozzle, which is of a design known per se, is arranged to pivot the fluid jet while the 30 nozzle head is kept stationary.

WO 2011/059338 PCT/N02010/000404 The cutting tool may be provided with a change-over valve which is arranged to selectably connect a fluid flow to a de sired nozzle. For example, the fluid flow may be directed to a cutting nozzle during the cutting operation and then di 5 rected to a cleaning nozzle during a subsequent cleaning op eration. The method and device according to the invention enable a considerable reduction in the time spent on closing petroleum wells while, at the same time, considerably simpler equipment 10 may be used compared with the prior art. The invention thereby provides for a substantial reduction in costs con nected with closing and finishing off wells. In what follows is described an example of a preferred em bodiment which is visualized in the accompanying drawings, in 15 which: Figure 1 shows schematically a well which has been prepared for a cutting operation according to the invention; Figure 2 shows schematically a section, on a larger scale, of a cutting head; 20 Figure 3 shows a cutting pattern in the wall of the casing; and Figure 4 shows schematically, on a smaller scale, a well af ter a plug has been set. In the drawings the reference numeral 1 indicates a petroleum 25 well in a formation 2. An inner casing 4, a second-inner cas ing 6 and other casings 8 are cemented into a borehole 10 by means of a cementation mass 12. A seal 14 seals between the inner casing 4 and the second inner casing 6.

WO 2011/059338 PCT/NO2010/000404 In figure 1 the well 1 is shown after preparatory work has been carried out, such as filling the lower portion of the inner casing 4 with filler 16, cutting the inner casing 4 and removing the upper portion, not shown, of the inner casing 4 5 from the well 1. Coiled tubing 18 with a cutting tool 20 fitted is in the well 1, the cutting tool 20 being positioned and held fixed in the second-inner casing 6 by means of an anchor 22. The cutting tool 20 includes a tool housing 24 with necessary 10 components known per se, not shown, for controlling the cut ting operation. An actuator 26 is arranged to move a ro tatable nozzle head 28 in the longitudinal direction of the well 1. In this preferred embodiment, the nozzle head 28 includes a is change-over valve 30 for selectably directing pressure fluid which is supplied via an actuator channel 32 from the coiled tubing 18 to a cutting nozzle 34 or a cleaning nozzle 36, see figure 2. The change-over valve 30 may be a so-called sequence valve 20 which changes its position every time the fluid pressure is relieved. When the cutting tool 20 is positioned in the well 1, the cutting may be started by fluid containing abrasive material flowing to the cutting nozzle 34 at relatively high pressure 25 via the coiled tubing 18 and the change-over valve 30. The nozzle head 28 is brought to move the cutting nozzle 34 along a predetermined path giving, for example, the cutting path 38 in the pipe wall 40 of the second-inner casing 6 as it is shown in figure 3.

WO 2011/059338 PCT/NO2010/000404 By subsequently cutting along the paths 42, pipe wall pieces 44 are formed from the longitudinal portion 46 of the second inner casing 6. By switching the change-over valve 30, pressure fluid is car s ried to the cleaning nozzle 36, whereby the pipe wall pieces 44 can be washed down or into the well 1. The part of the cementation mass 12 that may be behind the longitudinal portion 46 of the second-inner casing 6 is also removed by means of fluid jets from the nozzles 34, 36 of the 10 nozzle head 28. After the well 1 has been prepared, the coiled tubing 18 and the cutting tool 20 are pulled from the well 1, after which a plug 48 is set against the formation 2 in the longitudinal portion 46 in a manner known per se, see figure 4. In the 15 present embodiment a rubber type plug 48 is shown. A skilled person will understand that any suitable plug will be usable. In an alternative method, not shown, the longitudinal portion 46 may be chosen in a location in which two or more casings 6, 8, one outside another, will have to be cut away to expose 20 the formation 2.

Claims

1. A method of closing a well (1) in a formation (2) in the ground in which casing (4, 6, 8) is arranged, the method including: 5 - moving a cutting tool (20) down into the well (1); - removing a longitudinal portion (46) of the casing (4, 6, 8); - setting a plug (48) against the formation (2) in the longitudinal portion (46) from which the casing (4, 6, 10 8) has been removed, c h a r a c t e r i z e d i n that the method further includes cutting the longitu dinal portion (46) of the casing (4, 6, 8) into pipe wall pieces (44).

2. The method in accordance with claim 1, c h a r a c i5 t e r i z e d i n that the method further includes cutting the longitudinal portion (46) by means of a fluid jet.

3. The method in accordance with claim 1, c h a r a c t e r i z e d i n that the method further includes 20 letting the pipe wall pieces (44) remain in the well (1).

4. The method in accordance with claim 1, c h a r a c t e r i z e d i n that the method further includes the preparatory actions of: 25 - filling the lower portion of the well (1) with filler (16); - cutting an inner casing (4) at a lower position in the well (1) than the position at which the longitudi nal portion (46) is located; and 30 - removing the upper portion of the inner casing (4). WO 2011/059338 PCT/N02010/000404

5. The method in accordance with claim 1, c h a r a c t e r i z e d i n that the method further includes connecting the cutting tool (20) to the surface by means of coiled tubing (18). s

6. A cutting tool (20) for practising the method accord ingto claim 1, characterized i n that the cutting tool (20) includes a nozzle head (28) ro tatable around its longitudinal axis, with at least one nozzle (34, 36), the nozzle head (28) being con 10 nected to coiled tubing (18), the coiled tubing (18) extending to the surface, and the cutting tool (20) being connected to the casing (4, 6, 8) by means of ai anchor (22).

7. The cutting tool (20) in accordance with claim 6, 15 c h a r a c t e r i z e d i n that the anchor (22) is a rolling anchor.

8. The cutting tool (20) in accordance with claim 6, c h a r a c t e r i z e d i n that the cutting tool (20) is provided with an actuator (26) for moving the 20 nozzle head (28) axially.

9. The cutting tool (20) in accordance with claim 6, c h a r a c t e r i z e d i n that the nozzle head (28) is provided with a pendulum nozzle.

10. The cutting tool (20) in accordance with claim 6, 25 c h a r a c t e r i z e d i n that the cutting tool (20) is provided with a change-over valve (30) which is arranged to selectably connect a fluid flow to a desired nozzle (34, 36)