AU2010330957A1

AU2010330957A1 - Method and device for closing a well

Info

Publication number: AU2010330957A1
Application number: AU2010330957A
Authority: AU
Inventors: Per Lund; Svein H. Solversen
Original assignee: Norse Cutting and Abandonment AS
Current assignee: Norse Cutting and Abandonment AS
Priority date: 2009-12-17
Filing date: 2010-12-14
Publication date: 2012-06-21
Also published as: BR112012014203A2; WO2011074981A1; US20120279706A1; EP2513414A1; NO20093545A1

Abstract

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); - cutting openings (42) across a longitudinal portion (46) of the casing (4, 6, 8); - removing the cutting tool (20); and - filling a curable mass into the casing (4, 6, 8), the curable mass flowing through the openings (42), filling a space between the casing (4, 6, 8) and the formation (2).

Description

WO 2011/074981 PCT/N02010/000459 METHOD AND DEVICE FOR CLOSING A WELL 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 is -direction 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 20 vessel or an installation with the necessary drilling equipment. Chips from the machining must be transported up to the surface because the chips, which may be magnetic and may include relatively long chip coils, prevent tools from passing the portion if the chips are not removed.

WO 2011/074981 PCT/N02010/000459 2 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 s 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; - cutting openings in the pipe wall ,across a longitude nal portion of the casing; 1s - removing the cutting tool; and - filling a curable mass into the casing, the curable mass flowing through the openings, filling a space between the casing and the formation. Together with the mass present in the space between the 20 casing and the formation, the curable mass present in the casing forms a plug. The plug is permanent and seals against the formation. By a cutting tool is meant, in this connection, a tool which is arranged to make cuts through the pipe wall as opposed to 25 machining tools which are arranged to remove pipe material by chipping. By cutting pipe wall pieces from the longitudinal portion, the production of voluminous chips is avoided while at the same time the pipe wall pieces are relatively easy to handle.

WO 2011/074981 PCT/N02010/000459 3 Further, the method may include cutting the openings by means of a fluid jet. By using a fluid jet, the further induction of magnetic forces into the pipe wall pieces is avoided. The pipe wall pieces cut out may be allowed to fall down and 5 remain in the well. If desired, the pipe wall pieces may be carried to the surface, for example by means of a magnet. 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 10 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 15 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 20 longitudinal 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 casing by means of an anchor. The anchor may be a fixed anchor or a rolling anchor and the 25 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 30 tubing can be moved axially in the well without the use of a separate actuator.

WO 2011/074981 PCT/N02010/000459 4 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 nozzle head is kept stationary. s The cutting tool may be provided with a change-over valve which is arranged to selectably connect a fluid flow to a desired nozzle. For example, the fluid flow may be directed to a cutting nozzle during the cutting operation and then directed to a cleaning nozzle during a subsequent cleaning 10 operation. 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 may be used compared with the prior art. The invention 15 thereby provides for a substantial reduction in costs connected with closing and finishing off wells. In what follows is described an example of a preferred embodiment which is visualized in the accompanying drawings, in which: 20 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; Figure 3 shows a cutting pattern in the wall of the casing; 25 Figure 4 shows schematically, on a smaller scale, a well prepared for grouting; and Figure 5 shows the well after grouting. In the drawings the reference numeral 1 indicates a petroleum WO 2011/074981 PCT/N02010/000459 5 well in a formation 2. An inner casing 4, a second-inner casing 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 s inner casing 6. 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 10 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 15 components known per se, not shown, for controlling the cutting operation. An actuator 26 is arranged to move a rotatable nozzle head 28 in the longitudinal direction of the well 1. In this preferred embodiment, the nozzle head 28 includes a 20 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 25 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 WO 2011/074981 PCT/N02010/000459 6 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 so 5 that an opening 42 is cut, see figures 3 and 4. After that, the desired number of openings 42 may be cut. Through the choice of a cutting pattern, the pipe wall pieces 44 that are formed may be given a suitable size. The openings 42 in the second-inner casing 6 may extend across a 10 longitudinal.portion 46. By switching the change-over valve 30, pressure fluid is carried 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 15 longitudinal portion 46 of the second-inner casing 6 is also removed via the openings 42 by means of fluid jets from the nozzles 34, 36 of the nozzle head 28. After the cutting work in the well 1 is finished, the coiled tubing 18 and the cutting tool 20 are pulled out of the well 20 1. The longitudinal portion 46 is thereby prepared for grouting, see figure 4. A curable mass is then filled into the second-inner casing 6. The mass flows through the openings 42 and in between the second-inner casing 6 and the formation 2. Thereby a plug is 25 formed, closing the cross section of the borehole 40. In an alternative method, not shown, the longitudinal portion 46 may be chosen in a location in which openings will have to be cut in two or more casings 6, 8, one outside another, to give access to 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); - cutting openings (42) across a longitudinal portion (46) of the casing (4, 6, 8); - removing the cutting tool (20), c h a r a c t e r i z e d i n that the method further includes 1o filling a curable mass into the casing (4, 6, 8), the curable mass flowing through the openings (42), filling a space between the casing (4, 6, 8) and the formation (2) to form a full cross-sectional plug.

2. The method in accordance with claim 1, c h a r a c is t e r i z e d i n that the method further includes cutting the openings (42) 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 letting the pipe wall pieces (44) remain in the well 20 (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: - filling the lower portion of the well (1) with 25 filler (16); - cutting an inner casing (4) at a lower position in the well (1) than the position at which the longitudinal portion (46) is located; and - removing the upper portion of the inner casing (4). 30

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 WO 2011/074981 PCT/N02010/000459 8 connecting the cutting tool (20) to the surface by means of coiled tubing (18).

6. A cutting tool (20) for practising the method according to claim 1, c h a r a c t e r i z e d i n 5 that the cutting tool (20) includes a nozzle head (28) rotatable around its longitudinal axis, with at least one nozzle (34, 36), the nozzle head (28) being connected to coiled tubing (18), the coiled tubing (18) extending to the surface, and the cutting tool 10 (20) being connected to the casing (4, 6, 8) by means of an anchor (22).

7. 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 anchor (22) is a rolling anchor. 15

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 nozzle head (28) axially.

9. The cutting tool (20) in accordance with claim 6, 20 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, 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 25 is arranged to selectably connect a fluid flow to a desired nozzle (34, 36).