WO2022119445A1

WO2022119445A1 - Method and system for closing a well

Info

Publication number: WO2022119445A1
Application number: PCT/NL2021/050734
Authority: WO
Inventors: Jan Van Der Tempel
Original assignee: Brigantyne B.V.
Priority date: 2020-12-03
Filing date: 2021-12-03
Publication date: 2022-06-09
Also published as: NL2027036B1

Abstract

Method for closing a well, the well comprising at least a first tubing, wherein at least one plug is lowered into the first tubing where after the at least one plug is expanded inside the tubing, forcing an outer surface portion of the plug against an inner surface of the first tubing, closing off the well.

Description

Title: Method and system for closing a well

The invention relates to a method for closing a well. The invention further relates to a well closed off. The invention further relates to a system for closing off a well.

When a well, such as a gas or oil well has been exhausted or at least has to go out of commission, the well has to be closed off safely, at least in order to prevent any material such as gas or oil to escape from the well. Traditionally wells comprise an outer piping, especially a concrete lining, and an inner piping, the latter extending inside and substantially coaxially with the outer piping and made of metal. If a well has to be closed off, it is a legal requirement in most countries to provide at least two and sometimes even three or more closures of both the inner and outer piping, in order to secure that no leakage can occur. These closures are provided at great depth under the earth surface, for example two to three kilometers or more.

Traditionally wells are closed off in several consecutive steps. First a lower most closure is provided, by forming a concrete element on top of a bridge plug inside the inner tubing. The annular space between the inner and outer tubing may already be provided with a closure at that level, such as by a packer. A heavy and complex blow out preventer is positioned on top of the well. The inner tubing is then cut in longitudinal pieces and is removed from the well via the blow out preventer. This all requires using heavy equipment such as a rig and cranes. After the inner tubing has been removed a concrete second plug is formed above the lowermost plug, closing off the passage of the remaining outer tubing. This second plug may have a longitudinal length of several tens of meters, for example between 50 and 100 meters. After having formed this second plug an about three months waiting period of has to be observed in order to check for leaks. If no such leaks are found, a third concrete plug is formed closer to the surface, which may have a longitudinal length of tens of meters, for example ten meters, and is positioned for example tens of meters below the surface.

This traditional process is complicated and time consuming and furthermore requires complex and costly machinery and people over a long period of time.

An aim of the present disclosure is to provide an alternative method for closing off a well. An aim of the present disclosure is to provide for a method for closing off a well which is relatively easy to perform, relatively inexpensive and/or relatively quick. An aim of the present disclosure is to provide for a method which can be performed with relatively simple materials and equipment. An aim of the present disclosure is to provide for a well closed off in an alternative manner. An aim of the present disclosure is to provide for a system for closing off a well. At least one of these and other aims can be achieved at least in part with a method, well and/or system according to the disclosure.

In an aspect of the present disclosure a method for closing a well is provided, the well comprising at least a first tubing, wherein at least one plug is lowered into the first tubing, where after the at least one plug is expanded inside the tubing, forcing an outer surface portion of the plug against an inner surface of the first tubing, closing off the well.

In a traditional type well, having an inner and an outer tubing, the first tubing can be the outer tubing, when the plug can pass through an annular gap in the inner tubing. Alternatively the first tubing can be the inner tubing, which is then forced outward by the expanding plug, such that an outer surface portion of the inner tubing in turn closes off against an inner surface portion of the outer tubing. In such embodiment also in a first step an annular portion of the inner tubing can be forced outward by an expanding tool, such as for example known in the art, for example as disclosed in US4501514, forming a radially expanded inner tubing portion closing off against the inner surface of the outer tubing. Thereafter said tool can be removed and a plug can be expanded inside the radially expanded inner tubing portion, closing off the inner tubing. In a single tubing well the first tubing could be the single, only tubing.

The at least one plug can be a metal plug, such as a hollow metal plug at least having a bottom and an annular wall, which can be deformed plastically at least in part, such that a portion of the wall can be forced outward against an inner surface of the relevant tubing. Such plug can for example be cup shaped. By deforming the at least one plug plastically the plug will stay substantially in the expanded shape, closing off against the said inner surface. In embodiments such plug can be expanded radially outward by using a swaging tool. It shall however be clear that any suitable means can be used for expanding said plug at least partially at least radially, for example by mechanical tools, by hydraulic or pneumatic force, by explosion forming or the like. In embodiments the relevant part of the plug is stretched beyond the yield strength of the plug material, such that a deformation is obtained which will be maintained after removing of the expanding pressure.

In embodiments the at least one plug can comprise or be an elastically, deformable plug body which may be inflated, for example by pneumatic and/or hydraulic fluid. The fluid may be a fluid removable from the plug body, or may be a fluid which will stay inside the plug body, such as for example a flowable, solidifiable mass. Such mass may for example be cement or concrete or for example a foam or foam forming material. Such plug can for example be a plastic or rubber balloon.

In an aspect a method according to the present disclosure for closing a well having an inner tubing and an outer tubing can comprise lowering a cutting tool into the inner tubing, with which cutting tool at least two substantially longitudinal cuts are made through a wall of the inner tubing, and at least two substantially circumferential cuts are made through the wall of the inner tubing, such that at least two segments of the wall between the circumferential cuts and the longitudinal cuts are released from the wall, which segments are pushed outward in between the inner tubing and the outer tubing.

With such method segments of the inner tubing can be cut loose and be removed without having to lift the segments out of the well. These segments can easily be pushed into the gap between the inner tubing and the outer tubing, thus leaving an annular gap between a then upper section of the inner tubing and a then lower section of said inner tubing. In embodiments more than two longitudinal cuts can be made, spaced apart from each other radially, such that more than two such segments are cut and can be pushed outward into the gap, to fall down in said gap.

Alternatively a single circumferential cut, for example a substantially horizontal cut can be made, dividing the inner tubing into said upper section and said lower section, where after the upper section can be pulled upward thus forming said annular, longitudinal gap between the lower section and the upper section of the inner tubing. Similarly the upper section can be pulled upward relative to the lower section after longitudinal segments have been removed as previously described, for example for temporarily increasing the longitudinal length of the gap.

In embodiments a visco elastic material can be applied to the said outer surface portion of the plug, i.e. the outer surface portion or portions which is or are forced into contact with the inner surface of the relevant first tubing. Viscoelasticity is to be understood as at least meaning but not limited to the property of materials that exhibit both viscous and elastic characteristics when undergoing deformation. In embodiments the visco elastic material can be applied in at least two annular rings, longitudinally spaced apart from each other, for example at least one near an upper edge of a wall of the plug and one near a lower edge of said wall, the wall being at least part of the portion of the plug to be expanded radially outward for contacting the inner surface of the first tubing. The visco elastic material can then be enclosed between the plug and the inner surface of the first tubing, for example compressed, forming an even better closure cq sealing. The visco elastic material may in embodiments be tacky, such as adhesive, such that it will adhere to the plug and/or to the first tubing.

In embodiments the sealing material that is used can be a mouldable, self-adhesive and/or viscoelastic material. It preferably is watertight and gastight according to NEN 2768 qualifications. The sealing material can be such that it can be applied manually without the need of tools, primers or any pre-treatment of the surface. Preferably such material can have these properties persist until low to very low temperatures, such as a -20 degrees C° environment, and relatively high temperatures, such as for example +40 degrees C° environment, without tearing, breaking, melting or the build-up of internal stresses. In embodiments the material used as or for said substance can be Stopaq®, especially Stopaq® paste, provided by Stopaq BV, The Netherlands, or a similar sealant.

In embodiments after expanding the at least one plug a flowable, solidifiable mass is poured or injected into the tubing, forming a closure body above the at least one plug. The mass can for example be cement or concrete or a cement and/or concrete based mass, which can be poured for introduction into the well but which can solidify, such as cure in order to form a solid closing element, as is known in the art, closing off over a significant longitudinal length of the relevant tubing or tubings. In embodiments for example above the at least one plug at least one opening is formed through the wall of the inner tubing, where after the flowable, solidifiable mass passes through the at least one opening, such that the mass flows between the inner and outer tubing and inside the inner tubing and forms said closure body.

In embodiments at least one of the at least one plug and a or the cutting tool is lowered into the well using at least an umbilical. An umbilical can be or comprise a wire line, for example for providing electrical or pneumatic or hydraulic energy to for example a tool, and/or the umbilical can comprise a flexible tube, such as for example a coil tube, especially a metal coil tube, for feeding a fluid into the well, such as for example pneumatic hydraulic energy to for example a tool or a flowable mass, such as a flowable, sohdifiable mass for forming for example a closing element in and/or above the at least one plug.

In embodiments of a method of the disclosure more than one plug can be provided in the well, above each other seen in the longitudinal direction of the outer tubing and/or inner tubing, for forming two or more closures of the relevant tubing cq of the well.

A well according to the disclosure can comprise an outer tubing and an inner tubing extending into the earth from an earth surface, wherein at a depth below the earth surface a closure of the well has been formed, which closure comprises at least one plug, expanded inside the well, extending through an annular opening inside the inner tubing, such that an outer surface part of the plug is forced against an inner surface portion of the outer tubing, closing off any passage between the inner and outer tubing below the plug and the inner and outer tubing above the plug.

Alternatively a well according to the disclosure can comprise an outer tubing extending into the earth from an earth surface and an inner tubing extending inside the outer tubing from a depth below the earth surface downward, wherein a closure of the well has been formed above an upper end of the inner tubing, which closure comprises at least one plug, expanded inside the well, such that an outer surface part of the plug is forced against an inner surface portion of the outer tubing, closing off any passage between the inner and outer tubing below the plug and the outer tubing above the plug.

The disclosure further relates to a system for closing off a well, comprising at least one expandable plug and a tool for expanding said at least one plug inside tubing of a well. In further elucidation embodiments of the present disclosure will be discussed, by way of example only, with reference to the drawings.

Fig. 1 A - I show schematically in side view, partially in cross section consecutive steps in a method according to the disclosure;

Fig. 2A - C show schematically in side view, in cross section use of a tool inside a well for removing part of a tubing;

Fig. 2D and 2E show schematically a cross section along the line II - II in fig. 2B tubing of a well, before and after cutting in longitudinal direction of the tubing;

Fig. 2F and G show schematically in side view lowering a plug into a well and plugs mounted in the well, having been expanded in order to engage with an inner surface of the tubing of the well;

Fig. 3A - D show schematically in side view, in cross section, lowering and expanding a plug in tubing of a well;

Fig. 4A and B show schematically in side view forming a closure element in and/or above the plug.

Fig. 5A and B show schematically in top view and side view an alternative step of forming an expanded portion of an inner tubing of a well; and

Fig. 6 shows schematically in side view an alternative plug for use in a method and well according to the disclosure.

The drawings are schematic. In the drawings, similar or corresponding elements have been provided with similar or corresponding reference signs.

In this description a well has to be understood as at least meaning a well for natural resources such as hydrocarbons such as natural gas or oil. A well is a boring in the earth designed to bring such natural resources to the surface. A well according to the disclosure can extend far into the earth, for example deep wells having a longitudinal length between the upper most end and the lower most end of up to or above 6000 meters. A closure according to the present disclosure can be formed deep inside the well, for example but not limited to between 1000 and 6000 meters, such as for example at about 3000m below the earth surface or the upper most end of the well. A well according to the disclosure can be a land based well as well as a sea based (under water) well.

A well as disclosed by way of example only in this description can be referred to as a two tubing well. The well has an outer tubing which can also be referred to as outer lining or outer casing. Such outer tubing can comprise a cement or concrete annular wall with a lining, which may be referred to as casing. In this application for the sake of clarity and conciseness the annular wall and lining are shown and discussed as one tubing. The well moreover is shown and discussed having an inner tubing, which extends substantially coaxially within the outer tubing, wherein between the inner tubing and the outer tubing an annulus is formed, an annular space extending around the inner tubing. At least at one position deep into the well at least one packer can be provided, in the annulus, connecting the inner tubing to the outer tubing to hold the inner tubing in position and for sealing the annulus against flow of fluids such as liquids or gas from below said packer to above the packer in the annulus. Moreover valves and chokes can be provided in the inner tubing, for regulating flow in the inner tubing during production in the well. The inner tubing can be made of metal, as can the lining or casing of the outer tubing be.

In this description a longitudinal direction of the well should be understood as a direction between the upper most end, at or close to the earth surface, and the inlet end of the tubing, especially the lower most end of the tubing. It should be noted that the drawings are not to scale, since the actual closure which is provided as will be described will normally be over hundreds of meters below the earth’s surface. In the drawings is, where applicable, a part of the longitudinal length of the well has been removed between the earth’s surface and the position at which the closure is to be formed, showing the closure relatively close to the surface. As discussed the closure can be formed at great depth, for example but not limited to at a depth of over two kilometers, for example at about three kilometers below the earth’s surface.

Fig. 1A - 1 schematically show several steps of a method according to the present disclosure in a well 1. The well 1 is shown extending downward from the earth’s surface 2. The well 1 comprises an outer tubing 3 and an inner tubing 4, extending substantially coaxially inside the outer tubing 3. The tubing 3, 4 have a longitudinal direction L into the earth. An annulus 5 is formed between the inner tubing 4 and the outer tubing 3. At the upper end 6 of the tubing 3, 4 a well head 7 is mounted, in a conventional manner. At a certain longitudinal depth Li, for example at about 3000 meters below the earth’s surface 2, a bridge plug and/or a valve and/or choke 8, further referred to as bridge plug 8, is mounted inside the inner tubing 4. Close to said bridge plug or valve or choke 8 a packer 9 is shown, mounted in the annulus 5, closing off the annulus and holding the inner tubing 4 in position relative to the outer tubing 3.

As is shown in fig. 1A a reservoir plug 10 can be formed inside the inner tubing 4, close to or directly above the bridge plug 8, for example in a known manner by cement or concrete or such solifiable mass. The reservoir plug can form a first closure in the inner tubing 4.

After placing the reservoir plug 10 one or more plugs 11 are lowered into the inner tubing 4 and are expanded above the reservoir plug 10, such that the at least one plug 11 closes off at least the inner tubing 4, as will be explained hereafter in more detail. To this end at least one plug 11 is lowered into the inner tubing 4 where after the at least one plug 11 is expanded inside the tubing 4, forcing an outer surface portion 12 of the plug 11 against an inner surface of a first tubing, closing off the well.

In fig. IB two such plugs 11 are shown, above each other. In embodiments only one such plug 11 can be provided or more than two, as is for example shown in fig. 2. In fig. IB the lower plug 11A has been fully expanded, such that also the annulus 5 is closed off. The upper plug 11B is in the process of being expanded to a position as shown in fig. 1C.

In fig. IB the plugs 11A, B can be expanded inside the inner tubing 4, such that a wall portion 12 of the inner tubing 4 is expanded too, such that said surface portion 12 is forced against an inner surface portion 13 of the outer tubing 3. This is schematically shown in fig. 5A and B. In the embodiment of fig. 5A and B the plug 11 is lowered into the inner tubing 4 by for example an umbilical 14, such as for example a wireline or coil tube or a combination thereof. When the plug 11 has been lowered to the desired depth Li, the plug 11 is expanded, for example by forcing a gas or liquid into the plug 11 under high pressure through the umbilical 14, such that the plug 11 is expanded, especially expanded radially, as indicated by the arrows. By expanding the plug 11 the wall portion 12 of the inner tubing 4 is forced outward too, expanding said portion 12 radially such that the wall portion 12 comes into contact with and is forced against the inner surface portion 13 of the outer tubing 3. Thus the plug 11 closes off the passage 15 of the inner tubing 4, whereas the annulus 5 is closed off too, by the contacting surfaces 12, 13, thus forming at least a second closure of the well 1. Preferably the plug 11, especially the wall portion 12 of the plug 11 is expanded such that it deforms at least partially plastically, by stretching beyond the yield strength of the material of the plug, such that the plug maintains the expanded shape and configuration, even after lowering the pressure inside the plug 11 again. In the embodiment of fig. 5A and B the umbilical 14 can then be withdrawn or cut, for example directly above the plug 11, allowing the plug to stay in position at said depth Li. Alternatively a plug 11 could be mounted on an expander tool 16, as will be discussed in relation to for example fig 2 and 3, which expander tool can then be removed for the plug 11 after expansion of the plug 11. Alternatively the plug or plugs 11A, 11B in fig. 1 can be expanded after an annular portion 24 of the inner tubing 4 has been removed, or at least a longitudinal gap 17 has been formed in the inner tubing 4 at the desired depth Li, such that upon expansion of the or each plug 11 the plug can pass through such gap 17 and can be expanded such that the wall portion 12 of the plug is forced directly in contact with the inner surface portion 13 of the outer tubing. In such embodiments the plug or plugs 11 will close off directly both the passage 15 of the inner tubing 4 and the annulus 5, forming at least a second closure of the well 1.

After having placed the or each plug 11, one or more radial holes 19 can be formed through the wall 18 of the inner tubing 4, as shown in fig. 1C, above the plugs 11, for example by punching, drilling or any other suitable means. Then, as shown in fig. ID a flowable, solidifiable mass 20 such as cement or concrete can be introduced into the inner tube 4 and/or the annulus 5, which can flow through the at least one hole 19. Thus after sohdifying of the mass 20 a further closure 21 is formed, above the plug or plugs 11. The further closure 21 will fill both the passage 15 of the inner tubing 4 and the annulus 5 over a significant height H21, for example tens of meters. The height H21 can for example be, but not limited to, between 50 and 150 meters.

After having formed the further closure 21 over a period of time, for example some months, the well will be observed to ensure that the closures are functioning properly, by checking for leaks. This is schematically shown in fig. IE as a waiting period of for example three months. During that period of time only a leak testing equipment has to be present at the site, whereas contrary to the state of the art as discussed, most of the further equipment can be removed from the site. This increases it cost effectiveness.

After said period and if no leakage has been detected, the tubing 3, 4 can be cut, as schematically shown in fig. IF, above the closures and below the well head 7. Then the cut off parts of the tubing 3, 4 can be retrieved from the well, for example through the well head 7, in a known manner, as schematically shown in fig. 1G, using a crane 22, for example a mobile crane. Then a surface plug 23 can be formed inside the well 1, for example at the level where the tubing 3, 4 were cut off. Such surface plug 23 can again be made of a flowable, sohdifiable mass, such as cement or concrete, and will extend over a height H23 in the order of meters, for example between 5 and 20 meters, such as for example about 10 meters, which examples are not limiting. The surface plug 23 can for example be formed meters below the surface 2, in a known manner, as is shown in fig. 1H.

After having provided the surface plug 23, the well head 7 is removed, as is shown in fig. II. The well 1 is thus closed.

As discussed before, in embodiments an annular portion 24 of the inner tubing 4 can be removed for forming a longitudinal gap 17 through which the or at least a plug 11 can be expanded. In fig. 2 advantageous methods is disclosed for forming such gap 17. In this embodiment a tool 25 is lowered into the inner tubing 4, to the desired depth Li, for example by an umbilical 14, such as a wireline or coil tube. The tool 25 can be a cutting tool, such as for example but not limited to a laser cutter, a saw, a grinder or a water jet cutter or any such suitable tool for cutting through the wall 18 of the inner tubing 4.

By way of example, as is shown in fig. 2A the tool 25 can be a laser cutter emitting a laser beam 26 horizontally, from one or both opposite ends 27 of the tool 25, such that the laser beam 26 can cut through the wall 18. In fig. 2 A the tool 25 is shown as being held at a substantially fixed depth Li and is rotated around the longitudinal axis X - X of the tubing 3, 4, such that a substantially horizontal, annular cut 28 is formed, separating an upper part 4A of the tubing from a lower part 4B of the tubing.

After having made said horizontal cut 28, in embodiments the upper part 4A of the inner tubing 4 can be lifted and/or the lower part 4B could be allowed to move downward, for forming the annular gap 17, as is for example shown in fig. 2B.

Alternatively two horizontal cuts 28 can be made, longitudinally spaced apart over a distance D corresponding for example to the desired longitudinal height H17 of the gap 17. Thus an annular wall portion 29 of the inner tubing 4 between said two horizontal cuts 28 is cut loose from the inner tubing 4. This can then be removed for forming the gap 17.

In order to remove said annular wall portion 29 the tool 25 can be used for forming at least two longitudinal cuts 30 in said wall portion 29, such that the wall portion 29 is divided in segments 32, as is schematically shown in fig. 2C and E, which segments 32 can then be pushed outward, into the annulus 5, in which they can fall down, away from the gap 17. Preferably more than two longitudinal cuts 30 are made, dividing the wall part 29 in more than two segments 32, for example but not limited to three or four of such segments 32, which will make it easier to push the segments 32 out and allow them to fall away into the annulus 5. The segments 32 could alternatively be removed from the tubing 3, 4 by for example lifting them out of the well 1.

After having formed the gap 17 as discussed here above, a plug 11 can be lowered into the inner tubing 4, to the gap 17, as shown in fig. 2F, for example suspended from an umbilical 14. In the embodiment of fig. 2F and G the plug 11 initially has a cup shape, comprising a bottom 32 and an annular wall 33 extending upward from the bottom 32. In fig. 2F at the top of the drawing the plug 11 is shown being lowered into the passage 15 of the inner tubing 4. Initially the maximum diameter Dn(initial) of the plug 11 is smaller than the inner diameter D4 of the passage 15 of the inner tubing 4. In fig. 2F the plug 11 is again shown lowered to the level of the gap 17, where it is shown in a partially radially expanded state, as indicated by the arrows 34. The plug 11 in this embodiment has a slightly truncated conical shape, open to the upper side 35. It can however also be formed differently, for example cylindrical, and can have an open of partially or even fully closed upper side too.

As can be seen in comparing fig. 2F and 2G for example, the plug 11 can be expanded radially further, until the wall 33, especially an outer surface portion 12 thereof, is forced against the inner surface portion 13 of the outer tubing. In the embodiment shown a lower most plug 11 is shown resting on or at least in close contact with the upper end of the lower part 4B of the inner tubing 4. In embodiments a sealant can be provided between the bottom 32 of the plug and the upper end of the lower part 4B of the inner tubing, for an even better closure.

In fig. 2G three plugs 11 are shown extending through the same gap 17. It shall be clear that any number of plugs can be provided, such as one, two or more than three. If multiple plugs 11 are provided, they can extend through different gaps 17 or through the same gap 17.

The plug or plugs 11 can be expanded in any suitable manner, preferably plastically. Figs. 3A - 3D show by way of example a practical manner of expanding a plug 11. Fig. 3A shows a portion of an inner and outer tubing 4, 3 with a gap 17 in the inner tubing 4, as discussed earlier. A plug 11 is lowered into the inner tubing 4 through the passage 15 to the level of the gap 17, hanging in this embodiment from an umbilical 14 and an expander tool 16. The plug 11 can for example be suspended from the tool 16 by the bottom 32 and/or the wall 33, for example held in place by a magnet, adhesive, form fitment, suction, clamping or any other suitable means, or can be suspended directly from the umbilical 14 or a combination thereof.

As can be seen in fig. 3 the outside of the plug 11 can be provided in part or entirely with a sealant 34, for example an visco elastic substance. In fig. 3 by way of example there are two annular rings 35A, 35B of such sealant provided, near an upper edge 36 of the wall 33 and near a lower edge 37 of the wall 33 respectively. However, such sealant can also be provided differently, for example covering substantially the entire outer surface 12 of the wall 33 or covering the entire outside surface of the plug 11. The sealant 34 can for example be adhesive, for example a pressure sensitive adhesive, such that it sticks easily to the plug 11 and to the inner surface 13 of the outer tubing 3.

In fig. 3A and 3B a shielding 38 is provided at an outside covering the sealant 34, such that during lowering of the plug 11 through the passage 15 the sealant will not be contaminated and moreover will not adhered to the wall 18 of the passage 15. The shielding 38 can for example be a cylinder which extends around the plug 11 annularly and which will break away when the plug 11 is expanded. For example in the position as shown in fig. 3B the shielding may be removed by expanding the plug 11, such that the shielding breaks away and will fall down into the tubing 3. Alternatively other means can be provided for removing the shielding, for example mechanically, such as but not limited to pulling the shielding back up separate from the plug, by a further wire.

After the shielding is removed, when used, the plug 11 can be expanded, as is for example shown in fig. 3C, by the expanding tool 16. The plug 11 is preferably primarily or even only expanded radially. The wall 33 is pushed outward by elastic deformation of the plug 11, such that the wall

33 is brought into contact with the inner surface 13 of the outer tubing 3. In this embodiment especially the sealant 34 will be brought into contact with the outer tubing 3 first, which can be considered a first tubing here. When expanding the plug 11 further, the sealant will be compressed between the wall 33 and the inner surface of the outer tubing 3, preferably such that a portion 12 of the wall 33 between the rings of sealant will also be brought into contact with the surface 13. Thus the closure between the plug and the first tubing 3 is even further improved. In embodiments without the sealant

34 on the plug 11 the wall 33 will be pushed against the inner surface 13 directly. After having expanded the plug 11 sufficiently, the expanding tool 16 may be retrieved. To that end the expander tool 16 can for example be brought back into its original dimensions, as is shown in fig. 3D, such that it can be pulled back up out of the plug and the inner liner 3, as indicated by arrow U in fig. 3D. The plug 11 will stay in the position in which it is expanded. As discussed before with respect to fig. 1, in the embodiments of figs. 2 and 3 as discussed too further closures can be formed above the one or more plugs 11, such as a further closure and a surface plug.

In figs. 4 A and B an alternative embodiment is disclosed, in which a plug 11 as discussed in fig. 2 or 3 can be used. In this embodiment the umbilical 14 from which the expander tool 16 is suspended is used, during and/or after expansion of the plug 11, for feeding a flowable and solidifiable mass 20 into the well 1, especially into the plug 11 and/or into the inner tubing passage 15 and/or the annulus 5. As can be seen in fig. 4A by way of example the mass 20 can flow directly into the plug 11, for filling the plug 11 with a mass 20 which will solidify, even better ensuring that the plug 11 will keep its expanded state. In fig. 4B by way of example it is shown that the mass can flow on top of the plug 11, such that the level of the mass 20 can rise inside the tubing 3, 4, both in the passage 15 and the annulus 5, for example passing below a lower end of the upper part 4A of the inner tubing 4 and/or through holes or openings 19 in the wall 18, as indicated by the arrows 41. Thus in an easy way a further closure can be formed above the plug 11. During outflow of the mass 20 the expander tool 16 can be pulled up further with the rising of the level of mass in the well.

In embodiments the expander tool 16 can be a known mechanical tool, such as a swaging tool. In embodiments the expander tool can be hydraulic and/or pneumatic tooling. Such tools and tooling are well known in the art. An example of a swaging tool is for example disclosed in US4501514 or WO2019/043416, which are only disclosed as example and are by no means limiting the scope of the disclosure. For driving the expander tool 16 and/or the cutting tool 25 the umbilical can be used for feeding at least one of power fluid and/or electricity into the well 1 for at least one of expanding the at least one plug 11 and driving at least one tool 16, 25 inside the well 1. Any driving fluid can be recaptured by feeding it back up the well again, or can be discarded inside the well. Alternatively other means for expanding the plug 11 can be used, such as for example explosion forming.

Fig. 6 shows a further alternative method and system for closing off a well 1, in which an at least partly flexible, inflatable plug 11 is used, which is expanded by inflation. The plug 11 can for example be balloon shaped, such that it can be elastically expanded at least radially, by introducing a pressure fluid such as a gas or liquid into the plug 11. In this embodiment the plug 11 after inflation can be closed, in order to maintain the pressure inside the plug 11 to keep it in the expanded state. Alternatively the plug can be filled with a solidifying mass 20, such as cement, concrete, foam or the like, which can also be used for inflating the plug 11. After having expanded the plug 11 and fixating the expanded state, again further closures can be formed above the plug, as described before.

In all of the embodiments shown and discussed an upper part 4A of the inner tubing 4 can be removed in part or in full from the well 1 before forming further closures above the at least one plug 11.

A closed off well 1 as disclosed herein comprises an outer tubing 3 and an inner tubing 4 extending into the earth from an earth surface 2. At a depth below the earth surface 2 a closure of the well has been formed, which closure comprises at least one plug 11, expanded inside the well 1. The plug in embodiments extends through an annular opening 17 in the inner tubing 4, such that an outer surface part 12, 33 of the plug 11 is forced against an inner surface portion 13 of the outer tubing 3, closing off any passage between the inner and outer tubing 4, 3 below the plug 11 and the inner and outer tubing 4, 3 above the plug. If the upper part 4A of the inner tubing has been removed or was never present obviously the at least one plug will close off any passage between the inner and outer tubing 4, 3 below the plug 11 and the outer tubing 3 above the plug 11. In such embodiment a closure of the well 1 has been formed above an upper end of the inner tubing 4 or at least the remaining lower part 4B thereof. Alternatively the well can comprise an inner tubing 4 which has in part been expanded against the inside surface of the outer tubing 3. Obviously also combinations of such embodiments could be used.

In embodiments the plug 11 can be expanded such that a portion of the outer tubing is expanded too, even better fixating the plug in position in the well 1.

A system for closing a well 1 as disclosed can comprise at least one expandable plug and an expander tool for expanding said plug inside a tubing of a well. The system can furthermore comprise a cutting tool for providing an annular opening in a wall of a tubing. The system can furthermore comprise a tool for feeding a flowable, solidifying mass into a tubing of a well and/or into a plug as disclosed. Wherein a flowable mass can be a liquid, a suspension or a particle matter suitable for flowing into a tubing of a well. Solidifying should be understood as at least meaning transforming from a flowable mass to a set mass, such as concrete, cement, foaming materials, two or multi component materials for chemical reaction and the like.

The embodiments as disclosed are shown by way of example only and should not be construed as limiting the scope of the disclosure. Many variations are possible within the scope of the invention as defined by the claims.

For example some of the steps as discussed can be performed in different order. For example the well head could be removed earlier than after placing the plug or after providing any further closure. Closures using one or more plugs according to the disclosure could be provided at different longitudinal depths of the well. Such alternatives as well as any combination of features of disclosed embodiments should also be considered as having been disclosed herein or at least as covered by the disclosure and the claims.

Claims

1. Method for closing a well, the well comprising at least a first tubing, wherein at least one plug is lowered into the first tubing where after the at least one plug is expanded inside the tubing, forcing an outer surface portion of the plug against an inner surface of the first tubing, closing off the well.

2. Method according to claim 1, wherein the plug is plastically deformed by said expanding of the plug.

3. Method according to claim 1 or 2, wherein the first tubing is an inner tubing of the well, surrounded by a second tubing, wherein the first tubing is expanded by expanding the plug.

4. Method according to claim 1 or 2, wherein the first tubing is an outer tubing of the well, wherein an inner tubing extends inside the outer tubing, wherein a longitudinal portion of the inner tubing is removed, forming a longitudinal gap in the inner tubing, and the plug is expanded through the longitudinal gap against the first tubing.

5. Method according to claim 4, wherein the longitudinal portion is a circumferential longitudinal or annular portion.

6. Method according to claim 4 or 5, wherein a cutting tool is lowered into the inner tubing, with which cutting tool at least two substantially longitudinal cuts are made through a wall of the inner tubing, and at least two substantially circumferential cuts are made through the wall of the inner tubing, such that at least two segments of the wall between the circumferential cuts and the longitudinal cuts are released from the wall, which segments are pushed outward in between the inner tubing and the outer tubing.

7. Method according to any one of the preceding claims, wherein a metal hollow plug is used.

8. Method according to any one of the previous claims, wherein the plug is expanded by a swaging tool.

9. Method according to any one of the preceding claims, wherein the plug is expanded by hydraulic and/or pneumatic tooling.

10. Method according to any one of the preceding claims, wherein a visco elastic material is applied to the said outer surface portion of the plug.

11. Method according to any one of claims 1 - 6, wherein an at least partly flexible, inflatable plug is used, which is expanded by inflation.

12. Method according to any one of the preceding claims, wherein after expanding the at least one plug a flowable, solidifiable mass is poured or injected into the tubing, forming a closure body above the at least one plug.

13. Method according to any one of claims 4 - 11 and 12, wherein above the at least one plug at least one opening is formed through the wall of the inner tubing, where after the flowable, solidifiable mass passes through the at least one opening, such that the mass flows between the inner and outer tubing and inside the inner tubing and forms said closure body.

14. Method according to any one of the previous claims, wherein the at least one of the at least one plug and a or the cutting tool is lowered into the well using at least an umbilical.

15. Method according to claim 14, wherein the umbilical is or comprises a wireline.

16. Method according to claim 14 or 15, wherein the umbilical is or comprises at least a coil tubing.

17. Method according to any one of claims 14 - 16, wherein the umbilical is used for feeding at least one of power fluid and electricity into the well for at least one of expanding the at least one plug and driving at least one tool inside the well.

18. Method according to any one of claims 14 - 17, wherein the umbilical is used for feeding at least a flowable, solidifiable mass into the well.

19. Method according to any one of the previous claims, wherein after positioning the at least one plug into the well a closing element is formed above the at least one plug, which closing element is formed from a flowable, solidifiable mass fed into the well and allowed to solidify at least above the at least one plug.

20. Method according to any one of the previous claims, wherein at least two plugs are positioned inside the well, above each other.

21. Well, comprising an outer tubing and an inner tubing extending into the earth from an earth surface, wherein at a depth below the earth surface a closure of the well has been formed, which closure comprises at least one plug, expanded inside the well, extending through an annular opening inside the inner tubing, such that an outer surface part of the plug is forced against an inner surface portion of the outer tubing, closing off any passage between the inner and outer tubing below the plug and the inner and outer tubing above the plug.

22. Well, comprising an outer tubing extending into the earth from an earth surface and an inner tubing extending inside the outer tubing from a depth below the earth surface downward, wherein a closure of the well has been formed above an upper end of the inner tubing, which closure comprises at least one plug, expanded inside the well, such that an outer surface part of the plug is forced against an inner surface portion of the outer tubing, closing off any passage between the inner and outer tubing below the plug and the outer tubing above the plug.

23. Well according to claim 21 or 22, wherein the at least one plug is or comprises a metal cup, having at least a bottom wall and an annular side wall.

24. Well according to claim 21 or 22, wherein the at least one plug is or comprises at least one flexible expandable body, especially a balloon type of body.

25. Well according to any one of claims 21 - 24, wherein the at least one plug has been provided with a sealant at at least said outer surface part, wherein the sealant preferably is or comprises a visco elastic material.

26. Well according to any one of claims 21 - 25, wherein a closing body extends inside the well above the at least one plug, closing off any passage of at least the outer tubing or of the outer tubing and the inner tubing.

27. System for closing off a well, comprising at least one expandable plug and a tool for expanding said at least one plug inside tubing of a well.