AU2011343204A1

AU2011343204A1 - Rock anchor

Info

Publication number: AU2011343204A1
Application number: AU2011343204A
Authority: AU
Inventors: Jorgen Hallundbaek
Original assignee: Welltec AS
Current assignee: Welltec AS
Priority date: 2010-12-17
Filing date: 2011-12-16
Publication date: 2013-05-02
Also published as: RU2013132394A; EP2652257A1; MX2013006624A; US20140102719A1; CN103261578A; BR112013014561A2; CA2821840A1; WO2012080486A1; EP2466064A1

Abstract

The present invention relates to a formation fixation device for securing a tubular in an open-hole wellbore, the formation fixation device comprising a tubular part, a fixation unit and a fluid passage. Furthermore, the invention relates to a downhole fixation system for securing a casing comprising a first end and a second end in an open-hole wellbore and to a method of permanently fixating a tubular part in an open-hole wellbore as well as to use of a formation fixation device according to the invention for fixating a tubular part in an open-hole wellbore.

Description

WO 2012/080486 PCT/EP2011/073100 1 ROCK ANCHOR Field of the invention The present invention relates to a formation fixation device for securing a tubular 5 in an open-hole wellbore. Furthermore, the invention relates to a downhole fixation system for securing a casing comprising a first end and a second end in an open-hole wellbore and to a method of permanently fixating a tubular part in an open-hole wellbore as well as to use of a formation fixation device according to the invention for fixating a tubular part in an open-hole wellbore. 10 Background art Wells are completed in a variety of ways; some are made as open-hole completions and some as casing completions. In casing completing, the casing is 15 often cemented in the wellbore. This process is slow and requires a drilling rig at the surface, which is very expensive to use. It is desirable to be able to run in and secure the casing in an open-hole wellbore as fast as possible to reduce costs associated with renting expensive drilling rigs. 20 An alternative to cemented casings is disclosed in WO 09/120759 which describes a combined "Wellbore anchor and isolation system" comprising a tubular which may be attached to a tool string and lowered into a well. The tubular is provided with an anchor system comprising telescopic pistons which are extended in a radial direction by applying hydraulic pressure from within. 25 Each of the telescopic pistons is comprised by three rings movable in relation to one another. An isolation element is disposed on the outside of the tubular, creating an isolated zone when engaged with the walls of a wellbore. When a casing has been positioned in an open-hole wellbore, it is sometimes 30 important that it does not move and that the exact position is maintained. This is especially important when annular barriers are used to seal off a section of the wellbore. If the casing is moved following the deployment of the annular barriers, the sealing characteristics of the annular barriers may be compromised. The deployment of the annular barriers may in itself contribute to 35 a movement of the casing in the well.

WO 2012/080486 PCT/EP2011/073100 2 Summary of the invention It is an object of the present invention to wholly or partly overcome the above disadvantages and drawbacks of the prior art. More specifically, it is an object to 5 provide an improved formation fixation device, system and method for securing casing in an open-hole wellbore downhole. The above objects, together with numerous other objects, advantages, and features, which will become evident from the below description, are accomplished 10 by a solution in accordance with the present invention by a permanent formation fixation device for securing a tubular in an open-hole wellbore, the formation fixation device comprising: - a tubular part extending in an axial direction, the tubular part having an exterior surface and a hollow interior, 15 - a fixation unit arranged at the exterior surface of the tubular part, the fixation unit having a first end and a second end movable in relation to one another in the axial direction, and - a fluid passage extending from the hollow interior to one of the ends of the fixation unit; 20 wherein at least one of the ends of the fixation unit is moved when the tubular part is pressurised from within, forcing the fixation unit to project in a radial direction in relation to the tubular part, whereby the fixation unit enters into a projected position. 25 An advantage in this respect is that the casing may be rapidly secured in an open-hole wellbore during construction of an oil or gas well just by pressurising the casing from within e.g. by means of a drill pipe. This reduces the time required to complete the well and thereby reduces the days in which an expensive drilling rig is needed. Further, it may be possible to secure the casing 30 in the wellbore and deploy the annular barriers as part of the same working procedure and substantially simultaneously. In an embodiment of the invention, the fixation unit may comprise a locking mechanism for permanently locking the fixation unit in the projected position. 35 An advantage in this respect is that the fixation unit does not collapse when the tubular part is no longer pressurised.

WO 2012/080486 PCT/EP2011/073100 3 Furthermore, the fixation unit may comprise a slotted liner having a plurality of members connecting the first end and the second end, the members being projected in a radial direction in relation to the tubular part when the ends of the fixation unit are moved towards each other. 5 This creates a simple and reliable construction with a plurality of members engaging the formation. The slotted liner may surround the tubular part. 10 Moreover, each of the members may have a bend initiator, such as a transverse slot or fold, arranged substantially in a middle part of each member in the axial direction. 15 By having a bend initiator, a bend point of the members may be controlled and the bend initiated, thereby decreasing the amount of force used for initial bending. Furthermore, the fixation unit may comprise two pivotally connected members. 20 Additionally, the fixation unit may be arranged in a recess in the tubular part. An advantage in this respect is that the use of a fixation unit in combination with a casing does not affect the outer diameter of the casing. 25 Also, the fixation unit may be arranged on the outside of the tubular part. In addition, the fixation unit may be connected with the exterior surface of the tubular part. 30 Moreover, the fixation unit may be arranged partly inside the tubular part and extend through a slot in the exterior surface. In an embodiment, one of the ends of the fixation unit may constitute a piston 35 part comprising a surface adapted for receiving a force induced by a pressurised medium contained in the hollow interior of the tubular part.

WO 2012/080486 PCT/EP2011/073100 4 In another embodiment, both ends of the fixation unit may constitute a piston part comprising a surface adapted for receiving a force induced by a pressurised medium contained in the hollow interior of the tubular. 5 Moreover, one of the ends of the fixation unit may be fixed in relation to the tubular part. In addition, both ends of the fixation unit may be movable in relation to the tubular part. 10 This may reduce the axial movement of the device during activation of the fixation unit and facilitate the engagement of the fixation unit with the formation. In an embodiment, the formation fixation device may comprise a plurality of 15 fixation units. The plurality of fixation units may be distributed around a periphery of the tubular part. 20 Moreover, the plurality of fixation units may be distributed along the axial direction of the tubular part. Hereby the formation fixation device is aligned inside the wellbore. Furthermore, the plurality of piston parts may be distributed around a periphery 25 of the tubular. Additionally, the plurality of piston parts may move one end of the fixation unit, e.g. the slotted liner. 30 Also, the plurality of fixation units distributed along the axial direction of the tubular part may be displaced relative to one another around the periphery of the tubular part. In addition, the plurality of fixation units may be evenly distributed in the axial 35 direction and around the periphery of the tubular part.

WO 2012/080486 PCT/EP2011/073100 5 The present invention furthermore relates to a downhole fixation system for securing a casing comprising a first end and a second end in an open-hole wellbore, the fixation system comprising: - the formation fixation device described above, 5 - a casing connected with the tubular of the formation fixation device, - one or more annular barriers comprising a tubular part and a surrounding expandable sleeve, and - a pressure creating device fluidly connected to the hollow interior of the tubular part of the formation fixation device. 10 In an embodiment, the pressure creating device may be a downhole tool adapted to be arranged in fluid connection with the fluid passage. Furthermore, the pressure creating device may be a pump positioned on the 15 outside of the wellbore. Moreover, the pressure creating device may be connected with one end of a drill pipe and another end of the drill pipe may be connected with a connecting unit which is sealingly connectable with the first end of the casing, and the second 20 end of the casing being sealed. In addition, sealing means, such as packers, may be arranged around the drill pipe on opposite sides of the fluid passage, whereby a defined section of the casing may be pressurised. 25 Also, the invention relates to a method of permanently fixating a tubular part in an open-hole wellbore, the method comprising the steps of: - connecting the permanent formation fixation device described above with one or more casing elements, 30 - positioning the formation fixation device at a predetermined location in an open-hole wellbore, and - activating the fixation unit by applying a hydraulic pressure to one of the ends of the fixation unit, whereby the fixation unit engages with the sides of the wellbore. 35 Finally, the present invention relates to use of a formation fixation device as described above for fixating a tubular part in an open-hole wellbore WO 2012/080486 PCT/EP2011/073100 6 Brief description of the drawings The invention and its many advantages will be described in more detail below with reference to the accompanying schematic drawings, which for the purpose of 5 illustration show some non-limiting embodiments and in which Fig. la shows a view of a formation fixation device in an unset condition according to the invention, 10 Fig. lb shows a view of the formation fixation device shown in Fig. la in a set condition, Fig. 2a shows one embodiment of a formation fixation device comprising a slotted liner, 15 Fig. 2b shows a cross-sectional view across line a-a of the formation fixation device shown in Fig. 2a, Fig. 2c shows a view of a member having a bend initiator, 20 Fig. 3 shows a view of the embodiment shown in Fig. 2a in the set condition, Fig. 4 shows a view of one embodiment of a fixation unit in an intermediate position, 25 Fig. 5a shows a view of a locking mechanism, Fig. 5b shows another embodiment of the locking mechanism, 30 Fig. 6 shows an alternative embodiment of the permanent formation fixation device with the fixation unit arranged in a recess in the tubular part, Fig. 7a shows a schematic drawing of an open-hole wellbore with the permanent formation fixation device arranged in connection with other casing elements and 35 a pressure creating device deployed in the well, and WO 2012/080486 PCT/EP2011/073100 7 Fig. 7b shows a schematic drawing of an open-hole wellbore with an alternative pressure creating device deployed in the well. All the figures are highly schematic and not necessarily to scale, and they show 5 only those parts which are necessary in order to elucidate the invention, other parts being omitted or merely suggested. Detailed description of the invention 10 Figs. la and lb show a formation fixation device 1 for positioning in an uncased wellbore. Fig. la shows the formation fixation device 1 in a relaxed position in an unset condition, whereas Fig. lb shows the formation fixation device in an activated position. In Figs. la and 1b, the formation fixation device 1 comprises a tubular part 10 having a hollow interior 29. The tubular part 10 extends in an 15 axial direction and has an exterior surface 11 defining a periphery of the formation fixation device 1. The formation fixation device 1 further comprises a fixation unit 20 projectable in a radial direction of the tubular part for fixating the formation fixation device in the wellbore by pressurising the tubular from within, whereby the fixation unit 20 penetrates the formation. 20 When the formation fixation device 1 is in the relaxed position, the fixation units 20 can be activated, whereby the fixation unit 20 projects in the radial direction in relation to the tubular part 10. When the fixation unit 20 is projected so that the fixation units are fastened or anchored in the wall of the wellbore, i.e. the 25 formation, the formation fixation device 1 is said to be in an activated or set condition, as shown in Fig. 1b. Each fixation unit 20 comprises a first end 21 and a second end 22 movable in relation to one another in an axial direction of the tubular part 10 when the 30 tubular part is pressurised from within. During activation of the formation fixation device 1, the fixation units 20 are projected by moving the first end 21 a distance "d" towards the second end 22 which is fixed relative to the tubular part 10. As an alternative to the embodiments shown in Figs. la and 1b, the second end 22 could be moved towards the first end 21, or both ends could be moved towards 35 each other.

WO 2012/080486 PCT/EP2011/073100 8 In Fig. 2a, the fixation unit 20 is shown comprising a slotted liner 26 surrounding the tubular part 10. The slotted liner 26 has a first end 21 and a second end 22. The slotted liner 26 comprises a plurality of slots 25 forming members 23 connecting the first and second ends 21, 22. 5 As shown in Figs. 2b and 2c, each of the members 23 has bend initiators 24. The bend initiators 24 are arranged substantially in a middle part of each member 23, but may alternatively be arranged in other positions along the length of the members 23. In Fig. 2c, the bend initiators 24 are indentations, but may also be 10 slots or folds or any other suitable initiators for initiating and/or controlling the bending of the members 23. By having bend initiators 24, the bending of the members 23 is controlled to occur at the position of the bend initiators and the force required to initiate the bending is substantially reduced. 15 In Fig. 3, the members 23 of the slotted liner 26 are shown in its bent and projected position when the formation fixation device 1 is in the set or activated condition. The members 23 are projected by moving the first end 21 a distance "d" towards the second end 22, thereby inducing a force in the members and initiating the bending of each member, and thus the projection of the fixation unit 20 20. The members 23 may alternatively be projected by moving the second end 22 towards the first 21 end or by moving both ends 21, 22 towards each other. The tubular part 10 extends in the entire length of the formation fixation device 1, as indicated by the axial dotted lines shown in Fig. 2a. The formation fixation 25 device 1 is hollow and thus has a hollow cavity extending in the axial direction from one end to the other. In Figs. 2a and 3, the tubular part 10 is shown with protrusions 27 extending around the periphery of the tubular part 10. The protrusion 27 adjacent to the first end 21 of the fixation unit 20 has a hollow interior 28 into which the end 21 of the fixation unit 20 extends. The principle of 30 protrusions 27 having a hollow interior 28 is illustrated in Fig. 4. The first end 21 arranged inside the interior 28 of the protrusion 27 is formed as a piston part 30 acting in the hollow interior 28 functioning partly as a piston housing. The second end 22 is fixated in a recess formed by an edge 14 in the other protrusion 27, similar to what is shown in Fig. 6. Alternatively, the second end 22 may be fixed 35 to the tubular part 10 by welding or in any other way found suitable by a skilled person.

WO 2012/080486 PCT/EP2011/073100 9 The interior 28 of the protrusion 27, wherein the piston part 30 of first end 21 of the fixation unit 20 is arranged, constitutes a fluid passage 28 between the hollow interior 29 of the tubular part 10 and the piston part 30 of the first end 21. When the formation fixation device 1 is activated by pressurising a fluid in 5 the interior of the tubular part 10, the fluid is pushed through the fluid passage 28, thereby exerting a force on a surface 40 of the piston part 30. This force is directed into the members 23, whereby the members 23 is forced to project and the fixation unit 20 enters into the set position when the members press against and partly into the wall of the borehole. 10 Fig. 4 shows the fixation unit 20 comprising two pivotally connected members 31. One end of each member 31b is pivotally secured to the surface 11 of the tubular part 10, and the other end of each member 31a is pivotally connected to a piston part 30. When the piston part 30 moves towards a surface 41 of interior 28, the 15 angle between the members 31a and 31b is decreased, and the fixation unit 20 projects in the radial direction. Figs. 5a and 5b show a close-up of the first end 21 of the fixation unit 20. The first end 21 is positioned in the interior 28 of the protrusions 27, and seals 42 are 20 arranged in grooves in the outer surface of the piston part 30 between the first end 21 and the inner surfaces of the interior 28. The seals 42 create a fluid-tight connection and prevent the fluid inside the hollow interior 29 from flowing into the annulus surrounding of the formation fixation device 1 when the tubular is pressurised from within and prevent the formation fluid from flowing into the 25 tubular part 10 when the tubular part is no longer pressurised. In the solution shown in Figs. la and 1b, each seal is arranged on a piston part 30, and in the solution shown in Figs. 2a-3, the seals are arranged as circumferential seals on the inner and outer surfaces of the slotted liner 26. 30 The fixation unit 20 further comprises a locking mechanism 50 for fixating the fixation unit 20 in the projected and set position when the formation fixation device 1 has been activated. Figs. 5a and 5b show two different examples of a locking mechanism 50 which may be used with any of the above-mentioned embodiments of the formation fixation device 1. 35 Fig. 5a shows a locking mechanism 50. The exterior surface 11 of the tubular part 10 is serrated, threaded or toothed thereby forming a plurality of studs 51 WO 2012/080486 PCT/EP2011/073100 10 and intermediate grooves. The studs 51 are configured for engagement with a tooth 52 positioned on the piston part 30. As the piston part 30 is moved towards the surface 41, the tooth 52 shifts from engagement with one stud 51 to engagement with the subsequent stud 51 until the fixation unit 20 has reached 5 its set position. The locking mechanism 50 shown in Fig. 5b comprises a plurality of recesses 54 in the piston part 30. A spring-loaded stud 53 arranged in a recess in the tubular part 10 is pushed into engagement with the recesses 54 of the piston part 30. As 10 the piston part 30 is moved towards the surface 41, the spring-loaded stud 53 shifts from engagement with one recess 54 to engagement with the subsequent recess on the piston part 30. In the solution shown in Figs. la and 1b, each piston part 30 comprises a locking 15 mechanism 50, and in the solution shown in Figs. 2a-3, the locking mechanism comprises several spring-loaded studs 53 arranged around the periphery of the tubular part 10 in connection with circumferential recesses 54 on the inner surface of the slotted liner 26. 20 It will be evident for a person skilled in the art that such a locking mechanism 50 may be designed in a number of other ways, e.g. as a mechanical locking mechanism, an electro-mechanical locking mechanism, etc. In the solution shown in Figs. la and 1b, the fixation unit 20 is arranged in a 25 recess 12 in the tubular part 10, as shown in Fig. 6. The first end 21 of the fixation unit 20 is formed as a piston part 30 and is arranged between the tubular part 10 and an internal wall 13 thereof. The second end 22 is fixated by an edge 14 forming a recess. Alternatively, the second end 22 may be fixed to the tubular part 10 by for example welding. Still referring to Fig. 6, a number of bend 30 initiators 24 are shown both on the outside and inside of the fixation units 20. The bend initiators 24 are arranged substantially in the middle part of the fixation unit 20, as described above, but also adjacent to the ends 21, 22 of the fixation unit 20. The bend initiators 24 are formed as indentations, but may also be slots or folds. By having bend initiators 24, the bending of the members 23 is 35 controlled to occur at the position of the bend initiators and the force required to initiate the bending is substantially reduced.

WO 2012/080486 PCT/EP2011/073100 11 It will be evident for a person skilled in the art that several other solutions may be conceived by combining the above described embodiments. For example, a pivotally mounted piston part 30 may be used in combination with the slotted liner 26. The piston part 30 in the solution shown in Fig. 4 may also be integrated 5 with the member 31a. Further, the fixation unit 20 may be arranged in recesses in the tubular part 10 or on the outside of the tubular part in connection with protrusions 27 irrespective of whether the fixation unit comprises a slotted liner 26 or linked members 31a, 31b. The fixation unit 20 may also be constructed with both ends 21, 22 movable in relation to the tubular part 10. 10 Having described the structural features, the functionality and use will be described in further detail below. Starting from the unset condition, e.g. as shown in Fig. 2a, the formation fixation 15 device 1 is activated by pressurising the hollow interior 29 of the tubular part 10. The hollow interior 29 may be pressurised by injecting a fluid, such as a fluid present in oil or gas wells downhole, drilling fluid or any other fluid supplied from the surface of the well. When a fluid is injected and pressurised, it flows into the fluid passage 28 and exerts a force on the surface 40 of the fixation unit 20. The 20 magnitude of the force exerted on the piston part 30 depends on the surface area of the surface 40 and the pressure of the fluid inside the formation fixation device 1. To project the fixation unit 20, the force exerted on the surface 40 must exceed the force exerted on the fixation unit 20 by the formation pressure in the annulus 70 surrounding the formation fixation device 1. The force exerted on the 25 surface 40 must also be sufficient for members 23, 31a, 31b to penetrate the formation. In Fig. 5a, the pressurised fluid moves the piston part 30 towards the surface 41 of the interior 28, away from its initial position. The piston part 30 can only move 30 in one direction due to the locking mechanism 50 preventing backwards moving. As the piston part 30 moves, the fixation unit 20 is gradually projected radially. When the fixation unit 20 hits the walls or formation of the wellbore, it will gradually dig into the formation and anchor the formation fixation device 1. Depending on the characteristics of the formation, the fixation unit 20 will dig 35 more or less into the formation. The projection of the fixation unit 20 stops when the force exerted on the fixation unit 20 by for example formation sand or rock exceeds the force exerted by the pressurised fluid inside the formation fixation WO 2012/080486 PCT/EP2011/073100 12 device 1. Alternatively, the projection stops when the piston part 30 abuts the surface 41. The formation fixation device 1 may be used either alone or in combination with 5 any device or structure to be secured in an open-hole wellbore. Now referring to Fig. 7a, the formation fixation device 1 is used in combination with casing elements 64 and one or more annular barriers 63 in a casing assembly 80 or casing string. Casing elements 64, annular barriers 63 and one or more formation fixation devices 1 are assembled into a casing string at the surface, e.g. by 10 screwing them together, and are lowered into the wellbore. When the formation fixation device 1 is used in combination with an annular barrier 63, the formation fixation device 1 is positioned right next to the annular barrier. This is done to secure in the best possible way that the position of the annular barrier 63 is fixed in the wellbore by the formation fixation device 1. The formation fixation device 15 may also be used when fixating a liner hanger. When in the desired position, one or more formation fixation devices 1 is/are activated to secure the casing assembly 80 in the wellbore. When activated, the fixation units 20 of the one or more formation fixation devices 1 project radially 20 and engage with the walls of the wellbore. Depending on the material composition of the formation surrounding the wellbore, the degree of penetration of the fixation units 20 of the walls varies. This way, the fixation units 20 secure the formation fixation device 1 and attached casing elements 64 in the wellbore. Aside from securing the casing, the formation fixation device 1 contributes to 25 centralising the casing elements 64 in the wellbore. The one or more formation fixation devices 1 may be activated by injecting a fluid in a number of different ways. The fluid may be injected locally in a defined section of the casing assembly 80 comprising one or more fluid passages 28. 30 Local injection may be conducted by lowering a drill pipe 60 with circumferential packers into the casing assembly 80 and positioning the packers 61 on opposite sides of the one or more fluid passages 28. By injecting a fluid through the drill pipe 60 and into the hollow interior 29 between the packers 61, the fixation device 1 is pressurised and activated. Local injection may alternatively be done 35 by a well tool comprising a pump. Such a tool may be lowered into the casing assembly 80 and connected directly to the fluid passage 28. The well tool may WO 2012/080486 PCT/EP2011/073100 13 inject fluid already present in the well or fluid carried by the tool into the fluid passage 28. As an alternative to local injection, the entire casing assembly 80 may be 5 pressurised, as illustrated in Fig. 7b. In this embodiment, the casing assembly 80 is sealed in one end. The opposite end of the casing assembly 80 is connected to a drill pipe 60 via a connecting unit creating a seal between the drill pipe 60 and the casing assembly 80. The one or more formation fixation devices 1 is/are then activated by injecting a fluid into the entire casing assembly 80. Such injection of 10 fluid may also be used to simultaneously activate annular barriers 63 and thus expand expandable sleeves of the barriers. The formation fixation device 1 may be a permanent fixation device. By permanent is meant that the projection of the fixation unit 20 cannot be reversed 15 without destroying the functionality of the formation fixation device 1. The formation fixation device 1 can thus not be reused after having been activated or set for the first time. When the formation fixation device 1 has been activated and the fixation unit 20 has dug into the formation, the fixation unit is locked in the set position. When the fixation unit 20 has been set and the formation 20 fixation device 1 is in the activated condition, the pressure inside the formation fixation device does not have to be sustained. The formation fixation device 1 is permanently locked in the activated condition. By fluid or well fluid is meant any kind of fluid that may be present in oil or gas 25 wells downhole, such as natural gas, oil, oil mud, crude oil, water, etc. By a casing is meant any kind of pipe, tubing, tubular, liner, string etc. used downhole in relation to oil or natural gas production. Although the invention has been described in the above in connection with 30 preferred embodiments of the invention, it will be evident for a person skilled in the art that several modifications are conceivable without departing from the invention as defined by the following claims.

Claims

1. A formation fixation device (1) for securing a tubular in an open-hole wellbore, the formation fixation device (1) comprising: 5 - a tubular part (10) extending in an axial direction, the tubular part (10) having an exterior surface (11) and a hollow interior (29), - a fixation unit (20) arranged at the exterior surface (11) of the tubular part (10), the fixation unit having a first end (21) and a second end (22) movable in relation to one another in the axial direction, and 10 - a fluid passage (28) extending from the hollow interior to one of the ends (21, 22) of the fixation unit; wherein at least one of the ends (21, 22) of the fixation unit is moved when the tubular part is pressurised from within, forcing the fixation unit to project in a radial direction in relation to the tubular part, whereby the fixation unit enters 15 into a projected position.

2. A formation fixation device according to claim 1, wherein the fixation unit comprises a locking mechanism (50) for permanently locking the fixation unit in the projected position. 20

3. A formation fixation device according to claim 1 or 2, wherein the fixation unit comprises a slotted liner (26) having a plurality of members (23) connecting the first end and the second end, the members being projected in a radial direction in relation to the tubular part when the ends of the fixation unit are 25 moved towards each other.

4. A formation fixation device according to claim 3, wherein the slotted liner surrounds the tubular part. 30

5. A formation fixation device according to claim 3 or 4, wherein each of the members has a bend initiator (24), such as a transverse slot or fold, arranged substantially in a middle part of each member in the axial direction.

6. A formation fixation device according to claim 1 or 2, wherein the fixation 35 unit comprises two pivotally connected members (31). WO 2012/080486 PCT/EP2011/073100 15

7. A formation fixation device according to any of the preceding claims, wherein the fixation unit is arranged in a recess in the tubular part.

8. A formation fixation device according to any of the preceding claims, 5 wherein one of the ends of the fixation unit constitutes a piston part (30) comprising a surface (40) adapted for receiving a force induced by a pressurised medium contained in the hollow interior of the tubular part.

9. A formation fixation device according to any of the preceding claims, 10 wherein both ends of the fixation unit constitute a piston part comprising a surface adapted for receiving a force induced by a pressurised medium contained in the hollow interior of the tubular.

10. A formation fixation device according to any of the preceding claims, 15 wherein both ends of the fixation unit are movable in relation to the tubular part.

11. A formation fixation device according to any of the preceding claims, wherein the fixation device comprises a plurality of fixation units. 20

12. A downhole fixation system for securing a casing comprising a first end and a second end in an open-hole wellbore, the fixation system comprising: - the formation fixation device according to any of the claims 1-11, - a casing connected with the tubular of the formation fixation device, - one or more annular barriers comprising a tubular part and a surrounding 25 expandable sleeve, and - a pressure creating device fluidly connected to the hollow interior of the tubular part of the formation fixation device.

13. A downhole fixation system according to claim 12, wherein the pressure 30 creating device is a downhole tool adapted to be arranged in fluid connection with the fluid passage.

14. A downhole fixation system according to claim 12, wherein the pressure creating device is a pump positioned outside the wellbore. 35

15. A method of permanently fixating a tubular part in an open-hole wellbore, the method comprising the steps of: WO 2012/080486 PCT/EP2011/073100 16 - connecting the permanent formation fixation device according to any of the claims 1-11 with one or more casing elements, - positioning the formation fixation device at a predetermined location in an open-hole wellbore, and 5 - activating the fixation unit by applying a hydraulic pressure to one of the ends of the fixation unit, whereby the fixation unit engages with the sides of the wellbore.

16. Use of a formation fixation device according to any of the claims 1-11 for 10 fixating a tubular part in an open-hole wellbore.