A method and a centralizer system for centralizing a casing in a well bore

Abstract

A centralizer system and a method for centralizing a casing in a well bore before cementing of the casing in the well bore is disclosed, where the centralizer system comprises at least one centralizer which is adapted for mounting on the casing where the at least one centralizer comprises a receiving unit capable of receiving a wireless signal in form of a pressure wave and a wireless signal generator for generation and transmission of a wireless signal in form of a pressure wave which the receiving unit of the at least one centralizer is capable of receiving. The at least one centralizer is further configured such that the centralizer is activated for centralizing of the casing when the receiving unit receives a wireless signal transmitted by the signal generator.

Claims

1. Method for centralizing a casing in a well bore before cementing of the casing in the well bore, the method comprising the steps of: mounting at least one centralizer on the casing, the at least one centralizer comprising a receiving unit capable of receiving a wireless signal in form of a pressure wave, positioning the casing in the well bore at a desired position, providing a wireless signal generator for generation and transmission of a wireless signal in form of a pressure wave which the receiving unit of the at least one centralizer is capable of receiving, and transporting the signal generator down the well bore towards the casing and activating the signal generator such that the signal generator transmits the wireless signal and whereafter the receiving unit, on reception of the wireless signal, activates the at least one centralizer and the at least one centralizer centralizes the casing in the well bore.

2. Method according to claim 1, wherein a transport element is transported down the well bore, the transport element comprising the signal generator.

3. Method according to one of the claims 1-2, wherein the signal generator is triggered to start transmitting the wireless signal as the signal generator is approaching the casing or upon arrival at the casing.

4. Method according to claim 1, wherein the signal generator is triggered to start transmitting said wireless signal when the pressure in the well fluids surrounding the at least one transport element exceeds a predetermined value.

5. Method according to claim 1, wherein the signal generator is triggered to start transmitting said wireless signal when the temperature in the well fluids surrounding the at least one transport element exceeds a predetermined value.

6. Method according to claim 1, wherein the signal generator is mechanically triggered to start transmitting said wireless signal when the signal generator arrives at the casing.

7. Method according one of the claims 1-2, wherein the signal generator in the transport element continuously or intermittently transmits the wireless signal while being transported through the well bore.

8. Method according to claim 1, wherein a plurality of centralizers are provided in the well bore and that the centralizers are signally connected such that when the receiving unit of a first centralizer receives said wireless signal, the signal is forwarded to at least one of the remaining centralizers which will initiate centralizing of the casing on which it is mounted.

9. Method according to claim 1, wherein the pressure wave is a sound signal.

10. Method according to claim 1, wherein the transport element is pumped down the well bore by cement slurry.

11. Method according to claim 1, wherein transport element is a viper plug.

12. A centralizer system for centralizing a casing in a well bore before cementing of the casing in the well bore, the centralizer system comprising: at least one centralizer which is adapted for mounting on the casing, the at least one centralizer comprising a receiving unit capable of receiving a wireless signal in form of pressure waves, a wireless signal generator which is adapted for transport down the well bore and for generation and transmission of a wireless signal in form of a pressure wave which the receiving unit of the at least one centralizer is capable of receiving, and wherein the at least one centralizer is configured such that the centralizer is activated for centralizing of the casing when the receiving unit receives a wireless signal transmitted by the signal generator.

13. Centralizer system according to claim 12, wherein the centralizer system comprises a transport element, the transport element comprising the signal generator.

14. Centralizer system according to one of the claims 12-13, characterized in that the centralizer system comprises a pressure sensor comprised in the signal generator or the transport element, the signal generator being adapted to be activated when the pressure in the well bore exceeds a predetermined value.

15. Centralizer system according to one of the claims 12-14, characterized in that the centralizer system comprises a temperature sensor comprised in the signal generator or the transport element, the signal generator being adapted to be activated when the temperature in the well bore exceeds a predetermined value.

16. Centralizer system according to one of the claims 12-14, characterized in that the at least one centralizer and/or the signal generator and/or the transport element is provided with a mechanical device which activates the signal generator when the signal generator arrives at the casing.

17. Centralizer system according to one of the claims 12-15, characterized in that the centralizer system comprises a plurality of centralizers and that the centralizers are signally connected such that when the receiving unit of a first centralizer receives said wireless signal, the signal is forwarded to at least one of the remaining centralizers which will initiate centralizing of the casing on which it is mounted.

18. Centralizer system according to one of the claims 12-17, characterized in that the pressure wave is a sound signal.

19. Centralizer system according to one of the claims 12-18, characterized in that the transport element is a viper plug.

20. Use of a wireless signal to initiate the centralizing of a casing in a well bore before cementing of the casing, wherein the wireless signal is in the form of a pressure wave.

21. Use of a wireless signal according to claim 24, wherein the pressure wave is a sound wave.

Description

[0041] In the following different embodiments of the present invention will be described with reference to the drawings where

[0042] FIG. 1 schematically illustrates a first embodiment of a centralizer mounted on a casing and in an active position.

[0043] FIG. 2 schematically illustrates the first embodiment of the centralizer in an inactive position and mounted on a casing which is positioned in a well bore.

[0044] FIG. 3 schematically illustrates the first embodiment of the centralizer shown in FIG. 2 in an active position.

[0045] FIG. 4 schematically illustrates a second embodiment of the centralizer in an inactive position and mounted on a casing.

[0046] FIG. 5 schematically illustrates the second embodiment of the centralizer shown in FIG. 4 in an active position.

[0047] FIG. 6 schematically illustrates the centralizer system with the signal generator arranged in a transport element.

[0048] FIG. 7 schematically illustrates a variant of the centralizer system where the transport element is provided with a pressure sensor and a temperature sensor.

[0049] FIG. 8 schematically illustrates a variant of the centralizer system which is a combination of the variants shown in FIGS. 6 and 7.

[0050] The embodiments of the present invention described in detail below are similar and the same reference numbers are used on the drawings for the same features of the two embodiments. It should be understood that the embodiments shown in the figures are schematically drawn and only the features necessary for the understanding of the invention are included in the figures. The first five figures show two possible embodiments of the centralizer, while the last two figures relates to the centralizer system.

[0051] Referring to FIGS. 1-3 there is shown a first embodiment of a centralizer 12 which comprises a centralizer body 18 which is mounted on a casing 14. The centralizer 12 is mounted on the casing before the casing is lowered into the well bore 15, for example by clamping, bolting, welding or any other suitable ways of attaching the centralizer body 18, and thereby the centralizer 12, to the casing 14. When the casing with the centralizer 12 is lowered into the well bore 15, the centralizer is in an inactive position as shown in FIG. 2. When the casing is in the desired position in the well bore, the centralizer can be actuated and then assumes an active position as shown in FIG. 3 were the centralizer 12 has centralized the casing 14 in the well bore 15.

[0052] The centralizer 12 comprises at least one, but preferably three or more centralizing elements 20 with a first end portion 21 and a second end portion 22, and an actuator 36 comprising an actuator device 37. The centralizing elements 20 are preferably spaced equally around the centralizer body 18 in a circumferential direction. The actuator actuates a radial or partially radial movement of the centralizing elements 20 as will be explained below. A movement of the centralizing elements 20 in a partially radial direction means that the movement of the centralizing element 20 has a radial component as well as an axial component relative to the longitudinal axis A of the casing 14.

[0053] The centralizer further comprises a first link element 24 with a first end portion 25 and a second end portion 26 and a second link element 28 with a first end portion 29 and a second end portion 30. The first end portions 21 of the centralizing elements 20 are rotatably connected to respective first end portions 25 of the first link elements 24, and the second end portions 22 of the centralizing elements 20 are rotatably connected to respective second end portions 29 of the second link elements 28.

[0054] The second end portion 25 of the first link element 24 is rotatably connected to the centralizer body 18 or to the actuator device 37. The second end portion 30 of the second link element 28 is rotatably connected the centralizer body 18 or to the actuator device 37. Either one or both of the second end portion 25 of the first link element 24 and the second end portion 30 of the second link element 28 is/are connected to the actuator device 37.

[0055] For centralizing of the casing the actuator 36 actuates the actuator device 37 which causes the axial distance between the second end portion 25 of the first link element 24 and the second end portion 30 of the second link element 28 to be reduced.

[0056] The actuating device 37 may for example be formed as a piston/cylinder arrangement were the second end portions 25, 30 of the first link element 24 and the second link element 28 are connected respectively to the piston and the cylinder. When the length of the piston/cylinder arrangement is reduced, the centralizing element 20 will be forced out and will engage with the wall 16 of the well bore.

[0057] The actuating device 37 may also be in the form of a rotatable shaft with left and right hand screw threads which are in engagement with the second end portions 25, 30 of the first link element 24 and the second link element 28 respectively in a similar way to a rack and pinion gear. When the shaft is rotated such that the second end portions 25, 30 of the first link element 24 and the second link element 28 are moved towards each other, the centralizing element 20 is moved in a radial direction relative to the axis A and engages with the wall 16 of the well bore 15, whereby the casing is centralized.

[0058] Another option to effect a radial or a partially radial movement of the centralizing elements 20 shown in FIGS. 1-3 would be to use a pair of wedge shaped surfaces which are adapted for axial movement which will simultaneously cause a radial movement. Each centralizing element 20 may be formed with a first wedge surface which is arranged with an acute angle relative to the longitudinal axis A, and the centralizer body 18 may be formed with a corresponding second wedge surface. When the centralizing elements 20 are moved in the axial direction by the actuator device 17, the centralizing elements will simultaneously be moved in a radial direction due to the wedging effect until they engage with the wall 16 of the well bore 15. In order to provide only radial movement of the centralizing element 20, a separate wedge element could be arranged between the centralizing element 20 and the surface of the centralizer body which is inclined relative to the longitudinal axis A.

[0059] The centralizer system 10 further comprises a receiving unit 40. The receiving unit 40 is signally connected to the actuator 36 such that the receiving unit is capable of sending a signal to the actuator 36 which will cause the actuator device 37 to actuate the centralizing elements 20 so that the casing 14 is centralized in the well bore 15. The actuator device 40 may be connected to actuator 36 by means of a signal cable or by wireless communication such as blue tooth.

[0060] In FIGS. 4-5 a second embodiment of the centralizer is shown wherein the centralizing element 20 is made of a flexible material such as spring steel. In this embodiment the first end portion 21 and the second end portion 22 of the centralizing element 20 are preferably rotatably connected to the actuator device 37. The actuator device 37 may be a piston/cylinder arrangement or a rotatable shaft working in a similar way to a rack and pinion gear as explained above. The length of the actuator device 37 can thereby be reduced which forces the flexible centralizing element 20 to bend outwards and engage with the wall 16 of the well bore 15. As with the first embodiment of the present invention, there are provided at least one such flexible centralizing element, but preferably three or more flexible centralizing elements 20 are provided equally spaced around the circumference of the centralizer body 18. As the flexible centralizing elements 20 engage with the wall of the well bore 15, the casing 14 on which the centralizer 12 is attached, is centralized in the well bore 15. The rest of the second embodiment of the invention, such as the receiving unit 40, is same as the first embodiment of the invention shown in FIGS. 1-3 and the description of the common features are not repeated here.

[0061] The centralizer system shown in FIGS. 6-8 illustrates the centralizer system 10 where a centralizer 12 of the same type as the centralizers described above, is mounted on the casing 14. As shown in FIG. 6, a transport element 43 is provided with a signal generator 42 which is capable of generating and transmitting a wireless signal in the form of a pressure wave, preferably a sound wave. The signal generator 42 may be turned on before the signal generator is moved down the well such that the wireless signal is transmitted constantly or intermittently as the transport element 43 moves down the well towards the casing 14. In FIG. 6, the casing is provided with one or more stop elements 13, for example one or more casing shoes, which a transport element 43 hits when the transport element arrives at the casing.

[0062] The signal generator may be turned on by a partly or completely mechanical device (not shown in the figures). One or more of the stop elements 13 or, more preferably, the transport element 43 may be provided with a mechanical element such as a spring-loaded lever, a button-like element, a switch or another type of mechanical device that is suitable for turning on the signal generator. As the lever is pivoted or the button-like element is pressed in when the transport element 43 hits the stop elements 13, the signal generator 42 may be turned on directly or the movement of the lever, the button-like element or the switch may generate a signal that in turn activates the signal generator. When the receiving unit 40 subsequently detects the wireless signal transmitted by the signal generator 42, the actuator 36 is activated and the centralizing of the casing 14 is performed.

[0063] The receiving unit 40 further comprises a control unit (not shown on the figures) which transmits a signal to the actuator 36 for actuation of the actuator device 37 as soon as the antenna or vibration/sound sensor 41 detects the wireless signal transmitted by the signal generator 42.

[0064] In FIG. 7 a variant of the centralizer system 10 is shown. The casing 14 is in this embodiment not provided with stop elements 13. In stead the transport element is provided with one or more sensors which are capable of measuring one or more physical parameters of the transport element's surrounding environment as the transport element is moved down the well. Typically such physical parameters could be the pressure and the temperature in the fluid surrounding the transport element. The temperature and the pressure of the well fluids in a well typically increases with the depth of the well, and for any given well, the signal generator may be set to start operating when the temperature and/or the pressure in the fluid surrounding the transport element reach a predetermined value. To monitor the temperature and/or the pressure the transport element 43 may therefore be provided with a temperature sensor 44 and/or a pressure sensor 45 which is capable of measuring the temperature and pressure of the fluid surrounding the transport element 43 respectively. The embodiment of the transport element 43 shown in FIG. 7 is provided with both a temperature sensor 44 and a pressure sensor 45, but could have been provided with only a temperature sensor 44 or only a pressure sensor 45 depending on the situation. However, providing the transport element with both a temperature sensor and a pressure sensor will provide a considerably reduced risk that the signal generator 43 is not activated.

[0065] In FIG. 8 a variant of the centralizer system 10 is shown where the casing 14 is provided with stop elements 13, typically a casing shoe. The centralizer system may therefore be provided with a mechanical device which starts the signal generator 42 when the transport element 43 hits the stop elements in the same way as explained in detail above. The transport element 43 is also provided with sensors 44, 45 which are capable of measuring physical parameters of the fluid surrounding the transport element, for example temperature and/or pressure, as explained above. The signal generator 42 of the centralizing system 10 shown in FIG. 8 can therefore be activated by the temperature in the fluid surrounding the transport element 43 reaching a predetermined value or the pressure in the fluid surrounding the transport element 43 reaching a predetermined value or mechanically when the transport element 43 hits the stop elements 13 in the casing 14.

[0066] When the casing is cemented, the cement slurry is usually preceded by a viper plug which separates the cement slurry 51 from the well fluids 50 in front of the cement slurry. A viper plug may therefore conveniently be used as a transport element for the signal generator. The signal generator 42 is integrated in the viper plug which will protect the signal generator from environmental hazards and prevent the signal generator from getting damaged as it is transported or pushed down the well by the cement slurry towards the casing 14 with the casing centralizer 12.

[0067] The receiving unit 40 further comprises a control unit (not shown in the figures) which transmits a signal to the actuator 36 for actuation of the actuator device 37 as soon as the antenna 44 detects and reads (identifies).

[0068] In use, the centralizer system 10 works as follows. A centralizer 12 as shown in FIGS. 1-3 or FIGS. 4-5 is attached to the casing 14 which is to be centralized in the well bore 15. The casing 14, together with the attached centralizer 12 in an inactive position is lowered to the desired position in the well bore 15. This is shown in FIG. 2 where the casing 14 with the centralizer 12 in the inactive position is not centralized in the well bore 15. A signal generator 42, which is moved down the well in a direction 48, preferably by the cement slurry which is later used to cement the casing to the formations in the well bore, generates and transmits a wireless signal in the form of a pressure wave, such as a sound wave. The pressure waves are detected by the receiving unit 40 which then sends a signal to the actuator 36 whereby the centralizing elements 20 are moved radially until they are in engagement with the wall 16 of the well bore 15. This is shown in FIG. 3 where the centralizer 12 is in an active position and the casing 14 is positioned centrally in the well bore 15. When the casing 14 has been centralized by the centralizer 12, cement 51 may be flowed through the casing 14 and up the annulus between the casing and the formations for cementing of the casing as indicated in FIG. 3.

[0069] For all embodiments of the invention, the centralizer system is based on the fact that the receiving unit 40 and the signal generator 42 are cooperatively configured, i.e. the signal generator generates and transmits a wireless signal, in the form of a pressure wave such as a sound wave, which the receiving unit is capable of receiving. The receiving unit 40 may be provided with an antenna 41 or another device or sensor capable of detecting the wireless signal transmitted by the signal generator 42. When the signal generator 42 is within a distance of the receiving unit 40 where the receiving unit 40 is capable of detecting the wireless signal that is transmitted by the signal generator, the receiving unit will transmit a signal to the actuator 36 so that centralizing of the casing 14 is carried out.

[0070] It should also be noted that wireless signal, especially pressure waves, are capable of travelling over fairly large distances. The signal generator 42 may therefore be mounted above the well (not shown in the figures), for example on the well head, where the signal generator 42 generates a wireless signal, preferably a pressure wave, for example a sound wave, that travels down the well. When the receiving unit 40 detects the wireless signal that the signal generator transmits, the actuator 36 is activated and the centralizing elements moves radially and centralizes the casing 14 in the well bore. It should be mentioned that for the embodiments of the present invention where the

[0071] The present centralizer system 10 is described above with various ways of ensuring that the signal generator 12 is activated such that the casing centralizer is activated and the casing 14 is centralized before the casing 14 is cemented in its position in the well bore. It should be understood that the signal generator 42 may be transported down the well, either integrated in a transport element 42, such as a viper plug, or as a separate entity, such that the wireless signal, for example in the form of pressure waves produced by the signal generator 42 are transmitted down the well. When the signal generator 42 is transported down the well, it may be operating and transmitting pressure waves from the moment it is entered the well at the top of the well, or the signal generator 42 may be activated in different ways as the signal generator approaches the casing 14, not only by using temperature sensors, pressure sensors or mechanical devices as explained above, but also other feasible devices such as an inductive coil.

[0072] It should be understood that the claimed invention is not limited to the embodiments described above, since many modifications may be carried out within the range of the claims. The scope of the claimed invention is thus limited only by the claims.