The present invention relates to a method and a system for centralizing of a casing in a well bore before the casing is cemented in the well bore.

During drilling of a hydrocarbon well, the bore hole is at least in part provided with a casing which is cemented to the surrounding formations of the well bore. When a casing is cemented, cement is flowed through the casing and up through the annulus which is formed between the casing and the surrounding formations. Before cementing of a casing starts, the casing is preferably centralized, i.e. positioned centrally in the well bore. The centralizing of the casing improves the cementing of the casing preventing that the cement does not stick properly to the outside of the casing or the surrounding formations and that canals with polluted liquid is formed within the cement.

To centralize the casing before it is cemented to the formations, a centralizer is used. There are a number of centralizers available on the market. They do, however, have the problem that those centralizers which provide a good centralizing o the casing also hinders the cement to flow past the centralizer which may cause problems with the cementing job due to too high hydraulic pressure loss.

The objective of the present invention is therefore to provide an method and a system for centralizing of the casing before the cementing takes place which does not have the above mentioned problems.

These objectives are fulfilled with a method for centralizing a casing in a well bore as defined in claim 1 and a casing centralizer system for centralizing a casing in a well bore as defined in claim 7. Further embodiments of the invention are defined in the dependent claims.

The casing centralizer system comprises a casing centralizer for centralizing of the casing and at least one trigger device. The casing centralizer comprises a casing centralizer body which is mountable on a casing, for example by bolts, by welding or by any other suitable fastening methods. The casing centralizer further comprises at least one, but preferably three or more centralizing elements which are attached to the casing centralizer body and which are movable in radial or partially radial direction such that the centralizing elements engage with the formations in the well bore and thereby centralizes the casing before the casing is cemented in the bore hole.

The casing centralizer system further comprises an activator device which is mounted to or is embedded in the casing centralizer body. The at least one trigger device is of a relatively small size such that at least one, but preferably a plurality of such trigger devices can be put into a fluid which is flown through well bore and the casing and up the annulus outside the casing. The fluid thereby conveys the at least one trigger device through the casing and up through the annulus formed between the casing and the radially outer side of the casing. The activator device is signally connected to the actuator, either with signal cables or by means o wireless communication such as blue tooth. The activator device and the trigger device are electrically, magnetically or electro-magnetically cooperatively configured. When a trigger device is conveyed with a fluid through the casing and up the annulus, and thereby passes by the activator device, the activator device is triggered and sends a signal to the actuator which will actuate the centralizing elements which will be moved in a radial or partially radial direction relative to the casing and engage with the formations of well bore such that the casing is centralized in the well bore.

Thus, the activator device may be triggered by a trigger device flowing through the casing or a trigger device flowing up through the annulus. Thereafter, cement is flowed through the casing for cementing of the casing. If desired the activator device or the actuator may also be configured to send a signal, either through a communication cable or wirclessly, to a control central when the centralizing elements have been actuated, whereby an operator is informed that the casing has been centralized and the casing may be cemented in the well bore.

Thus, there is provided a method for centralizing a casing in a well bore before cementing of said casing in the well bore, wherein a casing centralizer is mounted on the casing to be centralized, which casing centralizer comprises at least one centralizing element which is movable in a radial or partially radial direction relative to the casing when the casing centralizer is mounted to the casing, at least one actuator comprising an actuator device connected to the at least one centralizing element for movement of the at least one centralizing element in said radial or partially radial direction, and an activator device which is signally connected to the actuator. The method further comprises the following steps:

- the casing is positioned in the well bore at a desired position;

at least one trigger device is put into a fluid which is being flowed through the casing and the annulus formed between the casing and the well bore thereby conveying the at least one trigger device through the casing and/or the annulus together with the fluid,

wherein the at least one trigger device and the activator device are electrically, magnetically or electro-magnetically cooperatively configured such that when the at least one trigger device passes by the activator device as the at least one trigger device is flowed through the casing or through the annulus, the activator device is triggered to generate a signal for actuation of the at least one actuator whereby the at least one centralizing element is moved radially or partially radially for engagement with the well bore and centralizing of the casing in the well bore.

That the at least one trigger device and the activator device are electrically, magnetically or electro-magnetically cooperatively configured should be understood such that a trigger device and the activator device communicate electro- magentically at some level as the trigger de ice moves past the activator device. The trigger devices may for example create disturbances in electric and/or magnetic fields which are detected by the activator device or the trigger devices and the activator device may communicate by sending and receiving signals, preferably by the trigger devices transmitting signals which are detected and read by the activating device. Since the diameter of casings are generally less than one meter, it will be sufficient if the activator device and the trigger devices are able to

communicate when they are within a range of a few meter from each other in the well bore, for example when the activator device and the trigger devices are within a range of 5-10 meters from each other. The trigger device may be provided with a transmitter capable of transmitting an electro-magnetic signal and the activator device may be provided with a receiver capable of receiving said electro-magnetic signal such that a trigger device comprising said transmitter is detected when the trigger device is passing by the activator device, i.e. when the trigger device is passing through the casing or through the annulus on the outside of the casing.

The trigger device may be provided with an RFID-chip and the activator device may be provided with an antenna for detection and reading of the trigger device comprising an RFID-chip when the trigger device passes by the activator device, i.e. when the trigger device is passing through the casing or through the annulus on the outside of the casing. Instead of an RFID-chip, the trigger device may be provided with a magnet and the activator device may be provided with a detector which is capable of detecting a trigger device with a magnet when said trigger device is passing by the activator device. The activator device may for example comprise an electric circuit in which an electric current is induced when the magnet with its magnetic field is conveyed through the casing and passes by the activator device.

The induced electric current is registered and triggers the activating device to send a signal to the actuator for actuation of the casing centralizer.

The activating device may be signally connected, directly or indirectly via a control unit, to the at least one actuator for actuati on of the at least one centralizing clement with a conventional signal cable or cables or through wireless communication such as blue tooth.

Preferably a plurality of trigger devices are put into the fluid being flowed through the casing to ensure that the activating device is triggered and a signal is sent to the actuator for actuation of the at least one centralizing element . The casing centralizer may be provided with three or more centralizing elements which are preferably equally spaced around the casing centralizer in a

circumferential direction. After the casing has been centralized, cement is flowed through the casing and into the annulus for cementing of the casing to the surrounding formations of the well bore.

There is also provided a casing centralizer system for centralizing a casing in a well bore before cementing of said casing in the well bore, the casing centralizer system comprising a casin centralizer and at least one trigger device which is capable of being conveyed with a fluid through the casing and an annulus formed between the casing and the formations of the well bore, wherein the casing centralizer comprises at least one centralizing element which is, when the casing centralizer is mounted on the casing, movable in a radial or partially radial direction relative to the casing for engagement with the well bore; at least one actuator comprising an actuator device which is connected to the at least one centralizing element for radial or partially radial movement of the at least one centralizing element; an activator device which is signally connected to the at least one actuator, wherein the at least one trigger device and the activator device are electrically, magnetically or electro- magnctically cooperatively configured such that when the at least one trigger device passes by the activator device as the at least one trigger device is flowed through the casing or the annulus, the activator device sends a signal for actuation of the actuator device whereby the at least one centralizing element is moved radially or partially radially for engagement with the well bore. The casing is thereby centralized relative to the well bore.

The at least one trigger device may comprise an RFID-chip and the activator device may comprise an antenna capable of receiving and reading signals transmitted by the RFID-chip. Alternatively, the at least one trigger device may comprise a magnet having a magnetic field and the activator device may comprise a receiver device which is capable of detecting the magnetic field of said magnet as the at least one trigger device is conveyed with a fluid through the casing. The activator device may for example comprise an electric circuit in which an electric current is induced when a trigger device comprising a magnet with its magnetic field is conveyed through the casing and passes by the activator device. The induced electric current or voltage is registered and triggers the activating device to send a signal to the actuator for actuation of the casing centralizer.

In an embodiment the at least one centralizing element may be rigid and movable in a radial or partially radial direction for engagement with the formations in the well bore. The centralizer system may further comprises a first link element and a second link element which are rotatably connected to the at: least one centralizer element. One or both of the first link clement and the second link element should be rotatably connected to the actuator device of the at least one actuator. Alternatively, the at least one centralizing element may be radially flexible for engagement with the formations in the well bore. Preferably the at least one centralizing element comprises a first end and a second end where one or both of the first end and the second end is/are connected to the actuator device of the at least one actuator.

The actuator device of the at least one actuator may comprise a piston/cylinder arrangement. Alternatively the actuator device of the at least one actuator may comprise a rotatable shaft with left and right hand screw threads which are in engagement with respectively the first link element and the second link clement. Preferably the casing centralizer comprises three or more centralizing elements.

These centralizing elements are preferably equally spaced around the circumference o the casing centralizer body.

The casing centralizer system may comprise a control unit which is signally connected, either through signal cables or through wireless communication, to the activator device and to the actuator. When the activator detects that a trigger device is passing through the casing or the annulus, a signal is sent to the control unit which in turn sends a signal to the actuator for actuation of the centralizing elements. The control unit may be a separate entity or may be integrated with the activator device. In the following two embodiments of the present invention will be described with reference to the drawings where

Figure 1 schematically illustrates a first embodiment of a casing centralizer in an active position.

Figure 2 schematically illustrates a first embodiment of a casing centralizer in an inactive position arranged on a casing in a well bore.

Figure 3 schematically illustrates a first embodiment of a casing centralizer in an active position arranged on a casing in a well bore.

Figure 4 schematically illustrates a second embodiment o a casing centralizer in an inactive position arranged on a casing.

Figure 5 schematically illustrates a second embodiment o a casing centralizer in an active position arranged on a casing.

The two embodiments described in detail below are similar and the same reference numbers arc 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. Referring to Figures 1 -3 there is shown a first embodiment of casing centralizer 12 comprising a casing centralizer body 18 which is mounted on a casing 14. The casing centralizer 1 2 is mounted on the casing before the casing is lowered into the well bore 15 (see Figures 2-3), for example by bolting, welding or any other suitable ways of attaching the casing centralizer body 18, and thereby the casing centralizer 12, to the casing 14. When the casing with the casing centralizer 12 is lowered into the well bore 15, the casing centralizer is in an inactive position as shown in Figure 2. When the casing is in the desired position in the well bore, the casing centralizer is actuated and assumes an active position as shown in Figure 3 were the casing centralizer 12 has centralized the casing 14 in the well bore 15.

The casing 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 casing 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.

The casing centralizer further comprises a fir t 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 o 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 o the second link elements 28.

The second end portion 25 of the first link clement 24 is rotatably connected to the casing centralizer body 18 or to the actuator device 37. The second end portion 30 of the second link element 28 is rotatably connected the casing 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.

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.

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. 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 o the well bore 15, whereby the casing is centralized.

Another option to effect a radial or a partially radial movement of the centralizing elements 20 shown in Figures 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 casing 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 casing centralizer body which is inclined relative to the longitudinal axis A.

The casing centralizer system 10 further comprises an activator device 40 and at least one, but preferably a plurality of trigger devices 44. The activator device 40 is signally connected to the actuator 36 such that the activator device 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.

The activator device 40 and the trigger devices 44 are magnetically, electrically or electro -magnetically cooperatively configured such that when a trigger device 44 is sufficiently close to the activator device 40, i.e. as the trigger device passes through the casing on which the casing centralizer 12 is attached or up through the annulus between the casing and the well bore, the activator device will detect the presence of the trigger device 44 and transmit a signal to the actuator 36 so that centralizing of the casing 14 is carried out.

That the at least one trigger device 44 and the activator device 40 are electrically, magnetically or electro-magnetically cooperatively configured should be understood such that a trigger device and the activator device communicate electro- magnetically at some level as the trigger device moves past the activator device within the casing or up the annulus between the casing and the well bore. The trigger devices may for example create disturbances in electric and/or magnetic fields which are detected by the activator device or the trigger devices and the activator device may communicate by sending and receiving signals, preferably by the trigger devices transmitting signals which are detected and read by the activating device. Since the diameter of casings are generally less than one meter, it will be sufficient if the activator device and the trigger devices are able to communicate when they are within a range of a few meters, for example within a range of 5-10 meters, from each other in the well bore.

In an embodiment of the invention the trigger device 44 comprises an RFID-chip and the activator device 40 comprises an antenna or reader 41 which is capable of detecting and reading the signals transmitted by the RFID-chip. The RFID-chip may be of the passive type where the energy in the electro-magnetic waves transmitted by the antenna 41 is used to power the RFID-chip which then transmits information back to the activator device 40 which is read by the antenna 41 . The RFID-chip may also be provided with a battery which provides the energy for the RFID-chip to transmit its signal intermittently or continuously which is read by the antenna 41 when the trigger device 44 passes through the casing 14 or through the annulus 15 formed between the formations 17 and the casing 14. The trigger device is preferably designed to be fluid tight such that it is conveyable with a fluid being flowed through the well bore and the casing.

The activating device 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 44 detects and reads (identi fies) a trigger device 44 with an RFID-chip passing through the casing 14.

In Figures 4-5 a second embodiment of the present invention 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 easing centralizer body 18 in. As the flexible centralizing elements 20 engage with the wall of the well bore 15, the casing 14 on which the casing centralizer 12 is attached, is centralized in the well bore 15. The rest of the second embodiment of the in vention, such as the activator device 40 and the trigger device 44, is same as the first embodiment of the invention shown in Figures 1-3, and is therefore not repeated here.

In use, the casing centralizer system 10 works as follows. A casing centralizer 12 as shown in Figures 1-3 or Figures 4-5 is attached to the casing 14 winch is to be centralized in the well bore 15. The casing 14, together with the attached casing centralizer 12 in an inactive position is lowered to the desired position in the well bore 1 5. This is shown in Figure 2 where the casing 14 with the casing centralizer 12 in the inactive position is not centralized in the well bore 15. Thereafter at least one, but preferably a plurality of trigger devices 44 are put into a fluid 50 which is circulated in the well as indicated by arrow 48 on Figures 2 and 3. A sufficient number of trigger devices are put into the circulating fluid 50 so that one can be reasonably sure that at least one of the trigger devices 44 survives as the trigger devices are conveyed by the circulating fluid through the well down to the casing 14 with the attached casing centralizer 12. As one or more of the trigger devices 44 passes by the activating device 40, either as they pass through the casing or as they pass through the annulus formed between the casing and the formations of the well bore, they are detected by the activating device 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 Figure 3 where the casing 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 casing 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 Figure 3.

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