Patent Publication Number: US-9416607-B2

Title: Downhole guiding tool

Description:
This application is the U.S. national phase of International Application No. PCT/EP2010/0070835 filed Dec. 29, 2010, which designated the U.S. and claims priority to EP Patent Application No. 09180926.9 filed Dec. 30, 2009, the entire contents of each of which are hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present invention relates to a downhole tool for guiding a device into a side track of a borehole, the tool having a tool axis and comprising a tool housing connected to an energy source. The invention further relates to a method for moving the downhole tool into a side track. 
     BACKGROUND 
     A device for guiding a borehole servicing tool string into a side track of a borehole is known from U.S. Pat. No. 5,415,238. The device disclosed in this patent is provided with a guiding nose for moving freely past a point of wall separation between the primary borehole and the lateral, and hence, into the lateral. The device is in one embodiment provided with two moving areas/joints; one for providing a rotation of the device around its own centre axis, and another—a hinge—in which the device is displaced out of the axial alignment with the housing. 
     These two moving joints make the device more complicated, and due to the rotation around the axis, it is not possible to move wires past this joint and on to the next joint—the hinge—as this will cause twisting of the wires. Therefore, the movement of the device can only take place by incorporating several power sources in the device; one for moving the device around its centre axis, and another for moving the device in the lateral direction. Furthermore, it is not possible to have different helping tools arranged in relation to the guiding device as these helping tools also require power and can, as a consequence of that, only be placed before reaching the first joint and not at the tip of the tool after reaching the joint, but with a large distance to the tip of the guiding device. 
     DESCRIPTION OF THE INVENTION 
     An aspect of the present invention is, at least partly, to overcome the disadvantages of the device mentioned above, and to provide a tool which is simply constructed and allows for movements in three planes/directions (X, Y and Z planes) in just one part of the construction. 
     Another aspect is to provide a device which is suitable for guiding tools down into a lateral borehole, which can be placed close to, or even in front of, the tip of the guiding device. 
     An additional aspect is to provide a guiding device where a logging tool can be arranged in the front of the tool. 
     The above objects, together with numerous other objects, advantages, and features, which will become evident from the below description, are accomplished by a solution in accordance with the present invention by a downhole tool for guiding a device into a side track of a borehole, the tool having a tool axis and comprising:
         a tool housing connected to an energy source,
 
the tool housing comprising:
   a guiding nose for guiding the tool into the side track, and   a joint for providing a revolving and pivoting motion of the guiding nose,
 
wherein the tool comprises a second means comprising a terminal surface facing the joint and being inclined in relation to a plane perpendicular to the tool axis, and wherein the second means is able to slide along the tool axis to fixate the guiding nose in a position in which the nose inclines in relation to the tool axis.
       

     Furthermore, the invention relates to a downhole tool for guiding a device into a side track of a borehole, the tool having a tool axis and comprising:
         a tool housing connected to an energy source,
 
the tool housing comprising:
   a guiding nose for guiding the tool into the side track, and   a joint for providing a revolving and pivoting motion of the guiding nose,
 
wherein the joint comprises a first and a second part, the first part comprising a recess engaging with a key in the second part.
       

     The downhole tool is placed in a borehole, and a sensor, which is guided into the borehole together with the downhole tool, detects the position of the lateral borehole, also called a side track. Subsequently, the downhole tool is stopped and moved back into a position before reaching the side track, and the joint is activated in a way that allows for movement of the guiding nose in the direction of the side track in that the joint is able to move in two or three directions, or combinations thereof, depending on the position of the side track in relation to the guiding nose. The nose is able to move in a conical section of a ball. 
     A movement in two directions is to be understood as a movement in an X and Y direction in an X, Y coordinate system in which the longitudinal direction of the tool housing is the Z direction. A movement in three directions is to be understood as a movement in an X, Y and Z direction in an X, Y, Z coordinate system, and even a rotation around its own axis. As the entire movement of the guiding tip takes place in this single joint, the construction is less fragile compared to known devices, and is thus suitable for transporting wires all the way through a downhole tool or at least to the position of the joint. 
     In one embodiment, the tool may further comprise a driving unit powered by the energy source for providing at least the revolving and pivoting motion. 
     In another embodiment, one of the first and second parts may be a ball socket and the other may be a ball and socket head. 
     In yet another embodiment, the joint may comprise a ball and socket joint. 
     Thus, the joint may comprise a socket. 
     In addition, the joint may comprise a ball and socket head. 
     Furthermore, the joint may be a universal joint, a U joint, a Cardan joint, a Hardy-Spicer joint or a Hooke&#39;s joint. 
     Also, the guiding nose may have a first end facing the joint, and the joint may comprise an accessory means for preventing the first end of the guiding means from rotating around the centre axis of the guiding nose. 
     If logging or measuring equipment is connected in front of the tool, the accessory means ensures that wires connected to this equipment are not twisted and that a slip ring solution is unnecessary. 
     In one embodiment, the joint may comprise an accessory means ensuring that a movement only takes place in the two directions, the X and Y directions, of the guiding nose. 
     In another embodiment, the accessory means may comprise at least one groove shaped in the ball and socket head and one key arranged in connection with the ball socket, the key being engaged with the groove. 
     In this way, the joint can only perform a movement in the X and Y directions which are in a transverse plane perpendicular to the longitudinal axis of the tool housing. However, since the guiding nose is an elongated member connected to the ball and socket head, it is still able to provide a movement in three planes while being prevented from rotating around its own axis. 
     In yet another embodiment, the tool may comprise a second means comprising a means for fixing or defining the position of the tool. 
     In addition, the tool may further comprise a driving unit for moving the second means. 
     Also, the tool may comprise a driving unit, such as a step motor, for rotating the second means. 
     Furthermore, the second means may comprise an axially slideable bushing arranged in the tool housing concentrically around the axis of the tool housing. 
     In addition, the axially slideable bushing may comprise the terminal surface facing the joint, the terminal surface of the bushing being declining and forming an angle in relation to a line perpendicular to the centre axis of the tool housing. 
     The tool housing may also comprise a toothed rim bushing for providing a rotation of the second means by means of an interacting means, the toothed rim bushing being rotatable in relation to the housing and being placed concentrically around the centre axis of the tool housing. 
     In addition, the position may be a lateral position of the guiding nose, i.e. the centre axis of the guiding nose may form an angle with the centre axis of the tool. 
     Furthermore, the accessory means may comprise at least one groove shaped in the ball socket and one key arranged in connection with the ball and socket head, the key being engaged with the groove. 
     In one embodiment, the bushing may be placed inside a socket ball housing, the socket ball housing encircling the bushing and the joint. This solution provides unambiguous relations between the different construction parts. 
     In another embodiment, the angle may be 10-25°, preferably 15-20°. 
     In yet another embodiment, the toothed rim bushing may interact with a toothed wheel. 
     Furthermore, the toothed wheel may be driven by a driving unit which may be a step motor. 
     Also, the interacting means may be a pater/mater arrangement comprising an elevated area formed in the second means, which is slideably arranged in an abutting cylindrical bushing. This is a simple way of transmitting the rotating force to the axially slideable bushing. 
     In addition, the axially slideable movement of the second means may be provided by at least one piston rod pushing the second means. This is simple way of transmitting the axial force to the axially slideable bushing. 
     According to the invention, the number of piston rods may be at least one and preferably three. 
     In one embodiment, the piston rod(s) may be moved by the driving unit driving a piston and be connected to the piston. 
     In another embodiment, the driving unit may be a motor or a hydraulic pump. 
     In yet another embodiment, the energy source may be a wireline. 
     The invention also relates to a method for moving a downhole tool as mentioned above into a side track, comprising the steps of:
         moving the tool into the borehole,   detecting a side track,   positioning the guiding nose opposite the side track,   positioning the second means in a start position, and   moving the guiding nose into the position by moving the second means towards the joint in the axial direction of the tool housing by means of the bushing means,
 
whereby the guiding nose is moved by the movement of the second means.
       

     The method may further comprise the step of moving the tool forward, whereby the guiding nose hits against a wall of the side track, thereby guiding the tool into the side track. 
     The invention relates also to a downhole system comprising the downhole tool described above, the system further comprises a downhole tractor. 
     Finally, the invention relates to the use of the downhole tool described above in combination with a tractor. 
    
    
     
       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 illustration show some non-limiting embodiments and in which 
         FIG. 1  shows an outside view of a tool according to invention, 
         FIG. 2  shows a cross-section through the tool on line AA of  FIG. 1 , 
         FIG. 3  shows a cross-section through the tool on line EE of  FIG. 2 , 
         FIG. 4  shows a cross-section through the tool on line BB of  FIG. 2 , 
         FIGS. 5A and 5B  show a perspective view of a part of the joint including a ball socket, 
         FIG. 6  shows a perspective view of a part of the joint including a ball and socket head, 
         FIG. 7  shows a perspective view of the socket ball housing, 
         FIGS. 8A and 8B  show a perspective view of the second means, the axially slideable bushing, 
         FIG. 9  shows a perspective view of the ball and socket head and the axially slideable bushing, 
         FIG. 10  shows a perspective view of the ball socket integrated with the guiding nose and the axially slideable bushing where the housing is removed, 
         FIG. 11  is a principle figure of the tool according to the invention and its relation to a tractor and helping tools, and 
         FIG. 12  is a principle figure of the tool according to the invention and its relation to a tractor and helping tools, placed in a borehole provided with a side track. 
     
    
    
     All these figures are highly schematic and not necessarily to scale, and they show only those parts which are necessary in order to elucidate the invention, other parts being omitted or merely suggested. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a downhole tool  1  according to the invention, comprising an outer tool housing  4 . In extension of this housing, a socket ball housing  23  is arranged concentrically around a centre axis  51  of the tool. The socket ball housing  23  surrounds a joint  10 , which provides a revolving and pivoting motion. The joint comprises a first  61  and a second  62  part. A revolving and pivoting motion should be understood as a pivoting and spinning movement around a central point, and even a rotating movement around the centre axis  53  of the guiding nose  6 . The joint  10  is in this embodiment constructed as a ball and socket joint  12 , however it could be any kind of joint, such as a universal joint, a U joint, a Cardan joint, a Hardy-Spicer joint or a Hooke&#39;s joint, allowing the guiding nose  6  to move, thereby causing revolving or pivoting motions, at least in the X and Y planes and also occasionally in the Z direction. In continuation of the socket ball housing  23  and in integrated connection with the ball and socket head  14 , the guiding nose  6  is formed. This guiding nose  6  is able to make revolving and rotating motions in a conical pattern around the tool axis  51 . 
       FIG. 2  shows a cross-section of the downhole tool  1  shown in  FIG. 1  along the section line A-A. The downhole tool  1  comprises an outer cylindrical part being a tool housing  4  arranged concentrically around the centre axis  51  of the downhole tool  1 . In continuation of the tool housing  4 , a socket ball housing  23  is arranged which also comprises a part of the tool housing  4 , the socket ball housing  23  also being a cylindrical device or a socket bushing  56  arranged concentrically around the centre axis  51  of the tool  1 . Inside the socket ball housing  23 , a cylindrical toothed rim bushing  24  is arranged concentrically around the centre axis  51  of the downhole tool  1 . The rim bushing  24  is able to rotate more than 360° and is rotatably arranged around the centre axis  54 ,  51 . 
     The rotation happens as a consequence of the toothed rim  24 ′ being arranged on the inside of the bushing  24  and interacting with a toothed wheel  25  which is driven by a step motor  26 , as can be seen in  FIGS. 2 and 3 . The toothed wheel  25  is connected to the step motor  26  by means of a shaft  32 . The toothed rim bushing  24  is a pater/mater arrangement  27  intermeshing with another bushing  19 ,  20  also referred to as the second means  19 . The second means  19  is in this embodiment formed as a cylindrical bushing  19 ,  20  which is axially slideable. This axially slideable bushing  19 ,  20  is also able to rotate around its own centre axis  53  which coincides with the centre axis  51  of the tool housing  4 . 
     The rotating motion of the second means  19  happens due to the interaction of the pater/mater arrangement  27  as a consequence of the movement of the rim bushing  24  when the rim bushing  24  turns. The rotating motion caused by the rim bushing  24  is transferred to the second means  19  due to the interaction of the pater/mater arrangement  27 . The pater/mater arrangement  27  may typically be formed by providing a toothed rim bushing  24  with recesses at its end pointing towards the axially slideable bushing  19 ,  20 . The axially slideable bushing  19 ,  20  is formed with rectangular tongues which interact with corresponding recesses formed in the toothed rim bushing  24 . This is also shown in  FIGS. 8A, 8B and 9  and is further explained below in connection with the description of  FIGS. 8A and 8B . 
     The terminal surface  22  of the axially slideable bushing  19 ,  20  pointing towards the toothed rim bushing  24  is cut off in a plane cut, and the other terminal surface  21  pointing towards the guiding nose  6  is formed with a declining terminal surface  21  forming an angle A between the plane of the terminal surface  21  and a line perpendicular to the centre axis  51  of the tool. This angle A is typically between 10-25°, preferably between 15-20°. 
     The declined terminal surface  21  of the bushing  19 ,  20  is directed towards the joint  10  which is a ball and socket joint  12 . Thus, the joint  10  comprises a first part  61  which is a ball socket  13  which is arranged rotatably around the second part  62  which is a ball and socket head  14 . The ball and socket head  14  is arranged in the tool housing in such a way that the centre axis  54  of the ball and socket head  14  coincides with the centre axis of the tool housing. The ball and socket head  14  is arranged immovably on a shaft  45  having a circumferential projecting area  44  providing the correct position of the ball and socket head  14  in relation to the axially slideable bushing  19 ,  20 . The ball and socket head  14 , the shaft  45  and the projecting area  44  may be moulded as one part. The shaft  45  has a through-going bore  52  through which wires can be arranged. 
     The circumferential projecting area  44  abuts the inside surface of the axially slideable bushing  19 ,  20 . The ball socket  13  partly surrounds the ball and socket head  14  and is connected with, or completely integrated with, the guiding nose  6  at the end of the ball socket opposite the surface abutting the inclined terminal surface of the axially slideable bushing  19 ,  20 . As the ball socket  13  moves, which movement may be a hinged or rotating movement or both, or combinations thereof, the guiding nose  6  will move with or follow the movement of the ball socket  13 . This is due to the movement of the axially slideable bushing  19 ,  20  and the interface between the declined surface  21  of the axially slideable bushing  19 ,  20  and a plane terminal surface  55  of the ball socket  13 . 
     The guiding nose  6  could be elongated with another cylinder encircling the guiding nose  6  which is preferably formed as a cylindrical part. The guiding nose  6  could also preferably be tapered in the front. Furthermore, the guiding nose  6  is provided with a channel  6 ′ through which wires could be placed in order to supply a helping tool  38 , such as a logging equipment, in front of the downhole tool  1 . 
     The end surface  55  of the ball socket  13  pointing towards the axially slideable bushing  19 ,  20  is plane in order to precisely follow the movement of the axially slideable bushing  19 ,  20 . When the axially slideable bushing  19 ,  20  is axially displaced and the inclined surface points towards the plane surface of the ball socket  13 , the ball socket moves into the desired position, and the guiding nose  6  will thereby move into its position. 
     The movement of the guiding nose  6  is a spacious movement in three directions; X, Y and Z, or combinations thereof, providing a revolving and pivoting motion. However, the ball and socket joint  12  is advantageously provided with a key/pin in the ball socket  13 , interacting with a groove  17  arranged in the ball and socket head  14 . In this way, the movement of the ball and socket joint  12 , and thereby the movement of the guiding nose  6 , are reduced to a movement only in the X and Y directions and combinations thereof, and rotation of the guiding nose  6  around its own axis  53  is thereby avoided. 
     The rotation of the toothed rim bushing  24  is provided by a rotation of the toothed wheel  25  which is placed on a rotating shaft  32  rotated by the step motor  26 . This means that when the toothed wheel  25  turns, the toothed rim bushing  24  rotates, and the movement of the toothed rim bushing  24  is transferred to the axially slideable bushing  19 ,  20  by means of the pater/mater arrangement  27 . In this way, the angled surface of the axially slideable bushing  19 ,  20  takes a position where the inclined surface points towards the side of the casing  57  in which the side track  2  is placed. Subsequently, an axial movement of the axially slideable bushing  19 ,  20  is performed by a driving unit  9 , such as a motor or a hydraulic pump, ensuring that a piston  30  is pushed forward in the direction of the guiding nose  6 , the motor and the slideable piston  30  being placed inside the tool housing  4 . 
     The piston  30  transfers the force to the axially slideable bushing  19 ,  20  by means of at least one piston rod  31 , and a terminal surface of the piston rod has a resting surface at a plane surface  22  of the axially slideable bushing  20 . The number of piston rods  31  could be one or more, preferably three. Due to the axial movement of the axially slideable bushing  19 ,  20 , the declined terminal surface  21  of the bushing  20  is pushed against the plane end surface  55  of the ball socket  13 , ensuring that the ball socket  13  is displaced, and the guiding nose  6  is thus moved in the desired direction. 
     Due to these mechanical movements of parts of the downhole tool  1 , the final positioning of the guiding nose  6  takes place, and the guiding nose  6  is now turning in the direction of the side track  2  and is guiding the downhole tool  1  when moved forward in the casing  57 . Typically, a sensor is arranged in the downhole tool  1  in such a way that it is able to detect the position of the side track  2 , and the downhole tool  1  is placed in the right position in the main casing, ensuring that the guiding nose  6  is positioned opposite the side track  2 . The movement of the guiding nose  6  taking place at the tip of the downhole tool  1  ensures that wires can be provided inside the tool housing  4  without twisting the wires, at least until the point where the joint is placed. Furthermore, the movement of the nose  6  taking place in at least the X or Y direction of a conventional coordinate system where the tool axis  51  is the Z direction also enables wires being provided inside the tool housing  4  without twisting the wires, at least until the point where the joint is placed. If the joint is also provided with means preventing a rotation of the guiding nose  6  of more than 360° around its axis  54 , the wires may continue past the moving joint and into a helping tool  38  or logging tool which may be placed in continuation of the guiding nose  6 , and the wires will thus not be twisted although the nose is rotated. 
       FIG. 3  shows a detailed view along the section E-E of  FIG. 2  showing the tool housing  4  and a step motor  26  arranged inside the tool housing  4 . The step motor  26  drives a shaft  32  which is connected to the toothed wheel  25  driving the toothed rim bushing  24  as the toothed wheel  25  interacts with a rim  24 ′ arranged on the inside surface of the toothed rim bushing  24 . 
       FIG. 4  shows a sectional view along the line B-B of  FIG. 2  during an interaction of the toothed wheel  25  and the rim  24 ′ of the toothed rim bushing  24 . It also shows the bottom part of the axially slideable bushing  19 ,  20  which is provided with areas  41  having a higher friction. In this case, three such areas are provided. These areas create a good connection between the axially slideable pistons and the terminal surface  22  of the axially slideable bushing  20 . 
     Referring to  FIGS. 5A, 5B and 6 , it will now be explained how the movement can be reduced to a movement in the X and Y directions.  FIG. 5A  shows a part comprising both the ball socket  13  and the guiding nose  6  or a part of the guiding nose  6 . This part is placed concentrically around the ball and socket head  14  and moves rotatably around the same. A terminal surface  55  of the ball socket is plane and forms an interfaced surface  43  to the axially slideable bushing  20  as this surface faces the terminal declined surface  21  of the slideable bushing  20 . In the ball socket  13 , a key/pin is arranged. This could be an integrated part arranged on the inner side of the socket, pointing radially towards the centre of the axis, or it could simply be an exchangeable pin arranged in a hole in the ball socket  13 . This key/pin interferes with a recess arranged in the ball and socket joint  12 , the recess  17  being shown in  FIG. 6 . In  FIG. 5A , the part comprising both the ball socket  13  and the guiding nose  6  is shown from one end of the part, and in  FIG. 5B , the part comprising both the ball socket  13  and the guiding nose  6  is shown from the other end of the part. The embodiment of  FIGS. 5A and 5B  varies from the embodiment of  FIGS. 1 and 2  in that the guiding nose  6  is provided with several recesses in the form of grooves to be able to connect easily with other tools or devices arranged in front of the tool. 
     In  FIG. 6 , the recesses  17  are placed or formed parallel with the centre axis of the tool housing  4 . There are preferably two recesses  17 , one on each side of the ball and socket head  14 , ensuring that when the key interferes with the recess, the ball socket  13  can only move in the X and Y directions but is unable to rotate around the Z direction. In this way, it is avoided that wires in the channel  6 ′ and bore  52  passing the joint  10  are twisted, as a rotation of 360°×N (N=1:∞) is avoided. This key and recess arrangement could of course also be opposite in that the key could be placed in the ball and socket head  14 , and the recess  17  could be placed on the inside surface of the ball socket  13 . There are preferably two keys on either side of the ball and socket head  14 . 
       FIG. 7  is a detailed view of the socket ball housing  23  and shows a tapered end  46  of the socket bushing, this end partly surrounding the ball socket  13  and hindering the part comprising the ball socket  13  and the guiding nose  6  from moving away from the ball and socket head  14 . 
       FIG. 8A  shows a perspective view of the second means  19  formed as an axially slideable bushing  19 ,  20  comprising the cylindrically formed housing which in one terminal end is plane, this end pointing towards the rim bushing  24 . The other terminal end  21  is inclined in such a way that the end surface forms an angel A with the line perpendicular to the centre axis of the bushing  19 ,  20 , this centre axis being coincident with the centre axis of the tool housing  4 . In  FIG. 8A , the second means in the form of the bushing  19 ,  20  is shown from one end of the bushing, and in  FIG. 8B , the bushing is shown from its other end. 
     At the plane end, the bushing  19 ,  20  is arranged with areas interacting with the rotating rim bushing  24  comprising rectangular areas being elevated and forming tongues  28 ′, and between these areas, rectangular areas with reduced thickness  28  are formed, which the flange of the rim bushing will slide into and form thereby a pater/mater locking system. 
       FIG. 9  shows a perspective view of the ball and socket head  14  placed on the shaft  45 . This shaft  45  is surrounded by the axially slideable bushing  19 ,  20 , and the angled terminal surface  21  of the axially slideable bushing  19 ,  20  points towards the head  14 . 
     The other terminal surface  22  points towards the rim bushing  24  and intermeshes with the toothed rim bushing  24  due to the pater/mater arrangement  27  described above. This intermeshing arrangement could be constructed in several other ways, e.g. it could be small pins intermeshing into small cylinders holes. It is important that the interface ensures that the rotation of the rim bushing  24  is transferred to the slideable bushing  19 ,  20  and that the rim bushing  24  and the slideable bushing  19 ,  20  are axially displaceable in relation to each other when the declining surface  21  of the slideable bushing  20  has reached its desired position. 
       FIG. 10  shows a perspective view of the ball socket integrated with the guiding nose  6  and the axially slideable bushing  19 ,  20  where the socket ball housing  23  has been removed. 
     The guiding nose is  6  connected to the ball socket  13 , and they can be integrated parts moulded together, or the nose  6  could be a separate part fastened to the socket  13 . The length of the guiding nose  6  can also vary and be telescopically formed. The telescopic function could be activated by means of the same power unit as that driving the means to position the guiding nose  6 . The interface formed by the plane terminal surface  55  of the ball socket  13  and the inclined terminal surface  21  of the slideable bushing  20  determines the position of the guiding nose  6 . 
       FIG. 11  shows a principle figure of the downhole tool  1  according to the invention and its relation to a downhole tractor  37  and helping tools  40 . The downhole tool  1  according to the invention is typically operated by a downhole tractor  37 . The guiding tool  1  is arranged in front of the downhole tractor  37 , and a helping tool  38  is typically arranged between these two or in front of guiding the downhole tool  1 . The helping tool  38  could be a pressure sensor which is transported safely down into the side tack  2  due to the guiding tool/downhole tool  1 . The downhole tractor  37  is used to draw and/or push the entire construction in the casing and is powered by energy from a wireline  5 . A downhole tractor is any kind of driving tool able to push or pull tools in a valve downhole, such as a Well Tractor®. 
     In front of the guiding tool  1 , logging or measuring equipment or another helping tool  38 , i.e. a milling tool  40  or a filter, could be placed. In this case, the helping tool  38  is typically supplied with power by wires which are placed in the bore  52  and the central channel  6 ′ in the guiding nose  6  and pass the joint and the guiding nose. 
       FIG. 12  shows a principle figure of the downhole system comprising a downhole tool  1 , a downhole tractor  37  and helping tools  38 . The downhole system is arranged in a casing  57  provided with a side track  2 , and the nose  6  is moved into position in order to guide the tool  1  into the side track  2 . 
     A downhole tool  1  according to the invention is placed in a casing  57  in a borehole  3  closed at the top by a well head  50 . The movement of the guiding nose  6  is driven by a driving unit  9 , such as a motor or a hydraulic pump, and the downhole tool  1  is driven by a downhole tractor  37  which is supplied with energy by a wireline  5 . The wireline  5  is connected to a power supply, e.g. an oil rig, situated above surface. This power supply also supplies the tool  1 . 
     When the guiding nose  6  is opposite the side track  2 , the nose  6  moves into the right position and is caught by the walls of the side track  2  when the tool  1  moves forward in the casing  57 . As the entire tool  1  is pushed further downwards, the nose  6  ensures that the tool is guided into the side track  2  and further down in it. 
     A wire made of fibreglass may be arranged in the channel  6 ′ and bore  52  and be fixated in the piston  30 . When the guiding nose  6  is not fixated in an inclined position by means of the bushing  19 ,  20 , it may hang loose from the rest of the downhole tool  1 . By arranging a fibreglass wire in the channel  6 ′ and the bore  52 , the wire will lead the guiding nose  6  into a position where it is inclined as little as possible and where a centre axis  53  is more parallel to a centre axis  54  of the shaft. This is due to the fact that the wire is flexible and bendable when the nose  6  is inclined, but the wire is still rigid and will flex back into its relaxed position, thereby forcing the nose  6  to assume en uninclined position. 
     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 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. 
     
       
         
           
               
               
               
               
             
               
                   
               
             
            
               
                  1 
                 Downhole tool 
                 23 
                 socket ball housing 
               
               
                  2 
                 side track 
                 24 
                 toothed rim bushing 
               
               
                  3 
                 bore hole 
                 24′ 
                 toothed rim 
               
               
                  4 
                 tool housing 
                 25 
                 toothed wheel 
               
               
                  5 
                 energy source 
                 26 
                 step motor 
               
               
                  6 
                 guiding nose 
                 27 
                 pater mater arrangement 
               
               
                  6′ 
                 channel 
                 28′ 
                 elevated area 
               
               
                  7 
                 Joint 
                 29 
                 recess groves 
               
               
                  8 
                 Position 
                 30 
                 piston 
               
               
                  9 
                 driving unit 
                 31 
                 piston rod 
               
               
                 10 
                 joint 
                 32 
                 shaft 
               
               
                 11 
                 second position 
                 33 
                 wireline 
               
               
                 12 
                 ball and a socket joint 
                 37 
                 tractor 
               
               
                 13 
                 ball socket 
                 38 
                 helping tool 
               
               
                 14 
                 ball and socket head 
                 40 
                 mill tool 
               
               
                 15 
                 center axis 
                 41 
                 Friction area for piston rod 
               
               
                 16 
                 accessory means 
                 43 
                 interface surface 
               
               
                 17 
                 groove 
                 44 
                 circumferential projecting area 
               
               
                 18 
                 key 
                 45 
                 shaft ball and socket head shaft 
               
               
                 19 
                 second means 
                 50 
                 rig 
               
               
                 20 
                 bushing 
                 51 
                 centre axis of tool 
               
               
                 21 
                 terminal surface 
                 52 
                 bore 
               
               
                 22 
                 terminal surface 
                 53 
                 centre axis of guiding nose 
               
               
                 55 
                 terminal surface of socket 
                 57 
                 casing 
               
               
                 56 
                 device/socket housing 
                 62 
                 second part 
               
               
                 61 
                 first part