WO2018156029A2

WO2018156029A2 - Indexing tool for a wellbore string

Info

Publication number: WO2018156029A2
Application number: PCT/NO2018/050048
Authority: WO
Inventors: Christian Berven; Michael Kennedy WILLIAMSON
Original assignee: Toolserv As
Priority date: 2017-02-23
Filing date: 2018-02-22
Publication date: 2018-08-30
Also published as: WO2018156029A3; NO343519B1; NO20170262A1

Abstract

An indexing tool (10) for a wellbore string (100) is described. The indexing tool is suitable for assisting a tool connected thereto in passing an obstruction in a well. The indexing tool (10) comprising: - a first tubular body (12); - a second tubular body (13) for receiving a portion of the first tubular body (12); - a retention means (18) for preventing the second tubular body (13) from sliding off of the first tubular body (12) when the indexing tool (10) is exposed to tensile forces in an axial direction; and - a protruding element (16) fixedly connected to the second tubular body (13); wherein a recess (14) is provided in connection with the first tubular body (12) for receiving and guiding the protruding element (16), said recess (14) extending in a circumferential and axial direction with regards to the first tubular body (12); wherein the indexing tool (10) further comprises: - a sleeve (19) movably arranged around a portion of the first tubular body (12), wherein the sleeve (19) comprises the recess (14); - an engagement means (20) arranged for: - engaging with the sleeve (19) and fixing the position of the sleeve (19) with regards to the first tubular body (12) when the first tubular body (12) is pulled in an axial direction away from the second tubular body (13), and for - disengaging from the sleeve (19) when the indexing tool (10) is exposed to external compressive forces such as from the wellbore string (100) being pushed against an obstruction in the well, such that the sleeve (19) rotates independently from the first tubular body (12). A wellbore string (100) comprising the indexing tool (10) is also described.

Description

INDEXING TOOL FOR A WELLBORE STRING

The invention concerns an indexing tool for a wellbore string. More particularly the invention concerns an indexing tool comprising a first tubular body and a second tubular body for receiving a portion of the first tubular body. The indexing tool is adapted for staged rotation of the second tubular body with regards to the first tubular body.

The purpose of an indexing tool is to rotate a portion of a wellbore string without having to rotate the entire string. The term "wellbore string" will herein include any downhole pipe string, casing string and tubing string. An indexing tool can be used in conjunction with other pieces of known downhole tools in order to facilitate getting these tools into the wellbore in an efficient manner. For instance, when the wellbore string runs into an obstruction in the well, the indexing tool can assist in passing the obstruction without having to rotate the entire wellbore string.

Prior art indexing tools typically comprise a so-called J-slot making up a zigzag pattern on the first tubular body, and a corresponding pin fixed to the second tubular body, such that when the first tubular body is reciprocated with respect to the second tubular body, the pin will be forced to follow the slot and thereby cause a staged rotation of the second tubular body, i.e. the second tubular body rotates one step when the indexing tool is exposed to an axial compressive force and another step when the indexing tool is exposed to an axial tensile force, and so on.

One of the problems connected to passing an obstruction in a well by means of an indexing tool, is that the staged rotation of the second tubular body, and the tool connected thereto, causes considerable torque which in turn may damage the tool. In particular the threads of a downhole tool have torque limitations.

Another drawback of the prior art indexing tools is that they are relatively expensive to produce.

The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least to provide a useful alternative to prior art.

The object is achieved through features, which are specified in the description below and in the claims that follow.

The invention is defined by the independent patent claims. The dependent claims define advantageous embodiments of the invention.

In a first aspect the invention relates more particularly to an indexing tool for a wellbore string and for assisting a tool connected thereto in passing an obstruction in a well , the indexing tool comprising:

- a first tubular body;

- a second tubular body for receiving a portion of the first tubular body;

- a retention means for preventing the second tubular body from sliding off of the first tubular body when the indexing tool is exposed to tensile forces in an axial direction ; and

- a protruding element fixedly connected to the second tubular body;

wherein a recess is provided in connection with the first tubular body for receiving and guiding the protruding element, said recess extending in a circumferential and axial direction with regards to the first tubular body. The characteristic features of the indexing tool are that it further comprises:

- a sleeve movably arranged around a portion of the first tubular body, wherein the sleeve comprises the recess;

- an engagement means arranged for:

- engaging with the sleeve and fixing the position of the sleeve with regards to the first tubular body when the first tubular body is pulled in an axial direction away from the second tubular body, and for

- disengaging from the sleeve when the indexing tool is exposed to external compressive forces such as from the wellbore string being pushed against an obstruction in the well, such that the sleeve rotates independently from the first tubular body.

The first tubular body may also be called the inner tubular body, or mandrel, whereas the second tubular body housing at least a portion of the first tubular body, may also be called the outer tubular body. In prior art indexing tools, the recess is provided in the portion of the first tubular body which is to be received by the second tubular body. The portion comprising the recess is expensive to produce, since the entire first tubular body has to be handled by machining tools. The sleeve comprising the recess, as disclosed in the first aspect of the invention, is cheaper and easier to produce. The use of a sleeve also has the advantage that it may be made of different materials than that of the first tubular body, such that if the body must be constructed from expensive materials, the sleeve may still be made from less expensive grade of steel. A further advantage of using a sleeve is that it may be replaced if it is damaged, without having to replace the entire first tubular body.

When the sleeve is slid over a portion of the first tubular body, it is movable in an axial direction and it is also rotatable with regards to the first tubular body. In the following any references to direction of rotation is with regards to the indexing tool in use. The retention means which prevents the second tubular body from sliding off of the first tubular body, also limits the axial movement of the sleeve in one direction. On the other side of the sleeve, the engagement means is provided. The engagement means is fixed to the first tubular body and will get into engagement with the sleeve when there is a pull in the well string, such that the first tubular body is pulled in an axial direction away from the second tubular body. When the engagement means is engaged with the sleeve, the sleeve is prevented from rotating. This means that since the sleeve is prevented from rotation, and the protruding element of the second tubular body is forced to travel along the recess, the second tubular body, and any downhole tool connected thereto, will be rotated a circumferential distance corresponding to the circumferential distance of the recess.

However, when the wellbore string is pushed against an obstruction in a well, causing compression of the indexing tool, such that the second tubular body is forced in an axial direction towards the first tubular body, the engagement means will get out of engagement with the sleeve at least to such an extent that the sleeve may be rotatable. The protruding element will follow the recess in the opposite direction and cause the sleeve to rotate around the first tubular body, i.e. only the sleeve rotates. In this way it is avoided that the second tubular body, and any tool connected thereto, rotates during compression. The indexing tool according to the first aspect of the invention therefore does not generate torque when weight is set down onto it in a downhole environment, and thereby the risk of damaging other parts of the downhole tool is greatly reduced compared to prior art indexing tools.

When the indexing tool as part of a wellbore string is driven into a well, the second tubular body of the indexing tool enters the well before the first tubular body of the indexing tool. If it is said herein that the second tubular body is rotated in a clockwise direction, that therefore means that the second tubular body rotates to the right when seen from the position of the first tubular body. Similarly, if the second tubular body is said to rotate anticlockwise, it is rotating to the left when seen from the position of the first tubular body.

The indexing tool, comprising the above-mentioned first tubular body and second tubular body, consequently has an inside diameter. It is also well known that a wellbore string has an inside diameter.

The inside diameter of the indexing tool may be equal to the inside diameter of the wellbore string. In a preferred embodiment, the inside diameter of the indexing tool may be no smaller than the inside diameter of the wellbore casing string to which it is connected. The purpose of this is to facilitate the running of other pieces of equipment through the bore of the indexing tool after it has been installed in a wellbore. Some examples of equipment that could be passed through the bore of the indexing tool are - drill bits, casing or liners, logging tools, etc. The benefit of having the inside diameter of the indexing tool the same as the casing string is that there is no need to remove any internal components of the indexing tool before running any subsequent pieces of equipment through the bore. This removes the need for drilling out any components of the tool and therefore saves time and makes future operations simpler.

The engagement means may be fixedly connected to the first tubular body. It is an advantage to have the engagement means fixedly connected to the first tubular body, since the purpose of the engagement means is to keep the sleeve from moving with respect to the first tubular body when the engagement means is in engagement with the sleeve. The engagement means may be a ring which for instance is arranged on the first tubular body by means of a threaded connection. The engagement means may be connected to the first tubular body after the sleeve has been slid into place, such that the engagement means also provides a stopping means for preventing the sleeve from sliding off of the first tubular body.

The engagement means may be provided with an interlocking mechanism facing a corresponding interlocking mechanism arranged on the sleeve. Typically, the face of the sleeve facing the engagement means could be provided with some kind of protrusions or recesses arranged to go into engagement with corresponding elements of the engagement means. When the engagement means is pulled into contact with the sleeve, the interlocking mechanism will stop the sleeve from rotating as the protruding elements of the second tubular body are forced to follow the recesses of the sleeve. When the tensile force is released, the sleeve will again be free to rotate.

The interlocking mechanism may comprise pins and slots. As an alternative, the interlocking mechanism may be a mechanism using the ball and taper principle.

The interlocking mechanism may comprise teeth. Teeth may be provided along the entire circumference of the sleeve and the ring, if the engagement means is a ring as mentioned above. Teeth may alternatively be provided along the entire circumference of either the sleeve or the ring and along at least a part of the circumference of the other of the sleeve or the ring.

Teeth constitute a preferred interlocking mechanism since they may easily be shaped such that one side of each tooth is inclined and the other side is straight, or mainly straight, for providing as much friction as possible between the corresponding teeth of the engagement means and the sleeve. The straight side efficiently stops the sleeve from rotating with regards to the engagement means, whereas the inclined side may allow the sleeve to rotate as long as the sleeve is given room to move in the axial direction.

The circumferential distance between the teeth should preferably be smaller than the circumferential distance from one end of the recess to the other end of the recess in order to provide the most efficient rotation of the tool. The second tubular body will rotate when the sleeve is in engagement with the engagement means, thus the smaller the distance which the sleeve has to rotate in order for the interlocking mechanism of the sleeve to align with the interlocking mechanism of the engagement means, the more of the movement of the protruding element in the recess will be translated into rotation of the second tubular body and any tool connected thereto.

The recess may comprise a plurality of recesses and the protruding element may comprise a plurality of protruding elements such that the recesses pair up with the protruding elements. The more protruding elements there are, the more shear forces the indexing tool can withstand. The preferred number of recesses and corresponding protruding elements will vary with the size of the tool as well as with the size of the recesses and of the protruding elements.

The recesses may be identical and have the same orientation. By "same orientation" is herein meant that a straight line between a first end point and a second end point of a recess is parallel to a straight line between a first end point and a second end point of any one of the other recesses. The end points must be understood to be located on the centre lines of the recesses.

The/each recess may be straight. This is a preferred embodiment of the sleeve since it is easier to make straight recesses in the sleeve, than recesses of any other shape.

The protruding elements may be of any suitable shape. They may be round, square, oval, or any other shape suitable for moving along a corresponding recess in the sleeve.

The indexing tool may further comprise a spring for pushing the sleeve towards the engagement means. Since the tool will only rotate when the sleeve is in engagement with the engagement means it is desirable that, during pulling of the string, the sleeve gets engaged with the engagement means as quickly as possible such that as little as possible of the distance the protruding elements travel in the recesses is wasted before the rotation of the second tubular body begins. A spring will in particular be useful if the indexing tool is in a horizontal position or inverted in the well, such that gravity works on the sleeve to pull it away from the engagement means.

If one wishes, the indexing tool described herein could also be arranged such that the second tubular body only rotates upon compression instead of upon tension, if this would be preferable in any application of the tool.

Herein is also described an alternative indexing tool for a wellbore string and for assisting a tool connected thereto in passing an obstruction in a well, the indexing tool comprising:

- a first tubular body;

- a second tubular body for receiving a portion of the first tubular body ;

- a protruding element fixedly connected to the second tubular body;

wherein a recess is provided in connection with the first tubular body for receiving and guiding the protruding element, said recess extending in a circumferential and axial direction with regards to the first tubular body, wherein

the indexing tool further comprises:

- an engagement means arranged for: - engaging with the sleeve and fixing the position of the sleeve with regards to the first tubular body when the first tubular body is pushed in an axial direction towards the second tubular body, and for

- disengaging from the sleeve when the indexing tool is exposed to tensile forces, such that the sleeve rotates independently from the first tubular body.

In this alternative indexing tool, the inner tubular body, i.e. the first tubular body typically enters into the wellbore first. The first tubular body is forced towards the second tubular body for instance when the first tubular body hits an obstruction in the well. When this indexing tool, which rotates upon compression, is run into the wellbore, it is in a fully stroked out position. A guide shoe typically having an offset taper designed nose, may be arranged at the bottom of the indexing tool. When the nose meets any obstacle and is put into compression, it will start to rotate together with the first tubular body. This rotation may, in this particular embodiment continue through a significant angle, up to 360 degrees, to allow the nose to pass the obstacle. The indexing tool may further be provided with an internal spring which, once the nose has passed the obstacle, pushes the nose and second tubular body back to the fully stroked out position. This removes the need for an operator to ever have to pick up the casing or liner string while running it into the wellbore. This is advantageous in certain circumstances in order to avoid damaging any seal surfaces or in applications where the string cannot be picked up due to the extreme weight.

The variations described above for the first aspect of the indexing tool, are also valid for this alternative indexing tool.

Also described herein is an engagement means for the indexing tool according to the first aspect of the invention. The engagement means being arranged for fixing the position of the sleeve with regards to the first tubular body when the first tubular body is pulled in an axial direction away from the second tubular body. Said engagement means is arranged for going into and out of engagement with the sleeve, dependent on the reciprocation of the first tubular body with regards to the second tubular body. This makes it possible to rotate the second tubular body only when the indexing tool is exposed to axial tensile forces.

It should however be noted, that the engagement means and the indexing tool could also be constructed such that it works the other way round, namely such that the engagement means gets into engagement with the sleeve only when the indexing tool is exposed to axial compressive forces.

The engagement means may comprise:

- a first face;

- connecting means for connecting the engagement means to the first tubular body such that the first face faces the sleeve; and

- an interlocking mechanism arranged in connection with the first face for engaging with a corresponding interlocking mechanism arranged on the sleeve, such that when the interlocking mechanism of the engagement means is engaged with the interlocking mechanism of the sleeve, the sleeve is prevented from rotating.

Preventing the sleeve from rotating with regards to the first tubular body is causing the rotation of the second tubular body when protruding elements of the second tubular body are forced to follow corresponding, inclined recesses of the sleeve. Similar, when the engagement means is not in engagement with the sleeve, the movement of the protruding elements along the recesses causes the sleeve to rotate with regards to the first tubular body and without causing the second tubular body to rotate.

The engagement means may be a ring.

The connecting means of the engagement means may be a left-handed threading. This is a preferred embodiment where the recesses of the sleeve are arranged such that they cause the second tubular body to rotate in a clockwise direction. Thus, the rotation of the second tubular body will tighten the connection of the engagement means and the first tubular body.

The connecting means of the engagement means may alternatively be pins or any other suitable connecting mechanism.

The interlocking mechanism may comprise teeth. This is a possible embodiment of the engagement means.

Also described herein is a sleeve for the indexing tool according to the first aspect of the invention, the sleeve comprising:

- at least one recess for receiving a protruding element, the recess extending between a first end point and a second end point such that when the sleeve and the protruding element are moved relatively to each other back and forth in the axial direction of the indexing tool, the protruding element travels back and forth between the first end point and the second end point of the recess, wherein the second end point is arranged at an axial and circumferential distance from the first end point.

The first end point and the second end point are arranged on the centre line of the recess as mentioned above.

The sleeve may comprise a plurality of recesses. The recesses may be identical. And a straight line between the first end point and the second end point of a recess may be parallel to a straight line between the first end point and the second end point of any one of the other recesses.

The sleeve and the engagement means as described herein are interrelated elements which work together in order to perform the function of the indexing tool.

In a second aspect the invention relates more particularly to a wellbore string comprising the indexing tool according to the first aspect of the invention. The wellbore string may further comprise a tool such as an eccentric lipstick shaped nose or a reamer type shoe connected to the indexing tool. The indexing tool can then be rotated through as many turns as required to move the tool past an obstruction in a well.

In the following is described an example of a preferred embodiment illustrated in the accompanying drawings, wherein :

Fig. 1 shows a prior art indexing tool ;

Fig. 2 shows an indexing tool according to the invention, wherein the indexing tool is exposed to axial tensile forces;

Fig. 3 shows the indexing tool of Figure 2, wherein the indexing tool is exposed to compressive forces;

Fig. 4 shows a sleeve and an engagement means for an indexing tool according to the invention;

Figs. 5A-5F show a wellbore string with the indexing tool in different positions as the wellbore string faces and passes an obstruction in a wellbore;

Fig. 6 shows a long stroke indexing tool, partly cut through, in a perspective view; and

Fig. 7 shows a wellbore string comprising an indexing tool.

The figures are shown in a simplified and schematic manner, and details that are not important in order to highlight what is new about the invention may have been omitted from the figures. The various elements in the figures are not necessarily shown to scale relative to each other. Like or corresponding elements will be indicated by the same reference numeral in the figures.

Any positional specifications such as "over", "under", "above", "below", "left" and "right" reflect the position shown in the figures.

Reference is first made to Figure 1 which shows a perspective view of a prior art indexing tool 1 . The indexing tool 1 comprises a first tubular body 2 and a second tubular body 3 arranged to receive a portion of the first tubular body 2. In the figure, the second tubular body 3 is shown cut through in order to make the portion of the first tubular body 2 which is received within the second tubular body 3 visible. A so-called J-slot 4 is arranged in the portion of the first tubular body 2 which is received within the second tubular body 3. The second tubular body 3 is provided with a plurality of holes 5 for receiving pins 6 from the outside of the second tubular body 3. The holes 5 and pins 6 must be understood to be provided in the entire circumference of the second tubular body 3. The pins 6 are fixed to the second tubular body 3 and received in the J-slot 4 of the first tubular body 2, such that when the first tubular body 2 is reciprocating with regards to the second tubular body 3, the pins 6 are guided by the J-slot 4. The first tubular body 2 is shown having a varying outer diameter, such that it has a first outer diameter which is larger than a second outer diameter, wherein the second outer diameter is the outer diameter of the portion received in the second tubular body 3. The inner diameter of the first tubular body 2 and the second tubular body 3 are the same. The indexing tool 1 further comprises a connecting ring 7 which is slid over the slimmest portion of the first tubular body 2 before the first tubular body 2 is received in the second tubular body 3. The second tubular body 3 is then fixedly connected to the connecting ring 7 by means of threads 7a. Also a retention ring 8 is provided on the first tubular body 2. The retention ring 8 prevents the second tubular body 3, connected to the connecting ring 7, from sliding off of the first tubular body 2 when axial tensile forces are acting on the indexing tool 1 . When the first tubular body 2 is reciprocating in an axial direction with regards to the second tubular body 3, the pins 6 will be guided by the J- slot 4 causing a staged rotation of the second tubular body 3 with regards to the first tubular body 2. So, when a wellbore string comprising the indexing tool is pushed against an obstruction in the well the indexing tool 1 is exposed to axial compressive forces and the second tubular body 3 rotates one step. When the wellbore string is then pulled back, the indexing tool 1 is exposed to axial tensile forces and the second tubular body 3 rotates one further step. This way the indexing tool 1 , which typically is connected to an asymmetric tool such as a reamer shoe or a guide shoe (not shown), will guide the wellbore string past the obstruction.

Reference is now made to Figure 2 which shows an indexing tool 10 according to the first aspect of the invention. This indexing tool 10 is in many ways similar to the prior art indexing tool 1 , as also this indexing tool 1 0 comprises a first tubular body 12 and a second tubular body 13 connected to each other in a similar way as described above by means of a connecting ring 17 and a retention ring 18. However, the indexing tool 1 0 according to the invention further comprises a sleeve 19 provided with a recess 14, here shown as a plurality of recesses 14, replacing the J-slot 4 provided in the first tubular body 2 of the prior art indexing tool 1 . Pins 16 are provided connected to the second tubular body 13, for instance through not shown holes provided in the second tubular body 13 in a similar way as shown for the prior art indexing tool 1 of Figure 1 . Each recess 14 has a first end point 141 and a second end point 142. The sleeve 19 is movably arranged on the portion of the first tubular body 12 which is arranged to be received in the second tubular body 13. The sleeve 19 is arranged between the retention ring 18 and the end of the first tubular body 12. In order to make sure the sleeve 19 does not slide off of the first tubular body 12 a stopping means or engagement means 20 is provided. In this embodiment the engagement means 20 is shown as a ring 20 fixedly connected to the first tubular body 12. In addition to stopping the axial movement of the sleeve 1 9, the engagement means 20 is also arranged to stop the rotational movement of the sleeve 19 when the engagement means 20 is pulled against the sleeve 19, namely when the wellbore string comprising the indexing tool 10 is being pulled, i.e. when there is an axial tensile force pulling the first tubular body 12 away from the second tubular body 13. When the rotational movement of the sleeve 19 is prevented, and the pins 16 of the second tubular body 13 are still forced to follow the recesses 14 from the first end 141 to the second end 142, the result is that the second tubular body 13 rotates a distance corresponding to the circumferential distance of the recesses 14. Note that in the Figures only one or two pins 16 are shown in order to better illustrate the movement of the pins 16 with regards to the sleeve 19. In Figure 2 the pin 16 approaches the second end point 142 of its respective recess 14, and the rotation of the second tubular body 13 is about to come to an end. In this embodiment the recesses 14 are shown as straight recesses 14 which are parallel to each other and which axes are inclined with regard to the axial direction of the indexing tool 10. The pins 16 moving along the recesses 14 therefore have to move both an axial distance and a circumferential distance with respect to the sleeve 19. In the Figures the indexing tool 10 is shown connected to a guide shoe 300 with an eccentric lipstick shaped nose.

It must be understood that the recesses 14 may have a variety of different shapes as long as they extend an axial and circumferential distance with respect to the sleeve 19. The recesses 14 are preferably identical. And a straight line between the first end point 141 and the second end point 142 of one recess 14 is parallel to a straight line between the first end point 141 and the second end point 142 of any one of the other recesses 14. The recesses 14 may be displaced axially with respect to each other in addition to being displaced circumferentially with respect to each other. Obviously, the arrangement of the protruding elements 16 and the corresponding holes in the second tubular body 13 must be adapted to correspond to the recesses 14 of the sleeve 19.

In Figure 3 the indexing tool 10 is exposed to compressive forces. The first tubular body 12 and the second tubular body 13 are pushed towards each other such that the pins 16 are urged to follow the recesses 14 back towards the first end 141 of the recesses 14. Since the engagement means 20 connected to the first tubular body 12 is now pushed out of engagement with the sleeve 19, the sleeve 19 will be free to rotate under the influence of the pins 1 6, and the sleeve 19 will rotate independently of the first tubular body 12 and the second tubular body 13. In Figure 3 this is illustrated by the pin 16 which has moved only axially, whereas the sleeve has been rotated clockwise.

In Figure 4 an embodiment of the sleeve 19 and of the engagement means 20 are shown in more detail. It must be understood, as mentioned above, that the recesses 14 of the sleeve 19 in other embodiments may be of different sizes and shapes, and of different orientation. The orientation of the first end 141 with regards to the second end 142 is decisive for the direction of rotation of the sleeve 19 and of the second tubular body 13 (shown in Fig. 2 and 3), and also for the degree of rotation, i.e. how much of a full revolution the sleeve 19 or the second tubular body 13 travels per reciprocation. The recesses 14 may also be at different distances from each other as long as the same distances are provided between the protruding elements 16 connected to the second tubular body 13. In this particular embodiment there are twelve recesses 14 provided. The recesses 14 are evenly distributed around the circumference of the sleeve 19. In this embodiment the engagement means 20 is provided with an interlocking mechanism 21 in the form of teeth provided on a first face 23 of the engagement means 20. The first face 23 is in use arranged such that it faces the sleeve 19. The interlocking mechanism 21 corresponds to an interlocking mechanism 22 provided on the sleeve 19. The engagement means 20 is further provided with connecting means 24 for connecting the engagement means 20 to the first tubular body 12. In this embodiment the connecting means 24 is shown as a threaded connection.

The Figures 5A through 5F show a wellbore string 100 in a well 200, wherein the wellbore string 100 comprises the indexing tool 10 described above. In Figure 5A the wellbore string 100 is exposed to tensile forces in the axial direction, and the guide shoe 300 has just hit an obstruction 201 in the well 200. Now the indexing tool 1 0 is exposed to compressive axial forces as the wellbore string 1 00 continues to push against the obstruction 201 . In Figure 5B the effect of the compressive forces is illustrated, namely that the pins 16 (only one shown) are forced towards the first tubular body 12 and the sleeve 19 is rotated in a clockwise direction independently of the other parts of the indexing tool 10.

When, as shown in Figure 5C, the wellbore string 100 is pulled back and the indexing tool 10 again is exposed to tensile axial forces, the engagement means 20 interlocks with the sleeve 19 by means of the teeth of the interlocking mechanism 21 , 22. The pins 16 are forced to follow the recesses 14 and now the entire second tubular body 13 and the guide shoe 300 connected thereto are rotated clockwise.

Since the guide shoe 300 is still not able to pass the obstruction 201 , the indexing tool 10 will again be exposed to compressive forces as weight is set down on the wellbore string 1 00 again. This is illustrated in Figure 5D. The pins 16 move in an axial direction and the sleeve 19 again rotates independently of the other parts of the indexing tool 10 as the teeth of the interlocking mechanism 21 , 22 go out of engagement with each other.

Again, the wellbore string is pulled back, tensile forces act on the indexing tool 10, and the second tubular body 13 rotates. This is illustrated in Figure 5E. Now the guide shoe 300 is able to pass the obstruction 201 . When the wellbore string 100 is now pushed further into the well 200, as illustrated in Figure 5F, the wellbore string 100 will continue into the well without any further rotation of the sleeve 19 or of the second tubular body 13.

It is obvious that if one wishes, the indexing tool 10 described herein could also be arranged such that the second tubular body 13 only rotates upon compression instead of upon tension, if this would be preferable in any application of the tool 10. Also, the indexing tool 1 0 could be arranged such that the inner tubular body, i.e. the first tubular body 12, enters the wellbore first, and is the part of the tool 10 which rotates.

This is illustrated in Figure 6, which shows an indexing tool 10 designed for aiding entry past restrictions in the wellbore and also for navigating open hole sections with a high degree of tortuosity.

When this indexing tool 1 0, which rotates upon compression, is run into the well bore it is in a fully stroked out position as shown in Fig. 6. When the nose of the guide shoe 300 at the bottom of the indexing tool 1 0 meets any obstacle and is put into compression the nose and the inner mandrel , i.e. the first tubular body 12, start to rotate. This rotation may in this particular embodiment continue through a significant angle, up to 360 degrees, to allow the nose which typically has an offset taper design to pass the obstacle. Once the nose has passed the obstacle an internal spring 121 then pushes the nose and the second tubular body 13, back to the fully stroked out position. This removes the need for an operator of the tool to ever have to pick up the casing or wellbore string 1 00 while running it into the wellbore. This is advantageous in certain circumstances in order to avoid damaging any seal surfaces or in applications where the string 1 00 cannot be picked up due to the extreme weight.

Figure 7 shows a cut through wellbore string 100 comprising the indexing tool 10. This figure clearly illustrates that an inside diameter ID is equal for the indexing tool 10 and the rest of the wellbore string 1 00.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

C l a i m s

1 . Indexing tool (10) for a wellbore string (100) and for assisting a tool connected thereto in passing an obstruction in a well, the indexing tool (10) comprising:

- a first tubular body (12);

- a second tubular body (13) for receiving a portion of the first tubular body (12);

- a retention means (18) for preventing the second tubular body (13) from sliding off of the first tubular body (12) when the indexing tool (1 0) is exposed to tensile forces in an axial direction; and

- a protruding element (16) fixedly connected to the second tubular body (13);

wherein a recess (14) is provided in connection with the first tubular body (12) for receiving and guiding the protruding element (16), said recess (14) extending in a circumferential and axial direction with regards to the first tubular body (12);

c h a r a c t e r i z e d i n that the indexing tool (10) further comprises:

- a sleeve (19) movably arranged around a portion of the first tubular body (12), wherein the sleeve (19) comprises the recess (14);

- an engagement means (20) arranged for:

- engaging with the sleeve (19) and fixing the position of the sleeve (1 9) with regards to the first tubular body (12) when the first tubular body (12) is pulled in an axial direction away from the second tubular body (13), and for

- disengaging from the sleeve (1 9) when the indexing tool (10) is exposed to external compressive forces such as from the wellbore string (100) being pushed against an obstruction in the well, such that the sleeve (1 9) rotates independently from the first tubular body (12).

2. Indexing tool (10) according to claim 1 , wherein an inside diameter (ID) of the indexing tool (10) equals an inside diameter (ID) of the wellbore string (100).

3. Indexing tool (10) according to claim 1 or 2, wherein the engagement means (20) comprises a ring (20) fixedly connected to the first tubular body (12).

4. Indexing tool (10) according to any one of claims 1 -3, wherein the engagement means (20) is provided with an interlocking mechanism (21 ) facing a corresponding interlocking mechanism (22) arranged on the sleeve (19).

5. Indexing tool (10) according to claim 4, wherein the interlocking mechanism (21 , 22) comprises teeth.

6. Indexing tool (10) according to any one of claims 1 -5, wherein the recess (14) comprises a plurality of recesses (14) and wherein the protruding element (16) comprises a plurality of protruding elements (16) such that the recesses (14) pair up with the protruding elements (16).

7. Indexing tool (10) according to claim 6, wherein the recesses (14) are identical and have the same orientation.

8. Indexing tool (10) according to any one of claims 1 -7, wherein the/each recess (14) is straight.

9. Indexing tool (10) according to any one of claims 1 -8, wherein the indexing tool (10) further comprises a spring for pushing the sleeve (1 9) towards the engagement means (20).

10. Wellbore string (100) comprising the indexing tool (10) according to any one of claims 1 -