WO2003012247A1

WO2003012247A1 - Tool string member with bearings

Info

Publication number: WO2003012247A1
Application number: PCT/GB2002/003435
Authority: WO
Inventors: Robert Patrick Appleton
Original assignee: Internat Tubular Services Ltd; Appleton Robert P
Priority date: 2001-07-27
Filing date: 2002-07-26
Publication date: 2003-02-13
Also published as: GB2396873A; GB0118270D0; GB0400641D0

Abstract

A tool string member (10) is disclosed comprising a body (12) having a bearing race (20) on an outer surface of the body, and bearings (28) located in the race, wherein each bearing is held in the race against lateral movement. Restraining the bearings against lateral movement in the race distributes the load more evenly onto the body of the tool, and reduces the risks of high forces locking up all of the bearings in the race.

Description

"Tool String Member with Bearings"

The present invention relates to a tool string member, and particularly to a member that is adapted to reduce drag and increase torque- on a drill string by the provision of bearings.

When drilling and completing oil, gas and water wells, it is conventional in the art to use a tool string such as a drill string that generally includes a number of stands of drill pipe, and a drill bit located at one end thereof. The drill string is rotated using a number of conventional techniques to impart torque to the drill bit. Also, it is often necessary to insert the drill string and bit into the borehole and remove it therefrom during the drilling operation, for example, to change a worn drill bit.

Frictional forces in the borehole between the drill string and the exposed formation or casing can cause the string to become stuck so that it can no longer rotate, and many different solutions have been proposed to avoid the drill string from becoming stuck, particularly as freeing a stick string takes time and involves a loss of production capability.

According to the present invention there is provided a tool string member comprising a body having a bearing race on an outer surface of the body, and bearings located in the race, wherein each bearing is held in the race against lateral movement.

The tool string may be a drill string.

Typically the race comprises a plurality of cups or other receptacles for the bearings disposed on a common plane, with a single bearing being disposed in each cup; however, it is sufficient for there to be an annular race containing the bearings with some formation in the race to restrain at least some of the bearings from lateral movement in the race, e.g. around the circumference of the body.

The bearings are preferably free to rotate about their own axes in the cups, but are prevented from other movement in relation to the body by the cups. This provides the advantage that the bearings are restrained against movement around the circumference of the tool and external forces acting on them, such as the weight of the string against the side of the tool, tends not to lock up the bearings or transmit the load via the bearings to any particular part of the tool. Two races each comprising a respective row of cups are preferably provided, each race being longitudinally spaced from the other. The cups in one race are preferably circumferentially offset with respect to the cups in the other. The offset between the cups is approximately equal to the radius of the cup, so that as one side of the tool bears against one side of the casing the load is distributed between at least 3 bearings.

This forms another aspect of the invention, which provides a tool string member comprising a body having first and second bearing races axially spaced apart, and bearings located in the races, wherein the bearings in the first race are circumferentially offset with respect to the bearings in the second race.

The bearings are typically self-cleaning by rotation about their own axes. This prevents a build up of drill cuttings, dirt and other debris around the bearing that may prevent it from rotation. In certain embodiments, the body may be provided with bores, channels or other such conduits between the cups for the circulation of fluid between the cups but not permitting movement of the bearings through the channel. This has the advantage that the fluid helps to keep the cups and bearings free from cuttings, debris etc.

The bearings are preferably ball bearings. This has the advantage that both radial torque and vertical drag are reduced; however, the invention is not limited to ball bearings and any suitable bearing may be used, such as roller bearings etc. Where a roller bearing is used, each roller bearing is preferably mounted on its own axis so that it can rotate about its own axis, but is prevented from moving about the circumference of the member.

The bearings are typically retained in place by one or more sleeves. The sleeve is typically provided with at least one cupped or chamfered edge. The radius of the cupped edge is preferably substantially the same as the radius of the cups. The cupped edges of two sleeves typically abut an outer surface of the bearings to retain them in place. Four sleeves are typically provided, two sleeves being used to abut each set of bearings to retain them in place. A retainer is typically used to keep the sleeves in place. In one embodiment, the retainer comprises a lock collar that typically includes a threaded bore that engages with threads provided on the body. However, the retainer may comprise a snap-on or shrink-on ring, such as a heat sensitive shrink ring. A circlip may also be used. The retainer need not be annular.

The cups and the cupped edges are preferably provided with a hard facing, such as tungsten carbide. This prolongs the life of the member by decreasing wear. Having the ball bearings able to rotate about their own axes distributes the load more evenly, and in particular, there is no or very little transfer of the load to the sleeves . The load is mainly transferred to the body via the bearings.

The bearings preferably protrude past an outermost surface of the member to a small extent so that they can bear against an innermost surface of a borehole wall, casing, or liner etc.

The member is typically suitable for making up into a rotating or non-rotating drill string or other tool string used for oil or gas exploration or recovery. The member and the bearings facilitate rotation of the rotating string in a borehole, casing, or liner etc. The bearings can also facilitate axial displacement of a non-rotating string as it is being inserted into and withdrawn from a borehole, casing, liner etc.

The body is preferably provided with connection means to allow the member to be coupled to a string such as a stand of drill pipe to form a drill string. The connection means may comprise pin and box connections for example. It will be appreciated that the cups and bearings may be provided on one or more stands of drill pipe, rather than on a separate member . Embodiments of the present invention shall now be described, by way of example only, and with reference to the accompanying drawings, in which: -

Fig. 1 is a cross sectional view of a body forming part of a drill string member; Fig. 2 is a cross section through the body taken along the line AA in Fig. 1; Fig. 3 is a cross section through the body taken a along the line BB in Fig. 1; Fig. 4 is a cross sectional view of an exemplary embodiment of a drill string member; Fig. 5 is a cross section through the member of Fig. 4 taken along the line AA; Fig. 6 is a cross section of an end sleeve forming part of the member of Fig. 4; Fig. 7 is a cross section of a lock ring or collar forming part of the member of Fig. 4; and Fig. 8 is a cross section of a mid-sleeve forming part of the member of Fig. 4.

Referring now to the drawings, the figures show an embodiment of a drill string member 10, best shown in Fig. 4, that includes a tubular body 12, best shown in Fig. 1. Referring particularly to Fig. 1, the body 12 includes connection means in the form of a pin connection 14 at one end of the body 12, and a box connection 16 at the other end of the body 12, as is common in the art. The connection means 14, 16 allows the member 10 to be coupled into a drill string in the conventional manner. A drill string generally comprises a number of stands of drill pipe (not shown) that are normally coupled together using threaded connections, and a drill bit located at the lower end of the string.

The body 12 includes a longitudinal throughbore 18 to provide for the passage of fluids therethrough, as is conventional in the art, so that drilling mud or the like can be pumped through the drill string to the drill bit.

The tubular body 12 has an outer surface 12o that includes a first portion 20 that is provided with a plurality of cups 22. The cups 22 generally comprise hemi-spherical indentations in the outer surface 12o of the body 12. A second portion 30 is provided in the outer surface 12o that includes a plurality of cups 32. Cups 32 are similar to cups 22, and are also hemi-spherical indentations in the outer surface 12o of the body 12.

The cups 22 are best shown in Fig. 2, which is a section through the body 12 along the line AA in Fig. 1, and the cups 32 are best shown in Fig. 3, which is a section through the body 12 along the line BB in Fig. 1. The cups 22, 32 are shaped and dimensioned to accommodate a bearing 28 in each cup 22, 32. The bearing 28 is typically a ball bearing (i.e. a sphere), but other types of bearing may also be used, such as a roller bearing (i.e. a cylinder), with appropriate shapes of cup that receive the bearing. Referring again to Fig. 1, the body 12 has an annular shoulder 24 that is located above the first portion 20 in use. The outer surface 12o is also provided with a threaded portion 26 that is located below the second portion 30 of the body 12 in use.

Referring now to Fig. 6, there is shown in cross section an end sleeve 36 that has an inner bore 38 that is of substantially the same diameter as the diameter of the first portion 20 of the body 12. The end sleeve 36 includes a first side 40 that is adapted to engage the shoulder 24 in use of the member 10. The end sleeve 36 is also provided with a cupped edge 42 at a second end 44, the cupped edge 42 being of substantially the same radius as cups 22, 32. The radius of the cups 22, 32 is slightly larger than the radius of the bearings 28 so that the bearings 28 can be received therein. The cupped edge 42 engages an outer surface of the bearing 28 in use. Two end sleeves 36a, 36b are typically provided, as will be described with reference to Fig. 4.

A lock collar 50, best shown in Fig. 7, includes a threaded bore 52. The threads of the bore 52 are adapted to engage the threads of the threaded portion 26 of the body 12 in use.

Referring now to Fig. 8, there is shown a mid-sleeve 56. The mid-sleeve 56 is provided with a stepped bore 58 that includes a first portion 60 that is of substantially the same diameter as the first and second portions 20, 30 of the body 12, and a second portion 62 that is of a larger diameter. The mid- sleeve 56 includes a first end 64 and a second end 66, where the second end 66 is provided with a cupped edge 68, the radius of the cupped edge 68 being substantially the same as the radii of the cups 22, 32. The cupped edge 68 is substantially the same as cupped edge 42 and is also designed to engage an outer surface of the bearings 28 in use. Two mid-sleeves 56a, 56b are typically provided, as will be described.

The cups 22, 32 and the cupped edges 42, 68 on the sleeves 36, 62 can be faced with tungsten carbide or a similar hard material in order to withstand wear on the surfaces of the cups 22, 32 and the cupped faces 42, 68 by the bearings 28. A bearing 28 is provided in each of the cups 22, 32, as best shown in Fig. 5, which is a section through the member 10 taken along the line AA in Fig. 4.

Referring in particular to Fig. 4, the member 10 is assembled by engaging the bore 38 of a first end sleeve 36a so that it slides from the end of the body 12 nearest the pin connection 14 towards the shoulder 24. The end 40a of the first end sleeve 36a abuts the annular shoulder 24, as shown in Fig. 4, to prevent movement of the first end member 36a in a direction parallel to the longitudinal axis of the member 10. A first set of bearings 28a is engaged in the cups 22 at the first portion 20, one bearing 28a being placed in each cup 22. Thereafter, a first mid- sleeve 56a is located over the body 12 so that the cupped end 68a engages an outer surface of bearings 28a. The cupped ends 42a, 68a hold the bearings 28a in place by engagement with the outer surface of the bearings 28a.

A compression spring is optionally positioned between the first mid-sleeve 56a and the second mid- sleeve 56b in order to force the mid-sleeves toward the bearings, and to take up wear on the bearings and the sleeves.

All of the sleeves 36, 56 can preferably be locked with dowel pins or some other similar device against rotation about the body. Each dowel pin can optionally be located in a longitudinally aligned slot on a respective sleeve, so as to allow longitudinal movement of the sleeves relative to the body.

Thereafter, a second mid-sleeve 56b is located over the body 12 so that the end 64b of the second mid- sleeve 56b engages the end 64a of the first mid- sleeve 56a. A second set of bearings 28b is located in the cups 32 at the second portion 30, one bearing 28b being located in each cup 32. A second end sleeve 36b is then located on the body 12 with the cupped end 42b engaging with the bearings 28b. The lock collar 50 is then threadedly engaged with the threads of the threaded portion 26 to retain the various sleeves and bearings in position.

It is to be noted that the bearings 28a, 28b are free to rotate about their own axes, but are prevented from circumferential movement about the body 12 by the cups 22, 32.

In use, the bearings 28a, 28b protrude by around a third of their diameter from the body portions 20, 30, and thus protrude past the outer surfaces of the sleeves 36a, 36b, 56a, 56b and the lock collar 50, so that the bearings 28a, 28b and not the outer surface of the body 12 and member 10, bear s against the innermost surface of the borehole wall or casing etc.

The ability of the bearings 28a, 28b to rotate about their own axes in the cups 22, 32 provides the advantage that less torque is required to rotate the string due to the reduced friction provided by rotation of the bearings 28a, 28b. Additionally, the upward and downward thrust provided on the string can be increased or enhanced due to the lower friction. Indeed, the bearings 28a, 28b also allow for the transfer of more power to the drill bit from the rotation of the string by decreasing friction.

As the bearings 28a, 28b rotate about their own axes in the cups 22, 32, this means that the bearings 28a, 28b are self cleaning as any drill cuttings or other debris that may collect between the bearings 28a, 28b and the cups 22, 32 is ejected by the rotation of the bearings 28a, 28b. Additionally, a circumferential conduit, bore or channel 20b, 30b can be provided in the body 12 between each of the cups 22, 32. The conduits 20b, 30b provide for movement of fluid between the cups 22, 32, and therefore assist in keeping the cups and bearings free from the collection of drill cuttings and other debris. In the case of one or a few of the bearings 28a, 28b being clogged by debris etc that restrains rotation of those bearings, this is not detrimental to the operation of the member 10, as the remainder of the bearings 28a, 28b can still provide a reduction in the frictional forces.

In the event that a large number of the bearings 28a, 28b do become clogged so that they can no longer rotate around their own axes, the lock collar 50 can be disengaged from the threaded portion 26 and the member 10 stripped down in the reverse process from its construction as described above with reference to Fig. 4. It will be appreciated that the lock collar 50 can be replaced by, for example, a heat sensitive ring (not shown) or a circlip. The lock collar, the heat sensitive ring or the circlip need not be completely annular in construction.

It is to be noted that the rows of cups 22, 32 are circumferentially offset with respect to one another by a suitable amount, which can be, for example, around half the width of a cup, as shown in particular in Figs 2 and 3. In other words, a joint 70 between adjacent cups 32a, 32b in one race is aligned with the centre of a cup 22a in the other race, which provides the advantage that the weight of the tool is supported by at least three bearings 28a, 28b, particularly when the member 10 is being used in a highly deviated or horizontal borehole.

The member 10 also provides other advantages in highly deviated and horizontal boreholes. In particular, when the member 10 is being used in a highly deviated or horizontal borehole, it is often lying on its side, similar to the orientation in Fig. 4, with the bearings 28a, 28b engaging an innermost surface of the borehole wall or casing. In this situation, each bearing 28a, 28b can rotate about its own axis to reduce the friction between the member 10 and thus the drill string. As noted above, at least three of the bearings 28a, 28b engage with the borehole wall of casing in use. In some conventional tools where bearings are provided in one or more races, the weight of the member 10 and the string pushes down against the bearings that are in contact with the borehole wall or casing and this downward force prevents the bearings from rotating in the races.

With certain embodiments of the present invention, this is overcome by enablng each bearing 28a, 28b to rotate in its own individual cup 22, 32 so that the bearings 28a, 28b are not forced away from the point of engagement with the borehole wall or casing by the weight of the member 10 and the remainder of the drill string. Each bearing 28a, 28b is restrained within its cup 22, 32 and thus cannot move substantially about the longitudinal axis of the member 10, but can rotate about its own axis to reduce friction. This is advantageous, as it allows the string to rotate more freely even in highly deviated and horizontal wells as the bearings are not pushed around the tool and away from the point of contact due to the weight of the string, thereby increasing the amount of torque available from the same input power by reducing the frictional forces .

The load on the bearings 28 is also distributed more evenly as the load is transferred directly into the body 12 by the bearings 28. This is because the bearings 28 are prevented from rotating about the longitudinal axis of the member 10, and thus they cannot be forced together because of the cups 22, 32. This avoids the load being concentrated on only some of the bearings 28. Also, the load is not transferred to the sleeves, as is the case with some conventional tools.

Certain embodiments of the invention can facilitate a significant reduction in rotary torque and tripping drag, by reducing the friction between the string in which the member is located at the borehole or pre-installed casing etc. The reduction in friction can also reduce casing wear, which is advantageous. Certain embodiments of the invention also allow easier steering capability of the string, and need not have any restrictions on the operating temperature of the string.

Certain embodiments of the invention also provide the advantage that the load is distributed more evenly between the bearings, and is transferred directly to the body by the bearings.

In certain embodiments, maintenance of the member may be performed relatively infrequently as the apparatus functions adequately even when the bearings have been worn through use, or even where a small number of the bearings become clogged by dirt, debris or drill cuttings. Also, the maintenance of the member is kept to a minimum as the bearings are designed to be self cleaning, and this can be enhanced in certain embodiments by providing conduits in the body that allow fluids to circulate between the cups. As a consequence of all these, the cost to replace the bearings and on the time spent stripping down the apparatus to replace the bearings can be saved.

It is to be noted that the particular embodiment shown uses ball bearings, but other forms of bearings may also be used, such as roller bearings. Where roller bearings are used, each roller bearing is preferably mounted on its own individual axis or constrained within a cup having an appropriate shape to permit the roller bearing to rotate about its axis, but prevent it from moving about the longitudinal axis of the member. Modifications and improvements may be made to the foregoing without departing from the scope of the present invention.

Claims

Claims :

1. A tool string member comprising a body having a bearing race on an outer surface of the body, and bearings located in the race, wherein each bearing is held in the race against lateral movement .

2. A tool string member as claimed in claim 1, wherein the tool string is a drill string.

3. A tool string member as claimed in claim 1 or claim 2, having at least one formation in the race to restrain at least some of the bearings from lateral movement in the race.

4. A tool string member as claimed in claim 1 or claim 2, wherein the race comprises a plurality of cups or other receptacles disposed on a common plane for receiving the bearings, with a single bearing being disposed in each cup.

5. A tool string member as claimed in claim 4, wherein the cups or receptacles have a hard facing.

6. A tool string as claimed in any preceding claim, wherein two races are provided, each race being longitudinally spaced from the other.

7. A tool string member as claimed in claim 3, wherein the bearings in one race are circumferentially o^'ffset with respect to the cups or formations in the other.

8. A tool string member as claimed in claim 7, wherein the offset between the cups or formations is approximately equal to the half the distance between the bearings in each race .

9. A tool string as claimed in any preceding claim, wherein the bearings are free to rotate about their own axes, but are restrained from other movement in relation to the body.

10. A tool string member comprising a body having first and second bearing races axially spaced apart, and bearings located in the races, wherein the bearings in the first race are circumferentially offset with respect to the bearings in the second race.

11. A tool string member as claimed in any preceding claim, wherein the bearings are self- cleaning by rotation about their own axes.

12. A tool string member as claimed in any preceding claim, wherein the or each race is provided with bores, channels or other conduits between the bearing positions for the circulation of fluid between the bearings.

13. A tool string member as claimed in any preceding claim, wherein the bearings are ball bearings .

14. A tool string member as claimed in any preceding claim, wherein the bearings are roller bearings.

15. A tool string member as claimed in any preceding claim, wherein each bearing is mounted on its own axis so that it can rotate about its own axis, but is prevented from moving laterally around the member.

16. A tool string member as claimed in any preceding claim, wherein the bearings are retained by at least one sleeve.

17. A tool string member as claimed in claim 16, wherein the sleeve is provided with at least one cupped or chamfered edge.

18. A tool string member as claimed in claim 17, wherein the cupped or chamfered edge has a radius substantially the same as the bearing.

19. A tool string member as claimed in claim 18, wherein the cupped or chamfered edge has a hard facing. 1/5

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