DRILL STRING MEMBER WITH BEARINGS

Abstract: A drill string member comprising a body (1), and bearing races (5) around the circumference of the member. In certain embodiment, the presence of spherical bearings (25) on the surface of the member reduces radial torque and vertical drag to enable easier operation of the drill string. Advantages of one embodiment includes a reduction in the wear or breakages of the components used in drilling.

Description: DRILL STRING MEMBER WITH BEARINGS This invention relates to string member, and particularly one which is adapted to reduce drag and torque on the drill string. In oil and gas well drilling it is generally known to rotate a drill string or a portion thereof in order to impart torque to the drill bit at the end. In addition, the drill bit is generally forced into and out of the bore hole as part of the drilling operation. Very often the frictional forces on the drillstring seize the string in the bore, and many solutions have been proposed to the problem of stuck drill string, as it involves great effort and lost production to remedy this. According to the present invention there is provided a drill string member comprising a body and one or more bearings on the outer surface of the body. The drill string member may be suitable for making up into a rotating or non-rotating drill string, to facilitate rotation in the bore or to facilitate axial displacement of non-rotating strings during their insertion into and withdrawal from the bore. Preferably the body member and bearings may be attached to a stand of drillpipe. In some embodiments the bearing may be incorporated within the outer surface of the drillpipe, which forms the body. In a preferred embodiment the body has a bearing race on its outer surface and one or more bearings which can move in the bearing race. Preferably the bearing race is an annular groove arranged perpendicular to the long axis of the body. Preferably there is more than one race provided and the races are preferably parallel to one another, and perpendicular to the axis of the body. The races are preferably continuous so that the bearings are free to move through 360° of the race as well as being free to rotate on their axes in the race. The bearings are preferably ball bearings (ie spheres). In such embodiments vertical drag and radial torque are reduced. Alternatively the bearings may be roller bearings (ie cylinders) or any suitable type of bearing. The bearings are preferably retained in the race by overcentre side walls so that the bearings are permitted to protrude from the race beyond the outer surface of the body to a small extent in order to bear against the inner surface of a well bore or casing, and are preferably retained in place by a moveable sleeve which abuts the bearings on one side and by a shoulder which abuts the bearings on the other. The sleeve and shoulder preferably provide abutments which extend around the centre of the bearings so as to retain them in the bearing race when the tool is assembled. Alternatively the bearings may be retained by an first upper and a second lower sleeve. Optionally there can be more than one sleeve. Each sleeve is typically provided with one or more seals such as o-ring seals in order to restrict the ingress of drill cuttings and other debris. The sleeve (s) are preferably spring-loaded so as to force the bearings into the race and to take up any play therein, and the loading of the spring is preferably adjustable. In a preferred embodiment there are two sleeves or a multiple of two sleeves such as 4 or 6 etc. Most preferably a spring or other resilient buffer is provided between each pair of sleeves. Preferably the spring extends longitudinally or circumferentially between each pair of sleeves. At an opposite edge, each sleeve preferably has a shoulder which abuts the bearings. Preferably the spring (s) keep the sleeves in contact with the bearings. A snap-on or shrink-on lock ring such as a heat sensitive shrink ring or a screw-on collar or lock ring or a circlip can be used to retain the sleeves, the bearings and optionally the spring forcing the sleeves against the bearings. Preferably all components of the invention comprise steel. Most preferably contact surfaces of the components of the invention are protected with a hard facing material such as tungsten carbide. Certain embodiments of the invention provide the advantage that the bearing races are self-cleaning thereby reducing the level of maintenance to free stuck bearings, and in certain embodiments all bearings can be released for cleaning by manipulation of very few parts of the apparatus. An embodiment of the present invention will now be described by way of example and with reference to the accompanying drawings, in which :- Fig 1 shows a side view of one embodiment of the invention; Fig 2 shows a body of the Fig 1 embodiment; Fig 3 shows an upper sleeve of the Fig 1 embodiment; Fig 4 shows a lower sleeve of the Fig 1 embodiment; Fig 5 shows a lock ring of the Fig 1 embodiment; Fig 6 shows a bevel spring of the Fig 1 embodiment; Fig 7 shows a bearing of the Fig 1 embodiment; and Fig 8 shows a side view of a screw-on lock ring used with a different embodiment; and, Fig. 9 shows a front view and sectional view of a further embodiment. Referring now to the drawings, a drill string member has a tubular body 1 having a box and pin section at respective ends as is common in the art and a through bore 2. The tubular body 1 has an outer surface with a first bearing race 5 cut in an annular ring around the outer surface of body 1 perpendicular to the axis of the through bore 2. The first bearing race 5 is bounded on its upper surface by a shoulder 5s which extends in part downwards towards the lower end of the tool from the upper end of the race 5, the purpose of which will be explained below. A second bearing race 6 of similar construction (apart from the upper shoulder 5s) is provided lower down the tool body 1, and annular grooves 10 are provided between the bearing races and below the second race 6 for receiving o-rings . A further annular groove 11 is provided below the lowermost o-ring groove for receiving a lock ring. A first annular sleeve 15 comprises an annular band of steel with cupped upper and lower edges 16u, 161. The cupped edges, 16u, 161 each have an outer shoulder 16s which extends upwardly and downwardly respectively of the sleeve 15. A lower sleeve 20 has an upper cup 21 with a similar upwardly pointing shoulder 21s, and an inner rabbet 23 at its lower surface to receive a bevel spring to be described. The bearing races 5 and 6, and the cups 16 and 21 on the sleeve 15 and 20 are faced with tungsten carbide or a similar hard facing material in order to withstand wear on the surfaces of the races and sleeves by the bearings . The tool is assembled by placing o-rings 12 into annular grooves 10 and threading the upper sleeve 15 onto the lower end 11 of the body. The spherical bearings 25 are then inserted into the upper race 5, and are held in place by the overcentre opposing shoulders 5s on the body 1 and similar shoulders 16s on the upper sleeve 15. The upper sleeve 15 is wide enough to hold the bearings 25 in the upper race and provides a second shoulder 16s adjacent to the lower race 6. The lower sleeve 20 is then threaded onto the lower end 11 of the body and the bearings 75 can be inserted into and retained within the lower race 6 between the lower shoulder 16s of the first sleeve 15 and the upper shoulder 21s of the second sleeve 20 in a similar manner to the first set of bearings 25. The rabbet 23 accommodates an annular bevel spring 27 which is threaded onto the lower end of the body 11 in the same way, and the annular lock ring 30 of expandable metal is heated to expand its diameter, offered up onto the lower end of the body 11 and left to cool in place in the lowermost annular groove 11 until it engages with the groove and maintains the spring 27 in compression between it and the rabbet 23 on the lower sleeve 20. By the upward force exerted on the lower sleeve 20 by the spring 27, the bearings 25 are pressed into the races 5, 6 and play is taken up, but the bearings 25 are free to move circumferentially around the annular races 5, 6 without much resistance. In use, the bearings 25 protrude by around a third of their width from the races 5, 6 and the innermost surface of the well bore or casing etc is therefore contacted by the bearings 25 rather than the outer surface of the tool body 1. The freedom of the bearings 25 to move in the races 5, 6 means that less torque is needed to rotate the string due to the lower friction, and the upward and downward thrust on the string can similarly be enhanced due to the lower friction. Certain embodiments of the invention permit the transfer of more power to the bit from the motor. The o-rings 12 resist the ingress of drill cuttings etc behind the sleeves 15, 20 and the fact that the races 5, 6 are annular without impediment to circumferential movement of each ball around the annular ring of each race 5, 6 means that the races 5, 6 are self cleaning in the event that any drill cuttings or any debris enters them. For maintenance, the ring 30 is heated to expand it and is thereafter removed from the groove 11, and the tool is stripped down in reverse process from its construction as described above. The heat sensitive ring 30 can be replaced by a circlip and need not be completely annular. A screw-on collar 31 with an internal screw thread can be used on a modified body la shown in Fig. 8 instead of a circlip or shrink ring 30. The inner threads on the collar 31, mates with co-operating threads on the outer surface of the body la below the lowermost o-ring groove 10, so that the collar 31 can be screwed onto the body la to retain the spring 27 and sleeve 20 in place. Certain embodiments of the invention can provide a significant reduction in rotary torque and tripping drag, and can reduce casing wear. Some embodiments of the invention allow easier steering capability of strings, and need not have any restrictions on their operating temperature. An alternative embodiment is shown in Fig. 9. The sleeves are provided in pairs 115, 120 and 150, 160. A circumferentially extending annular resilient buffer (not shown) or one or more separate longitudinally extending springs 153 are provided between suitable shoulders 151, 152 on each sleeve 115, 120. The springs 153 abut the shoulders 151, 152 which forces the opposite ends 116u of sleeve 115 and the lower end 1161 of sleeve 120 into contact with the bearings 125 and 175 respectively. The spring mechanism thus ensures contact between the sleeves 115, 120 and the bearings 125, 175 even as the bearings 125, 175 wear and reduce in size through use. A similar buffer (not shown) or springs 154 are provided between the second pair of sleeves 150, 160 to provide a similar function. Features not described in this embodiment are similar to those as described for previous embodiments. In certain embodiments maintenance of the apparatus may be performed infrequently as the apparatus functions adequately even when the bearings have been worn through use. Consequently, the cost to replace the bearings and on the time spent stripping down the apparatus to replace the bearings may be saved. Modifications and improvements can be incorporated without departing from the scope of the invention.

Claims: Cla ims 1. A drill string member comprising a body and one or more bearings on the outer surface of the body. 2. A drill string member as claimed in claim 1, wherein the or each bearing is held in a bearing race on the body. 3. A drill string member as claimed in claim 2, wherein the bearing race is an annular groove. 4. A drill string member as claimed in either claim 2 or claim 3, having more than one bearing race. 5. A drill string member as claimed in any one of claims 2 to 4, wherein the race(s) are perpendicular to the axis of the body. 6. A drill string member as claimed in any one of claims 2 to 5, wherein the races are continuous. 7. A drill string member as claimed in any preceding claim, wherein the bearings are spheres. 8. A drill string member as claimed in any one of claims 1 to 6, wherein the bearings are cylinders. 9. A drill string member as claimed in any one of claims 2 to 8, wherein the bearings are retained in the or each race by overcentre side walls in the race. 10. A drill string member as claimed in any preceding claim, wherein the bearings are retained in place by at least one sleeve which abuts the bearings on at least one side. 11. A drill string member as claimed in claim 10, comprising more than one sleeve. 12. A drill string member as claimed in claim 10 or claim 11, wherein the or each sleeve is provided with one or more seals. 13. A drill string member as claimed in any one of claims 10 to 12, wherein the or each sleeve is spring-loaded. 14. A drill string member as claimed in any preceding claim, wherein at least one shoulder or the body abuts the bearings on at least one side. 15. A drill string member as claimed in any one of claims 10 to 14, wherein a retaining member is used to retain the or each sleeve. 16. A drill string member as claimed in claim 15 wherein the retaining member is a snap-on or shrink-on lock ring, a screw-on collar, a lock ring or a circlip. 17. A drill string member as claimed in any one of claims 2 to 16, wherein the bearings and/or the races are lubricated by mud ingress. 18. A drill string member as claimed in any preceding one of claims 2 to 17, wherein the bearing races are self-cleaning. 19. A drill string member as claimed in any preceding claim, wherein bearings can be released for cleaning. 20. A drill string member as claimed in any preceding claim comprising a length of drill pipe. 21. A drill string member as claimed in any one of claims 1 to 19, comprising a sub or sleeve attachable to a length of drill pipe.

Inventors: KIDD ROBERT GORDON, KIDD, ROBERT, GORDON
Applicants: ITS SPECIALIST DRILLING TOOLS, KIDD ROBERT GORDON, ITS SPECIALIST DRILLING TOOLS LIMITED, KIDD, ROBERT, GORDON
Application year: 2000
Main classification: E21B10
IPC codes: E21B17