AU701439B2 - Bi-directional roller reamer - Google Patents

Description

WO 96/29499 PCT/AU96/00150 -1- BI-DIRECTIONAL ROLLER REAMER This invention relates to a roller reamer of the general type which is used in boreholes, and also to a method of reamer extraction from a borehole.

The invention is an improvement over the Applicant's earlier Australian Patent No 594885 and Application No PM 2305 (now PCT Application No PCT/AU94/00691).

BACKGROUND OF THE INVENTION The Patent 594885 introduced the concept of the use of end blocks retained by wedge blocks, for journalling the rollers of a borehole reamer. That system has been very successful and is also embodied in this invention by way of reference. However this invention is not limited to use with the wedge block bearing and retaining means and can be applicable to roller reamers of other types.

The Application No PCT/AU94/00691 disclosed the use of a piston floating freely in a cylindrical lubricant passage and lying between a bearing surface of a roller and the pressure force exterior of the roller so that the piston would apply the same pressure to lubricant as the external pressure, thereby reducing the pressure differential otherwise existing and in turn retaining the lubricant in the bearing structure. Again, this invention is particularly useful with the subject matter of PCT Application No PCT/AU/94/00691, but is not limited thereto.

A major difficulty which is sometimes encountered is extraction of a borehole reamer from a borehole when it has been partly or fully bored. There are various reasons why the borehole reamer can become locked in a borehole. One reason is the partial collapse of the walls of the borehole, another reason can be the curvature of the borehole which sometimes is required to have a lateral as well as a vertical component of direction, and prior art reamers tend to rigidly engage the surface defining the borehole, and sometimes slight earth movement, due for example to a small earthquake, can dislodge strata of rock or sedimentary layers with respect to one another.

SUMMARY OF THE INVENTION Therefore in one form of the invention there is proposed a bi-directional borehole reamer comprising a body having recess walls defining a plurality of 1 0 recesses extending along the body in an axial direction; a corresponding plurality of reamer rollers contained in respective said recesses, each said roller having a curved outer surface, being rotatable in said body, and said outer surface projecting radially outwardly beyond an outer curved surface of said body, each said roller comprising spaced hard 1 5 studs projecting from said curved outer surface for most of its length; at least one of said roller curved outer surface having a larger diameter portion intermediate its ends and smaller diameter portion at its ends; the configuration being such that said studs gradually and 2 0 progressively ream a borehole defining surface upon reamer rotation and extraction.

In an embodiment of this invention a borehole reamer is provided with reamer rollers each having hard projecting studs spaced along its length, the rollers being of greater length than prior art rollers, each having a major diameter S2 5 which gradually tapers to at least one of its ends which has a minor diameter, i: at least some of the rollers being tapered in both directions to converge towards their ends. They can, for example, be symmetrical about a central equatorial plane, and in use, the studs will gradually ream a bore hole wall if the reamer is rotated as it is retracted.

3 0 The closest prior art known to the Applicant is the British Patent No. 176,048 issued in 1920 to CE Reed of Houston, Texas. This disclosed a set of rotary reamer rollers, each of which was tapered to converge towards its ends, but the rollers were short, the taper angles steep, and there were no hard studs projecting which could gradually ream the surface of a borehole upon Z/ extraction.

2a BRIEF SUMMARY OF THE DRAWINGS Embodiments of the invention are described hereunder in some detail with reference to, and are illustrated in, the accompanying drawings, in which: Fig 1 shows a double-ended reamer, with minor diameters at both ends, within a bore hole; Fig 2 shows the reamer roller of Fig 1 drawn to a larger scale, wherein the major diameter is located centrally between the ends each having a minor diameter only slightly less than diameter a r r r r r r+ r +rr WO 96/29499 PCT/AU96/00150 -3- Fig 3 shows a second embodiment wherein there are two sets of reamer rollers, one near a downhole end of a borehole, and the other near the fishing neck end; and Fig 4 shows a second embodiment, similar to Fig 3, but illustrating a longer reamer.

In the first embodiment of Figs 1 and 2, a borehole reamer body supports a plurality of reamer rollers 11 in the same manner as described in our aforesaid Australian Patent 594885. Each reamer roller 11 is provided with a plurality of tungsten carbide insert studs 12 projecting from the outer surface 13 for almost the full length of the body 10. The intermediate part of the roller is designated 14, and the roller as illustrated is symmetrical about a central equatorial plane although that is not always essential. The intermediate part 14 has a generally cylindrical outer surface but the outer surface tapers from the larger diameter of the intermediate part 14 to the smaller diameter at the ends 18. The diameter difference is small, in the embodiment illustrated in Fig 2 being from 41 mm at the intermediate part 14 to 38 mm at the ends 18, so that reaming is both gradual and progressive both in downhole directions and during extraction. This is an important aspect of the invention. Although the surfaces can be tapered to converge towards the respective ends, as shown they are each provided with a series of steps 15 of diminishing diameter towards the respective ends of the roller, in order to simplify drilling for studs 12. The tungsten carbide insert studs 12 project both from the central portion 14 and from each of the steps 15. The envelope shape therefore constitutes a larger diameter cylindrical central portion, with two tapered portions extending towards respective ends.

In the event of an anomaly in the surface of a borehole which has been bored, a rotating drill string can ream the surface of the hole as the string is withdrawn, thereby further consolidating the earth material.

WO 96/29499 PCT/AU96/00150 -4- Figs 3 and 4 also illustrate the downhole end of the reamer a body having rollers 11 arranged in a circumferential set of three rollers, as in the first embodiment. However, in some difficult soil conditions, the very gradual diameter reduction from the intermediate part 14 to the ends 18 is likely to inhibit reaming of a partly collapsed or displaced hole wall, and a preliminary reaming operation is useful during extraction of a reamer and borehole bit.

The embodiment of Figs 3 and 4 achieves the preliminary extraction by use of a set of smaller reamer rollers 20, each roller 20 having a large diameter (D1) downhole end, and the curved surface 21 reduces in diameter towards the fishing neck end 22. Dimension D1 is less than dimension D, and dimension d 2 is much less than dimension d, so that there is much more taper (whereas D/d 1.1; Dl/d 2 1.25, approximately as drawn). Thus upon extraction, the smaller reamer rollers, upon rotation, can provide initial reaming of the hole wall. Since, however, upon down hole boring, rollers 11 will have already reamed the hole wall before it is traversed by the reamer rollers 20, there is no need for rollers 20 to be "double ended", with two small diameter ends and one large intermediate diameter part, as with the downhole reamer rollers 11.

In all instances, the ratio of large to small diameters should not exceed and the ratio of large diameter to distance from small diameter should not exceed 0.8, since beyond these limits the required gradual progressive reaming of a borehole surface will be negated.

Fig 4 illustrates a reamer with two sets of rollers 11 and 20. It is noteworthy that the rollers 20 near the fishing neck end are staggered with respect to the rollers 11 near the downhole end of body 10, and further that the ratio large diameter to the distance between that diameter and the small is about 0.6. In other respects the Fig 4 reamer is similar to that shown in Fig 3, and the numerals on those figures designate similar features.

WO 96/29499 PCT/AU96/00150 A consideration of the above two embodiments will indicate that this invention comprises a simple and effective way of overcoming the frequently encountered problem of extracting a reamer/borehole bit from a borehole.

Claims (9)

1. A bi-directional borehole reamer comprising a body having recess walls defining a plurality of recesses extending along the body in an axial direction; a corresponding plurality of reamer rollers contained in respective said recesses, each said roller having a curved outer surface, being rotatable in said body, and said outer surface projecting radially outwardly beyond an outer curved surface of said body, each said roller comprising spaced hard 1 0 studs projecting from said curved outer surface for most of its length; at least one of said roller curved outer surface having a larger diameter portion intermediate its ends and smaller diameter portion at its ends; the configuration being such that said studs gradually and progressively ream a borehole defining surface upon reamer rotation and extraction.

2. A bi-directional borehole reamer according to claim 1 wherein some at least of said rollers are arranged in a spaced circumferential set but not spaced axially from each other. 2 0

3. A bi-directional borehole reamer according to claim 1 wherein said S-reamer rollers are arranged in two sets of circumferentially spaced rollers, said sets being spaced axially from each other.

4. A bi-directional borehole reamer according to claim 3 wherein said reamer has a fishing neck end and a downhole end, one said set of rollers 25 being closer to the fishing neck end than the downhole end and having each roller of smaller diameter than the rollers of the other said set which are closer to the downhole end than the fishing neck end. 9 Sa

5. A bi-directional borehole reamer according to claim 3 wherein said reamer has a fishing neck end and a downhole end; a a .f l a first said set of rollers being closer to the fishing neck end than to the downhole end, the diameters of the rollers of said first set each converging towards said fishing neck end; a second said set of rollers being closer to said downhole end than to said fishing neck end, the diameters of the rollers of said second set each converging from a central portion towards the ends of said second set.

6. A bi-directional borehole reamer according to claim 5 wherein said reamer has a fishing neck end and a downhole end; 1 0 a first said set of rollers being closer to the fishing neck end than to the downhole end, the diameters of the rollers of said first set each converging towards said fishing neck end; a second said set of rollers being closer to said downhole end than to said fishing neck end, the diameters of the rollers of said second set each 1 5 converging from a central portion towards the ends of said second set, the maximum diameters of the rollers of the first said set being less than the maximum diameters of the rollers of said second set.

7. A bi-directional borehole reamer according to claim 3 wherein the ratio of large to small diameters in any one said roller does not exceed 2 0 and the ratio of large diameter to distance from small diameter should not exceed 0.8.

8. A method of extracting a reamer from a borehole comprising rotating a reamer as defined in Claim 1 having reamer rollers during extraction from said borehole, and gradually and progressively reaming a wall of said 2 5 borehole above said reamer with hard studs extending along and projecting from curved surfaces of said rollers.

9. A method according to claim 8 wherein said gradual and progressive reaming is effected by firstly engaging said hard studs projecting from relatively smaller diameter upper ends of said rollers with portion of said bore hole wall, and subsequently engaging said wall portion with further hard studs projecting from relatively larger diameter portions of said rollers downhole of said upper ends, upon said extraction. 8 A method according to claim 9 wherein said reamer comprises two sets of said reamer rollers one above the other; comprising firstly engaging said wall portion with said hard studs of the rollers of the upper of said sets, and subsequently engaging said wall portion with said hard studs of the lower of said sets, and wherein said lower set rollers have larger diameters than said upper set. Dated this 30th day of October 1998 GEARHART UNITED PTY LTD By their Patent Attorneys, COLLISON CO. r r r r r r r r r r r r r r r r r r r :1;