WO2000058595A1

WO2000058595A1 - Reaming stabiliser roller

Info

Publication number: WO2000058595A1
Application number: PCT/AU2000/000232
Authority: WO
Inventors: Adel Ali Bassal
Original assignee: Gearhart Australia Ltd.
Priority date: 1999-03-26
Filing date: 2000-03-23
Publication date: 2000-10-05
Also published as: AUPP946199A0

Abstract

The present invention is for a roller for use with a roller stabiliser used in boreholes. The roller includes an outer symmetrical to its axis of rotation. A first surface of the outer surface is generally parallel to said axis of rotation whilst a second surface or part of the second surface converges towards the axis of rotation. The first surface includes a plurality of hard inserts whilst the said second surface includes a plurality of cutters. Typically the roller is positioned in the reaming stabiliser so that the second surface leads the first in the direction that the roller stabiliser is moving when drilling in a borehole. However, where the roller ends are identical, that is, they have converging surfaces, then the roller assists in cutting through formation both when drilling into the borehole or being moved out of it.

Description

Reaming stabiliser roller

The present invention relates to a reaming stabiliser roller that reams and stabilises the operation of a drill string in a borehole drilling through the earth's surface.

BACKGROUND OF THE INVENTION

In operation boreholes are initially drilled as vertical holes and may then curve to an inclined or horizontal direction. Maintaining of complete control is very important but very difficult to achieve. A borehole drill may, for example, include three cutters or reamers, which are circumferentially spaced from one another. When the drill bit is inclined to the original axis, the space between the cutters can cause erratic or irregular operation in negotiating a curve.

So as to maintain control of the drill string, it is known to use a stabiliser tool, that may have projecting wear pad assemblies or rollers circumferentially spaced around the axis of the stabiliser tool, each roller having hard inserts. In addition it is known to use roller reamers which have different cutter types depending on the formation that is being drilled through and which assist in smoothing or finishing the borehole. For example blade type or sharp cutters on the roller reamers are generally used on soft formations (such as limestone or shale), whilst button or domed type cutters are used on hard and abrasive formations where tungsten carbide inserts act as teeth to fracture the formation.

The problem with using a stabiliser tool with wear pads is that the pads drag (scratch) along the borehole wall resulting in frictional forces being generated and resulting in the drill string being a high torque device. On the other hand if roller stabilisers are used there is less torque required but the total surface area in contact is less leading to a loss of stability. In addition, neither the wear pads or the roller stabiliser have any cutting capability and if they find themselves in an undersize hole, they cannot cut through, leading to jamming of the drill string or it twisting off.

As mentioned above, when a drill string is negotiating a curve, the borehole needs to be generally smooth and free of protrusions. That is, as you go around a corner one needs another cutting capability. Roller reamers provide that function, by having cutters that protrude from the roller and accordingly assist in shaping the borehole. A typical configuration of a drill string includes a drill bit, above which are located the roller reamers (called aggressive roller reamers), and above which are located either roller stabilisers (also known as non-aggressive roller reamers) or wear pad stabilisers. The stabilisers generally extend along the whole drill string typically every 30 metres. The choice of either wear pads or roller stabilisers depends on the formation one is passing through and whether sufficient torque can be provided. If there is sufficient torque than wear pads are used, but if one needs to reduce the torque than roller stabilisers are to be used. However, as already discussed, if these find themselves in undersize holes they can become jammed. The choice as to the combinations of roller reamers and/or stabiliser tools will therefore depend on each individual borehole, where the using an inappropriate configuration can lead to loss of a drill string.

It is therefore the object of the present invention to provide for a stabiliser tool that overcomes at least some of the abovementioned problems or provides the public with a useful alternative by providing for a remaining stabiliser tool.

BRIEF SUMMARY OF THE INVENTION

Therefore in one form of the invention there is proposed a roller for use with a roller stabiliser used in boreholes, said roller including an outer surface symmetrical to the axis of rotation, said outer surface having a first surface that is generally parallel to said axis of rotation and a second surface that converges towards said axis of rotation, said first surface including a plurality of hard inserts, and said second surface including a plurality of cutters.

Preferably said second surface is located at one end of said roller.

Preferably the second surface converges at an angle generally some 9-10 degrees.

Preferably said cutters are domed inserts manufactured from tungsten carbide. They cut through formation by pressing and fracturing the formation they are in contact with.

In preference the cutters are arranged circumferentially on a plane around said axis of rotation.

In preference there are at least three such planes. In preference the cutters are smooth type cutters. These types of cutters are used in soft formations such as limestone or shale.

In preference the cutters are blade type cutters. These types of cutters are also used in soft formations such as limestone or shale.

Preferably the hard inserts on the first surface thereof are tungsten carbide inserts whose outer surface is generally flush with the outer surface of said rollers.

Preferably the first surface further includes a plurality of helical grooves, with said inserts positioned in a helical arrangement on the shoulders between said grooves.

Preferably each shoulder has at least 8 inserts.

In preference there are 10 right hand spiral grooves, each having an angular width of some 36 degrees, and of a depth of several millimetres.

In preference each said roller has a further third surface that converges towards the axis of rotation.

In preference the second and third surface are located at either ends of the roller thereof.

In a further form of the invention there is proposed a rotary reaming stabiliser for use in boreholes including; a body having rollers contained in respective recesses each roller rotating around an axis of rotation about a fixed spindle held at its ends by retaining blocks removably attached to said body; said rollers having an outer surface symmetrical to the axis of rotation, said outer surface having a first surface that is generally parallel to said axis of rotation and a second surface that converges towards said axis of rotation; and said second surface including a plurality of cutters.

Preferably the rollers are positioned in said reaming stabiliser so that the second surface leads the first in the direction that the roller stabiliser is moving when drilling in a borehole. It has been found that when the rollers are positioned so that the second surface is located at the leading end of the roller, the cutters ensure that any formation that may jam the drill string is cutout. In addition a roller that has both ends thereof converging towards the axis of rotation and which has cutters on those surfaces assists in cutting through any formation wither during insertion or removal of the drill string.

In preference the second surface is located at an end of each said roller.

In preference the first surface includes a plurality of hard inserts.

In preference the stabiliser further includes wear pad assemblies.

In a yet further form of the invention there is proposed a rotary reaming stabiliser for use in boreholes including; a body having rollers contained in respective recesses each roller rotating around an axis of rotation about a fixed spindle held at its ends by retaining blocks removably attached to said body; said rollers having a central outer surface symmetrical to the axis of rotation, said outer surface having a first surface that is generally parallel to said axis of rotation; a second surface disposed of at one end of each roller, said second surface converging toward said axis of rotation; and a third surface disposed at the other end of each said roller, said third surface converging towards the axis of rotation; wherein located on said second and third surfaces are cutters adapted to cut into formations.

In preference to further assist in the stabilising of the drill string the reaming stabiliser roller may further include wear pad assemblies.

BRIEF DESCRIPTION OF THE DRAWINGS

Three embodiments of the invention are described hereunder in some detail with reference to and as illustrated in the accompanying drawings, in which:

FIG. 1 is a fragmentary elevation, which illustrates a reaming stabiliser of a drill string, according to a first embodiment;

FIG. 2 is a cross-section taken on line 2-2 of FIG. 1 ; FIG. 3 is an elevation view of a roller according to the first embodiment;

FIG. 4 is a cross-section taken on line 3 — 3 of FIG. 3;

FIG. 5 is an elevation view of a roller according to a second embodiment;

FIG. 6 is an elevation view of a roller according to a third embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the above figures it is to be understood that like elements are described by like numerals in the drawings. There is thus shown a reaming stabiliser tool having a body 10 including a plurality of rollers 12 that are located in recesses 14. The rollers rotate about a fixed spindle (not shown) held at its ends by retaining blocks 16, the blocks attached to said body by screws (not shown) through openings 18.

The rollers have an outer surface including a first surface 20 generally parallel to the axis of rotation and a second surface 22 located at on end thereof that converges with respect to the axis of rotation. A roller may typically be some 15-20 centimetres in length with the length of the second surface being generally about or slightly greater than a quarter of that distance, typically 5-6 centimetres. Typically the converging angle is some 9-10 degrees. The first surface includes a plurality of grooves 24 and a plurality of shoulders 26. The grooves are several millimeters deep. Located on the shoulders 26 are a plurality of hard inserts 28 manufactured form material such as tungsten carbide and which are inserted to be generally flush with the shoulders. In this way, the hard inserts provide for a hard wearing surface that is in direct contact with the borehole wall. The grooves 24 that are arranged in a helical arrangement. In this embodiment there are some 10 grooves, each spiraling through a total angle of 36 degrees. There are a total of 8 inserts arranged on each shoulder, the inserts being located in a staggered configuration. There are thus a total of 79 inserts located on the first surface, with one of the positions being used for a ball race button hole 38.

Located on the second surface are a plurality of cutters. In the first embodiment as shown in Fig.'s 1-4, the cutters are projecting buttons or domes 30 that are particularly adept at reaming through hard formations. Typically the buttons project several ^"millimeters from the second surface, and extend some 4-5 millimeters into the roller. The buttons are spaced circumferentially around the axis of rotation in three rows. In this particular embodiment the most extreme row 32 has some 14 buttons, the middle row 34 some 15 buttons and the inside row 36 some 10 carbide buttons. In use, the roller is placed on the body so that the second surface is closer to the drill string bit, that is, it is the leading end of the roller in the direction of the borehole.

Referring now to the second embodiment as shown in FIG 5 the cutters 40 may be of the blade or smooth type configuration, one that is appropriate for soft shale or limestone. Even though the cutter type has changed the basic configuration of the smooth inserts remains the same. Although not shown, the second surface may equally well include a combination of different cutter types. The size of the buttons located in the different rows, as well as their configuration may also be an adjustable feature.

Fig. 6 shows a third embodiment of the present invention where the reaming stabiliser is a bi-directional type. That is, the roller includes cutters at both ends to assist in cutting formation not only when the drill string is drilling into the bore hole but also when it is being removed. Thus the reaming roller has a central first surface 20 that is substantially parallel to the axis of rotation, a second surface 22 at one end thereof that converges towards the axis of rotation and a third surface 30 at the other end thereof that also converges towards the axis of rotation. Disposed on the second and third surface are cutters so that the stabiliser tool can cut into formation even when the drill string is being removed from the borehole.

The foregoing describes only several embodiments of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.

Claims

1. A roller for use with a roller stabiliser used in boreholes, said roller including an outer surface symmetrical to the axis of rotation, said outer surface having a first surface that is generally parallel to said axis of rotation and a second surface that converges towards said axis of rotation, said first surface including a plurality of hard inserts, and said second surface including a plurality of cutters.

2. A roller for use with a roller stabiliser as in claim 1 wherein said second surface is located at one end of said roller.

3. A roller for use with a roller stabiliser as in either one of claim 1 or 2 wherein the second surface converges at an angle generally some 9-10 degrees.

4. A roller as in any one of the above claims wherein said cutters are domed inserts manufactured from tungsten carbide.

5. A roller as in any one of the above claims wherein the cutters are arranged circumferentially on a plane around said axis of rotation.

6. A roller as in claim 5 wherein there are at least three such planes.

7. A roller as in any one of the above claims wherein said cutters are smooth type cutters.

8. A roller as in any one of the above claims wherein said cutters are blade type cutters.

9. A roller as in any one of the above claims wherein the hard inserts on the first surface thereof are tungsten carbide inserts whose outer surface is generally flush with the outer surface of said rollers.

10. A roller as in any one of the above claims wherein said first surface further includes a plurality of helical grooves, with said inserts positioned in a helical arrangement on the shoulders between said grooves.

11. A roller as in claim 10 wherein each shoulder has at least 8 inserts.

12. A roller as in either one of claims 10 or 11 wherein there are 10 right hand spiral grooves, each having an angular width of some 36 degrees, and of a depth of several millimetres.

13. A roller as in any one of the above claims wherein each said roller has a further third surface that converges towards the axis of rotation.

14. A roller as in claim 13 wherein said second and third surface are located at either ends of the roller thereof.

15. A rotary reaming stabiliser for use in boreholes including; a body having rollers contained in respective recesses each roller rotating around an axis of rotation about a fixed spindle held at its ends by retaining blocks removably attached to said body; said rollers having an outer surface symmetrical to the axis of rotation, said outer surface having a first surface that is generally parallel to said axis of rotation and a second surface that converges towards said axis of rotation; and said second surface including a plurality of cutters.

16. A rotary reaming stabiliser as in claim 15 wherein the rollers are positioned in said reaming stabiliser so that the second surface leads the first in the direction that the roller stabiliser is moving when drilling in a borehole.

17. A rotary reaming stabiliser as in claim 16 wherein said second surface is located at an end of each said roller.

18. A rotary reaming stabiliser as in either claim 16 or claim 17 wherein said first surface includes a plurality of hard inserts.

19. A rotary reaming stabiliser as in any one of claims 16 to 18 further including wear pad assemblies.

20. A rotary reaming stabiliser for use in boreholes including; a body having rollers contained in respective recesses each roller rotating around an axis of rotation about a fixed spindle held at its ends by retaining blocks removably attached to said body; said rollers having a central outer surface symmetrical to the axis of rotation, said outer surface having a first surface that is generally parallel to said axis of rotation; a second surface disposed of at one end of each roller, said second surface converging toward said axis of rotation; and a third surface disposed at the other end of each said roller, said third surface converging towards the axis of rotation; wherein located on said second and third surfaces are cutters adapted to cut into formations.