Drilling on gauge sub

Abstract

A drilling on gauge sub including a tubular housing having a first end, a second end and an exterior surface. Coupling means are positioned at both the first end and the second end of the tubular housing to couple the tubular housing to other components of a drill string. At least three cavities are provided in the exterior surface of the tubular housing. Each of the cavities having a first end and a second end. Reamer cutters are secured within each of the at least three cavities. The reamer cutters including cutters mounted on rotatably mounted rollers.

Description

FIELD OF THE INVENTION

The present invention relates to a drilling on gauge sub.

BACKGROUND OF THE INVENTION

As a drill bit wears during drilling, the hole it makes becomes undergauged. When the hole is undergauged there is a danger that the drill string behind the bit will become stuck. In order to minimize the amount of undergauged hole, a sub having reamer cutters is positioned directly behind the drill bit. As the drill bit wears, the reamer cutters of the drilling on gauge sub enlarge the hole made by the drill bit to keep the hole “on gauge”. When the drill bit is replaced due to wear, the drilling on gauge sub is also replaced due to wear of the reamer cutters. A problem currently being experienced when drilling on gauge is high torque loading. This torque loading can become so severe as to result in the drill string becoming stuck in the hole.

SUMMARY OF THE INVENTION

What is required is a drilling on gauge sub that will not create as much torque loading of the drill string.

According to the present invention therefore provided a drilling on gauge sub which includes a tubular housing having a first end, a second end and an exterior surface. Coupling means are positioned at both the first end and the second end of the tubular housing to couple the tubular housing to other components of a drill string. At least three cavities are provided in the exterior surface of the tubular housing. Each of the cavities having a first end and a second end. Reamer cutters are secured within each of the at least three cavities. The reamer cutters including cutters mounted on rotatably mounted rollers.

With the drilling on gauge sub, as described above, the rollers serve as a bearing surface which guides the bit on the downhole drilling motor. This greatly reduces the torque required to drilling a gauged hole with a downhole drilling motor.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to in any way limit the scope of the invention to the particular embodiment or embodiments shown, wherein:

FIG. 1 is a side elevation view, in section, of a drilling on gauge sub constructed in accordance with the teachings of the invention;

FIG. 2 is a side elevation view of a drill string to which the drilling on gauge sub illustrated in FIG. 1 is coupled;

FIG. 3 is a side elevation view in section of a reamer cutter module from the drilling on gauge sub illustrated in FIG. 1;

FIG. 4 is a side elevation view, in section, of the drilling on gauge sub illustrated in FIG. 1, with the reamer cutter module removed; and

FIG. 5 is an end view, in section, of the drilling on gauge sub illustrated in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment, a drilling on gauge sub generally identified by reference numeral 10, will now be described with reference to FIGS. 1 through 5.

Structure and Relationship of Parts:

Referring now to FIG. 1, drilling on gauge sub 10 has a tubular housing 12 with a first end 14, a second end 16 and an exterior surface 18. At both first end 14 and second end 16 of housing 12, there is coupling means 20 to couple tubular housing 12 to other components of a drill string 100. FIG. 2 shows drill string 100 with drilling on gauge sub 10 connected in line. Referring to FIG. 5, there are three cavities 22 in exterior surface 18 of tubular housing 12. Referring to FIG. 4, each cavity 22 has a first end 24 and a second end 25. At first end 24 of cavity 22, there is an undercut locking groove 26. At least three reamer cutter modules 28, are provided to be installed in cavity 22, where, referring to FIG. 1, each reamer cutter module 28 has a first end 30 and a second end 32. First end 30 of reamer cutter module 28 has a projecting tongue 34 adapted to engage locking groove 26 of cavity 22. This arrangement allows reamer cutter module 28 to be inserted into cavity 22, with first end 30 secured by locking groove 26, while second end 32 of reamer cutter module 28 is secured by detachable fasteners 36 within second end 25 of cavity 22. This is done such that projecting tongue 34 of each reamer cutter module 28 remains locked in engagement with locking groove 26, and such that each reamer cutter module 28 is field replaceable by detaching fastener 36 and withdrawing projecting tongue 34 from locking groove 26. Reamer cutter modules 28 include pins 29 to help keep the assembly together during installation and replacement.

Detachable fasteners 36 are bolts 38 which engage threaded apertures 40 in tubular housing 12. A debris cover 40 may also be positioned over each bolt 38 which is adapted to shield bolt 38 from debris 42, shown in FIG. 2. Again referring to FIG. 1, debris cover 41 may be held in place by a spring pin 44.

Referring now to FIG. 3, reamer cutter module 28 is shown to include cutters 46 rotatably mounted on rollers 48. Rollers 48 are cylindrical rollers oriented substantially parallel to the longitudinal axis 50 of tubular housing 12. Carbide spacers 52 are positioned at each end 54 of cylindrical rollers 48 to serve as wear surfaces and transmit axial loads. Rollers 48 rotate on radial bearings 56, which are positioned within a lubricant filled bearing chamber 58 with seals 60 positioned at each end 62 of bearing chamber 58 to contain lubricant 66. A lubricant supply passage 68 is in communication with bearing chamber 58 with a piston 70 positioned in lubricant supply passage 68. Piston 70 has a first face 72 and a second face 74. First face 72 engages lubricant 66 contained within lubricant supply passage 68. Second face 74 is exposed to pressure from drilling fluids such that the pressure exerted upon second face 74 of piston 70 causes piston 70 to move in lubricant supply passage 68 with first face 72 of piston 70 urging lubricant 66 into bearing chamber 58.

Operation:

The use of drilling on gauge sub 10 will now be discussed with reference to FIGS. 1 to 5. Referring now to FIG. 1, reamer cutter modules 28 are installed in housing 12. Referring to FIG. 2, drilling on gauge sub 10 is coupled by coupling means 20 into drill string 100. During drilling, drilling on gauge sub 10 ensures that the hole 78 drilled is the proper gauge. Rollers 48 serve as a bearing surface which reduces friction while guiding the drill bit of the downhole drilling motor. Referring again to FIG. 1, when reamer cutter modules 28 are to be replaced, such as when they are worn, or during a regular maintenance schedule, they are removed by removing debris cover 40 held in place by spring pin 44 and then removing bolt 38. First end 30 of reamer cutter module 28 is then free to be removed by disengaging projecting tongue 34 from locking groove 26. Another reamer cutter module 28 may then be installed by reversing the procedure.

The drawings accompanying this application illustrate three cavities. It will be appreciated that there could be more than three cavities—with configurations of four, five, six, etc. The drawings accompanying this application illustrate one type of cutter. It will be appreciated by one skilled in the art that different cutters are used for hard formations than for soft formations. Since the tool is field serviceable, it may be desirable to switch to different types of cutters when the tool is used in different formations. Alternatively, one can have an even number of cavities (four, six, or eight) with the cutters alternating around the circumference of the tool between hard formation cutters and soft formation cutters. This alternating configuration would be suitable for both soft and hard formations.

In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.

It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention as hereinafter defined in the Claims.

Claims

1. A drilling on gauge sub, comprising:

a tubular housing having a first end, a second end and an exterior surface;

coupling means at both the first end and the second end of the tubular housing to couple the tubular housing to other components of a drill string;

at least three cavities in the exterior surface of the tubular housing, each of the cavities having a first end and a second end;

reamer cutters positioned in each of the at least three cavities, the reamer cutters including cutters mounted on rotatably mounted rollers.

2. The drilling on gauge sub as defined in claim 1, wherein the reamer cutters are in the form of replaceable modules detachably secured in the cavities by fasteners.

3. The drilling on gauge sub as defined in claim 2, wherein

an undercut locking groove is positioned at the first end of each of the cavities;

each reamer cutter module having a first end and a second end, the first end the each reamer cutter module having a projecting tongue adapted to engage the locking groove of one of the cavities;

detachable fasteners securing the second end of each of the reamer cutter modules within the second end of one of the cavities so that the projecting tongue of each reamer cutter module remains locked in engagement with the locking groove, each reamer cutter module being replaceable by detaching the fastener and withdrawing the projecting tongue from the locking groove.

4. The drilling on gauge sub as defined in claim 1, wherein the rollers are cylindrical rollers oriented substantially parallel to the longitudinal axis of the tubular housing.

5. The drilling on gauge sub as defined in claim 4, wherein carbide spacers are positioned at each end of the cylindrical rollers to serve as wear surfaces and transmit axial loads.

6. The drilling on gauge sub as defined in claim 3, wherein the detachable fasteners are bolts which engage threaded apertures in the tubular housing.

7. The drilling on gauge sub as defined in claim 6, wherein a debris cover is positioned over each of the bolts, the debris cover being adapted to shield the bolt from debris.

8. The drilling on gauge sub as defined in claim 7, wherein each debris cover is held in place by spring pins.

9. The drilling on gauge sub as defined in claim 1, wherein the rollers rotate on radial bearings.

10. The drilling on gauge sub as defined in claim 9, wherein the radial bearings are positioned within a lubricant filled bearing chamber with seals being positioned at each end of the bearing chamber to contain lubricant.

11. The drilling on gauge sub as defined in claim 10, wherein a lubricant supply passage communicates with the bearing chamber, a piston being positioned in the lubricant supply passage, the piston having a first face and a second face, the first face engaging lubricant contained within the lubricant supply passage, the second face being exposed to pressure from drilling fluids, such the pressure; exerted upon the second face of the piston causes the piston to move in the lubricant supply passage with the first face of the piston urging lubricant into the bearing chamber.

12. A drilling on gauge sub, comprising:

a tubular housing having a first end, a second end and an exterior surface;

a first coupling at the first end and a second coupling at the second end of the tubular housing, the first coupling and the second coupling being adapted to couple the tubular housing to other components of a drill string;

more than two cavities in the exterior surface of the tubular housing, each of the cavities having a first end and a second end, an undercut locking groove being positioned at the first end of each of the cavities;

replaceable reamer cutter modules detachably positioned in the cavities, each reamer cutter module having a first end and a second end, the first end the each reamer cutter module having a projecting tongue adapted to engage the locking groove of one of the cavities, detachable fasteners securing the second end of each of the reamer cutter modules within the second end of one of the cavities so that the projecting tongue of each reamer cutter module remains locked in engagement with the locking groove, each reamer cutter module being replaceable by detaching the fastener and withdrawing the projecting tongue from the locking groove, each reamer cutter module including rotatably mounted cylindrical rollers which rotate on radial bearings and are oriented substantially parallel to the longitudinal axis of the tubular housing, cutters projecting from and being spaced around the outer circumference of the rollers;

the radial bearings being positioned within a lubricant filled bearing chamber with seals being positioned at each end of the bearing chamber to contain lubricant; and

a lubricant supply passage communicates with the bearing chamber, a piston being positioned in the lubricant supply passage, the piston having a first face and a second face, the first face engaging lubricant contained within the lubricant supply passage, the second face being exposed to pressure from drilling fluids, such the pressure; exerted upon the second face of the piston causes the piston to move in the lubricant supply passage with the first face of the piston urging lubricant into the bearing chamber.

13. The drilling on gauge sub as defined in claim 12, wherein carbide spacers are positioned at each end of the cylindrical rollers to serve as wear surfaces and transmit axial loads.

14. The drilling on gauge sub as defined in claim 12, wherein the detachable fasteners are bolts which engage threaded apertures in the tubular housing.

15. The drilling on gauge sub as defined in claim 14, wherein a debris cover is positioned over each of the bolts, the debris cover being adapted to shield the bolt from debris.

16. The drilling on gauge sub as defined in claim 15, wherein each debris cover is held in place by spring pins.

17. A method of drilling on gauge with a downhole drilling motor assembly, comprising the steps of:

securing a drilling on gauge sub having rollers on which are secured cutters adjacent to a drill bit end of the downhole drilling motor assembly; and

using the cutters to ream the hole, while the rollers concurrently guide the movement of the drilling motor assembly and reduce friction with the hole.