Wheel assembly

1. An apparatus comprising:

a wheel assembly configured to detachably connect to a downhole tool to thereby reduce friction between the downhole tool and a sidewall of a wellbore through which the downhole tool is conveyed, wherein the wheel assembly comprises:

an axle configured to contact a sidewall of the downhole tool, wherein the axle comprises a first bore extending therethrough;

a wheel rotatably connected with the axle, wherein the wheel comprises a second bore extending therethrough, and wherein rotating the wheel with respect to the axle moves the second bore into and out of alignment with the first bore; and

a fastener configured to extend into the sidewall of the downhole tool to detachably connect the axle to the downhole tool, wherein the second bore is configured to accommodate the fastener therethrough, and wherein the fastener is disposed within and extends out of the first bore.

2. The apparatus of claim 1 wherein the fastener comprises a threaded fastener extending through at least a portion of the axle and out of the axle, and wherein the fastener is configured to threadedly engage a threaded bore extending into the sidewall of the downhole tool to detachably connect the axle to the downhole tool.

3. The apparatus of claim 1 wherein:

the first bore is one of a plurality of first bores;

the fastener is one of a plurality of fasteners; and

rotating the wheel with respect to the axle moves the second bore one at a time into alignment with each of the first bores.

4. The apparatus of claim 1 wherein each of the first bore and the second bore is offset from an axis of rotation of the wheel.

5. The apparatus of claim 1 further comprising the downhole tool, wherein:

the fastener is one of a plurality of fasteners;

the downhole tool comprises a plurality of threaded bores extending into the sidewall of the downhole tool; and

each fastener threadedly engages a corresponding threaded bore to detachably connect the axle to the downhole tool.

6. The apparatus of claim 1 wherein:

the wheel assembly is one of a plurality of wheel assemblies; and

when the wheel assemblies are detachably connected with the downhole tool:

the wheel assemblies collectively define an axial profile having an axis of rotation; and

the axis of rotation is offset from a central axis of the downhole tool.

7. The apparatus of claim 1 wherein:

the wheel assembly is one of a plurality of wheel assemblies;

each wheel rotates about an axis of rotation; and

when the wheel assemblies are detachably connected with the downhole tool, the axes of rotation are offset from a central axis of the downhole tool.

8. The apparatus of claim 1 further comprising the downhole tool, wherein:

the fastener is one of a plurality of fasteners;

the downhole tool comprises a plurality of mounting bores extending into the sidewall of the downhole tool;

the mounting bores are located asymmetrically with respect to a central axis of the downhole tool; and

each fastener engages a corresponding mounting bore to detachably connect the wheel assembly to the downhole tool.

9. A method comprising:

connecting a wheel assembly to a downhole tool to reduce friction between the downhole tool and a sidewall of a wellbore through which the downhole tool is conveyed, wherein:

the wheel assembly comprises an axle and a wheel rotatably connected with the axle;

the downhole tool comprises a threaded bore extending into a sidewall of the downhole tool;

the axle comprises a bore extending therethrough;

the wheel comprises a bore extending therethrough;

the bore of the axle and the bore of the wheel are offset from an axis of rotation of the wheel; and

connecting the wheel assembly to the downhole tool comprises:

disposing the axle against the sidewall of the downhole tool such that the bore of the axle is aligned with the threaded bore;

rotating the wheel with respect to the axle to align the bore of the wheel with the bore of the axle;

inserting a threaded fastener into the threaded bore through the bore of the axle and the bore of the wheel; and

inserting the threaded fastener at least partially into the sidewall of the downhole tool to connect the axle to the downhole tool by threadedly engaging the threaded fastener within the threaded bore to connect the axle to the downhole tool.

10. An apparatus comprising:

a wheel assembly for a downhole tool, wherein the wheel assembly is operable to reduce friction between the downhole tool and a sidewall of a wellbore through which the downhole tool is conveyed, and wherein the wheel assembly comprises:

an axle comprising an outer circumferential groove and a passage extending though the axle;

a wheel disposed around the axle and comprising an inner circumferential groove, wherein the outer circumferential groove and the inner circumferential groove collectively define a circumferential space between the axle and the wheel, and wherein the passage intersects the circumferential space;

a plurality of ball bearings disposed within the circumferential space and configured to reduce friction between the axle and the wheel;

a blocking member disposed within the passage, wherein the blocking member is movable within the passage between a first position in which the ball bearings can be inserted into the circumferential space via the passage and a second position in which the blocking member prevents the ball bearings from exiting the circumferential space via the passage; and

a fastener engaging both the blocking member and the axle when the blocking member is in the second position to prevent the blocking member from moving along the passage from the second position to the first position, wherein the fastener is a threaded fastener comprising a head and a threaded shank, and wherein the threaded shank threadedly engages the blocking member and the head contacts the axle to prevent the blocking member from moving along the passage from the second position to the first position.

11. The apparatus of claim 10 wherein the passage extends laterally through the axle.

12. The apparatus of claim 10 wherein the passage intersects with the outer circumferential groove at an angle ranging between 60 and 120 degrees.

13. The apparatus of claim 10 wherein the first position is a radially inward position of the blocking member with respect to the axle, and wherein the second position is a radially outward position of the blocking member with respect to the axle.

14. The apparatus of claim 10 wherein the blocking member comprises a groove forming a portion of the outer circumferential groove of the axle when the blocking member is in the second position.

15. The apparatus of claim 10 wherein:

the axle further comprises a first retaining feature extending along the passage;

the blocking member comprises a second retaining feature; and

the first retaining feature and the second retaining feature engage to retain the blocking member within the passage while permitting the blocking member to move along the passage between the first position and second position.