GB2516860A

GB2516860A - Downhole expandable drive reamer apparatus

Info

Publication number: GB2516860A
Application number: GB1313801.1A
Authority: GB
Inventors: Paul Bernard Lee
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-08-01
Filing date: 2013-08-01
Publication date: 2015-02-11
Also published as: WO2015015169A3; US20160160578A1; WO2015015169A2; AR097191A1; GB201313801D0

Abstract

The invention relates to a downhole expandable drive reamer 2. The reamer 2 comprises a body 4 defining a longitudinal axis X--X. At least one roller 6 is disposed on the body and is moveable relative to the body 4 between an inwardly retracted condition and an outwardly deployed condition. A thread 8 or other protrusion is formed on at least one roller 6 and is arranged to engage a surface of a well bore to drive the reamer to along the well bore when the roller 6 is in the outwardly deployed condition. The rotational axis R-R of the roller 6 is non-parallel to the longitudinal axis X-X of the body.

Description

Downhole Expandable Drive Reamer Apparatus The present invention relates to a downhole expandable drive reamer apparatus for incorporation into a work string used in the recovery of hydrocarbons from well bores.

Downhole drill strings are used in the oil and gas industry to cut well bores to reach pockets of oil and gas. A drill string comprises lengths of elements called subs which are interconnected to lengthen the drill string as the drill string advances down a borehole.

To meet demand for energy, the drilling of oil and gas wells is becoming more and more complex in order to open up new reserves. Wells are drilled from land directionally and wells are also drilled in deeper and deeper formations. This means that drill strings can stretch up to several kilometres in length and may be curved to facilitate directional drilling.

However, longer, directional drill strings are susceptible to becoming stuck which can cause a catastrophic failure of the drill string.

A particular problem that arises with directional drilling is that the drill string/pipe commonly does not rotate in an operation called "sliding" the pipe. A bit at the end of the string is rotated by a mud motor, but most of the length of the drill sting is stationary which greatly increases friction, This therefore increases the likelihood of the drill string becoming stuck.

A preferred embodiment of the present invention seeks to

overcome the above disadvantages of the prior art.

According to an aspect of the present invention, there is provided a downhole expandable drive reamer apparatus for incorporation into a drill string, the apparatus comprising: a body defining a longitudinal axis; at least one roller moveable relative to the body between an inwardly retracted condition and an outwardly deployed condition; surface engagement means disposed on an outer surface of said at least one roller, the surface engagement means arranged to engage a surface of a well bore to drive the apparatus along the well bore; characterised in that the rotational axis of said at least one roller is non-parallel to the longitudinal axis of the body.

This provides the advantage of an apparatus that can be incorporated into many types a drill string to assist movement of the drill string along a well bore with little intervention from operators on the surface. In particular, this apparatus can help to pull a non-rotating drill string down a hole when positioned on the bottom bearing mandrel of a down hole motor or mud motor, wherein the drill bit would mount to the bottom of the expandable drive reamer apparatus.

It has been found that by providing threaded, studded or rollers comprising some other form of surface engaging protrusion, wherein the rollers rotate about a longitudinal axis which is offset from the longitudinal axis of the body on which they are disposed, the rollers engage the surface of a well bore and pull the drill string along the well bore.

This is advantageous because the only activity required by the operators on the surface is to operate the apparatus to deploy the rollers to the outward condition to engage the surface of the well bore.

In a preferred embodiment, the angle formed between the rotational axis of said at least one roller and the longitudinal axis of the body is more than zero degrees and no more than five degrees.

It has been found that an angle of offset of between 0 and 5 degrees is most effective in providing a downward force on the apparatus to move the apparatus along a well bore.

In a preferred embodiment, said at least one roller is rotatably mounted between two pistons, each said piston being arranged to be moved between an inwardly retracted position in the body and an outwardly deployed condition relative to the body in response to pressurisation of fluid in the body.

This provides the advantage of making the apparatus straightforward for operators on the surface to activate. All that is required is to commence the pumping of fluid along the work string which will automatically deploy the rollers to the outward condition.

In a preferred embodiment, the apparatus further comprises a plurality of rollers disposed at different locations around the body.

The surface engagement means may comprise a thread disposed on an outer surface of said at least one roller.

The surface engagement means may comprise a plurality of protrusions disposed on an outer surface of said at least one roller.

According to another aspect of the present invention, there is provided a drill string comprising a downhole expandable drive reamer apparatus as defined above.

A preferred embodiment of the present invention will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawings, in which: Figure 1 is a side view of a downhole expandable drive reamer apparatus embodying the present invention; Figure 2 is a cross-sectional view taken along line A-A of Figure 1; and Figure 3 is a perspective view of the apparatus of Figures 1 and 2 showing the rollers in the outwardly deployed activated condition.

Referring to Figure 1, a downhole expandable drive reamer apparatus 2 for incorporation into a work or drill string comprises a body 4 defining a longitudinal axis X-X. At least one roller 6 is disposed on the body and is moveable relative to the body 4 between an inwardly retracted condition and an outwardly deployed condition.

Surface engagement means such as a thread 8 is formed on at least one roller 6 and is arranged to engage a surface of a well bore to drive the apparatus to along the well bore when the roller 6 is in the outwardly deployed condition. The rotational axis R-R of the roller 6 is non-parallel to the longitudinal axis X-X of the body as shown in Figure 1.

In the example shown in the drawings, the surface engagement means is shown as a thread 8. However, it has been found that almost any type of outer profile on roller 6 engages the well bore surface and assists advancement of the apparatus along a well bore. For example, protrusions on the outer surface of the rollers 6, such as tungsten carbide studs press fit into the roller 6 have also been found to be effective.

In Figure 1, the angular offset between axes X-X and R-R is shown as 5 degrees, but it has been found that the rollers provide the most downward force if the angle of offset is more than 0 degrees and no thore than 5 degrees. The apparatus 2 is designed to be rotated by a mud motor at high RPM, such as 180 RPM. As a consequence, it has also been found that an offset of greater than 5 degrees could possibly stall the mud motor and advance the drive reamer apparatus 2 at too great a rate. Apparatus 2 is in the form of a sub to be interconnected into a drill string at its lower 4a and upper 4b ends, Each roller 6 is formed on an axle 10 which is rotatably mounted between two pistons 12 and 14.

Referring to Figure 2, a longitudinal bore 16 is provided through the body 4 through which pressurised fluid such as drilling mud can flow. When surface operators pump pressurised fluid through bore 16, inner surfaces 18 of the pistons 12 and 14 are urged outwardly to deploy the pistons 12 and therefore deploy the roller 6 to the outwardly deployed conditions. However it will be apparent to persons skilled in the art that other mechanisms can be used to deploy the rollers outwardly, such as sliding mandrels.

A particular example of the operation of apparatus 2 in in a non-rotational directional drill string in which apparatus 2 is mounted between the bottom bearing mandrel of a mud motor (not shown) and the drill bit (not shown) at the bottom end of a drill string. Apparatus 2 is rotated by the mud motor along with the bit. Rollers 6 are deployed to the outward expanded condition and provide a downward force by engaging and rolling against the walls of the well bore to assist downward advancement. When the string is to be retrieved, the rollers 6 are retracted.

It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims.

Claims

CLAIMS1. A downhole expandable drive reamer apparatus for incorporation into a drill string, the apparatus comprising: a body defining a longitudinal axis; at least one roller moveable relative to the body between an inwardly retracted condition and an outwardly deployed condition; surface engagement means disposed on an outer surface of said at least one roller, the surface engagement means arranged to engage a surface of a well bore to drive the apparatus along the well bore; characterised in that the rotational axis of said at least one roller is non-parallel to the longitudinal axis of the body.
2. An apparatus according to claim 1, wherein the angle formed between the rotational axis of said at least one roller and the longitudinal axis of the body is more than zero degrees and no more than five degrees.
3. An apparatus according to claim 1 or 2, wherein said at least one roller is rotatably mounted between two pistons, each said piston being arranged to be moved between an inwardly retracted position in the body and an outwardly deployed condition relative to the body in response to pressurisation of fluid in the body.
4. An apparatus according to any one of the preceding claims, further comprising a plurality of rollers disposed at different locations around the body.
5. An apparatus according to any one of the preceding claims, wherein the surface engagement means comprises a thread disposed on an outer surface of said at least one roller,
6. An apparatus according to any one of the preceding claims, wherein the surface engagement means comprises a plurality of protrusions disposed on an outer surface of said at least one roller.
7. A downhole expandable drive reamer apparatus for incorporation into a drill string, the apparatus substantially as hereinbefore described with reference to the accompanying drawings.
8. A drill string comprising a downhole expandable drive reamer apparatus according to any one of the preceding claims.