WO2012150445A2

WO2012150445A2 - Downhole tool

Info

Publication number: WO2012150445A2
Application number: PCT/GB2012/050902
Authority: WO
Inventors: Paul Bernard Lee
Original assignee: BYWORTH, Ian
Priority date: 2011-05-04
Filing date: 2012-04-24
Publication date: 2012-11-08
Also published as: WO2012150445A3; GB201107336D0

Abstract

A downhole tool (2) for applying sealant or other fluid to a surface of a well bore is described. Downhole (2) comprises a body (4) arranged to be located in a well bore, the body (4) comprising an internal chamber (6) arranged to receive a hydraulic working fluid. Deformable sealing means (8) is arranged to expand outwardly from the body (4) in response to an increase of fluid pressure in the internal chamber (6). The deformable sealing means is arranged to substantially isolate a portion (50) of the surface (52) of a well bore to prevent fluid communication with other parts of the surface of the well bore. The downhole tool further comprises at least one nozzle (10) arranged to apply sealant to the portion (50) of the surface of the well bore isolated by said sealing means.

Description

Downhole Tool

The present invention relates to a downhole tool for applying a sealant or other fluid to a surface of a well bore and relates particularly, but not exclusively, to a downhole tool for sealing leaking points in an open formation hydrocarbon well bore or leaking points in a casing of a well bore.

It is desirable to prevent ground water leaking into well bores used for hydrocarbon production. It is also desirable to prevent hydrocarbons from leaching into ground water if there are leaks in a well casing or well casing connections close to the surface where fresh ground water exists. In particular, during completion operations that conduct

perforation of a well casing and/or fracturing of formations, operators frequently encounter areas of a well bore that produce water either from an open formation or leaking parts of cased well. Existing methods of sealing well bores involve pumping and squeezing cement into the well bore zones that produce water and then subsequently drilling out the cement. Another method involves running a casing patch. This is a corrugated sleeve tool loaded with an outer sealant epoxy. A cone is pulled through the corrugated pipe and expanded to help to seal the casing bore.

These methods suffer from the drawback that the leak must be located by a first downhole tool, that tool withdrawn from the well bore and then a second tool to seal the leak be sent down the well bore. This is a time consuming and costly procedure. Furthermore, it is possible that the leak may shift along the well bore making such sealing methods unreliable .

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 tool for applying a sealant or other fluid to a surface of a well bore, the downhole tool

comprising : a body arranged to be located in a well bore, the body comprising an internal chamber arranged to receive hydraulic fluid; deformable sealing means arranged to expand outwardly from the body in response to an increase of fluid pressure in the internal chamber, wherein the deformable sealing means is arranged to substantially isolate a portion of the surface of a well bore to prevent fluid communication with other parts of the surface of the well bore; and at least one nozzle arranged to apply sealant to the portion of the surface of the well bore isolated by said sealing means in response to an increase of fluid pressure in the internal chamber.

This provides the advantage of a downhole tool that can both isolate a leaking portion of a well bore and apply a one or two part sealant to seal the leak. This tool therefore substantially simplifies sealing operations that previously required two different tools and therefore two different work strings to be run in a well bore. In a preferred embodiment, the deformable sealing means comprises at least one elastomeric tubular member mounted to the body, and wherein an internal surface of the or each elastomeric tubular member is in fluid communication with the internal chamber to enable an increase in fluid pressure in the internal chamber to cause the or each said elastomeric tubular member to expand outwardly from the body.

This provides the advantage of a sealing means that can be deployed by a simple increase in pressure in the internal diameter of the tool. This enables operators to mount the downhole tool in a work string and operate the sealing means from the surface by an increase in pressure rather than any other type of mechanical means. This therefore provides a straightforward and low cost method of operation.

In a preferred embodiment, the tool further comprises two elastomeric tubular members disposed at different locations along a longitudinal axis of the body.

This provides the advantage of enabling a section of the wall of a well bore to be isolated between two elastomeric tubular members .

A first end of the or each said elastomeric tubular member may be mounted to a collar member slidably mounted to the body.

This provides the advantage of increasing safety and

reliability of the downhole tool because the slidable collar enables the elastomeric tubular member to collapse when the tool is pulled upwardly to retrieve the tool from a well bore. This minimises the risk of the tool becoming stuck in a well bore.

In a preferred embodiment, the tool further comprises: at least one sealant chamber arranged to provide a supply of sealant to at least one nozzle; and compression means arranged to apply compression to sealant in at least one said sealant chamber and cause the sealant to be dispensed from the respective nozzle in response to an increase in fluid pressure in the internal chamber.

This provides the advantage of a mechanism that enables sealant to be dispensed in response to an increase of

hydraulic pressure in the tool.

In a preferred embodiment, the compression means comprises least one floating piston in fluid communication with both the internal chamber and the respective sealant chamber.

This provides the advantage of a mechanism that enables sealant to be dispensed in response to an increase in work string pressure.

In a preferred embodiment, the tool further comprises valve means arranged to close in response to a pressure drop in the internal chamber to indicate a well bore leak.

This provides the advantage of an apparatus that enables an operator on the surface to immediately detect a leaking part of a well bore or casing. According to another aspect of the present invention, there is provided a method of applying sealant to an inner surface of a well bore, the method comprising use of a downhole tool 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 longitudinal cross sectional view of a downhole tool embodying the present invention;

Figure 2A is a close up of the first half of the tool to the left of arrows A in Figure 1;

Figure 2B is a close up of the second half of the tool of Figure 1 to the right of arrows B in Figure 1;

Figure 3 is a close up longitudinal cross sectional view of the deformable sealing means and nozzles of the tool of Figure 1, showing the deformable sealing means in the collapsed condition; and

Figure 4 is a close up longitudinal cross sectional view corresponding to Figure 3 but showing the deformable sealing means in the outwardly deployed condition.

Referring to Figures 1 to 4, a downhole tool 2 for applying sealant to a surface of a well bore comprises a body 4 arranged to be located in a well bore, the body 4 comprising an internal chamber 6 arranged to receive a hydraulic working fluid. Deformable sealing means 8 is arranged to expand outwardly from the body 4 in response to an increase of fluid pressure in the internal chamber 6, wherein the deformable sealing means is arranged to substantially isolate a portion 50 of the surface 52 of a well bore to prevent fluid communication with other parts of the surface of the well bore. The downhole tool further comprises at least one nozzle 10 arranged to apply sealant to the portion 50 of the surface of the well bore isolated by said sealing means in response to an increase of fluid pressure in the internal chamber.

"Well bore" is intended to mean either an open formation borehole without a casing, or a borehole that has been cased in a manner that will be familiar to persons skilled in the art. Consequently, tool 2 can be used to seal leaking points in a casing of a well bore or seal parts of an open formation bore hole. The seal can be used to either prevent water leaking in to and contaminating hydrocarbon production in a well bore, or alternatively be used to prevent hydrocarbons from leaching into ground water if there are leaks in the casing of the well bore or casing connections close to the surface where fresh ground water exists.

The body 4 comprises an internal chamber in the form of a longitudinal bore 6. The body 4 is interconnected between a top sub 12 and a bottom sub 14 of a work string or drill string as will be familiar to persons skilled in the art. Completion fluid can be pumped along bore 6 by operators on the surface. Deformable sealing means comprises at least one elastomeric tubular member 20 mounted to the body 4. An internal surface 22 of each elastomeric tubular member 20 is in fluid communication with the internal chamber 6 by virtue of a plurality of ports 24 to enable an increase in the fluid pressure in the internal chamber 6 to cause each elastomeric tubular member 6 to expand outwardly from the body as shown in the configuration of Figure 4.

Two elastomeric tubular members 20 may be disposed at

different locations along the longitudinal axis of body 4 to enable a portion 50 of the region between the tool and the well bore to be effectively sealed off from other regions 54 of the well bore.

A first end 26 of each elastomeric tubular member 20 is mounted to a collar 28 slidably mounted to the body 4. The sliding of collar 28 can be seen by comparing the position of collar 28 in Figures 3 and 4. This enables the elastomeric tubular members 20 to expand outwardly and also enables the tubular member 20 to reliably collapse when the tool 2 is pulled out of the well bore. Alternatively, sliding collars 28 are unnecessary if the elastomeric tubular members are formed from a material that enables a large amount of

expansion in response to a fluid pressure increase.

Referring to Figures 1 and 2, sealant chambers 30 provide a supply of sealant to nozzles 10. Two nozzles 10 connected to respective sealant chambers 30 are shown, to enable a two part epoxy sealant to be applied. However, a single chamber and single component sealant could also be used. Furthermore, more than two sealant chambers 30 could be provided on the tool. Compression means 32 is arranged to apply compression to sealant in the chamber 30 to cause sealant to exit the respective nozzle 10 in response to an increase in fluid pressure in internal chamber 6. The nozzles 10 may also comprise check valves (not shown) which are adapted to open when pressure is applied to dispense sealant or other fluid. The check valves help to prevent foreign material entering nozzles 10 and chambers 30.

The compression means comprises floating pistons 34 which form a floating barrier in fluid communication with both internal chamber 6 and sealant chamber 30. Consequently, when the pressure in internal chamber 6 increases, fluid is communicated via ports 36 to floating piston 34 to move floating pistons 34 towards nozzles 10 and dispense sealant through nozzles 10.

Referring to Figures 1, 3 and 4 valve means comprises a check valve 40 arranged to close in response to a pressure drop in the internal chamber 6 to indicate a well bore leak. For example, if the pressure in the string is 300 psi, when the area in the well bore adjacent valve 40 and therefore nozzles 10 and tubular members 20 encounters a perforation or leak in the well bore casing, the pressure drops from 300 psi due to a leak in the casing or formation. After a predetermined fluid flow through valve 40, valve 40 closes and pressure begin to increase in internal chamber 6.

The method of operation of downhole tool 2 will now be described with reference to Figure 4. Downhole tool 2 is mounted in a work string and moved downwardly along a well bore in manner that will be familiar to persons skilled in the art of deployment of downhole tools. At the same time, working fluid such as completion fluid is pumped from the surface to fill the tool 2 and well bore with fluid.

When tool 2 reaches the bottom of the well, or reaches a predetermined point in the well, a ball (not shown) can be dropped to provide a fluid blockage in the work string below tool 2. This causes the annular pressure in the tool to increase. As pressure increases, fluid flows through ports 24 and causes elastomeric tubular members 20 to expand

outwardly. This may involve the movement of sliding rings 28, or in an alternative embodiment the tubular members 20 may be arranged to deploy without the need for sliding rings 28. Fluid also flows through valve 40.

With the elastomeric tubular members 20 deployed, the work string is then pulled slowly upwardly in the well bore. This causes the elastomeric tubular members 20 to slide along the surface 52 of the well bore.

When the tool 2 and valve 40 arrives at a region on the surface 52 at which a leak is located, fluid moving into the leaking point in the well casing or open formation of the wellbore causes a pressure drop in the tool which will be monitored by operators on the surface. Valve 40 is adapted to close in response to such a pressure drop. At the same time, the operators stop pulling the tool 2 upwardly in the well bore a leaking point in the well bore has been located.

A pressure increase can then be applied by the pumps on the surface to increase the pressure in the work string. This causes floating pistons 34 (Figures 1 and 2) to move towards nozzles 10 in chambers 30 to dispense the sealant from nozzles 10 into the portion 50 of the surface 52 of the well bore between the tubular members 20. Once a predetermined amount of sealant has been applied to the surface 52 of the wellbore, the downhole tool 2 can be raised again to locate further leaks and repeat the sealing operation. It can therefore been seen that downhole tool can be used to both locate and seal leaking portions of wellbore. Downhole tool 2 can also be used to dispense acid in a well bore rather than sealant. Acid can be used to breakdown casing cement or breakdown carbonate formations as will be familiar to persons skilled in the art.

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.

For example, the deformable sealing means could comprise a moving mechanical element that moves against and deforms outwardly the deformable part of the sealing means to form a seal, rather than using the direct influence of fluid

pressure on the sealing means to cause outward deformation. This could be accomplished for example by having at least one moveable collar mounted on the body 4 to compress a

deformable tubular element. The moveable collar would be arranged to move in response to an increase in fluid pressure in the internal chamber.

Claims

1. A downhole tool for applying a sealant or other fluid to a surface of a well bore, the downhole tool comprising: a body arranged to be located in a well bore, the body comprising an internal chamber arranged to receive hydraulic fluid; deformable sealing means arranged to expand outwardly from the body in response to an increase of fluid pressure in the internal chamber, wherein the deformable sealing means is arranged to substantially isolate a portion of the surface of a well bore to prevent fluid communication with other parts of the surface of the well bore; and at least one nozzle arranged to apply sealant to the portion of the surface of the well bore isolated by said sealing means in response to an increase of fluid pressure in the internal chamber.

2. A tool according to claim 1, wherein the deformable sealing means comprises at least one elastomeric tubular member mounted to the body, and wherein an internal surface of the or each elastomeric tubular member is in fluid

communication with the internal chamber to enable an increase in fluid pressure in the internal chamber to cause the or each said elastomeric tubular member to expand outwardly from the body.

3. A tool according to claim 2, further comprising two elastomeric tubular members disposed at different locations along a longitudinal axis of the body.

4. A tool according to claim 2 or 3, wherein a first end of the or each said elastomeric tubular member is mounted to a collar member slidably mounted to the body.

5. A tool according to any one of the preceding claims, further comprising: at least one sealant chamber arranged to provide a supply of sealant to at least one nozzle; and compression means arranged to apply compression to sealant in at least one said sealant chamber and cause the sealant to be dispensed from the respective nozzle in response to an increase in fluid pressure in the internal chamber.

6. A tool according to claim 5, wherein the compression means comprises at least one floating piston in fluid

communication with both the internal chamber and the

respective sealant chamber.

7. A tool according to any one of the preceding claims, further comprising valve means arranged to close in response to a pressure drop in the internal chamber to indicate a well bore leak.

8. A method of applying sealant to an inner surface of a well bore, the method comprising use of a downhole tool according to any one of the preceding claims.