CLEAN OUT TOOL

Abstract: A downhole cleaning tool, comprising, a body (2) or mandrill attachable to a work string or drill string, cleaning elements (9) suitable for cleaning a downhole surface such as the inside wall of well casing or liner or the like, radially extendible members (6) attached to said cleaning elements for operationally mounting said elements on the body, said members being adapted for moving the cleaning elements between a stowed position juxtaposed to the body or mandrill to permit transit of the tool downhole, and a deployed position to permit contact between the cleaning elements and a downhole surface to be cleaned, actuating means (12) provided on the body for moving the radially extendible members to deploy the cleaning elements, and biasing means (22) provided between the cleaning elements and the body for urging the cleaning elements towards said stowed position.

Description: CLEAN OUT TOOL This invention relates to equipment intended for use in downhole environments, such as may typically be found in oil and gas wells. The invention has a particular application in connection with well casing cleaning apparatus . It is now recognised in the art that considerable enhancement can be made to the efficiency of production rates from an oil well or the like by ensuring that the casing and/or casing liner of the well bore is free of debris, scale or other undesirable matter. Accordingly, various cleaning tools have been developed which are adapted specifically for cleaning well casing. For example, tools that incorporate mechanical brushes or scraping blades are well known. Other cleaning tools, typically referred to as circulation tools, are adapted to jet fluid at high velocity or pressure against the casing walls to perform a similar cleaning function. However, in the past, such tools have been limited in their application as a result of varying casing internal diameter throughout the well. As cleaning tools are generally required to be designed such that their outer cleaning members are in contact with the casing wall, they have previously been designed with relatively close tolerances and made suitable for one particular casing internal diameter. An object of the present invention is therefore to provide a clean out tool suitable for use in conjunction with casing of varying diameters. A further object of the invention is to provide a clean out tool for use in a downhole well which may be expanded and/or contracted as required, such as may be necessary for passing an obstacle or step in the well . According to a first aspect of the present invention there is provided a downhole clean out tool comprising a body or mandrel attachable to a work string or drill string, and cleaning members for cleaning the inside wall of well casing or liner, wherein the cleaning members are supported on radially extendible members. Optionally, the cleaning members may be brushes, scraper blades or the like. The tool may further comprise means for affecting a radial or near radial pressure jet of fluid against the casing or liner wall. The fluid may be cleaning fluid, solvent, dissolver or the like. The radially extendible members may comprise arms moveable between a first position where they are contracted in juxtaposition with the mandrel or body, and a second position where they are extended radially, wherein the arms support the cleaning members . Typically the tool further comprises activation means for retracting and/or extending the extendible members. Preferably said activation means is a moveable member . Most preferably the moveable member is hydraulically operated. In one embodiment the moveable member is one or more pistons, wherein a change in fluid pressure initiates movement of the one or more pistons relative to the body of the tool . Movement of the one or more pistons forces said extendible members to move between the first and second positions. Preferably the pistons are housed within piston chambers . Preferably the change in fluid pressure is created by pumping fluid through a through bore in the tools, wherein the pumping of fluid creates a back pressure within the through bore . Most preferably the change in fluid pressure is transferred into the piston chambers. In an alternative embodiment the moveable member is one or more adjustable sleeves which may be selectively adapted to bear on the extendible members, wherein movement of the one or more sleeves forces said members to move between the first and second positions. Movement of the adjustable sleeve may be initiated via fluid pressure . Preferably, the extendible members are biased by biasing means toward their retracted or first position. Movement of the moveable member relative to the body of the tool forces the extendible members to extend radially outwardly, wherein the release of said pressure enables the biasing means to return said extendible members to the retracted or first position. Preferably the biasing means is a spring. In one embodiment, the present invention provides a downhole cleaning tool, comprising, (i) a body or mandrill attachable to a work string or drill string, (ii) cleaning elements suitable for cleaning a downhole surface such as the inside wall of well casing or liner or the like, (iii) radially extendible members attached to said cleaning elements for operationally mounting said elements on the body, said members being adapted for moving the cleaning elements between a stowed position juxtaposed to the body or mandrill to permit transit of the tool downhole, and a deployed position to permit contact between the cleaning elements and a downhole surface to be cleaned, (iv) actuating means provided on the body for moving the radially extendible members to deploy the cleaning elements, and (v) biasing means provided between the cleaning elements and the body for urging the cleaning elements towards said stowed position. Preferably the through bore allows for the passage of fluid, cement or abrasives. Preferably the clean out tool may be used with foam. In order to provide a better understanding of the present invention, an example embodiment will now be described with reference to the following Figures in which: Figure 1 illustrates a clean out tool with cleaning members in a contracted position in accordance with one aspect of the present invention; Figure 2 illustrates a clean out tool with cleaning members in a radially extended position; Figure 3 illustrates a cross-sectional view of the clean out tool; Figure 4 illustrates a means whereby an offset arm connects an hydraulic piston sleeve to a cleaning member; Figure 5 illustrates means whereby an offset arm connects a cleaning member to the central unit of the tool ; Figure 6 is a front elevation of brush pad member; Figure 7 is a side elevation of brush pad member; Figure 8 is a cross sectional view of an alternative activation means of the present invention with the cleaning members in a contracted position; and Figure 9 is a cross sectional view of the activation means of Figure 8 with the cleaning members in an expanded position. Referring firstly to Figure 1, a clean out tool generally depicted at 1, is comprised of a cylindrical body 2 which can be mounted on the lower end of work string or drill string (not shown) . The body 2 also has a central axial bore 3 which extends from input port 4, to the head 5 of the cylindrical body 2. The bore 3 can be used to pump fluids, cement or abrasives through the body 2 of the tool 1. The clean out tool 1 is further comprised of one or more radially extendible members 6, which are separated by a central unit 7 in the depicted embodiment . The radially extendible members 6 are hydraulically operated. The extendible members 6 can be moved from a first retracted position to a second extended position by virtue of a moveable member 8. The moveable member 8 may be a sleeve or a piston. The moveable member 8 controls the radial extension of the extendible members 6 which are comprised of cleaning members 9 which are supported on offset arms 10. The radial extendible members 6 are designed to move from a first closed or contracted position, as shown in Figure 1, to a second open or extended position, as shown in Figure 2. The mechanism for moving the radial extendible members 6 from the contracted position to the extended position is shown in Figure 3. Fluid is pumped through the central bore 3 of the tool 1. This creates a back pressure within the bore 3. This flow induced pressure is then transmitted to the piston chambers 11. The piston chambers 11 which have pistons 12 are attached via pivot arms 10 to cleaning members 9. The cleaning members 9 may be brush pads, scrapers or blades. As pressure enters the chambers 11, the pistons 12 move axially along and relative to the body 2, applying a load to the pivot arms 10. As the pressure increases, the pistons 12 travel further and pivot the arms 10 radially. The tool 1 may also have flushing ports (not shown) which allow cleaning of the cleaning members 9. Figure 4 illustrates an offset pivot arm 10 in position relative to an hydraulically moveable member 8, namely a hydraulically operated piston, and a cleaning member 9. A first end of the offset pivot arm 10 is located within a machined recess 13 on the outer surface of the hydraulic piston 8 and is fixed in place by a pivot pin 14. A second end of an offset pivot arm 10 is attached in similar fashion to one end of a cleaning member 9. The cleaning member 9 is then attached to the central unit 7 of the tool 1 by means of a second offset pivot arm 15, as illustrated in Figure 5. Pivot pins 16 are used to attach the offset pivot arm 15 to the cleaning member 9 and to the central unit 7 via a machined recess 17. In one embodiment, the clean out tool 1 will incorporate brush pads 18 as the cleaning members 9 as illustrated in Figure 6 and Figure 7. These members comprise of an arched backing unit 19 on which are mounted a plurality of brush heads 20. At either end of the arched backing unit 19 are pivot pin locators 21. These pivot pin locators 21 aid the securing of a cleaning member 9 to the central unit 7 and a hydraulically operated piston 8 via pivot pins 16. The extendible members 6 of the clean out tool 1 are usually in the contracted position. Typically the extendible members 6 are biased into the body 2 of the tool 1 by one or more springs 22. When desired, fluid is pumped through the central bore 3 which extends the arms 10 radially. This extended position is maintained as long as the hydraulic pressure created by the fluid is maintained. When fluid flow is stopped or reduced, the bias created by springs 22 in the piston chambers 11 moves the cleaning members 9 back into the collapsed position. As a result the cleaning members 9 translate radially inwards to their initial contracted positions. Extension and retraction can be repeated with no requirement to remove the clean out tool 1 from the downhole environment . Figures 8 and 9 illustrate a further embodiment of the present invention in which like numerals have been used to represent like elements. In this embodiment the pivot arms 10 are provided with a cam surface 23 on the inner surface of the arms adjacent to the body 2 of the tool 1. A cam 24 for cooperation with the cam surface is provided on the body of the tool . The cleaning members 9 are mounted on pivot arms 10 as in the previous embodiment . The free end of each pivot arm is connected to a piston mounted on the body. The pistons are adapted to move in opposite directions upon the application of pressure into the piston chambers. The provision of the cam surface offers advantages in achieving smooth deployment of the cleaning members. As fluid is introduced into the piston chambers, the pressure forces the pistons to move axially along the chambers, parallel to the axis of the body, towards the extendible arms thereby applying a load to the arms 10 to push the arms over the cam on the body of the piston. This urges the arms into their expanded position such that the cleaning members supported thereon are deployed for cleaning debris from the wall of the well or casing or the like. Biasing means which may be in the form of springs 22 are provided within the piston chamber. When pressure is applied within the chamber, the pistons move against the bias and when the pressure is released, the bias urges the pistons to retreat back into the piston chamber thereby pulling the extendible arms and the cleaning members supported thereon back to the rest (stowed) position. In this embodiment, the outer diameter of the brush tool is about 5.4 cm (2 1/8 inch) . In the deployed position, the tool can be used to clean tubing sizes or up to about 14 cm (5 % inches), No. 17 casing. It is envisaged that the tool can be run in conjunction with a Rotoblast tool and that the expansion mechanism described above can be triggered by back pressure created by the Rotoblast tool. Furthermore, the tool can act as a tubing end locator, a tubing anchor or for pipe severance using anchor pads and the Rotoblast tool . The present invention is inherent with significant advantages. The employment of the hydraulic action allows the cleaning members 9 to be expanded at any depth or position within the well bore, and the spacing position of the cleaning members provides 360-degree mechanical cleaning coverage. The cleaning force (and hence efficiency) can be increased or decreased simply by adjusting the flow rate through the tool. Coverage can also be complimented by a high-pressure rotary jetting system, which allow specialised chemicals such as solvents or dissolvers to be applied directly at the well casing. The open design of the tool also has the advantage that it prevents clogging which could hinder the retrieval of the tool after use and permits the use of larger and hence more robust pivot pins and arms. The design of the tool also facilitates the stacking of cleaning members, which allows the efficiency of the device to be improved as required. The brush pads 18 could be changed to incorporate rigid scrapers or omni-directional slips (not shown) , such as are known in the art . Attachment of either of these components extends the range facilities for which this invention can be employed. The tool has the ability to pass through restrictions when in the contracted position. With omnidirectional slips in situ, the tool when activated acts as an anchor, allowing stabilisation for such activities as Tube Cutting. The cleaning members can also be employed to interact with any restrictions or to be incorporated in a Wire Line Entry Guide system. This provides a method for accurate depth measurement within the bore as is known by those skilled in the art. In addition, the large piston area allows the tool to be used with a combination of brush pads, slips or scrapers. This provides an ability to accurately identify target areas. The tool can then be anchored and so provide stabilisation in order to cut the tubular. Being able to ,do all these processes in one trip provides the significant advantage of saving rig time. Alternatively, the tool could be run on a conventional drill string with the moveable members held stationary by means of shear screws (not shown) . This allows for fluid to be circulated through the drill bit without activation of the cleaning members. Should the need arise to clean an area, an applied pressure of a predetermined value would shear the pins allowing the cleaning members to come into contact with the casing wall. The casing could then be scraped hence saving a separate scraper run. In an alternative embodiment, the cleaning members could be modified to encompass a knife configuration (not shown) . Applied pressure to a motor (not shown) within the drill string would activate an anchor section while simultaneously expanding the knives in the lower section. Rotation of the assembly would provide a cutting action. Alternatively, the inclusion of a Rupture Disc Sub (not shown) or a ball activated circulation sub (not shown) in the tool itself or built into the string would allow for cementing operations to be carried out after a tube cutting. This is a common operation in the art, carried out after cutting, and here would have the advantage of being done in one run. Further modifications and improvements may be incorporated without departing from the scope of the invention herein intended.

Claims: CLAIMS 1. A downhole cleaning tool, comprising, (i) a body or mandrill attachable to a work string or drill string, (ii) cleaning elements suitable for cleaning a downhole surface such as the inside wall of well casing or liner or the like, (iii) radially extendible members attached to said cleaning elements for operationally mounting said elements on the body, said members being adapted for moving the cleaning elements between a stowed position juxtaposed to the body or mandrill to permit transit of the tool downhole, and a deployed position to permit contact between the cleaning elements and a downhole surface to be cleaned, (iv) actuating means provided on the body for moving the radially extendible members to deploy the cleaning elements, and (v) biasing means provided between the cleaning elements and the body for urging the cleaning elements towards said stowed position. 2. A downhole cleaning tool according to claim 1, wherein the radially extendible members comprise arms pivotally mounted between the body or mandrill and the cleaning members. 3. A downhole cleaning tool according to claim 1 or 2 , wherein the actuation means comprises one or more adjustable sleeves adapted to bear on the extendible members to force the extendible members to move thereby moving the cleaning elements into the deployed position. 4. A downhole cleaning tool according to claim 1 or 2 , wherein the actuation means comprises one or more pistons wherein a change in fluid pressure initiates movement of the one or more pistons relative to the body of the tool thereby forcing said extendible members to move thereby moving the cleaning elements into the deployed position. 5. A downhole cleaning tool according to claim 4, wherein the body has an inclined surface over which the extendible members are propelled thereby forcing the extendible members to radially extend thereby moving the cleaning elements into the deployed position. 6. A downhole cleaning tool according to claim 4 or 5, wherein the one or more pistons are housed within piston chambers . 7. A downhole cleaning tool according to claim 4, 5 or 6, wherein the change in fluid pressure is created by pumping fluid through a through bore in the tool, wherein the pumping of fluid creates a back pressure within the through bore. 8. A downhole cleaning ' tool according to claim 6 or 7, wherein the change in fluid pressure is transferred into the piston chambers. 9. A downhole cleaning tool according to claim 7 or 8, wherein the through bore allows for the passage of fluid, cement or abrasives. 10. A downhole cleaning tool according to any preceding claim, wherein the cleaning members are brushes, scrapers or blades. 11. A downhole cleaning tool according to any preceding claim, wherein the tool further comprises means for effecting a radial or near radial pressure jet of fluid against the casing or liner wall. 12. A downhole cleaning tool according to claim 11, wherein the fluid is a cleaning fluid, solvent or dissolver . 13. A downhole cleaning tool according to any preceding claim, wherein the biasing member is a spring. 14. A downhole cleaning tool according to any preceding claim, wherein the tool is used with foam.

Inventors: GRAEME GORDON, GRAEME, GORDON
Applicants: GRAEME GORDON, NORTECH SYSTEMS LTD, GRAEME, GORDON, NORTECH SYSTEMS LIMITED
Application year: 2001
Main classification: E21B37
IPC codes: E21B37