US20120006561A1 - Method and apparatus for a well employing the use of an activation ball - Google Patents

Abstract

A system includes a tubular string that is adapted to be deployed downhole in a well and an activation ball. The activation ball is adapted to be deployed in the tubular string to lodge in a seat of the string. The ball includes a spherical body, which is formed from a metallic material that has a specific gravity less than about 2.0.

Description

• This application claims the benefit under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/363,547 entitled, “ALLOY METALLIC ACTIVATION BALL,” which was filed on Jul. 12, 2010, and which is hereby incorporated by reference in its entirety.
TECHNICAL FIELD
• The invention generally relates to a method and apparatus for a well employing the use of an activation ball.
BACKGROUND
• For purposes of preparing a well for the production of oil and gas, at least one perforating gun may be deployed into the well via a deployment mechanism, such as a wireline or a coiled tubing string. Shaped charges of the perforating gun(s) may then be fired when the gun(s) are appropriately positioned to form perforating tunnels into the surrounding formation and possibly perforate a casing of the well, if the well is cased. Additional operations may be performed in the well to increase the well's permeability, such as well stimulation operations and operations that involve hydraulic fracturing, acidizing, etc. During these operations, various downhole tools may be used, which require activation and/or deactivation. As non-limiting examples, these tools may include fracturing valves, expandable underreamers and liner hangers.
SUMMARY
• In an embodiment, a system includes a tubular string that is adapted to be deployed downhole in a well and an activation ball. The activation ball is adapted to be deployed in the tubular string to lodge in a seat of the string. The ball includes a spherical body, which is formed from a metallic material that has a specific gravity less than about 2.0.
• In another embodiment, a technique includes deploying an activation ball in a downhole tubular string in a well. The activation ball includes a spherical body, which is formed from a metallic material that has a specific gravity less than about 2.0. The technique includes communicating the ball through a passageway of the string until the ball lodges in a seat of the string to form an obstruction (or fluid tight barrier); and using the obstruction to pressurize a region of the tubular string.
• Other features and advantages will become apparent from the following description and the appended claims.
BRIEF DESCRIPTION OF DRAWING
• FIG. 1 is a schematic diagram of a well according to an embodiment of the invention.
• FIG. 2 is a flow diagram depicting a technique using an activation ball in a well according to an embodiment of the invention.
• FIGS. 3A,3B and3C are cross-sectional views of an exemplary ball activated tool.
• FIG. 4 is a cross-sectional view of an activation ball in accordance with embodiments disclosed herein.
DETAILED DESCRIPTION
• Systems and techniques are disclosed herein for purposes of using a light weight activation ball to activate a downhole tool. Such an activation ball may be used in awell10 that is depicted inFIG. 1. For this example, thewell10 includes awellbore12 that extends through one or more reservoir formations. Although depicted inFIG. 1 as being a main vertical wellbore, thewellbore12 may be a deviated or horizontal wellbore, in accordance with other embodiments of the invention.
• As depicted inFIG. 1, atubular string20 extends into thewellbore12 and includespackers22, which are radially expanded, or “set,” for purposes of forming corresponding annular seal(s) between the outer surface of thetubular string20 and the wellbore wall. Thepackers22, when set form corresponding isolated zones30 (zones30a,30band30cbeing depicted inFIG. 1, as non-limiting examples), in which may be performed various completion operations. In this manner, after thetubular string20 is run into thewellbore12 and thepackers22 are set, completion operations may be performed in onezone30 at a time for purposes of performing such completion operations as fracturing, stimulation, acidizing, etc., depending on the particular implementation.
• For purposes of selecting a givenzone30 for a completion operation, thetubular string20 includes tools that are selectively operated usingactivation balls36. For the particular non-limiting example depicted inFIG. 1, the downhole tools aresleeve valves33. In general, for this example, eachsleeve valve33 is associated with a givenzone30 and includes asleeve34 that is operated via anactivation ball36 to selectively open thesleeve34. In this regard, in accordance with some embodiments of the invention, thesleeve valves33 are all initially configured to be closed when run downhole. Referring toFIG. 3A in conjunction withFIG. 1, when closed (as depicted inzones30band30c), thesleeve34 covers radial ports32 (formed in ahousing35 of thesleeve valve33, which is concentric with the tubular string30) to block fluid communication between a central passageway21 of thetubular string20 and the annulus of theassociated zone30. Although not shown in the figures, thesleeve valve33 has associated seals (o-rings, for example) for purposes of sealing off fluid communication through theradial ports32. Thesleeve valve33 may be opened by deployment of a givenactivation ball36, as depicted inzone30aofFIG. 1.
• Referring toFIG. 3B in conjunction withFIG. 1, a givenactivation ball36 is deployed from the surface of the well and travels downhole (in the direction of arrow “A”) through the central passageway21 to eventually lodge in aseat38 of thesleeve34 and block acentral passageway39 of thesleeve valve33. Referring toFIG. 3C in conjunction withFIG. 1, when lodged in theseat38, an obstruction (or fluid tight barrier) is created, which allows fluid pressure to be increased (by operating fluid pumps at the surface of the well, for example) to exert a downward force on thesleeve34 due to the pressure differential (i.e., a high pressure “P_high” above theball36 and a low pressure “P_low” below the ball36) to cause thesleeve valve33 to open and thereby allow fluid communication through the associatedradial ports32.
• Referring toFIG. 1, in accordance with an exemplary, non-limiting embodiment, theseats38 of thesleeve valves33 are graduated such that the inner diameters of theseats38 become progressively smaller from the surface of the well toward the end, or toe, of thewellbore12. Due to the graduated openings, a series of varyingdiameter activation balls36 may be used to select and activate a given sleeve valve. In this manner, for the exemplary arrangement described herein, the smallest outerdiameter activation ball36 is first deployed into the central passageway21 of thetubular string20 for purposes of activating the lowest sleeve valve. For the example depicted inFIG. 1, theactivation ball36 that is used to activate thesleeve valve33 for thezone30ais thereby smaller than the corresponding activation ball36 (not shown) that is used to activate thesleeve valve33 for thezone30b. In a corresponding manner, an activation ball36 (not shown) that is of a yet larger outer diameter may be used activate thesleeve valve33 for thezone30c, and so forth.
• AlthoughFIG. 1 depicts a system of varying, fixeddiameter seats38, other systems may be used in accordance with other embodiments of the invention. For example, in accordance with other embodiments of the invention, a tubular string may contain valve seats that are selectively placed in “object catching states” by hydraulic control lines, for example. Regardless of the particular system used, a tubular string includes at least one downhole tool that is activated by an activation ball, which is deployed through a passageway of the string. Thus, other variations are contemplated and are within the scope of the appended claims.
• Removing a givenactivation ball36 from itsseat38 may be used to relieve the pressure differential resulting from the obstruction of the passageway37 (seeFIG. 3C) through thesleeve valve33. A seatedactuation ball36 may be removed from theseat38 in a number of different ways. As non-limiting examples, theactivation ball36 may be made of a drillable material so thatactivation ball36 may be milled to allow fluid flow through the central passageway21. Alternatively, thevalve seat38, thesleeve34 or theactivation ball36 may be constructed from a deformable material, such that theactivation ball36 may be extruded through theseat38 at a higher pressure, thereby opening the central passageway21. As yet another example, the flow of fluid through the central passageway21 may be reversed so that theactivation ball36 may be pushed upwardly through the central passageway21 toward the surface of the well. In this manner, a reverse circulation flow may be established between the central passageway21 and the annulus to retrieve theball36 to the surface of the well. By reversing fluid flow to dislodge theactivation ball36, theactivation ball36 is non-destructably removed from the well so that both theactivation ball36 and the corresponding sleeve valve may be reused.
• When theactivation ball36 is retrieved by flowing fluid upwardly through the central passageway21, theactivation ball36 may have a particular specific gravity so that upwardly flowing fluid can remove theactivation ball36 from theseat38. While the specific gravity of theactivation ball36 may be a relatively important constraint, theactivation ball36 should be able to withstand the impact of seating in theseat38, the building of a pressure differential across theball36 and the higher temperatures present in the downhole environment. The failure of theactivation ball36 to maintain its shape and structure during use may lead to failure of the downhole tool, such as the sleeve valve. For example, deformation of theactivation ball36 under impact loads, high pressure for high temperatures may conceivably prevent theactivation ball36 from properly sealing against theseat38, thereby preventing the effective buildup of a pressure differential. In other scenarios, the deformation of theactivation ball36 may cause theactivation ball36 to slide through theseat38 and to become lodged in thesleeve34, such that it may be relatively challenging to remove theactivation ball36.
• In embodiments whereactivation ball36 is designed to be retrieved by flowing fluid upwardly through the central passageway21, theactivation ball36 may have the following specific physical properties. Specifically, theactivation ball36 may have a particular specific gravity so that the upward flowing fluid can remove theactivation ball36 from theseat38 and carry it upward through central passageway21. While the specific gravity of theactivation ball36 may be a relatively important constraint, theactivation ball36 may also be able to withstand the impact of seating in the downhole tool, the building of a pressure differential across theactivation ball36, and the high temperatures of a downhole environment. Failure of theactivation ball36 to maintain its shape and structure during use may lead to failure of the downhole tool. For example, deformation of theactivation ball36 under impact loads, high pressures, or high temperatures may preventactivation ball36 from properly sealing againstseat38, thereby preventing the effective build up of a pressure differential. In other scenarios, deformation of theactivation ball36 may cause theactivation ball36 to slide through theseat38 and to become lodged in thesleeve34, such that conventional means of removing activation ball112 may be ineffective.
• Traditional activation balls may be solid spheres, which are constructed from plastics, such as for example, polyetheretherketone, or fiber-reinforced plastics, such as, for example, fiber-reinforced phenolic. While a traditional activation ball may meet specific gravity requirements, inconsistency in material properties between batches may present challenges such that the activation balls may be overdesigned so that their strength ratings, pressure ratings and temperature ratings are conservative. In accordance with embodiments of the disclosed herein, theactivation ball36 is a light weight ball, which permits theball36 to have desired strength properties while being light enough to allow removal of theball36 from the well.
• Referring toFIG. 2, thus, in accordance with some embodiments of the invention, atechnique50 includes deploying (block52) a light weight activation ball, such as a metallic activation ball that has a specific gravity less than about 2.0, into a tubular string in a well and allowing (block54) the ball to lodge in a seat of the string. Thetechnique50 includes using (block56) an obstruction created by the activation ball lodging in the seat to increase fluid pressure in the tubular string and using (block58) the increased fluid pressure to activate a downhole tool.
• Referring toFIG. 4, a cross-sectional view of an activation ball in accordance with embodiments disclosed herein is shown.Activation ball200 includes aspherical body202 formed from a metallic material, wherein the metallic material has a specific gravity less than about 2.0. In certain embodiments, the specific gravity ofspherical body202 may be between about 1.0 and about 1.9. The metallic material ofspherical body202 may be a metallic alloy such as, for example, beryllium alloy, aluminum alloy, or magnesium alloy. Beryllium alloys having a specific gravity of about 1.85, aluminum alloys having a specific gravity of about 2.8, and magnesium alloys having a specific gravity of about 1.8 may be used. A magnesium aluminum alloy may also be used, having a specific gravity of about 1.8.
• Acoating206 may be disposed over anouter surface204 ofspherical body202. Coating206 may be formed from a corrosion resistant material such as, for example, polytetrafluoroethylene, perfluoroalkoxy copolymer resin, fluorinated ethylene propylene resin, ethylene tetrafluoroethylene, polyvinylidene fluoride, ceramic material, and/or an epoxy-based coating material. In certain embodiments, coating206 may include Fluorolon® 610-E, available from Southwest Impreglon of Houston, Tex.
• Coating206 may be applied toouter surface204 ofspherical body202 using any method for applying a coating. For example, coating206 may be applied toouter surface204 ofspherical body202 by dippingspherical body202 in the coating material, spraying the coating material ontoouter surface204, or rollingspherical body202 in the coating material. A thickness, t, ofcoating206 may be between about 0.001 and about 0.005 inches. Those of ordinary skill in the art will appreciate that multiple layers of coating material may be applied in stages until a desired thickness ofcoating206 is achieved.
• Alternatively, coating206 may include a plating that is applied toouter surface204 ofspherical body202 such as, for example, zinc plating, nickel plating, or chromium plating. In embodiments wherecoating206 is a layer of plating, thickness, t, may be between about 0.001 and about 0.002 inches. In yet another embodiment, a surface treatment may be performed onsurface204 ofspherical body202 such as, for example, an anodizing or a laser cladding treatment. Surface treatments may also be performed on anouter surface208 ofcoating206 to improve corrosion resistance, abrasion resistance, and surface finish.Activation ball200 includingcoating206 may have an overall specific gravity less than 2.00 and, in certain embodiments, the overall specific gravity ofactivation ball200 may be between 1.00 and 1.85.
• Advantageously, an activation ball formed from a metallic alloy in accordance with embodiments disclosed herein may provide increased bearing strength and impact resistance when compared with traditional activation balls formed from plastic or composite materials. Plastic and composite materials degrade quickly under high pressures and temperatures, and the degradation can be difficult to predict. In contrast, metallic alloys are able to withstand relatively high pressures and temperatures, and material properties of metallic alloys under high pressures and temperatures are well understood. As such, an activation ball in accordance with embodiments disclosed herein may be designed to withstand high temperatures and pressures without overdesigning to account for uncertainties in material behavior. Thus, an activation ball as disclosed herein may be more reliable than a plastic or composite activation ball, and may be more durable in a downhole environment.
• Traditional activation ball materials such as plastics and composites are not easily plated or coated, and as such, a traditional activation ball is not protected from the high pressures and temperatures of a downhole environment. An activation ball in accordance with the embodiments disclosed herein having a spherical body formed from a metallic material can be coated, plated, and/or surface treated to improve properties such as impact and bearing strength, corrosion resistance, abrasion resistance, and surface finish. Because the behavior of metallic alloys under high pressures and temperatures is predictable, as discussed above, activation balls in accordance with the present application can be designed to have less contact area between the activation ball and a corresponding bearing area. As such, activation balls disclosed herein may allow for an increased number of ball activated downhole tools to be used on a single drill string. As a non-limiting example, by using an activation ball described above, approximately twelve fracturing valves (such as sleeve valve34 (FIG. 1), for example) may be used during a multi-stage fracturing process, whereas approximately eight fracturing valves may be used in series with traditional activation balls.
• While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.

Claims (20)

1. A system comprising:

a tubular string adapted to be deployed downhole in a well, the string comprising a seat; and

an activation ball adapted to be deployed in the tubular string to lodge in the seat, the ball comprising a spherical body formed from a metallic material having a specific gravity less than about 2.0.

2. The system ofclaim 1, further comprising a tool comprising the seat, wherein the ball is adapted to lodge in the seat to create an obstruction, where the tool is adapted to be activated in response to fluid pressure created due to the obstruction.

3. The system ofclaim 1, wherein the seat comprises one of a plurality of object catching seats of the string.

4. The system ofclaim 1, wherein the specific gravity is between about 1.00 and about 1.85.

5. The system ofclaim 1, wherein the metallic material comprises a metallic alloy.

6. The system ofclaim 5, wherein the metallic alloy is one selected from a group consisting of beryllium alloy, aluminum alloy, and magnesium alloy.

7. The system ofclaim 1, wherein the ball further comprises a coating disposed over the spherical outer surface of the ball.

8. The system ofclaim 7, wherein the coating comprises a material selected from a group consisting of polytetrafluoroethylene, perfluoroalkoxy copolymer resin, fluorinated ethylene propylene resin, ethylene tetrafluoroethylene, polyvinylidene fluoride, an epoxy-based coating material, and a ceramic material.

9. The system ofclaim 7, wherein a thickness of the material is between about 0.001 and 0.005 inches.

10. The system ofclaim 1, wherein the ball further comprises an anodized outer layer.

11. A method comprising:

deploying an activation ball in a downhole tubular string in a well, the activation ball comprising a spherical body formed from a metallic material having a specific gravity less than about 2.0;

communicating the ball through of the string until the ball lodges in a seat of the tubular string to form an obstruction; and

using the obstruction to pressurize a region of the tubing string.

12. The method ofclaim 11, further comprising using the pressurization to activate a downhole tool.

13. The method ofclaim 11, wherein the communicating comprises flowing the ball through at least one other seat associated with a ball size larger than a size of the ball.

14. The method ofclaim 11, further comprising:

flowing the ball out of the seat and to the surface of the well.

15. The method ofclaim 11, wherein the metallic material has a specific gravity between about 1.0 and about 1.9.

16. The method ofclaim 11, wherein the ball further comprises a coating material adapted to cover an outer surface of the spherical body.

17. The method ofclaim 16, wherein the specific gravity of the spherical ball with the coating material is between about 1.0 and about 1.9.

18. The method ofclaim 11, wherein an outer surface of the spherical ball is surface treated.

19. The method ofclaim 18, wherein the surface treatment comprises at least one selected from a group consisting of an anodizing treatment, a nickel plating treatment, a chrome plating treatment, a ceramic coating treatment, and laser cladding treatment.

20. The method ofclaim 18, wherein the specific gravity of the surface treated spherical ball is between about 1.0 and about 1.9.

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