Patent Publication Number: US-9404330-B2

Title: Method and apparatus for a well employing the use of an activation ball

Description:
This application is a continuation application of co-pending U.S. patent application Ser. No. 13/180,029, entitled “METHOD AND APPARATUS FOR A WELL EMPLOYING THE USE OF AN ACTIVATION BALL,” which was filed on Jul. 11, 2011. This application also claims priority from U.S. Provisional Patent Application Ser. No. 61/364,267 entitled, “HOLLOW METALLIC ACTIVATION BALL,” which was filed on Jul. 14, 2010, and U.S. Provisional Patent Application Ser. No. 61/363,547 entitled, “ALLOY METALLIC ACTIVATION BALL,” which was filed on Jul. 12, 2010. Each of these applications are hereby incorporated by reference in their entireties. 
    
    
     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&#39;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 and an activation ball. The tubular string is adapted to be deployed in the well, and the activation ball is adapted to be deployed in the tubular string to lodge in the seat. The activation ball includes an outer shell that forms a spherical surface. The outer shell forms an enclosed volume therein, and the outer shell is formed from a metallic material. 
     In another embodiment, a technique includes deploying an activation ball in a downhole tubular string in a well. The activation ball includes an outer shell that has an enclosed volume therein. The outer shell includes a metallic material. The technique includes communicating the ball through a passageway of the tubular string until the ball lodges in a seat of the string to form an obstruction (or fluid tight barrier), and the method includes using the obstruction to pressurize a region of the 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 and 3C  are cross-sectional views of an exemplary ball-activated tool of  FIG. 1  according to an embodiment of the invention. 
         FIG. 4  is a cross-sectional view of an activation ball in accordance with embodiments disclosed herein. 
         FIG. 5  is a cross-sectional view of an activation ball in accordance with embodiments disclosed herein. 
         FIG. 6  is a cross-sectional view of an activation ball in accordance with embodiments disclosed herein. 
         FIG. 7A  is a perspective view of an activation ball in accordance with embodiments disclosed herein. 
         FIGS. 7B-7D  are cross-sectional views of a portion of an activation ball in accordance with embodiments disclosed herein. 
         FIG. 7E  is a perspective view of a portion 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 a well  10  that is depicted in  FIG. 1 . For this example, the well  10  includes a wellbore  12  that extends through one or more reservoir formations. Although depicted in  FIG. 1  as being a main vertical wellbore, the wellbore  12  may be a deviated or horizontal wellbore, in accordance with other embodiments of the invention. 
     As depicted in  FIG. 1 , a tubular string  20  (a casing string, as a non-limiting example) extends into the wellbore  12  and includes packers  22 , which are radially expanded, or “set,” for purposes of forming corresponding annular seal(s) between the outer surface of the tubular string  20  and the wellbore wall. The packers  22 , when set form corresponding isolated zones  30  (zones  30   a ,  30   b  and  30   c  being depicted in  FIG. 1 , as non-limiting examples), in which may be performed various completion operations. In this manner, after the tubular string  20  is run into the wellbore  12  and the packers  22  are set, completion operations may be performed in one zone  30  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 given zone  30  for a completion operation, the tubular string  20  includes tools that are selectively operated using light weight activation balls  36 . As described herein, each activation ball  36  is constructed from an outer metallic shell and may be hollow, in accordance with some implementations. 
     For the particular non-limiting example that is depicted in  FIG. 1 , the downhole tools are sleeve valves  33 . In general, for this example, each sleeve valve  33  is associated with a given zone  30  and includes a sleeve  34  that is operated via a deployed activation ball  36  to selectively open the sleeve  34 . In this regard, in accordance with some embodiments of the invention, the sleeve valves  33  are all initially configured to be closed when installed in the well as part of the string  20 . Referring to  FIG. 3A  in conjunction with  FIG. 1 , when closed (as depicted in zones  30   b  and  30   c ), the sleeve  34  covers radial ports  32  (formed in a housing  35  of the sleeve valve  33 , which is concentric with the tubular string  30 ) to block fluid communication between a central passageway  21  of the tubular string  20  and the annulus of the associated zone  30 . Although not shown in these figures, the sleeve valve  33  has associated seals (o-rings, for example) for purposes of sealing off fluid communication through the radial ports  32 . 
     The sleeve valve  33  may be opened by deployment of a given activation ball  36 , as depicted in zone  30   a  of  FIG. 1 . Referring to  FIG. 3B  in conjunction with  FIG. 1 , in this regard, the activation ball  36  is deployed from the surface of the well and travels downhole (in the direction of arrow “A”) through the central passageway  21  to eventually lodge in a seat  38  of the sleeve  34 . Referring to  FIG. 3C  in conjunction with  FIG. 1 , when lodged in the seat  38 , 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 the sleeve  34  due to the pressure differential (i.e., a high pressure “P high ” above the ball  36  and a low pressure “P low ” below the ball  36 ) to cause the sleeve valve  33  to open and thereby allow fluid communication through the associated radial ports  32 . 
     Referring to  FIG. 1 , in accordance with an exemplary, non-limiting embodiment, the seats  38  of the sleeve valves  33  are graduated such that the inner diameters of the seats  38  become progressively smaller from the surface of the well toward the end, or toe, of the wellbore  12 . Due to the graduated openings, a series of varying diameter hollow activation balls  36  may be used to select and activate a given sleeve valve. In this manner, for the exemplary arrangement described herein, the smallest outer diameter activation ball  36  is first deployed into the central passageway  21  of the tubular string  20  for purposes of activating the lowest sleeve valve. For the example depicted in  FIG. 1 , the activation ball  36  that is used to activate the sleeve valve  33  for the zone  30   a  is thereby smaller than the corresponding hollow activation ball  36  (not shown) that is used to activate the sleeve valve  33  for the zone  30   b . In a corresponding manner, an activation ball  36  (not shown) that is of a yet larger outer diameter may be used activate the sleeve valve  33  for the zone  30   c , and so forth. 
     Although  FIG. 1  depicts a system of varying, fixed diameter seats  38 , 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 given activation ball  36  from its seat  38  may be used to relieve the pressure differential resulting from the obstruction of the passageway  37  (see  FIG. 3C ) through the sleeve valve  33 . A seated actuation ball  36  may be removed from the seat  38  in a number of different ways. As non-limiting examples, the activation ball  36  may be made of a drillable material so that activation ball  36  may be milled to allow fluid flow through the central passageway  21 . Alternatively, the valve seat  38 , the sleeve  34  or the activation ball  36  may be constructed from a deformable material, such that the activation ball  36  may be extruded through the seat  38  at a higher pressure, thereby opening the central passageway  21 . As yet another example, the flow of fluid through the central passageway  21  may be reversed so that the activation ball  36  may be pushed upwardly through the central passageway  21  toward the surface of the well. In this manner, a reverse circulation flow may be established between the central passageway  21  and the annulus to retrieve the ball  36  to the surface of the well. By reversing fluid flow to dislodge the activation ball  36 , the activation ball  36  is non-destructably removed from the well so that both the activation ball  36  and the corresponding sleeve valve may be reused. 
     When the activation ball  36  is retrieved by flowing fluid upwardly through the central passageway  21 , the activation ball  36  may have a particular specific gravity so that upwardly flowing fluid can remove the activation ball  36  from the seat  38 . While the specific gravity of the activation ball  36  may be a relatively important constraint, the activation ball  36  should be able to withstand the impact of seating in the seat  38 , the building of a pressure differential across the ball  36  and the higher temperatures present in the downhole environment. The failure of the activation ball  36  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 the activation ball  36  under impact loads, high pressure for high temperatures may conceivably prevent the activation ball  36  from properly sealing against the seat  38 , thereby preventing the effective buildup of a pressure differential. In other scenarios, the deformation of the activation ball  36  may cause the activation ball  36  to slide through the seat  38  and to become lodged in the sleeve  34 , such that it may be relatively challenging to remove the activation ball  36 . 
     In embodiments where activation ball  36  is designed to be retrieved by flowing fluid upwardly through the central passageway  21 , the activation ball  36  may have the following specific physical properties. Specifically, the activation ball  36  may have a particular specific gravity so that the upward flowing fluid can remove the activation ball  36  from the seat  38  and carry it upward through central passageway  21 . While the specific gravity of the activation ball  36  may be a relatively important constraint, the activation ball  36  may also be able to withstand the impact of seating in the downhole tool, the building of a pressure differential across the activation ball  36 , and the high temperatures of a downhole environment. Failure of the activation ball  36  to maintain its shape and structure during use may lead to failure of the downhole tool. For example, deformation of the activation ball  36  under impact loads, high pressures, or high temperatures may prevent activation ball  36  from properly sealing against seat  38 , thereby preventing the effective build up of a pressure differential. In other scenarios, deformation of the activation ball  36  may cause the activation ball  36  to slide through the seat  38  and to become lodged in the sleeve  34 , such that conventional means of removing activation ball  112  may be ineffective. 
     As disclosed herein, 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, the activation ball  36  is constructed out of a metallic shell and as such, may be a hollow ball or sphere, which permits the activation ball  36  to have desired strength properties while being light enough to allow removal of the ball  36  from the well. 
     Referring to  FIG. 2 , thus, in accordance with some embodiments of the invention, a technique  50  includes deploying (block  52 ) a shell-based activation ball, such as a hollow activation ball, into a tubular string in a well and allowing (block  54 ) the ball to lodge in a seat of the string. The technique  50  includes using (block  56 ) an obstruction created by the activation ball lodging in the seat to increase fluid pressure in the tubular string and using (block  58 ) the increased fluid pressure to activate a downhole tool. 
     Referring to  FIG. 4 , a cross-sectional view of a hollow activation ball  200  in accordance with embodiments disclosed herein is shown. Hollow activation ball  200  includes an outer shell  202  having an enclosed hollow volume  204 . Outer shell  202  may be formed from a first portion  206  and a second portion  208  which may be joined together using joining methods such as, for example, welding, friction stir welding, threading, adhering, pressure fitting, and/or mechanical fastening. As shown in  FIG. 4 , first and second portions  206 ,  208  of outer shell  202  are joined using a weld  210 ; however, those of ordinary skill in the art will appreciate that any known method of joining two parts may be used. 
     In certain embodiments, outer shell  202  may be formed from a metallic material. The metallic material may include a metallic alloy such as, for example, aluminum alloy and/or magnesium alloy. Aluminum alloys from the 6000 series and 7000 series may be used such as, for example, 6061 aluminum alloy or 7075 aluminum alloy. Although the specific gravity of most metallic materials is greater than 2.0, a hollow activation ball  200  in accordance with the present disclosure may have a specific gravity less than 2.0. Preferably, the specific gravity of hollow activation ball  200  in accordance with embodiments disclosed herein is between about 1.00 and about 1.85. 
     Referring to  FIG. 5 , a cross-section view of an activation ball  300  in accordance with embodiments disclosed herein is shown. Similar to hollow activation ball  200  ( FIG. 4 ), hollow activation ball  300  includes an outer shell  302  having an enclosed volume  304 . Outer shell  302  may be formed from a first portion  306  and a second portion  308 , joined together using threads  320 . One of ordinary skill in the art will appreciate that other joining or coupling methods may be used such as, for example, welding. Hollow activation ball  300  may further include a coating  322  disposed over an outer surface of outer shell  302 . Coating  322  may be 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, coating  322  may include Fluorolon® 610-E, available from Southwest Impreglon of Houston, Tex. 
     Coating  322  may be between 0.001 and 0.005 inches thick, and may be applied by dipping outer shell  302  in the coating material, by spraying the coating material onto outer shell  302 , by rolling outer shell  302  through the coating material, or by any other known coating application method. In certain embodiments, coating  322  may include a plating, an anodized layer, and/or a laser cladding. The coating material and the thickness of coating  322  may be selected such that activation ball  300  has an overall specific gravity between about 1.00 and about 1.85. Additionally, the coating material may be chosen to provide activation ball  300  with improved properties such as, for example, improved corrosion resistance and/or improved abrasion resistance. Specifically, the coating material may be selected to prevent a reaction between the metallic material of outer shell  302  and downhole fluids such as drilling mud or produced fluid. 
     Referring to  FIG. 6 , a cross-section view of an activation ball in accordance with embodiments disclosed herein is shown. Hollow activation ball  400  includes an outer shell  402  having an enclosed volume  404 . Outer shell  402  may include a first portion  406  and a second portion  408  joined using an interference fit  424 ; however, other joining methods such as welding, adhering, and threading may be used. Enclosed volume  404  may include a fill material  426  to provide additional support to shell  402  under high impact loads, pressures, and temperatures. In certain embodiments, fill material  426  may include at least one of a plastic, a thermoplastic, a foam, and a fiber reinforced phenolic. Fill material  426  may be selected such that the overall specific gravity of activation ball  400  is between about 1.00 and about 1.85. Although activation ball  400  is not shown including a coating, a coating may be added similar to coating  322  shown on activation ball  300  ( FIG. 5 ). 
     In other embodiments, hollow volume  404  may be filled with a gas such as, for example, nitrogen. The gas may be pressurized to provide support within outer shell  402  which may allow activation ball  400  to maintain its spherical shape under high impact loads, pressures, and temperatures. Hollow volume  404  may be filled with gas using an opening or port (not shown) disposed in outer shell  402 . After a desired amount of gas is pumped into hollow volume  404  and a desired internal pressure is reached, the port (not shown) may be sealed or capped to prevent gas from leaking out of activation ball  400 . 
     Referring to  FIG. 7A , a perspective view of a joined outer shell  502  including a first portion  506  and a second portion  508  in accordance with embodiments disclosed herein is shown. Referring now to  FIG. 7B , a side cross-sectional view of second portion  508  of outer shell  502  is shown. Only second portion  508  of outer shell  502  is shown for simplicity, and those of ordinary skill in the art will appreciate that the corresponding first portion  506  may be substantially the same as second portion  508 . 
     Outer shell  502  includes a hollow volume  504 , an inner surface  528 , and a support structure  530  disposed on the inner surface  528 . Support structure  530  may include a reinforcing ring  532  as shown which may be coupled to inner surface  528  of second portion  508  of outer shell  502 . Although only one reinforcing ring  532  is shown, those of ordinary skill in the art will appreciate that multiple reinforcing rings may be used having any desired thickness, t, and any desired maximum width, w. Additionally, although an inner face  534  of reinforcing ring  532  is shown parallel to a central axis  536  of second portion  508 , inner face  534  may alternatively be angled relative to central axis  536 , or may be arced to correspond with the curve of inner surface  528 . 
     Referring to  FIG. 7C , a side cross-sectional view of second portion  508  of outer shell  502  is shown having a second type of support structure  530  disposed therein. Ribs  538  are shown disposed on inner surface  528  of second portion  508 . Ribs  538  may take any shape or size, and may extend along inner surface  528  in any desired direction. As shown, ribs  538   a ,  538   b , and  538   c  intersect each other at junction  540 ; however, a plurality of ribs  538  may be positioned within second portion  508  such that no contact between ribs  538  occurs. 
     Referring to  FIG. 7D , a side cross-sectional view of second portion  508  of outer shell  502  is shown having a third type of support structure  530  disposed therein. Specifically, spindles  542  may be used to help support outer shell  502 , thereby maintaining the shape of outer shell  502  under high pressures, impact loads, and temperatures. In certain embodiments, a plurality of spindles  542  may extend radially outwardly from a center point  446  of an assembled activation ball  500 , and may contact inner surface  528  of second portion  508  at an intersection  544 . While specific examples of support structure configurations have been described, one of ordinary skill in the art will appreciate that other support structure configurations may be used without departing from the scope of embodiments disclosed herein. 
     Support structures  530  such as, for example, reinforcing rings  532 , ribs  538 , and spindles  542 , shown in  FIGS. 7B-7D , may be formed from a plastic, metal, ceramic, and/or composite material. Specifically, metal support structures may be formed from cast iron or low grade steel. In certain embodiments, support structures  530  may be formed integrally with first or second portions  506 ,  508  of outer shell  502 . Alternatively, support structures  530  may be formed separately and may be assembled within outer shell  502  using welding, brazing, adhering, mechanical fastening, and/or interference fitting. Those of ordinary skill in the art will appreciate that materials, designs, and dimensions of support structures  530  may be selected to provide increased strength to outer shell  502  while maintaining an overall specific gravity of activation ball  500  between about 1.00 and about 1.85. 
     Referring to  FIG. 7E , a perspective view of a first portion  506  of outer shell  502  of activation ball  500  is shown. Support structure  530  is shown disposed in hollow volume  504  of first portion  506 . The support structure  530  is an assembly of reinforcing rings  532 , ribs  538 , and a spindle  542 . Those of ordinary skill in the art will appreciate that various configurations of reinforcing rings  532 , ribs  538 , and spindles  542  may be used to create a support structure  530 . Additionally, although not specifically shown, a support structure  530  as discussed above may be used in combination with a fill material injected into enclosed volume  504 . 
     In certain embodiments, enclosed volume  504  may also be used to house equipment such as, for example, sensors. Sensors configured to measure pressure, temperature, and/or depth may be disposed within enclosed volume  504 . Data collected by the sensors may be stored in a storage device enclosed within volume  504 , or the data may be relayed to the surface of the wellbore. 
     Additionally, equipment such as, for example, receivers, transmitters, transceivers, and transponders, may be disposed within enclosed volume  504  and may send and/or receive signals to interact with downhole tools. For example, radio frequency identification (RFID) tags may be used as activation devices for triggering an electrical device in another downhole tool. For example, as the activation ball housing RFID tags passes through the wellbore, the RFID tags may activate a timer linked to the electrical device, which may lead to the performance of a desired task. In certain embodiments, a frac valve may be opened by initiating a corresponding timer using RFID tags and/or magnets housed within an activation ball. A magnet disposed within enclosed volume  504  may also be used to trigger and/or actuate downhole tools. 
     An activation ball in accordance with some embodiments may be manufactured by forming an outer shell out of a metallic material, wherein the outer shell includes an enclosed volume therein. In certain embodiments, the outer shell may be formed from a magnesium alloy, an aluminum alloy, a steel alloy, or nickel-cobalt base alloy. Specifically, an aluminum alloy may be selected from 6000 series aluminum alloys or 7000 series aluminum alloys, and a steel alloy may be selected from 4000 series steel alloys. In particular 4140 steel may be used. A nickel-cobalt base alloy such as, for example MP35N® may also be used. For ease of manufacturing, the outer shell may be made up of multiple portions joined together using, for example, welding, friction stir welding, brazing, adhering, threading, mechanical fastening, and/or pressure fitting. A wall thickness, tw, may vary depending on the material selected for outer shell  502 , so that an overall specific gravity of activation ball  500  between about 1.00 and about 1.85 may be achieved. An activation ball formed from high strength materials such as MP35N® or 4140 steel may have an overall specific gravity of about 1.2. The low specific gravity of an activation ball formed from MP35N or 4140 steel may greatly increase the likelihood of recovering the activation ball using reversed fluid flow through the center bore in which the activation ball is seated. 
     In some embodiments, manufacturing the activation ball may further include filling the enclosed volume within the outer shell with a fill material such as, for example, plastic, thermoplastic, polyether ether ketone, fiber reinforced phenolic, foam, liquid, or gas. The outer shell enclosed volume may be filled such that a pressure inside of the outer shell is greater than atmospheric pressure, thereby providing the activation ball with increased strength against impact loads and high pressures. 
     Alternatively, a rigid support structure may be provided within the enclosed volume of the outer shell. As discussed above, reinforcing rings, ribs, and spindles may be used separately or in combination to form the support structure. The support structure may be formed integrally with the outer shell by machining, casting, or sintering the outer shell. In another embodiment, the support structure may be formed as a separate component and may be later installed within the outer shell. In embodiments having a support structure fabricated separately from the outer shell, the support structure may be installed using welding, brazing, adhering, mechanical fastening, and/or pressure fitting. The support structure may be designed such that, when assembled within the activation ball, pressure applied by the support structure to the inner surface of the outer shell is greater than atmospheric pressure. 
     Advantageously, embodiments disclosed herein provide for an activation ball having increased strength under impact loads, high pressures, and high temperatures, while having an overall specific gravity between about 1.00 and about 1.85. Activation balls in accordance with the present disclosure may also have greater durability than activation balls formed from composite materials which degrade over time. Further, activation balls having a metal shell as disclosed herein may be more reliable due to the consistency of mechanical properties between different batches of metallic materials. Because of the consistency of mechanical properties of metallic materials, and because of their high strength, activation balls in accordance with the present invention 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 in the embodiments above, approximately twelve fracturing valves (such as the sleeve valves  33 ) may be used during a multi-stage fracturing process, whereas approximately eight fracturing valves may be used with traditional activation balls. 
     While the present invention has been described with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention