Abstract:
Apparatus and method are provided for diverting treatment fluids in wells. Sliding sleeves or valves are sequentially opened by dropping balls that may be of uniform size. Opening of one valve moves a collet into position such that the same size ball can be used to open a second valve. Any selected number of valves can be opened with the same size balls. Systems using the valves are also disclosed, along with methods for operating.

Description:
BACKGROUND OF INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention pertains to a system for injecting treatment fluids into a selected isolated interval in an oil and gas well. More particularly, valves disposed along a tubular are opened sequentially by pumping balls of one size down the tubular, causing one valve to open and another valve mechanism to be moved into position to be opened by a following ball. 
         [0003]    2. Description of Related Art 
         [0004]    Treatment fluids, such as hydraulic fracturing or acidizing fluids, are often used to treat multiple zones or segments of the earth penetrated by a wellbore. It is usually preferable to treat each zone or segment individually and to divert the treating fluid to another zone or segment when a designed amount of treating fluid has been injected into a zone or segment. In vertical wells, different zones of a producing formation are normally treated individually. In the horizontal wellbore portion of “horizontal wells,” different segments of the horizontal wellbore are often treated individually. This treatment may be a hydraulic fracturing treatment. It is common to isolate segments of horizontal wellbores by packers, either on casing in open hole or on tubing in a cased and perforated well. Packers are provided to isolate the zone to be treated so that fluid under pressure will be directed outwardly of the well and confined within a given zone or segment. In a horizontal well in shale gas reservoirs, it has become common to isolate the horizontal wellbore into ten or more segments and fracture each segment independently. The goal is to create multiple hydraulic fractures transverse to the wellbore, which are critical to producing gas from the well at economic rates. 
         [0005]    A common method for opening valves disposed along a casing or tubing in a well is the use of sliding sleeves, which may be opened by a tool run into the well. Another method is to place a ball in the injected fluid at a time when it will seat on a receiving apparatus connected to a sliding sleeve when it is desired to open the sliding sleeve. Fluid pressure behind the ball opens the sleeve or valve. To open a plurality of valves, it is necessary to use different size balls, starting with the smallest ball to seat on the lowest sleeve apparatus, which will pass through the larger seats. Balls of increasing size are injected to divert fluid to another zone or segment. The use of such apparatus and method is described in the article “Considered approach improves hydraulic fracturing in horizontal open holes,” E&amp;P Magazine, Jul. 1, 2009. This article discusses some of the limitations of the present method. The use of sequentially smaller ball seats on sleeves within the well results in a limited number of unique seats for a given tubing size and in a limited number of unique zones for a fracture project. Drastically reduced internal seat diameters are required as the distance from the well head to the fracturing zone increases. This results in reduced production from the lower zones and frequently requires post-fracturing drilling operations to remove the seats. 
         [0006]    This approach is also described in U.S. Pat. No. 7,387,165. This requires a complicated ball launching system for balls of varying diameter and opens up the possibility of mis-ordering the balls, which would then unintentionally block off a given zone. 
         [0007]    What is needed is apparatus and method for diverting treating fluids in a wellbore that does not require balls of varying size, such that any selected number of zones or intervals in a well can be treated. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    The invention as disclosed includes a well treating system that may include a lower initiation tool and a plurality of intermediate diverter valves that are positioned in zones or segments that are isolated by packers. Each diverter valve includes a sliding valve member that is axially moved as a result of a spherical ball being captured by a collet within the valve. All the balls are of the same diameter. Opening of the lowermost valve results in the next uphole valve being placed in a set position so that after the fracturing process is completed in the adjacent downhole fracturing zone, the valve is ready to be actuated by directing a subsequent ball down the well bore. 
         [0009]    The invention overcomes many of the above noted deficiencies with the prior art. A single size ball is employed which allows for a larger diameter production tube to be employed. This increases production compared to the prior art which requires sequentially smaller diameter balls and tubing. Since all the balls are of the same size, the possibility of mis-ordering the balls is eliminated and consequently accidental isolation of fracturing zones is eliminated, as is the requirement for post-fracturing drilling operations to remove the ball seats. Also, since the balls are of a uniform size and there is no need to reduce the diameter of the ball seats, an unlimited number of fracturing zones or intervals can be isolated and treated for a given well. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0010]      FIG. 1  is an overall view of the fracturing system according to an embodiment of the invention. 
           [0011]      FIG. 2  is a cross sectional view of the lower initiation tool in the closed position within the well. 
           [0012]      FIG. 3  is a cross sectional view of the lower initiation tool in the open position within the well. 
           [0013]      FIG. 4  is a cross sectional view of the lower portion of a diverter valve in the closed position within the well. 
           [0014]      FIG. 5  is a cross sectional view of the upper portion of a diverter valve in the closed position within the well. 
           [0015]      FIG. 6  is a cross-sectional view of the lower portion of the diverter valve in the open position within the well. 
           [0016]      FIG. 7  is a cross-sectional view of the upper portion of the diverter valve in the open position within the well. 
           [0017]      FIG. 8  is a cross-sectional view of the lower portion of the diverter valve in the set position within the well. 
           [0018]      FIG. 9  is a cross-sectional view of the upper portion of the diverter valve in the set, and closed position within the well. 
           [0019]      FIG. 10  is a cross-sectional view of the lower portion of the diverter valve in the reset condition within the well. 
           [0020]      FIG. 11  is a cross-sectional view of the upper portion of the diverter valve in the reset, and opened position within the well. 
       
    
    
       [0021]    The drawings provided herein are meant to illustrate the principles of the invention in general terms and are not intended to limit the invention to the specific details shown the drawings. Other shapes and sizes for the various structural members could be used without departing from the invention, which is set forth in the accompanying claims. Also the drawings are not necessarily drawn to scale. The drawings depict the invention in a vertical direction, but it should be understood that the apparatus can be used in vertical or horizontal wells or wells at any angle. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0022]      FIG. 1  illustrates an embodiment of the system deployed within a well bore  1 . The system includes tubing  2 , packers  3 , a plurality of diverter valves  35 , and lower initiation tool  6 . Lower initiation tool  6  and diverter valves  35  are positioned within zones  5  using suitable tubing  2 . Zones to be treated (called “fracturing zones” herein)  5  are isolated by positioning known packers  3  above and below the diverter valves and the lower initiation tool. Fracturing zones  5  are illustrated as separated by non-productive segments in the figure, which would apply in a vertical well or wellbore at an angle that penetrates both productive and non-productive zones. In a horizontal portion of a well, the non-productive zones may not be present. 
         [0023]    Referring to  FIG. 2 , the lower initiation tool  6  includes a housing  4 , which at its lower end  24  is adapted for connection to tubing  15  by any suitable means such as screw threads. The upper portion of the housing  23  is similarly adapted for attachment to the lower end  22  of tubing  2 . Packers  3  are positioned above and below the tool  6  on the tubing. Housing  4  including a plurality of radially spaced outlets  9  for the fracturing fluid. Housing  4  is also provided with a fluid passageway  17  to which a jumper conduit  16  is attached. A plurality of shear pins  11  are positioned within bores provided in the housing  4 . Mounted for axial movement within the housing  4  is a hollow cylindrical valve sleeve  7 . The upper end valve sleeve  7  includes a radial groove  25 . A pair of O-rings  18  and  19  is located on a raised shoulder portion  71 . A second raised shoulder portion  72  at the top of the valve sleeve cooperates with the raised shoulder portion  71  to form an annular chamber  21 . A third raised shoulder portion  73  is provided on the valve sleeve at its intermediate portion. A plurality of ports  8  are located in valve sleeve  7  between shoulders  71  and  73 . Valve sleeve  7  carries a snap ring  13  that is adapted to expand into snap ring recess  14  provided in the interior surface of the housing  4 . Shear pins  11  extend into blind bores provided on the outer surface of valve sleeve  7 . Valve sleeve  7  is also provided with a beveled interior surface  10  that is adapted to seat one of the balls  30 . 
         [0024]    To begin the fracturing process for the first fracturing zone a ball is initially placed or dropped down through tubing  2  and rests upon ball seat  10 . The fracturing fluid under pressure will exert a downward force on the ball and cause valve sleeve  7  to move axially after shearing the pins  11 . As shown in  FIG. 3 , this motion brings valve sleeve ports  8  into alignment with outlets  9 , thus allowing the fracturing fluid to escape under pressure into the first fracturing zone. Further movement of the valve sleeve  7  is prevented by a shoulder  74  on the valve sleeve  7  abutting a shoulder  75  provided within valve body  4  as shown in  FIG. 2 . At this point snap ring  13  expands into snap ring recess  14 . Movement of the valve sleeve  7  also brings fluid passageway  17  into fluid communication with annular chamber  21 . Annular chamber  21  is vented to the well bore via outlet passage  81  provided in the valve housing  4 . 
         [0025]    Details of a diverter valve  35  will now be discussed with reference to  FIGS. 4 and 5 . Diverter valve  35  has a valve housing  40  which at its lower end is provided with a coupling  41  adapted for connection with an upper portion  42  of a tubing. The coupling may be a conventional screw thread coupling as is known in the art. 
         [0026]    A collet  43  is located within the valve housing  40  and is axially movable within the housing. At its lower end the collet is provided with a plurality of collet fingers  44 . A hydraulic logic piston  46  is attached to an intermediate portion of collet  43  by a plurality of shear pins  49 . An annular chamber  45  is formed between the logic piston  46  and an interior wall portion of the valve housing  40 . A passageway  92  communicates with jumper conduit  16  and chamber  45 . The upper surface area  93  of hydraulic logic piston  46  is greater than that of its lower portion  94  so that fluid pressure within the diverter valve urges the logic piston  46  and consequently the collet in a downward direction as viewed in  FIG. 4 . However downward motion of the logic piston  46  is prevented by the pressure of fluid within chamber  45  until chamber  45  is vented to the outside of the valve housing via passageway  92 , jumper conduit  16 , chamber  21  and vent port  81 . This occurs when valve sleeve  7  of the lower initiation tool moves to an open position as shown in  FIG. 3 . 
         [0027]    The upper portion of a diverter valve  35  is shown in  FIG. 5 . The upper portion  60  of valve housing  40  is adapted to be connected to tubing at  61  using conventional coupling devices such as screw threads. The upper portion of the housing includes a fluid passageway  59  which is connected to a further jumper conduit  58 . A vent passage  95  extends from the interior portion to the exterior portion of the diverter valve housing. A valve sleeve  52  is located within a bore in the diverter valve housing for axial movement. A chamber  86  is formed between the outer surface of the valve sleeve  52  and the valve housing. A plurality of valve sleeve ports  55  are formed in the valve sleeve  52  between raised shoulder portions  96  and  97 . Valve housing  40  includes a plurality of outlets  54  that allow fracturing fluid to enter the fracturing zone when sleeve  52  moves to the position shown in  FIG. 7 . Shear pins  53  extend through bores in the valve housing  40  and extend into blind bores on the outer surface of sleeve  52 . The lower portion of sleeve  52  is provided with a snap ring  56  which is adapted to expand into snap ring recess  57  located in the valve housing. The lower end of the sleeve  52  and the upper end  99  of collet  43  are slidably connected by a connector sleeve  51  which has internal upper and lower shoulder portions  101  and  102  that engage shoulder portions provided on the exterior of sleeve  52  at  103  and collet  43  at  104  as shown in  FIG. 5 . 
         [0028]    As mentioned above, when the lower initiation tool is in the open position shown in  FIG. 3 , the hydraulic fluid in chamber  45  is vented thus allowing hydraulic logic piston  46  to move downwardly. Collet  43  moves downwardly as illustrated in  FIG. 4  with the logic piston  46  which causes the flexible fingers  44  at the end of the collet to be camed inwardly by a first beveled surface  91  to a position shown in  FIG. 8  which is the set condition. At this point the shoulder  103  on sleeve  52  comes into proximity with shoulder portion  101  of the connector sleeve. Further downward movement of the collet will move sleeve  52  downwardly as depicted in  FIG. 7  to a point where ports  55  are in alignment with outlets  54 , as discussed below. As discussed above, the flexible fingers  44  are axially movable to vary the internal diameter of the flow-through fluid passageway and thereby capture the next ball as it is introduced into the tubular string. It is understood that other mechanisms may be utilized to vary the diameter of the flow-through fluid passageway in response to axial movement of a cylindrical member. Such mechanisms may include for example, radially collapsible lugs, a deformable conical member or an iris arrangement. 
         [0029]    When the fracturing process is completed in the first fracturing zone, another ball  30  is introduced into the tubing. The ball is captured by the flexible fingers  44  of the collet which is in the set position as shown in  FIG. 8 . This increases the pressure within the valve housing to a point at which shear pins  49  are sheared. Collet  43  continues to travel in a downward direction until the fingers hit a second beveled surface  111  provided in the valve housing. This additional movement shears pins  53  and via connector sleeve  51  drags the valve sleeve to the position shown in  FIG. 7  which allows fracturing fluid to escape via valve sleeve ports  55  and outlets  54  into the next fracturing zone. This movement also sets the diverter valve above to a set position by virtue of venting the pressure in the housing via vent passage  95 , passageway  59 , and jumper conduit  58 , and the fracturing process can be repeated for multiple zones. 
         [0030]    When the fracturing process is completed, flow of the fracturing fluid is stopped and the pressure acting on the balls is eliminated. At this point all of the balls can be flowed back out of the well. All of the collets are returned to their original position by springs  48  and full flow through the tubular can now occur. The diverter valves are now in the reset made as shown in  FIGS. 9 and 10 . 
         [0031]    The operation of the fracturing system is as follows. The lower initiation tool and all of the diverter valves are positioned in the well in a closed mode. The first ball is dropped down to the lower initiation tool, and comes to rest on shoulder  10 . At this point the pressure of the fracturing fluid will cause valve sleeve  7  to shift downwardly bringing valve sleeve ports  8  into alignment with outlets  9 . Shear pins  11  are severed and snap ring  13  moves into snap ring groove  14 . Packers  3  isolate the fracturing zone so that fracturing fluid is confined under pressure within the fracturing zone. Movement of the valve sleeve  7  also opens up vent port  81  which relieves pressure within chamber  45  in the adjacent diverter valve so that hydraulic logic piston  46  in the diverter valve can move under pressure to its lower position which in turn moves collet  43 . Collet fingers  44  are thereby compressed inwardly by surface  91  to the set position shown in  FIG. 8 . Spring  48  is also partially compressed. 
         [0032]    When fracturing of the first zone is completed, the next ball is launched and is captured by the compressed collet fingers in the diverter valve above the first zone. The fracturing fluid pressure now causes collet  43  to move to the open position in  FIG. 6 , severing shear pins  49  in the hydraulic logic sleeve and shear pins  53  in the valve sleeve  52 . Main spring  48  is now fully compressed and snap ring  56  moves into snap ring recess  57  in the diverter valve. Once again, movement of the upper portion of the diverter valve sleeve relieves the pressure within the chamber  45  of the next diverter valve located in the next zone to be fractured so that the next diverter valve is now placed in the set mode as shown in  FIG. 8 . When fracturing of the second zone is completed, another ball is dropped thereby actuating the next diverter valve sleeve so that fracturing fluid is directed into the third fracturing zone via outlets  54  and  55 . 
         [0033]    This process can be continued indefinitely with the same size balls. Once all fracturing operations are complete, all of the balls can be flowed back out of the well. When fracturing fluid flow and pressure are removed, the collets in all of the diverter valves are returned to their original position by springs  48 . They are now reset as shown in  FIG. 10  to allow production fluid to flow upwardly through the tubing with full bore flow. 
         [0034]    Various modifications may be made without departing from the invention as disclosed. For example, the lower initiation tool may be replaced by a diverter valve with the collet pinned in the set position. Other modifications will be apparent to those with ordinary skill in the art.