Unlimited Downhole Fracture Zone System

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

1. Field of the Invention

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.

2. Description of Related Art

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.

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&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.

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.

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

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.

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)

FIG. 1 is an overall view of the fracturing system according to an embodiment of the invention.

FIG. 2 is a cross sectional view of the lower initiation tool in the closed position within the well.

FIG. 3 is a cross sectional view of the lower initiation tool in the open position within the well.

FIG. 4 is a cross sectional view of the lower portion of a diverter valve in the closed position within the well.

FIG. 5 is a cross sectional view of the upper portion of a diverter valve in the closed position within the well.

FIG. 6 is a cross-sectional view of the lower portion of the diverter valve in the open position within the well.

FIG. 7 is a cross-sectional view of the upper portion of the diverter valve in the open position within the well.

FIG. 8 is a cross-sectional view of the lower portion of the diverter valve in the set position within the well.

FIG. 9 is a cross-sectional view of the upper portion of the diverter valve in the set, and closed position within the well.

FIG. 10 is a cross-sectional view of the lower portion of the diverter valve in the reset condition within the well.

FIG. 11 is a cross-sectional view of the upper portion of the diverter valve in the reset, and opened position within the well.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Claims

1. A diverter valve for releasing fluid from a tubular string located within a well to a selected zone or segments of formations to be treated comprising:

a housing having upper and lower connections and having a flow-through fluid passageway;

a collet having a plurality of flexible fingers positioned within the flow-through fluid passageway and axially moveable therein;

at least one outlet formed in the periphery of the housing;

a valve sleeve positioned within the flow-through fluid passageway and axially moveable therein, said valve sleeve having at least one outlet port; and

a connector sleeve slidably receiving an upper end of the collet and a lower end of the valve sleeve.

2. The valve of claim 1 further including:

a chamber positioned between the housing and collet;

a hydraulic logic piston slidably mounted on the collet in the chamber; and

an outlet passageway between the chamber and the exterior surface of the housing.

3. The valve of claim 1 wherein the flow through fluid passageway includes a first beveled surface and a second beveled surface downstream of the first beveled surface.

4. The valve as claimed in claim 2 wherein the hydraulic logic piston is connected to the collet by shear pins.

5. The diverter valve of claim 1 further including a spring in the housing resisting axial movement of the collet and valve sleeve.

6. The diverter valve of claim 3 further including an annular chamber located between an upper portion of the valve sleeve and the valve body and an outlet vent communicating with the annular chamber.

7. The diverter valve of claim 1 further including first and second shoulders located on the valve sleeve and a plurality of ports in the circumference of the valve sleeve between the first and second shoulders.

8. The diverter valve of claim 1 further including a plurality of shear pins extending between the collet and valve sleeve, a snap ring carried by the valve sleeve and a snap ring recess in the flow through passageway of the valve body.

9. The diverter sleeve of claim 1 wherein the connector sleeve is of the lost motion type whereby one of the valve sleeve and collet can move axially with respect to each other.

10. Apparatus for fracturing a plurality of selected zones or segments of formations extending outwardly from an oil or gas well comprising:

a tubular string;

at least one packer mounted on the tubular string; and

a plurality of diverter valves according to claim 1 connected in the tubular string.

11. Apparatus according to claim 10 further including a plurality of balls of similar diameter.

12. A lower initiation tool for use in apparatus for hydraulic fracturing comprising:

a valve housing having upper and lower connection portions for connecting the tool to a tubular;

a flow-through fluid passageway;

a valve sleeve positioned within the flow-through passageway having at least one side outlet port and a ball valve seat;

at least one outlet provided on the wall of the housing adapted to align with the outlet port in the valve sleeve when the valve sleeve moves a selected distance within the valve housing;

an annular chamber formed between the valve sleeve and the valve housing; and

a fluid passageway in the valve housing connectable to a jumper conduit at one end and extending to an interior surface of the flow through passageway.

13. A lower initiation tool according to claim 12 further including shear pins extending between the valve housing and valve sleeve,

a snap ring carried by the valve sleeve, and

a snap ring recess on an interior surface of the valve housing.

14. A method for treating selected zones or segments of formations extending outwardly from an oil or gas well comprising:

positioning a tubular string within a bore of the well, said tubular string comprising tubulars, at least one packer on the tubulars, and a plurality diverter valves according to claim 1,

initiating a flow of treating fluid within the tubular string;

diverting the treating fluid flow at the last diverter valve to the zone or segment to be treated by dropping a ball of a selected size into the tubular string;

causing the next upstream diverter valve to be placed in a set position; and

dropping a second ball of the same diameter into the tubular string to terminate treating of the first zone or segment and simultaneously diverting treating fluid from the next diverter valve into the next zone or segment to be treated.

15. The method according to claim 14 further including terminating the flow of treating fluid and recovering the balls from the tubular string.

16. A method of treating selected zones or segments of formations extending outwardly from an oil or gas well comprising:

isolating a plurality of zones or segments;

directing treating fluid into the well;

injecting treating fluid into a first one of the zones or segments to be treated;

terminating the flow of treating fluid to the first one of the zones or segments and concurrently diverting the flow of treating fluid into a second zone or segment to be treated by introducing a ball of a selected size; and

terminating the flow of treating fluid to the second zone or segment while concurrently diverting the flow of treating fluid to a third zone or segment by introducing a second ball of the same size as the first ball into the tubular string.

17. A diverter valve for releasing fluid from a tubular string located within a well to a selected zone or segments of formations to be treated comprising:

a housing having upper and lower connections and having a flow-through fluid passageway;

the flow-through fluid passageway having a variable size diameter portion;

at least one outlet formed in the periphery of the housing; and

a valve sleeve positioned within the flow-through fluid passageway and axially moveable therein in response to a change in diameter of the flow-through fluid passageway, said valve sleeve having at least one outlet port.

18. A diverter valve according to claim 17 wherein the variable size diameter portion of the flow-through fluid passageway comprises a collet having a plurality of flexible fingers at one end thereof and axially movable within the flow-through fluid passageway.

19. A diverter valve as claimed in claim 18 and further comprising a connector sleeve slidably receiving an upper end of the collet and a lower end of the valve sleeve.

20. A diverter valve as claimed in claim 18 wherein the flow-through fluid passageway includes first and second frustoconical portions, a downstream portion of the second frustoconical portion being of less diameter than a downstream portion of the first frustoconical portion.