US20110155392A1

US20110155392A1 - Hydrostatic Flapper Stimulation Valve and Method

Info

Publication number: US20110155392A1
Application number: US12/732,345
Authority: US
Inventors: W. Lynn Frazier
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-12-30
Filing date: 2010-03-26
Publication date: 2011-06-30

Abstract

A downhole tool including a tubular housing, a sleeve, a flapper valve, and a pressurized chamber. The tubular housing has an inner bore. The sleeve is disposed in the inner bore and configured to slide between a first position and a second position. The flapper valve is pivotally coupled to the tubular housing, maintained in an inoperative position when the sleeve is in the first position, and pivotable between an open position and a closed position when the sleeve is in the second position. The pressurized chamber is in fluid communication with the sleeve, wherein, upon activation of the downhole tool, a hydrostatic pressure is applied on the sleeve via the pressurized chamber, such that the sleeve slides from the first position to the second position.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application having Ser. No. 61/291,216, filed on Dec. 30, 2009, which is incorporated by reference herein.

BACKGROUND

1. Field of the Invention
Embodiments of the present invention generally relate to isolation valves in wellbore completions. More particularly, embodiments of the present invention relate to flapper valves for isolating one casing region from another.
2. Description of the Related Art
Fracturing techniques in wellbores have been used to extract fluids, such as hydrocarbons like natural gas, from wellbores that would otherwise be unproductive. In situations where multiple hydrocarbon-bearing zones are encountered in vertical wells, horizontal wells, or in deviated wells, the multiple zones can be fractured one after another. This can be accomplished by perforating and then fracturing a distal zone and placing a bridge plug in the casing immediately above the fractured distal zone. This can isolate the fractured distal zone, allowing an adjacent proximal zone to be perforated and fractured. This process can be repeated until all of the desired zones have been fractured.
Once all the desired zones have been fractured, the bridge plugs between adjacent zones can be destroyed or opened to allow fluids from the fractured zones to flow in a commingled stream up the tube string to the surface. To accomplish this, the plugs can be broken apart or drilled out to allow the flow of fluid; however, this can leave fouling debris in the tube string and can present difficulties especially in deviated wells. Some plugs can instead be dissolved using activating agents, but this can limit the fluids that can be used with the downhole tool or present challenges if other dissolvable elements are used in the wellbore that are not intended to dissolve at the same time as the plug. The plugs can also be check valves, such as flapper valves, but the check valves need to be maintained in the open position during deployment down the well and thus require manipulation to allow them to operate at the desired time. This manipulation can require expensive equipment and can delay the sequential fracturing process. What is needed is a bridge plug that can effectively isolate the multiple zones, which can be deployed and removed without suffering from the drawbacks described above or others.

SUMMARY

Embodiments of the disclosure can provide an illustrative downhole tool, which can include a tubular housing, a sleeve, a flapper valve, and a pressurized chamber. The tubular housing can have an inner bore. The sleeve can be disposed in the inner bore and can be configured to slide between a first position and a second position. The flapper valve can be pivotally coupled to the tubular housing, maintained in an inoperative position when the sleeve is, for example, in the first position, and pivotable between an open position and a closed position when the sleeve is, for example, in the second position. The pressurized chamber can be in fluid communication with the sleeve, wherein, upon activation of the downhole tool, a hydrostatic pressure can be applied on the sleeve via the pressurized chamber such that the sleeve can slide from the first position to the second position.
Embodiments of the disclosure can also provide an illustrative method of plugging a casing string with a flapper valve assembly. The method can include storing a flapper valve in a stowed position with a sleeve, and biasing the flapper valve toward a valve seat. The method can also include longitudinally moving the sleeve by applying a hydrostatic pressure differential across the sleeve to release the flapper valve from the stowed position, and selectively blocking a flow of fluid through the casing string with the flapper valve.
Embodiments of the disclosure can further provide an illustrative flapper valve assembly, which can include a tubular housing, a sleeve, a flapper valve, and a pressurized chamber. The tubular housing can be connectable to a wellbore casing string and can have a storage cavity defined therein. The sleeve can be slidable between a first position and a second position, wherein the sleeve in the first position can cover the storage cavity and the sleeve in the second position can at least partially uncover the storage cavity. The flapper valve can be disposed in the tubular housing and can be pivotally connected thereto. The flapper valve can be contained in the storage cavity, for example, when the sleeve is in the first position, and the flapper valve can be pivotable between an open position and a closed position, for example, when the sleeve is in the second position. The pressurized chamber can be configured to create a pressure differential across at least a portion of the sleeve such that the sleeve can move longitudinally from the first position to the second position.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

FIG. 1 depicts a cross-sectional view of an illustrative flapper valve assembly, showing an illustrative flapper valve in a stowed position, according to one or more embodiments described.

FIG. 2 depicts a view similar to FIG. 1, showing the illustrative flapper valve blocking a downward flow of fluid into a well, according to one or more embodiments described.

FIG. 3 depicts a cross-sectional view of another illustrative flapper valve assembly, according to one or more embodiments described.

FIG. 4 depicts a cross-sectional view of yet another illustrative flapper valve assembly, according to one or more embodiments described.

DETAILED DESCRIPTION

A detailed description will now be provided. Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims. Each of the inventions will now be described in greater detail below, including specific embodiments, versions and examples, but the inventions are not limited to these embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the inventions, when the information in this disclosure is combined with available information and technology.
The terms “up” and “down”; “upward” and “downward”; “upper” and “lower”; “upwardly” and “downwardly”; “above” and “below”; and other like terms as used herein refer to relative positions to one another and are not intended to denote a particular spatial orientation since the apparatus and methods of using the same can be equally effective in either horizontal or vertical wellbore uses.
FIGS. 1 and 2 depict an illustrative flapper valve assembly 30 that can connect to a casing string as part of a wellbore completion (not shown), according to one or more embodiments. The flapper valve assembly 30 can have a flapper valve 67, a sleeve 70, and a pressurized chamber 71. The sleeve 70 can be slidable between a first position, shown in FIG. 1, and a second position, shown in FIG. 2. In the first position, the sleeve 70 can store the flapper valve 67 in an inoperative state or position, which can also be referred to herein as a stowed position. The flapper valve 67 can be maintained in the inoperative position, for example, during deployment of the casing string to which the flapper valve assembly 30 can be attached. In the second position, the sleeve 30 can release the flapper valve 67 into an operative state, allowing the flapper valve 67 to block a flow of fluid in at least one direction. The pressurized chamber 71 can enable the movement of the sleeve 70 by hydrostatic force, without requiring mechanical manipulation of the sleeve 70.
The flapper valve assembly 30 can also include a tubular housing 68, which can have an inner bore 69 and a lower sub 72. The lower sub 72 can have a threaded lower end 74 that can match the threads of any pipe joints or collars that can be included in a wellbore completion along with the flapper valve assembly 30. The tubular housing 68 can also have a central sub 76 coupled to the lower sub 72 and to an upper sub 80, for example, using threaded connections. In one or more embodiments, the upper sub 80 can be threaded onto the central sub 76 using a connecting member 79 and can provide a threaded end 84 that can attach to the casing string (not shown). The upper sub 80 can also include a smooth-walled portion 86 of the inner bore 69. The sleeve 70 can include a piston 90 connected thereto or integrally-formed therewith. The piston 90 can include one or more o-rings and/or other sealing devices to create slidable and sealing engagement between the piston 90 and the smooth-walled portion 86 of the tubular housing 68.
In one or more embodiments, the flapper valve 67 can be pivotally coupled to the lower sub 72 with a biasing member 109. In one or more embodiments, the flapper valve 67 can be biased toward the closed position by the biasing member 109. The biasing member 109 can include a pivot pin-and-spring assembly, or in other embodiments, can include any biasing structure or configuration. The biasing member 109 can bias the flapper valve 67 toward the lower sub 72 (counterclockwise, as shown), specifically, toward a valve seat 120 defined in the lower sub 72. While the sleeve 70 remains in the first position, however, the flapper valve 67 can be maintained inoperative in the stowed position.
The sleeve 70 can include a lower section 102 that can have a smaller external diameter than the tubular housing 68 and can thereby provide a storage cavity 88 for the flapper valve 67 radially between the sleeve 70 and the tubular housing 68. In the first position, a lower end of the sleeve 70 can engage the lower sub 72, as shown in FIG. 1, and can thereby seal against the lower sub 72 so that any materials proceeding through the inner bore 69 can be prevented from entering the storage cavity 88 and interfering with operation of the flapper valve 67.
The pressurized chamber 71 can be disposed in the upper sub 80 or, in other embodiments, can be disposed radially outside of the upper sub 80 (not shown). The pressurized chamber 71 can contain a gas at a reduced pressure in relation to the pressure in the flapper valve assembly 30 below the flapper valve 67. For example, the pressurized chamber 71 can include air at or near surface pressure, which can be encased therein. In one or more embodiments, the pressurized chamber 71 can be enclosed or self-contained. In one or more embodiments, the pressurized chamber 71 can communicate with the surface (not shown) when deployed down a wellbore (not shown) such that the surface can be the source of the reduced pressure gas contained in the pressurized chamber 71. In one or more embodiments, the pressurized chamber 71 can be located below the flapper valve 67 in the lower sub 72.
The pressurized chamber 71 can be in communication with a piston chamber 73 via a line 75, which can be formed in the upper and central subs 80, 76, with the line 75 extending past the connecting member 79, for example. The piston chamber 73 can be defined between the lower sub 72 and the piston 90, adjacent a side of the piston 90, as shown. In one or more embodiments, when the sleeve 70 is in the first position, the piston 90 can engage the lower sub 72 such that the piston chamber 73 can have little or substantially no volume. A second chamber 77 can be formed, for example, above the piston 90 and adjacent an opposite side of the piston 90, i.e., across the piston 90 from the piston chamber 73. The second chamber 77 can be separated and/or isolated from the inner bore 69 by the sleeve 70 such that, in one or more embodiments, the second chamber 77 can be prevented from communicating with the inner bore 69 and the piston chamber 73. In one or more embodiments, the second chamber 77 can initially be held at substantially the same pressure as the piston chamber 73 such that there can be substantially no pressure differential across the piston 90, for example.
The flapper valve assembly 30 can be activated to block a flow of fluid through the inner bore 69. Upon activation, the sleeve 70 can be drawn upward to the second position shown in FIG. 2 from the first position shown in FIG. 1, for example, thereby releasing the flapper valve 67 to the operative state. To draw the sleeve 70 upward, a vented section 110 of the tubular housing 68 can be created after the flapper valve assembly 30 has been positioned at a desired location, for example. In various embodiments, the vented section 110 can be created by any suitable perforating operation, including but not limited to: mechanical puncture, sand jetted puncture, ballistics such as shaped charges, by hydraulically or otherwise applying pressure to a frangible material such that the frangible material breaks apart, and/or by dissolving a dissolvable material. In various other embodiments, any other suitable method of perforating the tubular housing 68 and/or otherwise creating the vented section 110 can be used. Furthermore, the vented section 110 can extend partially through the tubular housing 68 to the extent necessary to put the pressurized chamber 71 in communication with the inner bore 69. Although not shown, in one or more embodiments, the vented section 110 can extend completely through the tubular housing 68.
In one or more embodiments, the flapper valve 67 can be pivotally coupled to the lower sub 72 with a biasing member 109. In one or more embodiments, the flapper valve 67 can be biased toward the closed position by the biasing member 109 such that when the sleeve 70 slides to the second position, for example, the flapper valve 67 can be urged toward the valve seat 120 by the biasing member 109. The biasing member 109 can include a pivot pin-and-spring assembly, or in other embodiments, can include any biasing structure or configuration.
The second chamber 77 can be defined between the piston 90 and the upper sub 80 such that, for example, while the sleeve 70 moves toward the second position, the volume of the second chamber 77 can be progressively reduced. In the second position, the sleeve 70 can release the flapper valve 67, allowing the biasing force of the biasing member 109 to act thereon and urge the flapper valve 67 toward the valve seat 120, for example. Accordingly, in the operative state, the flapper valve 67 can move or pivot as shown by arrow 97 between a closed position and a range of open positions. In the closed position, the flapper valve 67 can sealingly engage the valve seat 120. Furthermore, the flapper valve 67 can be in the closed position when, for example, the force applied on the flapper valve 67 by the pressure from above plus the biasing force of the biasing member 109 is greater than the force applied on the flapper valve 67 from below.
In one or more embodiments, the flapper valve 67 can have a concave or saddle-shaped upper and/or lower face, such that, for example, a cross-section of the flapper valve 67 can be arcuate. The flapper valve 67 in the inoperative state can thus conform to the annular cross-section of the tubular housing 68 and/or the storage cavity 88. This can allow the flapper valve assembly 30 to avoid significantly obstructing or decreasing a flow path area of the casing string to which the flapper valve assembly 30 can be attached. In one or more embodiments, the sleeve 70 can have an inner diameter that can be substantially the same as a diameter of the inner bore 69 proximal the upper and/or lower subs 80, 72, as shown. Furthermore, the flapper valve 67 being saddle-shaped can aid in resisting the pressure applied thereon, e.g., from above.
The valve seat 120 can also be concave or inversely saddle-shaped, so as to mate with the flapper valve 67 and create a sealing engagement therewith. Additionally, the flapper valve 67 can be made of a frangible material and can be movably fixed to the tubular housing 68 in any suitable manner. In one or more embodiments, the flapper valve 67 can be similar to or the same as the flapper valve described in U.S. patent application Ser. No. 12/130,840, the entirety of which is incorporated by reference herein to the extent it is not inconsistent with this disclosure.
With the sleeve 70 in the second position, the flapper valve 67 can be located at any of a range of open positions between the valve seat 120 and the tubular housing 68 (e.g., pivoted, shown clockwise, from the valve seat 120 toward the tubular housing 68), and can thereby allow a flow of fluid upward through the flapper valve assembly 30. The flapper valve 67 can be in the open position when the pressure from below applies a force on the flapper valve 67 greater than the force applied by pressure from above plus the biasing force, for example. Further, the flapper valve 67 can move or pivot between a range of open positions, as shown by the arrow 97, depending, for example, on the magnitude of the pressure differential across the flapper valve 67. Thus, a greater pressure from below can open the flapper valve 67 to a greater extent, for example.
In at least one embodiment, the flapper valve assembly 30 can be activated to release the flapper valve 67 from the stowed position. To activate the flapper valve assembly 30, the tubular housing 68 can be perforated or vented by any means known in the art, as described above, which can thereby expose the pressurized chamber 71 to the inner bore 69 via the vented section 110. The pressure in the inner bore 69 can be greater than the pressure previously in the pressurized chamber 71. This greater pressure from the inner bore 69 can then be communicated through the vented section 110, through the pressurized chamber 71 and the line 75, to the piston chamber 73, and can thereby increase the pressure in the piston chamber 73. This can create a pressure differential across the piston 90, as the second chamber 77 can remain at the reduced pressure. The pressure differential can draw the piston 90, and therefore the sleeve 70, upward toward the upper sub 80, for example. In one or more embodiments, the second chamber 77 can include any vents as necessary to allow the contents (e.g., air) therein to escape as the piston 90 moves toward the shoulder 96. In one or more embodiments, the contents of the second chamber 77 can escape between the piston 90 and the smooth-walled portion 86. In one or more embodiments, venting the second chamber 77 can be unnecessary, as the pressure differential between the second chamber 77 and the piston chamber 73 can be sufficiently great to move the piston 90, despite the pressure increases in the second chamber 77 resulting from the volume of the second chamber 77 decreasing.
The drawing of the sleeve 70 upward via a pressure differential across the piston 90 can also be described as releasing the hydrostatic pressure in the inner bore 69. Thus, upon activation, the sleeve 70 can be moved to the second position by simply perforating the tubular housing 68, without requiring mechanical manipulation or engagement of the sleeve 70. The hydrostatic pressure can thus draw the sleeve 70 from the first position (FIG. 1) to the second position (FIG. 2), for example.
In one or more embodiments, while the sleeve 70 slides from the first position to the second position, the flapper valve 67 can be progressively exposed and can eventually be released into the operative state. Accordingly, after entering the operative state, the flapper valve 67 can initially pivot to a closed position, blocking a flow of fluid in a first direction (e.g., downward, as shown), which can isolate portions of the wellbore completion below the flapper valve assembly 30 from portions above it. Furthermore, the flapper valve 67 can pivot to the open position, allowing an upward flow of fluid. In this manner, for example, the flapper valve 67 can selectively block fluid flowing therethrough. When selectively blocking fluid flow, for example, the flapper valve 67 can block a first flow of fluid (e.g., the downward flow), and can allow a second flow of fluid (e.g., the upward flow).
FIG. 3 depicts another embodiment of the flapper valve assembly 30, which can include a line 302 extending between and operatively connecting a controller 304 and the pressurized chamber 71. The controller 304 can be located at the surface of the wellbore or at another remote location or can be proximal the flapper valve assembly 30. Accordingly, to activate the flapper valve assembly 30, a signal can be sent from the controller 304 through the line 302 and to the second chamber 77 and/or the piston chamber 73. In one or more embodiments, the signal can be pneumatic, hydraulic, or both, such that a higher or lower pressure can be communicated through the line 302 into one of the chambers 73, 77, which can thereby allow one or both of the chambers 73, 77 to act as the above-described pressurized chamber 71 (FIGS. 1-2). For example, the controller 304 can include a compressor such that, to move the sleeve 70 from the first to the second position, the controller 304 can send a high pressure flow through the line 302 and into the one of the chambers 73, 77. This can create a pressure differential across the piston 90, thereby causing the sleeve 70 to slide upward, which can thereby release the flapper valve 67.
Furthermore, to re-stow the flapper valve 67, a flow can be evacuated from the piston chamber 73 by the controller 304 via the line 302, for example. This can provide a pressure differential in the reverse direction across the piston 90, which can cause the sleeve 70 to slide back down to stow the flapper valve 67. Although not shown, it will be appreciated that line 302 can include any valves, manifolds, headers, junctions, etc. as needed.
In one or more embodiments, the controller 304 can send an electrical signal to components of the flapper valve assembly 30 to effect movement of the flapper valve 67. For example, the flapper valve assembly 30 can include an electromagnetic solenoid or the like (not shown), which can be actuated to push or pull the sleeve 70 through its movement. Furthermore, the controller 304 can utilize wireless telemetry or wired signals to transmit instructions and can include any receiving devices positioned proximal the flapper valve assembly 30 in the wellbore
FIG. 4 depicts a cross-sectional view of yet another embodiment of the flapper valve assembly 30. The flapper valve assembly 30 can be substantially similar to the flapper valve assembly 30 described above with reference to FIGS. 1 and 2. Accordingly, the flapper valve assembly 30 can include a flapper valve 67 and a sliding sleeve 70 that can slide from a first to a second position by hydrostatic force. In one or more embodiments, the flapper valve 67 can have flat extents, as opposed to the saddle-shaped flapper valve 67 described above. In one or more embodiments, the flapper valve 67 can have a flat cross section, or can have a dome shape interior (not shown) to support additional load. In one or more embodiments, the flapper valve 67 can be similar to that described in U.S. patent application Ser. No. 11/010,072, the entirety of which is incorporated herein by reference to the extent it is not inconsistent with this disclosure.
The foregoing has outlined features of several embodiments so that those skilled in the art may better understand the detailed description that follows. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.
Certain embodiments and features have been described using a set of numerical upper limits and a set of numerical lower limits. It should be appreciated that ranges from any lower limit to any upper limit are contemplated unless otherwise indicated. Certain lower limits, upper limits and ranges appear in one or more claims below. All numerical values are “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.
Various terms have been defined above. To the extent a term used in a claim is not defined above, it should be given the broadest definition persons in the pertinent art have given that term as reflected in at least one printed publication or issued patent. Furthermore, all patents, test procedures, and other documents cited in this application are fully incorporated by reference to the extent such disclosure is not inconsistent with this application and for all jurisdictions in which such incorporation is permitted.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. A downhole tool, comprising:

a tubular housing having an inner bore;

a sleeve disposed in the inner bore and configured to slide between a first position and a second position;

a flapper valve pivotally coupled to the tubular housing, maintained in an inoperative position when the sleeve is in the first position, and pivotable between an open position and a closed position when the sleeve is in the second position; and

a pressurized chamber in fluid communication with the sleeve, wherein, upon activation of the downhole tool, a hydrostatic pressure is applied on the sleeve via the pressurized chamber, such that the sleeve slides from the first position to the second position.

2. The downhole tool of claim 1, wherein the tubular housing defines the pressurized chamber and further comprises a vented section extending between the inner bore and the pressurized chamber, wherein activation includes removing the vented section to provide fluid communication between the inner bore and the pressurized chamber.

3. The downhole tool of claim 2, wherein the vented section comprises a frangible material, a dissolvable material, or both.

4. The downhole tool of claim 1, further comprising a controller operatively connected to the pressurized chamber via a controller line, wherein activation includes the controller causing an increased pressure to be applied to the pressurized chamber.

5. The downhole tool of claim 1, wherein the tubular housing further comprises:

an upper sub in which the pressurized chamber is defined, wherein the upper sub provides a portion of the inner bore; and

a lower sub coupled to the upper sub, wherein the lower sub provides another portion of the inner bore and provides a valve seat, and wherein the flapper valve is pivotally coupled to the lower sub.

6. The downhole tool of claim 5, wherein:

the tubular housing includes a storage cavity defined therein, wherein the storage cavity is configured to receive the flapper valve in the inoperative position; and

the sleeve includes a lower end configured to engage the lower sub when the sleeve is in the first position, wherein the sleeve in the first position sealingly covers the storage cavity.

7. The downhole tool of claim 6, wherein the flapper valve is saddle-shaped, such that, when in the inoperative position, the flapper valve fits between substantially concentric cylindrical portions of the sleeve and the tubular housing in the storage cavity.

8. The downhole tool of claim 5, wherein the sleeve further comprises a piston having a first side facing the lower sub and a second side facing the upper sub, the piston being coupled to the sleeve and slidably engaging the tubular housing.

9. The downhole tool of claim 8, further comprising:

a piston chamber defined in the tubular housing adjacent the first side of the piston; and

a line extending from the pressurized chamber to the piston chamber, the line configured to provide fluid communication between the pressurized chamber and the piston chamber.

10. The downhole tool of claim 9, further comprising a second chamber defined adjacent the second side of the piston, wherein the piston is configured to slide toward the upper sub and reduce a volume of the second chamber when a pressure in the piston chamber is increased.

11. A method for plugging a casing string with a flapper valve assembly, comprising:

storing a flapper valve in a stowed position with a sleeve;

biasing the flapper valve toward a valve seat;

longitudinally moving the sleeve by applying a hydrostatic pressure differential across the sleeve to release the flapper valve from the stowed position; and

selectively blocking a flow of fluid through the casing string with the flapper valve.

12. The method of claim 11, wherein longitudinally moving the sleeve comprises increasing a pressure on a side of the sleeve.

13. The method of claim 12, wherein increasing the pressure on the side of the sleeve comprises:

perforating a tubular housing in which a pressurized chamber is defined, wherein, after the perforating, the pressurized chamber fluidly communicates with an inner bore of the tubular housing; and

communicating a bore pressure of the inner bore to a side of the sleeve via the pressurized chamber.

14. The method of claim 13, wherein longitudinally moving the sleeve further comprises isolating a second chamber disposed on a second side of the sleeve from the bore pressure, wherein a pressure in the second chamber is less than the bore pressure.

15. The method of claim 13, wherein perforating the tubular housing comprises dissolving a section of the tubular housing.

16. The method of claim 11, wherein longitudinally moving the sleeve comprises applying a pressure to a pressurized chamber with a controller in fluid communication with the pressurized chamber.

17. A flapper valve assembly, comprising:

a tubular housing connectable to a wellbore casing string and having a storage cavity defined therein;

a sleeve slidable between a first position and a second position, wherein the sleeve in the first position covers the storage cavity and the sleeve in the second position at least partially uncovers the storage cavity;

a flapper valve disposed in the tubular housing and pivotally connected thereto, wherein the flapper valve is contained in the storage cavity when the sleeve is in the first position, and wherein the flapper valve is pivotable between an open position and a closed position when the sleeve is in the second position; and

a pressurized chamber communicating with the sleeve and configured to create a pressure differential across at least a portion of the sleeve, such that the sleeve moves longitudinally from the first position to the second position.

18. The flapper valve assembly of claim 17, further comprising:

a piston having opposing first and second sides, wherein the piston is coupled to the sleeve and located between the sleeve and the tubular housing; and

a piston chamber fluidly communicating with the pressurized chamber and defined in the tubular housing adjacent the first side of the piston.

19. The flapper valve assembly of claim 18, further comprising a second chamber isolated from the pressurized chamber and defined at least partially in the tubular housing adjacent the second side of the piston, wherein, when the tubular housing is vented to communicate the inner bore with the pressurized housing, a pressure in the second chamber is less than a pressure in the piston chamber.

20. The flapper valve assembly of claim 18, wherein the tubular housing further comprises a dissolvable section, a frangible section, or both, which is removable to provide fluid communication between the inner bore and the pressurized chamber.