Overpressure toe valve with atmospheric chamber

Abstract

A toe valve for use in a wellbore includes: a tubular mandrel having couplings at longitudinal ends thereof for assembly as part of a casing or liner string; a housing extending along a periphery of the mandrel and mounted thereto; a valve piston disposed in an annulus formed between the housing and the mandrel, movable between an open position and a closed position, disposed between a valve port of the housing and a valve port of the mandrel in the closed position; a fastener releasably connecting the valve piston to the housing in the closed position; an atmospheric chamber forming a portion of the annulus adjacent to the valve piston; and a drive piston disposed in the annulus adjacent to a drive port of the mandrel and operable to release the valve piston.

Claims

1. A toe valve for use in a wellbore, comprising: a tubular mandrel having couplings at longitudinal ends thereof for assembly as part of a casing or liner string; a housing extending along a periphery of the mandrel and mounted thereto; a valve piston disposed in an annulus formed between the housing and the mandrel, movable between an open position and a closed position, disposed between a valve port of the housing and a valve port of the mandrel in the closed position; a fastener releasably connecting the valve piston to the housing in the closed position; an atmospheric chamber forming a portion of the annulus adjacent to the valve piston; a drive piston disposed in the annulus adjacent to a drive port of the mandrel and operable to release the valve piston; and a trigger piston disposed in the annulus between the valve piston and the drive piston.

2. The toe valve of claim 1, further comprising: a hydraulic activator disposed in a wall of the housing between the trigger piston and the drive piston and linking the drive piston and the trigger piston.

3. The toe valve of claim 2, wherein: the annulus comprises an upper annulus and a lower annulus, the toe valve further comprises hydraulic fluid disposed in a drive chamber of the upper annulus adjacent to the drive piston and disposed in a trigger chamber of the lower annulus adjacent to the trigger piston, and the hydraulic activator is in fluid communication with the drive chamber and the trigger chamber.

4. The toe valve of claim 3, wherein the hydraulic activator comprises a hydraulic port and a pressure control device disposed in the hydraulic port.

5. The toe valve of claim 3, further comprising: a drive spring disposed in the drive chamber; and a trigger spring disposed in the trigger chamber, wherein the drive spring is in an extended position and the trigger spring is in a contracted position when the toe valve is in the closed position.

6. The toe valve of claim 2, wherein: a valve chamber forms a portion of the annulus adjacent to the valve piston and the trigger piston, and the valve chamber is in fluid communication with the valve port of the housing when the toe valve is in the closed position.

7. The toe valve of claim 6, further comprising a valve spring disposed in the valve chamber.

8. The toe valve of claim 1, further comprising: hydraulic fluid disposed in a hydraulic chamber of the annulus adjacent to the drive piston and the trigger piston.

9. The toe valve of claim 8, further comprising a second fastener releasably connecting the trigger piston to the housing in the closed position.

10. The toe valve of claim 8, wherein: a valve chamber forms a portion of the annulus adjacent to the valve piston and the trigger piston, and the valve chamber is in fluid communication with the valve port of the housing when the toe valve is in the closed position.

11. The toe valve of claim 8, wherein: a bore chamber forms a portion of the annulus adjacent to the drive piston and a boss of the mandrel, and the toe valve further comprises a drive spring disposed in the bore chamber.

12. The toe valve of claim 8, wherein: the trigger piston has a stinger formed therein for engaging the valve piston, and the housing has a shoulder formed therein for receiving the trigger piston.

13. The toe valve of claim 1, wherein the fastener is shearable and is accessible from an exterior of the toe valve.

14. The toe valve of claim 1, further comprising a debris excluder disposed in the drive port.

15. A method of using the toe valve of claim 1 in a wellbore, comprising: assembling the toe valve as part of a casing or liner string; deploying the casing or liner string into the wellbore; cementing the casing or liner string into the wellbore; pressure testing the cemented casing or liner string by pressurizing a bore thereof, wherein the toe valve is in the closed position during the assembly, deployment, cementation, and pressure test; and after pressure testing, increasing the pressure in the bore to an overpressure, thereby shifting the toe valve from the closed position to the open position.

16. A toe valve for use in a wellbore, comprising: a tubular mandrel; a housing extending along a periphery of the mandrel; couplings at longitudinal ends of the toe valve for assembly as part of a casing or liner string; a valve piston disposed in an annulus formed between the housing and the mandrel, movable between an open position and a closed position, disposed between a valve port of the housing and a valve port of the mandrel in the closed position; a fastener releasably connecting the valve piston to the housing in the closed position; an atmospheric chamber forming a portion of the annulus adjacent to the valve piston; a drive piston disposed in the annulus adjacent to a drive port of the mandrel and operable to release the valve piston; and a trigger piston disposed in the annulus between the valve piston and the drive piston.

17. The toe valve of claim 16, further comprising a hydraulic activator disposed in a wall of the housing between the trigger piston and the drive piston and linking the drive piston and the trigger piston.

18. The toe valve of claim 17, wherein: the annulus comprises an upper annulus and a lower annulus, the toe valve further comprises hydraulic fluid disposed in a drive chamber of the upper annulus adjacent to the drive piston and disposed in a trigger chamber of the lower annulus adjacent to the trigger piston, and the hydraulic activator is in fluid communication with the drive chamber and the trigger chamber.

19. The toe valve of claim 18, wherein the hydraulic activator comprises a hydraulic port and a pressure control device disposed in the hydraulic port.

20. The toe valve of claim 16, wherein the trigger piston has a stinger formed therein for engaging the valve piston.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, 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 disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

(2) FIGS. 1A and 1B illustrate a first overpressure toe valve with an atmospheric chamber in a closed position, according to one embodiment of the present disclosure.

(3) FIG. 2A illustrates the first toe valve in a first intermediate position while shifting from the closed position to an open position. FIG. 2B illustrates the first toe valve in a second intermediate position while shifting from the closed position to the open position.

(4) FIG. 3 illustrates the first toe valve in the open position.

(5) FIG. 4A illustrates a second overpressure toe valve with an atmospheric chamber in a closed position, according to another embodiment of the present disclosure. FIG. 4B illustrates the second toe valve in a first intermediate position while shifting from the closed position to an open position.

(6) FIG. 5A illustrates the second toe valve in a second intermediate position while shifting from the closed position to the open position. FIG. 5B illustrates the second toe valve in the open position.

DETAILED DESCRIPTION

(7) FIGS. 1A and 1B illustrate a first overpressure toe valve 1 with an atmospheric chamber 12 in a closed position, according to one embodiment of the present disclosure. The toe valve 1 may include a mandrel 2, a housing 3, a drive piston 4, a trigger piston 5, a valve piston 6, and one or more springs 7d,t,v. The mandrel 2 may be a tubular member having a longitudinal bore formed therethrough and couplings, such as threads (only lower thread shown), formed at longitudinal ends thereof for assembly of the toe valve 1 as part of a casing string or liner string.

(8) The housing 3 may be a sleeve including a plurality of sections 3a-c extending along the mandrel 2. The mandrel 2 may have a boss formed in a periphery thereof and an upper longitudinal end of the upper housing section 3a may be mounted thereto, such as by a threaded connection. An interface between the mandrel 2 and the upper housing section 3a may be sealed, such as by an elastomeric o-ring 8, carried in a groove formed in the mandrel boss. The upper housing section 3a may have an enlarged diameter upper portion, a reduced diameter lower portion, and an increased thickness mid portion connecting the upper and lower portions. An upper annulus may be formed longitudinally between the boss of the mandrel 2 and the mid portion of the upper housing section 3a and radially between the upper portion of the upper housing section and a periphery of the mandrel.

(9) The drive piston 4 may be disposed in the upper annulus and may divide the upper annulus into an upper bore chamber and a lower hydraulic drive chamber. The drive piston 4 may be annular and may carry inner and outer seals, such as elastomeric o-rings 8, in respective inner and outer grooves formed therein. The drive piston 4 may also have an inner recess formed in an upper portion thereof which may facilitate fluid communication with the mandrel bore. The mandrel 2 may have one or more (two shown) drive ports 2d formed through a wall thereof adjacent to a top of the upper annulus to provide fluid communication between the mandrel bore and the upper bore chamber. A debris excluder, such as a rupture disk 9, may be disposed in each upper drive port 2d and mounted to the mandrel 2, thereby closing the drive ports and isolating the mandrel bore from the bore chamber. The drive rupture disks 9 may have a set pressure greater than a cementing pressure and a testing pressure.

(10) Hydraulic fluid 10, such as refined and/or synthetic oil, may be disposed in the hydraulic drive chamber. For simplicity, the hydraulic fluid 10 is shown in FIGS. 1A and 1B and depicted in FIGS. 2A and 2B with an arrow, though it remains in the hydraulic chambers throughout shifting of the first toe sleeve 1. The drive spring 7d may be a compression spring, such as a coil spring, and may also be disposed in the hydraulic drive chamber and may have an upper end bearing against the drive piston 4 and a lower end bearing against the upper housing section 3a, thereby biasing the drive piston toward the mandrel boss. The mid housing section 3b may overlap the lower portion of the upper housing section 3a and a top of the mid housing section may abut the mid portion of the upper housing section.

(11) The lower portion of the upper housing section 3a may include a hydraulic activator having a radial hydraulic port formed through a wall thereof and an angled hydraulic port formed through the wall thereof. A hydraulic pressure control device, such as a rupture disk 11, may be disposed in the angled hydraulic port and may be mounted to the lower portion of the upper housing section 3a thereby closing the angled hydraulic port and isolating the hydraulic drive chamber from a hydraulic trigger chamber. The hydraulic rupture disk 11 may have a set pressure greater than the cementing pressure and the testing pressure. The radial hydraulic port may be in fluid communication with the hydraulic drive chamber via an unsealed portion of the interface between the upper housing section 3a and the mandrel 2. The radial hydraulic port may be in fluid communication with the angled hydraulic port via an unsealed portion of the interface between the upper housing section 3a and the mid housing section 3b. The angled hydraulic port may be in fluid communication with the hydraulic trigger chamber via another unsealed portion of the interface between the upper housing section 3a and the mandrel 2.

(12) For isolating the hydraulic activator from leakage or bypass, the lower portion of the upper housing section 3a may carry an inner seal and a pair of outer seals, such as elastomeric o-rings 8, in respective inner and outer grooves formed therein for the respective interfaces with the mandrel 2 and the mid housing section 3b. An upper one of the outer seals may be located above the radial hydraulic port and a lower one of the outer seals may be located adjacent to a lower portion of the angled hydraulic port. The inner seal may be located between the radial and angled hydraulic ports. The mid housing section 3b may be mounted to a lower longitudinal end of the upper housing section 3a, such as by a threaded connection.

(13) A lower annulus may be formed longitudinally between the bottom of the upper housing section 3a and a top of the lower housing section 3c and radially between the mid housing section and the periphery of the mandrel 2. The trigger piston 5 and the valve piston 6 may be disposed in the lower annulus and may divide the lower annulus into the upper hydraulic trigger chamber, a mid valve chamber, and a lower atmospheric chamber 12. The trigger piston 5 may be annular and may carry inner and outer seals, such as elastomeric o-rings 8, in respective inner and outer grooves formed therein. The trigger piston 5 may also have inner and outer recesses formed in a lower portion to define a stinger which may facilitate interaction with the valve spring 7v. The hydraulic fluid 10 may be disposed in the hydraulic trigger chamber. The trigger spring 7t may be a compression spring, such as a coil spring, may also be disposed in the hydraulic trigger chamber, and may have an upper end bearing against the upper housing section 3a and a lower end bearing against the trigger piston 5, thereby biasing the trigger piston toward the valve piston 6.

(14) The valve spring 7v may be a compression spring, such as a wave spring, may be disposed in the valve chamber, and may have an upper end bearing against the trigger piston 5 and a lower end bearing against the valve piston 6, thereby biasing the trigger piston away from the valve piston. The mandrel 2 may have one or more (four shown) valve ports 2v formed through a wall thereof adjacent to a mid-point of the lower annulus to provide fluid communication between the mandrel bore and the valve chamber when the toe valve 1 is in the open position (FIG. 3). The mid housing section 3b may have one or more (two shown) valve ports 3v formed through a wall thereof adjacent to the mandrel valve ports 2v to provide fluid communication between the valve chamber and a cement sheath (not shown) disposed between the toe valve 1 and a periphery of the wellbore when the toe valve is in the open position.

(15) The valve chamber may be in fluid communication with the housing valve ports 3v via an unsealed portion of the interface between the valve piston 6 and the mid housing section 3b. The valve piston 6 may be releasably connected to the mid housing section 3b by one or more (pair shown) shearable fasteners 13. Collectively, the shearable fasteners 13 may be set to withstand a force exerted on an upper face of the valve piston 6 by hydrostatic wellbore pressure acting thereon as the toe sleeve 1 is being deployed into the wellbore. The valve piston 6 may have a groove formed in a periphery thereof for receiving inner portions of the shearable fasteners 13 and the mid housing section 3b may have a port formed through the wall thereof for each shearable fastener for receiving an outer portion thereof. The shearable fasteners 13 may be accessible from the exterior of the toe valve 1 for adjustment of the set force thereof while the toe valve is in the oilfield.

(16) The valve piston 6 may be annular and may carry a pair of inner seals and an outer seal, such as elastomeric o-rings 8, in respective inner and outer grooves formed therein. When the valve piston 6 is in the upper kept position, an upper one of the inner seals may be located above the mandrel valve ports 2v and a lower one of the inner seals may be located below the mandrel valve ports, thereby isolating the mandrel bore from the valve chamber and the atmospheric chamber 12. When the valve piston 6 is in the upper kept position, the outer seal may be located below the housing valve ports 3v, thereby isolating the atmospheric chamber 12 from the wellbore hydrostatic pressure. When the valve piston 6 is in the upper kept position, the trigger spring 7t may be in a contracted position and the drive spring 7d may be in an extended position.

(17) The lower housing section 3c may have a reduced diameter upper portion, an enlarged diameter lower portion, and an increased thickness mid portion connecting the upper and lower portions. The mid housing section 3b may overlap the upper portion of the lower housing section 3c and a bottom of the mid housing section may abut the mid portion of the lower housing section. For isolating the atmospheric chamber 12, the upper portion of the lower housing section 3c may carry an outer seal and the mid portion of the lower housing section may carry an inner seal, such as elastomeric o-rings 8, in respective inner and outer grooves formed therein for the respective interfaces with the mid housing section 3b and the mandrel 2.

(18) FIG. 2A illustrates the first toe valve 1 in a first intermediate position while shifting from the closed position to the open position. The toe valve 1 may be assembled as part of a casing string or a liner string and usually located in proximity to a lower end of the string. Once assembled, the casing or liner string is then deployed into the wellbore adjacent to an oil or gas bearing formation. The casing or liner string may then be cemented into position in the wellbore by pumping cement slurry down a bore thereof and up an annulus formed between the casing or liner string and the wellbore. Once the cement slurry has cured into a cement sheath in the wellbore annulus, a pressure test may be performed by pressurizing the bore of the casing or liner string to the testing pressure and holding the testing pressure for a period of time, such as between five minutes and one hour. The toe valve 1 may remain in the closed position during assembly with the casing or liner string, deployment into the wellbore, cementing of the casing or liner string, and pressure testing.

(19) Once the pressure test has concluded, the bore of the casing or liner string may be further pressurized to an overpressure. The overpressure may be greater than the testing pressure which may be greater than the cementing pressure. The overpressure may exceed the testing pressure by an amount ranging between one-hundred five percent and one-hundred twenty-five percent. The overpressure may be equal to or greater than the set pressures of the rupture disks 9, 11. The overpressure may be held until the toe valve 1 shifts from the closed position to the open position.

(20) The drive rupture disks 9 may burst, thereby opening the drive ports 2d and providing fluid communication between the mandrel bore and the bore chamber. Pressurized bore fluid 14 may enter the bore chamber and exert a fluid force on upper faces of the drive piston 4. The drive piston 4 in turn may pressurize the hydraulic drive chamber until the hydraulic rupture disk 11 bursts, thereby opening the angled hydraulic port and hydraulically linking the drive piston 4 and the trigger piston 5. The contracted trigger spring 7t may be free to extend and pressure by the hydraulic fluid 10 may act in conjunction therewith to move the linked pistons 4, 5 longitudinally downward together and the stinger of the trigger piston 5 may engage the valve spring 7v.

(21) FIG. 2B illustrates the first toe valve 1 in a second intermediate position while shifting from the closed position to the open position. Contraction of the valve spring 7v may exert force on the valve piston 6 and the shearable fasteners 13, thereby fracturing the shearable fasteners and releasing the valve piston from the mid housing section 3b.

(22) FIG. 3 illustrates the first toe valve 1 in the open position. Release of the valve piston 6 from the housing 3 allows the force exerted by hydrostatic pressure acting on an upper face of the valve piston to push the valve piston longitudinally downward into the atmospheric chamber 12. As the upper one of the inner seals 8 of the valve piston 7 approaches the mandrel valve ports 2v, the fluid 14 from the mandrel bore may also exert pressure on the upper face of valve piston 7, thereby assisting with movement thereof into the atmospheric chamber 12. Shifting of the toe valve 1 may be complete when a lower face of the valve piston 6 engages the top of the lower housing section 3c, thereby providing fluid communication between the mandrel valve ports 2v and the housing valve ports 3v via the valve chamber. The mandrel bore fluid 14 may then be pumped into the formation adjacent to the wellbore by fracturing the cement sheath.

(23) Alternatively, the rupture disks 9 and/or the rupture disk 11 may be set to burst at the testing pressure instead of the overpressure. Alternatively, the shearable fasteners 13 may be set to withstand the force exerted on the upper face of the valve piston 6 by the trigger piston 5 having the testing pressure exerted thereon. Alternatively, a different type of debris excluder may be used instead of the rupture disks 9, such as filters or an array of micro-ports. Alternatively, the springs 7d,t,v and/or the rupture disks 9 may be omitted.

(24) FIG. 4A illustrates a second overpressure toe valve 15 with an atmospheric chamber 22 in a closed position, according to another embodiment of the present disclosure. The toe valve 15 may include a mandrel 16, a housing 17, a drive piston 18, a trigger piston 19, a valve piston 20, and a drive spring 21. The mandrel 16 may be a tubular member having a longitudinal bore formed therethrough and couplings, such as threads (only lower thread shown), formed at longitudinal ends thereof for assembly of the toe valve 15 as part of a casing string or liner string.

(25) The housing 17 may be a sleeve including a plurality of sections 17a,b extending along the mandrel 16. The mandrel 16 may have a boss formed in a periphery thereof and an upper longitudinal end of the upper housing section 17a may be mounted thereto, such as by a threaded connection. An interface between the mandrel 16 and the upper housing section 17a may be sealed, such as by an elastomeric o-ring 8, carried in a groove formed in the mandrel boss. An annulus may be formed longitudinally between the boss of the mandrel 16 and a top of the lower housing section 17b and radially between the upper housing section 17a and the periphery of the mandrel.

(26) The drive piston 18, the trigger piston 19, and the valve piston 20 may be disposed in the annulus and may divide the annulus into an upper bore chamber, a mid hydraulic chamber, a mid valve chamber and the lower atmospheric chamber 22. The drive piston 18 may be annular and may carry inner and outer seals, such as elastomeric o-rings 8, in respective inner and outer grooves formed therein. The drive piston 18 may also have an inner recess formed in an upper portion thereof which may facilitate fluid communication with the mandrel bore. The mandrel 16 may have one or more (two shown) drive ports 16d formed through a wall thereof adjacent to a top of the annulus to provide fluid communication between the mandrel bore and the upper bore chamber. A debris excluder, such as the rupture disk 9, may be disposed in each upper drive port 16d and mounted to the mandrel 16, thereby closing the drive ports and isolating the mandrel bore from the bore chamber. The drive spring 21 may be a compression spring, such as a wave spring, may be disposed in the bore chamber, and may have an upper end bearing against the mandrel boss and a lower end bearing against the drive piston 18, thereby biasing the drive piston away from the mandrel boss.

(27) The hydraulic fluid 10 may be disposed in the hydraulic chamber and may hydraulically link the drive piston 18 and the trigger piston 19. The trigger piston 19 may be annular and may carry inner and outer seals, such as elastomeric o-rings 8, in respective inner and outer grooves formed therein. The trigger piston 19 may also have inner and outer recesses formed in a lower portion to define a stinger which may facilitate interaction with the valve piston 20. The upper housing section 17a may have a shoulder 17s formed in an inner surface thereof for receiving the trigger piston 19.

(28) The mandrel 16 may have one or more (four shown) valve ports 16v formed through a wall thereof adjacent a lower portion of the annulus to provide fluid communication between the mandrel bore and the valve chamber when the toe valve 15 is in the open position (FIG. 5B). The upper housing section 17a may have one or more (two shown) valve ports 17v formed through a wall thereof adjacent to the mandrel valve ports 16v to provide fluid communication between the valve chamber and a cement sheath (not shown) disposed between the toe valve 15 and a periphery of the wellbore when the toe valve is in the open position. The valve chamber may be in fluid communication with the housing valve ports 17v via an unsealed portion of the interface between the valve piston 20 and the upper housing section 17a.

(29) The trigger piston 19 may be releasably connected to the upper housing section 17a by a shearable fastener 23. The shearable fastener 23 may be set to withstand a force exerted on a lower face of the trigger piston 19 by hydrostatic wellbore pressure acting thereon as the toe sleeve 15 is being deployed into the wellbore. The trigger piston 19 may have a groove formed in a periphery thereof for receiving an inner portion of the shearable fastener 23 and the upper housing section 17a may have a port formed through the wall thereof for receiving an outer portion of the shearable fastener.

(30) The valve piston 20 may be releasably connected to the upper housing section 17a by a shearable fastener 24. The shearable fastener 24 may be set to withstand a force exerted on an upper face of the valve piston 20 by hydrostatic wellbore pressure acting thereon as the toe sleeve 15 is being deployed into the wellbore. The valve piston 20 may have a groove formed in a periphery thereof for receiving an inner portion of the shearable fastener 24 and the upper housing section 17a may have a port formed through the wall thereof for receiving an outer portion of the shearable fastener. The shearable fasteners 23, 24 may be accessible from the exterior of the toe valve 15 for adjustment of the set forces thereof while the toe valve is in the oilfield.

(31) The valve piston 20 may be annular and may carry a pair of inner seals and an outer seal, such as elastomeric o-rings 8, in respective inner and outer grooves formed therein. When the valve piston 20 is in the upper kept position, an upper one of the inner seals may be located above the mandrel valve ports 16v and a lower one of the inner seals may be located below the mandrel valve ports, thereby isolating the mandrel bore from the valve chamber and the atmospheric chamber 22. When the valve piston 20 is in the upper kept position, the outer seal may be located below the housing valve ports 17v, thereby isolating the atmospheric chamber 22 from the wellbore hydrostatic pressure.

(32) The lower housing section 17b may have a reduced diameter upper portion, an enlarged diameter lower portion, and an increased thickness mid portion connecting the upper and lower portions. The upper housing section 17a may overlap the upper portion of the lower housing section 17b and a bottom of the upper housing section may abut the mid portion of the lower housing section. For isolating the atmospheric chamber 22, the upper portion of the lower housing section 17b may carry an outer seal and the mid portion of the lower housing section may carry an inner seal, such as the o-rings 8, in respective inner and outer grooves formed therein for the respective interfaces with the upper housing section 17a and the mandrel 16.

(33) FIG. 4B illustrates the second toe valve 15 in a first intermediate position while shifting from the closed position to the open position. The second toe valve 15 may be assembled with the casing or liner string, deployed into the wellbore, cemented into place, and pressure tested, as discussed above for the first toe valve 1. Once the pressure test has concluded, the bore of the casing or liner string may be further pressurized to the overpressure. The drive rupture disks 9 may burst, thereby opening the drive ports 16d and providing fluid communication between the mandrel bore and the bore chamber. The pressurized bore fluid 14 may enter the bore chamber and exert a fluid force on upper faces of the drive piston 18. The drive piston 18 in turn may pressurize the hydraulic chamber which may exert force on the trigger piston 19 and the associated shearable fastener 23, thereby fracturing the shearable fastener and releasing the trigger piston from the upper housing section 17a.

(34) FIG. 5A illustrates the second toe valve 15 in a second intermediate position while shifting from the closed position to the open position. Release of the trigger piston 19 may allow the linked pistons 18, 19 to move longitudinally downward together and the stinger of the trigger piston may engage the valve piston. The trigger piston 19 may exert force on the valve piston 20 and the shearable fastener 24, thereby fracturing the shear pin and releasing the valve piston from the upper housing section 17a. The pistons 18-20 may continue the downward longitudinal movement until the trigger piston 19 engages the shoulder 17s.

(35) FIG. 5B illustrates the second toe valve 15 in the open position. Release of the valve piston 20 from the housing 17 allows the force exerted by hydrostatic pressure acting on an upper face of the valve piston to push the valve piston longitudinally downward into the atmospheric chamber 22. As the upper one of the inner seals 8 of the valve piston 20 approaches the mandrel valve ports 16v, the fluid 14 from the mandrel bore may also exert pressure on the upper face of valve piston 20, thereby assisting with movement thereof into the atmospheric chamber 22. Shifting of the toe valve 15 may be complete when a lower face of the valve piston 20 engages the top of the lower housing section 17b, thereby providing fluid communication between the mandrel valve ports 16v and the housing valve ports 17v via the valve chamber. The mandrel bore fluid 14 may then be pumped into the formation adjacent to the wellbore by fracturing the cement sheath.

(36) Alternatively, the rupture disks 9 may be set to burst at the testing pressure instead of the overpressure. Alternatively, the shearable fastener 19 and/or the shearable fastener 24 may be set to withstand having the testing pressure exerted thereon. Alternatively, a different type of debris excluder may be used instead of the rupture disks 9, such as filters and/or an array of micro-ports. Alternatively, the rupture disks 9 may be omitted.

(37) While the toe valves 1, 15 are shown vertically oriented in the Figures, in actuality, the toe valves may be deployed in deviated, such as horizontal, portions of the wellbore so that up and down in the Figures reflects up-hole and downhole, respectively.

(38) Alternatively, either toe valve 1, 15 could be used upside down without affecting the operation thereof. Alternatively, to facilitate assembly, either or both toe valves 1, 15 may have a fill port and/or vent port for each hydraulic chamber.

(39) While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope of the invention is determined by the claims that follow.