Sliding sleeve valve assembly with a fluid bypass

Abstract

A sliding sleeve valve assembly with a fluid bypass for use in a wellbore. When a downhole section of the casing string is isolated from an uphole section by setting an isolation element in the valve assembly, the fluid bypass can allow allow for the release of hydraulic pressure from the downhole section. The fluid bypass can be open by default, can be opened by exceeding a burst disc rating, or can be opened by shifting the sliding sleeve to the open position. The fluid bypass can provide fluid communication between the downhole section and the uphole section, or between the downhole section and the wellbore annulus. The fluid bypass may be formed by a path that circumvents sealing within the annulus between the sleeve and the housing, or the fluid bypass may be formed by defeating sealing within the annulus between the sleeve and the housing.

Description

SLIDING SLEEVE VALVE ASSEMBLY WITH A FLUID BYPASSTECHNICAL FIELD

[0001] The disclosure relates to downhole tools for subterranean wellbore operations, and more specifically to sliding sleeve valve assemblies with a fluid bypass.BACKGROUND

[0002] Well completions within a subterranean formation often include valve assemblies, integrated as part of a casing string, for selectively controlling access to the surrounding reservoir. Valve assemblies may include one or more sliding sleeves to selectively open ports to allow flow of materials between the interior of the casing string and the surrounding subterranean formation during operations, including, for example, during fluid injection for well stimulation operations (e.g. fracturing). Shifting a sliding sleeve may be accomplished by deploying an isolation member, such as a packer, downhole to engage the sleeve so that it can be shifted, hydraulically or mechanically. Engagement of the isolation member with the sleeve acts to seal the well downhole of the engaged isolation member.

[0003] When using an isolation member in a sliding sleeve valve assembly to isolate a downhole section of a closed end well from an uphole section, sliding the sleeve downhole decreases the volume of the downhole section, thereby increasing hydraulic pressure in the downhole section. The increased hydraulic pressure in the downhole section increases resistance to and may impede shifting the sleeve downhole and may also act to inadvertently shift the sleeve back uphole after downward pressure on the isolation element is reduced and before the isolation element can be disengaged from the sleeve.

[0004] Inadvertently shifting the sleeve uphole closes the ports in the valve assembly, which may be undesirable for well production or other operations requiring open ports. This effect is strongest for valve assemblies that are in close proximity to the toe of the well, as the smaller volumes respond with greater increases in pressure in response to shifting the sleeve and engaged isolation member downhole. To remedy the increased hydraulic pressure in the isolated downhole section, known solutions include a burst disc in the downhole section which opens at a predetermined pressure to allow fluid release from the downhole section into a decompression chamber. However, this approach is limited as a burst disc cannot be resealed, precluding thepotential for repeatedly opening and closing the sleeve without replacing the ruptured disc.

[0005] Thus, there is a need in closed end wells for a valve assembly capable of resisting inadvertent closing regardless of the number of instances of opening and closing the valve.SUMMARY

[0006] In accordance with the present disclosure, there are provided valve assemblies comprising a fluid bypass, methods for opening a fluid bypass of a valve assembly, methods for venting pressure from a pressure isolated downhole section of a completed well, and a well completions system.

[0007] In some embodiments, there is a valve assembly for integration within a casing string disposed within a subterranean formation, comprising a tubular housing comprising a wall defining a central passage therethrough and at least one port extending through the wall for allowing fluid communication between the central passage and the subterranean formation; a sleeve disposed within the housing and slidable within the central passage from a closed position, where the sleeve is axially aligned with at least one port, to an open position, where the sleeve is axially misaligned from the at least one port, the sleeve configured to engage an isolation member to seal a downhole section of the central passage from an uphole section; an annulus between an outer surface of the sleeve and an inner surface of the tubular housing comprising at least two seals flanking the at least one port to prevent fluid communication between the central passage and the subterranean formation when the sleeve is in the closed position; and a fluid bypass for venting pressure from the downhole section when the isolation member is engaged with the sleeve.

[0008] The fluid bypass may vent pressure from the downhole section by fluidly connecting the downhole section to the uphole section, or by allowing fluid communication between the downhole section and the wellbore annulus between the casing string and the wellbore. The fluid bypass may be open by default, may be opened by increasing the hydraulic pressure in the uphole section to exceed a burst disc rating, or may be opened by shifting the sleeve to the open position.

[0009] A fluid bypass that is open by default may be formed along a portion of the annulus between the outer surface of the sleeve and the inner surface of the tubular housing. There may be a sleeve port through the wall of the sleeve at a location upholeof the location where the isolation member is designed to engage the sleeve to provide fluid communication between the uphole section and the uphole end of the fluid bypass. An absence of seals from the sleeve port to the downhole end of the sleeve may provide fluid communication between the annulus and the downhole section. A burst disc may be present within the fluid bypass, possibly as a feature of the sleeve port, to limit access until the pressure differential exceeds the burst disc rating.

[0010] A fluid bypass that may be opened by shifting the sleeve to the open position may include means for removing sealing engagement within the annulus between the outer surface of the sleeve and inner surface of the tubular housing. An annular space comprising a radial enlargement of the annulus allows for misalignment of a sealing element following shifting the sleeve to the open position to allow fluid flow between the sealed downhole section of the central passage to the uphole section of the central passage.

[0011] The fluid bypass may comprise an annular space between the sleeve and the tubular housing wall. The valve assembly may further comprise between an outer surface of the sleeve and an inner surface of the tubular housing wall: a seal in an annular groove; and an annular ridge; wherein in a first sleeve position, the seal and the annular ridge are aligned to seal the fluid bypass; and wherein in a second sleeve position, the seal and the annular ridge are misaligned to open the fluid bypass.

[0012] There may be a second annular groove containing a second seal on the tubular housing inner surface downhole from the annular groove, and shifting the sleeve to a third sleeve position downhole from the second sleeve position aligns the second seal with the annular ridge to reclose the fluid bypass.

[0013] There may be a second annular ridge downhole from the annular ridge, and shifting the sleeve to a third sleeve position downhole from the second sleeve position aligns the seal with the second annular ridge to reclose the fluid bypass.

[0014] The annular ridge may be on the sleeve outer surface and the annular groove on the tubular housing inner surface. The second annular groove containing the second seal may be on the tubular housing inner surface.

[0015] The annular ridge may be on the tubular housing inner surface and the annular groove on the sleeve outer surface. The second annular ridge may be on the tubular housing inner surface.

[0016] There may be one or more sleeve ports to provide fluid access to the annular space, on one or both of the uphole side and downhole side of the location where the isolation element is designed to engage with the sleeve. There may be one or more sleeve ports to provide fluid access to the annulus, on one or both of the uphole side and downhole side of the location where the isolation element is designed to engage with the sleeve. The one or more sleeve ports to the annulus or to the annular space may comprise a burst disc.

[0017] The fluid bypass may connect the downhole section to the uphole section. The fluid bypass may vent pressure from the downhole section by fluidly connecting the downhole section to a wellbore annulus. The fluid bypass may comprise an opening in the tubular housing wall to connect the downhole section to the wellbore annulus. The sleeve may be a toe sleeve. The fluid bypass may include a one-way valve for allowing flow out of the downhole section while preventing flow into the downhole section.

[0018] In some embodiments, there is a method for venting pressure of a pressure isolated downhole section of a casing string disposed within a subterranean formation and comprising a valve assembly having a fluid bypass, comprising the steps: a) setting an isolation member in a central passage of a sleeve disposed in a tubular housing having at least one port openable for fluid communication between the central passage and the subterranean formation, the isolation member isolating a downhole section of the central passage from an uphole section; and b) shifting the sleeve downhole with respect to the tubular housing to open a fluid bypass to vent pressure from the downhole section.

[0019] There may be an annular ridge and a seal aligned between the sleeve and the tubular housing in step a), and in step b), shifting the sleeve downhole misalgns the seal and the annular ridge to open an annular space between the sleeve and the tubular housing that comprises the fluid bypass.

[0020] Opening the fluid bypass may connect the downhole section and the uphole section to allow flow from the downhole section to the uphole section. Opening the fluid bypass may connect the downhole section and a wellbore annulus to allow flow from the downhole section to the wellbore annulus. The sleeve may be a toe sleeve.

[0021] The method may further comprise after step b), step c) of performing a downhole operation. The downhole operation may include, but is not limited to, one ormore of fluid injection for well stimulation, water injection for water disposal, and steam injection for steam assisted gravity drainage. After step c), the method may further comprise shifting the sleeve further downhole to re-close the fluid bypass. Alternatively, the method may further comprise shifting the sleeve back uphole to reclose the fluid bypass.

[0022] The fluid bypass may allow for one-way flow out of the downhole section.

[0023] The method may further comprise before or after b), increasing pressure in the uphole section to exceed a burst disc rating, the burst disc located along the fluid bypass.

[0024] In some embodiments, there is a well completion system comprising a casing string installed within a wellbore intersecting a subterranean formation and comprising tubular elements, one or more standard valve assemblies, and at least one valve assembly having a fluid bypass. The fluid bypass may have a default open position, may be opened by exceeding a burst disc rating, or may be opened by shifting a sleeve within the valve assembly having the fluid bypass to the open position. It is preferred that the valve assembly with the fluid bypass is located at the toe of the casing string.BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In the Detailed Description section below, one or more embodiments of the present technology are described in relation to the attached figures. These embodiments are intended to provide a better understanding of the disclosure and how the disclosure may be put into practice. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments of the disclosure. Similar reference numerals indicate similar components.FIG. 1 is a schematic of a completed well with valve assemblies penetrating a subterranean formation.FIG. 2A is an axial cross-sectional side view of a valve assembly having a sliding sleeve in the closed position and engaged with an isolation member.FIG. 2B is an axial cross-sectional side view of the valve assembly from FIG. 2A with the sleeve in the open position and a fluid bypass, shown conceptuallyvia an open arrow, for venting fluid from a downhole section to an uphole section.FIG. 2C is an axial cross-sectional side view of the valve assembly from FIG. 2A with the sleeve in the open position and a fluid bypass, shown conceptually via an open arrow, for venting fluid from a downhole section to a wellbore annulus.FIG. 3A is an axial cross-sectional side view of a valve assembly with a sliding sleeve in the closed position, engaged with an isolation member, and a closed fluid bypass between the downhole section and the uphole section.FIG. 3B is an axial cross-sectional side view of a valve assembly with a sliding sleeve in the open position, engaged with an isolation member, and an open fluid bypass between the downhole section and the uphole section.FIG. 4A is an enlarged view of section A from FIG. 3A.FIG. 4B is an enlarged view of section B from FIG. 3B.FIG. 5 is a radial cross-sectional view of FIG. 3A and FIG. 3B through the dotted line indicated by a-a.FIG. 6A is an axial cross-sectional view of a valve assembly with a sliding sleeve in the closed position, engaged with an isolation member, and a fluid bypass between the downhole section and the uphole section.FIG. 6B is an axial cross-sectional view of the valve assembly of FIG. 6A with the sleeve in the open position.FIG. 7A is an axial cross-sectional side view of a valve assembly with a sliding sleeve in the closed position, engaged with an isolation member, and a closed fluid bypass between the downhole section and the wellbore annulus.FIG. 7B is an axial cross-sectional side view of a valve assembly with a sliding sleeve in the open position, engaged with an isolation member, and an open fluid bypass between the downhole section and the wellbore annulus.FIG. 8A is an enlarged view of section C from FIG. 7A.FIG. 8B is an enlarged view of section D from FIG. 7B.FIG. 9A is an axial cross-sectional side view of a valve assembly with a sliding sleeve in the closed position, engaged with an isolation member, and a closed fluid bypass between the downhole section and the uphole section.FIG. 9B is an axial cross-sectional side view of a valve assembly with a sliding sleeve in the open position, engaged with an isolation member, and an open fluid bypass between the downhole section and the uphole section.FIG. 9C is an axial cross-sectional side view of a valve assembly with a sliding sleeve in the open position, engaged with an isolation member, and a closed fluid bypass between the downhole section and the uphole section.DETAILED DESCRIPTION

[0026] This disclosure relates to a sliding sleeve valve assembly having a fluid bypass to allow a release of hydraulic pressure from an isolated downhole section in a wellbore. Various aspects of the disclosure will now be described with reference to the figures. For the purposes of illustration, components depicted in the figures are not necessarily drawn to scale. Instead, emphasis is placed on highlighting the various contributions of the components to the functionality of various aspects of the disclosure. A number of possible alternative features are introduced during the course of this description. It is to be understood that, according to the knowledge and judgment of persons skilled in the art, such alternative features may be substituted in various combinations to arrive at different embodiments of the present disclosure.

[0027] Referring to FIG. 1 , a typical completed well 1 comprises a casing string 2 extending vertically down from the surface 3 through a wellbore 4, drilled into a subterranean formation 8, before leveling off to a relatively horizontal section and ending at the toe 5. For some well completions, isolation material, typically cement, is passed down the casing string central passageway 6 out the toe 5 and back up through a wellbore annulus 7, between the casing string 2 and wellbore 4, to seal off the wellbore annulus 7. For closed end wells, cementing results in a complete seal at the toe 5. The casing string 2 may include one or more valve assemblies 10 at various positions along the length of the casing string. Valve assemblies can be manipulated, such as with a tool string 9 comprising, among other tools, an isolation member 26, for regulating flow between the casing string central passageway 6 and the subterranean formation 8. Engagement of the isolation member 26 along the casing string 2 creates potential for a pressure differential, where the section uphole of the engaged isolationmember, or uphole section 30, differs with respect to pressure from the section downhole of the engaged isolation member, or downhole section 28. In closed end wells, downhole section 28 may be sealed when isolation member 26 is engaged, resulting in changes in pressure when the volume of downhole section 28 is altered.

[0028] Referring to FIG. 2A, a valve assembly 10 generally includes a tubular housing 12 with a central passage 14 therethrough and one or more ports 16 for allowing fluid communication between the central passage and the subterranean formation adjacent the valve assembly. In some embodiments, the housing 12 may be assembled from multiple components, such as, for example, from an uphole sub, central sub, and downhole sub, coupled together via threaded connections or other mechanism known in the art. In some embodiments, in light of developing 3D printing technology, the housing 12 may be formed as a single piece, eliminating the need for assembly prior to integration within a casing string. The uphole and downhole ends of housing 12 may include threading (not shown) or other means for connection to components for construction of a casing string, including other valve assemblies or tubulars typically used for this purpose. The central passage 14 of valve assembly 10 contributes to and is continuous with a casing string central passage 6.

[0029] Design of a valve assembly housing falls within the expertise of the person skilled in the art. Considerations for sizing, including the wall thickness and inner and outer diameters, and materials for construction can be chosen for the particular application based on prior art and common knowledge for valve assemblies with sliding sleeves. This includes design of a region within the housing having an enlarged inner diameter for accommodation of one or more sliding sleeves and allowing generally for an inner diameter that approximates the casing string inner diameter, excluding common profiles for locating tools and those inherent in connections between tubular components.

[0030] It is appreciated that the ports 16 may comprise multiple ports, and the ports can be evenly or unevenly spaced and / or aligned about the circumference of a part of housing 12. It is also possible to have a single port instead of multiple ports. Furthermore, the ports 16 may have similar or different cross-sectional areas and shapes, e.g. cylindrical, frustoconical, tapered toward or away from the subterranean formation.

[0031] A sleeve 20 is disposed in the housing 12 and is movable with respect to housing 12 to selectively provide or deny access through the ports depending onrelative axial positioning of the sleeve 20 with respect to the ports 16. The range of movement of sleeve 20 is dictated by hard stops which limit axial movement within the housing 12. In some embodiments, the hard stops may be in the form of an uphole shoulder 12a or a downhole shoulder 12b, that limit further uphole and downhole movement, respectively. In some embodiments, a hard stop may be in the form of an uphole or downhole end of another sleeve. Sleeve 20 may be in a closed position, where it is axially aligned with ports 16 (FIG. 2A), preventing flow therethrough, or sleeve 20 may be in an open position, where it is axially misaligned from ports 16 (FIG. 2B and 2C), allowing flow therethrough.

[0032] Prevention of flow in annulus 19 between the sleeve 20 and the housing 12 may be managed through use of seals 18, strategically placed in close proximity to the one or more ports 16, or the ends of the one or more sleeves present within the housing. As is known in the art, one option for sealing is by way of O-rings situated in grooves extending from the inner surface of the housing, or the external surface of a sleeve, and when in contact with the opposing surface, acts to prevent flow past the O-ring. In some embodiments, the O-rings may be further supported using back up rings. Other options for seals 18, include, but are not limited to, vee rings, T-seals, and polypacks.

[0033] It should be understood by the person skilled in the art that for the valve assembly to fulfill its role in preventing flow between the casing string central passage 6 and the subterranean formation 8 when sleeve 20 is in the closed position, a seal on each side of port 16 is recommended. The seals 18 can be located in close proximity to the port 16, such as those shown in FIGS. 2A-C, or may be distanced from the port 16, for example at location in close proximity to the downhole end of sleeve 20.

[0034] In operation, an isolation member 26 is deployed down the well, as part of a tool string, and set in the valve assembly by engaging sleeve 20, to isolate a downhole section 28 of the central passage from an uphole section 30. The isolation member 26 may be a packer assembly, a bridge plug or another suitable isolation member. Positioning of the isolation member 26 within the target can be accomplished using any means known in the art. For example, use of a collet or other radially biased element to move into a locate profile to effect a change in tension that once detected may confirm positioning. Locate profiles can be transient, such as those formed by a space between the end of the sleeve and the downhole shoulder when the sleeve isin the closed position. Locate profiles can also be permanent, for example as an indentation in the inner surface of the casing string or the sleeve.

[0035] Once the isolation member is set in the central passage, the sleeve 20 may be shifted downhole as shown in FIGS. 2B and 2C. This may be accomplished by increasing hydraulic pressure in the uphole section 30, causing the sleeve to move downhole. For shifting the sleeve using hydraulic means it is preferable to employ two or more seals 18 to seal off annulus 19 so that when shifting the sleeve, fluid introduced uphole acts on isolation member 26 as opposed to bypassing isolation member 26 without shifting the sleeve. Alternatively, the sleeve may be shifted using set down force provided by a shifting tool that is deployed downhole, typically using coiled tubing or drill pipe, to engage with the sleeve to shift it downhole. Shifting the sleeve downhole decreases the volume and increases the hydraulic pressure in the downhole section 28. As described below, when the isolation member is engaged with the sleeve, hydraulic pressure in the downhole section may be vented by way of a fluid bypass. As shown conceptually in FIGS. 2B and 2C, the fluid bypass 40 may provide fluid communication between the downhole section 28 and one or both of the uphole section 30 (FIG. 2B) and the wellbore annulus 7 (FIG. 2C). In some embodiments, the fluid bypass may include a valve for allowing one-way flow out of the downhole section while preventing fluid from flowing into the downhole section.

[0036] In some embodiments, fluid bypass 40 is present when the sleeve is closed and when the sleeve is open (FIG. 6A and 6B). In this embodiment, the fluid bypass 40 may be static in that shifting the sleeve does not alter the fluid bypass and typically involves bypassing sealing interfaces through additional ports or removal of seals. In this embodiment, shifting of the sleeve is preferably performed using mechanical methods known in the art, the shifting of the sleeve causing an initial increase in pressure in the downhole section that drops over time due to venting through the fluid bypass, the time required dependent on the size and shape of the fluid bypass.

[0037] In some embodiments, movement of the sleeve to the open position opens the fluid bypass 40 (FIG. 3B and 4B). In this embodiment, the bypass is open by defeating a sealing engagement by eliminating contact between one or more seals and one or more contact surfaces.

[0038] Turning to FIGS. 3A, 3B, 4A, and 4B, downhole seal 48, identified as the seal located closest to the downhole end of the sleeve, is in sealing engagementwith both the sleeve and the housing when the sleeve is in the closed position, and when the sleeve is moved to the open position, the sealing engagement of the downhole seal between one of the housing or the sleeve is negated, allowing fluid movement through the annulus at the location of the downhole seal. In some embodiments, sealing engagement of the downhole seal is lost when the sleeve is moved to the open position due to alignment of the downhole seal with an annular space that is radially larger than the annulus in the location where the downhole seal can be in sealing arrangement with both the housing and the sleeve.

[0039] In an embodiment, as shown in FIG. 3A and 3B and in enlarged views from dashed boxes A and B shown in FIG. 4A and 4B, respectively, the fluid bypass 40 of valve assembly 10 is formed by an annular space 42 between an outer surface 20a of sleeve 20 and an inner surface 12c of the tubular housing 12. In the closed position (FIG. 3A and 4A), axial alignment of an annular ridge 44 protruding from the outer surface 20a with an annular groove 46 on inner surface 12c containing downhole seal 48, prevents flow through annular space 42 between downhole section 28 and uphole section 30 as downhole seal 48 contacts annular ridge 44 (see dashed arrows and x in FIG. 4A). In the open position (FIG. 3B and 4B), moving sleeve 20 downhole creates axial separation of annular ridge 44 relative to downhole seal 48. In this position, the annular ridge 44 is not in contact with downhole seal 48, allowing fluid to flow through the annular space 42 and, forming the fluid bypass 40. In this illustrated example, the fluid bypass 40 fluidly connects the downhole section 28 of the central passage to the uphole section 30 of the central passage, thereby providing a flow path, indicated by dashed arrows, that bypasses the engaged isolation member 26 in the central passage. When open, the fluid bypass allows venting of pressure in downhole section by allowing fluid to move from the downhole section to the uphole section.

[0040] In some embodiments, access to annular space 42 from uphole section 30 of central passage 14 may be by way of a sleeve port 20b, as shown in FIG. 3A, 3B, 4A, and 4B, located on sleeve 20 uphole of where isolation member 26 is designed to engage sleeve 20. In some embodiments, access between annular space 42 and uphole section 30 of central passage 14 may be by way of the uphole end of sleeve 20, made possible by the absence of one or more seals 18 between the uphole end of sleeve 20 and the annular space 42, when sleeve 20 is in the open position.

[0041] In some embodiments, the opposing surfaces on which the annular ridge 44 and the downhole seal 48 are situated may be reversed such that thedownhole seal 48 is located on the sleeve outer surface 20a, and the annular ridge located on the tubular housing inner surface 12c. In this case, the downhole seal 48 would move downhole of the annular ridge when the sleeve moves downhole, thereby opening the fluid bypass.

[0042] As shown in FIG. 3A, 3B, 4A, and 4B, annular space 42 is shown as a radial enlargement of the annulus 19 between the housing 12 and the sleeve 20 by a reduction in the thickness of sleeve 20 on opposite sides of annular ridge 44. It is appreciated that other embodiments are possible. In some embodiments, the annular space may comprise a radial enlargement of the annulus between the housing and the sleeve through a reduction in the thickness of the housing wall on one or both of the uphole side and downhole side of an annular ridge on the inner surface of the housing. In some embodiments, the annular space is formed by a radial enlargement of the annulus between the housing and the sleeve through a reduction in the thickness of one or both of the housing and the sleeve on the uphole side of annular ridge.

[0043] In some embodiments, access to annular space 42 from downhole section 28 of central passage 14 may be affected by the absence of seals downhole of annular ridge 44, as shown in FIG. 3A, 3B, 4A, and 4B. In some embodiments, access between annular space 42 and downhole section 28 of central passage 14 may be by way of a sleeve port (not shown) located on sleeve 20 downhole of where isolation member 26 is designed to engage sleeve 20.

[0044] In some embodiments, sleeve ports providing access to the annular space from the uphole section of the central passage and / or from the downhole section of the central passage may further comprise a burst disc, providing fluid access after a threshold pressure differential has been reached. The burst disc rating is the pressure differential at which the burst disc ruptures and allows flow of fluid therethrough. A burst disc rating can be chosen based on the characteristics of the well, and can range from about 500 psi to 1000 psi, and even as high as 10,000 psi. In some embodiments, sleeve ports may comprise a check valve to allow fluid to flow out of the downhole section, while preventing fluid to move into the downhole section from the annular space.

[0045] The annular space can include variations in number, shape, and size. In some embodiments, valve assembly 10 may comprise an annular space between sleeve 20 and housing 12 that extends radially along the entire circumference of one or both of the inner surface of housing 12 and the outer surface of sleeve 20, wherefluid may access the uphole end of annular space 42 via one or more sleeve ports 20b. In some embodiments, annular space 42 may comprise one or more channels that extend from the uphole end of annular space 42 to annular ridge 44. For example, in FIG. 5, a radial cross-section as indicated by the dashed lines a-a in FIG. 3A and 3B, shows radial distribution of four annular channels 43 about and extending from the outer surface 20a of sleeve 20, each annular channel 43 fluidly connected to a sleeve port 20b. In some embodiments, annular channels 43 are linear, extending axially from an uphole end to the annular ridge 44. In some embodiments, annular channels may be helical in shape, extending from the uphole end and twisting radially toward the annular ridge 44. In some embodiments, annular channel 43 comprises a single channel extending from an uphole end to the annular ridge 44. In some embodiments, annular channel 43 comprises two or more channels extending from an uphole end to the annular ridge 44.

[0046] Referring to FIG. 6A and 6B, the fluid bypass 40 may be static, providing fluid communication between the downhole section 28 and the uphole section 30 in both the open position (FIG. 6A) and the closed position (FIG. 6B). The fluid bypass 40 (indicated by dashed arrows) is made possible by inclusion of a sleeve port 20b, located on sleeve 20 uphole of where isolation element 26 is designed to engage sleeve 20, and the absence of a seal 18 between the sleeve port 20b and the sleeve downhole end. The pathway is present regardless of the axial position of the sleeve relative to ports 16.

[0047] In some embodiments, when the sleeve 20 is in the open position, the fluid bypass (shown conceptually in FIG. 2C) vents pressure in the downhole section by allowing movement of fluid from the downhole section 28 to the wellbore annulus 7.

[0048] Referring to FIGS. 7A and 8A, the sleeve 20 is in the closed position in the tubular housing 12 and the ports 16 and fluid bypass are closed. When an isolation member 26 is set in the sleeve to seal the downhole section 28 from the uphole section 30, and the sleeve is shifted downhole as shown in FIG. 7B and 8B, the fluid bypass 40 is opened, allowing fluid to flow between the downhole section and the wellbore annulus 7.

[0049] FIGS. 8A and 8B show enlarged views, as indicated by boxes C and D from FIG. 7A and 7B, of the fluid bypass of FIGS. 7A and 7B, respectively. The fluid bypass is similarto that described above with reference to FIGS. 3A, 3B, wherein there is an annular space 42 between the sleeve outer surface 20a and the tubular housinginner surface 12c, and a combination of an annular ridge 44 on an opposing surface to an annular groove 46 containing a downhole seal 48 that when in contact seals the fluid bypass as in FIG. 8A (indicated by x— -), and when not in contact, opens the fluid bypass 40 as in FIG. 8B. The tubular housing 12 includes a bypass port 41 in its wall that is part of the fluid bypass to allow fluid to flow from the downhole section 28 to the wellbore annulus 7. In the illustrated example, the fluid bypass goes from the sleeve downhole end 21 , through the annular space 42, and out the bypass port 41 to the wellbore annulus 7. Alternatively, there may be an opening in the sleeve wall, downhole of the isolation member 26, through which fluid can flow to enter the annular space 42. The opening and / or bypass port may include a burst disc that bursts at a predetermined pressure to expose the opening and / or bypass port and open the fluid bypass.

[0050] The presence of cement, or other suitable isolation material, within the wellbore annulus 7 may limit movement of fluid from the downhole section to the wellbore annulus 7 due to lack of access. In some embodiments, bypass port 41 may be fluidly connected to the one or more ports 16 via a suitable conduit through housing 12 that extends axially from the exit point of bypass port 41 to the one or more ports 16. In this embodiment, fluid communication may be established between the downhole section 28 and the wellbore annulus 7 and the uphole section 30, via ports 16.

[0051] The valve assembly described herein is ideally suitable for use as a toe sleeve where there is typically a smaller volume in the downhole section below the isolation element which leads to a larger pressure increase in response to shifting the sleeve downhole. The valve assembly may also be used at various other stages in the wellbore besides the toe sleeve. As such, a well completion system comprising a casing string comprising tubular elements, connected end to end and including one or more standard valve assemblies, and at least one valve assembly comprising a fluid bypass as described above. In some embodiments, the well completion system comprises multiple valve assemblies lacking a fluid bypass, or standard valve assemblies, in combination at least one valve assembly comprising a fluid bypass. In some embodiments, the well completion system comprises a single valve assembly having a fluid bypass, the single valve assembly located at the toe of the well.

[0052] After the fluid bypass has been opened and venting of the downhole section is completed, the fluid bypass may be left open, or it may be reclosed. In oneembodiment, the fluid bypass may be re-closed by shifting the sleeve to the closed position. In one embodiment, the fluid bypass is re-closed by shifting the sleeve to an additional downhole position such that sealing engagement is restored. Depending on which opposing surface the seal and the annular ridge are on, this is accomplished by having a second annular ridge or a second seal. In the example shown in FIGS. 9A, 9B, and 9C, the annular ridge 44 in the annular space 42 between the sleeve outer surface 20a and the tubular housing inner surface 12c contacts a second downhole seal 48a in a second annular groove 46a in the tubular housing inner surface, located downhole from the downhole seal 48. The alignment of the second downhole seal 48a with annular ridge 44 re-seals the fluid bypass (FIG. 9C). Alternatively, if the location of the annular ridge and the downhole seal are reversed with the downhole seal 48 on the sleeve outer surface 20a, and the annular ridge 44 on the tubular housing inner surface 12c, there would be a second annular ridge on the tubular inner surface 12c downhole from the first annular ridge, which would contact the downhole seal 48 when the sleeve moves downhole. The recloseable fluid bypass may be between the downhole section 28 and the uphole section 30 as shown in FIGS. 9A-9C, or it may be between the downhole section and the wellbore annulus 7.

[0053] Although the present disclosure has been described and illustrated with respect to preferred embodiments and preferred uses thereof, it is not to be so limited since modifications and changes can be made therein which are within the full, intended scope of the disclosure as understood by those skilled in the art.

Claims

1. CLAIMS1. A valve assembly for integration within a casing string disposed within a subterranean formation, comprising: a tubular housing comprising a wall defining a central passage therethrough and at least one port extending through the wall for allowing fluid communication between the central passage and the subterranean formation; a sleeve disposed within the housing and slidable within the central passage from a closed position, where the sleeve is axially aligned with the at least one port, to an open position, where the sleeve is axially misaligned from the at least one port, the sleeve configured to engage an isolation member to seal a downhole section of the central passage from an uphole section; an annulus between an outer surface of the sleeve and an inner surface of the tubular housing comprising at least two seals flanking the at least one port to prevent fluid communication between the central passage and the subterranean formation when the sleeve is in the closed position; and a fluid bypass for venting pressure from the downhole section when the isolation member is engaged with the sleeve.

2. The valve assembly of claim 1 , wherein the fluid bypass is opened by moving the sleeve to the open position.

3. The valve assembly of claim 1 or 2, wherein the fluid bypass vents pressure from the downhole section by fluidly connecting the downhole section to the uphole section.

4. The valve assembly of claim 3, wherein the fluid bypass comprises an annular space between the sleeve and the tubular housing wall.

5. The valve assembly of claim 4, further comprising between an outer surface of the sleeve and an inner surface of the tubular housing: a seal in an annular groove; andan annular ridge; wherein in a first sleeve position, the seal and the annular ridge are aligned to seal the fluid bypass; wherein in a second sleeve position, the seal and the annular ridge are misaligned to open the fluid bypass.

6. The valve assembly of claim 5, wherein the annular ridge is on the sleeve outer surface and the annular groove is on the tubular housing inner surface.

7. The valve assembly of claim 5, wherein the annular ridge is on the tubular housing inner surface and the annular groove is on the sleeve outer surface.

8. The valve assembly of any one of claims 1 or 2, wherein the fluid bypass vents pressure from the downhole section by fluidly connecting the downhole section to a wellbore annulus.

9. The valve assembly of any one of claims 1-8, wherein the sleeve is a toe sleeve.

10. The valve assembly of any one of claims 1-9, wherein one or more sleeve ports provide fluid access to the annulus on one or both of the uphole side and downhole side of the location where the isolation element is designed to engage with the sleeve.

11. The valve assembly of any one of claims 4-7, wherein one or more sleeve ports provide fluid access to the annular space, on one or both of the uphole side and downhole side of the location where the isolation element is designed to engage with the sleeve12. The valve assembly of any one of claims 5-7, wherein there is a second annular groove containing a second seal on the tubular housing inner surface downhole from the annular groove, and shifting the sleeve to a third sleeve position downhole from the second sleeve position aligns the second seal with the annular ridge to reclose the fluid bypass.

13. The valve assembly of any one of claims 5-7, wherein there is a second annular ridge downhole from the annular ridge, and shifting the sleeve to a third sleeve positiondownhole from the second sleeve position aligns the second annular ridge with the seal to reclose the fluid bypass.

14. The valve assembly of any one of claims 1-13, wherein the fluid bypass includes a one-way valve for allowing flow out of the downhole section while preventing flow into the downhole section.

15. A method for venting pressure of a pressure isolated downhole section of a casing string disposed within a subterranean formation and comprising a valve assembly having a fluid bypass comprising the steps: a) setting an isolation member in a central passage of a sleeve disposed in a tubular housing having at least one port openable for fluid communication between the central passage and the subterranean formation, the isolation member isolating a downhole section of the central passage from an uphole section; and b) shifting the sleeve downhole with respect to the tubular housing to open a fluid bypass to vent pressure from the downhole section.

16. The method of claim 15, wherein the fluid bypass comprises a burst disc, further comprising before or after b), increasing pressure in the uphole section to exceed a rating of the burst disc.

17. The method of claim 15 or 16, wherein there is an annular ridge and a seal aligned between the sleeve and the tubular housing in step a), and in step b), shifting the sleeve downhole misaligns the seal and the annular ridge to open an annular space between the sleeve and the tubular housing that comprises the fluid bypass.

18. The method of any one of claims 15-17, wherein opening the fluid bypass connects the downhole section and the uphole section to allow flow from the downhole section to the uphole section.

19. The method of claim 15 or 16, wherein opening the fluid bypass connects the downhole section and a wellbore annulus to allow flow from the downhole section to the wellbore annulus.

20. The method of any one of claims 15-19, wherein the sleeve is a toe sleeve.

21. The method of any one of claims 15-20, further comprising after step b): c) performing a downhole operation, including, but not limited to, fluid injection for well stimulation, water injection for water disposal, and steam injection for steam assisted gravity drainage.

22. The method of claim 21 , further comprising between steps b) and c), shifting the sleeve further downhole to re-close the fluid bypass.

23. The method of any one of claims 15-22, wherein the fluid bypass allows for one-way flow out of the downhole section.

24. A well completion system comprising a casing string installed within a wellbore intersecting a subterranean formation and comprising tubular elements, one or more standard valve assemblies, and at least one valve assembly according to any one of claims 1-14.

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