WO2019218073A1

WO2019218073A1 - Well string staging tool

Info

Publication number: WO2019218073A1
Application number: PCT/CA2019/050665
Authority: WO
Inventors: Nathan Brian Coffey; Scott Kenneth MURDOCH
Original assignee: 1966109 Alberta Ltd.
Priority date: 2018-05-16
Filing date: 2019-05-16
Publication date: 2019-11-21

Abstract

Described are various embodiments of a well string staging tool comprising an elongated outer housing assembly and a hollow elongated inner assembly which is maintained within the elongated outer housing assembly and permitted limited relative axial sliding movement. The elongated inner assembly is reversibly slidable in response increasing and decreasing injection fluid pressures received therein and acting on one or pistons provided with means to inhibit the ingress of debris and particulate matter therein. The permitted limited relative axial sliding movement of said elongated inner assembly unobstructs and obstructs more or more fluid ports in an outer wall of the elongated outer housing assembly so as to selectively allow delivery of fluid to a wellbore annular space.

Description

WELL STRING STAGING TOOL

RELATED APPLICATION

[0001] The present application is an International Patent Application which claims benefit of priority to United States Provisional Patent Application serial number 62/672,507 entitled “WELL STRING STAGING TOOL” filed May 16, 2018, the disclosure of which is herein incorporated by reference.

FIELD OF THE DISCLOSURE

[0002] The present disclosure relates to cement staging tools and, in particular, to the infiltration of debris into certain areas of such tools. BACKGROUND

[0003] This background information is provided to reveal information believed by the applicant to be of possible relevance. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art or forms part of the general common knowledge in the relevant art. [0004] In order to collect hydrocarbon products from drilled reservoir formations, subterranean oil and gas wells require the inflow of hydrocarbon products into a well string, which generally is tubular. The well string is inserted into a wellbore and has a proximal end located near the ground surface and a distal end which is located near a well production zone. As the well string has a smaller diameter than the wellbore into which it is inserted, an annulus is therefore defined between the wellbore wall and the well string. The annulus, or annular space, extends axially along the well string. Inserting and maintaining the well string in the wellbore is known in the industry as well completion.

[0005] There are several techniques known in the art for well completion. One such technique is known as cement-back monobore completion which is where the distal production zone of the wellbore is left uncased so as to allow hydrocarbon products to flow into the well string. This uncased section, as known as open hole, is therefore exposed to the subterranean formations from where hydrocarbon products can be retrieved and thus permitted to flow via the well string to the proximal end at the ground surface where they can be collected. The portion of the wellbore from where hydrocarbons are not collected is the non-production zone along which a portion of well string lines. The non-production zone is generally lined in at least a portion of the annular space with cement, and therefore this is known in the industry as cement completion. Accordingly, in cement completions the production zone is sealed, via the cement in the annulus from contaminates. The cement in the annular space also secures the well string in place within the wellbore such that the distal end is maintained in the desired location of the production zone, that being in the open hole.

[0006] The cementing operation to the secure the well string in the wellbore in cement- back monobore well completions typically involves the placement of a cement staging tool along a portion of the well string. Located distally to the cement staging tool along the well string, in typical cement-back monobore well completions, are one or more liner packers. The well string is inserted in the wellbore such that the well string extends essentially coaxially within the wellbore from the proximal end near the ground surface to the distal end open hole end near the production zone.

[0007] Cement staging tools known in the art are generally provided as tubular devices which comprise an inner tubular assembly and outer tubular assembly. Ports allow a cement slurry which is inj ected from the surface down the well string to flow from the inner tubular assembly through the outer tubular assembly into the annular space between the wellbore wall and the well string. The cement slurry exiting from the port then cures to secure the well string in place and seals the production zone from contaminants. Once the wellbore is completed, hydrocarbon products flow from the production zone up the well string to the surface.

[0008] In prior art devices, the inner tubular assembly is permitted to selectively reversibly slide within the outer tubular assembly under the pressure provided by injecting a cement slurry down the well string and into the cement staging tool. The sliding action of the inner tubular assembly within the outer tubular assembly allows for the selective opening and closing of the ports located in the outer tubular assembly wall, which are initially blocked by a portion inner tubular assembly wall, such that the cement slurry may enter into the annular space. The cement slurry is blocked from flowing into the production zone by the one or more liner packers and thus the cement slurry exiting the ports is only permitted to flow in annular space of the non-production zone. The continued injection of cement slurry down the well string causes the cement slurry to be forced to flow upwards from the cement staging tool into the annular space, thereby cementing the well string within the wellbore.

[0009] U.S. Patent Application Publication Number US 2004/0154798A1, entitled “ZERO DRILL COMPLETION AND PRODUCTION SYSTEM”, filed February 5, 2004 and assigned to Baker Hughes Incorporated describes a pressure activated cementing valve for incorporation into a well string having inner and outer circulation ports located in a bore wall and an outer tool casing, respectively. An axially sliding sleeve is provided which initially obstructs a fluid flow channel between the inner and outer ports. Once the well string is desirably placed downhole, the sleeve is positionally displaced by fluid pressure applied within the well string so as to open inner and outer ports such that a cement slurry pumped down the well string can flow into the annulus around the well string. A second sleeve is then displaced from an initial position by increasing the pressure within the well string and fluid flowing through a fluid port acting on one end causes the second sleeve to slide and obstruct the inner and outer circulation ports.

[0010] U.S. Patent Application Publication Number US 2010/0224371 Al, entitled “CIRCULATION CONTROL VALVE AND ASSOCIATED METHOD”, filed March 4, 2009 and assigned to Halliburton Energy Services, Inc. describes tubular valve assembly for cementing wellbores which comprises an outer tubular member having ports through a wall of the outer tubular member and an inner tubular member located within the outer tubular member. The inner tubular member in an initial position obstructs fluid flow through the ports and is reciprocally displaceable within the outer tubular member so as to allow fluid flow through the ports. As fluid pressure within the well string is increased, the inner tubular member slides within the outer tubular member against a bias provided by an internal pressurized chamber defined between the outer and inner tubular members and the ports are thus opened. The outer tubular member has a lug ring with lugs secured to interior slide thereof. As the inner tubular member is displaced within the outer tubular member, the lugs proceed through a path defined by a recessed profile in a sleeve secured to the inner tubular member thereby limiting the amount of axial movement of the inner tubular member relative the outer tubular member under increased and decreased pressure provided by the fluid. Initially, as the fluid pressure is increased and the inner tubular member is displaced, the lugs travel in the recessed profile to a zone where the lugs may reside as the initially increased fluid pressure in the well string is released and the ports are maintained in an open position. The lugs are then maintained in said zone by the bias provided by internal pressurized chamber. In this position a cement slurry injected down the well string may exit into the annulus through the ports in the outer tubular member. An additional application fluid pressure in the well string to overcome the bias provided by internal pressurized chamber will cause the lugs to advance to another zone in the recessed profile where the ports are still open. A subsequent release of fluid pressure then causes the lugs, under the bias provided by internal pressurized chamber, to advance to a final zone in the recessed profile where the inner tubular member is slide relative to the outer tubular member such that the ports are closed. Further applications fluid pressure will not allow the ports to open as the lugs are maintained in a locked-out position or zone in the recessed profile. The ports are therefore openable once the well string is desirably located within a wellbore so as allow cementing of the well string and permanently closable once a sufficient amount of cement has been injected into the annular space.

[0011] International Patent Application Publication Number PCT/CA2016/051216 entitled“APPARATUS AND METHODS FOR CEMENTING OF WELLBORES”, filed October 20, 2016 and applied for by Modern Wellbore Solutions Ltd. describes similar device as discussed above with respect to U. S. Patent Application Publication Number US 2010/0224371 Al in that the device comprises and outer tubular member within which is disposed and inner tubular member wherein the outer tubular member has ports through a wall thereof. The inner tubular member in an initial position obstructs fluid flow through the ports and is reciprocally displaceable within the outer tubular member to as so allow fluid flow through the ports. As a cement slurry is injected down the well string, the inner tubular member is displaced so as to expose the ports in the wall of the outer tubular member and allow the cement slurry to flow through. The inner tubular member is biased in a port-closed position by a spring or biasing means which is located in one of a plurality of first pistons, having actuating surfaces. The plurality of first pistons, are defined by a cavity bordered by an inner surface of the outer tubular member and an outer surface of the inner tubular member. In operation, the plurality of one or more first pistons are in fluid communication via a first aperture with the wellbore annular space such that fluid may travel and in out of the first aperture as the inner tubular member slides relative to and within the outer tubular member. A plurality of second pistons are also defined between the inner surface of the outer tubular member and the outer surface of the inner tubular member. The plurality of second pistons are also fluid communication via a second aperture with the wellbore annular space such that fluid may travel in and out of the first aperture as the inner tubular member slides relative to and within the outer tubular member. As a cement slurry is injected down a well string, the cement slurry, under pressure, acts on a pressure actuatable surface defined circumferentially at an exposed up-hole surface end of the inner tubular member which causes the inner tubular member to slide within the outer tubular member toward a downhole end of the device and the springs in the plurality of the pistons are compressed as well as the plurality of first and second pistons. In doing so, the inner tubular member is displaced to a port open position and cement slurry is permitted to exit the ports. Similar to U.S. Patent Application Publication Number US 2010/0224371, the outer tubular member has a lug ring with lugs coupled to interior slide thereof. As the inner tubular member is displaced within the outer tubular member, the lugs proceed through a path defined by a recessed profile in a sleeve secured to the inner tubular member thereby limiting the amount of axial movement of the inner tubular member relative the outer tubular member under increased and decreased pressure provided by the fluid. Initially, as the fluid pressure is increased the inner tubular member is displaced. As more pressure is applied by the injecting of the cement slurry acting on the pressure actuatable surface, the inner tubular member is further displaced, but limited in the amount of displacement by the lugs travelling within the recessed profile. When pressure is reduced to a point less than biasing force of the springs, the spring cause the inner tubular member to slide within and relative to the outer tubular member such that the ports can at least partially close. Additionally, if the pressure in the annular space is greater than the pressure of the cement slurry acting on the pressure actuatable surface, slurry in the annular space enters the first and second apertures also causing the inner tubular member to return nearer the initial position by acting the first and second pistons and at least partially closing the ports. Therefore, variations in the cement slurry injection pressure and pressure differentials between inside the device and in the annular space in operation causes the inner tubular member to cycle between port open and partially closed configurations. Once the pressure of the cement slurry advancing into the annular space is equal to or greater than that of the injection pressure, the cement slurry in the annular space causes the first and second pistons, under the assistance of the springs, to displace the inner tubular member to a port-closed position and the lugs thus move within the recessed profile to full port-closed position zone of the recess profile. The inner tubular member thus obstructs further cement slurry from exiting the ports. As the inner tubular member is first displaced from the initial position, as discussed above, a ratchet formed by co-operating surfaces on the inner surface of the outer tubular member and the outer surface of the inner tubular member near the location of the pressure actuatable surface irreversibly advances such that the lugs in the recessed profile cannot return to the starting position and once the lugs have advanced to the full port-closed position zone, the ratchet locks the inner tubular member relative the outer tubular member such that the ports cannot be reopened by further application of differential cement slurry pressures either within the well string or the wellbore annular space.

[0012] Fluids in cementing well strings in wellbores and the wellbores themselves contain debris and fine particulate materials. These fine particulate materials and debris pose problems in the functioning of cement staging tools, such as those noted above. Cement staging tools, being machined devices with several moving parts, channels, recessed profiles and chambers have several places where fine particulate materials and debris may encroach or intrude within the machined tolerances between various interacting and cooperating parts. For example, in the case of the injecting a cement slurry down a well string to exit through ports in a cement staging tool such as those described above, debris and fine particulate material may enter into the piston apertures, the pistons, the recessed profiles and in between sliding parts, as well as other unwanted areas of the devices, thus rendering the devices inoperable and unable to complete well string cementing operations. In the event that a cement staging tool is rendered inoperable prior to the completion of well string cementing operations, it may be necessary to remove the well string and its component parts from the wellbore, which is not only timing consuming, but also costly. Therefore, it would be desirable to provide a cement staging tool which has provisions to ameliorate the infiltration of fine particulate materials and debris into at least some of the areas of the cement staging tool where they pose problems and thus reduce the likelihood of the cement staging tool being rendered inoperable prior to completing the cementing operations of a well string.

SUMMARY [0013] The following presents a simplified summary of the general inventive concepts described herein to provide a basic understanding of some aspects of the disclosure. This summary is not an extensive overview of the disclosure. It is not intended to restrict key or critical elements of embodiments of the disclosure or to delineate their scope beyond that which is explicitly or implicitly described by the following description and claims. [0014] A need exists for a cement staging tool that overcomes some of the drawbacks of known devices, or at least, provides a useful alternative thereto. Some aspects of this disclosure provide examples of such a well string staging tool for delivering fluids to a wellbore annular space which has provisions to ameliorate the infiltration of fine particulate materials and debris into at some of the areas of the well string staging tool where such debris and fine particulate matter may pose problems and thus reduce the likelihood of the well string staging tool being rendered inoperable prior to completing the cementing operations of a well string.

[0015] Described are various embodiments of a well string staging tool comprising an elongated outer housing assembly and a hollow elongated inner assembly which is maintained within the elongated outer housing assembly and permitted limited relative axial sliding movement. The elongated inner assembly is reversibly slidable in response increasing and decreasing fluid injection pressures received therein and acting on one or pistons provided with means to inhibit the ingress of debris and particular matter therein. The permitted limited relative axial sliding movement of the elongated inner assembly unobstructs and obstructs more or more fluid ports in an outer wall of the elongated outer housing assembly so as to selectively allow delivery of fluid to a wellbore annular space.

[0016] In accordance with one aspect, there is provided a well string staging tool for delivering a fluid to a desired zone within a wellbore. The well string staging tool comprises an elongated outer housing assembly having a proximal end and a distal end and an outer housing assembly lumen. The elongated outer housing assembly is adapted near the proximal end thereof for coupling and fluid communication with a downhole portion of a well. The is also provided an elongated inner assembly having an inner assembly lumen in fluid communication with a portion of the outer housing assembly lumen for receiving fluid from the well string and configured for reversible axial slidable communication within the outer housing assembly lumen along a predefined travel path in response injection pressures of the fluid. The elongated outer housing assembly has one or more fluid ports through a wall thereof for allowing the fluid to exit the outer housing assembly lumen which are obstructed by a wall portion of the elongated inner assembly when the elongated inner assembly is an initial position. The elongated inner assembly is displaceable from the initial position along the travel path in response to increases and decreases of the injection pressure of the fluid relative to an annular space fluid pressure so as to unobstruct the one or more fluid ports and selectively allow egress of the fluid into the annular space between the elongated outer housing assembly and a wellbore wall. One or more chambers are defined between an outer surface of the elongated inner assembly and an inner surface of the elongated outer housing assembly and are provided where a portion of the chambers forms one or more pistons, each of the pistons having an aperture for allowing fluid transfer between the inner assembly lumen or the annular space and wherein the apertures have a screening of a mesh size suitable for inhibiting the ingress particulate matter into each of the one or more pistons.

[0017] In some exemplary embodiments of the well string staging tool a portion of the pistons comprises one or more first pistons located near the distal end of the well string staging tool. The one or more first pistons each include at least one aperture operable to allow the passage of fluid from interior the elongated inner assembly lumen into the one or more first pistons and where, under increased injection fluid pressure relative the annular space pressure, the first piston is caused to expand and the elongated inner assembly consequently to travel along the travel path towards the proximal end and the one or more fluid ports to open.

[0018] In some exemplary embodiments, the first piston aperture includes a pressure responsive burst disc for initially sealing across the first piston aperture so as to obstruct fluid flow from interior the inner assembly lumen into the first piston when the inner assembly is in the initial position and to rupture in response to a predetermined injection fluid pressure so as to allow the passage of fluid into the first piston.

[0019] In some exemplary embodiments, the well string staging tool further comprises one or more shear pins for maintaining the elongated inner assembly in the initial position. The shear pins are responsive to break under a predetermined axial sliding force acting on the elongated inner assembly so as to allow axial sliding displacement of the elongated inner assembly relative the elongated outer housing assembly.

[0020] In some exemplary embodiments, when the elongated inner assembly is axially displaced within the outer housing lumen in response to increased fluid injection pressure, the elongated inner housing assembly slides and an interior of the first piston is exposed to the elongated outer housing lumen.

[0021] In some exemplary embodiments, the well string staging tool further comprises one or more biasing means configured bias to the elongated inner assembly toward initial position.

[0022] In some exemplary embodiments, the biasing means are disposed in at least one of the chambers. Furthermore, in some exemplary embodiments, the at least one chamber in which the biasing means is disposed comprises a second piston located between the proximal end and the distal end of the well string staging tool. The second piston includes at least one second piston aperture operable to allow the passage of fluid from the annular space into the second piston when the annular space fluid pressure is greater than the fluid injection pressure and causes the second piston to expand and consequently the elongated inner assembly to return to near the initial position along the travel path. [0023] In some exemplary embodiments, a portion of the pistons comprises a third piston located between the proximal end and the distal end of the well string staging tool. The third piston includes at least one third piston aperture operable to allow the passage of fluid from interior the elongated inner assembly lumen into the third piston, wherein increased injection fluid pressure relative the annular space fluid pressure causes the third piston to expand and the elongated inner assembly to travel along the travel path consequently towards the proximal end and the one or more fluid ports to open.

[0024] In some exemplary embodiments, a portion of the pistons comprises a fourth piston located between the proximal end and the distal end of the well string staging tool. The fourth piston includes at least one fourth piston aperture operable to allow the passage of fluid from the annular space into the fourth piston when the annular space fluid pressure is greater than the fluid injection pressure and causes the fourth piston to expand and the elongated inner assembly consequently to return to near the initial position along the travel path. [0025] In some exemplary embodiments of the well string staging tool the one or more fluid ports are provided at an angle relative a central longitudinal axis of the well string staging tool.

[0026] In some exemplary embodiments, the travel path is defined by a longitudinally extending recessed profile on the outer surface of the elongated inner assembly engageable by a lug pin coupled to an inner surface of the elongated outer housing assembly. During the axial sliding movement, the lug pin being is displaced in the recessed profile.

[0027] In some exemplary embodiments, the well string staging tool further comprises a lug ring holder circumferentially encasing a portion of the elongated inner assembly and fixed in position relative to a portion of the inner surface of the elongated outer housing assembly. The lug ring holder has an elongate slot for receiving therethrough a portion of the lug pin for travel in the recessed profile.

[0028] In some exemplary embodiments, the well string staging tool further comprises a lug ring circumferentially encasing a portion of the elongate inner assembly having coupled thereto the lug pin wherein the lug depends through the elongate slot for engageable communication with the recessed profile. In some exemplary embodiments, the lug pin is further circumferentially displaceable in the elongate slot

[0029] In some exemplary embodiments, the recessed profile is a provided as a J-slot profile and wherein the lug pin is maintained in a starting zone when the elongated inner assembly is in the initial position and when the elongated inner assembly is displaced under increased fluid injection pressure, the lug pin advances to a longitudinally extending portion of the J-slot where the one or more fluid ports are unobstructed. When the fluid injection pressure is decreased to where the elongated inner assembly returns to near the initial position, the lug pin advances to a working sequential zone in the recessed profile where the one or more fluid ports are obstructed.

[0030] In some exemplary embodiments, the J-slot profile comprises a repeating pattern which repeats a predetermined number of times. Each repetition is interconnected and the pattern terminates at a fluid port obstructed lock-out zone. [0031] In some exemplary embodiments, the outer surface of the elongated inner assembly and the inner surface of the elongated outer housing assembly further comprise complementary formations for inhibiting rotation of the elongated inner assembly relative the elongated outer housing assembly during the reversible axial slidable communication.

[0032] In some exemplary embodiments, the chambers are sealed near each end thereof between the outer surface of the elongated inner assembly and the inner surface of the elongated outer housing assembly by sealing rings.

[0033] In some exemplary embodiments, the elongated inner assembly further comprises a detachable distal end portion configured for axial slidable movement with the elongated inner assembly towards the proximal end of the elongated outer housing assembly and in response to a sudden predetermined fluid injection pressure increase, independently towards a predetermined region nearer the distal end of the elongated outer housing lumen for obstructing the one or more fluid ports. [0034] In some exemplary embodiments, the predetermined region nearer the distal end of the elongated outer housing is determined by an outer housing assembly abutting formation against which the detachable distal end portion abuts. In some exemplary embodiments, the detachable distal end portion further comprises a dissolvable ball seat. [0035] Other aspects, features and/or advantages will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES [0036] Several embodiments of the present disclosure will be provided, by way of examples only, with reference to the appended drawings, wherein:

[0037] Figure l is a plan side view of an exemplary configuration of a wellbore system in which the well string staging tool of the present disclosure may be utilized;

[0038] Figure 2 is a perspective view of an exemplary embodiment of the well string staging tool of the present disclosure;

[0039] Figure 3 is a cross-sectional side plan view of the well string staging tool of Figure 2 along line E’-E’;

[0040] Figure 3a is an expanded view of a portion of Figure 3;

[0041] Figure 3b is an expanded view of a portion of Figure 3; [0042] Figure 3c is an expanded view of a portion of Figure 3;

[0043] Figure 3d is an expanded view of a portion of Figure 3;

[0044] Figure 4 is a schematic cross-sectional view of an exemplary embodiment of an aperture of the present disclosure; [0045] Figure 4a is a schematic cross-sectional view of an exemplary embodiment of an aperture of Figure 4 showing fluid entering and exiting a chamber from the inner assembly lumen;

[0046] Figure 4b is a schematic cross-sectional view of an exemplary embodiment of an aperture of Figure 4 showing fluid entering and exiting a chamber from the annular space;

[0047] Figure 5a is a cross-sectional side plan view of the well string staging tool of Figure 2 showing the elongated inner assembly in a fluid port open position;

[0048] Figure 5b is a cross-sectional side plan view of the well string staging tool of Figure 5 showing the elongated inner assembly in a fluid port locked position;

[0049] Figure 6 is a side plan view of the inner assembly proximal component of the well string staging tool of the present disclosure;

[0050] Figure 6a is a schematic plan view of the lug pin travel path of Figure 6;

[0051] Figure 7 is a cross-section plan view along line F’-F’ of Figure 3; [0052] Figure 8a is a side plan view of the lug ring of the well string staging tool of the present disclosure;

[0053] Figure 8b is a side plan view of the lug ring holder of the well string staging tool of the present disclosure;

[0054] Figure 9 is a cross-section plan view along line G’-G’ of Figure 3; and [0055] Figure 10 is an expanded view of a portion of Figure 3.

[0056] Elements in the several figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be emphasized relative to other elements for facilitating understanding of the various presently disclosed embodiments. Also, common, but well-understood elements that are useful or necessary in commercially feasible embodiments are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present disclosure.

DETAILED DESCRIPTION

[0057] Various implementations and aspects of the specification will be described with reference to details discussed below. The following description and drawings are illustrative of the specification and are not to be construed as limiting the specification. Numerous specific details are described to provide a thorough understanding of various implementations of the present specification. However, in certain instances, well-known or conventional details are not described in order to provide a concise discussion of implementations of the present specification.

[0058] Various apparatuses and processes will be described below to provide examples of implementations of the system disclosed herein. No implementation described below limits any claimed implementation and any claimed implementations may cover processes or apparatuses that differ from those described below. The claimed implementations are not limited to apparatuses or processes having all of the features of any one apparatus or process described below or to features common to multiple or all of the apparatuses or processes described below. It is possible that an apparatus or process described below is not an implementation of any claimed subject matter.

[0059] Furthermore, numerous specific details are set forth in order to provide a thorough understanding of the implementations described herein. However, it will be understood by those skilled in the relevant arts that the implementations described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the implementations described herein. [0060] In this specification, elements may be described as“configured to” or“adapted to” perform one or more functions or“configured for” or“adapted for” such functions. In general, an element that is configured to perform or configured for performing a function is enabled to perform the function, or is suitable for performing the function, or is adapted to perform the function, or is operable to perform the function, or is otherwise capable of performing the function.

[0061] In Figure 1, there is shown a general schematic representation of a plan side view of a subterranean well system 100 showing a general exemplary system wherein an embodiment of the well string tool 20 of the present disclosure may be used. Generally, the well system 100 comprises a wellbore 114 which is defined by a wellbore wall 116 drilled in reservoir, generally being of reservoir rock H6a and having a proximal end P’ and a distal end D’. A well string 112 is inserted into the wellbore 112 around which is formed an axially extending annulus or annual space 118 between a wellbore wall 116 and the well string 112. The well string 112, which is generally tubular, may be cemented into the wellbore 114 using the well string staging tool 20 as described herein to complete cementing operations. The well string 112 of the well system 100 generally comprises several additional components as noted herein for an understanding of the presently disclosed well string staging tool 20 which are conventionally used in a multi-stage open hole fluid stimulation operation. Located distal in such operations to the well string staging tool 20 are generally one or more liner packers l lOa, l lOb, l lOc, and l lOd which allow for sectional fluid stimulation and stimulation fluid ports l20a, l20b, and l20c. The stimulation fluid ports l20a, l20b, and l20c may be selectively opened and closed to stimulate hydrocarbon reservoir flow into the annular space 118 distally to the well string staging tool 20. Fluid circulation, as denoted at F, may be set up at the proximal end P’ of the well so that fluid migrates through the well string 112 to the distally located wellbore isolation valve 122 and thus fluid flow into the annulus 118. It should be noted that and understood that during various operations, the well string staging tool 20 and embodiments described herein are not be limited the system 100 arrangement shown in Figure 1. On the contrary, other well system having a requirement for well string cementing operations may be constructed as determined by one of skill in the art. The well string staging tool 20 as described herein may be used in conjunction with several well systems, operational devices and methods.

[0062] Referring now to Figure 2, there is shown a perspective view of the well string staging tool 20 of the present disclosure. The well string staging tool 20 as shown in Figure 2 has an elongated outer housing assembly 22 with proximal end 24 which is adapted for coupling and fluid communication with a downhole portion of the well string 112. Located in the elongated outer housing assembly 22 and through an outer housing wall 38 are one or more second piston apertures 48b which allow fluid communication with corresponding one or more second pistons 60. Additionally, located in the outer housing assembly 22 and through the outer housing wall 38 are one or more fourth piston apertures 48d which allow fluid communication with corresponding one or more fourth pistons 64. The fluid communication of fluids in and out of second pistons 60 and fourth piston 64 is described in more detail below. Also shown in Figure 2 is the distal end 26 of the elongated outer housing assembly 22 which is adapted for coupling and fluid communication with a portion of the well string 112 located in the open hole region of the system 100 where the liner packers l lOa to l lOd, stimulation fluid ports l20a to l20c and wellbore isolation valve 122, as generally shown in Figure 1 and described above, may be located in certain exemplary subterranean well systems 100. The elongated outer housing assembly 22 includes one or more fluid ports 36 which depend through the outer housing assembly wall 38. During use of the well string staging tool 20, the fluid ports 36 provide fluid communication between an outer housing assembly lumen 28 and the annular space 118 so as to allow a fluid injected down the well string 112 as denoted by F of Figure 1, such as wellbore cement, to exit into the annular space 118.

[0063] Figure 3 is a cross-section view of the well string staging tool 20 of the present disclosure along line E’-E’ of Figure 2. Located within the outer housing assembly lumen 28 is an elongated inner assembly 30 having an inner assembly lumen 32 for receiving the fluids, such as wellbore cement, from the well string 112 via the proximal end 24 of the outer housing lumen 28 in fluid communication therewith. The elongated inner assembly 30 is permitted limited reversible axial sliding movement within outer housing assembly lumen 28 along a travel path in response to a predetermined injection pressure of the fluid, as described in further detail below.

[0064] With reference to Figure 3, various chambers 42 are shown and described below. In the embodiment of the well string staging tool 20 shown in the figures and described herein, there are provided various chambers 42 comprising one or more first pistons 52, more or more second pistons 60, one or more third pistons 62, and one or more fourth pistons 64. In some embodiments, the chambers 42 may be sealed about proximal and distal ends thereof by sealing rings 92, which in some embodiments may be provided as O-rings so as to seal the outer surface 44 of the elongated inner assembly 30 against the inner surface 46 of the outer housing assembly 22. The elongated outer housing assembly 22 and the elongated inner assembly 30, in various embodiments disclosed herein may further comprise multiple interlinkable components. For example, the elongated outer housing assembly 22 may comprise an outer housing proximal component 22a, adapted for coupling with the well string 112 as noted above, an outer housing proximal intermediate component 22b distally coupled to the outer housing proximal component 22a, an outer housing distal intermediate component 22c distally coupled to the outer housing proximal intermediate component 22c, and an outer housing distal component 22d distally coupled to the outer housing distal intermediate component 22c. Additionally, for example, the elongated inner assembly 30 may comprise an inner assembly proximal component 30a, an inner assembly intermediate component 30b distally coupled to the inner assembly proximal component 30a, and an inner assembly distal component 30c distally coupled to the inner assembly intermediate component 30b. Furthermore, each of the elongated outer housing assembly 22 and inner assembly 30 components may include wall profiles, which, when assembled into the well string staging tool as described herein form walls to the various pistons or chambers 42 as described below in certain embodiments. With regard to the various components formed to complete the outer housing assembly 22 or inner assembly, 30, the components may be interlinked by interlinking profiles and/or one or more set screws 94.

[0065] As shown in Figure 3a, in an initial position A (also shown in Figure 3), located near the distal end 24, the one or more first pistons 52 are defined by a chamber 42 bordered by a first piston proximal wall 52a located on a portion of the inner assembly outer surface 44 of the inner assembly distal component 30c, a first piston distal wall 52b located on a portion of the outer housing assembly outer surface 44 of the outer housing distal component 22d, a first piston outer wall 52c located on a portion of an outer housing inner surface 44 of the outer housing distal intermediate component 22c, and a first piston inner wall 52d located on a portion of the inner assembly outer surface 44 of the inner assembly distal component 30c. The first piston 52 is in fluid communication with the inner assembly lumen 32 via a first piston aperture 48a which depends through an inner assembly wall portion 40 so as to allow the ingress of fluid into the first piston 52. Initially, a burst disc 54, which is provided to inhibit the ingress of fluid into the first piston 52, seals the first piston aperture 48a such that fluid cannot enter the first piston until a predetermined fluid pressure in the inner assembly lumen 32 is reached. Once the fluid pressure in the inner assembly lumen is reached by the injection of a fluid down the well string 112, the burst disc 54 is ruptured and fluid is allowed to pass through the first piston aperture 48a into the first piston. [0066] When the elongated inner assembly 30 is located in the initial position A in the outer housing assembly lumen 28, the relative position of the elongated outer housing assembly 22 and the elongated inner assembly 30 is maintained by one or more shear pins 56. In the embodiment of the well string staging tool 20 shown in the figures, the shear pins 56 are shown as being depending through a portion of the outer housing assembly wall 38 near the proximal end 26 into a portion of the inner assembly wall 40, also located nearer the proximal end 26 thereof. However, one of the skill in the art will appreciate that the location and configuration of the one or more shear pins 56 to maintain the relative position of the elongated outer housing assembly 22 and the elongated inner assembly 30 in the initial position A may be changed as desired and as may be required in certain applications and configurations of the well string staging tool 20.

[0067] Turning now to the use of the well string staging tool 20, when a fluid is inj ected down the well string 112, it passes into a proximal portion of the outer housing lumen 28 and further into the inner assembly lumen 32. Once the injection pressure of the fluid is increased to a predetermined desired level, the one or more burst discs 54 are ruptured, and fluid is this permitted to enter the first piston 52 via the corresponding first piston aperture 48a. It should be noted that one of skill art will may determine the appropriate burst discs and shear pin strength required for a given well completion operation. Accordingly, the burst discs and shear pines required for a given application may be installed for the specific characteristics required for a given well completion. [0068] As the injection pressure of the fluid is maintained or, in some embodiments increased or slightly decreased, the flow of fluid into the first piston 52 causes the elongated inner assembly 30 to axially slide towards the proximal end 24 relative to the elongated outer housing assembly 22 and within the outer housing assembly lumen 28. As the elongated inner assembly 30 begins to slide, should a sufficient injection pressure be applied to the fluid, the one or more shear pins 56 are broken and the elongated inner assembly 30 is free to slide along a predetermined travel path 34 relative to and within the outer housing lumen 28.

[0069] With reference to Figure 3b, the second piston aperture 48b, as noted above, allows fluid communication between the annular space 118 and chamber 42, herein as communicating with the second piston aperture 48b, termed the second piston 60. In various embodiments, there may be provided one or more second pistons 60 bordered by a second piston proximal wall 60a located on a portion of the outer assembly inner surface 46 of the outer housing assembly proximal intermediate component 22b, a second piston distal wall 60b located on a portion of the inner assembly outer surface 44 of the inner assembly intermediate component 30b, a second piston outer wall 60c located on a portion of an outer housing inner surface 44 of the outer housing distal intermediate component 22c and a second piston inner wall 60d located on a portion of the inner assembly outer surface 44 of inner assembly intermediate component 30b. [0070] With reference to Figure 3c, a third piston aperture 48c, allows fluid communication between the inner assembly lumen 32 and chamber 42, herein as communicating with the third piston aperture 48c, termed the third piston 62. In various embodiments, there may be provided one or more third pistons 62 bordered by a third piston proximal wall 62a located on a portion of the inner assembly inner surface 44 of the assembly proximal component 30a, a third piston distal wall 60b located on a portion of the outer housing assembly outer surface 46 of the outer housing assembly proximal intermediate component 22b, a third piston outer wall 62c located on a portion of an outer housing inner surface 44 of the outer housing proximal intermediate component 22b and a third piston inner wall 62d located on a portion of the inner assembly outer surface 44 of inner assembly intermediate component 30b. [0071] With reference to Figure 3d, the fourth piston aperture 48d, as noted above, allows fluid communication between the annular space 118 and chamber 42, herein as communicating with the fourth piston aperture 48d, termed the fourth piston 64. In various embodiments, there may be provided one or more fourth pistons 64 bordered by a fourth piston proximal wall 64a located on a portion of the outer assembly inner surface 46 of the outer housing assembly proximal component 22a, a fourth piston distal wall 64b located on a portion of the inner assembly outer surface 44 of the inner assembly proximal component 30a, a fourth piston outer wall 64c located on a portion of an outer housing inner surface 44 of the outer housing proximal intermediate component 22b and a fourth piston inner wall 64d located on a portion of the inner assembly outer surface 44 of inner assembly proximal component 30a.

[0072] Figure 4 shows a schematic side view of an exemplary embodiment of the apertures 48 disclosed herein which allow the flow of fluid in and out of the various chambers 42 or, more specifically the one or more first pistons 52, the one or more second pistons 60, the one or more third pistons 62 and/or the one or more fourth pistons 64. In general, the aperture is formed through a wall of the various components of the elongated outer housing assembly 22 and/or the elongated inner assembly 30, as discussed above and herein so as to allow the passage of fluid in and out of the chambers 42 as shown by the directional arrows. In order that debris and fine particulate matter is substantially impeded form entering the chambers 42 where they may clog the chambers 42 and or interfere with the various moving components machined tolerances, a screening 50 or mesh 50 or particulate filter 50 is provided across the aperture 48. The screening 50 may be selected by user to be of a suitable mesh size so as to correspond with the expected and determined debris or particulate matter size which may be carried in the injection fluid, such as cement or drilling muds, and/or present in the annular space 118 of the wellbore 114. For example, a mesh size of from about 20 to 100 microns, is generally provided. However, other mesh sizes may be selected as required by a person of skill in the art. As shown in the Figure 4, the aperture 48 is formed through a wall and has a shoulder portion 53 on which the screening 50 is placed. In some embodiments, the screening may be held in place by an epoxy or glue. However, in the embodiment shown herein the screening 50 is maintained in place in the aperture 48 by a hollow retaining nut 51 threadably engaged with a portion of the aperture wall such that the screening 50 is sandwiched between the shoulder portion 53 and the hollow retaining nut 51. Fluid is thus allowed to pass through the hollow retaining nut 51 and screening 50 into and out of the chamber 42 while debris and particulate matter is substantially blocked from entering the chamber 42 by way of the screening 50.

[0073] Turning now to Figures 4a and 4b, exemplary fluid flows are shown with respect to the apertures 48. For example, in Figure 4a, there is schematically shown the flow of fluid into a chamber 42, such as the one or more first pistons 52 and the one or more third pistons 62. When the injection pressure of a fluid being provided to the inner assembly lumen 32 is sufficient so as to cause fluid to enter the first piston 52 and third piston 62 via respective apertures 48, the pistons axially expand thus causing axial sliding movement of the elongated inner assembly 30 within the outer housing assembly lumen 28 and relative thereto in direction of P\ As this happens, with reference to Figure 4b, fluid within the one or more second pistons 60 and the one or more fourth pistons 64 exits into the annual space 118 as the one or more second pistons 60 and the one or more fourth pistons 64 axial contract. Conversely, if the pressure within the annular space 118 is equal to or greater than the fluid pressure within the inner assembly lumen 32, fluid enters the one or more second pistons 60 and the one or more fourth pistons 64 and these pistons axially expand while the one or more first pistons 52 and the one or more third pistons 62 axially contract and the elongated inner assembly 30 is thus caused to axially slide within the elongated outer housing assembly 22 and relative thereto in the direction of D’. Furthermore, as shown in Figure 3b, in some embodiments, there is a biasing means 58 provided in the chamber 42 defining the second piston 60. The biasing means 58, which in some embodiments may take the form of a spring is provided to bias the elongated inner assembly 30 in the direction of D’. Therefore, for example, if the pressure in the annular space 118 and the pressure in the inner assembly 32 is approximately equal, the biasing means 58 will cause or assist the inner assembly 30 to axially slide within the outer housing assembly lumen 28 in the direction of D’ and return to near the initial position A. However, it should be noted that in some embodiments, not shown, the biasing means may not be required or may take another form such as a separate gas pressurized chamber suitably provided in the well string staging 20 so as to cause the elongated inner assembly 30 to return to near the initial position A when insufficient fluid injection pressure is provided within inner assembly lumen 32. Therefore, by increasing the injection pressure of a fluid, which may, in some embodiments be a cementing fluid, the elongated inner assembly 30 is caused to axially travel within the outer housing assembly lumen 28 and relative to the elongated outer housing assembly 22 along a predefined travel path 34 in the direction of P’ by fluid entering the one or more first pistons 52 and the one or more third pistons 62. When the fluid injection pressure is decreased, the elongated inner assembly 30 is biased along the predefined travel path 34 to travel in the direction of D’ and/or by the ingress of fluid from the annular space 118 into the one or more second pistons 60 and the one or more fourth pistons 64 having a greater pressure than that of the pressure of the fluid provided down the well string 112. The predefined travel path 34 is discussed in more detail below.

[0074] Having now described the fluid flows with respect to the various apertures 48 and chambers 42 in response to varying the fluid injection pressure provided down the well string 112, the one or more first piston 52 is discussed in relation to Figure 5. As noted above, initially the elongated inner assembly 30 is maintained in the initial position A by shear pins 56. Once a fluid injection pressure provided down the well string 112 is sufficient to cause burst discs 54 to rupture, fluid is permitted to enter the one or more first pistons 52. This causes the one or more first pistons 52 to axially expand and the shear pins 56 to break, allowing the elongated inner assembly 30 to travel in the outer housing assembly lumen 28 in the direction of P’. Once the shear pins 56 have released purchase on the elongated inner assembly 30, fluid flowing into the one or more first pistons 52 and the one or more third pistons 62 causes the axial sliding movement of the elongated inner assembly 30 against the bias of the biasing means 58, and the chamber of the first piston 52 is exposed to the outer housing assembly lumen 28. As the interior of the one or more pistons 52 is exposed to the outer housing assembly lumen 28, the inner assembly distal component 30a is thus moved along the travel path 34 such that the inner assembly distal component 30a unobstructs the fluid ports 36 located and depending through the outer housing assembly wall 38 in the outer housing assembly distal intermediate component 22c. This thereby allows injected fluid, such as cement to enter into the annular space 118 where the elongated inner assembly 30 is in a fluid port 36 port open position B, as shown in Figure 5. Figure 5b shows the elongated inner assembly 30 in the port lock position C where the fluid ports 36 are again obstructed from allowing fluid to exit therethrough. In order to better illustrate the axially sliding movement in response to increasing fluid injection pressure so as to shift the elongated inner assembly 30 in direction of P’, Figure 5 notes distance B’ as measured from the proximal end 24 of the elongated outer housing assembly 22 and the proximal end of the elongated inner assembly 30 when in the fluid port 36 open position B. Whereas Figure 5b notes the increased distance C’ relative to distance B’ of Figure 5, similarly measured, when the fluid injection pressure is decreased and the elongated inner assembly 30 is caused to axially slide within the outer housing assembly lumen 28 in the direction of D’ to the fluid port 36 port locked position C where the fluid ports 36 are obstructed from permitting the passage of fluid therethrough into the annular space 118. Port locked position C is slightly more in the direction of D’ as compared to the initial position A and distance A’ of Figure 3 as defined by the travel 34, discussed in more detailed below. [0075] The fluid ports 36, as noted above, are provided for allowing the fluid injected down the well string 112 into the well string staging tool 20 to exit into the annular space 118 and thus, in some embodiments cement the well string 112 in place within the wellbore 114. Although the fluid ports 36 may be provided as openings of various shapes and configurations as determined by the requirements of a given cementing operation by one of skill in the art, in preferred embodiments, such as shown in Figure 2, the fluid ports 36 may be provided as elongated openings. Furthermore, in preferred embodiments, the fluid ports 36 are provided as elongate openings made through the outer housing assembly wall 38 at an angle relative to the central axis 10 of the well string staging tool 20. By providing the fluid port 36 at an angle, it has been surprisingly discovered that the fluid exiting the fluid port 36 better enters the annular space and flow thereof is improved for cementing the well string 112 in place.

[0076] Turning now the travel path 34 of the elongated inner assembly 30 within the outer housing assembly lumen 28, the travel path is defined by a recessed profile 66 milled into the inner assembly outer surface 44, which in the embodiments described herein is provided on the inner assembly proximal component 30a, as shown, for example in Figure 6. A lug pin 70 is coupled to the outer housing inner surface 46 and slidingly engages with the recessed profile 66. In some embodiments, the lug pin 70 may be coupled by intervening components. The lug pin 70, as the elongated inner assembly 30 is caused to axially slide within the outer housing lumen 28, slides within the recessed profile 66 and limits the displacement of the elongated inner assembly 30 within the outer housing lumen 28 along the travel path. In some embodiments, there may be provided more than one recessed profiles 66, each with a corresponding and cooperating lug pin 70.

[0077] With reference to Figure 6, the recessed profile 66 may be provided, in some exemplary embodiments as a plurality of interconnecting J-slots, where an exemplary travel path 34 pattern is shown in Figure 6a. When the elongated inner assembly 30 is in the initial position A, as discussed above, the lug pin 70 is located in the J-slot starting zone 78A. As the elongated inner assembly 30 axially slides, once the shear pins 56 are broken under an increased fluid injection pressure, the lug pin 70 is moved relative to the outer assembly proximal component 22a into a longitudinally extending portion 78B of one of the interconnected the J-slots. When the fluid injection pressure is sufficiently decreased and the elongated inner assembly 30 is biased towards the initial position A, lug pin 70 is moved relative to the inner assembly proximal component 30a into a near initial position portion 78C of the interconnected J-slots. When the fluid injection pressure is again increase to overcome the bias, the lug pin 70, owing to the shape of the recessed profile 66 interconnected plurality of J-slots, is advanced to the next longitudinally extending portion 78B, as shown in Figure 6. Owing to the recessed profile 66 J-slot shape, the lug pin 70 is only permitted to advance to the next longitudinally extending portion 78B of the recessed profile 66 and not return to a previously utilized longitudinally extending portion 78B. The lug pin 70 advances through the travel path 34 of the recessed profile under sufficiently increased fluid injection pressure to overcome the bias and sufficiently decreased fluid injection pressures cycles until it is located in the J-slot fluid port locked zone 78D.

[0078] Figure 7 is a cross-sectional view along line F’-F’ of Figure 3 showing an exemplary embodiment and configuration of the outer housing assembly proximal component 22b, the inner assembly proximal component 30a and intervening components. In the embodiment shown in Figure 7, the lug pins 70 are coupled to a lug ring 76 which circumferentially encases a portion of the inner assembly proximal component 30a and is maintained in place by a lug rug holder 72. The lug ring holder 72 is fixed in position relative to the elongated outer housing assembly 22 by suitable means. For example, in the embodiment shown in Figure 7, the lug ring holder 72 is coupled to the housing proximal component by a set screw thereby maintaining the lug ring 76 and thus the lug pins in a fixed position relative to outer housing assembly inner surface 46. Yet, in operation of the well string staging tool 20, the relative position of the lug ring 76 and the lug pins 70 is allowed to change relative to the elongated inner assembly 30 as the lug pins 70 advance through the recessed profile 66 in response to increasing and decreasing fluid injection pressures.

[0079] Building on the description above of the interaction of the lug pin 70, the lug ring 76 and the lug ring holder 72, Figure 8a shows a side profile view of the lug ring 76 and the lug pin 70. Figure 8b shows a side profile of the lug ring holder 72. The lug ring holder 72 has an elongate slot 74 through which, when assembled in the well string staging tool 20 as discussed above with respect to Figure 7 and shown in the cross-sectional view of Figure 3, the lug pin 70 depends through for engagement with the recessed profile 66. As the lug pin 70 advances along the travel path 34 defined by the recessed profile 66, the lug ring 76, and thus the lug pin 70, rotate relative to the fixed-in-position lug ring holder 72 such that lug pin 70 travels circumferentially in the elongate slot 74. This allows the lug pin 70 to move through the recessed profile 66 milled into the outer surface 46 of the inner assembly proximal component 30a from the J-slot starting zone 78A, through the interconnected longitudinally extending portions 78B and finally into the J-slot fluid port locked zone 78D in response to cycles of increasing and decreasing fluid injection pressures. Once the lug pin 70 is located in the J-slot fluid port locked 78D, the inner assembly distal portion 30c is abutted against abutting formation 86 formed on an inner surface of the outer housing distal component 22d and maintained in place by permanent locking means (not shown). The permanent locking means may take the form, for example, of irreversibly cooperating ratcheting surfaces located on the outer surface of the inner assembly distal component 30s and the inner surface of the outer housing distal component 22d. [0080] The lug ring 76 and coupled lug pin 70, as noted above, is permitted to circumferentially rotate relative to the elongated inner assembly 30 and the elongated outer housing assembly 22 as the lug pin 70 advances along the travel path 34. However, the elongated inner assembly 30 and the elongated outer housing assembly 22 are permitted to only move relative to each other in response to increasing and decreasing fluid injection pressures along a limited axial sliding travel path 34; the limited axial sliding travel path 34 being defined by the recessed profile 66 and lug pin 70 interaction. In order to prevent rotation of the inner assembly proximal component 30a relative to the outer housing proximal component 22a, complementary anti-rotation formations are provided on the outer housing inner surface 46 and inner assembly outer surface 44. In the embodiment described herein and shown in the figures, these anti-rotation formations are provided on the outer housing proximal component 22a and the inner assembly proximal component 30a. However, one of skill in the art may determine that such anti -rotation formations may be provided, as required in certain applications elsewhere on the well string staging tool 20 such that the elongated outer housing assembly 22 and the elongated inner assembly 30 are maintained in relative non-rotational communication and permitted only relative axial displacement. Figure 9 is a cross-sectional view along line G’-G’ of Figure 3 which shows an exemplary embodiment of the anti -rotational formations. For example, one or more anti-rotation pins 80 may be provided as depending through the outer housing assembly wall 38 and being received into corresponding and complementary elongate anti -rotation pin recessed profiles 82 longitudinally milled into the inner assembly proximal component 30a outer surface 44.

[0081] In some embodiments the inner assembly distal component 30c has an exterior profile located near the proximal end thereof which detachably links with an exterior profile of the distal end of the inner assembly intermediate component 30b thereby providing a linking assembly 96 as shown in Figure 10. During normal operation of the well string staging tool 20, the elongated inner assembly 30 moves axially along the travel path 34, as discussed above. However, should it be required, for example in an emergency situation, to rapidly obstruct the fluid ports 36 so as to stop fluid from entering the annual space 118, the inner assembly distal component 30c can be rapidly detached from the inner assembly intermediate component 30b and axially displaced towards the distal end 26 in the direction of D\ In such a situation, the inner assembly distal component 30c, is termed a detachable distal end portion 84. The linking assembly 96, in certain embodiments, is responsive to a sudden increase in fluid injection pressures. For example, such a sudden increase in fluid injection pressure over a normal, in other words, predetermined injection pressure causes the detachable distal end portion 84 to detach from the inner assembly intermediate component 30b and axially slide towards D’ and stop in a predetermined position near the distal end of the outer housing lumen 28. In the embodiment shown in the figures, the predetermined position near the distal end of the outer housing lumen 28 is provided by an abutting formation 86 formed on an inner surface of the outer housing distal component 22d against which the distal end of the detachable distal end portion 84 abuts and is not permitted to axially slide further towards D’ thereby obstructing fluid ports 36 from allowing further fluid to exit. In some embodiments a permanent locking means may be provided so as to permanently lock the detachable end portion 84 in fluid port locked position in the outer housing assembly lumen 32. Located proximal to the detachable distal end portion 84 within the inner assembly lumen 32, in some embodiments, is provided a dissolvable ball seat 90, as shown, for example in Figures 3 and 10. The dissolvable ball seat 90 abuts the detachable distal end portion 84 at proximal end thereof and has a pressure actuatable surface 98 against which the sudden increase in fluid injection pressure, or in some embodiments (not shown) an object sent down the well string, acts to force the linking assembly 96 to detach and thus sever the detachable distal end portion 84 from the elongated inner assembly 30 in order to obstruct the fluid ports 36. In normal operation, once the lug pins 70 have cycled through the recessed profile 66 and are maintained in the J-slot fluid port locked zone 78D such that the fluid ports 36 are reversibly obstructed, the dissolvable ball seat 90, owing to its construction material, dissolves in the salinity of the injection fluid or cement and thus the fluid ports are permanently obstructed.

[0082] While the present disclosure describes various embodiments for illustrative purposes, such description is not intended to be limited to such embodiments. On the contrary, the applicant's teachings described and illustrated herein encompass various alternatives, modifications, and equivalents, without departing from the embodiments, the general scope of which is defined in the appended claims. Except to the extent necessary or inherent in the processes themselves, no particular order to steps or stages of methods or processes described in this disclosure is intended or implied. In many cases the order of process steps may be varied without changing the purpose, effect, or import of the methods described.

[0083] Information as herein shown and described in detail is fully capable of attaining the above-described object of the present disclosure, the presently preferred embodiment of the present disclosure, and is, thus, representative of the subject matter which is broadly contemplated by the present disclosure. The scope of the present disclosure fully encompasses other embodiments which may become apparent to those skilled in the art, and is to be limited, accordingly, by nothing other than the appended claims, wherein any reference to an element being made in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more." All structural and functional equivalents to the elements of the above-described preferred embodiment and additional embodiments as regarded by those of ordinary skill in the art are hereby expressly incorporated by reference and are intended to be encompassed by the present claims. Moreover, no requirement exists for a system or method to address each and every problem sought to be resolved by the present disclosure, for such to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. However, that various changes and modifications in form, material, work-piece, and fabrication material detail may be made, without departing from the spirit and scope of the present disclosure, as set forth in the appended claims, as may be apparent to those of ordinary skill in the art, are also encompassed by the disclosure.

Claims

CLAIMS What is claimed is:

1. A well string staging tool for delivering a fluid to a desired zone within a wellbore comprising:

an elongated outer housing assembly having a proximal end and a distal end and being adapted near said proximal end thereof for coupling and fluid communication with a downhole portion of a well string and having an outer housing assembly lumen;

an elongated inner assembly having an inner assembly lumen in fluid communication with a portion of said outer housing assembly lumen for receiving fluid from said well string and configured for reversible axial slidable communication within the outer housing assembly lumen along a predefined travel path in response injection pressures of said fluid; said elongated outer housing assembly having one or more fluid ports through a wall thereof for allowing said fluid to exit said outer housing assembly lumen which are obstructed by a wall portion of the elongated inner assembly when said elongated inner assembly is an initial position; said elongated inner assembly being displaceable from said initial position along said travel path in response to increases and decreases of said injection pressure of said fluid relative to an annular space fluid pressure so as to unobstruct said one or more fluid ports and selectively allow egress of said fluid into said annular space between the elongated outer housing assembly and a wellbore wall;

one or more chambers defined between an outer surface of the elongated inner assembly and an inner surface of the elongated outer housing assembly; a portion of said chambers forming one or more pistons, each of said pistons having an aperture for allowing fluid transfer between said inner assembly lumen or said annular space; and said apertures having a screening of a mesh size suitable for inhibiting the ingress particulate matter into each of said one or more pistons.

2. The well string staging tool as defined in claim 1, wherein a portion of said pistons comprises a first piston located near said distal end of said well string staging tool; said first piston including at least one first piston aperture operable to allow the passage of fluid from interior said elongated inner assembly lumen into said first piston, wherein under increased injection fluid pressure relative said annular space pressure causes said first piston to expand and said elongated inner assembly to travel along said travel path towards said proximal end and said one or more fluid ports to open.

3. The well string staging tool as defined in claim 2, wherein said first piston aperture includes a pressure responsive burst disc for initially sealing across said first piston aperture so as to obstruct fluid flow from interior said inner assembly lumen into said first piston when said inner assembly is in said initial position and to rupture in response to a predetermined injection fluid pressure so as to allow the passage of fluid into said first piston.

4. The well string staging tool as defined in any one of claims 1 to 3, further comprising one or more shear pins for maintaining said elongated inner assembly in said initial position; said shear pins responsive to a predetermined axial sliding force acting on said elongated inner assembly so as to cause axial sliding displacement of said elongated inner assembly relative said elongated outer housing assembly.

5. The well string staging tool as defined in any one of claims 1 to 4, wherein when said elongated inner assembly is axially displaced within said outer housing lumen in response to increased fluid injection pressure, said elongated inner housing assembly slides and an interior of said first piston is exposed to said elongated outer housing lumen.

6. The well string staging tool as defined in any one of claims 1 to 5, further comprising one or more biasing means configured bias to said elongated inner assembly toward initial position.

7. The well string staging tool as defined in claim 6, wherein said biasing means are disposed in at least one of said chambers.

8. The well string staging tool as defined in any one of claims 1 to 7, wherein said at least one chamber in which said biasing means is disposed comprises a second piston located between said proximal end and said distal end of said well string staging tool; said second piston including at least one second piston aperture operable to allow the passage of fluid from said annular space into second piston when said annular space fluid pressure is greater than said fluid injection pressure and causes said second piston to expand and said elongated inner assembly to return to near said initial position along said travel path.

9. The well string staging tool as defined in any one of claims 1 to 8, wherein a portion of said pistons comprises a third piston located between said proximal end and said distal end of said well string staging tool; said third piston including least one third piston aperture operable to allow the passage of fluid from interior said elongated inner assembly lumen into said third piston, wherein under increased injection fluid pressure relative said annular space fluid pressure causes said third piston to expand and said elongated inner assembly to travel along said travel path towards said proximal end and said one or more fluid ports to open.

10. The well string staging tool as defined in any one of claims 1 to 9, wherein a portion of said pistons comprises a fourth piston located between said proximal end and said distal end of said well string staging tool; said fourth piston including at least one fourth piston aperture operable to allow the passage of fluid from said annular space into fourth piston when said annular space fluid pressure is greater than said fluid injection pressure and causes said fourth piston to expand and said elongated inner assembly to return to near said initial position along said travel path.

11. The well string staging tool as defined in any one of claims 1 to 10, wherein said one or more fluid ports are provided at an angle relative a central longitudinal axis of the well string staging tool.

12 The well string staging tool as defined in any one of claims 1 to 11, wherein said travel path is defined by a longitudinally extending recessed profile on said outer surface of the elongated inner assembly engageable by a lug pin coupled to said an inner surface of said elongated outer housing assembly; said lug pin being is displaceable in said recessed profile.

13. The well string staging tool as defined in claim 12, further comprising a lug ring holder circumferentially encasing to a portion of the elongated inner assembly and fixed in position relative to a portion of the inner surface of the elongated outer housing assembly; said lug ring holder having an elongate slot for receiving therethrough a portion of said lug pin for travel in said recessed profile.

14. The well string staging tool as defined in claim 13, further comprising a lug ring circumferentially encasing a portion of the elongate inner assembly having coupled thereto said lug pin wherein said lug depends through said elongate slot for engageable communication with said recess profile.

15. The well string staging tool as defined in claim 14, wherein said lug pin is further circumferentially displaceable in said elongate slot.

16. The well string staging tool as defined in any one of claims 10 to 15, wherein said recessed profile is a provided as a J-slot profile and wherein said lug pin is maintained in a starting zone when said elongated inner assembly is in said initial position and when said elongated inner assembly is displaced under increased fluid injection pressure, said lug pin advances to a longitudinally extending portion of said J-slot where said one or more fluid ports are unobstructed and when said fluid injection pressure is decreased to where said elongated inner assembly returns to near said initial position, said lug pin advances to a working sequential zone in said recessed profile where said one or more fluid ports are obstructed.

17. The well string staging tool as defined in claim 16, wherein said J-slot profile comprises a repeating pattern which repeats a predetermined number of times, each repetition being interconnected and said pattern terminating at a fluid port obstructed lock-out zone.

18. The well string staging tool as defined in any one of claims 1 to 17, said outer surface of said elongated inner assembly and said inner surface of the elongated outer housing assembly further comprising complementary formations for inhibiting rotation of said elongated inner assembly relative said elongated outer housing assembly during said reversible axial slidable communication.

19. The well string staging tool as defined in any one of claims 1 to 18, wherein said chambers are sealed near each end thereof between said outer surface of said elongated inner assembly and said inner surface of the elongated outer housing assembly by sealing rings.

20. The well string staging tool as defined in any one of claims 1 to 19, said

elongated inner assembly further comprising a detachable distal end portion configured for axial slidable movement with said elongated inner assembly towards said proximal end of said elongated outer housing assembly and in response to a sudden predetermined fluid injection pressure increase, independently towards a predetermined region nearer said distal end of said elongated outer housing lumen for obstructing said one or more fluid ports.

21 The well string staging tool as defined in claim 20, wherein said

predetermined region nearer said distal end of said elongated outer housing is determined by an outer housing assembly abutting formation against which said detachable distal end portion abuts.

22. The well string staging tool as defined in claim 20, wherein detachable distal end portion further comprises a dissolvable ball seat.