Abstract:
The present invention relates to a pressure actuated valve for use in well completion assemblies. The valve is operable by pressure between three configurations. In a first configuration, the valve is in a locked-closed configuration. In a second configuration, the valve remains closed but is unlocked. In a third configuration, the valve is open. Also disclosed is a method of installing and operating a three pressure actuated valve in a well completion operation.

Description:
REFERENCE TO PRIOR APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 60/097,449, filed Aug. 21, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to the field of well completion assemblies for use in a wellbore. More particularly, the invention provides an improved pressure actuated valve for production zone isolation. 
     The present invention provides an isolation sleeve assembly which may be installed inside a production screen and thereafter controlled by generating a pressure differential between the valve interior and exterior. In contrast, prior systems required the use of a service string, wire line, coil tubing, or other implement to control the configuration of the isolation valves. Utilization of such systems involves positioning of tools down-hole. Each trip into the wellbore adds additional expense to the well owner and increases the possibility that tools may become lost in the wellbore requiring still further operations for their retrieval. 
     While pressure actuated valves have been used in certain situations, disadvantages have been identified with such devices. For example, prior pressure actuated valves had only a closed position and an open position. Thus, systems could not reliably use more than one such valve, since the pressure differential utilized to shift the first valve from the closed position to the open would be lost once the first valve was opened. Therefore, there could be no assurance all valves in a system would open. 
     There has therefore remained a need for an isolation system for well control purposes and for wellbore fluid loss control, which combines simplicity, reliability, safety and economy, while also affording flexibility in use. The present invention satisfies this need, providing an isolation system which does not require tools to shift the valve and allows the use of multiple pressure actuated valves in a production assembly. 
     SUMMARY OF THE INVENTION 
     Briefly describing one aspect of the present invention, there is provided an isolation assembly which comprises a production string having an interior annulus and an exterior. The production string includes at least one aperture providing fluid communication between the exterior and the interior annulus. Further, a pressure actuated valve is disposed adjacent the aperture. The valve is shiftable by changes in pressure between a locked-closed configuration, an unlocked-closed configuration and an open configuration. In a preferred embodiment, the valve assembly further includes a mechanism for biasing the valve into the open configuration after it has been shifted to the unlocked-closed configuration. In still a further aspect of a preferred embodiment, the valve assembly includes inner and outer sleeves axially displaceable by the generation of a pressure differential between the interior of the production tubing and the exterior. In a preferred embodiment, the inner and outer sleeves define a chamber for transferring a pressure differential into a force acting along the longitudinal axis to urge axial displacement of one sleeve with respect to the other. 
     The present invention further contemplates the use of a plurality of valves according to the present invention within a single screen assembly and that there may be multiple screen assemblies. Also, if desired to reduce costs of an assembly, a single dump valve having only an open and closed position may be combined with valves of the present design. In such an assembly the pressure differential required to shift the valves from the locked-closed configuration to the unlocked-closed configuration would be less than the pressure required to shift the dump valve to the open position. 
     Further, valves of the present design may be used in conjunction with known gravel packing and isolation systems. In this manner, gravel packing the formation may be conducted in a standard manner and the formation isolated. Once this is completed, the formation may be brought on-line without running tools back into the wellbore simply by pressuring up the interior of the tubing to open any number of valves according to the present invention. 
     The present invention further contemplates a method of inserting production tubing, comprising providing a production tubing assembly including a screen, and a pressure actuated isolation valve disposed adjacent the screen. The assembly is inserted into a wellbore until the screen and isolation valve are disposed adjacent a production zone. In a preferred embodiment the isolation valve is initially in a closed configuration, however, it is contemplated that the valve may be manipulated into such a configuration after placement. When desired, a pressure differential is created between the exterior of the production tubing and the interior, the pressure differential tends to shift the pressure actuated valve from a locked-closed configuration to an unlocked-closed configuration. Thus, in the first valve shifting operation the valve stays in a continuously closed state. In a preferred embodiment, the pressure in the tubing is initially increased with respect to the pressure surrounding the production assembly to move the valve to an unlocked, yet closed configuration. Once unlocked, the pressure differential is decreased to allow the valve to move to an open configuration to permit fluid flow through the production screen. In multiple zone completions, the method may preferably include passing a further production tubing string through the isolation valve to reach a lower production zone. It will be understood that the pressure actuated valve of the present invention may be actuated with such a second production tubing in place in the wellbore. 
     It is an object of the present invention to provide a versatile isolation system that combines simplicity, reliability, safety, and economy with optional methods of operation. 
     Another object of the present invention is to provide an isolation valve that may be shifted without the use of tools inserted into the wellbore. 
     Still another object of the present invention is to provide an isolation system that may be permanently installed inside the production screen at the surface prior to running into the well. 
     Yet a further object of the present invention is to provide a pressure actuated valve that may be used in conjunction with a plurality of similar valves to provide reliable shifting of all valves simultaneously. 
     It is a further object to provide an isolation system which is simpler to install and operate, and which provides immediate access to a zone of interest. 
     According to one aspect of the invention, there is provided a valve for a production assembly for the production of minerals from a well, the valve having a tube having at least one opening; a sleeve having at least one other opening and being movably connected to the tube, wherein the tube and sleeve are configurable in at least locked-closed, unlocked-closed and open configurations, wherein the at least one opening and the at least one other opening are adjacent in the open configuration and nonadjacent in the locked-closed and unlocked-closed configurations; and a chamber between the tube and the sleeve, wherein a pressure within the chamber unlocks the lock and configures the tube and sleeve between the locked-closed and unlocked-closed configurations. 
     According to a further aspect of the invention, there is provided a valve for a production assembly for the production of minerals from a well, the valve having: a tube having at least one hole; a sleeve, wherein the sleeve and tube are configurable between at least locked-closed, unlocked-closed and open configurations, wherein the sleeve shuts the at least one hole in the locked-closed and unlocked-closed configurations and the sleeve opens the at least one hole in the open configuration; and a pressure activated control mechanism. 
     According to still another aspect of the invention, there is provided a production assembly for producing mineral from a production zone, the assembly having: a production string; a production screen; a valve having: a tube having at least one hole; a sleeve, wherein the tube and sleeve are configurable between at least locked-closed, unlocked-closed and open configurations, wherein the sleeve shuts the at least one hole in the locked-closed and unlocked-closed configurations and the sleeve opens the at least one hole in the open configuration; and a pressure activated control mechanism. 
     According to another aspect of the invention, there is provided a method for producing mineral from a production zone, the method having the steps of: placing a production assembly adjacent the production zone, wherein the production assembly having: a production pipe; a production valve comprising: a tube having at least one hole; a sleeve, wherein the tube and sleeve are configurable between at least locked-closed, unlocked-closed and open configurations, wherein the sleeve shuts the at least one hole in the locked-closed and unlocked-closed configurations and the sleeve opens the at least one hole in the open configuration; and a pressure activated control mechanism which reconfigures the sleeve and tube between the locked-closed configuration and the unlocked-closed configuration; inducing a pressure differential between an interior of the production assembly and an exterior of the production assembly, wherein the pressure differential is sufficient to activate the pressure activated control mechanism. 
     Further objects and advantages of the present invention will be apparent from the description of the preferred embodiment which follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is better understood by reading the following description of non-limitative embodiments with reference to the attached drawings wherein like parts in each of the several figures are identified by the same reference characters, and which are briefly described as follows. 
     FIGS. 1 ( a ) through ( d ) are a side, partial cross-sectional, diagrammatic view of half of a production tubing assembly in accordance with the present invention in a locked-closed configuration. It will be understood that the cross-sectional view of the other half of the production tubing assembly is a mirror image taken along the longitudinal axis. 
     FIGS. 2 ( a ) through ( d ) illustrate the isolation system of FIG. 1 in an unlocked-closed configuration. 
     FIGS. 3 ( a ) through ( d ) illustrate the isolation system of FIG. 2 in an open configuration. 
     FIG. 4 is a cross-sectional, diagrammatic view taken along line A—A of FIG.  3 ( c ) showing the full assembly. 
     It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, as the invention may admit to other equally effective embodiments. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. 
     In accordance with the present invention, an isolation system with a unique pressure actuated valve is provided which may be installed prior to running the system into the wellbore. This yields a simpler and easier installation with advantages also in respect to the subsequent operation of the system. A valve system is mounted within the production screen and forms an integral part of the assembly, thereby avoiding the need for a separate isolation system to be run separately into the well. However, a valve assembly according to the present invention may be run into the wellbore and placed adjacent a production zone in a subsequent operation. 
     Referring to FIGS. 1 ( a ) through ( d ), there is shown a production tubing assembly  10  according to the present invention. The production tubing assembly  10  is mated in a conventional manner and will only be briefly described herein. Assembly  10  includes production pipe  40  that extends to the surface and a production screen assembly  12  with integral isolation valve assembly  8  controlling fluid flow through the screen assembly. In a preferred embodiment production screen assembly  12  is mounted on the exterior of isolation valve assembly  8 . Isolation valve assembly  8  is interconnected with production tubing  40  at the uphole end by threaded connection  38  and seal  36 . Similarly on the downhole end  69 , isolation valve assembly  8  is interconnected with production tubing extension  13  by threaded connection  22  and seal  24 . In the views shown, the production tubing assembly  10  is disposed in well casing  11  and has inner tubing  14 , with an internal bore  15 , extending through the inner bore  46  of the assembly. 
     The production tubing assembly  10  illustrates a single preferred embodiment of the invention. However, it is contemplated that the isolation valve assembly according to the present invention may have uses other than at a production zone and may be mated in combination with a wide variety of elements as understood by a person skilled in the art. Further, while only a single isolation valve assembly is shown, it is contemplated that a plurality of such valves may be placed within the production screen depending on the length of the producing formation and the amount of redundancy desired. Moreover, although an isolation screen is disclosed in the preferred embodiment, it is contemplated that the screen may include any of a variety of external or internal filtering mechanisms including but not limited to screens, sintered filters, and slotted liners. Alternatively, the isolation valve assembly may be placed without any filtering mechanisms. 
     Referring now more particularly to isolation valve assembly  8 , there is shown outer sleeve upper portion  18  joined with an outer sleeve lower portion  16  by threaded connection  28 . For the purpose of clarity in the drawings, these openings have been shown at a  45 ° inclination. Outer sleeve upper portion  18  includes two relatively large production openings  60  and  62  for the flow of fluid from the formation when the valve is in an open configuration. Outer sleeve upper portion  18  also includes through bores  48  and  50 . Disposed within bore  50  is shear pin  51 , described further below. The outer sleeve assembly has an outer surface and an internal surface. On the internal surface, the outer sleeve upper portion  18  defines a shoulder  88  (FIG.  1 ( c )) and an area of reduced wall thickness extending to threaded connection  28  resulting in an increased internal diameter between shoulder  88  and connection  28 . Outer sleeve lower portion  16  further defines internal shoulder  89  and an area of reduced internal wall thickness extending between shoulder  89  and threaded connection  22 . Adjacent threaded connection  38 , outer sleeve portion  18  defines an annular groove  76  adapted to receive a locking ring  68 . 
     Disposed within the outer sleeves is inner sleeve  20 . Inner sleeve  20  includes production openings  56  and  58  which are sized and spaced to correspond to production openings  60  and  62 , respectively, in the outer sleeve when the valve is in an open configuration. Inner sleeve  20  further includes relief bores  54  and  42 . On the outer surface of inner sleeve there is defined a projection defining shoulder  86  and a further projection  52 . Further inner sleeve  20  includes a portion  21  having a reduced external wall thickness. Portion  21  extends down hole and slidably engages production pipe extension  13 . Adjacent uphole end  67 , inner sleeve  20  includes an area of reduced external diameter  74  defining a shoulder  72 . 
     In the assembled condition shown in FIGS.  1 ( a ) through ( d ), inner sleeve  20  is disposed within outer sleeves  16  and  18 , and sealed thereto at various locations. Specifically, on either side of production openings  60  and  62 , seals  32  and  34  seal the inner and outer sleeves. Similarly, on either side of shear pin  51 , seals  26  and  30  seal the inner sleeve and outer sleeve. The outer sleeves and inner sleeve combine to form a first chamber  55  defined by shoulder  88  of outer sleeve  18  and by shoulder  86  of the inner sleeve. A second chamber  43  is defined by outer sleeve  16  and inner sleeve  20 . A spring member  80  is disposed within second chamber  43  and engages production tubing  13  at end  82  and inner sleeve  20  at end  84 . A lock ring  68  is disposed within recess  76  in outer sleeve  18  and retained in the recess by engagement with the exterior of inner sleeve  20 . Lock ring  68  includes a shoulder  70  that extends into the interior of the assembly and engages a corresponding external shoulder  72  on inner sleeve  20  to prevent inner sleeve  20  from being advanced in the direction of arrow  64  beyond lock ring  68  while it is retained in groove  76 . 
     The valve assembly of the present invention has three configurations as shown in FIGS. 1 through 3. In a first configuration shown in FIG. 1, the production openings  56  and  58  in inner sleeve  20  are axially spaced from production openings  60  and  62  along longitudinal axis  90 . Thus, valve assembly  8  is closed and restricts flow through screen  12  into the interior of the production tubing. The inner sleeve is locked in the closed configuration by a combination of lock ring  68  which prevents movement of inner sleeve  20  up hole in the direction of arrow  64  to the open configuration. Movement down hole is prevented by shear pin  51  extending through bore  50  in the outer sleeve and engaging an annular recess in the inner sleeve. Therefore, in this position the inner sleeve is in a locked closed configuration. 
     In a second configuration shown in FIG. 2, shear pin  51  has been severed and inner sleeve  20  has been axially displaced down hole in relation to the outer sleeve in the direction of arrow  66  until external shoulder  52  on the inner sleeve engages end  53  of outer sleeve  16 . The production openings of the inner and outer sleeves continue to be axial displaced to prevent fluid flow therethrough. With the inner sleeve axial displaced down hole, lock ring  68  is disposed adjacent reduced outer diameter portion  74  of inner sleeve  20  such that the lock ring may contract to a reduced diameter configuration. In the reduced diameter configuration shown in FIG. 2, lock ring  68  may pass over recess  76  in the outer sleeve without engagement therewith. Therefore, in this configuration, inner sleeve is in an unlocked position. 
     In a third configuration shown in FIG. 3, inner sleeve  20  is axially displaced along longitudinal axis  90  in the direction of arrow  64  until production openings  56  and  58  of the inner sleeve are in substantial alignment with production openings  60  and  62 , respectively, of the outer sleeve. Axial displacement is stopped by the engagement of external shoulder  86  with internal shoulder  88 . In this configuration, valve assembly  8  is in an open position. 
     In the operation of a preferred embodiment, at least one isolation valve according to the present invention is mated with production screen  12  and, production tubing  13  and  40 , to form production assembly  10 . The production assembly according to FIG. 1 with the isolation valve in the locked-closed configuration, is then inserted into casing  11  until it is positioned adjacent a production zone (not shown). When access to the production zone is desired, a predetermined pressure differential between the casing annulus  44  and internal annulus  46  is established to shift inner sleeve  20  to the unlocked-closed configuration shown in FIG.  2 . It will be understood that the amount of pressure differential required to shift inner sleeve  20  is a function of the force of spring  80 , the resistance to movement between the inner and outer sleeves, and the shear point of shear pin  51 . Thus, once the spring force and resistance to movement have been overcome, the shear pin determines when the valve will shift. Therefore, the shifting pressure of the valve may be set at the surface by inserting shear pins having different strengths. 
     A pressure differential between the inside and outside of the valve results in a greater amount of pressure being applied on external shoulder  86  of the inner sleeve than is applied on projection  52  by the pressure on the outside of the valve. Thus, the internal pressure acts against shoulder  86  of to urge inner sleeve  20  in the direction of arrow  66  to sever shear pin  51  and move projection  52  into contact with end  53  of outer sleeve  16 . It will be understood that relief bore  48  allows fluid to escape the chamber formed between projection  52  and end  53  as it contracts. In a similar fashion, relief bore  42  allows fluid to escape chamber  43  as it contracts during the shifting operation. After inner sleeve  20  has been shifted downhole, lock ring  68  may contract into the reduced external diameter of inner sleeve positioned adjacent the lock ring. Often, the pressure differential will be maintained for a short period of time at a pressure greater than that expected to cause the down hole shift to ensure that the shift has occurred. This is particularly important where more than one valve according to the present invention is used since once one valve has shifted to an open configuration in a subsequent step, a substantial pressure differential is difficult to establish. 
     The pressure differential is removed, thereby decreasing the force acting on shoulder  86  tending to move inner sleeve  20  down hole. Once this force is reduced or eliminated, spring  80  urges inner sleeve  20  into the open configuration shown in FIG.  3 . Lock ring  68  is in a contracted state and no longer engages recess  76  such the ring now slides along the inner surface of the outer sleeve. In a preferred embodiment spring  80  has approximately 300 pounds of force in the compressed state in FIG.  2 . However, varying amounts of force may be required for different valve configurations. Moreover, alternative sources other than a spring may be used to supply the force for opening. As inner sleeve  20  moves to the open configuration, relief bore  54  allows fluid to escape chamber  55  as it is contracted, while relief bores  48  and  42  allow fluid to enter the connected chambers as they expand. 
     Although only a single preferred embodiment of the invention has been shown and described in the foregoing description, numerous variations and uses of a valve according to the present invention are contemplated. As examples of such modification, but without limitation, the valve connections to the production tubing may be reversed such that the inner sleeve moves down hole to the open configuration. In this configuration, use of a spring  80  may not be required as the weight of the inner sleeve may be sufficient to move the valve to the open configuration. Further, the inner sleeve may be connected to the production tubing and the outer sleeve may be slidable disposed about the inner sleeve. A further contemplated modification is the use of an internal mechanism to engage a shifting tool to allow tools to manipulate the valve if necessary. In such a configuration, locking ring  68  may be replaced by a moveable lock that could again lock the valve in the closed configuration. Alternatively, spring  80  may be disengageable to prevent automatic reopening of the valve. 
     Further, use of a valve according to the present invention is contemplated in many systems. One such system is the ISO System offered by OSCA, Inc. and described in U.S. Pat. No. 5,609,204, the disclosure therein is hereby incorporated by reference. A tool shiftable valve may be utilized within the production screens to accomplish the gravel packing operation. Such a valve could be closed as the crossover tool string is removed to isolate the formation. The remaining production valves adjacent the production screen may be pressure actuated valves according to the present invention such that inserting a tool string to open the valves is unnecessary. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.