An apparatus for isolating a first zone from a second zone in a subterranean wellbore. The apparatus includes an outer tubular and an inner tubular disposed within the outer tubular forming an annular flow path therebetween that is in fluid communication with the first zone. The inner tubular defines a central flow path that is in fluid communication with the second zone. A sleeve having at least one seal is positioned in the annular flow path and is axially movable relative to the inner and outer tubulars between a closed position wherein the seal engages the inner tubular and an open position wherein the seal engages the outer tubular. A mandrel is slidably disposed within the inner tubular and is coupled to the sleeve. The mandrel is operable to shift the sleeve between the open position and the closed position responsive to changes in pressure within the central flow path.

CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation of co-pending application Ser. No. 13/878,599, filed Apr. 10, 2013, which is a United States National Stage application of International Application no. PCT/US2012/047125, filed Jul. 18, 2012. The entire disclosures of these prior applications are incorporated herein by this reference. 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    This invention relates, in general, to equipment utilized in conjunction with operations performed in subterranean wells and, in particular, to a reclosable multi zone isolation tool for isolating an upper zone from a lower zone in a subterranean wellbore and a method for use thereof 
       BACKGROUND OF THE INVENTION 
       [0003]    Without limiting the scope of the present invention, its background will be described with reference to producing multiple hydrocarbon bearing subterranean zones in a well, as an example. It is common to encounter hydrocarbon wells that traverse more than one separate subterranean hydrocarbon bearing zone. In such wells, the separate subterranean hydrocarbon bearing zones may have similar or different characteristics. For example, the separate subterranean hydrocarbon bearing zones may have significantly different formation pressures. Even with the different pressures regimes, it may nonetheless be desirable to complete each of the multiple zones prior to producing the well. In such cases, it may be desirable to isolate certain of the zones from other zones after completion. 
         [0004]    For example, when multiple productive zones that have significantly different formation pressures are completed in a single well, hydrocarbons from a high pressure zone may migrate to a lower pressure zone during production. It has been found, however, that this migration of hydrocarbons from one zone to another may decrease the ultimate recovery from the well. One way to overcome this fluid loss from a high pressure zone into a lower pressure zone during production and to maximize the ultimate recovery from the well is to initially produce only the high pressure zone and delay production from the lower pressure zone. Once the formation pressure of the high pressure zone has decreased to that of the lower pressure zone, the two zones can be produced together without any loss of reserves. It has been found, however, that from an economic perspective, delaying production from the lower pressure zone while only producing from the high pressure zone may be undesirable. 
         [0005]    A need has therefore arisen for an apparatus that provides for the isolation of separate zones traversed by a wellbore. A need has also arisen for such an apparatus that does not required delayed production from a lower pressure zone during production from a high pressure zone. Further, a need has arisen for such an apparatus that does not allow fluid loss from a high pressure zone into a lower pressure zone if both zones are produced at the same time. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention disclosed herein comprises an apparatus and method that provides for the isolation of separate zones traversed by a wellbore. In addition, the apparatus and method of the present invention do not required delayed production from a lower pressure zone during production from a high pressure zone. Further, the apparatus and method of the present invention enable simultaneous production from multiple zones without fluid loss from a high pressure zone into a lower pressure zone. 
         [0007]    In one aspect, the present invention is directed to an apparatus for isolating a first zone from a second zone in a subterranean wellbore. The apparatus includes an outer tubular and an inner tubular disposed within the outer tubular forming a substantially annular flow path therebetween that is in fluid communication with the first zone. The inner tubular defines a central flow path therein that is in fluid communication with the second zone. A sleeve having at least one seal disposed on an inner surface thereof is positioned in the annular flow path to control fluid flow therethrough. The sleeve is axially movable relative to the outer tubular and the inner tubular between a closed position wherein the seal engages an outer surface of the inner tubular and an open position wherein the seal engages an outer surface of the outer tubular. A mandrel is slidably disposed within the inner tubular and coupled to the sleeve. The mandrel is operable to shift the sleeve between the open position and the closed position responsive to changes in pressure within the central flow path. 
         [0008]    In one embodiment, a collet assembly is coupled to the sleeve to selectively prevent shifting of the sleeve relative to the outer tubular when the sleeve is in the open position and when the sleeve is in the closed position. In another embodiment, the sleeve has a plurality of seals disposed on the inner surface thereof such that the seals engage the outer surface of the inner tubular in the closed position and the outer surface of the outer tubular in the open position. In some embodiments, the outer tubular includes an extension that forms a substantially annular pocket such that the at least one seal engages the outer surface of the extension in the open position. 
         [0009]    In certain embodiments, the mandrel forms at least a portion of the inner tubular. In one embodiment, the mandrel and the inner tubular define an actuation chamber operable to receive pressure from within the central flow path to bias the mandrel in a first direction relative to the inner tubular and shift the sleeve from the closed position to the open position. In another embodiment, an equalization pathway is disposed within the annular flow path to selectively prevent operation of the sleeve from the closed position to the open position. 
         [0010]    In some embodiments, a lock assembly is positioned between the mandrel and the inner tubular that selectively prevents movement of the mandrel in the second direction relative to the inner tubular when the sleeve is in the open position. In these embodiments, the lock assembly may include a spring operated lug support and at least one lug such that the lug support props the lug radially outwardly to create interference with the inner tubular. Also, in these embodiments, the mandrel may include at least one reclosing port operable to receive pressure from within the central flow path, when the sleeve is in the open position, to release the lock assembly and to bias the mandrel in the second direction relative to the inner tubular, thereby shifting the sleeve from the open position to the closed position. 
         [0011]    In another aspect, the present invention is directed to an apparatus for isolating a first zone from a second zone in a subterranean wellbore. The apparatus includes an outer tubular and an inner tubular disposed within the outer tubular forming a substantially annular flow path therebetween that is in fluid communication with the first zone. The inner tubular defines a central flow path therein that is in fluid communication with the second zone. The outer tubular includes an extension that forms a substantially annular pocket. A sleeve having at least one seal disposed on an inner surface thereof is positioned in the annular flow path to control fluid flow therethrough. The sleeve is axially movable relative to the outer tubular and the inner tubular between a closed position wherein the seal engages an outer surface of the inner tubular and an open position wherein the seal engages an outer surface of the extension of the outer tubular. A mandrel is slidably disposed within the inner tubular and is coupled to the sleeve. The mandrel is operable to shift the sleeve between the open position and the closed position responsive to changes in pressure within the central flow path. The mandrel and the inner tubular define an actuation chamber operable to receive pressure from within the central flow path to bias the mandrel in a first direction relative to the inner tubular and shift the sleeve from the closed position to the open position. The mandrel includes at least one reclosing port operable to receive pressure from within the central flow path when the sleeve is in the open position to bias the mandrel in a second direction relative to the inner tubular and shift the sleeve from the open position to the closed position. 
         [0012]    In a further aspect, the present invention is directed to a method for isolating a first zone from a second zone in a subterranean wellbore. The method includes disposing a multi zone isolation tool within the wellbore in a closed position, the tool including an inner tubular defining a central flow path and an outer tubular defining an annular flow path with the inner tubular, the annular flow path in fluid communication with the first zone, the central flow path in fluid communication with the second zone; maintaining the tool in the closed position while treating the second zone by equalizing pressure in the central flow path and the annular flow path; operably coupling a tubing string with the inner tubular; varying the pressure in the central flow path; biasing a mandrel slidably disposed within the inner tubular in a first direction; shifting a sleeve having at least one seal disposed on an inner surface thereof and coupled to the mandrel from the closed position wherein the seal engages an outer surface of the inner tubular to an open position wherein the seal engages an outer surface of the outer tubular; aligning a fluid diverter with at least one reclosing port of the mandrel; varying the pressure in the central flow path; biasing the mandrel in a second direction; and shifting the sleeve from the open position to the closed position. 
         [0013]    The method may also include selectively preventing shifting of the sleeve when the sleeve is in the open position and when the sleeve is in the closed position with a collet assembly coupled to the sleeve, selectively preventing movement of the mandrel in the second direction when the sleeve is in the open position with a lock assembly positioned between the mandrel and the inner tubular, propping the lug radially outwardly with a spring operated lug support to create interference with the inner tubular, releasing the lock assembly and/or pressurizing an actuation chamber disposed between the mandrel and the inner tubular. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures in which corresponding numerals in the different figures refer to corresponding parts and in which: 
           [0015]      FIG. 1  is a schematic illustration of a completion system including a multi zone isolation tool of the present invention; 
           [0016]      FIGS. 2A-2D  are cross sectional views of successive axial sections of a multi zone isolation tool of the present invention in the closed position; 
           [0017]      FIGS. 3A-3D  are cross sectional views of successive axial sections of a multi zone isolation tool of the present invention in the open position; and 
           [0018]      FIGS. 4A-4D  are cross sectional views of successive axial sections of a multi zone isolation tool of the present invention in the open position with a fluid diverter positioned therein. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts, which can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention, and do not delimit the scope of the present invention. 
         [0020]    The present invention provides improved methods and tools for completing and separately producing individual hydrocarbon zones in a single well. The methods can be performed in either vertical or horizontal wellbores. The term “vertical wellbore” is used herein to mean the portion of a wellbore in a producing zone, which is substantially vertical, inclined or deviated. The term “horizontal wellbore” is used herein to mean the portion of a wellbore in a producing zone, which is substantially horizontal. Since the present invention is applicable in vertical, horizontal and inclined wellbores, the terms “upper and lower” and “top and bottom” as used herein are relative terms and are intended to apply to the respective positions within a particular wellbore while the term “levels” is meant to refer to respective spaced positions along the wellbore. The term “zone” is used herein to refer to separate parts of the well designated for treatment and/or production and includes an entire hydrocarbon formation or separate portions of the same formation. As used herein, “down,” “downward” or “downhole” refer to the direction in or along the wellbore from the wellhead toward the producing zone regardless of the wellbore's orientation toward the surface or away from the surface. Accordingly, the upper zone would be the first zone encountered by the wellbore and the lower zone would be located further along the wellbore. Tubing, tubular, casing, pipe liner and conduit are interchangeable terms used herein to refer to walled fluid conductors. 
         [0021]    Referring initially to  FIG. 1 , a multi zone isolation tool of the present invention is disposed within a cased wellbore that is generally designated  10 . Wellbore  10  is illustrated intersecting two separate hydrocarbon bearing zones, upper zone  12  and lower zone  14 . For purposes of description, only two zones are shown but it is understood that the present invention has application to isolate any number of zones within a well. As mentioned, while wellbore  10  is illustrated as a vertical cased well with two producing zones, the present invention is applicable to horizontal and inclined wellbores with more than two producing zones and in uncased wells. 
         [0022]    A completion string disposed within wellbore  10  includes upper and lower sand screen assemblies  16 ,  18  that are located proximate to zones  12 ,  14 , respectively. Wellbore  10  includes a casing string  20  that has been perforated at locations  22 ,  24  to provide fluid flow paths into casing  20  from zones  12 ,  14 , respectively. The completion string includes production tubing  26 , packers  28 ,  30  and a crossover sub  32  to enable fluid flow between the interior of the completion string and annulus  34 . The completion string also includes multi zone isolation tool  36  of the present invention. As explained in greater detail below, tool  36  functions to connect lower sand screen assembly  18  and production tubing  26  via a first flow path. Tool  36  also functions to selectively isolate and connect upper sand screen assembly  16  to annulus  34  via a second flow path. Thus, tool  36  selectively isolates zone  12  and zone  14  and allows zones  12 ,  14  to be independently produced. 
         [0023]    Referring next to  FIGS. 2A-2D , therein is depicted a more detailed illustration of an embodiment of a multi zone isolation tool of the present invention that is generally designated  100 . Tool  100  includes a substantially tubular outer housing assembly  102  that is formed from a plurality of housing members that are securably and sealingly coupled together by threading, set screws or similar technique. In the illustrated embodiment, housing assembly  102  includes an upper housing member  104 , a first upper intermediate housing member  106 , a second upper intermediate housing member  108  having a housing extension  110 , a housing coupling  112 , a sleeve housing member  114  that forms a substantially annular pocket  116  with housing extension  110 , a lower intermediate housing member  118 , a housing coupling  120  and a lower housing member  122 . It is to be understood by those skilled in the art that even though a particular arrangement of housing members is depicted and described, other arrangements of housing members are possible and are considered within the scope of the present invention. 
         [0024]    Disposed within housing assembly  102  is an inner tubular assembly  124  that is formed from a plurality of tubular members that are securably and sealingly coupled together by threading, set screws or similar technique. In the illustrated embodiment, tubular assembly  124  includes an upper tubular member  126  having a polished bore receptacle  128 , a first upper intermediate tubular member  130  having a radially expanded region  132 , a second upper intermediate tubular member  134  having a lower shoulder  136 , a first intermediate tubular member  138 , a second intermediate tubular member  140 , a first lower intermediate tubular member  142  having a profile  144 , a second lower intermediate tubular member  146  and a lower tubular member  148 . It is to be understood by those skilled in the art that even though a particular arrangement of tubular members is depicted and described, other arrangements of tubular members are possible and are considered within the scope of the present invention. 
         [0025]    Slidably disposed within tubular assembly  124  is a mandrel assembly  150  that is formed from a plurality of mandrel members that are securably and sealingly coupled together by threading, set screws or similar technique. In the illustrated embodiment, mandrel assembly  150  includes an upper mandrel member  152  including a profile  154  and a plurality of reclosing ports  156 , an intermediate mandrel member  158  that carries one or more lugs  160  and a lower mandrel member  162  including a plurality of opening ports  164 . It is to be understood by those skilled in the art that even though a particular arrangement of mandrel members is depicted and described, other arrangements of mandrel members are possible and are considered within the scope of the present invention. 
         [0026]    Disposed between tubular assembly  124  and mandrel assembly  150  is a lug support sleeve  166  and a spring  168 . Together, lug support sleeve  166 , spring  168  and lugs  160  may be referred to as a lock assembly. Near their lower ends, tubular assembly  124  and mandrel assembly  150  define an actuation chamber  170  that is in fluid communication with opening ports  164  of mandrel assembly  150 . Together, tubular assembly  124  and mandrel assembly  150  define a central flow path  172  that extends between the upper and lower ends of tool  100 . As such, at least portions of mandrel assembly  150  may be considered as part of tubular assembly  124  in the section between tubular member  130  and tubular member  134 . As previously described with reference to  FIG. 1 , central flow path  172  is in fluid communication with lower sand screen assembly  18  and therefore lower zone  14 . 
         [0027]    Together, housing assembly  102  and tubular assembly  124  define a substantially annular flow path  174 . As previously described with reference to  FIG. 1 , annular flow path  174  is in fluid communication with upper sand screen assembly  16  and therefore upper zone  12 . Disposed within annular flow path  174  is a sleeve  176  that has a plurality of seals  178  disposed on the inner surface thereof. In the illustrated embodiment, sleeve  176  is threadably coupled to a collet assembly  180 . Near its lower end, sleeve  176  is securably coupled to mandrel assembly  150  via a threaded connector held in position by a pin  182  that extends through one of three radially expanded sections of mandrel assembly  150  (only one being visible in the figures). Each of the radially expanded sections extends approximately thirty degrees in the circumferential direction such that the flow of fluid through annular flow path  174  is not prevented by the radially expanded sections. Also disposed within annular flow path  174  is an equalization pathway depicted as control line  184  that extends between tubular member  130  and tubular member  146 . 
         [0028]    The operation of tool  100  will now be described with reference to  FIGS. 2A-2D  and  3 A- 3 D. Tool  100  is initially run into the wellbore as part of the completion string with housing assembly  102  preferably forming a portion of the tubular string that extends to the surface. The completion string is the positioned at the desired location, such as that depicted in  FIG. 1 . Initially, tool  100  is in its closed position as depicted in  FIGS. 2A-2D  wherein sleeve  176  is in its lower position with seals  178  engaging an outer sealing surface of tubular member  130  such that fluid flow through annular flow path  174  is prevented. In this configuration, treatment or other operations requiring fluid flow and pressure fluctuations downhole of tool  100  are performed through central flow path  172 . Even though pressure fluctuations are occurring in central flow path  172  and are communicated to actuation chamber  170  and therefore to a lower piston area of mandrel assembly  150 , operation of tool  100  is prevented. Specifically, annular flow path  174  and central flow path  172  are in fluid communication with one another above tool  100 . In addition, the pressure in annular flow path  174  above sleeve  176  is communicated to an upper piston area of mandrel assembly  150  via control line  184  that serves as a pathway to equalize pressure across mandrel assembly  150 . 
         [0029]    After treatment or other operations to the lower zone or zones are complete, the lower zones may be plugged off and a tubing string may be stabbed into polished bore receptacle  128  of tubular assembly  124 . In this configuration, annular flow path  174  and central flow path  172  are no longer in fluid communication with one another above tool  100 . Now, increased pressure within central flow path  172  is communicated to actuation chamber  170  via opening ports  164 . This pressure acts on the lower piston area of mandrel assembly  150  and urges mandrel assembly in the uphole direction. Mandrel assembly  150  is threadably coupled to sleeve  176  and sleeve  176  is threadably coupled to collet assembly  180 . As best seen in  FIG. 2B , collet assembly  180  selectively prevents upward movement of sleeve  176  and mandrel assembly  150  until the pressure exerted on the lower piston area of mandrel assembly  150  exceeds a predetermined value sufficient to radially inwardly retract the collet fingers of collet assembly  180 , to pass through a downwardly facing shoulder  186  of housing assembly  102 . 
         [0030]    When the predetermined value is reached and the collet fingers of collet assembly  180  are radially retracted, sleeve  176  and mandrel  150  shift in the uphole direction to the position depicted in  FIGS. 3A-3D . As illustrated, collet assembly  180  reengages with housing assembly  102  in annular recess  188 . Sleeve  176  is in its upper position partially disposed within annular pocket  116  of housing assembly  102  with seals  178  engaging an outer sealing surface of housing extension  110 . In this configuration, fluid communication between annular flow path  174  and the upper zone is allowed, enabling, for example, production from the upper zone into annular flow path  174 . Importantly, in this configuration, seals  178  are protected from fluid flow or any abrasive materials therein as seals  178  are sealingly engaged with the outer sealing surface of housing extension  110  and out of the flow path. As such, seals  178  are not susceptible to damage during production from the upper zone or other fluid flow operations therethrough. Also, in this configuration, downhole movement of mandrel assembly  150  is prevented as spring  168  has urged lug support sleeve  166  under lugs  160  which are now aligned with and interfere with profile  144  of tubular member  142 , as best seen in  FIG. 3C . 
         [0031]    Referring additionally to  FIGS. 4A-4D , if it is desired to return tool  100  from the open position to the closed position, a fluid diverter  190  may be run downhole on a conveyance that is depicted as wireline  192  and positioned within tool  100 . Fluid diverter  190  includes a latch assembly  194  that is operable to engage profile  154  of mandrel assembly  150 . Once engaged, a discharge port  196  of fluid diverter  190  is in fluid communication with reclosing ports  156  of mandrel assembly  150 . In this configuration, fluid pressure above seals  198  of fluid diverter  190  in central flow path  172  is routed to chamber  200 , which is in fluid communication with reclosing ports  156  via discharge port  196 . The fluid pressure then acts on a lower piston area of lug support sleeve  166  which compresses spring  168  and unprops lugs  160 , as best seen in  FIG. 4C . 
         [0032]    The fluid pressure from chamber  200  now acts on an upper piston area of mandrel assembly  150  and urges mandrel assembly  150  downhole. As best seen in  FIG. 4B , collet assembly  180  selectively prevents downward movement of sleeve  176  and mandrel assembly  150  until the pressure exerted on the upper piston area of mandrel assembly  150  exceeds a predetermined value sufficient to radially inwardly retract the collet fingers of collet assembly  180 , to pass through an upwardly facing shoulder of annular recess  188  of housing assembly  102 . When the predetermined value is reached and the collet fingers of collet assembly  180  are radially retracted, sleeve  176  and mandrel  150  shift in the downhole direction to the position depicted in  FIGS. 2A-2D . As illustrated, collet assembly  180  is now repositioned below downwardly facing shoulder  186  of housing assembly  102 , thereby selectively preventing upward movement of sleeve  176  and mandrel assembly  150 . Sleeve  176  is now repositioned in its lower position with seals  178  engaging an outer sealing surface of tubular member  130 . In this configuration, fluid flow through annular flow path  174  is prevented and tool  100  has been returned to its closed configuration. The processes of opening and reclosing tool  100  can be repeated as required to enable independent and selective production from the upper and lower zones. 
         [0033]    While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments as well as other embodiments of the invention will be apparent to persons skilled in the art upon reference to the description. It is, therefore, intended that the appended claims encompass any such modifications or embodiments.