PATENT ABSTRACT
A system and method for completing a well with multiple zones of production is provided, including a casing having a plurality of flapper valves integrated therein for isolating each well zone and a perforating gun string for selectively perforating the casing and underlying formation at each well zone to establish communication between the formation and the interior of the casing and to facilitate delivery of treatment fluid to each of the multiple well zones. Furthermore, the present invention further discloses mechanisms for selectively actuating each flapper valve, such as by detonating a perforating gun in a perforating gun string. Still furthermore, the present invention discloses a method of providing a perforating gun string having multiple guns, each gun selectively detonated at a corresponding well zone, and the gun string being stored in a lubricator at the surface between alternating sequences of perforating and treating the well zones.

PATENT DESCRIPTION
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This is a continuation-in-part of U.S. Ser. No. 10/905,073, filed Dec. 14, 2004, entitled “SYSTEM FOR COMPLETING MULTIPLE WELL INTERVALS.” 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to recovery of hydrocarbons in subterranean formations, and more particularly to a system and method for delivering treatment fluids to wells having multiple production zones.  
         [0004]     2. Background of the Invention  
         [0005]     In typical wellbore operations, various treatment fluids may be pumped into the well and eventually into the formation to restore or enhance the productivity of the well. For example, a reactive or non-reactive “fracturing fluid” or a “frac fluid” may be pumped into the wellbore to initiate and propagate fractures in the formation thus providing flow channels to facilitate movement of the hydrocarbons to the wellbore so that the hydrocarbons may be pumped from the well. In such fracturing operations, the fracturing fluid is hydraulically injected into a wellbore penetrating the subterranean formation and is forced against the formation strata by pressure. The formation strata is forced to crack and fracture, and a proppant is placed in the fracture by movement of a viscous-fluid containing proppant into the crack in the rock. The resulting fracture, with proppant in place, provides improved flow of the recoverable fluid (i.e., oil, gas or water) into the wellbore. In another example, a reactive stimulation fluid or “acid” may be injected into the formation. Acidizing treatment of the formation results in dissolving materials in the pore spaces of the formation to enhance production flow.  
         [0006]     Currently, in wells with multiple production zones, it may be necessary to treat various formations in a multi-staged operation requiring many trips downhole. Each trip generally consists of isolating a single production zone and then delivering the treatment fluid to the isolated zone. Since several trips downhole are required to isolate and treat each zone, the complete operation may be very time consuming and expensive.  
         [0007]     Accordingly, there exists a need for systems and methods to deliver treatment fluids to multiple zones of a well in a single trip downhole.  
       SUMMARY  
       [0008]     The present invention relates to a system and method for delivering a treatment fluid to a well having multiple well zones (e.g., production zones). According to some embodiments of the present invention, a well completion system is provided having: (1) a casing installed in a wellbore such that the casing intersects one or more well zones, (2) a perforated interval formed at each well zone to establish hydraulic communication with the underlying formation at each particular well zone for delivery of a treatment fluid or for receiving a production fluid, and (3) a flapper valve installed in the wellbore at each well zone above the perforated interval to provide zonal isolation between the various well zones.  
         [0009]     Another embodiment of the well completion system of the present invention includes a mechanism for selectively actuating the flapper valves. For example, one such mechanism may be a perforating gun, which actuates a selected flapper valve upon detonation.  
         [0010]     Still another embodiment of the well completion system of the present invention includes a perforating gun string including multiple perforating guns that may be fired selectively in each zone of a multi-zonal well. This embodiment also includes a lubricator for storing the gun string at the surface while each well zone is treated.  
         [0011]     Other or alternative embodiments of the present invention will be apparent from the following description, from the drawings, and from the claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The manner in which these objectives and other desirable characteristics can be obtained is explained in the following description and attached drawings in which:  
         [0013]      FIG. 1  illustrates a profile view of an embodiment of the multi-zonal well completion system of the present invention having zonal isolation flapper valves installed in a wellbore.  
         [0014]      FIG. 2  illustrates an enlarged cross-sectional view of an embodiment of the zonal isolation flapper valve of the present invention.  
         [0015]      FIGS. 3-11  illustrate a profile view of an embodiment of the method of the present invention for using the zonal isolation flapper valve system and a perforating gun string to perforate and frac a multi-zonal well. 
     
    
       [0016]     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, for the invention may admit to other equally effective embodiments.  
       DETAILED DESCRIPTION  
       [0017]     In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.  
         [0018]     In the specification and appended claims: the terms “connect”, “connection”, “connected”, “in connection with”, and “connecting” are used to mean “in direct connection with” or “in connection with via another element”; and the term “set” is used to mean “one element” or “more than one element”. As used herein, the terms “up” and “down”, “upper” and “lower”, “upwardly” and downwardly”, “upstream” and “downstream”; “above” and “below”; and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly describe some embodiments of the invention. Moreover, the term “treatment fluid” includes any fluid delivered to a formation to stimulate production including, but not limited to, fracing fluid, acid, gel, foam or other stimulating fluid.  
         [0019]     Generally, this invention relates to a system and method for completing multi-zone wells by delivering a treatment fluid to achieve productivity. Typically, such wells are completed in stages that result in very long completion times (e.g., on the order of four to six weeks). The present invention may reduce such completion time (e.g., to a few days) by facilitating multiple operations, previously done one trip at a time, in a single trip.  
         [0020]      FIG. 1  illustrates an embodiment of the well completion system of the present invention for use in a wellbore  10 . The wellbore  10  may include a plurality of well zones (e.g., formation, production, injection, hydrocarbon, oil, gas, or water zones or intervals)  12 ,  14 . The completion system includes a casing  20  having one or more zonal isolation valves  30  integrated or connected inline with the casing and arranged to correspond with each formation zone  12 ,  14 . Each zonal isolation valve  25  is arranged at or just below the corresponding well zone  12 ,  14  and includes a flapper  32  and a flapper-actuating mechanism  34 . However, exact depth positioning of the flapper  32  of each zonal isolation valve  30  is not critical, as long a flapper is arranged somewhere in between each well zone to be treated. The flapper  32  may be any structure that is moveable between an open position whereby communication is established through the axial bore of the casing  20  and a closed position whereby communication is interrupted through the axial bore of the casing. The zonal isolation valves  30  function to regulate hydraulic communication through the axial bore of the casing  20  and thus to isolate a particular well zone from other well zones. For example, to deliver a treatment fluid to the formation at well zone  14 , the flapper  32  of the isolation valve  30  shown just bellow well zone  14  must be closed. To close the flapper  32 , the flapper-actuating mechanism  34  is activated to move the flapper into the closed position and seal the axial bore of the casing  20 . Therefore, any treatment fluid injected into the axial bore of the casing  20  from the surface will be delivered to well zone  14  and blocked from communicating with well zone  12 . The flapper-actuating mechanism  34  may be a control line from the surface or a tool controlled from the surface (e.g., a perforating gun). Alternatively, the flapper-actuating mechanism  34  may be controlled remotely as by pressure pulse, electromagnetic radiation waves, seismic waves, acoustic signals, radio frequency, or other wireless signaling. Moreover, while the present invention is described with respect to flapper valves, it is intended that any type of valve or combination of valves may be used to regulate communication through the axial bore of the casing including, but not limited to a flapper valve or a ball valve.  
         [0021]      FIG. 2  illustrates an embodiment of a zonal isolation valve  30 . In this embodiment, the valve  30  includes a valve housing  31  having an axial bore therethrough and which is connected to or integrally formed with a casing  20  (or other cemented-in tubular string). The housing  31  has a recess  36  defined therein for containing a flapper  32 . The flapper  32  may be energized by any energy supplying device including, but not limited to, a coil spring, a linear spring, compressed gas spring, solenoid, gravity-actuated, mechanically actuated by a collet, fluid flow or hydraulic pressure. A sleeve  40  resides within the axial bore of the valve housing  31  adjacent the recess  36  to hold the flapper  32  in an energized state when the valve  30  is in the open position. The zonal isolation valve  30  further includes a mechanism for actuating the flapper  32  by shifting the sleeve  40  upward, thus allowing the flapper  32  to rotate such that the valve is in the closed position. In some embodiments, a spring (or other energizing device) is provided to energize the flapper. The sleeve  40  includes a piston ring  41  (or other piston element such as a tab or a protruding surface), which rests on or above a lower shoulder  37  formed on the inner bore of the valve housing  31 . The shoulder  37  prevents the sleeve  40  from moving axially downward. An upper shoulder  38  may also be formed on the inner bore of the valve housing  31  to provide an upper stop for the piston ring  41  of the sleeve  40 . An annular space  46  is defined between the valve housing  31  and the sleeve  40  for the piston ring  41  to traverse. A chamber  42  is arranged above the valve housing  31  and is hydraulically connected to the annular space  46  below the piston ring  41  via a hydraulic conduit  44 . In some embodiments, the chamber  42  is an annular chamber having an axial bore sized to receive a perforating gun string. The pressure within the annular space  46  above the piston ring  41  should be less than the well pressure, but greater than the pressure within the chamber  42 . Therefore, the pressure differential between the annular space  46  and the chamber  42  forces the sleeve axially downward and thus maintains the valve  30  in the closed position when the chamber is intact. In other embodiments, chambers  42  and  46  are set at a pressure of 0 psi or atmospheric pressure and the sleeve  40  may be held by a shear pin, rupture disk, or other frangible connection to hold the sleeve in place over the flapper  32 . To move the zonal isolation valve  30  from the open position to the closed position, the chamber  42  is ruptured (e.g., as by detonating a shaped charge of a perforating gun) to establish communication between the wellbore  10  and the annular space  46  below the piston ring  41  via the hydraulic conduit  44 . Once ruptured, well fluid flows from the wellbore  10  through the chamber  42  and into the annular space  46  below the piston ring  41  via the hydraulic conduit  44  to move the sleeve  40  axially upward. As the sleeve  40  clears the flapper  32  in the recess  36  of the valve housing  31 , the energized flapper  32  is rotates to seal the axial bore of the casing  20  and move the zonal isolation valve  30  into the closed position.  
         [0022]      FIG. 3  illustrates an embodiment of the well completion system  100  of the present invention for selectively perforating and delivering a treatment fluid to a well zone in a multi-zonal well. This well completion system  100  includes a wellbore  110  intersecting multiple well zones  112 ,  114 . The well is supported by a casing  120 , which is cemented in-place and suspended from a wellhead  130 . The wellhead  130  may include: (1) an inlet conduit  132  (or multiple inlets) for injecting a treatment fluid into the wellbore  110 , a lubricator  140  (or other tubular member inline with the casing and connected above the wellhead) for receiving a perforating gun string  150 , and an inline valve  134  for selectively sealing the wellbore  110  during injection of treatment fluid. The inlet conduit  132  is connected to a treatment fluid supply and pump (not shown) for injection of treatment fluid into the wellbore to treat isolated well zones. The perforating gun string  150  may include a plurality of guns  152 ,  154  each holding one or more explosive charges and connected together by an adapter  156 . The perforating gun string  150  may be suspended and run into the wellbore  110  by a line  160 . The line  160  may be any structure capable of supporting and transporting the perforating gun string  150  in and out of the wellbore  110  including, but not limited to, wireline, slickline, or coiled tubing. It is intended that by using wireline or slickline, depth positioning of the perforating gun string  150  may be performed with increased accuracy over prior art completion systems (e.g., casing conveyed perforating gun systems). In other embodiments, the perforating gun may be formed integral with a pumpable dart to be deployed downhole and actuated by a wireless signal as shown in U.S. Ser. No. 10/905,372, which is incorporate herein by reference. The well completion system further includes one or more zonal isolation valves  30 A,  30 B for isolating and treating well zones  112  and  114  respectively. Each zonal isolation valve  30 A,  30 B is as described in detail above and illustrated in  FIG. 2 . However, it is intended that other types of valves or combinations of valves may be used to isolate particular well zones.  
         [0023]     In operating the well completion system  100 , with respect to  FIG. 4 , the inline valve  134  of the wellhead  130  is opened such that the perforating gun string  150  may be lowered into the well. In order to treat the well zone  112  underlying the casing  120 , the perforating gun string  150  is first suspended by the line  160  and lowered to the target depth, which corresponds with the chamber  42 A of valve  30 A via the wellhead  130 .  
         [0024]     With respect to  FIG. 5 , once the perforating gun string  150  is lowered to the target depth at well zone  112  such that the lower-most gun  152  is adjacent the chamber  42 A of valve  30 A, the gun is detonated. The explosive charges of the lower gun  152  ignite and penetrate the surrounding formation at well zone  112  and simultaneously rupture the chamber  42 A. In some embodiments, the perforating gun string  150  may be oriented, centralized, and positioned in the wellbore  110  as desired before ignition to create more uniform size penetrations. With more uniform sized penetrations, the treatment fluid subsequently delivered may be more equally distributed around the casing  120 .  
         [0025]     With respect to  FIG. 6 , with the chamber  42 A ruptured, well fluid from the surrounding formation well zone  112  enters the chamber  42 A and acts against the piston ring  41 A via the hydraulic conduit  44 A to move the sleeve  40 A axially upward.  
         [0026]     With respect to  FIG. 7 , once the sleeve  40 A has been shifted upward a sufficient distance, the energized flapper  32 A rotates to seal the axial bore of the casing  120 . At this point, the well zone  112  is isolated from any other well zones below the valve  30 A.  
         [0027]     With respect to  FIG. 8 , once the well zone  112  is isolated, the perforating gun string  150  is pulled from the wellbore  110 . A treatment fluid may then be injected into the perforated well zone  112  via the inlet conduit  132 . In some embodiments, the gun string  150  may remain in the lubricator  140 , which is sealed off from the wellbore  110  by the inline valve  134 , instead of being removed from the completion system  100  all together. Each of the guns in the gun string are selectively detonated a each corresponding well zone. In such embodiments, significant operating time and cost saving may be achieved and more individual formation layers may be treated offering increased productivity.  
         [0028]     With respect to  FIG. 9 , after treatment of well zone  112  is completed, it may be desirable to treat an upper well zone  114 . In this event, inline valve  134  of wellhead  130  is opened and the perforating gun string  150  is lowered to the target depth such that the lower-most gun  154  is adjacent the chamber  42 B of valve  30 B. In this position, the gun  154  is detonated. The explosive charges of the upper gun  154  ignite and penetrate the surrounding formation at well zone  114  and simultaneously rupture the chamber  42 B.  
         [0029]     With respect to  FIG. 10 , with the chamber  42 B ruptured, well fluid from the surrounding formation well zone  114  enters the chamber  42 B and acts against the piston ring  41 B via the hydraulic conduit  44 B to move the sleeve  40 B axially upward. Once the sleeve  40 B has been shifted upward a sufficient distance, the energized flapper  32 B rotates to seal the axial bore of the casing  120 . At this point, the well zone  114  is isolated from well zone  112  and any other well zones below the valve  30 B.  
         [0030]     With respect to  FIG. 11 , once the well zone  114  is isolated, the perforating gun string  150  is pulled from the wellbore  110 . A treatment fluid may then be injected into the perforated well zone  114  via the inlet conduit  132 . Again, in some embodiments, the gun may remain in the lubricator  140 , which is sealed off from the wellbore  110  by the inline valve  134 .  
         [0031]     In some embodiments, the well zones are selectively isolated and perforated starting from the bottom-most well zone and progressing uphole. In this way, each well zone is isolated from other downhole well zones by the zonal isolation valve and from other uphole well zones by the casing, which is not yet perforated for the uphole well zones.  
         [0032]     Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.