You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
CROSS REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention is in the field of equipment used in the production of fluids from, and injection of fluids into, oil and gas wells having multiple zones. 
     2. Background Art 
     Many oil or gas wells extend through multiple formations, resulting in the establishment of multiple zones at different depths in the well. It may be desirable to produce formation fluids such as gas or oil from different zones at different times, and to inject fluids such as water into different zones at different times, for the purpose of ultimately obtaining the maximum production from the well. Further, it may be desirable to produce formation fluids from one or more zones, while simultaneously injecting fluids into one or more other zones. Finally, it may be desirable to convert a particular zone from a production zone into an injection zone, after the zone is depleted. 
     Known equipment for these purposes usually requires pulling the completion assembly from the well, and changing or reconfiguring the equipment in the assembly, when it is desired to commence or cease production or injection in a particular zone. Further, known equipment is generally limited to the production of fluid or the injection of fluid at any given time, with simultaneous production and injection not being possible, or at least difficult. More specifically, known equipment is not capable of the simultaneous production from multiple zones and injection into multiple zones. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a method and apparatus for selectively injecting into a given zone or multiple zones, or producing from a given zone or multiple zones, without pulling the equipment from the well. A completion unit is positioned next to each zone of the formation, with zones being segregated by packers. An injection sleeve and a production sleeve are provided in each completion unit. Each sleeve essentially bridges between the completion string and the production string, which is within the completion string. Each sleeve is shifted, such as by hydraulic, electrical, or mechanical operation, to selectively align a conduit through the sleeve with its associated port in the wall of the completion string. When aligned with the inlet port, the conduit in the production sleeve conducts formation fluid into a production fluid path in the production string. When aligned with the outlet port, the conduit in the injection sleeve conducts injection fluid from an injection fluid path into the formation. Regardless of sleeve position, both injection flow and production flow can be maintained through the completion unit to other completion units above or below. 
     By selectively shifting the sleeves, selected zones can be isolated, produced from, or injected into, as desired. One or more lower zones can be injected into while one or more upper zones are produced from, or vice versa. If desired, alternating zones can even be simultaneously produced from and injected into. 
    
    
     The novel features of this invention, as well as the invention itself, will be best understood from the attached drawings, taken along with the following description, in which similar reference characters refer to similar parts, and in which: 
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a longitudinal section of a production unit as implemented in the present invention, with production flow from the zone isolated; 
     FIG. 2 is a transverse section of a production sleeve as used in the production unit of FIG. 1; 
     FIG. 3 is a longitudinal section of the production unit of FIG. 1, with production flow from the zone established; 
     FIG. 4 is a longitudinal section of an injection unit as implemented in the present invention, with injection flow into the zone isolated; 
     FIG. 5 is a transverse section of an injection sleeve as used in the injection unit of FIG. 4; 
     FIG. 6 is a longitudinal section of the injection unit of FIG. 4, with injection flow into the zone established; 
     FIG. 7 is a longitudinal section of a completion unit, showing production flow from the zone established, and showing an alternative configuration of the completion and production strings; 
     FIG. 8 is a longitudinal section of the completion unit of FIG. 7, showing production flow from the zone and injection flow into the zone both isolated; and 
     FIG. 9 is a longitudinal section of the completion unit of FIG. 7, showing injection flow into the zone established. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in FIG. 1, a production unit  10  used as part of the present invention includes a completion string  12  of tubing or piping, a production string  14  of tubing or piping, one or more centralizing rings  16 , and a longitudinally shiftable production sleeve  18 . This production unit can be placed in a well bore, aligned with a selected zone of the downhole formation. The completion string  12  shown is flush joint piping, and the production string  14  can be flush joint piping. Other types of piping or tubing can also be used. The production string  14  is substantially coaxially located within the completion string  12 , centralized therein by the centralizing rings  16 . An upper end  19  and a lower end  21  of the production sleeve  18  are configured to slidably mount within production string fittings  23 , for shifting of the production sleeve  18  by means of longitudinal movement relative to the completion string  12 . It will be seen that shifting of the production sleeve  18  could be rotational relative to the completion string  12 , rather than longitudinal, if desired. 
     FIG. 2 shows a transverse section of the production sleeve  18 . One or more production fluid conduits  22  are arranged more or less radially from the center of the production sleeve  18  to its outer periphery. One or more injection fluid bypass channels  24  pass longitudinally through the production sleeve  18 , to ensure that injection fluid can bypass the production sleeve from an upper annulus to a lower annulus. A production fluid flow path  28  passes longitudinally through the production sleeve  18 , ensuring the production fluid from a lower zone can pass to an upper zone. The production fluid conduits  22  are also in fluid flow communication with the production fluid flow path  28 . 
     FIG. 1 shows only one of the production fluid conduits  22 , and only one of the bypass channels  24 . However, it can be seen that, regardless of the position of the production sleeve  18 , an injection fluid flow path exists through the production sleeve  18  as indicated by the arrow labeled IF. Further, the injection fluid flow path continues through bypass channels  26  in the centralizing rings  16 . This allows injection fluid pumped downhole in the annulus between the completion string  12  and the production string  14  to flow completely through the production unit  10  from an upper zone to a lower zone, regardless of the position of the production sleeve  18 . 
     It also can be seen that, regardless of the position of the production sleeve  18 , production fluid can flow through the production fluid flow path  28  in the production sleeve  18  as indicated by the arrow labeled PF. Further, production fluid can flow through the center of the centralizing rings  16 , in the production fluid flow path  28  in the production string  14 . This allows production fluid to flow completely through the production unit  10  from a lower zone to an upper zone, regardless of the position of the production sleeve  18 . 
     Shifting of the production sleeve  18  could be accomplished by several different means, such as hydraulically, mechanically, or electrically, or a combination thereof. FIG. 1 shows one embodiment of a hydraulic shifting means, including an upper hydraulic duct  30 , a lower hydraulic duct  32 , and a two directional hydraulic chamber  34 . A shoulder on the production sleeve  18  can be positioned in the hydraulic chamber  34 . When the upper duct  30  is pressurized, the production sleeve  18  is shifted downwardly, or to the right in the figure. When the lower duct  32  is pressurized, the production sleeve  18  is shifted upwardly, or to the left in the figure. A similar hydraulic assembly could be used to rotationally shift the production sleeve  18 , if preferred. Further, an electrical solenoid mechanism could accomplish either longitudinal or rotational shifting, if preferred. Still further, other known shifting mechanisms could be used to shift the production sleeve  18 . 
     A formation fluid inlet port  20  is formed through the wall of the completion string  12 . The production fluid conduit  22  in the production sleeve  18  does not align with the inlet port  20 , when the production sleeve  18  is in the upper position shown in FIG.  1 . This isolates the inlet port  20 , preventing flow of formation fluid through the inlet port  20 , through the production fluid conduit  22 , and into the production fluid flow path  28 . FIG. 3 illustrates that the production sleeve  18  can be selectively shifted downwardly when desired, to align the production fluid conduit  22  with the inlet port  20 . This establishes flow of formation fluid through the inlet port  20 , through the production fluid conduit  22 , and into the production fluid flow path  28 . 
     As shown in FIG. 4, an injection unit  40  used as part of the present invention includes the completion string  12 , the production string  14 , one or more centralizing rings  16 , and a longitudinally shiftable injection sleeve  42 . This injection unit also can be placed in a well bore, aligned with a selected zone of the downhole formation. As will be seen, the injection unit  40  can be associated with a production unit  10  for a particular zone of the formation, to facilitate selective production from, or injection into, the zone. An upper end  43  and a lower end  45  of the injection sleeve  42  are configured to slidably mount within production string fittings  23 , for shifting of the injection sleeve  42  by means of longitudinal movement relative to the completion string  12 . It will be seen that shifting of the injection sleeve  42  could be rotational relative to the completion string  12 , rather than longitudinal, if desired. 
     FIG. 5 shows a transverse section of the injection sleeve  42 . One or more injection fluid conduits  46  are arranged at several locations, connecting the upper side of the injection sleeve  42  to its outer periphery. One or more injection fluid bypass channels  56  pass longitudinally through the injection sleeve  42 , to ensure that injection fluid can bypass the injection sleeve from an upper annulus to a lower annulus. A production fluid flow path  28  passes longitudinally through the injection sleeve  42 , ensuring the production fluid from a lower zone can pass to an upper zone. 
     FIG. 4 shows only one of the injection fluid conduits  46 , and only one of the bypass channels  56 . However, it can be seen that, regardless of the position of the injection sleeve  42 , an injection fluid flow path exists through the injection sleeve  42  as indicated by the arrow labeled IF. Further, the injection fluid flow path continues through bypass channels  26  in the centralizing rings  16 . This allows injection fluid pumped downhole in the annulus between the completion string  12  and the production string  14  to flow completely through the injection unit  40  from an upper zone to a lower zone, regardless of the position of the injection sleeve  42 . 
     It also can be seen that, regardless of the position of the injection sleeve  42 , production fluid can flow through the production fluid flow path  28  in the injection sleeve  42  as indicated by the arrow labeled PF. Further, production fluid can flow through the center of the centralizing rings  16 , in the production fluid flow path  28  in the production string  14 . This allows production fluid to flow completely through the injection unit  40  from a lower zone to an upper zone, regardless of the position of the injection sleeve  42 . 
     Shifting of the injection sleeve  42  could be accomplished by several different means, such as hydraulically, mechanically, or electrically, or a combination thereof. FIG. 4 shows one embodiment of a hydraulic shifting means, including an upper hydraulic duct  50 , a lower hydraulic duct  52 , and a two directional hydraulic chamber  54 . A shoulder on the injection sleeve  42  can be positioned in the hydraulic chamber  54 . When the upper duct  50  is pressurized, the injection sleeve  42  is shifted downwardly, or to the right in the figure. When the lower duct  52  is pressurized, the injection sleeve  42  is shifted upwardly, or to the left in the figure. A similar hydraulic assembly could be used to rotationally shift the injection sleeve  42 , if preferred. Further, an electrical solenoid mechanism could accomplish either longitudinal or rotational shifting, if preferred. Still further, other known shifting mechanisms could be used to shift the injection sleeve  42 . 
     An injection fluid outlet port  44  is formed through the wall of the completion string  12 . The injection fluid conduit  46  in the injection sleeve  42  does not align with the outlet port  44 , when the injection sleeve  42  is in the upper position shown in FIG.  4 . This isolates the outlet port  44 , preventing flow of injection fluid through the injection fluid conduit  46 , through the outlet port  44 , and into the formation. FIG. 6 illustrates that the injection sleeve  42  can be selectively shifted downwardly when desired, to align the injection fluid conduit  46  with the outlet port  44 . This establishes flow of injection fluid through the injection fluid conduit  46 , through the outlet port  44 , and into the formation. 
     FIGS. 7,  8 , and  9  illustrate the pairing of a production unit  10  with an injection unit  40  to form a completion unit, which can be placed downhole in a well bore, aligned with a selected zone of the formation. Packers  58  can be used to isolate adjacent zones. FIGS. 7,  8 , and  9  also illustrate a variation of the configuration of the completion string and the production string, when it is desired to pump injection fluid into the annulus surrounding the completion string, rather than pumping injection fluid into an annulus between the completion string and the production string, as in the embodiments shown in FIGS. 1,  3 ,  4 , and  6 . In either embodiment, however, production fluid flow and injection fluid flow can be controlled as shown in FIGS. 7,  8 , and  9 . 
     FIG. 7 shows the production sleeve  18  in its lower position, and the injection sleeve  42  in its upper position. This establishes flow of formation fluid from the zone into the production fluid flow path  28 , while preventing flow of injection fluid into the zone. FIG. 8 shows the production sleeve  18  in its upper position, and the injection sleeve  42  in its upper position. This prevents flow of formation fluid from the zone into the production fluid flow path  28 , while also preventing flow of injection fluid into the zone. FIG. 9 shows the production sleeve  18  in its upper position, and the injection sleeve  42  in its lower position. This prevents flow of formation fluid from the zone into the production fluid flow path  28 , while establishing flow of injection fluid into the zone. 
     It can be seen that, by selective shifting of the production sleeves  18  and the injection sleeves  42  in multiple zones, one or more zones can produce formation fluid, simultaneous with the injection of fluid into one or more other zones. 
     While the particular invention as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages hereinbefore stated, it is to be understood that this disclosure is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended other than as described in the appended claims.

Summary:
A method and apparatus for simultaneously producing fluid from one or more zones of an oil or gas well, while injecting fluid into one or more other zones of the well, and for converting a depleted production zone into an injection zone, by remotely shifting sleeves in the apparatus to selectively align inlet and outlet ports with production and injection flow paths, respectively. A production string is provided within a completion string; the completion string has inlet and outlet ports to the well bore. One or more production sleeves have production conduits which can be selectively aligned with inlet ports by shifting the production sleeves. One or more injection sleeves have injection conduits which can be selectively aligned with outlet ports by shifting the injection sleeves.