Patent Publication Number: US-11643900-B2

Title: Modular pressure cylinder for a downhole tool

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Applicant claims the benefit to priority under 35 U.S.C. § 119(e) of provisional patent application 62/608,707 filed on Dec. 21, 2017. 
    
    
     FIELD OF THE INVENTION 
     This invention relates in general to piston assemblies for converting pumped fluid pressure to mechanical force in a downhole tool and, in particular, to a novel modular pressure cylinder for converting pumped fluid pressure to mechanical force in a downhole tool. 
     BACKGROUND OF THE INVENTION 
     Piston assemblies for converting pumped fluid pressure to mechanical force in a downhole tool are known and used in downhole tools such as packers, straddle packers, tubing perforators and the like. Such piston assemblies use a plurality of pistons connected to an inner or outer mandrel of a downhole tool to increase the force that can be generated from a given pressure of fluid pumped down a tubing string to the downhole tool. An example of one such piston assembly can be found in U.S. Pat. No. 8,336,615 which issued on Dec. 25, 2012. While these piston assemblies have proven useful, they suffer certain limitations that affect their utility. For example, if mechanical force is required at opposite ends of a downhole tool, a piston assembly must be provided on each end of the downhole tool, as taught for example in U.S. Pat. No. 9,598,939 which issued on Mar. 21, 2017. This increases a length of the down hole tool, which can be undesirable. 
     There therefore exists a need for a modular pressure cylinder for a downhole tool that overcomes the shortcomings of known prior art prior art piston assemblies. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide a modular pressure cylinder for a downhole tool. 
     The invention therefore provides a modular pressure cylinder for a downhole tool, comprising: an active mandrel tube having a central passage and active mandrel tube fluid ports in fluid communication with the central passage; and a modular pressure cylinder that reciprocates on the active mandrel tube, the modular pressure cylinder including at least two interconnected pressure cylinder modules having interconnected pressure cylinder walls and interconnected pressure pistons that reciprocate within pressure cylinders, the interconnected pressure pistons including pressure cylinder fluid ports that permit fluid flowing through the active mandrel tube fluid ports to enter the pressure cylinders and simultaneously urge the interconnected pressure cylinder walls and the interconnected pressure pistons to move in opposite directions along an axis of the active mandrel tube. 
     The invention further provides a modular pressure cylinder for a downhole tool, comprising: an active mandrel tube having a central passage and active mandrel tube fluid ports that provide fluid communication between the central passage and an external periphery of the active mandrel tube; and a modular pressure cylinder that reciprocates on the active mandrel tube, the modular pressure cylinder including at least two interconnected pressure cylinder modules having interconnected pressure cylinder walls and pressure pistons respectively having pressure cylinder male coupling sleeves and pressure cylinder female coupling sleeves that interconnect the pressure pistons, the pressure pistons reciprocating within pressure cylinders defined by the interconnected pressure cylinder walls and the interconnected pressure cylinder male and female coupling sleeves, the interconnected pressure cylinder male and female coupling sleeves including pressure cylinder fluid ports that permit pressurized fluid flowing through the active mandrel tube fluid ports to flow into the pressure cylinders and urge the interconnected pressure cylinder walls and the interconnected pressure pistons to move in opposite directions along an axis of the active mandrel tube. 
     The invention yet further provides a modular pressure cylinder for a downhole tool, comprising: an active mandrel tube having a central passage and active mandrel tube fluid ports that provide fluid communication between the central passage and an external periphery of the active mandrel tube with active mandrel tube axial grooves in an outer periphery thereof, the active mandrel tube axial grooves respectively being in fluid communication with the active mandrel tube fluid ports to ensure fluid communication between the central passage and respective pressure cylinder fluid ports of the modular pressure cylinder while the modular pressure cylinder is urged along an axis of the active mandrel tube; and a modular pressure cylinder that reciprocates on the active mandrel tube, the modular pressure cylinder including at least two interconnected pressure cylinder modules having interconnected pressure cylinder walls and pressure pistons respectively having pressure cylinder male coupling sleeves and pressure cylinder female coupling sleeves that interconnect the pressure pistons, the pressure pistons having pressure piston seals that respectively provide a fluid seal against the respective pressure cylinder walls, the pressure pistons reciprocating within pressure cylinders defined by the interconnected pressure cylinder walls and the interconnected pressure cylinder male and female coupling sleeves, the interconnected pressure cylinder male and female coupling sleeves including pressure cylinder fluid ports that permit pressurized fluid flowing through the active mandrel tube to flow into the pressure cylinders and urge the interconnected pressure cylinder walls and the interconnected pressure pistons to move in opposite directions along an axis of the active mandrel tube, and the pressure cylinder walls respectively including pressure cylinder pressure equalization ports to equalize fluid pressure behind the respective pressure pistons. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, in which: 
         FIG.  1    is a perspective view of an embodiment of a straddle packer with fluid pressure packer set in accordance with the invention in a run-in condition; 
         FIG.  2    is a cross-sectional view of the straddle packer shown in  FIG.  1   , in the run-in condition; 
         FIG.  3   a    is an exploded cross-sectional view of mandrel tubes and mandrel flow sub of the straddle packer shown in  FIG.  2   ; 
         FIG.  3   b    is an exploded side elevational view of the mandrel tubes and the mandrel flow sub shown in  FIG.  3     a;    
         FIG.  3   c    is an exploded cross-sectional view of sliding sleeves that reciprocate, from the run-in condition to the packer set condition, on the mandrel tubes of the straddle packer shown in  FIG.  3     b;    
         FIG.  4    is a cross-sectional view of the embodiment of the straddle packer shown in  FIG.  1    in the packer set condition; 
         FIG.  5   a    is a cross-sectional view of a velocity bypass sub of the straddle packer shown in  FIGS.  1 ,  2  and  4   , with a velocity bypass valve of the velocity bypass sub in an open condition; and 
         FIG.  5   b    is a cross-sectional view of the velocity bypass sub of the straddle packer shown in  FIG.  5   a   , with the velocity bypass valve of the velocity bypass sub in a closed condition. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention provides a modular pressure cylinder for a downhole tool. The pressure cylinder has an active mandrel tube with a central passage and active mandrel tube fluid ports in fluid communication with the central passage, and a modular pressure cylinder that reciprocates on the active mandrel tube. The modular pressure cylinder includes at least two interconnected pressure cylinder modules having interconnected pressure cylinder walls and interconnected pressure pistons that reciprocate within pressure cylinders. The interconnected pressure pistons include pressure cylinder fluid ports that permit fluid flowing through the active mandrel tube fluid ports to enter the pressure cylinders and simultaneously urge the interconnected pressure cylinder walls and the interconnected pressure pistons to move in opposite directions along an axis of the active mandrel tube. 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Part No. 
                 Part Description 
               
               
                   
                   
               
             
            
               
                   
                 10 
                 Straddle packer 
               
               
                   
                 11 
                 Multicomponent mandrel 
               
               
                   
                 12 
                 Completion string connection component 
               
               
                   
                 13 
                 Multicomponent mandrel central passage 
               
               
                   
                 14 
                 Completion string connection 
               
               
                   
                 15 
                 Upper packer element compression shoulder 
               
               
                   
                 16 
                 Upper packer element sleeve 
               
               
                   
                 18 
                 Upper packer element 
               
               
                   
                 20 
                 Upper compression bell 
               
               
                   
                 21a, 21b 
                 Upper compression bell pressure equalization ports 
               
               
                   
                 22 
                 Upper mandrel tube 
               
               
                   
                 23 
                 Upper compression bell shoulder 
               
               
                   
                 24 
                 Upper sliding sleeve 
               
               
                   
                 25 
                 Upper sliding sleeve threaded connection 
               
               
                   
                 26 
                 Upper sliding sleeve coupling 
               
               
                   
                 27 
                 Slotted sliding sleeve female coupling end 
               
               
                   
                 28 
                 Slotted sliding sleeve 
               
               
                   
                 29a, 29b 
                 Sliding sleeve finger components 
               
               
                   
                 30 
                 Mandrel flow sub 
               
               
                   
                 31 
                 Mandrel flow sub grooves 
               
               
                   
                 32a-32h 
                 Mandrel flow sub nozzles 
               
               
                   
                 33 
                 Slotted sliding sleeve captured end thread 
               
               
                   
                 33a 
                 Slotted sliding sleeve coupling thread 
               
               
                   
                 34 
                 Lower sliding sleeve coupling 
               
               
                   
                 34a 
                 Lower sliding sleeve coupling upper thread 
               
               
                   
                 34b 
                 Lower sliding sleeve coupling lower thread 
               
               
                   
                 36 
                 Lower sliding sleeve 
               
               
                   
                 37 
                 Lower sliding sleeve threaded connection 
               
               
                   
                 38 
                 Slotted sliding sleeve captured end coupling ring 
               
               
                   
                 40a, 40b 
                 Cap screws 
               
               
                   
                 42 
                 Lower mandrel tube 
               
               
                   
                 44 
                 Mandrel tube crossover component 
               
               
                   
                 46 
                 Active mandrel tube component 
               
               
                   
                 48 
                 Modular pressure cylinder 
               
               
                   
                 49a-49h 
                 Active mandrel tube fluid ports 
               
               
                   
                 50 
                 Sleeve/cylinder crossover 
               
               
                   
                 52a-52j 
                 Pressure cylinder pressure equalization ports 
               
               
                   
                 53a-53d 
                 Active mandrel tube axial grooves 
               
               
                   
                 54a-54d 
                 Pressure cylinder modules 
               
               
                   
                 55a-55d 
                 Pressure cylinder walls 
               
               
                   
                 56a-56d 
                 Pressure pistons 
               
               
                   
                 57a-57h 
                 Pressure cylinder fluid ports 
               
               
                   
                 58a-58d 
                 Pressure cylinder male coupling sleeves 
               
               
                   
                 59a-59b 
                 Pressure cylinder chambers 
               
               
                   
                 60a-60d 
                 Pressure cylinder female coupling sleeves 
               
               
                   
                 62 
                 Pressure cylinder crossover sleeve 
               
               
                   
                 64 
                 Lower compression bell 
               
               
                   
                 65a, 65b 
                 Lower compression bell equalization ports 
               
               
                   
                 66a-66d 
                 Pressure piston seals 
               
               
                   
                 66j 
                 Compression bell seal 
               
               
                   
                 67a-67d 
                 Pressure cylinder seals 
               
               
                   
                 68a-68e 
                 Pressure cylinder coupling seals 
               
               
                   
                 69 
                 Pressure cylinder crossover sleeve seal 
               
               
                   
                 70 
                 Lower compression bell male coupling sleeve 
               
               
                   
                 72 
                 Lower packer element mandrel sleeve component 
               
               
                   
                 74 
                 Lower packer element 
               
               
                   
                 76 
                 Lower crossover sub 
               
               
                   
                 78 
                 Lower packer element compression shoulder 
               
               
                   
                 80 
                 Lower crossover sub male connector 
               
               
                   
                 82 
                 Velocity bypass sub 
               
               
                   
                 83 
                 Velocity bypass sub threaded downhole end 
               
               
                   
                 84 
                 Velocity bypass valve 
               
               
                   
                 85a 
                 Velocity bypass sub connector end 
               
               
                   
                 85b 
                 Velocity bypass sub valve end 
               
               
                   
                 86 
                 High pressure fluid seal 
               
               
                   
                 88a-88b 
                 Velocity bypass valve ports 
               
               
                   
                 90 
                 Velocity bypass valve spring 
               
               
                   
                 92 
                 Velocity bypass valve jet nozzle 
               
               
                   
                 94a, 94b 
                 Cap screws 
               
               
                   
                 96 
                 Lower end cap 
               
               
                   
                   
               
            
           
         
       
     
       FIG.  1    is a perspective view of one embodiment of the straddle packer  10  with fluid pressure packer set in accordance with the invention in the run-in condition. The straddle packer  10  has a multicomponent mandrel  11 , the majority of which can only be seen in a cross-sectional view (see  FIG.  2   ). The multicomponent mandrel  11  extends from the uphole end to the downhole end of the straddle packer  10 . On the uphole end of the multicomponent mandrel  11 , a completion string connection component  12  includes a completion string connection  14  (best seen in  FIGS.  2  and  4   ). A configuration of the completion string connection  14  is a matter of design choice and dependent on whether the straddle packer  10  is to be operated using a coil tubing string (not shown) or jointed tubing string (not shown), as is well understood in the art. 
     The completion string connection component  12  has an upper packer element compression shoulder  15  and an upper packer element sleeve  16  (see  FIGS.  2  and  4   ) that supports an elastomeric upper packer element  18 , the function of which will be explained below with reference to  FIG.  4   . On a downhole side of the upper packer element  18  is an upper compression bell  20  having an upper compression bell shoulder  23  for compressing the upper packer element  18 . The upper compression bell  20  slides over the upper element packer sleeve  16 , as will be explained below with reference to  FIG.  4   . An upper sliding sleeve  24  is connected to a downhole side of the upper compression bell  20 . The upper sliding sleeve  24  is connected to an upper sliding sleeve coupling  26 , which is in turn connected to a female coupling end  27  of a slotted sliding sleeve  28 . In one embodiment, the slotted sliding sleeve  28  has four slotted sliding sleeve finger components  29   a - 29   d , two of which,  29   a ,  29   d , can be seen in this view. The slotted sliding sleeve finger components  29   a - 29   d  define four slots that respectively expose at least one mandrel flow sub nozzle of a mandrel flow sub  30 . In this embodiment, the mandrel flow sub  30  has a plurality of mandrel flow sub nozzles,  32   a - 32   h  (only  32   a  and  32   b  are visible in this view—better seen in  FIGS.  3   a  and  3   b   ). It should be understood the number of mandrel flow sub nozzles is a matter of design choice. It should also be understood that a size and shape of the at least one mandrel flow sub nozzle is a matter of design choice and that it may be permanent or interchangeable and any one of, but not limited to, a bore and a slot or any combination thereof. A downhole end of the sliding sleeve finger components  29   a - 29   d  are threadedly connected to a slotted sliding sleeve captured end coupling ring  38  that surrounds a lower sliding sleeve coupling  34  (see  FIG.  2   ) that is threadedly connected to a lower sliding sleeve  36 . A downhole end of the lower sliding sleeve  36  is connected to a sleeve/cylinder crossover  50  that is in turn connected to a modular pressure cylinder  48  assembled by interconnecting a plurality of pressure cylinder modules,  54   a - 54   d  in this embodiment. The pressure cylinder module  54   d  is connected to a lower compression bell  64  that slides over a lower packer element mandrel sleeve component  72  (see  FIGS.  2  and  4   ) of the multicomponent mandrel  11 , which supports an elastomeric lower packer element  74 . Connected to the lower packer element mandrel sleeve component  72  is a lower crossover sub  76  having a lower packer element compression shoulder  78 . In one embodiment a velocity bypass sub  82 , which will be explained below with reference to  FIGS.  5   a  and  5   b   , is connected to a downhole side of the lower crossover sub  76 . A lower end cap  96 , which caps the downhole end of the multicomponent mandrel  11 , is connected to the lower crossover sub  76  or the velocity bypass sub  82  when the velocity bypass sub  82  is incorporated into the straddle packer  10 . 
       FIG.  2    is a cross-sectional view of the straddle packer  10  shown in  FIG.  1    in the run-in condition, in which the upper packer element  18  and lower packer element  74  are in a relaxed, unset condition suitable for moving the straddle packer  10  to a desired location in a wellbore. As explained above, the slotted sliding sleeve  28  is connected to the lower sliding sleeve  36  by the lower sliding sleeve coupling  34 , which is threadedly connected to both the slotted sliding sleeve  28  and the lower sliding sleeve  36 , The slotted sliding sleeve captured end coupling ring  38  that covers the lower sliding sleeve coupling is likewise threadedly connected to the slotted sliding sleeve  28 . Rotation of the slotted sliding sleeve captured end coupling ring  38  is inhibited by cap screws  40   a ,  40   b.    
     As explained above, the elastomeric upper packer element  18  is supported on the upper packer element sleeve  16  of the completion string connection component  12  of the multicomponent mandrel  11 . The multicomponent mandrel  11  has a central passage  13  that provides an uninterrupted fluid path through the multicomponent mandrel  11 . The multicomponent mandrel  11  includes the following interconnected components: the completion string connection component  12 , which is threadedly connected to an upper mandrel tube  22 ; the mandrel flow sub  30  connected to a downhole end of upper mandrel tube  22 ; the wear-resistant, replaceable mandrel flow sub nozzle(s), in this embodiment  32   a - 32   h  (only 6 of which,  32   a - 32   b ,  32   c - 32   d  and  32   e - 32   f , are visible in this view); a lower mandrel tube  42  connected to a downhole end of the mandrel flow sub  30 ; a mandrel tube crossover component  44  connected to a downhole end of the lower mandrel tube  42 ; an active mandrel tube component  46  that supports the modular pressure cylinder  48  is connected to a downhole end of the mandrel tube crossover component  44 ; the lower packer element mandrel sleeve component  72  connected to a downhole end of the active mandrel tube component  46 ; the lower crossover sub  76  connected to the downhole end of the lower packer element mandrel sleeve component  72 ; and the optional velocity bypass sub  82  connected to a lower crossover sub male connector  80  of the lower crossover sub  76 . 
     In one embodiment the velocity bypass sub  82  has a threaded downhole end  83  to permit the connection of another downhole tool or, in this embodiment, a lower end cap  96  that caps the central passage  13  of the multicomponent mandrel  11  and prevents debris from entering the velocity bypass sub  82  and the central passage  13  if the straddle packer  10  is run into a downhole proppant plug, or other debris in a wellbore. In an alternate embodiment the lower end cap  96  is connected directly to the lower crossover sub  76 . 
     The active mandrel tube component  46  slidably supports the respective pressure cylinder modules  54   a - 54   d  of the modular pressure cylinder  48 . As explained above, the number of pressure cylinder modules used in the straddle packer  10  is a matter of design choice, but four modules has been found to be appropriate for many applications. If the number of pressure cylinder modules is changed, a length of the active mandrel tube component  46  is modified accordingly, as will be readily understood by those skilled in the art. In this embodiment, the active mandrel tube component  46  has two active mandrel tube fluid ports (collectively  49   a - 49   h ) that provide fluid communication between the central passage  13  and each of the respective pressure cylinder modules  54   a - 54   d . Active mandrel tube axial grooves  53   a - 53   d  respectively ensure fluid communication with the respective pressure cylinder modules Ma- 54   d  regardless of a relative rotation of the active mandrel tube component  46  with respect to the modular pressure cylinder  48 . The active mandrel tube axial grooves  53   a - 53   d  also ensure fluid communication between the central passage  13  and the respective pressure cylinder modules  54   a - 54   d  when the straddle packer  10  is shifted from the run-in condition the to set condition shown in  FIG.  4   . 
     In this embodiment, each of the pressure cylinder modules  54   a - 54   d  are identical and each pressure cylinder module  54   a - 54   d  respectively includes the following components: a pressure cylinder wall  55   a - 55   d ; a pressure piston  56   a - 56   d  with respective pressure piston seals  66   a - 66   d  that respectively seal against an inner surface of the respective pressure cylinder walls  55   a - 55   d ; each pressure piston  56   a - 56   d  reciprocates within a pressure cylinder chamber  59   a - 59   d ; pressure cylinder seals  67   a - 67   d  respectively inhibit the migration of fluid out of the respective pressure cylinder chambers  59   a - 59   d ; each pressure piston  56   a - 56   d  has a pressure cylinder male coupling sleeve  58   a - 58   d  and a pressure cylinder female coupling sleeve  60   a - 60   d ; in one embodiment the respective pressure cylinder male coupling sleeves  58   b - 58   d  may have an external thread that engages an internal thread in the respective pressure cylinder female coupling sleeves  60   a - 60   c  to connect the respective pressure pistons  56   a - 56   d  together, in another embodiment the respective cylinder modules  54   a - 54   d  are overlapped as shown but not threadedly connected and held together by compression between the upper packer element  18  and the lower packer element  74 ; respective pressure cylinder coupling seals  68   b - 68   d  inhibit any migration of fluid between the pressure cylinder male coupling sleeves  58   b - 58   d  and the pressure cylinder female coupling sleeves  60   a - 60   c ; pressure cylinder fluid ports  57   a - 57   h  let the high pressure fluid flow through active mandrel tube fluid ports  49   a - 49   h  into the respective pressure cylinder chambers  59   a - 59   d ; pressure cylinder pressure equalization ports  52   a - 52   j  in the respective cylinder walls  55   a - 55   d  equalize pressure behind the respective pressure pistons  56   a - 56   d  with ambient wellbore pressure. In one embodiment the active mandrel tube fluid ports  49   a - 49   h  and the pressure cylinder pressure equalization ports  52   a - 52   j  are provided with high pressure fluid filters (for example, sintered metal filters that known in the art (not shown)) that permit fluid to pass through the respective active mandrel tube fluid ports  49   a - 49   h  and pressure cylinder pressure equalization ports  52   a - 52   j  but inhibit particulate matter from migrating into the respective pressure cylinder chambers  59   a - 59   d.    
     A pressure cylinder crossover sleeve  62  caps the pressure cylinder male coupling sleeve  58   a  of the pressure cylinder module  54   a . A pressure cylinder crossover sleeve seal  69  provides a fluid seal between the pressure cylinder crossover sleeve  62  and the active mandrel tube component  46 , and a pressure cylinder coupling seal  68   a  provides a fluid seal between the pressure cylinder crossover sleeve  62  and the pressure cylinder male coupling sleeve  58   a . The pressure cylinder female coupling sleeve  60   d  is threadedly connected to a lower compression bell male coupling sleeve  70 . A pressure cylinder coupling seal  68   e  provides a high pressure fluid seal between the pressure cylinder female coupling sleeve  60   d  and the lower compression bell male coupling sleeve  70 . A compression bell seal  66   j  prevents the migration of fluid between the lower compression bell male coupling sleeve  70  and the active mandrel tube component  46 . 
     When high pressure fluid is pumped into the straddle packer  10 , the modular pressure cylinder  48  compresses the upper packer element  18  and the lower packer element  74  to isolate a section of the wellbore between the two packer elements  18 ,  74  after a pumped fluid rate exceeds a flow rate of the flow sub nozzle(s)  32   a - 32   h . If the optional velocity bypass sub  82  is present, the modular pressure cylinder  48  compresses the upper packer element  18  and the lower packer element  74  to isolate a section of the wellbore between the two packer elements  18 ,  74  after the velocity bypass valve closes, as will be explained below in detail with reference to  FIG.  4   . 
       FIG.  3   a    is an exploded cross-sectional view of mandrel tubes  22 ,  42  and mandrel flow sub  30  of the straddle packer  10  shown in  FIG.  2   . As explained above, the upper mandrel tube  22  is threadedly connected to the mandrel flow sub  30 . In this embodiment, the mandrel flow sub  30  has eight replaceable mandrel flow sub nozzles  32   a - 32   h , though the number of mandrel flow sub nozzles is a matter of design choice. The lower mandrel tube  42  is threadedly connected to the downhole side of the mandrel flow sub  30 . 
       FIG.  3   b    is an exploded side elevational view of the mandrel tubes  22 ,  42  and the mandrel flow sub  30  shown in  FIG.  3   a   . In this embodiment, the mandrel flow sub  30  is generally cylindrical but has four spaced apart axial mandrel flow sub grooves  31  in a top surface thereof that respectively receive one of the slotted sliding sleeve finger components  29   a - 29   d  (see  FIG.  3   c   ). When the slotted sliding sleeve  28  is slid over the mandrel flow sub  30 , a top surface of the sliding sleeve finger components is flush with outer surfaces of the mandrel flow sub  30 , as can be seen in  FIGS.  2  and  4   . 
       FIG.  3   c    is an exploded cross-sectional view of sliding sleeves  24 ,  28 ,  36  that reciprocate, from the run-in condition to the upper packer set condition and back to the run-in condition, on the upper mandrel tube  22 , the mandrel flow sub  30  and the lower mandrel tube  42  shown in  FIG.  3   b   . The upper sliding sleeve  24  slides over the upper mandrel tube  22 . As explained above, the upper sliding sleeve  24  is threadedly connected by upper sliding sleeve thread connection  25  to the upper sliding sleeve coupling  26 . The upper sliding sleeve coupling  26  is in turn threadedly connected to the slotted sliding sleeve female coupling end  27  of the slotted sliding sleeve  28 . The slotted sliding sleeve finger components  29   a - 29   d  (only  29   b  and  29   c  are visible in this view) are threadedly connected by a slotted sleeve coupling thread  33   a  to a lower sliding sleeve coupling upper thread  34   a . The lower sliding sleeve  36  is threadedly connected to the lower sliding sleeve coupling  34  by a lower sliding sleeve coupling lower thread  34   b  that engages a lower sliding sleeve threaded connection  37 . As explained above, the slotted sliding sleeve captured end coupling ring  38  covers the lower sliding sleeve coupling  34  and threadedly engages the slotted sliding sleeve captured end thread  33 . After the slotted sliding sleeve captured end coupling ring  38  is fully threaded onto the slotted sleeve captured end thread  33  of the slotted sliding sleeve  28 , the cap screws  40   a ,  40   b  are tightened to inhibit rotational movement. 
       FIG.  4    is a cross-sectional view of the embodiment of the straddle packer  10  shown in  FIG.  1    in the packer set condition. All of the components of the straddle packer  10  have been explained with reference to  FIGS.  1 - 3   , with the exception of some of the parts of the velocity bypass sub  82 , which will be explained below with reference to  FIGS.  5   a  and  5   b   , and that explanation of those parts will not be repeated, except insofar as is necessary to describe the functioning of the straddle packer  10 . 
     As explained above, when high pressure fluid is pumped into the straddle packer  10 , it exits through the mandrel flow sub nozzle(s)  32   a - 32   h  and, if the optional velocity bypass sub  82  is present, the velocity bypass valve jet nozzle  92  and velocity bypass valve ports  88   a ,  88   b  of the open velocity bypass valve  84  (see  FIG.  2   ) until the pump rate exceeds a threshold pump rate predetermined by an orifice size of the velocity bypass valve jet nozzle  92 . In one embodiment, the threshold pump rate is, for example, about 3 bbl/minute. When the threshold pump rate is exceeded, the velocity bypass valve  84  is forced close, as shown in this view, and fluid flow through velocity bypass valve ports  88   a ,  88   b  ceases. When fluid flow through the velocity bypass sub  82  ceases, fluid pressure rapidly builds within the central passage  13  of the multicomponent mandrel  11  because the rate of discharge from the central passage  13  is throttled by the mandrel flow sub nozzle(s)  32   a - 32   h . Consequently, the high pressure fluid is forced through the active mandrel tube fluid ports  49   a - 49   h  and flows through the pressure cylinder fluid ports  57   a - 57   h  of the respective pressure cylinder modules  54   a - 54   d  and into the respective pressure cylinder chambers  59   a - 59   d . As explained above with reference to  FIG.  2   , in one embodiment the pressure pistons  56   a - 56   d  are connected to the lower compression bell  64 , and the pressure cylinder walls  55   a - 55   d  are connected to the interconnected sliding sleeves (lower sliding sleeve  36 , slotted sliding sleeve  28  and upper sliding sleeve  24 ), which are in turn connected to the upper compression bell  20 . The high pressure fluid forced into the respective pressure cylinder chambers  59   a - 59   d  simultaneously urges the pressure pistons  56   a - 56   d  and the pressure cylinder walls  55   a - 55   d  in opposite directions along an axis of the active mandrel tube component  46 . Since the opposite ends of the straddle packer  10  are immovably connected to the multicomponent mandrel  11 , the upper compression bell  20  is urged to slide over the upper packer element sleeve  16  by the movement of the pressure cylinder walls  55   a - 55   d , and the lower compression bell  64  is urged to slide over the lower packer element mandrel sleeve component  72  by the movement of the pressure pistons  56   a - 56   d . The upper compression bell  20  compresses the upper packer element  18  and the lower compression bell  64  compresses the lower packer element  74  into respective sealing contact with a wellbore. As the upper compression bell  20  slides over the upper packer element sleeve  16 , pressure within the upper compression bell  20  is equalized by fluid passing through upper compression bell pressure equalization ports  21   a ,  21   b . Likewise, as the lower compression bell  64  slides over the lower packer element, mandrel sleeve component  72 , pressure within the lower compression bell  64  is equalized by fluid passing through lower compression bell pressure equalization ports  65   a ,  65   b . In one embodiment the pressure equalization ports  21   a ,  21   b  and  65   a ,  65   b  are all provided with particulate filters (not shown) to inhibit the migration of solids into the respective upper compression bell  20  and the lower compression bell  64 . As understood by those skilled in the art, the higher the fluid pressure of the high pressure fluid, the greater the compression of the upper packer element  18  and the lower packer element  74 . 
     After the pumping of the high pressure fluid is completed and pumping stops, the high pressure fluid may or may not continue to flow through the mandrel flow sub nozzle(s)  32   a - 32   h . If the optional velocity bypass sub  82  is present, once the rate of flow of the high pressure fluid drops below the predetermined threshold, the velocity bypass valve  84  opens and fluid rapidly drains from the central passage  13 , which drains the respective pressure cylinder chambers  59   a - 59   d . As the pressure cylinder chambers  59   a - 59   d  are drained, the upper packer element  18  and the lower packer element  74  return to the relaxed condition, which urges the pressure cylinder walls  55   a - 55   d  and the pressure pistons  56   a - 56   d  back to the run-in condition seen in  FIG.  2   . The straddle packer  10  can then be moved to another location in the wellbore or removed from the well. 
       FIG.  5   a    is a cross-sectional view of the velocity bypass sub  82  of the straddle packer  10  shown in  FIGS.  1 ,  2   , with the velocity bypass valve  84  in the open, run-in condition. In order to permit assembly and servicing of the velocity bypass valve  84 , the velocity bypass sub  82  is constructed in two parts, a velocity bypass sub connector end  85   a  that threadedly connects to the lower crossover sub male connector  80  of the lower crossover sub  76 ; and, a velocity bypass sub valve end  85   b  that threadedly connects to the velocity bypass sub connector end  85   a . Cap screws  94   a ,  94   b  inhibit rotation of the velocity bypass sub valve end  85   b  with respect to the velocity bypass sub connector end  85   a . A velocity bypass valve spring  90  constantly urges the velocity bypass valve  84  to the open condition. A high pressure seal  86  inhibits fluid migration around the velocity bypass valve  84 . As explained above, in the open position high pressure fluid flows through a replaceable velocity bypass valve jet nozzle  92  and out through the open velocity bypass valve ports  88   a ,  88   b . A nozzle size of the velocity bypass valve jet nozzle  92  determines a threshold rate of flow required to overcome the resilience of the velocity bypass valve spring  90  to force the velocity bypass valve  84  to the closed condition shown in  FIG.  5     b.    
       FIG.  5   b    is a cross-sectional view of the velocity bypass sub  82  of the straddle packer  10  shown in  FIG.  4   , when the straddle packer  10  is in the set condition or in transition to or from the set condition. As can be seen, the velocity bypass valve  84  has been urged, by a rate of high pressure fluid flow that exceeds the threshold determined by the velocity bypass jet nozzle  92 , to the closed condition in which high pressure fluid no longer flows through the velocity bypass valve ports  88   a - 88   b . In this condition of the velocity bypass valve  84 , the high pressure fluid sets the upper packer element  18  and the lower packer element  74 , as explained above in detail. 
     The explicit embodiments of the invention described above have been presented by way of example only. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.