Straddle packer with fluid pressure packer set and velocity bypass

Abstract

A straddle packer has a multicomponent mandrel with an active mandrel component. A pressure cylinder module reciprocates in opposite directions within a limited range over the active mandrel component. When fluid is pumped through a tubing string into the straddle packer, a piston of the pressure cylinder module is urged in one direction along an axis of the active mandrel component while a cylinder wall of the pressure cylinder module is urged in an opposite direction along the axis to simultaneously compress spaced-apart packers of the straddle packer to a packer set condition.

Claims

1. A straddle packer with fluid pressure packer set, comprising: a multicomponent mandrel that extends from an upper end to a lower end of the straddle packer, the multicomponent mandrel including an active mandrel tube component with active mandrel tube fluid ports that permit high pressure fluid to flow from a central passage of the multicomponent mandrel through the active mandrel tube component; an upper packer element and a lower packer element that respectively surround the multicomponent mandrel in a spaced apart relationship, the upper packer element and the lower packer element respectively being in a normally relaxed condition; and a pressure cylinder module that expands bi-directionally within a restricted range on the active mandrel tube component, the pressure cylinder module having a pressure cylinder wall and a pressure piston that reciprocates within a pressure cylinder, the pressure piston including pressure cylinder fluid ports that permit fluid flowing through the active mandrel tube fluid ports to enter the pressure cylinder and simultaneously urge the pressure cylinder wall and the pressure piston to move in opposite directions along an axis of the active mandrel tube component to compress the respectively normally relaxed upper and lower packer elements to a packer set condition.

2. The straddle packer as claimed in claim 1 wherein the multicomponent mandrel comprises: a completion string connection component which is threadedly connected to an upper mandrel tube; a mandrel flow sub connected to a downhole end of the upper mandrel tube; at least one mandrel flow sub nozzle in the mandrel flow sub; a lower mandrel tube connected to a downhole end of the mandrel flow sub; a mandrel tube crossover component connected to a downhole end of the lower mandrel tube; the active mandrel tube component connected to a downhole end of the mandrel tube crossover component; a lower packer element mandrel sleeve component connected to a downhole end of the active mandrel tube component; and, a lower crossover sub connected to a downhole end of the lower packer element mandrel sleeve component.

3. The straddle packer as claimed in claim 2 wherein the pressure cylinder module comprises: the pressure cylinder wall; the pressure piston with a pressure piston seal that seals against an inner surface of the pressure cylinder wall; the pressure piston reciprocating within the pressure cylinder chamber; a pressure cylinder seal that inhibits a migration of fluid out of the pressure cylinder chamber; the pressure piston having a pressure cylinder male coupling sleeve and a pressure cylinder female coupling sleeve, a pressure cylinder fluid port to let the fluid flow through the active mandrel tube fluid ports into the pressure cylinder chamber; and a pressure cylinder pressure equalization port in the pressure cylinder wall to equalize pressure behind the pressure piston with ambient wellbore pressure.

4. The straddle packer as claimed in claim 3 further comprising a sliding sleeve that reciprocates over the multicomponent mandrel from an upper packer run-in condition to an upper packer set condition and back to the upper packer run-in condition when the pressure cylinder module is moved from the run-in condition to the packer set condition.

5. The straddle packer as claimed in claim 4 wherein the sliding sleeve comprises: an upper sliding sleeve connected to an upper compression bell that slides over a downhole end of an upper packer element sleeve of the completion string connection component, the upper sliding sleeve sliding over the upper mandrel tube; a slotted sliding sleeve connected to a downhole end of the upper sliding sleeve, the slotted sliding sleeve sliding over the mandrel flow sub and having slotted sliding sleeve finger components that define slots that expose the at least one mandrel flow sub nozzle; and, a lower sliding sleeve connected to a downhole end of the slotted sliding sleeve, a downhole end of the lower sliding sleeve being connected to sleeve/cylinder crossover that is connected to the pressure cylinder wall of the pressure cylinder module.

6. The straddle packer as claimed in claim 3 wherein the pressure piston female coupling sleeve is connected to a lower compression bell male coupling sleeve of a lower compression bell that reciprocates over an uphole end of the lower packer element mandrel sleeve component of the multicomponent mandrel, the lower packer element mandrel sleeve component supporting the lower packer element and the lower compression bell reciprocating from a lower packer run-in condition to a lower packer set condition and back to the lower packer run-in condition when the pressure cylinder module is moved from the run-in condition to the packer set condition.

7. The straddle packer as claimed in claim 2 wherein the completion string connection component comprises a completion string connection for connecting a tubing string to the straddle packer.

8. The straddle packer as claimed in claim 2 wherein the completion string connection component comprises an upper packer compression shoulder and an upper packer element sleeve that supports the upper packer element.

9. The straddle packer as claimed in claim 2 further comprising a velocity bypass sub connected to the lower crossover sub, the velocity bypass sub comprising a velocity bypass valve having a velocity bypass jet nozzle; a velocity bypass valve spring that urges the velocity bypass valve to an open condition; at least one velocity bypass fluid port through which high pressure fluid passes from the central passage of the multicomponent mandrel when the velocity bypass valve is in the open condition, whereby the velocity bypass valve is urged to a closed condition when the fluid, flow through the velocity bypass valve exceeds a fluid flow threshold governed by an orifice size of the velocity bypass jet nozzle.

10. The straddle packer as claimed in claim 9 wherein the velocity bypass jet nozzle is replaceable to adjust the fluid flow threshold.

11. The straddle packer as claimed in claim 9 further comprising a lower end cap connected to a downhole end of the velocity bypass sub.

12. A straddle packer with fluid pressure packer set and velocity bypass, comprising: a multicomponent mandrel having a central passage that extends from an upper end to a lower end of the multicomponent mandrel, the multicomponent mandrel having a completion string connection mandrel component at an upper end of the straddle packer to permit the connection of a tubing string to the straddle packer and a velocity bypass crossover at a lower end of the straddle packer to permit the connection of a velocity bypass sub; an upper packer element and a lower packer element that respectively surround the multicomponent mandrel in a spaced apart relationship; a pressure cylinder module that reciprocates within a restricted range on an active mandrel tube component of the multicomponent mandrel; an upper compression bell that compresses the upper packer element and a lower compression bell that compresses the lower packer element when fluid is pumped into the straddle packer at a flow rate that exceeds a flow rate threshold, the upper compression bell being connected to an upper end of a sliding sleeve that is connected by a crossover to the pressure cylinder wall of the pressure cylinder module, and the lower compression bell being connected the pressure piston of the pressure cylinder module; an upper and a lower mandrel tube of the multicomponent mandrel, the upper mandrel tube being connected on a top end to the completion string mandrel component and on a lower end to a mandrel flow sub, and an upper end of the lower mandrel tube being connected to a lower end of the mandrel flow sub and on a lower end to the active mandrel tube component of the multicomponent mandrel, the mandrel flow sub including at least one mandrel flow sub nozzle; and the velocity bypass sub having a central passage in fluid communication with the central passage of the multicomponent mandrel and housing a velocity bypass valve having the flow rate threshold, whereby fluid pumped through the completion tubing string into the multicomponent mandrel flows through the at least one mandrel flow sub nozzle and the velocity bypass valve until a flow rate of the fluid exceeds the flow rate threshold, after which the velocity bypass valve closes and the fluid flows only through the at least one mandrel flow sub nozzle and into fluid ports of the pressure cylinder module, urging the pressure piston in a first direction and the pressure cylinder wall in an opposite direction along an axis of the active mandrel tube component to compress the respective packer elements to a packer set condition.

13. The straddle packer as claimed in claim 12 wherein the multicomponent mandrel further comprises a mandrel tube crossover component connected to a downhole end of the lower mandrel tube; the active mandrel tube component being connected to a downhole end of the mandrel tube crossover component; a lower packer element mandrel sleeve component connected to a downhole end of the active mandrel tube component, the lower packer element mandrel sleeve supporting the lower packer element.

14. The straddle packer as claimed in claim 13 wherein the pressure piston female coupling sleeve is connected to a lower compression bell male coupling sleeve of the lower compression bell, the lower packer element mandrel sleeve component supporting the lower packer element; and the lower compression bell reciprocating over an uphole end of the lower packer element mandrel sleeve component from a lower packer run-in condition to a lower packer set condition and back to the lower packer run-in condition when the pressure cylinder module is urged from the run-in condition to the packer set condition.

15. The straddle packer as claimed in claim 12 wherein the pressure cylinder module comprises: the pressure cylinder wall; the pressure piston with a pressure piston seal that seals against an inner surface of the pressure cylinder wall; the pressure piston reciprocating within a pressure cylinder chamber; a pressure cylinder seal that inhibits the migration of fluid out of the pressure cylinder chamber; the pressure piston having a pressure cylinder male coupling sleeve and a pressure cylinder female coupling sleeve; a pressure cylinder fluid port to let the fluid flow through the active mandrel tube fluid ports into the pressure cylinder chamber; and, pressure cylinder pressure equalization ports in the pressure cylinder wall to equalize pressure behind the pressure piston with ambient wellbore pressure.

16. The straddle packer as claimed in claim 12 further comprising a lower end cap that caps a downhole end of the velocity bypass sub.

17. The straddle packer as claimed in claim 12 wherein the velocity bypass valve comprises a replaceable velocity bypass valve jet nozzle having an orifice that determines the flow rate threshold.

18. A straddle packer with fluid pressure packer set and velocity bypass, comprising: a multicomponent mandrel having a completion string connection component which is threadedly connected to an upper mandrel tube; a mandrel flow sub connected to a downhole end of upper Mandrel tube; at least one mandrel flow sub nozzle in the mandrel flow sub; a lower mandrel tube connected to a downhole end of the mandrel flow sub; a mandrel tube crossover component connected to a downhole end of the lower mandrel tube; an active mandrel tube component connected to a downhole end of the mandrel tube crossover component; a lower packer element mandrel sleeve component connected to a downhole end of the active mandrel tube component; a lower crossover sub connected to the downhole end of the lower packer element mandrel sleeve component; an upper packer element and a lower packer element that respectively surround the multicomponent mandrel in a spaced apart relationship; a pressure cylinder module that reciprocates within a restricted range on an active mandrel tube component of the multicomponent mandrel, the pressure cylinder module including: a pressure cylinder wall; a pressure piston with a pressure piston seal that seals against an inner surface of the pressure cylinder wall; the pressure piston reciprocating within a pressure cylinder chamber; a pressure cylinder seal that inhibits the migration of fluid out of the pressure cylinder chamber; the pressure piston having a pressure cylinder male coupling sleeve and a pressure cylinder female coupling sleeve; a pressure cylinder fluid port to let the high pressure fluid flow through the active mandrel tube fluid ports into the pressure cylinder chamber; and pressure cylinder pressure equalization ports in the pressure cylinder wall to equalize pressure behind the pressure piston with ambient wellbore pressure; an upper compression bell that compresses the upper packer element and a lower compression bell that compresses the lower packer element when high, pressure fluid is pumped into the straddle packer at a flow rate that exceeds a predetermined flow rate threshold, the upper compression bell being connected to an upper end of a sliding sleeve that is connected by a crossover to an upper end of the cylinder wall of the pressure cylinder module, and the lower compression bell being connected to a lower end of the pressure piston of the pressure cylinder module; an upper and a lower mandrel tube of the multicomponent mandrel, the upper mandrel tube being connected on an upper end to the completion string mandrel component and on a lower end to a mandrel flow sub, and an upper end of the lower mandrel tube being connected to a lower end of the mandrel flow sub and on a lower end to the active mandrel tube component of the multicomponent mandrel, the mandrel flow sub including at least one mandrel flow sub nozzle; and a velocity bypass sub connected to the velocity bypass sub crossover, the velocity bypass sub having a central passage in fluid communication with the central passage of the multicomponent mandrel and housing a velocity bypass valve having the flow rate threshold, whereby fluid pumped through the completion tubing string into the multicomponent mandrel flows through the at least one mandrel flow sub nozzle and the velocity bypass valve until the flow rate of the fluid exceeds the flow rate threshold, after which the fluid flows only through the at least one mandrel flow sub nozzle and into fluid ports of the pressure cylinder module, urging the pressure piston of the pressure cylinder module in a first direction and the pressure cylinder wall of the pressure cylinder module in an opposite direction along an axis of the active mandrel tube component, to compress the respective packer elements to a packer set condition.

19. The straddle packer as claimed in claim 18 further comprising a lower end cap that caps a downhole end of the velocity bypass sub.

20. The straddle packer as claimed in claim 18 wherein the velocity bypass valve comprises a replaceable velocity bypass valve jet nozzle having an orifice that determines the flow rate threshold.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, in which:

(2) 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;

(3) FIG. 2 is a cross-sectional view of the straddle packer shown in FIG. 1, in the run-in condition;

(4) FIG. 3a is an exploded cross-sectional view of mandrel tubes and mandrel flow sub of the straddle packer shown in FIG. 2;

(5) FIG. 3b is an exploded side elevational view of the mandrel tubes and the mandrel flow sub shown in FIG. 3a;

(6) FIG. 3c 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. 3b;

(7) FIG. 4 is a cross-sectional view of the embodiment of the straddle packer shown in FIG. 1 in the packer set condition;

(8) FIG. 5a 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

(9) FIG. 5b is a cross-sectional view of the velocity bypass sub of the straddle packer shown in FIG. 5a, with the velocity bypass valve of the velocity bypass, sub in a closed condition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(10) The invention provides a straddle packer with a fluid pressure boosted packer set and velocity bypass for use in precision well stimulation or remediation treatments in either open hole or cased wellbores (hereinafter referred to collectively as “wellbores”). The straddle packer has spaced-apart upper and lower packer elements that bracket a mandrel flow sub component of a multicomponent mandrel that extends from an upper end to a lower end of the straddle packer. The mandrel flow sub has at least one abrasion-resistant fluid nozzle used to inject well stimulation or well remediation fluid (hereinafter referred to collectively as “high pressure fluid”) into a section of a wellbore that is pressure isolated by the respective spaced-apart upper and lower packer elements when the respective packer elements are in a packer set condition. In this document, “flow sub nozzle” means any orifice, permanent or interchangeable, through which high pressure fluid may be pumped, including but not limited to a bore and a slot. In the packer set condition the respective upper and lower packer elements are in high pressure sealing contact with a wellbore. The respective upper and lower packer elements are compressed to the packer set condition by a pressure cylinder module that is activated by the high pressure fluid pumped through a tubing string connected to the straddle packer. The pressure cylinder module has a cylinder wall, a cylinder chamber and a piston that reciprocates within the cylinder chamber. High pressure fluid pumped through the tubing string enters the cylinder chamber via pressure cylinder fluid ports in a piston coupling sleeve. The high pressure fluid urges sliding sleeves connected to the piston and the cylinder wall in opposite directions along an axis of the multicomponent mandrel component, simultaneously compressing the upper and lower packer elements to the packer set condition. When the pumping of high pressure fluid is stopped, the upper and lower packer elements return to the run-in condition. The cylinder wall effectively doubles piston area, permitting the respective packer elements to be set using the single cylinder module. A velocity bypass valve on a downhole end of the straddle packer permits high pressure fluid to flow through the fluid nozzles and the velocity bypass valve so long as a rate of flow remains at or below a predetermined threshold rate of flow. This has the advantages of permitting the wellbore to be flushed in an area of the straddle packer to remove debris before the packers are set. It also permits the tool to rapidly depressurize and return to the run-in condition once high pressure fluid pumping has been terminated, minimizing a probability that the straddle packer will become “stuck in the hole”.

(11) TABLE-US-00001 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 Mandrelflow 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 49a-49b Active mandrel tube fluid ports 50 Sleeve/cylinder crossover 52a-52d Pressure cylinder pressure equalization ports 53 Active mandrel tube axial grooves 54 Pressure cylinder module 55 Pressure cylinder wall 56 Pressure piston 57a-57b Pressure cylinder fluid ports 58 Pressure cylinder male coupling sleeve 59 Pressure cylinder chamber 60 Pressure cylinder female coupling sleeve 62 Pressure cylinder crossover sleeve 64 Lower compression bell 65a, 65b Lower compression bell equalization ports 66 Pressure piston seal  66j Compression bell seal 67 Pressure cylinder seal 68a, 68b Pressure cylinder coupling seal 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

(12) 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 whale 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.

(13) 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 29a-29d, two of which, 29a, 29d, can be seen in this view. The slotted sliding sleeve finger components 29a-29d 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, 32a-32h (only 32a and 32b are visible in this view—better seen in FIGS. 3a and 3b). It should be understood the number, size and shape of mandrel flow sub nozzles is a matter of design choice. A downhole end of the sliding sleeve finger components 29a-29d 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 pressure cylinder module 54. The pressure cylinder module 54 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. 5a and 5b, 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.

(14) 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 40a, 40b.

(15) 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 32a-32h (only 6 of which, 32a-32b, 32c-32d and 32e-32f, 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 pressure cylinder module 54 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.

(16) 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.

(17) The active mandrel tube component 46 slidably supports the pressure cylinder module 54. The active mandrel tube component 46 has two active mandrel tube fluid ports 49a, 49b that provide fluid communication between the central passage 13 and the pressure cylinder module 54, Active mandrel tube axial grooves 53 ensure fluid communication between the central passage 13 and the pressure cylinder module 54 when the straddle packer 10 is shifted from the run-in condition the to set condition shown in FIG. 4.

(18) In this embodiment, the pressure cylinder module 54 includes the following components: a pressure cylinder wall 55; a pressure piston 56 with a pressure piston seal 66 that seals against an inner surface of the pressure cylinder wall 55; the pressure piston 56 reciprocates within a pressure cylinder chamber 59; a pressure cylinder seal 67 inhibits the migration of fluid out of the pressure cylinder chamber 59; the pressure piston 56 has a pressure cylinder male coupling sleeve 58 and a pressure cylinder female coupling sleeve 60; in one embodiment the pressure cylinder male coupling sleeve 58 may have an external thread that engages an internal thread in a pressure cylinder crossover sleeve 62, in another embodiment the pressure cylinder module 54 and the pressure cylinder crossover sleeve 62 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; a pressure cylinder coupling seal 68a inhibits any migration of fluid between the pressure cylinder male coupling sleeve 58 and the pressure cylinder crossover sleeve 62; pressure cylinder fluid ports 57a, 57b let the high pressure fluid flow through active mandrel tube fluid ports 49a, 49b into the pressure cylinder chamber 59; pressure cylinder pressure equalization ports 52a-52d in the pressure cylinder wall 55 equalize pressure within the pressure cylinder module 54 with ambient wellbore pressure. In one embodiment the active mandrel tube fluid ports 49a-49b and the pressure cylinder pressure equalization ports 52a-52d 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 49a-49b and pressure cylinder pressure equalization ports 52a-52d but inhibit particulate matter from migrating into the pressure cylinder chamber 59.

(19) The pressure cylinder crossover sleeve 62 caps the pressure cylinder male coupling sleeve 58 of the pressure cylinder module 54. 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. The pressure cylinder female coupling sleeve 60 is threadedly connected to a lower compression bell male coupling sleeve 70. A pressure cylinder coupling seal 68b provides a high pressure fluid seal between the pressure cylinder female coupling sleeve 60 and the lower compression bell male coupling sleeve 70. A compression bell seal 66j prevents the migration of fluid between the lower compression bell male coupling sleeve 70 and the active mandrel tube component 46.

(20) When high pressure fluid is pumped into the straddle packer 10, the pressure cylinder module 54 simultaneously 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) 32a-32h. If the optional velocity bypass sub 82 is present, the pressure cylinder module 54 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.

(21) FIG. 3a 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 32a-32h, though the number, size and shape 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.

(22) FIG. 3b is an exploded side elevational view of the mandrel tubes 22, 42 and the mandrel flow sub 30 shown in FIG. 3a. 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 29a-29d (see FIG. 3c). 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.

(23) FIG. 3c 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. 3b. 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 threaded 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 29a-29d (only 29b and 29c are visible in this view) are threadedly connected by a slotted sleeve coupling thread 33a to a lower sliding sleeve coupling upper thread 34a. The lower sliding sleeve 36 is threadedly connected to the lower sliding sleeve coupling 34 by a lower sliding sleeve coupling lower thread 34b that engages a lower sliding sleeve threaded connection 3T 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 40a, 40b are tightened to inhibit rotational movement.

(24) FIG. 4 is a cross-sectional view of the embodiment of the straddle packer 10 shown in FIG. 1 in the packer set condition. Each of the components of the straddle packer 10 has been explained above with reference to FIGS. 1-3, except for some of the components of the velocity bypass sub 82, which will be explained below with reference to FIGS. 5a and 5b, and that explanation of those parts will not be repeated, except insofar as is necessary to describe the functioning of the straddle packer 10.

(25) As explained above, when high pressure fluid is pumped into the straddle packer 10, it exits through the mandrel flow sub nozzle(s) 32a-32h and, if the optional velocity bypass sub 82 is present, the velocity bypass valve jet nozzle 92 and velocity bypass sub ports 88a, 88b 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 sub ports 88a, 88b 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) 32a-32h. Consequently, the high pressure fluid is forced through the active mandrel tube fluid ports 49a and 49b and flows through the pressure cylinder fluid ports 57a and 57b of the pressure cylinder module 54 and into the pressure cylinder chamber 59. As explained above with reference to FIG. 2, in one embodiment the pressure piston 56 is connected to the lower compression bell 64, and the pressure cylinder wall 55 is 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. When the high pressure fluid is forced into the pressure cylinder chamber 59, the active mandrel fluid ports 49a, 49b are fixed points from which the pressure piston 56 and the pressure cylinder wall 55 are simultaneously urged in opposite directions along an axis of the active mandrel tube component 46. The simultaneous and opposite directions of movement of the pressure piston 56 and the pressure cylinder wall 55 is balanced, and the packer element setting force generated by the pressure cylinder module 54 is double that of a comparable single cylinder with one fixed end. 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 wall 55, 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 piston 56. 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 21a, 21b. 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 65a, 65b. In one embodiment the pressure equalization ports 21a, 21b and 65a, 65b 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.

(26) 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) 32a-32h. 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 pressure cylinder chamber 59. As the pressure cylinder chamber 59 is drained, the upper packer element 18 and the lower packer element 74 return to an unset condition, which urges the pressure cylinder wall 55 and the pressure piston 56 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.

(27) FIG. 5a 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 85a that threadedly connects to the lower crossover sub male connector 80 of the lower crossover sub 76; and, a velocity bypass sub valve end 85b that threadedly connects to the velocity bypass sub connector end 85a. Cap screws 94a, 94b inhibit rotation of the velocity bypass sub valve end 85b with respect to the velocity bypass sub connector end 85a. 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 sub ports 88a, 88b. 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. 5b.

(28) FIG. 5b 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 sub ports 88a-88b. 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.

(29) 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,