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This application claims the priority of U.S. Provisional Patent Application Ser. No. 60/436,554 filed Dec. 26, 2002. 

   BACKGROUND OF THE INVENTION 
   1. Field of The Invention 
   This invention relates to the art of earth boring and crude petroleum production. More particularly, the invention relates to well annulus packer tools and methods for improving the efficiency of downhole operations 
   2. Description of Related Art 
   Packers and bridge plugs are devices for sealing the annulus of a borehole between a pipe string that is suspended within the borehole and the borehole wall (or casing wall). Hereafter, the term “packer” will be used as a generic reference to packers, bridge plugs or other such flow channel obstructions. The functional purpose of a packer is to obstruct the transfer of fluid and fluid pressure along the length of a well annulus. 
   Certain well completion procedures call for a conduit link to the surface independent of a primary workstring flowbore provided by drill pipe or coiled tubing. For example, certain chemical treatments are facilitated by an independent fluid conduit that is externally banded to the workstring as the workstring is lowered into a well. In another example, independent conduits that are externally banded to a workstring may provide hydraulic power fluid circulation conduits for downhole motors and other power tools. Another exemplary use for an external conduit could include a protective tubing sheath for electrical or fiber optic conduit. 
   When it is necessary to continue the continuity of such an external conduit past or below a packer, it is preferable for the packer construction to provide an internal by-pass channel for the conduit. Hence, the external conduit follows a course between the workstring flowbore and the radially expandable sealing gland of the packer. Above and below the packer sealing gland, connectors are provided for convenient attachment of the external conduit run. 
   Typically, inflation or compressive expansion of a packer sealing gland is accomplished by a fluid pressure elevation within the workstring flowbore. Such selectively applied fluid pressure within the flowbore is typically applied by closing off the flowbore. This is conventionally accomplished via a wireline conveyed plug, hydromechanical valve, or by setting a “disappearing” plug into the flowbore. Alternatively, the flowbore may be closed off by depositing a bore sealing element such as a dart or ball into the flowbore and either pumping or allowing gravity to carry the sealing element against a bore closure seat below the packer. When the sealing element, for example, a ball, engages the bore closure seat, pump pressure at the surface may be transferred down the flowbore to the packer engagement mechanism. Unfortunately, this procedure leaves the bore obstructed by the sealing element for subsequent operations. Although the obstruction may be avoided or accommodated, the obstruction presence creates additional complications. 
   Other typical packer expansion techniques include mechanical devices that set the packer seal by rotation or a selective push or pull. Although mechanically set packers are not normally used in conjunction with external conduit due to the angular or linear displacement of the supporting workstring, expansion and rotary transition joints may be used to transcend the obstacles thereby facilitating use of the invention to activate or operate other downhole tools such as valves in conjunction with mechanically set packers. 
   A system has been used previously that utilized an external fluid conduit safety valve line to actuate a packer as well as to close the safety valve. In this system, the safety valve was located uphole from the packer, and both the packer and safety valve were located relatively close to the surface (i.e., within a few hundred feet). This system used a relief valve that opened to set the packer after the safety valve was closed. Aside from this system, however, it has not been generally known to actuate a packer assembly using an external conduit that is used for chemical injection, motor control, or other independent well service function. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is a method for engaging a well packer in a workstring that carries an external conduit without obstructing the workstring flow bore. 
   Another object of the invention is provision of an apparatus that will permit dual use of a well workstring that supports an external conduit. 
   A further object of the invention is a dual use utility of an external conduit for hydraulically setting a packer and thereafter using the same external conduit for a separate or independent purpose. 
   Also an object of the invention is the capacity to set a fluid pressure actuated appliance in a well service string that carries an external conduit without obstructing the service string flow bore. 
   These and other objects of the invention as will be apparent from the detailed description to follow are realized from an external conduit secured to a well service string for an independent well service function. The external conduit may be obstructed to fluid flow by a calibrated rupture element a point downhole of a fluid flow junction for a conduit that is also connected to fluid pressure actuated appliance such as a packer. The independent function of the external conduit may be as a well treating chemical carrier or as a conduit for hydraulic power fluid. An external service conduit, usually routed through a packer mandrel, provides flow continuity past a packer gland for the external conduit between the uphole and downhole ends of the pipe string that supports the packer joint. The methods and device of the present invention permit such dual use operation even where the packer and other independent well service function are located thousands of feet below the surface of the well. 
   Well working circumstances giving rise to the necessity and use of such equipment may be simplified by a junction connection of the packer service conduit with a shunt conduit to the packer actuation chamber. Downstream of the junction connection, the service conduit or external conduit is closed; preferably by a pressure-relieved obstruction such as a rupture disc or pressure displaced piston valve. 
   When the well workstring is positioned as required, the packer is actuated by a pressure increase within the external conduit. Preferably, the packer actuation chamber is protected by a pressure responsive closure valve that closes the packer actuation chamber to fluid pressure above a predetermined value. 
   A fluid pressure increase in the external conduit above the packer setting pressure ruptures a calibrated disc or membrane thereby opening the pressure relieved obstruction and permitting the primary or independent use of the external conduit. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings in which like reference characters designate like or similar elements throughout the several figures of the drawing. 
       FIG. 1  is a schematic side, cross-sectional view of an exemplary wellbore containing a production assembly in accordance with the present invention with a packer device, safety valve and chemical injection system. 
       FIG. 2  illustrates the quarter section of a hydraulically set packer having an external conduit by-pass in accordance with the present invention. 
       FIG. 3  is a schematic side, cross-sectional view of an exemplary wellbore containing a production assembly in accordance with the present invention having a packer device and downhole motor. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows an exemplary wellbore  10  that has been drilled through the earth  12  to a hydrocarbon-producing formation  14 . In this instance, the formation  14  is in a late stage of its life and requires chemical injection treatment to assist continued production of hydrocarbons therefrom. A production assembly  15  is incorporated into a production string  16 , which is disposed within the wellbore  10 , extending downwardly from the surface (not shown) of the wellbore  10 . The production tubing string  16  defines an interior fluid flowbore  18  axially along its length. As is known in the art, the production tubing string  16  is made up of a series of production tubing sections that are secured in an end-to-end fashion. An annulus  20  is defined between the outer surface of the production tubing string  16  and the interior wall  22  of the wellbore  10 . 
   A number of subs and tools may be incorporated into the production tubing string  16 , as is well known. The production tubing string  16  includes a hydraulically-actuated subsurface safety valve  24  that is operable to close off flow of fluid through the interior fluid flowbore  18  upon actuation. Incorporated within the production tubing string  16  below the safety valve  20  is a packer assembly  26  for sealing off the annulus  20  against fluid flow and securing the production tubing string  16  within the wellbore  10 . The packer assembly  26  is shown in an unset, or running, position in  FIG. 1 . The structure and operation of the packer assembly  26  will be described in greater detail shortly. 
   An external fluid conduit  28  is disposed within the annulus  20  extending from the surface of the wellbore  10 . The external fluid conduit  28  is secured to the outer surface of the production tubing string  16  along its length by banding or the like. The fluid conduit  28  is operably interconnected (see fluid port  30 ) with the safety valve  24  for the delivery of fluid used to actuate the valve  24 . The fluid conduit  28  also passes through the packer assembly  26 , in a manner that will be described in greater detail shortly. The lower end  32  of the fluid conduit  28  provides a fluid outlet that is disposed proximate the formation  14  for delivery of chemical injection fluid to the formation  14 . 
   Referring to  FIG. 2 , the packer assembly  26  is shown in greater detail and apart from the other components of the production tubing string  16 . The packer assembly  26  includes a sealing element and an anchor slip mechanism between an upper collar  40  and a lower collar  42 . Secured between and to each of the collars is a tubular mandrel  44 . A cylindrical tube  46  has a sliding seal fit against the outer surface of the mandrel  44  but is immovably secured to the lower collar  42  by an assembly ring  48  having a threaded connection to both, the lower collar  42  and the cylindrical tube  46 . 
   A cylinder wall extension  50  from the cylindrical tube base has a greater inside diameter than the mandrel outside diameter to create an annular cylinder chamber  52  between the concentrically facing wall surfaces. Slidably disposed within the cylinder chamber  52  is an actuating piston  54 . The outer face of the piston  54  bears against an actuating ram  56 . 
   In sliding assembly between the actuating ram  56  and an abutment ledge on the upper collar  40  is a set of upper anchor slips  58 , a set of lower anchor slips  60  and a packer sealing element  62 . 
   Operatively, fluid pressure admitted to the cylinder chamber  52  displaces the actuating piston  54  against the ram  56 . Force of the displaced ram  56  compressively collapses the expanded slip and seal assembly to radially expand the anchor slip elements and the seal element against a casing or wellbore wall. 
   The external conduit  28  is connected to a by-pass service conduit  64  bored within the structural annulus of the mandrel  44 . A lower conduit sub  66 , connected to the lower outlet of the by-pass service conduit  64 , is also connected to a calibrated rupture element  68 . 
   The rupture element  68  has, for example, three flow ports: an inlet port connected to the lower conduit sub  66 ; a secondary outlet port connected to a packer setting shunt conduit  70 ; and a primary outlet port connected to the external conduit extension  72 . Specifically, the packer setting shunt conduit  70  is connected to the packer actuating chamber  52 . The flow channel of the shunt conduit  70  may also include a check valve  74  oriented to prevent reverse flow of fluid from the shunt conduit  70 . An open flow channel within the rupture element  68  links the inlet port  66  with the shunt conduit  70 . 
   Also within the rupture element  68 , is a calibrated flow barrier (rupture disc  76 ) between the inlet port  66  and the primary outlet port  72  that prevents fluid flow into the outlet port  72  until ruptured by a predetermined increase of pressure differential across the rupture element  68 . 
   In operation, the production tubing string  16  is provided with the external fluid conduit  28  for delivery of well treatment chemical and is positioned at the desired well depth for setting of the packer assembly  26 . Setting is caused by a first fluid pressure delivery of hydraulic fluid along the fluid conduit  28 . As the fluid pressure charge emerges from the mandrel by-pass conduit  64  into the rupture element  68 , the flow barrier  76  within the rupture element blocks the line flow from continuing along the primary external line  72 . Such flow is initially directed into the shunt conduit  70 . From the shunt conduit  70 , the pressurized fluid enters the pressure chamber  52  to drive the actuating piston  54  against the actuating ram  56 . Longitudinal displacement of the actuating ram  56  displaces the slips  58  and  60  radially outward to anchor the packer assembly  26  within the wellbore  10 . Continued compression of the packer assembly  26  expands the perimeter of the packer seal element  62  against the well wall  22  for isolation of the well annulus  20 . 
   In some cases, the shunt conduit  70  enters the pressure chamber  52  through a pressure limiting valve not shown. At a predetermined elevated pressure, the pressure limiting valve closes permanently to isolate the pressure chamber  52  from extreme pressure spikes. 
   Also at a predetermined pressure above the packer setting pressure, the flow barrier  76  in the rupture element  68  fails by a physical rupture. This rupture opens a direct flow channel from the lower conduit sub  66  into the external extension conduit  72 . Fluid within the pressure chamber  52  is isolated by the pressure limiting valve and/or the shunt conduit check valve  74 . Alternatively, the flow barrier  76  of the rupture element  68  may be ruptured by causing multiple cycles of pressure increases. Such a device might incorporate a bellows or an indexing mechanism which “counts” a number of pressure increase cycles before allowing fluid communication to begin. 
   Shunt conduit  70  and rupture element  68  are illustrated as dashed lines routed externally of the packer assembly body. This format is used for disclosure clarity. Those of ordinary skill will understand that the shunt conduit  70  and/or the rupture element  68  may be fabricated internally of either collar  40  or  42 . The shunt conduit  70  may be extended along the mandrel  44  laterally of the by-pass conduit  64 . 
   Once the packer assembly  26  is set, as described above, production stimulation chemicals are then pumped down the external fluid conduit  28  where they flow past the now set packer assembly  26  and exit the fluid outlet at lower end  32  where it commingles with the produced fluid within the lower portion of the wellbore  10 . The presence of the chemicals in the lower portion of the wellbore  10  helps to stimulate production from the formation  14 . Thus, it can be seen that the external fluid conduit  28  of the production assembly  15  provides a dual use in that it both sets that packer assembly  26  and is subsequently used for chemical stimulation of the formation. Additionally, the external fluid conduit  28  may be used to actuate the safety valve  24 , if necessary, by selectively directing fluid flow into the fluid inlet  30 . 
   Referring now to  FIG. 3 , there is shown an alternative production system  80  that is constructed in accordance with the present invention. In this system, the production tubing string  16  is provided with a packer assembly  26  and a hydraulically-actuated fluid pump  82 . A subsurface safety valve, such as the safety valve  24  described earlier, may or may not be present. The pump  82  is provided with a plurality of fluid inlets  84  for the intake of production fluid from the annulus  20  that is to be transmitted upwardly through the interior flowbore  18  of the production tubing string  16 . The external fluid conduit  28  is operatively associated with the fluid pump  82  to supply hydraulic fluid that will operate the pump  82 . The spent hydraulic fluid may be either expelled into the wellbore  10  or returned to the surface of the wellbore via a return fluid conduit (not shown). In operation, the pump  82  will draw fluid into the inlets  84  and pump it upward toward the surface of the wellbore  10 . 
   The production assembly  80  is operated to first set the packer assembly  26 , as described previously. When set, a second, greater level of fluid pressure is applied within the external fluid conduit  28  to supply hydraulic fluid to the pump  82  for operation of the pump  82 . The production assembly  80  is, therefore, also provided with an external fluid conduit that is capable of dual operable purposes within the wellbore  10 . 
   Although the invention has been described in terms of particular embodiments which are set forth in detail, it should be understood that this is by illustration only and that the invention is not necessarily limited thereto. Alternative embodiments and operating techniques will become apparent to those of ordinary skill in the art in view of the present disclosure. Accordingly, modifications of the invention are contemplated which may be made without departing from the spirit of the claimed invention.

Summary:
Fluid setting pressure is delivered to a hydraulically set well packer through an external conduit strapped to the exterior of a well workstring above the packer assembly. The continuity of the external conduit is continued past the packer assembly by following a flow channel along the mandrel sleeve thickness. Representatively, the external conduit may serve a primary well function other than packer setting (e.g. well chemical delivery). A calibrated rupture element in the external conduit is disposed to initially obstruct external conduit flow past the packer element. Consequently, fluid pressure transferred down the external conduit is first channeled to the packer setting pressure chamber. After setting, the fluid pressure in the external conduit is increased to rupture the calibrated element. When the external conduit flow channel is opened by rupture of the calibrated element, and the additional well service function may be accomplished.