Abstract:
A compressor free, generator free system production well for accelerated oil and gas removal from a reservoir using a magnetically coupled expander pump assembly, which include an outer expansion turbine that rotates around a pump. A magnetic coupling couples the expansion turbine to the pump. An inner portion of the magnetic coupling can be coupled to a pump shaft that drives the pump. An outer portion of the magnetic coupling can be driven by the expansion turbine, which rotates circumferentially around the pump. The expansion turbine drives the fluid to pump a driven fluid stream through the magnetic coupling. In this manner, flow directions of both driving and driven fluid streams remain separate and coaxial, thereby facilitating a reduction in an overall diameter of the expander pump assembly.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The current application is a Continuation in Part of co-pending International Patent Application Serial No.: PCT/US2014/023310 filed on Mar. 11, 2014, which is a Continuation of co-pending U.S. patent application Ser. No. 13/797,856 filed on Mar. 12, 2013, both entitled “MAGNETICALLY COUPLED EXPANDER PUMP WITH AXIAL FLOW PATH”. These references are hereby incorporated in their entity. 
    
    
     FIELD 
     The following disclosure relates to a pump arrangement and in particular, to a magnetically coupled expander pump with an axial flow path. 
     BACKGROUND 
     A need exists for a magnetically coupled, expander-driven pump, wherein the pumped fluid is able to flow through the center of a magnetic coupling. 
     The present embodiments meet this need. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description will be better understood in conjunction with the accompanying drawings as follows: 
         FIG. 1  shows a sectional view of a compressor free generator free production well for accelerated oil and gas removal from a reservoir according to one or more embodiments. 
         FIG. 2A  shows a sectional view of an expander pump unit according to one or more embodiments. 
         FIG. 2B  shows an exploded sectional view of a portion of the expander pump unit shown in  FIG. 2A  according to one or more embodiments. 
         FIG. 2C  shows an exploded sectional view of another portion of the expander pump unit shown in  FIG. 2A  according to one or more embodiments. 
     
    
    
     The present embodiments are detailed below with reference to the listed Figures. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Before explaining the present apparatus in detail, it is to be understood that the apparatus is not limited to the particular embodiments and that it can be practiced or carried out in various ways. 
     Magnetic couplings can have uses in various applications related to pumping fluids, particularly when isolation of the pumped fluid is desired. Typical magnetic coupling arrangements include disc (“face-to-face”) magnetic drive arrangements and coaxial canister-type coupling arrangements with axially aligned drive shafts which can be used to transfer torque to a completely isolated fluid path. In such typical arrangements, the fluid flow can be redirected in a perpendicular direction between inlet and outlet as it passes through the pump. However, there can be some applications in which such a redirection of the fluid flow is not desirable. 
     Some pumps with magnetic couplings can be driven by a motor. However, it can be possible for the driving torque to be provided by an expansion turbine. A pressurized working fluid can be fed into one annulus of a set of concentric pipes and allowed to build pressure as it flows down a geothermal power wellbore. Within the wellbore, heat can be added to the pressurized working fluid, and the hot, high pressure fluid then flows through an expander before returning to the surface in a lower density condition. The expansion of the pressurized working fluid can provide torque that can be used to drive the geothermal fluid pump. 
     Some prior art teaches a canister-type cylindrical magnetic coupling that can be used to transfer torque from the expander, which can be positioned vertically above the pump. The geothermal fluid in the well can feed the inlet of the pump in the center of the well, but the geothermal fluid can be discharged at the outlet of the pump in an essentially perpendicular direction with respect to the inlet direction, subsequently flowing up the well in the outer annulus. 
     In a first aspect of the prior art, an expander pump unit can be described in which an expander can be located surrounding the pump. A pressurized working fluid provided in the annulus surrounding a center pipe can flow through an expansion turbine (hereinafter referred to as an expander), causing it to rotate around the center pipe. The torque generated by the expander can be transferred to a rotating drive shaft, which can be coupled to the pump, in the middle of the center pipe via the use of an open-ended magnetic coupling. The pump can increase the pressure of a pumped fluid contained within the center pipe to move the pumped fluid axially through the pipe. 
     The magnetic coupling described herein can be comprised of outer and inner magnet-bearing cylinders, separated by a non-magnetic cylindrical wall that can be formed as a single unit or attached to the center pipe. The non-magnetic cylindrical wall can provide separation of the two fluid streams. The outer magnet-bearing cylinder can be integrated with the expander. The inner magnet-bearing cylinder can be connected to the pump shaft by rigid spokes around which fluid can pass. 
     This arrangement can be applicable to a system in which a pressurized working fluid can be used to drive a pump, and in which the allowable apparatus diameter may be limited. More specifically, the pumped stream flow path can be maintained in an axial direction, such as in a section of straight pipe, particularly as may be found in the wellbore for geothermal or oil and gas production. 
     In a second aspect, an expander pump unit is described, in which the pump can be disposed in a pipe, and the pump can be constructed to pump a first fluid. The expander pump unit can include an expander disposed in an annular space surrounding the pipe. The expander can be driven by a second fluid flowing in the annular space. The expander pump unit further can include the magnetic coupling comprising an inner rotating cylinder connected to the pump within the pipe and an outer rotating cylinder connected to the expander surrounding the pipe. The inner rotating cylinder can have open ends in fluid communication with the pump. 
     In a third aspect, an expander pump unit can be described, in which the expander pump unit can include a pump disposed in a pipe, and the pump can be constructed to pump a first fluid. The expander pump unit also can include a pump driver constructed to drive the pump. The expander pump unit can further include the magnetic coupling comprising the inner rotating cylinder connected to the pump within the pipe, and the outer rotating cylinder connected to the pump driver surrounding the pipe. The inner rotating cylinder can have open ends in fluid communication with the expander pump unit. 
     A benefit of this invention can be increased productivity to a well operator, associated with greater reliability of ThermalDrive vs. electric submersible pumps (ESP), e.g., reduced down time. 
     Other benefits can include reduced carbon footprint for operators by using the latent heat contained in the well vs. electricity. Using the latent heat contained in the well can (a) reduce operating costs to an operator associated with reductions in the parasitic load for pumping; (b) reduce maintenance costs to an operator associated with wire-line retrieval of the pump; and/or (c) reduce costs to a well operator due to co-generation of electricity at the surface (if the resource can be energetic enough) and provides supplemental income. 
     The term “exchange with the upwardly flowing working fluid” can refer to the physical replacement of a downwardly flowing working fluid in the annular space of the upwardly flowing working fluid. 
       FIG. 1  shows a sectional view of a compressor free generator free production well for accelerated oil and gas removal from a reservoir according to one or more embodiments. 
     A wellbore  200  can be formed through a formation  202 . 
     The well casing  105  can be installed in the wellbore  200 . 
     A wellhead  201  can be connected to the well casing  105 . 
     An outer pipe  106  can be installed in the well casing  105  and can be concentrically mounted within the well casing  105  forming a first annular space  400  between the well casing  105  and the outer pipe  106 . 
     An inner pipe  107  with an inner pipe axis  119  can be installed in the outer pipe  106  for conveying the production fluid  101  concentrically mounted within the outer pipe  106  forming a second annular space  402  between the outer pipe  106  and the inner pipe  107 . 
     A rotating expander  120  can be attached to one end of the inner pipe  107 . 
     The rotating expander  120  can be located between the inner pipe  107  and the outer pipe  106  for extracting energy from the downwardly flowing working fluid  102 . 
     The wellbore  200  can also include a pump  110  with a pump shaft  112  and a pump housing  140 . The pump  110  can connect to the inner pipe  107  for flowing or directing the flow of the production fluid  101  to the wellhead  201 . 
     The downwardly flowing working fluid  102  can feed the rotating expander  120  initially by flowing into a first annular space  400  in the well and then transferring into the second annular space  402  adjacent the production fluid to reach the rotating expander  120  becoming a supercritical fluid as hydrostatic pressure and heat is applied. 
     Upwardly flowing working fluid  103  can flow between the outer pipe  106  and the inner pipe  107  in the second annular space  402  contacting the inner pipe  107  to exchange heat with the production fluid  101 . 
     The upwardly flowing working fluid  103  can exit the rotating expander  120  into the first annular space  400  then flow to the wellhead  201  through the second annular space  402 . 
     A packer  108  can be used for sealing the space between the inner pipe  107  and the well casing  105 . 
     The compressor free, generator free system for the production well can provide accelerated oil and gas removal using heat exchanged with the production fluid  101  without expending energy from a compressor or a generator to perform the heat exchange. 
     A crossover  300  can be mounted between inner pipe  107  and the well casing  105  enabling the downwardly flowing working fluid  102  to exchange with the upwardly flowing working fluid  103  optimizing heat transfer between the production fluid  101  and the downwardly flowing working fluid  102  below the crossover  300  and the upwardly flowing working fluid above the cross over. 
       FIG. 2A  shows a sectional view of an expander pump unit according to one or more embodiments.  FIG. 2B  shows an exploded sectional view of a portion of the expander pump unit shown in  FIG. 2A  according to one or more embodiments.  FIG. 2C  shows an exploded sectional view of another portion of the expander pump unit shown in  FIG. 2A  according to one or more embodiments. 
     Referring to  FIGS. 2A-2C  the rotating expander  120  can be depicted with an outer wall  124  and a plurality of integral expander vanes  121 , which can be attached to the outer wall  124 . 
     The plurality of integral expander vanes  121  can convert a reduction of pressure in the downwardly flowing working fluid  102  into torque. 
     A retainer ring  129  can be depicted extending radially and outwardly from the inner pipe  107  toward the well casing  105  providing axial support for the rotating expander  120 . 
     Also shown is a pump pressure balance chamber  113  between the pump housing  140  formed around the pump  110   
     A disc  135  can be attached to an upper end of the pump shaft  112 , which can offset generated thrust produced by moving the production fluid  101  to the wellhead. 
     A labyrinth seal  141  can be interposed between the pump shaft  112  and the pump housing  140  to control the flow of the production fluid  101  into the pump pressure balance chamber  113 , wherein the pump pressure balance chamber  113  can be positioned between the rotating expander  120  and the outer pipe  106  and wherein the pump pressure balance chamber  113  can compensate for axial thrust from the pump  110 . 
     Embodiments depicted show an outer labyrinth seal  126  in the outer pipe  106 , which can be configured to flow the upwardly flowing working fluid  103  through fluid bearings  125  and into the first annular space between the outer pipe  106  and the inner pipe  107  towards an expander chamber valve  131  between the outer pipe  106  and the inner pipe  107 . 
     The expander chamber valve  131  can enable pressure of the upwardly flowing working fluid  103  to flow into an expander pressure balance chamber  130  of the rotating expander  120  and increase in pressure, exerting pressure simultaneously on an upper sealing flange  128  and a lower sealing flange  134  located between the outer pipe  106  and the inner pipe  107  opening the expander chamber valve  131  and moving the rotating expander  120  in a downward direction opposite the direction of flow of the upwardly flowing working fluid  103  flowing the downwardly flowing working fluid  102  into the first annular space formed between the outer pipe  106  and the inner pipe  107  above the rotating expander  120 . 
     The fluid bearings  125  can radially support the rotating expander. 
     The outer labyrinth seal  126  in the outer pipe  106  can be configured to flow the upwardly flowing working fluid  103  through the fluid bearings  125  between the outer pipe  106  and the inner pipe  107  towards the expander chamber valve  131  between the outer pipe  106  and the inner pipe  107 . 
     The expander chamber valve  131  can enable pressure of the upwardly flowing working fluid  103  to flow into the expander pressure balance chamber  130  of the rotating expander  120 , which can increase pressure in the expander pressure balance chamber  130  exerting pressure simultaneously on the upper sealing flange  128  and the lower sealing flange  134  located between the outer pipe  106  and the inner pipe  107  opening the expander chamber valve  131  and moving the rotating expander  120  in a downward direction opposite the direction of flow of the upwardly flowing working fluid into the first annular space formed between the outer pipe  106  and the inner pipe  107  above the rotating expander  120 . 
     In an embodiment, an inner labyrinth seal  127  attached to the rotating expander  120  can be used to bypass a portion of the upwardly flowing working fluid  103  around the rotating expander  120 . 
     The pump shaft  112  can extend through an inner rotating cylinder  115 . 
     The pump shaft  112  can have at least one spoke of a plurality of spokes  117 . Each spoke of the plurality of spokes can extend from the pump shaft  112  and can connect to the inner rotating cylinder  115 . 
     A hollow bore  139  can be formed in the pump shaft  112 . 
     The hollow bore  139  can be configured to flow a portion of the production fluid  101  from the pump pressure balance chamber  113  through an open pump chamber valve  136  around the disc  135  into the hollow bore  139 , whereupon the portion of the production fluid  101  can flow to a relatively low pressure below at least one of the plurality of spokes  117 . 
     In embodiments, the disc  135  can have a second upper seal  137  configured to seal against a sealing surface  138  attached to the pump housing  140 . 
     In embodiments, the expander chamber valve  131  can have a first upper seal  132  and a lower sealing surface  133 . 
     In embodiments, the pump  110  can pump the production fluid  101  coaxially with the inner pipe  107 . 
     In embodiments, a non-magnetic cylindrical wall  303  can separate an outer rotating cylinder  122  from an inner rotating cylinder  115 . 
     The non-magnetic cylindrical wall  303  can be configured for separating the upwardly flowing production fluid  101  from either the downwardly flowing working fluid  102  or the upwardly flowing working fluid  103 . 
     In embodiments of the compressor free, generator free system, a plurality of pump impellers  111  can be used in the pump  110 . 
     The plurality of pump impellers  111  can increase pressure of the production fluid  101  enabling the production fluid  101  to flow to the wellhead inside of the inner pipe  107 . 
     In embodiments, the pump  110  can be installable and retrievable through the inner pipe  107 . 
     It should be noted that the rotating expander pump unit  100  can be located below ground in a cased wellbore, such as the rotating expander pump unit can be used in a geothermal or oil and gas production well. The well casing  105  can separate a surrounding geologic formation from the production fluid  101  contained within the compressor free generator free production well. 
     The packer  108  can be used for sealing the space between the inner pipe  107  and the well casing  105 . 
     It should be noted that when arranged in the compressor free, generator free production well, the pump  110  can deliver the production fluid  101  upwardly from the producing formation to the surface. The production fluid  101  can flow through at least one of the plurality of spokes  117  internal to the inner rotating cylinder  115  before flowing into the pump  110 . As the production fluid  101  flows into the pump  110  it can be directed into the first of a plurality of pump impellers  111  which can increase the pressure of the production fluid  101 . Now at a higher pressure, the production fluid  101  can be able to flow to the surface inside the inner pipe  107 . 
     Axial support for the pump shaft  112  can be provided by a pump pressure balance chamber  113 , as shown in greater detail in  FIG. 2B . 
     It should be noted the second upper seal  137  can be constructed, for example, from a low friction material that can also withstand high temperatures. One suitable material for the second upper seal can include, but is not limited to polyether ether ketone (PEEK). Other suitable materials can be used within the scope of the invention. 
     At startup and when the pump  110  is not operating, the pump chamber valve  136  can be closed. During operation of the pump  110 , the plurality of pump impellers  111  and the pump shaft  112  can experience a thrust in a downward direction, opposite the direction of the production fluid  101  flow. The pump pressure balance chamber  113  can provide a means to offset the downward thrust so as to axially support the pump shaft  112 . 
     A portion of the production fluid  101 , shown by small solid arrows in  FIG. 2B , can flow past the labyrinth seal  141  into the pump pressure balance chamber  113 . The pressure of the production fluid  101  in the pump pressure balance chamber  113  can increase, exerting increased pressure between the pump housing  140  and the disc  135  tending to open the pump chamber valve  136  by moving the pump shaft  112  in an upward direction. The production fluid  101  flowing from the pump pressure balance chamber  113  through the open pump chamber valve  136  can subsequently proceed to flow around the disc  135  into the hollow bore  139  formed in the pump shaft  112 , whereupon the production fluid  101  can flow to the relatively low pressure pump suction below at least one of the plurality of spokes  117 , as shown in  FIG. 2C . 
     Also, during operation, as pressure in the pump pressure balance chamber  113  decreases, the pump chamber valve  136  can close, allowing the disc  135  and the pump shaft  112  to move axially downward. 
     It should be noted that the plurality of integral expander vanes  121  can convert the reduction of pressure in the upwardly flowing working fluid  103  into rotating torque. 
     The outer labyrinth seal  126  and the inner labyrinth seal  127  can be attached, respectively, to the outer wall  124  and the outer rotating cylinder  122  to control the flow of the upwardly flowing working fluid  103  bypassing the rotating expander  120 , as discussed in greater detail below. Fluid bearings  125 , which can include foil bearings, can be interposed between the outer wall  124  and the outer pipe  106  to radially support the rotating expander  120 . Axial support for the rotating expander  120  can be provided by the retainer ring  129 , extending radially inwardly from the inner pipe  107  and an expander pressure balance chamber  130 . 
     The expander pressure balance chamber  130  can be formed between the outer labyrinth seal  126 , the lower sealing flange  134  extending from the disc  135  of the outer wall  124 , and the upper sealing flange  128  extending inwardly from the outer pipe  106 . The upper sealing flange  128  can include a first upper seal  132 , which can be constructed to seal against a lower sealing surface  133  attached to the lower sealing flange  134 . The first upper seal  132  can be constructed, for example, from a low friction material that can also withstand high temperatures. 
     One suitable material for the seal can include but is not limited to polyether ether ketone (PEEK). Of course, other suitable materials exist and are within the scope of the invention. 
     At startup and when the rotating expander  120  is not operating, the expander chamber valve  131  can be open and the inner labyrinth seal  127  rests on the retainer ring  129 . During operation of the rotating expander  120  and the plurality of pump impellers  111  can experience a thrust in the direction of the upwardly flowing working fluid  103  flow tending to urge the lower sealing flange  134  upward so as to close the expander chamber valve  131 . The expander pressure balance chamber  130  can provide a means to offset the generated thrust. 
     A portion of the upwardly flowing working fluid  103 , shown by small solid arrows in  FIG. 2C , can flow between the outer labyrinth seal  126  and the outer pipe  106 , through the fluid bearings  125 , towards the expander chamber valve  131 . The pressure of the upwardly flowing working fluid  103  in the expander pressure balance chamber  130  can increase, exerting pressure on the upper sealing flange  128  and the lower sealing flange  134  tending to open the expander chamber valve  131  and thus moving the rotating expander  120  in a downward direction opposite the direction of flow of the upwardly flowing working fluid  103 . The downwardly flowing working fluid  102  flowing from the expander pressure balance chamber  130  through the open expander chamber valve  131  can subsequently proceed into the first annular space formed between the outer pipe  106  and the inner pipe  107 , above the rotating expander  120 . 
     Also, during operation, as pressure in the expander pressure balance chamber  130  decreases, the expander chamber valve  131  can close, allowing the rotating expander  120  to move axially upward. 
     The rotating expander  120  can have components shown including but not limited to a magnetic coupling  114  having the outer rotating cylinder  122  with a plurality of outer magnets  123 . 
     The outer rotating cylinder can rotate around the inner pipe  107  synchronously with the inner rotating cylinder  115 . 
     The inner rotating cylinder can have a plurality of inner magnets  116 . 
     In embodiments, the outer rotating cylinder  122  can be an inner wall of the rotating expander  120 . 
     One skilled in the art will recognize that aspects of the present invention can be applied in numerous different applications, whether downhole or above ground. For example, in an embodiment disclosed herein, torque can be provided to the outer portion of the magnetic coupling by a second pressurized working fluid stream. Other installations, particularly above ground, can instead provide a similar rotating torque to the outer rotating cylinder by different mechanical means, such as a gear drive or a belt and pulley system. Such an arrangement would allow for true in-line pumping of a completely isolated fluid. 
     In other embodiments, a different type of pump can be selected. The embodiment herein discloses the use of a centrifugal pump. However, other pumps requiring rotating torque can be substituted, such as a twin-screw pump. 
     One skilled in the art may also recognize that the relative location of the various key parts may be altered. For example, the expander may be axially offset from the outer rotating cylinder instead of the integrated design disclosed herein, or the relative axial locations of the pump and the magnetic coupling may be reversed. Also, in another embodiment, the flow direction of the pressurized working fluid may be reversed if it becomes advantageous to flow the pressurized working fluid downward in the annular space between the inner pipe and the outer pipe. 
     While these embodiments have been described with emphasis on the embodiments, it should be understood that within the scope of the appended claims, the embodiments might be practiced other than as specifically described herein.