Patent Publication Number: US-2006016591-A1

Title: Apparatus and method for agitating reservoir while pumping

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims foreign priority based upon Canadian application serial no. 2,471,681, filed Jun. 18, 2004 and domestic priority from U.S. provisional application Ser. No. 60/692,214, filed Jun. 20, 2005. 
    
    
     BACKGROUND  
      In certain oil producing areas considerable sand, water and like impurities are present in the producing formation in addition to the desired oil. In such formations the sand can settle out of the reservoir, and block the flow of production fluid from the formation into the well casing. In addition the sand can settle on down-hole tools, anchors, tubing, pumps and the like and jam them in the well casing such that same cannot be removed.  
      Petroleum production fluid is also generally mixed with gas. Where gas concentrations are significant, pump performance can be reduced because the pump periodically draws gas instead of liquid, and then the pump heats because there is a lack of lubrication.  
      Present pumps simply pump the fluid from the reservoir at a desired rate, and are located at an elevation in the reservoir such that the production fluid enters the well fast enough to prevent the reservoir from being drawn down below the pump intake. Sand present in the production fluid at the intake is pumped to the surface, however sand concentrations at lower levels of the reservoir are typically higher than at the pump intake. Eventually the sand in the lower levels settles to the bottom of the reservoir and stays there.  
     SUMMARY OF THE INVENTION  
      It is an object of the present invention to provide a pump apparatus for agitating a reservoir that overcomes problems in the prior art.  
      In a first embodiment the invention provides an apparatus for agitating production fluid in an underground reservoir. The apparatus comprises a port adapter adapted for connection to a pump output and to an output conduit such that pumped fluid can pass through the port adapter to the output conduit. A bypass port is defined in a wall of the port adapter, and a circulating conduit is connected at an upper end thereof to the bypass port and has a lower end. At least one fastener is operative to secure the circulating conduit to a pump. A circulating nozzle is connected to the lower end of the circulating conduit, and the circulating nozzle comprises an orifice operative to restrict flow through the circulating conduit. The apparatus is configured such that when attached to a pump the circulating nozzle is in the reservoir when production fluid is being pumped, and such that production fluid flows up the output conduit and through the circulating conduit and circulating nozzle into the reservoir.  
      In a second embodiment the invention provides an apparatus for agitating production fluid in an underground reservoir and pumping the agitated production fluid to the surface. The apparatus comprises a pump having a pump intake at a lower end thereof and a pump output at an upper end thereof. A port adapter is connected at a lower end thereof to the pump output and defines a bypass port in a wall thereof. An output conduit is connected at a lower end thereof to an upper end of the port adapter and is connected at an upper end thereof to a surface facility. A circulating conduit is secured to the pump and is connected at an upper end thereof to the bypass port and has a lower end. A circulating nozzle is connected to the lower end of the circulating conduit and comprises an orifice operative to restrict flow through the circulating conduit. The apparatus is configured such that the pump intake and the circulating nozzle are in the reservoir when production fluid is being pumped, and such that production fluid flows up the output conduit to the surface facility and through the circulating conduit and circulating nozzle into the reservoir.  
      In a third embodiment the invention provides a method for agitating production fluid in an underground reservoir and pumping the agitated production fluid to the surface. The method comprises providing a pump having a pump intake at a lower end thereof and a pump output at an upper end thereof; connecting a lower end of a port adapter to the pump output and providing a bypass port in a wall of the port adapter; connecting an output conduit at a lower end thereof to an upper end of the port adapter and connecting an upper end of the output conduit to a surface facility; securing a circulating conduit to the pump and connecting the circulating conduit at an upper end thereof to the bypass port; connecting a circulating nozzle to a lower end of the circulating conduit and providing an orifice in the circulating nozzle operative to restrict flow through the circulating conduit; locating the pump intake and the circulating nozzle in the reservoir and operating the pump to pump production fluid up the output conduit to the surface facility, and to pump production fluid through the circulating conduit and circulating nozzle into the reservoir to agitate the reservoir.  
      The pump apparatus agitates the fluid in the reservoir by re-circulating a portion of the pumped fluid back into the reservoir. The re-circulated fluid agitates the fluid in the reservoir such that sand is continually mixed into the fluid and pumped to the surface rather than settling out and remaining in the reservoir. The agitation also promotes gas breakout, where the gas separates from the liquid and rises out of the reservoir, reducing the problems associated with gas in the production fluid.  
      The circulating nozzle is sized to suit the pump capacity, depth of well, type and viscosity of production fluid, and desired rate of flow from the reservoir to the surface. The flow through the circulating conduit plus the flow to the surface equal the pump output.  
      Rotating pumps are known whereby the speed of rotation can be varied to vary the pumping rate. For example a 100 liters per second (1/sec) pump may pump 100 l/sec at 1000 pounds per square inch (psi) at maximum speed. Pressure at the pump output down-hole is a factor of the volume being pumped to surface, and the distance to surface. Where it is desired to pump 50 l/sec to the surface, the pressure at the reservoir depth could be for example 500 psi, and the speed of the pump to achieve this can be calculated.  
      Adding the circulating conduit and nozzle of the invention, the pump speed will be increased such that the pump output down-hole is raised for example to 60 l/sec. It is desired to still maintain the flow of 50 l/sec to the surface, so the pressure at the pump output will remain at 500 psi, but the circulating nozzle will have a size that allows 10 l/sec to flow through the circulating conduit and circulating nozzle and back into the reservoir at that pressure of 500 psi. The pump still raises 50 l/sec to the surface, but also is re-circulating 10 l/sec though the circulating nozzle into the reservoir to agitate the reservoir.  
      In a given well it might be found that 10 l/sec provides satisfactory agitation and sufficient mixing of the sand with the fluid, as in the above example. The pump efficiency is reduced somewhat since it is pumping 60 l/sec but only 50 l/sec is getting to the surface, but in suitable conditions this will be seen as an acceptable expense for agitating the reservoir.  
      If it is then decided to increase the production rate of the well in the above example such that more fluid is pumped to surface, typically the pump speed would be increased. However the increased flow from the pump output will increase the pressure in the output conduit and at the port, such that flow through the circulating conduit and nozzle will increase. For example increasing the pump output to 70 l/sec might increase the pressure and thus the flow through the circulating conduit and nozzle to 15 l/sec, with only 55 l/sec getting to the surface. Thus one half of the increased output would be reaching surface, and the pump efficiency losses could be unacceptable.  
      If 10 l/sec through the circulating nozzle provides adequate agitation, the increase to 15/lsec may not provide sufficient benefits to overcome the loss of pump efficiency. As the pump speed is increased to 80 l/sec, the pressure at the pump output might increase such that the flow through the circulating nozzle increases to 22 l/sec, such that only 3 I/sec of the 10 l/sec increased pump output is reaching the surface.  
      Where it is desired in the above example to increase the flow to surface from 50 to 60 l/sec, it will generally be desirable to raise the pump and change the circulating nozzle to one with a smaller passageway, such that at the increased pressure present when the flow to the surface is 60 l/sec, flow through the nozzle is maintained at 10 l/sec, and pump output is 70 l/sec.  
      The proper circulating nozzle size can be calculated for a production fluid with given characteristics, pumped from a given depth at a given flow to surface. The circulating nozzle can be located at virtually any level in the reservoir. Where it is desired to agitate the reservoir to suspend sand in the production fluid so same is pumped to the surface, the circulating nozzle will generally be located below the pump intake. Where it is desired to agitate the reservoir to release gas from the production fluid the circulating nozzle will likely be located above the pump intake so that the agitated fluid is nearer the top of the production fluid so that the gas more readily escapes the fluid.  
      It is contemplated that the fluid passing through the circulating conduit and nozzle could also be used to drive a centrifuge that would aid in separating the gas from the liquid in the production fluid. 
    
    
     DESCRIPTION OF THE DRAWINGS  
      While the invention is claimed in the concluding portions hereof, preferred embodiments are provided in the accompanying detailed description which may be best understood in conjunction with the accompanying diagrams where like parts in each of the several diagrams are labeled with like numbers, and where:  
       FIG. 1  is a schematic side view of an embodiment of the invention;  
       FIG. 2  is a schematic cross-sectional side view of a port adapter for attachment to the pump output, and the connected output conduit to the surface, circulating conduit, and circulating nozzle;  
       FIG. 3  is a schematic cross-sectional side view of a circulating nozzle for use with the invention. 
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS  
       FIG. 1  schematically illustrates a conventional pump  2 . The illustrated pump  2  for example comprises a fixed stator and a rotating rotor mounted inside a housing. The pump capacity varies as the rotor speed increases or decreases.  
      The pump  2  pushes production fluid from the reservoir up through the output conduit  6  connected to the pump output at the top of the pump  2 . As illustrated in  FIG. 2 , a port adapter  8  is placed in the output conduit by threading it into the top of the pump  2  and then threading the output conduit  6  into the top of the port adapter  8 . The port adapter  8  includes an elbow  10  connected to a bypass port  9  defined in a wall of the port adapter  8 , and extending from one side of the port adapter  8  and having an outside end oriented downward.  
      A circulating conduit  12  is threaded into the outside end of the elbow  10  and extends downward alongside the pump  2  to a location in the reservoir outside the pump  2 . The circulating conduit  12  is securely fixed to the pump  2  with straps  18  or the like, and could also be secured to the anchor used conventionally to secure the pump  2  in a well casing. The circulating conduit  12  must be secure so that it does not vibrate or shake loose and be lost in the well. As indicated by the broken lines in  FIG. 1 , the length of the circulating conduit  12  can be adjusted so that the circulating nozzle  14  is located at virtually any level of the reservoir, either above the pump intake  20 , or below it in order to suit the particular situation.  
      A circulating nozzle  14  is threaded onto the bottom end of the circulating conduit  12 . Thus pumped fluid can either pass up the output conduit  6  to the surface, or into the circulating conduit  12 . The circulating nozzle  14  restricts flow through the circulating conduit  12 , such that, as indicated in  FIG. 2 , production fluid  36  flows both up the output conduit  6  and through the circulating conduit  12  and circulating nozzle  14  in proportions that can be adjusted to suit the particular situation by varying the size of the orifice through the circulating nozzle  14 .  
      By way of example, the pump  2  could have a capacity of 100 liters per second (1/sec) such that the pump  2  can pump 100 l/sec at 1000 pounds per square inch (psi) at maximum speed. Where it is desired to pump 50 l/sec to the surface, and the pressure at the reservoir depth is 500 psi, the speed of the pump  2  to achieve this can be calculated.  
      Adding the circulating conduit  12  and nozzle  14  of the invention, the pump speed will be increased from the 50 l/sec rate such that the pump output is raised for example to 60 l/sec at a down-hole pressure of 500 psi, and the circulating nozzle will have a size that at a pressure of 500 psi allows 10 l/sec to flow through the circulating conduit  12  and circulating nozzle  14  and back into the reservoir. The pump  2  still raises 50 l/sec to the surface requiring a down-hole pressure of 500 psi, but also is re-circulating 10 l/sec though the circulating nozzle  14  into the reservoir to agitate the reservoir.  
       FIG. 3  illustrates a particular configuration of the circulating nozzle  14  that uses a venturi arrangement to increase agitation of the production fluid in the reservoir. The primary orifice  30  has a diameter that is sized to allow the desired flow through the circulating nozzle  14  as discussed above. The lower orifice  32  is much larger increasing between the primary orifice  30  and the lower nozzle outlet, creating a lower pressure area  34  as pressurized production fluid  36  flows from the primary orifice  30  into the lower orifice  32 . The lower pressure area  34  will draw production fluid  36  from the reservoir through channels  38 , defined in walls of the circulating nozzle  14  below the primary orifice  30  and above the nozzle outlet, and increase agitation of the reservoir by creating both a flow into the circulating nozzle  14  through the channels  38  and out of the circulating nozzle  14  through the lower orifice  32  and nozzle outlet.  
      The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous changes and modifications will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all such suitable changes or modifications in structure or operation which may be resorted to are intended to fall within the scope of the claimed invention.