Abstract:
A method and system capable of economically removing a liquid from a liquid reservoir, such as oil from an oil reservoir, by withdrawing limited quantities of the liquid in discrete steps. The system includes a dipping unit sized to be received in a passage to the reservoir, such as a casing of an oil well, and a unit for lowering and raising the dipping unit within the passage. The dipping unit is configured and oriented to have an upper end portion and a lower end portion when within the passage. The dipping unit includes a chamber, a feature for enabling a liquid to enter the chamber when at least its lower end portion is submerged in the liquid within the reservoir, and a feature for releasing the liquid from the chamber. In use, the dipping unit is lowered within passage to a liquid reservoir to enable liquid to flow into the chamber of the dipping unit when at least a lower end portion of the dipping unit is submerged in the liquid within the reservoir, and then raising the dipping unit within the passage so that the liquid is released from the chamber.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/785,153 filed Mar. 23, 2006, the contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention generally relates to equipment and methods for removing liquids from liquid reservoirs, for example, oil well recovery equipment and methods capable of economically removing oil from an oil field.  
         [0003]     An oil well is typically constructed to have a tubing within one or more casings that structurally support the wellbore and seal the wellbore (other than the tubing) at the surface, typically so that the pressure of the oil within the oil field is sufficient to force oil through the tubing to the surface. As an oil field is depleted, this pressure can drop to a sufficiently low level to necessitate the use of artificial lift methods and equipment, examples of which include downhole pumps, gas lifts, and surface pump-jacks. Such measures have been referred to as “secondary recovery” methods. However, because of the costs of typical lift equipment, secondary recovery methods are pursued only if the oil field is believed to make the additional cost and effort economically viable. Wells are abandoned once production drops when even secondary recovery equipment is no longer economically practical. Even so, oil remains within the oil field and would be removed if suitable equipment and methods were available.  
       BRIEF SUMMARY OF THE INVENTION  
       [0004]     The present invention provides a method and system capable of economically removing a liquid from a liquid reservoir, such as oil from an oil well, by withdrawing limited quantities of the liquid in discrete steps.  
         [0005]     The system includes a dipping unit sized to be received in a passage to a liquid reservoir, such as the casing of an oil well, and a unit for lowering and raising the dipping unit within the passage. The dipping unit is configured and oriented to have an upper end portion and a lower end portion when within the passage. The dipping unit includes a chamber, a feature for enabling a liquid to enter the chamber when at least its lower end portion is submerged in the liquid within the reservoir, and a feature for releasing the liquid from the chamber.  
         [0006]     The method includes lowering a dipping unit within a passage to a liquid reservoir, such as a casing of an oil well, to enable a liquid to flow into a chamber of the dipping unit when at least a lower end portion of the dipping unit is submerged in the liquid within the reservoir, and then raising the dipping unit within the passage so that the liquid is released from the chamber.  
         [0007]     In view of the above, the invention can be understood to be very simple and economical for removing liquids from a liquid reservoir, a particularly notable example of which is the removal of oil from an oil well. In the preferred invention, the invention is capable of removing oil from a well more economically than existing secondary recovery systems to the extent that an oil well can remain productive that might otherwise be abandoned as being no longer economically practical if only conventional recovery equipment were available.  
         [0008]     Other objects and advantages of this invention will be better appreciated from the following detailed description. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  represents a cross-sectional view of a dipping unit in accordance with a preferred embodiment of this invention, during which a chamber within the dipping unit is being filled with a liquid, such as oil from an oil well.  
         [0010]      FIG. 2  represents a cross-sectional view of the dipping unit of  FIG. 1  during a dump cycle.  
         [0011]      FIG. 3  is a top view of the dipping unit of  FIGS. 1 and 2 .  
         [0012]      FIG. 4  schematically represents an oil recovery system that includes the dipping unit of  FIGS. 1 through 3  in accordance with this invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]      FIGS. 1 through 3  depict a dipping unit  10  for use in removing a liquid from a liquid reservoir. A particularly notable application for the unit  10  is an oil recovery system  100  shown in  FIG. 4 . Though the invention will be described below in reference to an oil well recover system and method, the invention is not so limited. For example, the dipping unit  10  is also well suited for removing water from a water well or other water source or reservoir, such as for the purpose of obtaining water samples for testing, etc.  
         [0014]     From  FIGS. 1 and 2 , it can be seen that the dipping unit  10  generally has upper and lower end portions  12  and  14  held together with a biasing assembly  16 . A fill chamber  18  is defined in the upper end portion  12  of the unit  10  by a tube  20 , a dump adapter  22 , and a fitting  24  that secures the dump adapter  22  to the tube  20 . While the fitting  24  is represented as being attached (e.g., welded) to the tube  20  and threaded into the adapter  22 , other assembly methods are also within the scope of the invention, including fasteners, an all-welded construction, etc. In addition, it is foreseeable that a unitary construction could be adopted for the upper end portion  12 .  
         [0015]     The lower end portion  14  of the unit  10  is represented as including a valve body  28  threaded onto a valve head  30 , a plate  32  held against a shoulder of the valve body  28  by the valve head  30 , and a ball  34  within a chamber  36  of the valve body  28 . The ball  34  is free to move within the valve body chamber  36  between a valve seat  40  at the lower end of the chamber  36  and the plate  32  defining the upper end of the chamber  36 . The material, size, and density of the ball  34  are preferably selected so that the ball  34  is buoyed or otherwise forced off the seat  40  by the flow of oil (or other liquid intended to be extracted by the dipping unit  10 ) under the pressure exerted by oil within an oil reservoir (field, accumulation, pool, etc.), such as the reservoir  64  represented in  FIG. 4 . One or more passages  42  are present in the plate  32  to fluidically connect the valve body chamber  36  to an annular-shaped chamber  44  within the valve head  30 , which as discussed below is fluidically connected to the fill chamber  18  within the upper end portion  12  of the unit  10 . The annular shape of the chamber  44  is the result of a cylindrical boss  38  attached to or otherwise part of the valve head  30  and/or plate  32 . While a ball valve assembly (ball  34  and valve body  28 ) is shown, from the following discussion it will become evident that other valve assemblies (both mechanically and electrically operated) capable of permitting oil flow into the lower end portion  14  of the dipping unit  10  are also within the scope of the invention.  
         [0016]     The biasing assembly  16  is represented as including a bolt  46  that passes through a boss  26  within and secured to the dump adapted  22 , passes through a gasket  48  between the upper and lower end portions  12  and  14  of the unit  10 , and is threaded into the boss  38  of the valve head  30 . A compression spring  50  is compressed between the head  52  of the bolt  46  and the boss  26  of the dump adapter  22 , biasing the valve head  30  (and therefore the entire lower end portion  14 ) toward the upper end portion  12  and compressing the gasket  48  therebetween. One or more passages  54  are defined in the gasket  48  so that the valve body chamber  36  is fluidically connected to the fill chamber  18  within the upper end portion  12  of the unit  10  through the passages  42  in the plate  32 , the chamber  44  within the valve head  30 , and the passages  54  in the gasket  48 . The compression spring  50  provides an in expensive and uncomplicated biasing action well suited for use in the dipping unit  10  of this invention, though it should be understood that other biasing mechanisms are also within the scope of the invention, including other types of springs, elastic materials, pneumatically, mechanically, and electrically operated cylinders, etc.  
         [0017]     The dipping unit  10  is further represented as including a plate-like flange  56  with an opening  58  through which the upper end portion  12  of the unit  10  is received. As evident from  FIG. 4 , the flange  56  is intended to be mounted at or near the upper end of a substantially (though not necessarily) vertical well casing  62  in which the dipping unit  10  operates, and therefore would normally be located a considerable distance from the lower end portion  14  of the dipping unit  10  during a fill cycle. However, for convenience  FIG. 1  depicts the flange  56  as immediately above the lower end portion  14  during a fill cycle.  
         [0018]     As evident from  FIG. 4 , the width of the dipping unit  10  is sufficiently less than that of the casing  62  to allow the unit  10  to move freely between the flange  56  and the reservoir  64 . From  FIG. 2 , it can be seen that the lower end portion  14  and gasket  48  of the unit  10  have slightly larger diameters than the upper end portion  12  of the unit  10  and the opening  58  in the flange  56 , so that the unit  10  is able to freely travel upward through the opening  58  until the gasket  48  and lower end portion  14  encounter the flange  56 , at which point the lower end portion  14  can travel no farther and the gasket  48  seals against the lower surface of the flange  56  surrounding the opening  58 . Because of the biasing assembly  16 , the upper end portion  12  of the unit  10  is able to continue traveling upward a limited distance (e.g., until the spring  50  is completely compressed). As evident from  FIG. 2 , the ability of the upper end portion  12  to continue traveling upward relative to the lower end portion  14  results in separation  60  of the end portions  12  and  14  at the lower extremity of the chamber  18 .  
         [0019]     With the dipping unit  10  as described above, the unit  10  is effectively configured to bail oil from an oil well by filling the fill chamber  18  through the valve body  28  when the lower end portion  14  is sufficiently submerged in oil to cause the ball  34  to unseat from its valve seat  40 , as represented in  FIGS. 1 and 4 . Oil that enters the valve body chamber  36  rises up through the passages  42  within the plate  32  and through the chamber  44  within the lower end portion  14  of the unit  10 , and then enters the fill chamber  18  through the passages  54  within the gasket  48 . As depicted in  FIG. 4 , depending on the length of the tube  20  it may also be possible that oil enters the fill chamber  18  from the upper extremity of the upper end portion  12 , which is preferably open as indicated in  FIG. 3 . Once oil flow into the dipping unit  10  ceases as a result of hydraulic pressure equalization, the ball  34  reseats itself against its valve seat  40  and the dipping unit  10  is raised through the well casing  62  until the lower end portion  14  encounters the flange  56  at the top of the casing  62 , causing the oil within the fill chamber  18  to be dumped through the separation  60  created between the end portions  12  and  14  of the dipping unit  10 . The ball valve assembly  28 / 34  prevents or otherwise minimizes the loss of oil from the fill chamber  18  as the unit  10  is raised within the casing  62 , and the gasket  48  and ball valve assembly  28 / 34  cooperate to prevent the oil released from the fill chamber  18  from flowing back into the well casing  62 .  
         [0020]      FIG. 4  schematically represents the oil released from the fill chamber  18  as being dumped into an enclosure  66  that includes a drain pipe  68  through which the oil flows before being collected in a holding tank  70 . The tank  70  is represented as equipped with a sensor  84  to detect the presence of water in the oil, for example, a float that is buoyant in oil but not water, so that appropriate actions can be taken to avoid or minimize water contamination, including stoppage of the dipping unit  10  and initiating an inactive period in the recovery process during which oil from the surrounding substrata is allowed to refill the well before resuming oil extraction. Various alternatives are known to be capable of performing the same or equivalent function, such as a sensor in the enclosure  66 , drain pipe  68 , or tank  70  that detects the presence of water by, for example, sensing electrical conductivity. The water sensor  84  can also be used to initiate water separation from the holding tank  70 , such as with an oil/water separator, or actions to remove water from the well. The enclosure  66  further contains a winch  72 , a cable  74  (for example one-eight inch (about 3 mm) stainless steel), and a pulley  76  configured to lower and raise the dipping unit  10 , an electrical power supply  78  for powering a motor (e.g., a 1 HP electronically-controlled DC servomotor) for the winch  72 , and a control panel  80  for housing a control system for operating the winch  72 . The control system is preferably equipped to allow for manual, programmed, and automatic operation of the dipping unit  10 . For this purpose, the pulley  76  is preferably equipped with an encoder  82  that operates with the cable  74  to monitor the travel of the dipping unit  10 . The encoder  82  is also preferably able to detect when vertical movement of the dipping unit  10  ceases, as when the unit  10  encounters a body of oil in the reservoir  64  at the lower end of the casing  62  and when the lower end portion  14  of the unit  10  encounters the flange  56  at the upper end of the well casing  62 . The encoder  82  or any suitable switch can be used during operation of the control system in a calibration mode, during which a zero depth for the dipping unit  10  can be associated with the upper limit of travel for the dipping unit  10 .  
         [0021]     If the control system is a microprocessor-based intelligent control system, feedback from the encoder  82  can be used to train the control system to slow the assent and descent of the dipping unit  10  to allow more gradual stops. Alternatively or in addition to the encoder  82 , the current draw of the winch  72  can be monitored or the winch  72 , cable  74 , or pulley  76  can be equipped with a strain gage to sense when the dipping unit  10  encounters a body of oil at the lower end of the casing  62  and encounters the flange  56  at the lower (fill) and upper (dump) extents, respectively, of the dipping unit  10 , as well as to detect any obstruction or other anomaly in the operation of the dipping unit  10 . An intelligent control system is also capable of learning the optimum stopping point for effectively recovering oil on an ongoing basis. For example, through feedback from the encoder  82 , strain gage, and/or water sensor  84 , the control system can learn how deep to lower the dipping unit  10 , how many cycles to complete before encountering water, and how long an inactive period is necessary to allow oil from the surrounding substrata to replenish the oil well to a suitable level to permit reinitiating oil extraction.  
         [0022]     In its manual operating mode, the control system preferably enables an operator to press buttons to lower and raise the dipping unit  10  all while monitoring a display that continuously shows the depth of the unit  10 . Safety limits established by the encoder  82 , water sensor  84 , strain gage, etc., preferably set outer limits of operation to ensure safety. For the programmed mode, the control system can be preferably programmed for maximum fill depth, dwell time at the fill depth, dwell time at the upper (dump) extent of operation, and number of fill-dump cycles to make in succession before initiating an inactive period during which oil is allowed to replenish the oil well. When operating in the automatic mode, the control system is preferably programmed for maximum fill depth, dwell time at the fill depth, and dwell time at the upper (dump) extent of operation, but then makes use of the feedback from the water sensor  84  to set the number of fill-dump cycles to make in succession before initiating an inactive period. Any of these operating modes can also include a water extraction cycle for the purpose of extracting water from the well with the dipping unit  10 . Control systems of the type described above are well within the scope of those skilled in the pertinent art, and therefore will not be described in any further detail.  
         [0023]     The capacity of the dipping unit  10  and system  100  can be readily varied according to the particular application. For use as a secondary recovery system in oil fields, the size of the fill chamber  18  within the dipping unit  10  and the operation of the system  100  are believed to be capable of achieving pumping capacities on the order of about five barrels of oil per day, though lesser and greater capacities are also within the scope of this invention.  
         [0024]     While the invention has been described in terms of a preferred embodiment, it is apparent that other forms could be adopted by one skilled in the art. For example, the physical configuration of the dipping unit  10 , enclosure  66 , and their individual components could differ from those shown and discussed, and various materials and processes for manufacturing the dipping unit  10 , enclosure  66 , and their individual components are known to those skilled in the art and could be used. Therefore, the scope of the invention is to be limited only by the following claims.