Abstract:
The present invention relates to a pumping system and method for drawing or pumping subsurface fluid (e.g., gas, oil, water, etc.) from a well, particularly a gas well. The pumping system of the present invention includes a pump which displaces fluid in a well into a string of hollow sucker rods during the downward stoke of the pump. The string of hollow sucker rods extends generally to the surface so that the fluids can be directed to collection equipment on the surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not applicable.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable.  
       BACKGROUND OF THE INVENTION  
       [0003]     The present invention relates generally to pumping systems for recovering or pumping subsurface liquids from a well.  
         [0004]     When hydrocarbon-producing wells are drilled, initial hydrocarbon production is usually attained by natural drive mechanisms which force the hydrocarbons into producing wells. Further, as the reservoir energy is spent during production, it may be necessary to use other methods to recover the large quantities of hydrocarbons remaining in the reservoir. For example, a common technique is water flooding, wherein water is injected through certain injection wells to displace the remaining hydrocarbons from the reservoir into a producing well in the field.  
         [0005]     During production, the natural and/or artificial production fluids travel up a casing (i.e., tubing) of the well. Commonly, the casing of the well includes lower sections of tubing having a smaller diameter, such as a diameter of 2⅞ inches, and upper sections having other diameters, such as a diameter of 5½ inches. Due to the larger dimensions of the upper casing sections however, the fluid of the well may rise to a level such that the pressure behind the fluid is no longer sufficient to drive the fluids of the well to the surface. This causes the well to effectively “suffocate.” Moreover, “bubbling” can occur, which results in significant gas loss (e.g., 3 to 10 MCF/day).  
         [0006]     Commonly, gas wells are slim hole completions utilizing smaller diameter casing sections at the lower ends of the well. For example, consider a casing having a 500-1,000 foot section of 2⅞ inch tubing at the lower end of the well, which then transitions into a 8,000-9,000 foot section of 5½ inch tubing extending to the surface. The 2⅞ inch tubing at the bottom of the casing may not enable the fluid to be forced up the length of the casing because the fluid essentially gets “too heavy”, especially when the fluid reaches the 5½ inch portion of the tubing, or when the fluid includes a heavy substance, such as water. If the well becomes “waterlogged” and the fluid cannot be lifted to the surface, the well suffocates and bubbles.  
         [0007]     Generally, a conventional pump with a string of solid rods cannot be utilized because of the inability of the convention pump to efficiently lift the heavy fluid. Further, caution must be used so as not to rupture the casing wall of the well. Therefore, a need exists for a safe, effective and efficient pumping system for drawing fluid from a producing well. It is to such a pumping system that the present invention is directed.  
       SUMMARY OF THE INVENTION  
       [0008]     The pumping system of the present invention includes a down hole downstroke pump. Fluid flows into the barrel of the pump and is displaced therefrom via a hollow plunger into a string of hollow sucker rods on the downward stoke of the pump. The string of hollow sucker rods extend generally to the surface so that the fluid can be directed to collection equipment on the surface. Substantially all of the fluid is conveyed to the surface through the string of hollow sucker rods rather than through the cavity of the well tubing thereby relieving wear and tear on the sucker rods. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a schematic diagram of a pumping system constructed in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0010]     Referring now to  FIG. 1 , shown therein is a pumping system  10  for pumping fluids from a gas well  12 , the gas well  12  defined by a well tubing  14  (which may also be referred to herein as a well casing  14 ). The gas well  12  extends from a ground surface  15  a distance into the earth to a hydrocarbon bearing formation (not designated). The well tubing  14  has a well tubing hole  16  within which gases and fluids from the hydrocarbon bearing formation collect via perforations (not shown) in the well tubing  14 .  
         [0011]     The pumping system  10  is constructed of a pump  18  which has a pump barrel  20 . A lower end  22  of the pump  18  is connected to a seating nipple  24  which in turn is attached to a holddown device  26  which is attached to an inner surface  27  of the well tubing  14 . The holddown device  26  thereby secures the pump  18  at a position within the well tubing  14 . The seating nipple  24  has perforations  28  which allow fluids and gas to flow into the pump  18  from the well  12 .  
         [0012]     The pump  18  is constructed of a hollow plunger  30  which has an upper end  32  and a lower end  34 . The hollow plunger  30  has a plunger cavity  36  into which fluids and gas can flow from the pump barrel  20 . Attached to the hollow plunger  30  is a string of hollow sucker rods  38  which has a lower end  40 , an upper end  42 , and a sucker rod cavity  43  into which a fluid or gas can flow from the hollow plunger  30 . The lower end  40  of the string of hollow sucker rods  38  is attached to the upper end  32  of the hollow plunger  30  via a hollow adaptor/connector  44 . The hollow adaptor/connector  44  is constructed such that there is a substantially continuous opening between the hollow plunger  30  and the string of hollow sucker rods  38 . Further, the pump  18 , in one embodiment, is constructed of a standing valve  46  having an entrance hole  48  and an exit hole  50 , and a traveling valve  52  having an entrance hole  54  and an exit hole  56 . The traveling valve  52  is connected to the lower end  34  of the hollow plunger  30 . In operation, fluid and gas is pumped in an upward direction  60  through the string of hollow sucker rods  38  and thereby through a well head  66  and stuffing box  68  at an upper end of the well tubing  14  above the surface  15 .  
         [0013]     The fluid and gas flows therefrom into a flow T  70  which has a first valve  72  which leads into a separator  74 , and optionally a second valve  76  for inputting other materials into the flow T  70 , if desired. The upper end  42  of the string of hollow sucker rods  38  is attached to a polished rod  78  via a polished rod connector  80 . The polished rod  78  is connected to a pumping unit  82  which provides the mechanics for raising and lowering the string of hollow sucker rods  38  and the hollow plunger  30  of the pump  18  in a manner well known to those of ordinary skill in the art.  
         [0014]     Preferably, the pump  18  is a type of pump known in the art as a downstroke pump. In operation, the pumping system  10  is installed in the well  12  such that the pump  18  is positioned at a position in the well tubing  14  where there is significant fluid collection, as discussed previously. As noted above, the pump  18  is preferably a downstroke pump, such as is commercially available from Skillman Pump Co., Tomcat Supply (the “Pup Pump,” Oklahoma City, Okla.), Norris O&#39;Bannon Co., or Harbison-Fischer Manufacturing Co., for example.  
         [0015]     The components of the well  12  and pumping system  10  are commercially available and/or are able to be manufactured or obtained by persons of ordinary skill in the art. For example, the pump  18  is preferably a downstroke pump such as a 2 inch by 1 1/16 inch “Pup Pump” available from Tomcat Supply Co. in Oklahoma City. Other downstroke pumps are available as noted above.  
         [0016]     In operation, the pump  18  shown in  FIG. 1  pumps fluid and gas upwardly when the hollow plunger  30  of the pump  18  is on the downward stroke. More particularly, when the hollow plunger  30  is moving upwardly (pulled upwardly by the string of hollow sucker rods  38 ), the traveling valve  52  is closed. The standing valve  46  is open and fluid fills the pump barrel  20  as the hollow plunger  30  is lifted. When the downstroke is initiated, the hollow plunger  30  is pushed downwardly by the force of the string of hollow sucker rods  38  causing the standing valve  46  to close and the traveling valve  52  to open thereby causing the plunger cavity  36  of the hollow plunger  30  to be filled with the fluid in the pump barrel  20 . As fluid is forced into the plunger cavity  36 , fluid already in the plunger cavity  36  is forced upwardly in direction  60  into the string of hollow sucker rods  38 . Eventually, as the string of hollow sucker rods  38  fill with fluid over the entire length of the string of hollow sucker rods  38 , fluid is pushed through the flow T  70  into the separator  74  where the gas and oil can be separated from the remainder of the fluid pumped from the well  12 . Using the pumping system  10  described herein, substantially all of the fluid and gas is pumped through the string of hollow sucker rods  38 , contrary to other pumping systems previously available wherein fluid is pumped via the well tubing hole  16  (e.g., see U.S. Pat. Nos. 6,497,561 and 6,368,084 issued to Skillman).  
         [0017]     In one embodiment, the hollow sucker rod utilized for the string of hollow sucker rods  38  can be a “PCPRod® 1000” hollow sucker rod obtainable from Tenaris Connections in Houston, Tex., and the adaptor/connector  44  can be a common 1 inch hollow rod connector having a 11½ V thread which is modified to be compatible with the threading of the Tenaris PCPRod®. Examples of other threaded pipe joints which constructed to make the adaptor/connector  44  in accordance with the present invention can be found in U.S. Patent Application Publication Nos. 2004/0017079, 2004/0017080, and 2004/0113423; and U.S. Pat. No. 6,764,108, the entire contents of each which are hereby expressly incorporated herein by reference.  
         [0018]     The stuffing box  68  is a device that prevents leakage around the string of hollow sucker rods  38  as the string of hollow sucker rods  38  runs into and out of the well  12 . For example, the stuffing box  68  can be a packing or stuffing box made by J. M. Huber Corporation in Edison, N.J. or other stuffing boxes known in the art.  
         [0019]     Because the string of hollow sucker rods  38  generally has a smaller outer diameter than the inner diameter of the well tubing  14  (e.g., about 1.9 inches and 2⅞ inches, respectively), some bubbling can occur therebetween. The stuffing box  68  may have an integrated stuffing flow T (not shown) which can be adapted to allow for collection of the gas bubbling in the annular side between the string of hollow sucker rods  38  and the well tubing  14 .  
         [0020]     As noted above, the holddown device  26  is a device which holds the pump  18  in a substantially stationary position within the well tubing  14 . Preferably, the holddown device  26  is connected to a stationary component of the pump  18  (e.g., the pump barrel  20 ) and/or the seating nipple  24 . In one embodiment, the holddown device  26  includes a mechanical holddown having a packer, such as a commercially available 2 1/16 inch mechanical holddown.  
         [0021]     Other components of the pumping system  10  may include, but are not limited to, the following: a seating nipple  24  with dimensions 2 1/16 inch by 2⅜ inch; an adaptor/connector  44  having internal and external dimensions suitable for connecting the pump plunger  34  to an adjacently disposed hollow sucker rod of the string of hollow sucker rods  38  constructed from PCP1000 hollow rods available from Tenaris. The flow T  70  and stuffing box  68  are available from Tenaris. The stuffing box  68  may be for example 2⅞ inches by 1.9 inches with a 1 inch bleeder. Well heads  66  are well known in the art and are commercially available as are separators  74 . The well tubing  14  typically has an internal diameter of 2⅞ inches and is well known to those of ordinary skill in the art.  
         [0022]     From the above description, it is clear that the present invention is well adapted to carry out the objects and to attain the advantages mentioned herein, as well as those inherent in the invention. Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be apparent to those skilled in the art that certain changes and modifications may be practiced without departing from the spirit and scope thereof, as described herein, and that the examples described herein are not intended to limit the appended claims but only to exemplify several of the embodiments that the invention encompasses.