Patent Application
20060169458
Not applicable.
Not applicable.
The present invention relates generally to pumping systems for recovering or pumping subsurface liquids from a well.
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.
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).
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.
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.
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.
Referring now to
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.
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.
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.
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'Bannon Co., or Harbison-Fischer Manufacturing Co., for example.
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.
In operation, the pump 18 shown in
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.
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.
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.
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.
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.
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.
