Downhole oil well pump apparatus
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to pumps that are used in the secondary recovery of oil, namely recovery of oil that will not flow to the surface via downhole pressure. Even more particularly, the present invention relates to an improved downhole oil well pump that includes a flexible pumping member activated with hydrostatic pressure of liquified gas (such as, for example, butane) and a closed circuit flow path for the gas that includes a compressing step to recompress the butane to liquid form after it has been expanded to gaseous state following the pumping cycle of the pump. 
     2. General Background 
     In the pumping of oil from a downhole oil well environment, it has been known to use mechanical pumps such as rod pumps to lift oil to the earth&#39;s surface when that oil will not flow because of low formation pressure. Such pumps have been in use for years and are commercially available from a number of manufacturers such as Camco, Otis, Halliburton and others. These same manufacturers supply gas lift valves that can be used to &#34;lift&#34; oil from a sluggish well. Gas lift valves are valving structures that are positioned at vertically spaced intervals along the production tubing. They are activated at varying pressures, providing pressurized gaseous injection at various levels in the well to help urge the oil upwardly. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved oil pump apparatus for lifting oil to the earth&#39;s surface. The apparatus provides an improved method and apparatus for lifting oil to the earth&#39;s surface that would not otherwise flow freely because of lack of downhole pressure. The apparatus of the present invention includes an elongated tool body and a means for lowering the tool body into the well to a level that contains oil to be pumped. In the preferred embodiment, the lowering device can be a coil tubing unit. 
     A packer is provided for closing off the production tubing below the tool body. 
     The tool body includes a bladder that flexes between expanded and contracted positions. 
     The tool body includes a production channel for transmitting oil between the bladder and the earth&#39;s surface. Valves are provided above and below the bladder at the production channel to valve fluid flow. One valve allows oil into the bladder, a check valve allows oil to flow upwardly but closes to keep oil from reversing its flow. 
     A closed circuit, pressurized gas system is used to generate a flow differential for forcing the oil to be pumped upwardly. 
     In the preferred embodiment, the closed circuit pressurized gas system includes a delivery pipe that transmits liquified butane or liquified propane or the like downhole to the bladder. The liquified butane uses its own hydrostatic pressure to collapse the bladder forcing the oil upwardly through the production channel. A timer regulates transmission of the liquified butane downhole. 
     The apparatus of the present invention is unique in that it uses a hydrostatic head of liquified gas to help lift the oil in the well. 
     During placement, the apparatus of the present invention can be installed on coiled tubing without removing existing tubing. 
     The lifting fluid (for example propane or butane) is maintained in the coil tubing under enough pressure to keep it in liquid state. 
     The coil tubing annulus contains the liquid gas to be pumped. The production tubing or casing annulus contains low pressure gas returning to the surface. A compressor is used at the surface to recompress the gas to a liquid state so that is can provide enough hydrostatic pressure to lift the produced liquid. 
     Extremely high pressures are not required because the produced oil is not much heavier than liquid propane or butane unless there is a large amount of produced water. 
     Typical oil wells already have a tubing/annulus packer installed. If so, the packer is set with a standing valve in the tubing near the bottom. With the method of the present invention, a hole is punched in the tubing a known distance above the standing valve packer. 
     The user then runs another packer with the pump and sleeve valve spaced such that the punched hole is between the sleeve valve and the pump packer. 
     Water is displaced in the well with liquified gas such as propane, and the packer is set. The user then bleeds the tubing/casing annulus off until the well fluid expands the pump bladder. By increasing with coil pressure, the sleeve valve opens and directs the coil pressure to the outside of the bladder while sealing the punched hole. The bladder will then collapse forcing the well fluid (oil) up the coil/tubing annulus. 
     A timer is provided at the surface that will stop the pressure when the bladder is collapsed. A spring loaded pressure actuated ball valve on the bottom will support the hydrostatic pressure of the liquified propane. 
     The sleeve valve will close, venting the outside of the bladder to the tubing/casing annulus through the punched hole. Well fluid will then be exposed to low pressure and will fill the bladder. When this is completed, a surface timer will repressure the coil tubing and the cycle is repeated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a further understanding of the nature and objects of the present invention, reference should be had to the following detailed description, taken in conjunction with the accompanying drawings, in which like parts are given like reference numerals, and wherein: 
     FIG. 1A-1C are sectional elevational views of the preferred embodiment of the apparatus of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates the preferred embodiment of the apparatus of the present invention designated generally by the numeral 10. Oil well pump apparatus 10 is shown is FIG. 1 as disposed within the lower end of a typical downhole oil well casing 11. The cylindrically shaped casing 11 extends down into the surrounding formation 12 having oil to be pumped to the surface. 
     A production tubing 13 also extends down into the well, being concentrically positioned within the casing 11. A casing packer 14 is disposed at the lower end of the casing between the casing 11 and production tubing 13. The lower end of the casing 11 carries a plurality of perforations 16 that allow oil to flow into the lower end 15 of casing 11 via perforations 16. Arrows 17 in FIG. 1 schematically depict the flow path of oil from surrounding formation 12 through perforations 16 and into production tubing 13. 
     The lower end portion 18 of the production tubing 13 extends below the packer 14. Production tubing 13 has an internal bore 19. Tool body 20 is disposed within the production tubing bore 19 and extends slightly below the lower end 18 of production tubing 13. 
     Tool body 20 includes a lower cylindrical section 21. Section 21 provides a bore 22 that communicates with incoming oil, schematically shown as arrows 17. The oil entering casing 15 is prevented from flowing upwardly in casing 15 by packer 14. Oil is prevented from flowing upwardly in production tubing 18 bore 19 by packer 26. Thus, the incoming oil flows into bore 22 of lower tool body section 21. The oil flows upwardly, displacing ball 25 on valve seat 24 of check valve 23 and entering bore 30 of restricted diameter section 27 of tool body 20. In this position, the oil exits bore 30 of restricted diameter section 27 via a plurality of perforations 28 and filling flexible bladder 29. The flexible bladder 29 expands to the position shown in phantom lines in FIG. 1. The expanded position of bladder 29 (when filled with oil) is indicated by the numeral 29b in FIG. 1. The contracted position (prior to filling) is designated as 29a. 
     To pump oil from within bladder 29 (full position 29b), hydrostatic pressure in the form of liquified gas (e.g. butane or propane) is pumped downhole via bore 52 of gas delivery line 51 (see arrows 53, FIG. 1). Gas delivery line 51 can be coil tubing of a coil tubing unit (commercially available). The coil tubing can also be used to place the tool body 20 in the well. The liquified gas produces a hydrostatic head that transmits pressure via line 45 to sleeve valve 34, opening flexible sleeve 35 and depressing the external surface of bladder 29. This hydrostatic head collapses bladder 29 and forces oil within bladder 29 to flow upwardly (see arrows 41, 43, 63) to oil exit port 64. 
     A timer (located at the well surface area) is preferably used to stop the pressure acting on bladder 29 once the bladder 29 has collapsed. At that time, spring loaded pressure actuated ball valve 47 will support the hydrostatic pressure of the liquified gas (i.e. butane or propane). Sleeve valve 34 will close when pumping stops, venting gas on the outside of bladder 29 to the casing annulus via opening 39. Well fluid (i.e. oil to be pumped) will be exposed to this low pressure and will then fill the bladder 29 again. When this is done, the surface timer will repressure the delivery line 51 and the cycle repeats. 
     Check valve body 31 includes a valve seat 32 for receiving ball 33. During a pumping of oil and a collapsing of bladder 29, ball 33 closes check valve body 31 by seating against valve seat 32. 
     Sleeve valve body 34 defines a central section of tool body 20, positioned above restricted diameter section 27 of tool body 20. Sleeve valve body 34 carries a cylindrically shaped flexible sleeve 35 that includes an attached portion 36 and a moving portion 37. When liquid butane is pumped (see arrow 53) downhole via delivery tube 51, it opens the moving portion 37 of flexible sleeve 35 so that the hydrostatic head of liquid butane (or like liquid gas) flows through flow openings 50 and engages the outside surface of bladder 29, causing bladder 29 to collapse to the position shown in hardlines and designated as 29a. 
     Delivery tube 51 communicates with cylindrical section 38 of tool body 20. As part of the method of the present invention, a flow opening 39 is formed in the well production tubing 13 adjacent sleeve valve body 34. An upper tubing packer 40 is placed between cylindrical tool body section 38 and sleeve valve body 34 as shown in the drawing. When the pump 56 stops pumping liquid butane downhole via delivery tube 51, spring 48 closes ball valve 47 by forcing ball valve 47 against valve seat 46. 
     Coil spring 48 extends between ball 47 and annular shoulder 49. When this occurs, the sleeve moving portion 37 collapses against openings 50 and the butane below packer 40 exits via flow opening 39 into casing annulus above packer 14 that flow zone being indicated by the arrow 62 as a return flow path for butane gas. 
     Valve tree 54 includes flow outlet 60 for vaporized butane gas returning to compressor 58 and pump 56. Oil exit port 64 delivers the production of oil from the well. Pump 56 is schematically shown in FIG. 1 as transmitting liquified gas under pressure via flow line 55 to liquid delivery tube 51. Compressor 58 receives butane (gaseous phase) via flow outlet 60 as schematically indicated by the arrows 59. Flow line 57 transmits liquid butane from compressor 58 to pump 56 after it has been changed from gaseous phase to liquid phase. 
     With the method of the present invention, pump 56 transmits liquified gas such as butane, propane, or like via line 55 to pump delivery tube 51. The liquid butane defines a hydrostatic head that opens valve 47 and exerts pressure on bladder 29 that has been filled with oil to be pumped. The pressure exerted on bladder 29 also closes ball 25 against seat 24 preventing the reverse flow of oil from within bladder 29 to the lower end of 21 of the tool body 20. A timer can be used to run the pump 56 for a desired time interval based upon the rate at which oil is entering bladder 29, the size of bladder 29, and the size of the flow channels leading to and from bladder 29. 
     When the pump 56 is stopped by the timer, valve 47 closes and the gas below valve 47 transfers from liquid to gaseous phase as it exits port 39. Returning gaseous phase butane or propane travels through annulus 61 (see arrows 62) to compressor 58 where the gaseous phase butane or propane is recompressed to liquid phase and transferred via line 57 to pump 56. The cycle can thus be controlled by alternating the pump 56 between pumping (on) and non-pumping (off) timed cycles. 
     Because the apparatus 10 of the present invention is an elongated structure, the sectional view of the apparatus 10 has been split into three drawing sheets as FIGS. 1A, 1B, and 1C. Match lines A--A on FIGS. 1A and 1B shows that the bottom of FIG. 1A and 1B shows that the bottom of FIG. 1A matches the top of Figure 1B. Similarly, the bottom of FIG. 1B matches the top of FIG. 1C at match lines B--B. 
     The following table lists the parts numbers and parts descriptions as used herein and in the drawings attached hereto. 
     
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PARTS LIST                                                                
Part Number     Description                                               
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10              oil well pump                                             
11              casing                                                    
12              formation                                                 
13              production tubing                                         
14              casing packer                                             
15              lower end of casing                                       
16              perforations                                              
17              arrows                                                    
18              lower end of tubing                                       
19              tubing bore                                               
20              tool body                                                 
21              lower cylindrical section                                 
22              tool body bore                                            
23              check valve body                                          
24              valve seat                                                
25              ball                                                      
26              packer                                                    
27              restricted diameter section                               
28              perforations                                              
29              flexible bladder                                          
30              bore                                                      
31              check valve body                                          
32              valve seat                                                
33              ball                                                      
34              sleeve valve body                                         
35              flexible sleeve                                           
36              attached portion                                          
37              moving portion                                            
38              cylindrical section                                       
39              flow opening                                              
40              upper tubing packer                                       
41              arrows                                                    
42              lateral channel                                           
43              arrow (production)                                        
44              relief valve body                                         
45              vertical channel                                          
46              valve seat                                                
47              ball                                                      
48              coil spring                                               
49              annular shoulder                                          
50              flow opening                                              
51              liquified gas delivery tube                               
52              bore                                                      
53              arrow                                                     
54              valve tree                                                
55              flow line                                                 
56              pump                                                      
57              flow line                                                 
58              compressor                                                
59              arrow                                                     
60              flow outlet                                               
61              annulus                                                   
62              arrow                                                     
63              flow line                                                 
64              oil exit port (production)                                
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     Because many varying and different embodiments may be made within the scope of the inventive concept herein taught, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirement of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.