Abstract:
A downhole ram pump. A downhole pump system includes a flow restricting device which variably restricts fluid flow through an opening, the restricting device vibrating in response to the fluid flow, thereby alternately increasing and decreasing the fluid flow through the opening; and a pump device which generates a pressure differential in response to vibration of the restricting device. Another downhole pump system includes a flow restricting device which vibrates in response to fluid flow through an opening, thereby alternately increasing and decreasing the fluid flow through the opening, a pressure differential across the restricting device variably biasing the restricting device to increasingly restrict the fluid flow through the opening, and the pressure differential alternately increasing and decreasing in response to respective alternate increasing and decreasing flow through the opening; and a pump device which generates differential pressure in response to vibration of the restricting device.

Description:
BACKGROUND  
       [0001]     The present invention relates generally to equipment utilized and operations performed in conjunction with subterranean wells and, in an embodiment described herein, more particularly provides a downhole ram pump.  
         [0002]     A wide variety of downhole well tools may be utilized which are hydraulically operated. For example, flow control devices, packers, plugs, etc. are available, and others may be developed in the future, which use pressure in performing their respective functions.  
         [0003]     In the past, the most common methods of supplying hydraulic pressure to well tools were use of well fluid pressure, and transmission of pressure through control lines extending large distances from a remote location, such as the earth&#39;s surface or another location in the well. However, well fluids usually contain debris which can cause a malfunction in a well tool, and pressure in a well fluctuates and is difficult to predict and control. Control lines are relatively expensive and time-consuming to install, and are subject to damage during installation.  
         [0004]     Therefore, it may be seen that it would be very beneficial to be able to generate hydraulic pressure downhole, e.g., in relatively close proximity to a well tool which is operated using the pressure. This would preferably eliminate the need for using well fluid pressure to operate the well tool, and would preferably eliminate the need to extend control lines large distances in the well.  
       SUMMARY  
       [0005]     In carrying out the principles of the present invention, a downhole pump system is provided which solves at least one problem in the art. One example is described below in which flow through a tubular string is used to operate a downhole pump device, thereby generating a differential pressure for use in operating a well tool.  
         [0006]     In one aspect of the invention, a downhole pump system is provided which includes a flow restricting device which variably restricts fluid flow through an opening. The restricting device vibrates in response to the fluid flow. The restricting device thereby alternately increases and decreases the fluid flow through the opening. A pump device generates differential pressure in response to vibration of the restricting device.  
         [0007]     In another aspect of the invention, a downhole pump system includes a flow restricting device which vibrates in response to fluid flow through an opening. The restricting device thereby alternately increases and decreases the fluid flow through the opening. A pressure differential across the restricting device variably biases the restricting device to increasingly restrict the fluid flow through the opening. The pressure differential alternately increases and decreases in response to respective alternate increasing and decreasing flow through the opening. A pump device generates differential pressure in response to vibration of the restricting device.  
         [0008]     These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of representative embodiments of the invention hereinbelow and the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a schematic partially cross-sectional view of a pump system embodying principles of the present invention;  
         [0010]      FIG. 2  is an enlarged scale schematic cross-sectional view of a pump which may be used in the system of  FIG. 1 ; and  
         [0011]      FIG. 3  is a schematic cross-sectional view of an alternate configuration of the pump of  FIG. 2 .  
     
    
     DETAILED DESCRIPTION  
       [0012]     Representatively illustrated in  FIG. 1  is a downhole pump system  10  which embodies principles of the present invention. In the following description of the system  10  and other apparatus and methods described herein, directional terms, such as “above”, “below”, “upper”, “lower”, etc., are used for convenience in referring to the accompanying drawings. Additionally, it is to be understood that the various embodiments of the present invention described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of the present invention. The embodiments are described merely as examples of useful applications of the principles of the invention, which is not limited to any specific details of these embodiments.  
         [0013]     As depicted in  FIG. 1 , a tubular string  12  (such as a production, injection, drill, test or coiled tubing string) has been installed in a wellbore  14 . A pump  16  is interconnected in the tubular string  12 . The pump  16  generates differential pressure from flow of fluid (represented by arrow  18 ) through an internal flow passage  20  of the tubular string  12 .  
         [0014]     The fluid  18  is shown in  FIG. 1  as flowing upwardly through the tubular string  12  (as if the fluid is being produced), but it should be clearly understood that a particular direction of flow is not necessary in keeping with the principles of the invention. The fluid  18  could flow downwardly (as if being injected) or in any other direction. Furthermore, the fluid  18  could flow through other passages (such as an annulus  22  formed radially between the tubular string  12  and the wellbore  14 ) to operate the pump  16 , if desired.  
         [0015]     The pump  16  is illustrated in  FIG. 1  as being connected to various well tools  24 ,  26 ,  28  via fluid lines  30  external to the tubular string  12 . These lines  30  could instead, or in addition, be positioned within the passage  20  or in a sidewall of the tubular string. As another alternative, the well tools  24 ,  26 ,  28  (or any combination of them) could be integrally formed with the pump  16 , for example, so that the lines  30  may not be used at all, or the lines could be integral to the construction of the pump and well tool(s).  
         [0016]     The well tool  24  is depicted in  FIG. 1  as being a pressure set packer. For example, elevated pressure supplied via the lines  30  could be used to operate an actuator to set the packer, or the elevated pressure could be used to operate a valve to control application of well pressure to a setting mechanism, etc.  
         [0017]     The well tool  26  could be any type of well tool, such as a flow control device, sampler, telemetry device, plug, etc. The well tool  26  could also be representative of instrumentation for another well tool, such as a control module, actuator, etc. for operating another well tool. As another alternative, the well tool  26  could be one or more accumulators used to store pressure for operating other well tools.  
         [0018]     The well tool  28  is depicted in  FIG. 1  as being a flow control device, such as a sliding sleeve valve or variable choke. The well tool  28  is used to control flow between the passage  20  and the annulus  22 . Alternatively, the well tool  28  could be a flow control device which controls flow in the passage  20 , such as a safety valve.  
         [0019]     Although certain types of well tools  24 ,  26 ,  28  are described above as being operated using pressure generated by the pump  16 , it should be clearly understood that the invention is not limited to use of the pump  16  with any particular type of well tool. The invention is also not limited to any particular type of well installation or configuration.  
         [0020]     Referring additionally now to  FIG. 2  an enlarged scale schematic cross-sectional view of the pump  16  is representatively illustrated. The pump  16  is shown apart from the remainder of the system  10 , it being understood that in use the pump would preferably be interconnected in the tubular string  12  at upper and lower end connections  32 ,  34  so that the passage  20  extends through the pump.  
         [0021]     Accordingly, in the system  10  the fluid  18  flows upwardly through the passage  20  in the pump  16 . The fluid  18  could flow in another direction (such as downwardly through the passage  20 , etc.) if the pump  16  is used in another system.  
         [0022]     The passage  20  extends through a generally tubular housing  36  of the pump  16 . The housing  36  may be a single tubular member or it may be an assembly of separate components.  
         [0023]     Note that the housing  36  includes a flow restriction  38  in the form of a venturi in the passage  20 . As the fluid  18  flows through the restriction  38 , a pressure differential is created, in a manner well understood by those skilled in the art. Pressure in the passage  20  upstream of the restriction  38  will, therefore, be greater than pressure downstream of the restriction.  
         [0024]     The housing  36  also includes openings  40  formed through its sidewall downstream of the restriction  38 , and openings  42  formed through its sidewall upstream of the restriction. An annular chamber  44  formed between the housing  36  and an outer housing  46  is in communication with each of the openings  40 ,  42 . Thus, instead of flowing directly through the restriction  38 , a portion of the fluid  18  is induced by the pressure differential in the passage  20  to flow through the openings  42  upstream of the restriction  38  to the chamber  44 , and from the chamber through the openings  40  back into the passage  20  downstream of the restriction.  
         [0025]     A flow restricting device  48  is positioned in the chamber  44 . The device  48  operates to variably restrict flow through the openings  40 , for example, by varying an unobstructed flow area through the openings. The device  48  is illustrated as a sleeve, but other configurations, such as needles, cages, plugs, etc., could be used in keeping with the principles of the invention.  
         [0026]     As depicted in  FIG. 2 , the openings  40  are fully open, permitting relatively unobstructed flow through the openings. If, however, the device  48  is displaced upwardly, the flow area through the openings  40  will be increasingly obstructed, thereby increasingly restricting flow through the openings.  
         [0027]     The device  48  has an outwardly extending annular projection  50  formed thereon which restricts flow through the chamber  44 . Because of this restriction, another pressure differential is created in the chamber  44  between upstream and downstream sides of the projection  50 . As the fluid  18  flows through the chamber  44 , the pressure differential across the projection  50  biases the device  48  in an upward direction, that is, in a direction which operates to increasingly restrict flow through the openings  40 .  
         [0028]     Upward displacement of the device  48  is resisted by a biasing device  52 , such as a coil spring, gas charge, etc. The biasing device  52  applies a downwardly directed biasing force to the device  48 , that is, in a direction which operates to decreasingly restrict flow through the openings  40 .  
         [0029]     If the force applied to the device  48  due to the pressure differential across the projection  50  exceeds the biasing force applied by the biasing device  52 , the device  48  will displace upward and increasingly restrict flow through the openings  40 . If the biasing force applied by the biasing device  52  to the device  48  exceeds the force due to the pressure differential across the projection  50 , the device  48  will displace downward and decreasingly restrict flow through the openings  40 .  
         [0030]     Note that if flow through the openings  40  is increasingly restricted, then the pressure differential across the projection  50  will decrease and less upward force will be applied to the device  48 . If flow through the openings is less restricted, then the pressure differential across the projection  50  will increase and more upward force will be applied to the device  48 .  
         [0031]     Thus, as the device  48  displaces upward, flow through the openings  40  is further restricted, but less upward force is applied to the device. As the device  48  displaces downward, flow through the openings  40  is less restricted, but more upward force is applied to the device. Preferably, this alternating of increasing and decreasing forces applied to the device  48  causes a vibratory up and down displacement of the device relative to the housing  36 .  
         [0032]     A pump device  54  uses this vibratory displacement of the device  48  to generate differential pressure. An annular piston  56  is connected to the device  48  so that it displaces with the device  48 . The piston  56  could be integrally formed with the device  48 , or it could be separately formed and then connected to the device.  
         [0033]     Displacement of the piston  56  causes an annular pump chamber  58  to change volume. As the piston  56  displaces upward, the pump chamber  58  volume decreases. As the piston  56  displaces downward, the pump chamber  58  volume increases.  
         [0034]     Input and output lines  60 ,  62  are connected to the pump chamber  58 . A check valve  64  interconnected in the input line  60  only permits flow through the line into the pump chamber  58 . Another check valve  66  interconnected in the output line  62  only permits flow through the line out of the pump chamber  58 .  
         [0035]     Thus, as the piston  56  displaces upward, the volume of the chamber  58  decreases and fluid in the chamber is forced to flow out of the chamber through the output line  62 . As the piston  56  displaces downward, the volume of the chamber  58  increases and fluid is drawn into the chamber through the input line  60 . Preferably, the piston  56  continuously displaces alternately upward and downward with the device  48  while the fluid  18  flows through the passage  20 , so that fluid is pumped through the chamber  58  (i.e., into the chamber via the line  60  and out of the chamber via line  62 ) while the fluid  18  flows through the passage  20 .  
         [0036]     The pump device  54  is connected to an accumulator device  68 . Specifically, the line  62  is connected to an annular chamber  70 , and the line  60  is connected to another annular chamber  72 . The pump device  54  and accumulator device  68  could be combined into a single assembly, or they could be separately constructed and then either connected directly to each other or remotely connected to each other.  
         [0037]     Another annular chamber  74  is separated from the chamber  70  by a floating annular piston  76 . The chamber  74  is also separated from the chamber  72  by another floating annular piston  78 . Preferably, a compressible fluid (such as nitrogen gas, etc.) is contained in the chamber  74 .  
         [0038]     The accumulator device  68  also includes a biasing device  80  (such as a coil spring, etc.). The biasing device  80  applies a biasing force to the piston  78 , which operates to maintain a pressure differential across the piston. As will be appreciated by those skilled in the art, the force applied to one side of the piston  78  by pressure in the chamber  72  and by the biasing device  80  will equal the force applied to the other side of the piston by pressure in the chamber  74 .  
         [0039]     Thus, at a state of equilibrium, the pressure in the chamber  72  will preferably be less than the pressure in the chamber  74 . In addition, at the state of equilibrium, pressure in the chamber  70  will equal pressure in the chamber  74 . However, it should be clearly understood that other pressures and pressure relationships may be used in keeping with the principles of the invention.  
         [0040]     The pump device  54  and accumulator device  68  utilize a principle known to those skilled in the art as a “ram pump.” The momentum of the moving components (the device  48 , piston  56  and fluid moving through the line  62 ) operate to increase the pressure of the fluid in the chamber  70  of the accumulator device  68  when the piston  56  is displacing upward. Similarly, the momentum of the moving components operate to decrease the pressure of the fluid in the chamber  72  of the accumulator device  68  when the piston  56  is displacing downward. Thus, an increased pressure differential between the chambers  70 ,  72  is achieved using this principle. The chamber  74  provides an effective compressible “cushion” for the introduction of fluid into the chamber  70  and the withdrawal of fluid from the chamber  72  during operation of the pump device  54 .  
         [0041]     As described above, pressure in the chamber  70  will be elevated relative to pressure in the chamber  72  during operation of the pump device  54 . This pressure differential may be used to operate an actuator  82  for a well tool. The actuator  82  is depicted in  FIG. 2  as including a cylindrical piston  84  separating chambers  86 ,  88  but it should be clearly understood that any type of actuator may be used in keeping with the principles of the invention.  
         [0042]     The actuator  82  is merely an example of a manner in which elevated pressure generated by the pump  16  may be used to operate a well tool. For example, the actuator  82  could be used to set the well tool  24 , or displace a closure device of the well tool  28 , or otherwise operate the well tool  26 , etc. In addition, elevated pressure, reduced pressure, or differential pressure generated by the pump  16  may be used in any manner, and in systems other than the system  10 , in keeping with the principles of the invention.  
         [0043]     A control module  90  may be interconnected between the chambers  86 ,  88  of the actuator  82  and the chambers  70 ,  72  of the accumulator device  68 . The control module  90  may be used to control how and when the various chambers  70 ,  72 ,  86 ,  88  are placed in communication with each other. The control module  90  may be operated remotely via telemetry (such as electrical, pressure pulse, acoustic, electromagnetic, optical or other form of telemetry) and/or the control module may be operated in response to local stimulus, such as outputs of sensors, etc.  
         [0044]     Referring additionally now to  FIG. 3 , another configuration of the pump  16  is representatively illustrated. In this configuration, the accumulator device  68  is not used. Instead, the control module  90  operates to connect the chamber  58  via the line  62  to the desired one of the chambers  86 ,  88  when the piston  56  displaces upward, and to connect the other of the chambers  86 ,  88  to the chamber  58  via the line  60  when the piston displaces downward. The control module  90  may include an accumulator therein for storing pressure and fluid. In this regard, note that the control module  90  may be combined with the accumulator device  68  described above and/or may be combined with the pump device  54 , if desired.  
         [0045]     Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the invention, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to the specific embodiments, and such changes are contemplated by the principles of the present invention. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims and their equivalents.