Patent Publication Number: US-10774628-B2

Title: Hydraulically actuated downhole pump with traveling valve

Description:
CLAIM OF PRIORITY UNDER 35 U.S.C. 119 
     This application claims benefit of U.S. Provisional Patent Application No. 62/062,517, filed Oct. 10, 2014, and entitled “Hydraulically Actuated Downhole Pump with Travelling Valve” which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     Field 
     Embodiments of the present disclosure generally relate to hydraulically activated pump. 
     Description of the Related Art 
     When reservoir pressure in a well is insufficient for the production fluid to reach the surface on its own, pumps can be used in the well to help bring production fluids to the surface. One type of pump for such operations is a hydraulically actuated pump. 
     A hydraulically actuated pump is typically deployed downhole in a tubing disposed in a wellbore. Surface equipment injects power fluid, e.g., produced water or oil, down the tubing to the pump. The power fluid operates to drive an engine piston internally between upstrokes and down strokes which, in turn, drives a pump piston connected to the engine piston via a rod. During upstrokes, the pump draws in production fluid to an intake pump volume below the pump piston. During down strokes, the pump transfers the production fluid from the intake pump volume to a discharge pump volume above the pump piston. In a subsequent upstroke, the production fluid is discharged from the discharge pump volume via the tubing-casing annulus or some such parallel path to the surface equipment for handling. 
     Hydraulically activated pumps use the incompressible characteristic of the production liquid to transfer the production liquid from the intake volume to the discharge volume and discharge the production liquid out of the discharge volume. However, in traditional hydraulically activated pumps, when gas is drawn into the intake pump volume during an upstroke, the gas in the intake volume will simply compress and expand during the subsequent down strokes and upstrokes, thereby causing the pump to gas lock. When gas lock occurs, the pump fails to move any production liquid to the surface. 
     There is, therefore, a need for a hydraulic pump capable of preventing gas lock. 
     SUMMARY 
     Embodiments of the present disclosure generally relate to a hydraulic pump with gas lock prevention. 
     One embodiment of a pump includes a pump barrel having an intake port and a discharge port, and a pump piston movably disposed in the pump barrel. The pump piston divides an inner volume of the pump barrel into a first pump volume connected to the discharge port and a second pump volume connected to the intake port. A pump flow path is formed through the pump piston connecting the first pump volume and the second pump volume. The pump further includes a first valve disposed in the pump flow path in the pump piston. The first valve selectively permits fluid flow from the second pump volume to the first pump volume. The pump further includes a second valve disposed at the discharge port to selectively permit fluid flow out of the first pump volume through the discharge port. 
     Another embodiment provides a hydraulic pump. The hydraulic pump comprises an engine barrel and a pump barrel and an engine piston movably disposed in the engine barrel. The engine piston divides an inner volume of the engine barrel into a first engine volume and a second engine volume. The engine barrel has an engine inlet port connecting to the inner volume. The hydraulic pump further includes a pump piston movably disposed in the pump barrel. The pump piston divides an inner volume of the pump barrel into a first pump volume and a second pump volume. The first pump volume has an outlet port and the second pump volume has an intake port. The hydraulic pump further includes a middle rod connecting the engine piston and the pump piston. The middle rod has a rod passage selectively connecting the first engine volume and the first pump volume. The hydraulic pump further includes a first check valve disposed in the pump piston to control flow from the first pump volume to the second pump volume, and a second check valve disposed to control flow from the first pump volume through the outlet port of the pump barrel. 
     Another embodiment provides a method for pumping production fluid from a wellbore. The method includes stroking a pump piston disposed in a pump barrel repeatedly between an upstroke and a down stroke, wherein the pump piston divides the pump barrel into a first pump volume and a second pump volume, a pump flow path is formed through the pump piston between the first pump volume and the second pump volume, and a first check valve is disposed in the pump flow path in the pump piston. The method further includes, during each upstroke, drawing production fluid into the second pump volume through an intake port through the pump barrel and discharging fluid in the first pump volume through a second check valve disposed on a discharge port through the pump barrel. The method further includes, during each down stroke, flowing the production fluid in the second pump volume to the first pump volume through the first check valve disposed in the pump piston while the second check valve remains closed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the various aspects, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments. 
         FIG. 1A  is a schematic sectional view showing a hydraulic pump according to one embodiment of the present disclosure disposed in a wellbore. 
         FIG. 1B  is a schematic sectional view showing the hydraulic pump of  FIG. 1A  during a down stroke. 
         FIG. 2A  schematically illustrates the directions of fluid flow in the hydraulic pump of  FIG. 1A  during an upstroke. 
         FIG. 2B  schematically illustrates the directions of fluid flow of the hydraulic pump of  FIG. 1A  during a down stroke. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. The drawings referred to here should not be understood as being drawn to scale unless specifically noted. Also, the drawings are often simplified and details or components omitted for clarity of presentation and explanation. The drawings and discussion serve to explain principles discussed below, where like designations denote like elements. 
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth to provide a more thorough understanding of the present disclosure. However, it will be apparent to one of skill in the art that the present disclosure may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the present disclosure. 
       FIG. 1A  is a schematic sectional view showing one embodiment of a hydraulic pump  100  disposed in a wellbore. The hydraulic pump  100  may be used to produce production fluids from a wellbore to the surface. 
       FIG. 1A  illustrates the hydraulic pump  100  is installed downhole in tubing  20  disposed in a wellbore casing  10 . A tubing standing valve  18  may be disposed inside the tubing  20  at a lower end  20   a . The tubing stand valve  18  selectively closes a tubing volume  24  inside the tubing  20  and a production region  16  below the tubing  20 . The tubing standing valve  18  ensures that fluid flows from the production region  16  to the tubing volume  24 , not vice versa. The tubing standing valve  18  also allows retrieval of the hydraulic pump  100  by pumping power fluid through an annulus  12  between the tubing  20  and the wellbore casing  10 . One or more packer assembly  14  may be disposed between the tubing  20  and the wellbore casing  10  near the lower end  20   a  of the tubing  20 . The one or more packer assembly  14  seals the annulus  12  from the production region  16 . The tubing  20  may include one or more ports  22  near the lower end  20   a  to connect the tubing volume  24  and the annulus  12 . 
     The hydraulic pump  100  may be disposed in the tubing volume  24  near the lower end  20   a  to pump production fluid in the production region  16  to the annulus  12 . The hydraulic pump  100  may include a housing  102 . The housing  102  has an engine barrel  104  and a pump barrel  106 . A seating cup  108  may be disposed on the housing  102  between the engine barrel  104  and the pump barrel  106 . The seating cup  108  is configured to contact an inner wall of the tubing  20  and form a seal with the tubing  20 . The seating cup  108  seals a pump tubing volume  24   b  between the pump barrel  106  and the tubing  20 . The port  22  connects the pump tubing volume  24   b  to the annulus  12 . A sealing member  110  may be disposed on the housing  102  above the engine barrel  104 . The sealing member  110  is configured to contact the inner wall of the tubing  20  and form a seal with the tubing  20 . The seating cup  108  and the sealing member  110  seal an engine tubing volume  24   a  between the engine barrel  104  and the tubing  20 . 
     The hydraulic pump  100  may include an engine check valve  124  disposed above the engine barrel  104 . The engine check valve  124  allows fluid, such as a power fluid, to enter the engine tubing volume  24   a . The engine barrel  104  encloses an engine volume  112  therein. The engine barrel  104  may have an engine inlet port  126  connecting the engine volume  112  to the engine tubing volume  24   a . The engine inlet port  126  may be positioned to connect the lower engine volume  112   b  to the engine tubing volume  24   a . An engine piston  116  is movably disposed in the engine barrel  104 . The engine piston  116  divides the engine volume  112  into an upper engine volume  112   a  and a lower engine volume  112   b.    
     The pump barrel  106  encloses a pump volume  114  therein. A pump piston  118  may be movably disposed in the pump barrel  106 . The pump piston  118  divides the pump volume  114  into an upper pump volume  114   a  and a lower pump volume  114   b . A middle rod  120  is coupled between the engine piston  116  and the pump piston  118 . The middle rod  120  enables the engine piston  116  and the pump piston  118  to move in synchrony along a central axis  101  of the hydraulic pump  100 . The engine piston  116  and the pump piston  118  move back and forth along the central axis  101  changing sizes of the upper engine volume  112   a , the lower engine volume  112   b , the upper pump volume  114   a  and the lower pump volume  114   b . A rod seal  122  may be disposed inside the housing  102  between the engine barrel  104  and the pump barrel  106 . The rod seal  122  forms a seal around the middle rod  120  to fluidly isolate the pump volume  114  from the engine volume  112 . 
     In one embodiment, the engine piston  116  has an inner chamber  128  formed therein. The inner chamber  128  opens to the upper engine volume  112   a . The inner chamber  128  has an upper port  138  and a lower port  140 . The upper port  138  is connected to the lower engine volume  112   b . The lower port  140  is connected to a rod passage  130  formed through the middle rod  120 . The rod passage  130  may be connected to the upper pump volume  114   a  through one or more upper outlet  132 . 
     In one embodiment, a reversing valve  146  may be disposed in the inner chamber  128  of the engine piston  116 . The reversing valve  146  alternatively connects the upper engine volume  112   a  to the lower engine volume  112   b  and the rod passage  130 . The reversing valve  146  may include a piston  148  disposed in the inner chamber  128 . The piston  148  is movable vertically within the inner chamber  128  between an upper pressure seat  142  and a lower pressure seat  144 . When the piston  148  is in contact with the upper pressure seat  142 , the upper engine volume  112   a  is connected with the lower engine volume  112   b  through the upper port  138 . When the piston  148  is in contact with the upper pressure seat  142 , the upper engine volume  112   a  is connected with the rod passage  130  through the lower port  140 . 
     A push rod  158  may be disposed on the engine piston  116 . A bias element  160  may be attached to the push rod  158  to bias the push rod  158  away from the piston  148  of the reversing valve  146 . As the engine piston  116  moves upwards, the push rod  158  may become in contact with an upper wall  104   a  of the engine barrel  104 . The upper wall  104   a  pushes the push rod  158  and the push rod  158  compresses the bias element  160  to move downward. If the piston  148  of the reversing valve  146  is in contact with the upper pressure seat  142  when the push rod  158  is moving down, the push rod  158  contacts the piston  148  and pushes the piston  148  down to reverse the position of the reversing valve  146 . Similarly, a lower push rod  162  disposed at an opposite end of the piston  148  to push the piston  148  up when the engine piston  116  is at a lower most position and the piston  148  of the reversing valve  146  is in contact with the lower pressure seat  144 . 
     In one embodiment, the rod passage  130  may extend through the pump piston  118  and open to the lower pump volume  114   b  through a lower outlet  134 . Thus, the rod passage  130  provides a fluid communication between the lower pump volume  114   b  and the upper pump volume  114   a . A traveling valve  136  may be disposed in the pump piston  118  to selectively open the lower outlet  134 . The traveling valve  136  allows fluid flow from the lower pump volume  114   b  to the rod passage  130  and prohibits fluid flow from the rod passage  130  to the lower pump volume  114 . Alternatively, the fluid passage from the lower pump volume  114   b  to the upper pump volume  114   a  may be an independent flow path formed through the pump piston  118  and not connected to the rod passage  130 . 
     The pump barrel  106  may include an intake port  150 . The intake port  150  may be formed through a lower end of the pump barrel  106  to draw up production fluid into the lower pump volume  114   b . An intake valve  152  may be disposed in the intake port  150  to selectively open and close the intake port  150 . The intake valve  152  may be a check valve to ensure that fluid only flow into the pump volume  114  not out of the pump volume  114 . 
     The pump barrel  106  may also include a discharge port  154 . The discharge port  154  may be formed through an upper end of the pump barrel  106  to connect the upper pump volume  114   a  to the pump tubing volume  24   a . A discharge valve  156  may be disposed in the pump barrel  106  to selectively open and close the discharge port  154 . In one embodiment, the discharge valve  156  may be a disk valve having a valve body with a set of ports and a disk plate with sealing members configured to seal the set of ports in the valve body. In one embodiment, the discharge valve  156  may be disk valve including a self-cleaning mechanism configured to cause a disturbance in fluid flow within or near the valve body when the disk plate is sealing or unsealing the set of ports. The disturbance in the fluid flow may impede, remove and/or displace debris buildup on a surface of the valve body. The self-cleaning mechanism may include one or more cut outs formed a surface of the valve body in proximity to the set of ports. Alternatively, the discharge valve  156  may be any suitable valves, for example any suitable pressure activated valves, such as a ball and seat valve and a flapper valve. 
     During operation, the hydraulic pump  100  may be disposed at the lower end  20   a  of the tubing  20  with the pump barrel  106  facing the production region  16  and the engine barrel  104  away from the production region  16 . The hydraulic pump  100  may be positioned against the tubing standing valve  18 . The seating cup  108  and the sealing member  110  are pressed against the inner surface of the tubing  20  to seal off the pump tubing volume  24   b  and the engine tubing volume  24   a  from each other and from the remaining tubing volume  24  above the hydraulic pump  100 . A power fluid may be applied from surface through the tubing volume  24  to drive the engine piston  116  and the pump piston  118  up and down the engine barrel  104  and the pump barrel  106 .  FIG. 1A  schematically illustrates the hydraulic pump  100  when the engine piston  116  and the pump piston  118  are moving up, i.e. during an upstroke.  FIG. 1B  schematically illustrates the hydraulic pump  100  when the engine piston  116  and the pump piston  118  are moving down, i.e. during a down stroke. 
       FIG. 2A  schematically illustrates the directions of fluid flow during upstroke. During upstroke, the reversible valve  146  is in contact with the upper pressure seat  142  causing the inlet port  138  to be closed by the reversible valve  146  while the outlet port  140  is open. The closure of the inlet port  138  prevents fluid flow from the lower engine volume  112   b  to the upper engine volume  112   a . The opening of the outlet port  140  allows fluid flow from the upper engine volume  112   a  to the bump volume  114  through the rod passage  130 . 
     As shown in  FIG. 2A , the power fluid in the tubing volume  24  enters the engine tubing volume  24   a  through the engine check valve  124 . The power fluid then enters the lower engine volume  112   b  through the engine inlet port  126 . Because the inlet port  138  is blocked by the reversible valve  146 , the power fluid remains in the lower engine volume  112   b . The pressure of the power fluid in the lower engine volume  112   b  increases until it overcomes the pressure of the fluid in the upper engine volume  112   a , thereby moving the engine piston  116  upward. The upstroke of the engine piston  116  reduces the upper engine volume  112   a , which forces the fluid in the upper engine volume  112   a  to flow through the outlet port  140  and into the rod passage  130 . 
     The upstroke of the engine piston  116  is translated to the pump piston  118  through the middle rod  120 . Upward movement of the pump piston  118  enlarges the volume of the lower pump volume  114   b  and reduces the volume of the upper pump volume  114   a . The pressure in the lower pump volume  114   b  decreases as a result of enlarging the volume of the lower pump volume  114 . When the pressure in the lower pump volume  114   b  is lower than the pressure of the production region  16 , the check valves  18  and  152  open to draw the production fluid into the lower pump volume  114 . 
     Because the travelling valve  136  is closed during the upstroke, fluid communication between the rod passage  130  and the lower pump volume  114   b  is blocked. The fluid in the rod passage  130  enters into the upper pump volume  114   a  through the upper outlet  132  of the rod passage  130 . In this respect, the upper pump volume  114   a  contains a mixture of the production fluid and the power fluid (commingled fluid). Both the introduction of fluid into the upper pump volume  114   a  and the reduction in volume of the upper pump volume  114   a  contributes to the increase in pressure of the upper pump volume  114   a  during the upstroke. When the pressure in the upper volume  114   a  reaches the opening pressure of the discharge valve  156 , the discharge valve  156  opens to allow fluid from the upper pump volume  114   a  to exit into the pump tubing volume  24   b , then through the port  22  to the annulus  12 , and then to the surface. The expelled fluid is a mixture of production fluid and power fluid (commingled fluid). 
     As the engine piston  116  moves to its upper location, the push rod  158  will contact the top wall  104   a  of the engine barrel  104 . The push rod  158  moves relative to the engine piston  116  and compresses the bias element  160 . The push rod  158  then contacts and pushes the piston  148  of the reversing valve  146 . In response, the reversible valve  146  moves downward within the inner chamber  128 , thereby opening the inlet port  138  and closing the lower port  140 . The power fluid from the lower engine volume  112   b  flows through the inlet port  138  and into the upper engine volume  112   a . The flow of power fluid into the upper engine volume  112   a  causes the upper engine volume  112   a  to expand and the engine piston  116  to move down, thus, starting a down stroke. 
       FIG. 2B  schematically illustrates the directions of fluid flow during a down stroke. After the reversing valve  146  reverses its position at the top of an upstroke, power fluid flows from the lower engine volume  112   b  to the upper engine volume  112   a  through the inlet port  138 . The upper engine volume  112   a  expands to push down the engine piston  116  and the pump piston  118 . When the lower port  140  is closed, the upper pump volume  114   a  loses the pressure from the power fluid. The upper pump volume  114   a  also loses pressure because the upper pump volume  114   a  is expanding due to the pump piston  118  moving downward. The discharge valve  156  is closed as a result of the pressure drop in the upper pump volume  114   a . The downward movement of the pump piston  118  also reduces the volume of the lower pump volume  114   b , thereby causing the pressure in the lower pump volume  114   b  to increase. The increased pressure in lower pump volume  114   b  opens the travelling valve  136  and closes the intake valve  152 . Thus, during a down stroke, the production fluid in the lower pump volume  114   b  flows into the upper pump volume  114   a  through the travelling valve  136 . 
     When the engine piston  116  is moving downward to its bottom location, the reversing valve  146  may be reversed to open the lower port  140  and close the inlet port  138  to start the next upstroke. During the next upstroke, new production fluid may be drawn into the lower pump volume  114   a , and the production fluid in the upper pump volume  114   a  will be discharged through the discharge valve  156  along with the spent power fluid in the upper engine volume  112   a.    
     The hydraulic pump  100  according to the present disclosure has several advantages over traditional hydraulic pumps. For example, the hydraulic pump  100  is configured to prevent gas lock and is effective in high gas content wells, for example, horizontal shale well completions. As described above, during upstroke, when the production fluid in the upper pump volume  114   a  is being discharged into the annulus  12 , the upper pump volume  114   a  is in fluid communication with the upper engine volume  112   a  so that the upper pump volume  114   a  is pressurized by the power fluid in the upper engine volume  114   a . The pressure of the power fluid from the upper engine volume  112   a  provides sufficient pressure to open the discharge valve  156  to discharge the high gas content production fluid into the annulus  12 . Even if the production fluid in the lower engine volume  114   b  includes a high percentage of compressive fluid, such as gas, the discharge check valve  156  isolates the upper pump volume  114   a  from the fluid pressure in the annulus  12  to permit the fluid in the lower engine volume  114   b  to be transferred to the upper engine volume  114   a  during down stroke, thus preventing gas lock in the lower engine volume  114   b.    
     Additionally, compared to traditional pumps with gas lock preventing mechanism, the hydraulic pump  100  includes a simplified and more robust structure. Traditional gas lock preventing mechanism includes two check valves positioned next to each other on the pump barrel for intake and discharge respectively resulting in a complex structure. By using the travelling valve  136  in the pump piston  118  to control the intake of production fluid in the upper pump volume  114   a , the hydraulic pump  100  of the present disclosure provides a simplified solution for gas lock prevention. 
     While the foregoing is directed to embodiments of the present disclosure, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.