Active intake pressure control of downhole pump assemblies

Abstract

Progressive cavity pump assemblies including one or more mechanisms adapted to regulate intake pressure of the main pump between a minimum intake pressure and a maximum intake pressure. In one embodiment, the mechanism is a sealing member configured to open at a threshold pressure to discharge wellbore fluid and close after falling below the threshold pressure. In an alternative embodiment, the mechanism may be a regulator assembly that adjusts the volume of output from the charge pump to the interconnect according to the pressure in the interconnect.

1 . A pump assembly comprising:
 a charge pump having an intake port and an outlet port;   an interconnect having an intake port and an outlet port, with the intake port connected to the outlet port of the charge pump; and   a main pump having an intake port and an outlet port, with the intake port connected to the outlet port of the interconnect;   wherein the interconnect comprises at least one mechanism adapted to regulate an intake pressure of the main pump between a minimum intake pressure and a maximum intake pressure.   
   
   
       2 . The pump assembly of  claim 1  wherein the at least one mechanism adapted to regulate an intake pressure of the main pump between a minimum intake pressure and a maximum intake pressure comprises one or more sealing members configured to open at a threshold pressure to discharge wellbore fluid from the interconnect. 
   
   
       3 . The pump assembly of  claim 2 , wherein the one or more sealing members is a pressure relief valve, the pressure relief valve comprising:
 a substantially cylindrical first housing member having an axial passage therethrough, the first housing member disposed in the pressure relief port so as to seal the annulus between the first housing member and the pressure relief port, wherein a first end of the passage is in fluid communication with the exterior of the interconnect and a second end of the passage is in fluid communication with the interior of the interconnect; the first housing member having a first housing port in the curved surface of the first housing member connecting the passage and the interior of the interconnect;   a substantially cylindrical second housing member slideably disposed within the first housing member between the first housing port and the second end of the passage in the first housing member so as to seal the annulus between the first housing member and the second housing member and separate the first and second ends of the passage in the first housing member, the second housing member having a second housing port in the curved surface of the second housing member and the second housing member having a passage therethrough, with a first end of the passage in the second housing member being in fluid communication with the first end of the passage in the first housing member and a second end of the passage in the second housing member is in fluid communication with a second housing port in the curved surface of the second housing member and the second housing member being slidingly configurable within the first housing member so that in a closed configuration the first and second housing ports are not aligned and in an open configuration the first and second housing ports are aligned; and   a biasing member that operates against the first and second housing members to urge the pressure relief valve closed;   
     wherein an interconnect interior pressure operates on the second housing member to urge the pressure relief valve open. 
   
   
       4 . The pump assembly of  claim 2 , wherein one or more sealing members is a stopper comprising:
 a substantially cylindrical manifold having a first end proximate to the charge pump and a second end farther away from the charge pump in fluid communication with one or more stopper ports in the manifold, the manifold being coaxially mounted in the interconnect and moveable along the longitudinal axis of the interconnect to at least a closed configuration where the stopper port is not aligned with a pressure relief port and an open configuration where the stopper port is aligned with pressure relief port;   a surface attached to the manifold; and   a biasing member that operates against the manifold that urges the manifold closed;   
     wherein an interconnect interior pressure operates on the surface of the manifold to urge the manifold open. 
   
   
       5 . The pump assembly of  claim 4 , wherein the substantially cylindrical manifold comprises:
 a plurality of stopper ports, where a first stopper port is smaller than a second stopper port; and   
     wherein the first and second stopper ports are located in the manifold so that the interconnect interior pressure operates on the surface of the manifold to urge the manifold along the longitudinal axis of the interconnect from the closed configuration first to a first open configuration where the first stopper port is aligned with a pressure relief port and then to a second open configuration where the second stopper port is aligned with a pressure relief port. 
   
   
       6 . The pump assembly of  claim 4 , wherein the interconnect further comprises:
 a plurality of pressure relief ports, where a first pressure relief port is smaller than a second pressure relief port; and   
     wherein the first and second pressure relief ports are located in the interconnect so that the interconnect interior pressure operates on the surface of the manifold to urge the manifold along the longitudinal axis of the interconnect from the closed configuration first to a first open configuration where a stopper port is aligned with the first pressure relief port and then to a second open configuration where a stopper port is aligned with the second pressure relief port. 
   
   
       7 . The pump assembly of  claim 2 , wherein the one or more sealing members comprises a flap assembly comprising:
 a flap for blocking the pressure relief port attached to an exterior surface of the interconnect by a hinge; and   a biasing member that biases the flap against the exterior surface of the interconnect to block the pressure relief port   
     wherein an interconnect interior pressure operates on the flap to urge the flap away from the pressure relief port. 
   
   
       8 . The pump assembly of  claim 2 , wherein the one or more sealing members comprise a pliable bladder disposed within the interconnect having one or more slits aligned with the one or more pressure relief ports, the slits being configured to open at a threshold pressure to discharge wellbore fluid. 
   
   
       9 . The pump assembly of  claim 2 , wherein the at least one mechanism adapted to regulate an intake pressure of the main pump between a minimum intake pressure and a maximum intake pressure comprises multiple sealing members, wherein at least two of the sealing members are configured to open at different threshold pressures, so that more wellbore fluid is discharged as the intake pressure of the main pump exceeds each different threshold pressure. 
   
   
       10 . The pump assembly of  claim 9 , wherein the one or more sealing members is a pressure relief valve, the pressure relief valve comprising:
 a substantially cylindrical first housing member having an axial passage therethrough, the first housing member disposed in the pressure relief port so as to seal the annulus between the first housing member and the pressure relief port, wherein a first end of the passage is in fluid communication with the exterior of the interconnect and a second end of the passage is in fluid communication with the interior of the interconnect; the first housing member having a first housing port in the curved surface of the first housing member connecting the passage and the interior of the interconnect;   a substantially cylindrical second housing member slideably disposed within the first housing member between the first housing port and the second end of the passage in the first housing member so as to seal the annulus between the first housing member and the second housing member and separate the first and second ends of the passage in the first housing member, the second housing member having a second housing port in the curved surface of the second housing member and the second housing member having a passage therethrough, with a first end of the passage in the second housing member being in fluid communication with the first end of the passage in the first housing member and a second end of the passage in the second housing member is in fluid communication with a second housing port in the curved surface of the second housing member and the second housing member being slidingly configurable within the first housing member so that in a closed configuration the first and second housing ports are not aligned and in an open configuration the first and second housing ports are aligned; and   a biasing member that operates against the first and second housing ports to urge the pressure relief valve closed;   
     wherein an interconnect interior pressure operates on the second housing member to urge the pressure relief valve open. 
   
   
       11 . The pump assembly of  claim 9 , wherein the one or more sealing members comprises a flap assembly comprising:
 a flap for blocking the pressure relief port attached to an exterior surface of the interconnect by a hinge; and   a biasing member that biases the flap against the exterior surface of the interconnect to block the pressure relief port   
     wherein an interconnect interior pressure operates on the flap to urge the flap away from the pressure relief port. 
   
   
       12 . A pump assembly comprising:
 a charge pump having an intake port and an outlet port;   an interconnect having an intake port and an outlet port, with the intake port connected to the outlet port of the charge pump; and   a main pump having an intake port and an outlet port, with the intake port connected to the outlet port of the interconnect;   wherein the pump assembly comprises at least one mechanism outside of the interconnect adapted to regulate an intake pressure of the main pump between a minimum intake pressure and a maximum intake pressure.   
   
   
       13 . The pump assembly of  claim 12 , wherein the at least one mechanism adapted to regulate an intake pressure of the main pump between a minimum intake pressure and a maximum intake pressure comprises at least one mechanism adapted to regulate the volume of output from the charge pump to the interconnect according to the pressure in the interconnect. 
   
   
       14 . The pump assembly of  claim 13  wherein the charge pump comprises a rotor aligned for longitudinal insertion within a stator, and the mechanism comprises
 a biasing member that axially biases the rotor within the stator;   a guide on which the stator may move axially; and   a chamber connected to the stator that expands upon an increase in pressure in the chamber such that the rotor is drawn out of the stator.   
   
   
       15 . A regulator assembly adapted for incorporation in a downhole pump assembly to regulate the volume of output from a charge pump to an interconnect according to the pressure in the interconnect, with the charge pump having a stator and a rotor aligned for longitudinal insertion within the stator, the regulator assembly comprising:
 a biasing member that axially biases the rotor within the stator; and   a guide on which the stator may move axially.   
   
   
       16 . The regulator assembly of  claim 15  wherein the guide is connectable to the interconnect, the regulator assembly further comprising an adaptor for connection to the stator to form an expandable pressurizable chamber. 
   
   
       17 . The regulator assembly of  claim 16  wherein the biasing member is configured so that upon nominal operating pressure the rotor is substantially within the stator. 
   
   
       18 . The regulator assembly of  claim 16  wherein the biasing member is damped. 
   
   
       19 . The regulator assembly of  claim 15  further comprising a chamber connected to the stator that expands upon an increase in pressure in the chamber to push the stator such that the rotor is drawn out of the stator. 
   
   
       20 . The regulator assembly of  claim 19  wherein the biasing member is configured so that upon nominal operating pressure the rotor is substantially within the stator. 
   
   
       21 . The regulator assembly of  claim 19  wherein the biasing member is damped. 
   
   
       22 . A regulator assembly adapted for incorporation in a downhole pump assembly to regulate the volume of output from a charge pump to an interconnect according to the pressure in the interconnect, the regulator assembly comprising:
 a gearbox linking the drive shaft to the stator;   an actuator for selecting a gear of the gearbox;   a pressure sensor; and   a controller operatively coupled to the pressure sensor and the actuator so as to select a lower gear upon a first threshold pressure being registered by the pressure sensor and select a higher gear upon a second threshold pressure being registered by the pressure sensor.   
   
   
       23 . The regulator assembly of  claim 22  wherein the first and second threshold pressures are identical. 
   
   
       24 . The regulator assembly of  claim 22  wherein the second threshold pressure is lower than the first threshold pressure.