Discharge pressure actuated pump

Abstract

A pump has a pump barrel formed from a larger diameter section and a smaller diameter section. Each section has a biased piston moveable within the section and the pistons are connected together to form a variable volume chamber between the pistons. As the connected pistons move toward the larger diameter section, a volume of fluid is moved through an inlet valve into the variable volume chamber of increasing volume. When the pistons are moved toward the smaller diameter section, a differential volume of fluid is discharged from the variable volume chamber of decreasing volume through a discharge valve into a discharge conduit. The pistons are actuated to move within the pump barrel by application and release of pressure at a remote end of the discharge conduit.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
         1 . A fluid apparatus comprising:
 a pump barrel having a first barrel section in fluid communication with a fluid source and a second barrel section in fluid communication with a discharge conduit;   a first piston housed in the first barrel section for axial movement therein;   a second piston housed in the second barrel section for axial movement therein in response to application of an actuating pressure to the discharge conduit, the first and second pistons defining a variable volume chamber between the first and second pistons;   a biasing element coupled to at least one of the first and second pistons;   an inlet check valve operable to permit fluid to flow from the fluid source into the variable volume chamber;   an outlet check valve operable to permit fluid to flow from the variable volume chamber into the discharge conduit; and   a connector between the first and second pistons, the connector being operably configured to cause movement of the first piston in response to movement of the second piston caused by the actuating pressure, the respective movements of the first and second pistons being operable to increase the volume of the variable volume chamber thereby drawing fluid into the chamber through the inlet check valve while causing energy to be stored in the biasing element, the stored energy in the biasing element being subsequently operable to cause return movement of the first and second pistons when the actuating pressure is decreased, the return movement of the first and second pistons being operable to reduce the volume of the variable volume chamber thereby causing fluid to be discharged from the chamber through the outlet check valve.   
     
     
         2 . The apparatus of  claim 1  wherein the biasing element comprises a liquid spring comprising a sealed chamber operable to hold a compressible fluid and a displacing element operable to be received in the sealed chamber to reduce the volume thereof. 
     
     
         3 . The apparatus of  claim 2  wherein the sealed chamber comprises a port operable to allow passage therethrough of at least a portion of the displacing element. 
     
     
         4 . The apparatus of  claim 2  wherein a distal end of the displacing element received in the sealed chamber is substantially of the same diameter as the port. 
     
     
         5 . The apparatus of  claim 2  wherein the displacing element comprises a spring rod received in the sealed chamber and adapted to avoid buckling when an unsupported free end of the spring rod is maximally extended into the sealed chamber during operation. 
     
     
         6 . The apparatus of  claim 2  wherein the displacing element comprises a spring rod connected to the first piston. 
     
     
         7 . The apparatus of  claim 2  wherein the displacing element received in the sealed chamber does not comprise a piston. 
     
     
         8 . The apparatus of  claim 2  wherein the sealed chamber comprises cylindrical side walls and wherein each portion of the displacing element received in the sealed chamber during operation is equally spaced apart from a corresponding portion of the cylindrical side walls, as viewed in a transverse sectional view. 
     
     
         9 . The apparatus of  claim 2  wherein the displacing element comprises a compressible fluid contacting portion for contacting the compressible fluid in the sealed chamber, the entire compressible fluid contacting portion having a substantially constant diameter. 
     
     
         10 . The apparatus of  claim 2  wherein the port comprises a chamber seal made of a material unlike that of the compressible liquid. 
     
     
         11 . The apparatus of  claim 10  wherein the chamber seal comprises a nitrile T-seal. 
     
     
         12 . The apparatus of  claim 10  wherein the chamber seal has backups and a wiper. 
     
     
         13 . The apparatus of  claim 2  wherein the sealed chamber comprises a standard API pump barrel. 
     
     
         14 . The apparatus of  claim 2  wherein the compressible fluid has a compressibility of about 0.01% per bar of pressure at an operating temperature of about 40 degrees C. 
     
     
         15 . The apparatus of  claim 1  wherein the biasing element comprises a top end and a bottom end, the top end being proximate to one of the first and second pistons. 
     
     
         16 . The apparatus of  claim 1  wherein the inlet check valve is integral with the first piston and the outlet check valve is integral with the second piston. 
     
     
         17 . The apparatus of  claim 1  wherein the biasing element is disposed between the first and second pistons. 
     
     
         18 . A method for producing accumulated liquids from a gas well, comprising:
 positioning a fluid apparatus in the wellbore and forming an annulus therebetween, the apparatus comprising a pump barrel having:   a first barrel section in fluid communication with a fluid source and a second barrel section in fluid communication with a discharge conduit, the first barrel section having a diameter greater than the second barrel section, the first and second barrel sections being fluidly connected therebetween;   a first piston housed in the first barrel section for axial movement therein;   a second piston housed in the second barrel section for axial movement therein;   a connector between the first and second pistons for concurrent axial movement within the pump barrel between an inlet position and a discharge position, the first and second pistons being spaced apart for forming a chamber of variable volume therebetween, the first and second pistons being biased to the discharge position;   an inlet check valve to permit fluid to move from the fluid source to the variable volume chamber; and   an outlet check valve to permit fluid to move from the variable volume chamber to the discharge conduit,   wherein when an actuating pressure, sufficient to overcome a biasing force, is applied to the second piston through the discharge conduit, the outlet valve closes and the first and second pistons move to the inlet position and increase the variable volume chamber by a differential volume, opening the inlet valve and permitting the flow of the differential volume of fluid from the fluid source through the inlet valve into the variable volume chamber; and   when the actuating pressure is released, the first and second pistons are biased to the discharge position for displacing the differential volume of fluid from the variable volume chamber, closing the inlet valve and opening the outlet valve for discharging the differential volume of fluid through the outlet valve to the discharge conduit;   producing gas to surface through the annulus, liquid accumulating in the wellbore adjacent the distal end of the conduit;   applying an actuating pressure at the discharge conduit such that when the force of the actuating pressure is greater than the force exerted by the biasing means and a force of pressure at the fluid source, the discharge valve operates to the closed position, the first and second pistons move to the inlet position and the inlet valve operates to the open position for charging the accumulated fluids from the wellbore into the variable volume chamber; and   releasing the actuating pressure so that the first and second pistons are biased to return to the discharge position, the inlet valve moving to the closed position, the discharge valve moving to the open position and pumping the differential volume from the variable volume chamber through the discharge valve to the discharge conduit.   
     
     
         19 . The method of  claim 18  further comprising activating the fluid apparatus at regular predetermined intervals in response to data representing historical liquid accumulation for a particular reservoir type. 
     
     
         20 . The method of  claim 18  further comprising, actuating the fluid apparatus in response to a remote sensor operable to sense fluid accumulation in the wellbore.