Long-stroke deep-well pumping unit

Abstract

Methods and apparatus for driving a positive displacement pump disposed within a wellbore are disclosed herein. Embodiments of the present invention provide a drive mechanism for driving the downhole positive displacement pump. In embodiments of the present invention, the positive displacement pump is hydraulically driven and mechanically counterbalanced. The drive mechanism may be mechanically or electrically controlled, or may be controlled by a combination of mechanical and electrical controls.

1 . A drive mechanism for a downhole, reciprocating positive displacement pump, comprising: 
 a hydraulic drive comprising a plurality of variable flow hydraulic pumps operatively connected to a reversible rotary drive motor with a closed-loop, hydraulic circuit; and    a reciprocating counterbalance,    wherein the hydraulic drive is capable of dictating the pumping rate of the downhole positive displacement pump and the reciprocating counterbalance is capable of balancing a load on a rod string of the downhole positive displacement pump and the drive mechanism.    
   
   
       2 . The drive mechanism of  claim 1 , further comprising a plurality of powering mechanisms which are capable of cooperating with the hydraulic pumps and the drive motor to provide power for rotation of the drive motor.  
   
   
       3 . A drive mechanism for a downhole, reciprocating positive displacement pump, comprising: 
 a hydraulic drive comprising a piston pump operatively connected to a reversible, variable-speed electric motor; and    a reciprocating counterbalance,    wherein the hydraulic drive is capable of dictating the pumping rate of the downhole positive displacement pump and the reciprocating counterbalance is capable of balancing a load on a rod string of the downhole positive displacement pump and the drive mechanism.    
   
   
       4 . A drive mechanism for a downhole, reciprocating positive displacement pump, comprising: 
 a hydraulic drive comprising a pump having a vane motor operatively connected to a reversible, variable-speed electric motor; and    a reciprocating counterbalance,    wherein the hydraulic drive is capable of dictating the pumping rate of the downhole positive displacement pump and the reciprocating counterbalance is capable of balancing a load on a rod string of the downhole positive displacement pump and the drive mechanism.    
   
   
       5 . A drive mechanism for a downhole, reciprocating positive displacement pump, comprising: 
 a hydraulic drive comprising a variable flow hydraulic pump operatively connected to a reversible, variable-speed electric motor; and    a hydraulic counterbalance,    wherein the hydraulic drive is capable of dictating the pumping rate of the downhole positive displacement pump and the hydraulic counterbalance is capable of balancing a load on a rod string of the downhole positive displacement pump and the drive mechanism.    
   
   
       6 . The drive mechanism of  claim 5 , wherein the hydraulic counterbalance is an accumulator.  
   
   
       7 . The drive mechanism of  claim 6 , wherein the accumulator is capable of reducing an amount of power expended by the hydraulic drive during reciprocation.  
   
   
       8 . A drive mechanism for a downhole, reciprocating positive displacement pump, comprising: 
 a hydraulic drive comprising a variable flow hydraulic pump operatively connected to a reversible rotary drive motor with a closed-loop, hydraulic circuit; and    a counterbalance reciprocatable downhole;    wherein the hydraulic drive is capable of dictating the pumping rate of the downhole positive displacement pump and the reciprocating counterbalance is capable of balancing a load on a rod string of the downhole positive displacement pump and the drive mechanism.    
   
   
       9 . A method of driving a downhole positive displacement pump, comprising: 
 providing a drive mechanism comprising a hydraulic drive having a closed-loop hydraulic circuit;    providing the downhole positive displacement pump comprising a piston reciprocatable within a cylinder, wherein the hydraulic drive is operatively connected to the piston;    operating the hydraulic drive to pump downhole fluid using the positive displacement pump;    counterbalancing a load of the downhole fluid and the piston using a hydraulic counterbalance; and    controlling the speed and direction of reciprocation of the piston within the cylinder using the drive mechanism.    
   
   
       10 . The method of  claim 9 , wherein the hydraulic counterbalance is an accumulator capable of storing and releasing energy expended by the hydraulic drive during reciprocation.