Linear pumping system and methods for controlling the same

Abstract

An example linear pumping system suitable for small size and low flow rate operation. The system includes a pump casing that encloses a linear motor and one or two (an upper and lower) pumps. The pump casing may include an upper fluid inlet port, a lower fluid inlet port, and a fluid-outlet port. The linear motor includes a stator and a mover, where the mover includes an upper plunger portion and a lower plunger portion and is configured to move alternately up and down relative to the stator. The upper and lower pumps positioned on both sides of the mover may each include a pump chamber, a fluid inlet valve, and a fluid outlet valve. In operation, hydraulic pressure from the upper and lower pump outlet valves causes fluid within an interior cavity of the pump casing to be expelled through the fluid outlet port. The motion of the mover can be controlled using pressure and/or plunger position measurements.

What is claimed is: 
     
         1 . A linear pumping system, comprising:
 (a) a pump casing having an interior cavity and at least one fluid inlet port receiving fluid from outside the pump casing, and at least one fluid outlet port expelling fluid from the interior cavity to the outside of the pump casing;   (b) a linear motor enclosed within the pump casing and including a stator and a mover, the mover including a plunger and being configured to move alternately up and down with respect to the stator; and   (c) a first pump enclosed within the pump casing and including a first pump chamber, a first pump fluid inlet valve configured to receive fluid into the first pump chamber from outside the pump casing through the at least one fluid inlet port of the pump casing, and a first pump fluid outlet valve configured to expel fluid from the first pump chamber into the interior cavity of the pump casing,   wherein the first pump chamber is configured to receive a top portion of the plunger of the linear motor mover, the received top plunger portion causing fluid to be drawn into the first pump chamber through the first pump inlet valve on a downstroke of the linear motor mover, and causing fluid to be expelled from the first pump chamber into the interior cavity of the pump casing through the first pump outlet valve on an upstroke of the linear motor mover; and   wherein hydraulic pressure from the first pump causes fluid within the interior cavity of the pump casing to be expelled through the fluid outlet port of the pump casing.   
     
     
         2 . The linear pumping system of  claim 1 , further comprising
 (d) a second pump enclosed within the pump casing and including a second pump chamber, a second pump fluid inlet valve configured to receive fluid into the second pump chamber from outside the pump casing through the at least one fluid inlet port of the pump casing, and a second pump fluid outlet valve configured to expel fluid from the second pump chamber into the interior cavity of the pump casing,   wherein the second pump chamber is configured to receive a bottom portion of the plunger of the linear motor mover, the received bottom plunger portion causing fluid to be drawn into the second pump chamber through the second pump inlet valve on an upstroke of the linear motor mover, and causing fluid to be expelled from the second pump chamber into the interior cavity of the pump casing through the second pump outlet valve on a downstroke of the linear motor mover; and   wherein hydraulic pressure from the first pump and the second pump causes fluid within the interior cavity of the pump casing to be expelled through the fluid outlet port of the pump casing.   
     
     
         3 . The linear pumping system of  claim 1 , wherein the linear motor further includes an expandable diaphragm that seals oil within the linear motor and is configured to allow the oil within the linear motor to expand or contract with temperature. 
     
     
         4 . The linear pumping system of  claim 2 , wherein the first and second pump fluid inlet valves and first and second pump fluid outlet valves are one-way valves that are configured to operate in any orientation. 
     
     
         5 . The linear pumping system of  claim 4 , wherein at least one of the first and second pump fluid inlet valves and first and second pump fluid outlet valves comprises a ball valve having a buoyant ball. 
     
     
         6 . The linear pumping system of  claim 4 , wherein at least one of the first and second pump fluid inlet valves and the first and second pump outlet valves comprises a ball valve having a metallic ball and a magnetic valve seat. 
     
     
         7 . The linear pumping system of  claim 2 , wherein the first and second pump fluid inlet ports are configured to receive fluid in a direction that is substantially perpendicular to a lengthwise direction of the first and second pump chambers. 
     
     
         8 . The linear pumping system of  claim 2 , further comprising one or more pressure sensors configured to measure pressure within at least one of the first and second pump chambers. 
     
     
         9 . The linear pumping system of  claim 8 , further comprising a motor controller that is configured to control movement of the linear motor based at least in part on pressure measured by the one or more pressure sensors. 
     
     
         10 . The linear pumping system of  claim 9 , wherein the motor controller is configured to control one or more motion parameters of the linear motor dependent on the pressure measured within at least one of the first or second pump chambers. 
     
     
         11 . The linear pumping system of  claim 2 , further comprising one or more sensors configured to determine a location of the mover in relation to at least one of the first and second pump chambers. 
     
     
         12 . The linear pumping system of  claim 11 , further comprising a motor controller configured to control a stroke length of the linear motor based at least in part on the position of the mover. 
     
     
         13 . The linear pumping system of  claim 1 , further comprising one or more temperature sensors configured to measure an operating temperature of the linear motor. 
     
     
         14 . The linear pumping system of  claim 13 , further comprising a motor controller that is configured to control one or more motion parameters of the linear motor based at least in part on the measured operating temperature of the linear motor. 
     
     
         15 . The linear pumping system of  claim 14 , wherein the motor controller is configured to stop movement of the linear motor if the measured operating temperature of the linear motor reaches a predetermined threshold. 
     
     
         16 . A method of controlling operation of a linear pumping system for use in an oil or gas well, the linear pumping system including a linear motor and one or more pump chambers, comprising:
 measuring pressure within the one or more pump chambers of the linear pumping system;   measuring a position of a plunger rod of the linear motor in relation to the one or more pump chambers; and   controlling movement of the plunger rod within the one or more pump chambers based at least in part on the measured pressure and position.   
     
     
         17 . The method of  claim 16 , wherein a stroke length of the linear motor is controlled based at least in part on the measured position to cause a maximum penetration of the plunger rod within the one or more pump chambers. 
     
     
         18 . The method of  claim 16 , wherein movement of the linear motor is stopped if the measured pressure exceeds a predetermined threshold. 
     
     
         19 . The method of  claim 16 , further comprising:
 measuring an operational temperature of the linear motor; and   controlling movement of the linear motor based at least in part on the measured operational temperature.   
     
     
         20 . The method of  claim 19 , wherein movement of the linear motor is stopped if the measured operational temperature exceeds a predetermined threshold. 
     
     
         21 . The method of  claim 16 , further comprising the step of
 using at least one of (a) pressure measurements within the one or more pump chambers and (b) linear motor temperature to provide an estimate of the fluid/gas mixture in the portion of the oil or gas well where the linear pumping system is located.