Artificial Lift Mechanisms

Abstract

The invention relates to electric linear motors and gas springs in reciprocating pumps for oil wells. By the use of this invention a simple, silent, compact and adaptable mechanism can be constructed to drive a wide range of such pumps. The mechanism will sense a variety of pumping conditions and react automatically thereto.

1 . Method of driving a reciprocating pump or an artificial lift device, having a linear electric motor and at least one gas spring, comprising controlling a mass of gas in the at least one gas spring in accordance with current demands of the linear electric motor, integrated over a plurality of complete operating cycles of the reciprocating pump or artificial lift device. 
     
     
         2 . Method of  claim 1 , further comprising supporting at least a part of a deadweight of a rod or rod string connecting the linear electric motor to the reciprocating pump or artificial lift device with the gas spring. 
     
     
         3 . (canceled) 
     
     
         4 . Method of  claim 1 , wherein gas in the at least one gas spring is an inert gas. 
     
     
         5 . Method of  claim 1 , wherein the linear electric motor is arranged to raise and lower an extendible member, arranged to pass through a sliding gas seal in an upper part of a chamber, containing or forming part of the linear electric motor, said chamber being filled with an inert gas under pressure so as to form a combined linear electric motor and gas spring. 
     
     
         6 . Method of  claim 5 , wherein a topmost part of the combined linear electric motor and gas spring is fitted with a protective cover for protecting a surface of the extendible member where it emerges from a pressurized enclosure containing the linear electric motor. 
     
     
         7 . Method of  claim 5 , wherein an intermediate chamber is associated with the gas spring and connected thereto with an electrically-operated valve. 
     
     
         8 . Method of  claim 7 , wherein a transducer is arranged to measure a differential pressure across the valve, the intermediate chamber being connected via an electrically-operated source valve to a source of pressurized inert gas and via a second valve to the outside atmosphere. 
     
     
         9  Method of  claim 8 , wherein the valve, source valve and second valve are operated in accordance with algorithms related to current demands of the linear electric motor, a motion of a reciprocating thrust tube and differential pressures measured by the transducer, to utilize and to conserve an inert gas supply. 
     
     
         10 . Method of  claim 9 , wherein measured values of instantaneous current demands of the linear electric motor are mathematically processed to calculate at least key parameters of a pumping operation, detect faults and anomalies, initiate appropriate automatic responses, prepare information for transmission to a remote site and combinations thereof. 
     
     
         11 . An apparatus for pumping a liquid from a deep shaft or borehole comprising:
 a linear electric motor; and   a gas spring counter balance for cooperation with said linear electric motor to remove deadload forces from said linear electric motor and for storing and recycling energy to minimize dynamic power consumption.   
     
     
         12 . The apparatus in accordance with  claim 11 , wherein a mass of gas in said gas spring is varied in accordance with an integrated electric current consumption of said linear electric motor. 
     
     
         13 . The apparatus in accordance with  claim 11 , wherein said apparatus is arranged to be both fully autonomous and remotely controllable. 
     
     
         14 . A method for pumping a liquid from a deep shaft or borehole comprising:
 providing an apparatus as defined in  claim 11 ;   connecting the apparatus via a rod string to a pump positioned within the deep shaft or borehole;   supplying controlled electric power to the apparatus; and   recovering the liquid.   
     
     
         15 . Method of  claim 1 , further comprising storing energy in the gas spring during part of its motion. 
     
     
         16 . Method of  claim 15 , further comprising releasing energy stored in the gas spring, thereby assisting a motion of the reciprocating pump or artificial lift device, thereby reducing electrical power demand of the reciprocating pump or artificial lift device. 
     
     
         17 . Apparatus for pumping liquid comprising:
 a motor adapted to be connected with a rod;   a spring containing a fluid and cooperatively connected with said motor, and adapted to support at least part of a deadweight of the rod;   wherein a mass of the fluid in said spring is controlled in accordance with current demands of said motor.   
     
     
         18 . Apparatus of  claim 17 , wherein the fluid is an inert gas. 
     
     
         19 . Apparatus of  claim 17 , wherein the rod is configured to pass through a seal in a chamber defining said spring. 
     
     
         20 . Apparatus of  claim 17 , further comprising:
 an intermediate chamber;   a first valve for providing selectable fluid communication between said intermediate chamber and said spring; and one or both of:   a second valve for providing selectable fluid communication between said intermediate chamber and a fluid source; and   a third valve for providing selectable fluid communication between said intermediate chamber and the atmosphere.   
     
     
         21 . Apparatus of  claim 20 , further comprising a transducer for detecting a pressure differential across said first valve. 
     
     
         22 . Apparatus of  claim 21 , wherein any or all of said first valve, said second valve and said third valve are operated in accordance with algorithms related to current demands of said motor, a motion of said rod, and the differential pressure to utilize and to conserve fluid. 
     
     
         23 . Apparatus of  claim 17 , wherein measured values of instantaneous current demands of said motor are mathematically processed to calculate at least key parameters of a pumping operation, detect faults and anomalies thereof, initiate appropriate automatic responses, prepare information for transmission to a remote site, and combinations thereof.