Hydraulically operated wellbore liquid lift using casing gas as energy source

Abstract

A system for lifting liquid from a wellbore includes a turbine selectively coupled to a source of gas flow originating in the wellbore. The turbine is arranged to convert the gas flow directly into rotation of the turbine. An hydraulic pump is rotationally coupled to the turbine. An hydraulic cylinder and piston are arranged to move a sucker rod string disposed in the wellbore. Control valves are provided to selectively apply gas flow to the turbine and hydraulic pressure from the pump to lift the piston and enable lowering thereof by the weight of the sucker rod string. The system further comprises control circuits configured to operate the control valves.

1 . A system for lifting liquid from a wellbore, comprising:
 a turbine selectively coupled to a source of gas flow originating in the wellbore, the turbine arranged to convert the gas flow directly into rotation of the turbine;   an hydraulic pump rotationally coupled to the turbine;   an hydraulic cylinder and piston arranged to move a sucker rod string disposed in the wellbore;   control valves to selectively apply gas flow to the turbine and hydraulic pressure from the pump to lift the piston and enable lowering thereof by the weight of the sucker rod string; and   control circuits configured to operate the control valves.   
     
     
         2 . The system of  claim 1  wherein the control valves comprise a gas supply control valve to cause turbine rotation when the sucker rod string requires lifting. 
     
     
         3 . The system of  claim 1  wherein the control valves comprise a controllable orifice valve in a line connecting the hydraulic cylinder to a reservoir, the controllable orifice valve arranged to enable lowering of the sucker rod string at a selected rate. 
     
     
         4 . The system of  claim 1  further comprising an accumulator in hydraulic communication with an intake side of the hydraulic pump, the accumulator charged to a selected pressure and configured to recharge using hydraulic fluid displaced from the cylinder when the sucker rod string is allowed to drop. 
     
     
         5 . A method for lifting liquid from a wellbore, comprising:
 converting flow of gas from a wellbore directly into rotational energy using a turbine disposed in the gas flow;   converting the rotational energy into reciprocating motion; and   using the reciprocating motion to operate a sucker rod string disposed in the wellbore.   
     
     
         6 . The method of  claim 5  wherein the converting rotational energy comprises rotating an hydraulic pump, and selectively directing pressure output from the hydraulic pump to an hydraulic cylinder/piston combination coupled to the sucker rod string. 
     
     
         7 . The method of  claim 6  further comprising stopping rotation of the hydraulic pump, and selectively controlling rate of discharge of hydraulic fluid from the cylinder/piston combination to enable dropping the sucker rod string at a selected rate. 
     
     
         8 . The method of  claim 6  further comprising prepressurizing the pump with pressure stored in an accumulator to at least partially offset a weight of the sucker rod string. 
     
     
         9 . The method of  claim 5  wherein the flow of gas from the wellbore is from an annular space between a wellbore casing and a wellbore tubing disposed within the wellbore casing.