Artificial lift system

Abstract

An artificial lift system provides an artificial lift design specifically for the pumping of liquids from natural gas wells, but not limited to this application. In doing so, production rates and reserves recovered can be significantly increased. The artificial lift system uses small diameter continuous tubing to run the pump in the hole and deliver small volumes of high pressure dry gas as a power fluid to the pump. This power fluid forces liquid that has been drawn into the pump from the bottom of the wellbore to surface. By removing the liquids from the wellbore the natural gas can flow unrestricted to surface. A control system for the artificial lift system delivers a pre-determined volume of power fluid to the pump on a periodic basis. Feedback mechanisms may adjust the volume and/or the period to improve the efficiency of the pump.

1 . A method of operating an artificial lift system comprising a gas pump having a surface fill valve, a pressure actuated fill valve and a bleed valve comprising the steps of:
 (a) opening and closing the surface fill valve to deliver a predetermined volume of power fluid at a pressure above a set point of a pressure actuated fill valve in order to pressurize a gas pump, wherein the set point of the pressure actuated fill valve is higher than the discharge pressure of the gas pump;   (b) closing the bleed valve with pressure downstream of the fill valve;   (c) opening the bleed valve by dissipating pressure in a bleed valve control line through a vent orifice; and   (d) repeating steps (a)-(c) as a pump cycle on a periodic basis.   
     
     
         2 . The method of  claim 1  wherein the periodic basis comprises a pump cycle is initiated on a regular time interval. 
     
     
         3 . The method of  claim 2  wherein an end-of-cycle event is used to modify the regular time interval. 
     
     
         4 . The method of  claim 3  wherein the end-of-cycle event comprises the initiation of step (c) 
     
     
         5 . The method of  claim 3  wherein the end-of-cycle event produces an acoustic signal which is detected by an acoustic monitor. 
     
     
         6 . The method of  claim 4  further comprising the step of monitoring operation of the surface fill valve and/or the bleed valve by an acoustic monitor. 
     
     
         7 . A control system for an artificial lift system comprising a gas pump having a surface fill valve, a pressure actuated fill valve and a bleed valve, the control system comprising a logic controller comprising:
 (a) a surface fill valve controller for delivering a predetermined volume of power fluid at a pressure above a set point of a pressure actuated fill valve in order to pressurize a gas pump;   (b) a timer for actuating the surface fill valve controller on a periodic basis.   
     
     
         8 . The control system of  claim 7  further comprising an acoustic sensor for detecting an end-of-cycle event, said acoustic sensor operatively connected to the logic controller to modify the timer period. 
     
     
         9 . The control system of  claim 7  wherein the end-of-cycle event is opening of the bleed valve. 
     
     
         10 . The control system of  claim 7  further comprising a fluid level determination subsystem comprising an acoustic sensor, and wherein the logic controller comprises a module for echo determination of fluid level using an end-of-cycle acoustic event. 
     
     
         11 . The control system of  claim 7  further comprising a diagnostic acoustic sensor for detecting valve operation events, said acoustic sensor operatively connected to the logic controller to provide valve operation status.