System and method for intermittent gas lift

Abstract

A gas-lift apparatus and method for use in a well in which liquids accumulate in a liquid zone. The apparatus comprises a first string extending into the liquid zone and having upper and lower ends; a second string surrounding the first string and defining an annulus therewith, the second string extending a distance from the first string lower end such that the annulus has upper and lower ends, the annulus being closed at its upper and lower ends and defining a chamber, the chamber being in fluid communication with the inside of the first string; a check valve controlling the flow of liquid into from the wellbore into the lower end of said annulus; a gas valve allowing the flow of gas from the first string into the upper end of the chamber; and a valve for controlling the flow of gas into the upper end of said inner string.

1 . An intermittent gas-lift apparatus for use in a well that produces gas and liquid, in which liquids accumulate in a liquid zone in the wellbore, comprising:
 a first string extending into the liquid zone and having an upper end and a lower end;   a second string surrounding the first string and defining an annulus therewith, said second string extending a predetermined axial distance from the first string lower end such that said annulus has an upper end and a lower end, said annulus being closed at its upper and lower ends so as to define a chamber, said chamber being in fluid communication with the inside of said first string;   a check valve controlling the flow of liquid into from the wellbore into the lower end of said annulus;   a gas valve allowing the flow of gas from the first string into the upper end of the chamber; and   a valve for controlling the flow of gas into the upper end of said first string.   
     
     
         2 . The apparatus according to  claim 1  wherein the axial length of said annulus is less than 50% of the length of said first string. 
     
     
         3 . The apparatus according to  claim 1  wherein the first string comprises coiled tubing. 
     
     
         4 . The apparatus according to  claim 1  wherein the second string comprises production tubing. 
     
     
         5 . The apparatus according to  claim 1 , further including a plunger slidably disposed in said first string. 
     
     
         6 . A method for producing gas from a well that produces gas and liquid, in which liquids accumulate in a liquid zone in the wellbore, comprising the steps of:
 a) providing in the well an apparatus comprising:
 a first string extending into the liquid zone and having an upper end and a lower end; 
 a second string surrounding the first string and defining an annulus therewith, said second string extending a predetermined axial distance from the first string lower end such that said annulus has an upper end and a lower end, said annulus being closed at its upper and lower ends so as to define a chamber, said chamber being in fluid communication with the inside of said first string; 
 a check valve controlling the flow of liquid into from the wellbore into the lower end of said annulus; 
 a gas valve allowing the flow of gas from the first string into said chamber; and 
 a valve for controlling the flow of gas through the upper end of said first string 
   b) allowing liquid to flow from the wellbore into the annulus;   c) pumping gas into the annulus via the gas valve and preventing liquid from flowing out of the annulus until a desired pressure is reached; and   d) allowing gas to flow out of the annulus via the inner string while preventing gas from flowing out of the annulus via the gas valve, such that the gas flowing out of the annulus propels a slug of liquid toward the surface.   
     
     
         7 . The method according to  claim 6  wherein the axial length of the annulus is less than 50% of the length of the first string. 
     
     
         8 . The method according to  claim 6  wherein the first string comprises coiled tubing. 
     
     
         9 . The method according to  claim 6  wherein the second string comprises production tubing. 
     
     
         10 . The method according to  claim 6 , wherein the first string includes a plunger slidably disposed therein.