Accumulation and recycling of captured gas in recovery of subterranean fluids

Abstract

A system and method for capturing lift gas in wells with small formation gas production. The system includes a separator for separating gases from wellbore fluid and a vessel for accumulating the separated gas. The system also includes a switch that directs fluid from the vessel to a wellbore upon attainment of a condition, such as a certain pressure in the vessel. The method includes the steps of separating gas from a wellbore fluid, directing the gas to an accumulation vessel, and directing the gas from the vessel to a wellbore upon attainment of a condition, such as a certain pressure in the vessel.

1 . A gas lift supply apparatus, comprising:
 a separator for separating a wellbore fluid into a gas stream and a remaining fluid stream;   a vessel for storing the gas from the separator; and   a switch operatively connected to the vessel, wherein the switch directs a portion of the gas from the vessel to a lift gas injection apparatus upon the attainment of a first pressure condition relating to the vessel.   
   
   
       2 . The apparatus of  claim 1 , wherein the lift gas injection apparatus comprises a compressor for compressing the gas and injecting the gas into a wellbore or a portion thereof. 
   
   
       3 . The apparatus of  claim 1 , wherein the switch stops directing the gas from the vessel upon the attainment of a second pressure condition relating to the vessel, the second pressure condition being lower that the first pressure condition. 
   
   
       4 . The apparatus of  claim 3 , wherein the first pressure condition is less than about 200 psi and the second pressure condition is less than about 100 psi. 
   
   
       5 . The apparatus of  claim 3 , wherein the first pressure condition is less than about 100 psi and the second pressure condition is less than about 50 psi. 
   
   
       6 . The apparatus of  claim 1 , wherein the wellbore fluid comprises a gas concentration less than about 50 standard cubic feet of gas per barrel of wellbore fluid. 
   
   
       7 . The apparatus of  claim 1 , wherein the wellbore fluid comprises a gas concentration less than about 20 standard cubic feet of gas per barrel of wellbore fluid. 
   
   
       8 . The apparatus of  claim 1 , wherein the wellbore fluid comprises a gas concentration less than about 10 standard cubic feet of gas per barrel of wellbore fluid. 
   
   
       9 . The apparatus of  claim 2 , further comprising a first conduit leading from the compressor to the wellbore; and
 a second conduit branching from the first conduit and leading to a high pressure vessel for storage of excess lift gas.   
   
   
       10 . The apparatus of  claim 1 , wherein the switch comprises a valve assembly. 
   
   
       11 . The apparatus of  claim 1 , further comprising a production string in the wellbore; and
 a gas lift valve connected to the production string for directing the gas injected into the wellbore into the production string.   
   
   
       12 . A method for supplying lift gas to a wellbore, comprising:
 separating a wellbore fluid into a gas component and a remaining fluids component;   collecting the gas in a vessel; and   directing a portion of the gas from the vessel to a wellbore or a portion thereof upon attainment of a first pressure condition relating to the vessel.   
   
   
       13 . The method of  claim 12 , wherein the directing step comprises directing the gas from the vessel to a compressor and from the compressor into the wellbore. 
   
   
       14 . The method of  claim 13 , further comprising continuing the directing step until the attainment of a second pressure condition relating to the vessel. 
   
   
       15 . The method of  claim 14 , further comprising repeating the steps of separating, collecting, directing, and continuing until the gas directed to the wellbore enters into a production tubing stream as a lift gas. 
   
   
       16 . The method of  claim 12 , wherein the wellbore fluid comprises a gas concentration less than about 50 standard cubic feet of gas per barrel of wellbore fluid. 
   
   
       17 . The method of  claim 12 , wherein the wellbore fluid comprises a gas concentration less than about 20 standard cubic feet of gas per barrel of wellbore fluid. 
   
   
       18 . The method of  claim 12 , wherein the wellbore fluid comprises a concentration of gas less than about 10 standard cubic feet of gas per barrel of wellbore fluid. 
   
   
       19 . The method of  claim 12 , wherein the step of directing a portion of the gas from the vessel to a wellbore comprises directing the gas portion into an annulus between a wellbore casing and a wellbore production tubular. 
   
   
       20 . The method of  claim 12 , wherein the step of directing a portion of the gas from the vessel to a wellbore comprises directing the gas portion into a lift gas tubular in the wellbore. 
   
   
       21 . The method of  claim 12 , further comprising charging the wellbore or the vessel or both with a charge gas from a portable charge gas source containing less than about 25,000 standard cubic feet of charge gas. 
   
   
       22 . The method of  claim 15 , further comprising recycling all or substantially all of the lift gas by separating the lift gas from the well fluids;
 directing a first volume of the separated lift gas to the compressor and from the compressor to the wellbore, wherein the first volume is less than or equal to the maximum gas capacity of the compressor; and   directing a second volume of the separated lift gas to the vessel, wherein the second volume is approximately the difference between the total volume of separated lift gas the first volume.   
   
   
       23 . A method for supplying lift gas to a wellbore, comprising:
 providing a wellbore with a casing and a production string inside the casing;   placing at least one gas lift valve on the production string;   channeling wellbore fluids from the wellbore to a separator;   separating a gas from the wellbore fluids;   collecting the gas in a low pressure vessel;   directing a portion the gas from the low pressure vessel to an annulus between the wellbore casing and the wellbore production string upon attainment of a first pressure condition relating to the vessel, wherein the directed gas does not have sufficient volume to enter the wellbore production string through the gas lift valve; and   repeating the steps of separating, collecting, and directing until the total volume of gas directed from the vessel has sufficient volume to enter the wellbore production string as a lift gas via the gas lift valve.   
   
   
       24 . The method of  claim 23 , wherein the wellbore fluid comprises a gas concentration less than about 10 standard cubic feet of gas per barrel of wellbore fluid. 
   
   
       25 . The method of  claim 23 , further comprising charging the wellbore or the vessel or both with a charge gas from a portable charge gas source containing less than about 25,000 standard cubic feet of charge gas. 
   
   
       26 . The method of  claim 23 , further comprising recycling all or substantially all of the lift gas by separating the lift gas from the well fluids;
 directing a first volume of the separated lift gas to the compressor and from the compressor to the wellbore, wherein the first volume is less than or equal to the maximum gas capacity of the compressor; and   directing a second volume of the separated lift gas to the vessel, wherein the second volume is approximately the difference between the total volume of separated lift gas the first volume.