Gas lift optimization process

Abstract

A system, method and process (utility) is presented to control a gas injection setpoint of a production well utilizing gas lift. The utility may control a flow valve and/or source of injection gas (e.g., gas injection compressor) to increase or decrease a gas injection flow rate (e.g., setpoint) into the well during a gas injection interval. The utility monitors bottom hole pressure related values for multiple gas injection intervals with each have different gas injection setpoints (e.g., flow volumes). Bottom Hole Pressures (e.g., averages). The differences between the Bottom Hole Pressures are compared to calculate Bottom Hole Pressure Drawdown (BHPD) rates between intervals. A subsequent gas injection setpoint (e.g., direction and/or magnitude of change) is selected based on a comparison of a current BHPD and a previous BHPD.

What is claimed is: 
     
         1 . A process for adjusting a gas injection setpoint for a well utilizing gas lift, comprising:
 identifying a first Bottom Hole Pressure Drawdown (BHPD) between an end of a first gas injection interval having a first gas injection setpoint and an end of a second gas injection interval having a second gas injection setpoint;   identifying a second BHPD between an end of a third gas injection interval having a third gas injection setpoint and the end of the second gas injection interval;   comparing the second BHPD to the first BHPD; and   adjusting a gas injection setpoint for a subsequent gas injection interval based on the comparison.   
     
     
         2 . The process of  claim 1 , further comprising:
 maintaining gas flow into a well at the first gas injection setpoint for the first gas injection interval to establish a first bottom hole pressure (BHP) at the end of the first gas injection interval;   maintaining gas flow into the well at the second gas injection setpoint for the second gas injection interval to establish a second BHP at the end of the second gas injection interval; and   identifying a change between the first BHP and the second BHP, wherein the change corresponds to the first BHPD.   
     
     
         3 . The process of  claim 2 , further comprising:
 maintaining gas flow into the well at the third gas injection setpoint for the third gas injection interval to establish a third BHP at the end of the third gas injection interval; and   identifying a change between the second BHP and the third BHP, wherein the change corresponds to the second BHPD.   
     
     
         4 . The process of  claim 3 , wherein the establishing of each BHP comprises at least one of:
 obtaining a bottom hole pressure measurement from a bottom hole pressure sensor;   obtaining a bottom hole pressure related value from an output of a production flow sensor; and   generating a bottom hole pressure related value from a multiphase correlation calculation.   
     
     
         5 . The process of  claim 3 , wherein establishing each BHP comprises:
 generating an average BHP for each gas injection interval.   
     
     
         6 . The process of  claim 3 , further comprising for each gas injection interval:
 monitoring a current gas flow into the well;   comparing the gas flow to a predetermined minimum gas flow; and   suspending the gas injection interval when the current gas flow into the well is less that the predetermined minimum gas flow.   
     
     
         7 . The process of  claim 6 , further comprising:
 identifying when the current gas flow exceeds the gas injection setpoint for the gas injection interval; and   restarting the gas injection interval.   
     
     
         8 . The process of  claim 1 , wherein adjusting the gas injection setpoint for the subsequent interval based on the comparison, further comprises:
 adjusting the gas injection setpoint for the subsequent interval in the direction of a previous gas injection setpoint adjustment if the second BHPD is greater than the first BHPD   adjusting the gas injection setpoint for the subsequent interval in a direction opposite of the previous gas injection setpoint adjustment if the second BHPD is less than the first BHPD.   
     
     
         9 . The process of  claim 8 , wherein the adjusting of the gas injection setpoint for the subsequent interval comprises one of increasing the gas injection setpoint for the subsequent interval and decreasing the gas injection setpoint for the subsequent interval. 
     
     
         10 . The process of  claim 8 , wherein adjusting the gas injection setpoint for the subsequent interval in a direction opposite of the previous gas injection setpoint adjustment comprises:
 adjusting the gas injection setpoint in the opposite direction with a magnitude that is a fraction of a magnitude of the previous gas injection setpoint adjustment.   
     
     
         11 . The process of  claim 1 , further comprising:
 comparing the second BHPD to a predetermined threshold; and   increasing the gas injection setpoint for the subsequent gas injection interval if the second BHPD is less than the predetermined threshold.   
     
     
         12 . A system for adjusting a gas injection setpoint for a well utilizing gas lift, comprising:
 a flow control valve disposed in a flow path between a gas source and a well;   a flow meter disposed in the flow path between the gas source and the well, the flow meter being configured to measure a rate of gas flow through the flow path and generate a corresponding output;   a controller in communication with the flow control valve and the flow meter, the controller configured to:
 adjust the flow control valve to establish gas injection setpoints for gas injection intervals, respectively; 
 identify a Bottom Hole Pressure (BHP) for each gas injection interval; 
 calculate a current Bottom Hole Pressure Drawdown (BHPD) between an end of a current gas injection interval and an end of a previous gas injection interval; 
 compare the current BHPD to a previous BHPD; 
 calculate an adjusted gas injection setpoint for a subsequent gas injection interval based on the comparison; and 
 generate a valve control signal for receipt by the flow control valve, the flow control valve being configured to adjust a rate of gas flow into a well to the adjusted gas injection setpoint in response to a valve control signal. 
   
     
     
         13 . The system of  claim 12 , further comprising at least one of:
 a bottom hole pressure sensor connected to the controller, wherein the controller identifies the BHP based on an output of the bottom hole pressure sensor; and   a production flow sensor connected to the controller, wherein the controller identifies the BHP based on an output of the production flow sensor.   
     
     
         14 . The system of  claim 12 , wherein the controller is configured to perform a multiphase correlation calculation, wherein the controller identifies the BHP based on an output of the multiphase correlation calculation. 
     
     
         15 . The system of  claim 12 , wherein the controller is configured to:
 identify a change between a BHP for the current gas injection interval and a BHP for an immediately previous gas injection interval, wherein the change is the current BHPD.   
     
     
         16 . The system of  claim 15 , wherein the controller is configured to:
 set the adjusted gas injection setpoint for the subsequent interval in the direction of a previous gas injection setpoint adjustment if the current BHPD is greater than the previous BHPD; and   set the adjusted gas injection setpoint for the subsequent interval in a direction opposite of the previous gas injection setpoint adjustment if the current BHPD is less than the previous BHPD.   
     
     
         17 . The system of  claim 16 , wherein the controller is configured to:
 increasing the previous the gas injection setpoint or decrease the previous gas injection setpoint for the subsequent interval.   
     
     
         18 . The process of  claim 16 , wherein, when setting the adjusted gas injection setpoint in a direction opposite of the previous gas injection setpoint adjustment, the controller is configured to:
 set the adjusted gas injection setpoint in the opposite direction with a magnitude that is a fraction of a magnitude of the previous gas injection setpoint adjustment.   
     
     
         19 . A process for adjusting a gas injection setpoint for a well utilizing gas lift, comprising:
 calculating a current Bottom Hole Pressure Drawdown (BHPD) between an end of a current gas injection interval and an end of a previous gas injection interval;   comparing the current BHPD to a previous BHPD;   calculating an adjusted gas injection setpoint for a subsequent gas injection interval based on the comparison; and   controlling flow control valve disposed in a flow path between a gas source and the well to adjust a rate of gas flow into the well to the adjusted gas injection setpoint.   
     
     
         20 . The process of  claim 19 , further comprising:
 identifying a Bottom Hole Pressure (BHP) for the current gas injection interval;   identifying a change between the current BHP and a previous BHP for a previous gas injection interval, wherein the change represents the BHPD.   
     
     
         21 . The process of  claim 19 , further comprising:
 setting the adjusted gas injection setpoint for the subsequent interval in the direction of a previous gas injection setpoint adjustment if the current BHPD is greater than the previous BHPD; and   setting the adjusted gas injection setpoint for the subsequent interval in a direction opposite of the previous gas injection setpoint adjustment if the current BHPD is less than the previous BHPD.   
     
     
         22 . The process of  claim 21 , further comprising:
 setting the adjusted gas injection setpoint in the opposite direction with a magnitude that is a fraction of a magnitude of the previous gas injection setpoint adjustment.