Downhole Gas Influx Detection

Abstract

A technique enables determination of gas influx in a fluid handling system. A tubing is provided for conducting fluid flow therethrough. Pressure signals are transmitted through the fluid in the tubing. Parameters of the pressure signal, e.g. time and/or attenuation, are measured at a first location and a second location along the tubing. Parameter data is evaluated to determine the occurrence of changes indicative of gas influx into the tubing.

1 . A method of determining gas influx, comprising:
 deploying a tubing in a wellbore;   transmitting a pressure signal downhole through a fluid in the tubing;   measuring a time delay and an attenuation of the pressure signal at a downhole location; and   outputting data, corresponding to the time delay and the attenuation, to a control system for determining the occurrence of gas influx into the tubing.   
   
   
       2 . The method as recited in  claim 1 , wherein deploying comprises deploying a coiled tubing in the wellbore. 
   
   
       3 . The method as recited in  claim 1 , wherein transmitting comprises utilizing a valve to create the pressure signal. 
   
   
       4 . The method as recited in  claim 1 , wherein transmitting comprises transmitting a pulse signal. 
   
   
       5 . The method as recited in  claim 1 , wherein transmitting comprises transmitting a continuous wave signal. 
   
   
       6 . The method as recited in  claim 1 , further comprising utilizing the control system to calculate a gas fraction resulting from gas influx. 
   
   
       7 . The method as recited in  claim 1 , further comprising utilizing the control system to compare the time delay and attenuation of a plurality of sequential pressure signals to determine changes indicative of gas influx. 
   
   
       8 . The method as recited in  claim 1 , further comprising utilizing the control system to compare the time delay and attenuation to a baseline time delay and attenuation to determine the occurrence of gas influx. 
   
   
       9 . A system, comprising:
 a tubing deployed in a wellbore;   a pressure modulation device to transmit a pressure signal downhole through the tubing;   an uphole sensor to detect time and pressure of the pressure signal;   a downhole sensor to detect time and pressure of the pressure signal; and   a control system coupled to the uphole sensor and the downhole sensor to measure a time delay of the pressure signal as it moves from the uphole sensor to the downhole sensor, the control system being able to use the time delay to determine a gas influx in the tubing.   
   
   
       10 . The system as recited in  claim 9 , wherein the tubing comprises coiled tubing. 
   
   
       11 . The system as recited in  claim 9 , wherein the pressure modulation device comprises a valve. 
   
   
       12 . The system as recited in  claim 9 , wherein the pressure modulation device is used to transmit a pulse signal. 
   
   
       13 . The system as recited in  claim 9 , wherein the pressure modulation device is used to transmit a continuous wave signal. 
   
   
       14 . The system as recited in  claim 9 , wherein the control system is operated to determine an attenuation of the pressure signal. 
   
   
       15 . A method, comprising:
 transmitting a pressure signal along a fluid disposed in a tubing; and   determining whether an influx of gas into a liquid has occurred within the tubing by measuring at least one of a speed change and an attenuation of the pressure signal.   
   
   
       16 . The method as recited in  claim 15 , further comprising deploying the tubing in a wellbore. 
   
   
       17 . The method as recited in  claim 16 , further comprising using the tubing for a cleanout procedure. 
   
   
       18 . The method as recited in  claim 16 , wherein determining comprises measuring the pressure and time of the pressure signal at an uphole position and at a downhole position. 
   
   
       19 . The method as recited in  claim 18 , further comprising outputting data obtained at the uphole position and the downhole position to a processor-based control system. 
   
   
       20 . A method, comprising:
 deploying a coiled tubing string downhole for a well operation;   transmitting a pressure signal along an interior of the coiled tubing;   measuring the length of time required for the pressure signal to travel between two locations along the coiled tubing; and   determining whether a gas has mixed with liquid in the coiled tubing based in the pressure signal travel time between the two locations.   
   
   
       21 . The method as recited in  claim 20 , wherein transmitting comprises transmitting a pulse signal. 
   
   
       22 . The method as recited in  claim 20 , wherein transmitting comprises transmitting a continuous wave signal. 
   
   
       23 . The method as recited in  claim 20 , wherein transmitting comprises transmitting the pressure signal from an uphole location to a downhole location. 
   
   
       24 . The method as recited in  claim 20 , wherein measuring further comprises measuring an attenuation of the pressure signal. 
   
   
       25 . The method as recited in  claim 24 , wherein determining comprises processing time and attenuation data on a processor-based control system.