Patent ID: 8256282

Claim:
A method for determining a critical desorption pressure comprising: pumping drilling fluid out of an area within a well bore; drawing formation fluid from a formation into the area; detecting a bubble point pressure of the area by, for a plurality of iterations until the bubble point pressure is detected: obtaining the formation fluid in a flowline, measuring, by a liquid detector connected to the flowline, a response time of light passing through the formation fluid in the flowline, detecting the bubble point pressure as a current local pressure in the area when, based on the response time, gas is determined to be present in the flowline, and reducing, by a pressure interval, the current local pressure in the area when, based on the response time, gas is determined not to be present in the flowline, wherein reducing the current local pressure comprises pumping additional drilling fluid out of the area to draw the formation fluid from the formation into the area, wherein, for each iteration of the plurality of iterations, the flowline is located at a requisite depth; and identifying the critical desorption pressure of the formation fluid as equal to the bubble point pressure.