Application of Coiled Tubing Distributed Optical Fiber Temperature Sensing Technology in Well Integrity Diagnosis

Due to the influence of reservoir geological features and cementing quality, wellbore leakage and damage often occur. The traditional packer pressure test has many problems, such as complicated production process, long production period and low accuracy of leakage location, which have seriously affected the fracturing operation schedule. The distributed optical fiber temperature sensing (DTS) system is used to collect the high frequency temperature through the coiled tubing downhole optical fiber. Combined with the casing collar magnetic locator (CCL) and the optical fiber to calibrate the depth, the temperature difference of the whole wellbore was analyzed to determine the location of the leaks. In the test well of Changqing Oilfield, the monitoring depth was 5,122 m, the positioning accuracy of CCL was ±1 ft, and the positioning accuracy of optical fiber was 0.5 m. It was found that there were three suspicious leaks in the monitoring well section by the interpretation soft, which was consistent with the results of the packer pressure test, and the operation period was shortened by 66%. The technology enables rapid and accurate location of multiple leaks in the wellbore, and improve operational efficiency. It has the advantages of long monitoring distance, accurate location, and short operation period, which enriches the well integrity diagnosis and ensure the on-site fracturing operation effectively.