In view of the common problems of CCUS injection wells, such as casing pressure, difficulty in maintenance and high cost, in order to improve the wellbore integrity of injection wells and reduce comprehensive costs, the research and test of coiled tubing gas injection completion technology were carried out. By optimizing the stainless steel coiled tubing for well completion, the string can resist the corrosion of downhole long-term acidic environment, the leakage point is minimized, and the whole well completion under pressure can be conducted. A special gastight packer has been developed, which adopts a double rubber cylinder sealing structure. The gastight pressure bearing is 50MPa, and the unsealing tonnage is controlled below 8.0t, providing a means to solve the tripping problem caused by the low tensile strength of coiled tubing. Large diameter coiled tubing hanger, metal auxiliary sealing device, dual function safety release and gas seal connector are designed to meet the comprehensive requirements of the overall sealing performance of the gas injection string and the later operation under pressure. On this basis, a new process test was carried out for the first well of coiled tubing gas injection in Changqing Oilfield. It only takes 2.5 hours to lower the tubing string to the design depth. The testing of the large diameter coiled tubing hanger and metal auxiliary sealing device at the wellhead was normal, and the setting and verification of the gas seal packer were successful once. The success of this test provides a new solution for the completion of CCUS injection wells, which is of great significance in improving the integrity of injection wells, realizing safe gas injection throughout the life cycle of injection wells, and building Changqing Oilfield into the largest CCUS industrial base in China. It has a very broad application prospect.
Keywords Coiled tubing gas injection, wellbore integrity, gas injection string, gas seal packer, large diameter coiled tubing hanger