Abstract:

CO₂ flooding is one of the effective methods for EOR. CO₂ flooding test has been started in Subei（northern Jiangsu province） oilfield since 2005. Y221 packer was used to seal pipe column in the early stage, which basically met the requirements of gas injection. But there still existed problems such as the poor gas sealing performance of gas injection pipe string, the backwashing valve could not be opened, or the casing annulus corrosion inhibitor could not be replaced in circulation, which led to serious corrosion of tubing and casing, and it brought difficulties to the later operation. Since 2014, by improving and optimizing the tubing material, a new CO₂ flooding pipe string （Φ73.02 mm N80-3Cr-BGT1 gas sealing tubing+sliding sleeve switch+Y445J packer+Φ73.02 mm N80 thickening tubing+gas admittance valve of multi-function） has been designed based on the development and application of Y445J packer. And field tests have been conducted for 8 wells, all of which can ensure the good condition of casing pressure being zero for a long time. The experiment shows that the pipe string has the advantages of good gas sealing performance, circulating replacement of oil casing annulus corrosion inhibitor, and preventing back flow. The performance meets the design requirements, and is worth popularizing.

Key words: Subei oilfield, CO₂ flooding, Y221 packer, Y445J packer