CO

2

flooding is one of the effective methods for EOR. CO

2

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 materi

al

a new CO

2

flooding pipe string （

Φ

73.02 mm N80-3Cr-BGT1 gas sealing tubing+sliding sleeve switch+Y445J packer+

Φ

73.02 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.