CO2 Flooding WAG Safety Control Technology

Abstract Under the conditions of injecting pure CO2, the corrosion rate of strings in CO2 injection wells is very low, while in WAG process, because CO2 is mixed with water, corrosion rate of downhole strings is high. Hence, we need to take some anticorrosion measures. Because of the fluctuations in pressure and the changes in temperature due to frequent changes of gas injection and water injection, both of these two processes will cause load changes of the tubing, as well as reduce the tubing seal behavior. WAG technology should be optimized. According to affecting factors of corrosion of WAG process in CO2 flooding, studies of corrosion prevention measures of wellhead equipment, downhole strings and casing are carried out. Based on different conditions of string mechanics in the WAG process, considering different working conditions, the CO2 WAG process is optimized to reduce fatigue failure due to the fluctuations of pressure and temperature on the strings. The safety control technology of CO2 WAG is widely used in CO2 flooding test in Daqingzi oilfield. In the CO2 WAG process, the technology optimizes injection strategy and corrosion prevention measures in CO2 WAG injection process, protects wellhead equipment and downhole strings of the CO2 injection effectively, as well as ensures safe and smooth operation of CO2 injecting wells.