A Stratified Gas Injection Technique with Concentric Double Pipe for CO₂ Flooding in Subei Oilfield

Conventional gas injection techniques of CO₂ flooding in Subei Oilfield face uneven suction profiles, serious gas channeling in high permeability layers, and low production degrees in low permeability layers in the techniques’ application. In order to address these issues, we analyzed conventional stratified gas injection techniques and developed a stratified gas injection technique with concentric double pipe for CO₂ flooding. It contains a two-stage anchored pipe string design, anti-corrosion materials and a mass flowmeter selection, with optimization of a gas injection separator and other downhole tools. According to the actual situation of field, the instability of the pipe string and the failure of the packer were solved, and an accurate stratified gas injection was accomplished. The technique has been tested in Well C1 of Caoshe Oilfield, and all indexes met the design requirements of stratified gas injection by adjusting the stratified gas injection volume with ground devices. The good test results showed that the technique has the advantages of convenient operation, high reliability, and high dispensing accuracy. Therefore, it can bring about fine gas injection and provide a new technical method for effective development of CO₂ flooding in Subei Oilfield.