Abstract:

CO₂ injection for enhanced oil recovery（EOR） has gone though 4 stages of technical improvements in North Jiangsu Basin. During the current low oil price period, three challenges are exiting: the high cost of CO₂ flooding makes it difficult to realize benefit development, the minimum miscible pressure（MMP） is too high to enhance oil recovery substantially, and the heterogeneity is too strong for expanding CO₂ swept volume. Therefore, three main countermeasures is put forward. Firstly, the optimization of scheme is the key. By full advantage of the old wells to reduce investment for new wells, optimization of injection mode to reduce injection volume, use of current equipment to reduce recycling cost, and overall plan for the pipe network to reduce gas cost, the cost of CO₂ flooding is reduced, thus, the equilibrium oil price of 60 % of the CO₂ flooding project will be kept below ＄60/bbl. Secondly, screening and evaluation of additives to reduce MMP are carried out. Meanwhile, the miscible condition was improved and the recovery rate of CO₂ flooding was increased by the injection in advance to increase the formation pressure. Tiredly, the swept volume of CO₂ is improved by means of injection at the high parts, water alternating gas injection（WAG）, and profile modification to mitigate gas channeling. The research and practice offer reference and examples for the beneficial development of CO₂ flooding in similar reservoirs under low oil price.

Key words: CO₂ flooding, EOR, North Jiangsu Basin, reducing minimum miscible pressure, mitigate gas channeling