NIE Fajian^1,2, MAO Hongchao¹, WANG Qing³, DING Yan^1,2

1. School of Petroleum Engineering, Yangtze University, Wuhan 430100, Hubei Province, China;

2. Research Institute of Exploration and Development, Zhongyuan Oilfield Company, SINOPEC, Zhengzhou 450046, Henan Province, China;

3. Office of Management Committee of National University Science Park of China University of Petroleum, Dongying 257000, Shandong Province, China

Abstract: The CO₂ flooding technologies formed from research and practices in Zhongyuan Oilfield are systematically summarized in recent ten years, including CO₂ flooding mechanism, suitability screening and evaluation technology, reservoir project optimization technology, and assorted injection/production engineering technology. The implementation results in test areas such as the Lower Es₁ reservoir of Pucheng Oilfield and Block Hu96 are evaluated and analyzed, and the CO₂flooding experience for different types of reservoirs is summarized. Research results show that the CO₂ can drive the residual oil after water flooding because it is dissolved in oil spot and oil film for ultra-high water cut reservoirs. The CO₂ can displace the crude oil in the pore throat of above 0.01 μm because of the low interfacial tension between CO₂ and crude oil and the low capillary resistance for the deep reservoir with low permeability. The field practice has proved that the relatively mature CO₂flooding technologies have been developed in the corrosion protection, profile monitoring, layered injection and mobility control. Application of the CO₂ flooding in the deep reservoirs with low permeability has obtained good results, which are in the ultra-high water cut stage. Since the CO₂flooding performance is not affected by temperature or salinity, it has great potential in the high temperature and high salinity reservoirs, which also provides references for the gas injection technology and practice in other types of reservoirs.