Oil recovery is increased by about 15% by CO2 flooding in Daqing Oilfield. However, problems such as corrosion,gas channeling, and freezing blocking occur frequently in the process of production. Since ordinary carbon steel is generally adopted for well completion, CO2 corrosion affects the well life and the overall development of the test area. CO2 flooding low-cost chemical corrosion prevention technology is formed, and the corrosion rate is only 0.065mm/a under the CO2 partial pressure of 5MPa and the temperature of 80℃. Due to the low gas viscosity and the heterogeneity of the oil layer, viscous fingering and channeling are easy to occur. Therefore, acid-resistant and oil-resistant CO2 foam channeling sealing agent was developed. Under the condition of pH=3 and oil saturation of 60%, the foaming volume was 430mL and the half-life was 83h. In the process of delaying gas channeling by water alternating gas injection, CO2 hydrate is easy to be generated, which leads to freezing and blocking of wellbore and surface pipelines, resulting in low production rate. Therefore, a low-temperature and efficient plugging removal technology was developed, which realizes 100% dissolution of freezing and blocking at -20℃ for the first time. The improvement of a series of low cost oilfield chemical technologies of CO2 flooding has improved the well running rate, reduces the operation cost, and provides technical support for the sustainable and effective development of CO2 flooding.
Keywords carbon dioxide flooding, corrosion inhibitor, channeling sealing agent, freezing blocking removal agent