Research on the Integrity Guarantee Technology of Cement Ring Under the Environment of Shale Oil Carbon Dioxide Injection for EOR
In order to improve the corrosion integrity of cementing stone(ring)in the environment of carbon dioxide injection and extraction,this paper conducts scientific research from three aspects:supercritical CO2 corrosion mechanism,anti-corrosion additives and systems,and explores the relevant changes in macroscopic mechanics and microscopic morphology of different cement stones during maintenance in supercritical CO2 environment.The research results show that supercritical CO2 significantly accelerates the structural damage of cement stone,and the anti CO2 corrosion cementing cement stone can control its compressive strength degradation rate of≤8.56%after 30 days of corrosion.When encountering CO2,the self-healing cement stone has an efficient crack self-healing ability of≥90.22%.At the same time,the annular leakage flow rate of the cement ring after 60 days of corrosion is≤0.000 2 mL/min.This technology has been promoted and applied in 83 wells in Longdong shale oil demonstration area of Changqing Oilfield,with a high-quality cementing rate of≥93.9%.There has been no gas leakage phenomenon during construction so far.The research results have certain practical guidance significance for improving the integrity of cementing cement sheath in shale oil carbon dioxide injection and extraction environment.