页岩油二氧化碳注气提采环境下固井水泥环完整性保障技术研究

Research on the Integrity Guarantee Technology of Cement Ring Under the Environment of Shale Oil Carbon Dioxide Injection for EOR

为提高二氧化碳(CO_(2))注气提采环境下固井水泥石(环)的腐蚀完整性,文章从超临界CO_(2)腐蚀机理、防腐添加剂及体系三方面进行科研攻关,探讨不同水泥石在超临界CO_(2)环境养护中宏观力学与微观形貌的相关变化。研究结果表明:超临界态CO_(2)显著加速水泥石结构破坏,抗CO_(2)腐蚀固井水泥石可控制其腐蚀30 d的抗压强度衰退率≤8.56%,遇CO_(2)自修复水泥石具有≥90.22%的高效裂缝自修性,同时该水泥环腐蚀60 d后环空窜逸流量≤0.0002 mL/min,该技术在长庆油田陇东页岩油示范区完成推广应用83井次,固井质量优质率≥93.9%,施工至今无气体窜逸现象发生。该研究结果对提高页岩油二氧化碳注气提采环境下的固井水泥环完整性具有一定的实践指导意义。

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 CO_(2)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 CO_(2)environment.The research results show that supercritical CO_(2)significantly accelerates the structural damage of cement stone,and the anti CO_(2)corrosion cementing cement stone can control its compressive strength degradation rate of≤8.56%after 30 days of corrosion.When encountering CO_(2),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≤0.0002 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.