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CO2突破压是CO2地质封存盖层密封性和安全性评价的关键指标之一,盖层CO2突破压试验技术也是评价盖层密封性的关键技术之一。国内外学者已经对不同盖层岩样的CO2突破压开展了较为系统的试验研究,但还未对不同温度和压力条件下的CO2突破压变化规律进行研究。在调研现有CO2突破压试验方法和设备的基础上,研制了集成分步法、连续法、脉冲法和驱替法等多种突破压测量方法的CO2突破压试验装置,具有广泛的适用范围。采用该试验装置对四川盆地内须家河组泥质粉砂岩薄弱盖层开展了突破压试验研究,研究40~70℃和10~30 MPa温压范围内超临界CO2突破压的变化规律。试验拟合结果显示:在所研究的温压范围内,CO2突破压随CO2压力升高而降低;随CO2温度上升而上升。试验结果与基于表面张力的理论结果趋势吻合较好,但存在一定的差异;两者之间的差异可能是受CO2-水接触角变化、砂岩孔隙结构非均质性以及试验方法的影响。
CO2 breakthrough pressure is one of the key indicators for the evaluation of the sealing and safety of CO2 geological seal cover. The CO2 breakthrough pressure test of cover cap is also one of the key technologies to evaluate the seal of cover. Domestic and foreign scholars have carried out systematic tests on the CO2 breakthrough pressure of different caprock samples, but the law of CO2 breakthrough pressure under different temperature and pressure conditions has not been studied. Based on the investigation of the existing CO2 breakthrough pressure test methods and equipment, a CO2 breakthrough pressure test device integrating a variety of breakthrough pressure measurement methods such as step-by-step method, continuous method, pulse method and flood displacement method has been developed and has a wide scope of application . Using this test device, a breakthrough pressure test was carried out on the weak caprocks of the Argillaceous siltstone in the Xujiahe Formation in Sichuan Basin to study the variation of the breakthrough pressure of supercritical CO2 in the temperature range of 40 ~ 70 ℃ and 10 ~ 30 MPa. The experimental results show that the breakthrough pressure of CO 2 decreases with the increase of CO 2 pressure and increases with the increase of CO 2 temperature. The experimental results are in good agreement with the theoretical trend based on surface tension. However, there is a certain difference between them. The difference between the two may be due to the change of CO2-water contact angle, the heterogeneity of pore structure and the test method.