不同温压条件下泥质粉砂岩二氧化碳突破压的试验研究

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。

Experimental studies of CO2 breakthrough pressure of argillaceous siltstone under different pressures and temperatures

The CO2 breakthrough pressure (threshold pressure) is one of key indicators for the caprock sealing ability and safety of CO2 geological storage. Different breakthrough pressures experiments have been carried out for different caprock examples around world, and set up a fundamental database for caprock sealing ability evaluation; however, very few researches has been carried out on CO2 breakthrough pressure experiment under different pressures and temperatures. Based on the characteristics and range of breakthrough pressure equipment, the CO2 breakthrough pressure measurement apparatus is developed. The apparatus integrates several methods, such as, step method, continuous method, pulse decay method, and dynamic method. It covers the ordinary range of breakthrough pressure in cap-rocks. Experimental studies of CO2 breakthrough pressure in water saturated argillaceous siltstone sample from Xujiahe formation are carried out; for the Xujiahe formation is an important target formation and seal formation for CO2 aquifer storage in Sichuan Basin. The CO2 breakthrough pressures of core samples under different temperatures and pressures are studied in the experiment. The experiment results show that the breakthrough pressure increases with temperature increasing and CO2 pressure decreasing within the studied pressure and temperature range. The experiment results have the same tendency as the theoretical results deduced by theoretical method; however, there is a discrepancy between experiment results and theoretical results. The discrepancy might be caused by the variation of contact angle, pore-geometry heterogeneity, and experiment method; and this need further study.