pH值对砂岩中CO2示踪矿物的稳定性影响实验研究

Influence of pH value on the stability of CO_2 tracer mineral in sandstone

研究片钠铝石形成后保持稳定的pH值临界条件,对含片钠铝石砂岩展开了不同pH值条件下水-岩反应实验。结果表明:在封闭反应体系条件下,相同pH值(pH值为4)、不同体积(10、80、500 m L)条件下,随着反应溶液体积的增大,片钠铝石溶蚀程度增强,片钠铝石稳定性降低;相同体积(500 m L)、不同pH值(4<pH<9)条件下,pH值的增大对片钠铝石溶解速率影响不显著;pH值不是片钠铝石溶解程度发生改变的主控因素,在研究天然片钠铝石稳定性时,可以排除pH值造成的影响。

CO2 geological storage is a feasible way of limiting the excessive CO2 emission into atmosphere. Dawsonite is an effective ＂tracer mineral＂ of CO2 migration, accumulation or escape, which is also a dominant ＂traps minerals＂ for CO2 geological storage. The water-rock reaction experiment on dawsonite sandstone at different pH values was carried out to explore the pH value critical conditions for dawsonite stability after its formation. In the closed reaction system, under the condition of constant pH value （pH = 4） and different volumes （10, 80,500 mL）, it is found that the degree of dawsonite dissolution increases and the dawsonite stability decreases with the increasing volume of reaction solution. Meanwhile, at the constant volume （ V=500 mL） with different pH values （4〈pH〈9）, it is found that pH value in this range does not present significant effect on the dissolution rate of dawsonite. It is concluded that the pH value （4〈pH〈9） is not the main factor of changing the dawsonite dissolution degree. Thus, the influence of pH value is negligible when studying the stability of natural dawsonite.