高岭石与CO2溶液反应实验研究

Experimental study on the reaction of kaolinite with CO2(aq)

关键词:  高岭石  CO₂驱  衍射分析  元素分析  离子含量

Key words:  kaolinite  CO₂ flooding  diffraction analysis  element analysis  ion concentration

摘要:

目的 高岭石是沉积岩重要的黏土矿物,为明确高岭石在CO₂水溶液中化学行为与变化历程,探究CO₂与高岭石反应规律。方法 在10 MPa、60 ℃下,利用XRD、XRF、ICP、SEM等手段系统评价了高岭石与CO₂在不同反应阶段的状态,重点对比了高岭石粉末反应前后固相元素、晶体结构及反应液中离子含量变化,结合高岭石结构特征,明确高岭石在酸中的变化规律。结果 液相中新增加了Al³⁺、Si⁴⁺,Mg²⁺含量先上升后趋于平稳,固相粉末中Si/Al(质量比)变化较小,衍射曲线峰形稳定,高岭石集合体未见明显溶蚀,单体边缘有轻微溶蚀。结论 高岭石与CO₂反应后总体变化较小,在CO₂溶液中相对稳定存在。实验结果为注CO₂对储层特征的影响以及气/水交替驱的可行性研究提供重要参数和依据。 

Abstract:

Objective Kaolinite is an important clay mineral in sedimentary rocks. The research purpose of this paper is to clarify the chemical behavior and change process of kaolinite in CO₂ aqueous solution and explore the reaction law of CO₂ with kaolinite. Methods The reaction state of kaolinite with CO₂ at different reaction stages under the station of 10 MPa and 60 ℃ was systematically evaluated by means of XRD, XRF, ICP and SEM. The changes of solid elements, crystal structure and ion concentration in reaction solution before and after kaolinite powder reaction were compared. Then combined with the structural characteristics of kaolinite, the change law of kaolinite in acid was clarified. Results The results showed that the concentrations of Al³⁺ and Si⁴⁺ increased in the liquid phase, Mg²⁺ concentration increases first and then tends to be stable. The change of Si/Al (mass ratio) in solid powder is small, and the peak shape of diffraction curve is stable. There is no obvious dissolution of kaolinite aggregate, and there is slight dissolution at the edge of monomer. Conclusion sThe change of kaolinite after reacting with CO₂ is small and relatively stable in CO₂ solution on the whole. The experimental results provide important parameters and basis for the impact of CO₂ injection on reservoir characteristics and the feasibility study of gas/water alternative flooding.