弱碱三元复合驱钙镁硅混合成垢的微观考察

Microcosmic Investigation on the Scale Formation of Calcium Magnesium and Silicon in the Weak Alkalescent Alkaline / Surfactant / Polymer Flooding

笔者通过对大庆采油五厂返排液水质分析,配置实验模拟液,对弱碱三元复合驱钙镁硅混合垢生长的微观过程进行了研究,并总结钙镁硅混合垢微观成垢机理。实验表明,碳酸盐与硅酸自聚成垢之间是相互影响的,单独钙镁体系或者硅酸成垢率低,成垢速率缓慢;低浓度比体系中硅酸对钙离子成垢有加速作用,1 h混合体系钙离子成垢率为87%,高浓度比体系中硅酸对钙离子成垢有一定的减速作用,10 h时钙离子成垢率为50%,但二者均未影响钙离子的最终成垢率,24 h后钙成垢率均为98%;混合体系中镁离子成垢显著增加,低浓度比体系中影响尤为明显,1 h后低浓度比体系中镁离子成垢率已达94%;钙镁离子对硅酸聚合有明显的促进作用,低浓度比体系72 h后硅酸成垢率为95%,而但纯硅酸体系72 h的成垢率仅为5%,高浓度比体系,钙镁离子对硅酸最终成垢率无太大影响,但对其聚合速率影响颇大。偏光显微镜观察,纯碳酸盐溶液中,混合垢以立方体型碳酸钙和棒状三水合碳酸镁组成,碳酸钙吸附在棒状三水合碳酸镁晶须两端;加入硅酸后,生成球状三水合碳酸镁,絮状硅酸吸附在碳酸盐晶体上。利用电子扫描显微镜观察得到,钙镁硅混合垢微观形态为"核壳包被"结构,即以碳酸盐为晶核,多聚硅酸为壳的球形混合垢。

After analyzing the water quality of flowback liquid from Daqing＇ s No. 5 oil production company, the author confects the experimental modelling liquid, researches on the micro process of the scale formation of calcium magnesium and silicon in the weak base ternary compound oil displacement wells, and finally summarizes the micro mechanism about how the calcium magnesium and silicon mix into scale. Experiments show that during the separate process of scale formation, the carbonate and silicate are interacted with each other. In addition, the scale formation rate of separate calcium magnesium or silicic acid is low, and the speed of it is rather slow. In the low concentration system, silicic acid has increased effects on calcium ion, and the scale formation rate of calcium ion in mixed system for 1 h is 87%. In the high concentration system, silicic acid has decreased effects on calcium ion, and the scale formation rate of calcium ion in mixed system for 10 h is 50%. But the above two conditions both have no impacts on the final scale formation rate of calcium ions, the scale formation rateof calcium ion after 24 h is 98%. In the mixed system, the scale formation of magnesium ions increased significantly, especially in the low concentration system, and the scale formation rate of magnesium ions in the low concentration system is 94% after 1 h. Calcium and magnesium ions have obvious effects on the polymerization reaction of silicic acid, and the scale formation rate of silicic acid in the low concentration system is 95 % after 72 h. While in the pure silicate system, the scale formation rate for 72 h is only 5%, and in the high concentration system, calcium and magnesium ions have no influence on the ultimate scale formation rate of silicate. However, it has quite big influence on the polymerization rate. Using the micropolariscope, we can see in the pure carbonate solution, the mixing scale is made up of the cubic calcium carbonate and baculine magnesium hydroxide, and the calcium carbonate is adsorbed on both ends of cat whisker from the rod-shaped magnesium hydroxide. After adding silicic acid, it generates ballshaped trihydrate magnesium carbonate, and the flocculent silicic acid is absorbed on the carbonate crystals. By scanning electron microscopy, we can also observe that the microstate of calcium magnesium and silicon mixed scale is core-and-shell package, namely the ballshaped mixed scale treats carbonate as the crystal nucleus and polymer silicic acid as shell.