三元复合驱钙镁硅钡成垢特征研究

Scaling Formation Characteristics of Ca^(2+)/Mg^(2+)/Si^(4+)/Ba^(2+) in ASP Flooding

由于三元复合驱中的碱对储层矿物的溶蚀作用,使得岩石矿物以可溶物形态进入到储层流体,造成了严重的结垢、堵塞问题。在50℃动态环境,模拟油井采出液离子组成,进行硅钙镁钡成垢实验。研究结果表明,三元复合驱垢主要为碳酸盐、硅酸盐混合垢。随着油井采出液pH值增加,垢样中硅酸盐含量增加,碳酸盐含量降低。在pH值小于10.7时,溶液中硅酸盐沉积速度较快;pH值大于10.7时,硅酸盐沉积速度较缓慢。模拟体系中碳酸根离子含量较低(80 mg/L)时,产生片状硅酸盐沉淀;碳酸根含量较高(1100 mg/L)时,产生颗粒状碳酸盐沉淀。硅离子促进钙盐垢的沉积,在硅含量500 mg/L时,沉垢量最多,达247 mg/L。阳离子增多促进垢的生成,但在钙、钡离子未达到沉积平衡前,镁离子不发生沉积反应。

The erosion and dissolution of reservoir rock minerals by the alkali of ASP flooding made the sandstone passing into the reservoir fluid in soluble state, which caused severe scaling and blocking. Simulated the formation fluid, an experiment of Si2＋ ／Ca2＋ ／Mg2＋ ／Ba2＋ scaling was performed under 50℃. The results showed that the ASP-flooding-scale was mainly composed of carbonate and silicate. With increasing pH value of oil well producded liquid, the content of silicate in the scaling increased, while that of carbonate decreased. When the pH value was less than 10.7, the sedimentation velocity of silicates was higher, otherwise, it became lower. The different content of carbonate and silicate made the scaling state diverse. Flake silicate precipitation formed under low concentration of carbonate ion （80 mg/L）, and granular carbonate precipitation formed under high concentration of carbonate ion （ 1100 mg/L）. Silicon ion promoted the deposition of calcium. The maximum value of scale deposition （247 mg/L） was produced with silicon content 500 mg/L. The cation promoted the deposition of scaling, but Mg2 ＋ wouldn＇t take a precipitation reaction until Ca2 ＋ and Ba2 ＋ reached their chemical equilibrium.