固体草酸双层微胶囊化制备方法及性能评价

Preparation method and rating of merit of encapsulating solid oxalic acid with double deck

针对氯化铵 /亚硝酸盐化学生热压裂液破胶体系存在的羟丙基瓜尔胶用量大、粘度难提高 (一般为 1 0 0mPa·s)、应用范围窄、压裂成本过大的问题 ,提出采用化学物理方法———油相相分离法将草酸微胶囊化。通过微胶囊制备实验 ,确定乙基纤维素作第一层囊壁 ,芯材比为 1 0∶2 ,石蜡作第二层囊壁 ,芯材比为 5∶2。缓释实验结果表明 ,微胶囊具有较高的产率 ,按上述条件制成的微胶囊具有很好的缓释性能 ,pH值为 8左右的水溶液在 3h以后pH值才下降为 7.5 ,对压裂液粘度不会造成很大的影响 ,很好地解决了氯化铵

A chemophysical method phase separation of oil phase for solid oxalic acid encapsulating was presented to solve the problems of needing much hydroxyl propyl guar gum, viscosity increasing difficultly (commonly only 100 mPa·s to the best), narrow usage range and high fracturing cost existed in the using of ammonium chloride/nitrous salt chemical heat generating fracturing fluid system. In preparation of the product, ethyl cellulose was used to be the first microcapsule wall where the ratio of the core to shell is 10 to 2, and paraffin was used to be the second microcapsule wall where the ratio of the core to shell is 5 to 2. Laboratory tests indicated that the microcapsule made under the above conditions possesses high productivity and efficiency. Its delayed releasing performance that the pH value of water solution reducing from about 8 to 7.5 after 3 h has not effect on the viscosity of fracturing fluid, thus the problem of ammonium chloride/nitrous salt chemical heat generating fracturing fluid will be resolved.