Effects of Acid and Base Types on pH Controlled Reversible Emulsion

By changing external conditions, reversible emulsion can vary between oil-in-water emulsion and water-in-oil emulsion to play a better role that is expected. Studies have been conducted on the preparation and stability of reversible emulsions and the effects of acid and base types on them. The studies demonstrated that, a reversible emulsion with good reversibility can be prepared with selected emulsifiers through a predetermined process, and the emulsion can retain good stability before and after reversion. The types of acid and base, especially the anions of high valence in acids, play an important role in the reversion of reversible emulsion. Hydrochloric acid and acetic acid can reverse the phase of emulsion. Sulfuric acid does not change the phase of emulsion, nor does it demulsify the emulsion. Citric acid demulsifies emulsion. In phase changing of reversible emulsion caused by NaOH, Na₂CO₃, NaHCO₃ and ammonia, a maximal electric conductivity appeared; it appeared just during the process of phase change, not after the completion of phase change. These studies can be applied in the treatment of mud cakes produced by reversible emulsion drilling fluids formulated with reversible emulsions; using acid solution, the mud cakes can be easily disposed of with good results.