For many years, hydrochloric acid was the main fluid used in carbonate reservoirs well stimulation. Hydrochloric acid has many advantages including high dissolving power and water soluble products, but it also has some disadvantages such as high reaction rate and high corrosivity. There are other acid systems that can be used to minimize these effects; one of the most important systems is the emulsified acid. The emulsified acid offers the advantage of minimum additives and minimum corrosion possibilities. Researchers correlated the droplet size of the dispersed phase (acid) and emulsifier concentration to the viscosity, stability, and reaction kinetics of emulsified acids.
The effect of emulsifier concentration, acid volume fraction and temperature on elastic properties of emulsified acid was not studied before. The main objective of this work is to study the effect of these parameters on the elastic properties of the emulsified acid. In order to perform that, a HPHT oscillatory rheometer was used.
The general behavior of emulsified acid is that the viscous modulus (G″) is always higher than the elastic modulus (G′). As the emulsifier concentration increases, viscosity increases and the viscous behavior dominates for these fluids. As the acid volume fraction increases, the viscous modulus (G″) increases. At low emulsifier concentration (2 vol%), the elastic modulus (G′) and viscous modulus (G″) increase with increasing the temperature up to 170 °F and then decrease. At higher emulsifier concentration, the elastic modulus (G′) almost does not change with temperature and the viscous modulus (G″) always decreases with increasing temperature. These results will help production engineer to better design acid treatments that depend on emulsified acids.