Yousef Kazemzadeh

Different ions present in formation water (FW) and aqueous phases injected into the oil reservoirs can affect the formation and stability of water-in-oil (W/O) emulsions. Previous studies regarding this issue devoted attention to the chemical compounds of the oil and water with a partial focus on different parameters at ambient pressure and temperature. However, pressure can multilaterally control the formation of emulsification phenomena. One important factor of emulsion stability is the asphaltene that is present in the crude oil. These particles are subjected to instability when they encounter a change in chemical composition and pressure, which affects the formation and stability of the emulsion. In this study, emulsification at various pressures and salinity were analyzed to determine the role of affecting factors, including asphaltene and various ions in the aqueous phase. The apparatus used for monitoring the emulsification was a HP-HT Emulsion Analyzer, designed and constructed by our research group. According to the results, the type and concentration of cations present in the aqueous phase govern the stability of the emulsion. At low salinities (i.e. up to 10,000 ppm), the emulsion stability increases and then decreases with increasing salt concentration in the water phase. At high pressures (i.e. from 4000 to 6000 psi), divalent cations form a more stable emulsion in comparison with monovalent ones. In addition, among divalent cations, Mg2+ introduces a more stable emulsion than that of Ca2+. Based on the results, the thermodynamic conditions affect the precipitation and deposition of asphaltene. Since dead oil was used in this research, the emulsion stability decreases with a decreasing asphaltene content at the interface at high pressures (i.e. 4000–6000 psi). This is due to the considerable reduction in the number of emulsifiers at the interface. Therefore, at high pressures, pressure increase reduces the emulsion stability. However, at low pressures (