Experimental Study on Water-in-Oil Emulsion Stability Induced by Asphaltene Colloids in Heavy Oil

Emulsion stability in water-oil systems is critical for numerous industrial applications, particularly in oil recovery and transportation. However, predicting and controlling the stability of these emulsions under varying conditions remains a challenge. In this study, we investigated the formation and stability of water-oil emulsions under both atmospheric and high-pressure, high-temperature (HPHT) conditions, with a focus on the role of asphaltenes and interfacial tension (IFT). Emulsion stability tests revealed that emulsions exhibit consistent long-term stability at atmospheric conditions, irrespective of the oil-water ratio. Under HPHT conditions, stability varied significantly, with the 75:25 oil-water ratio exhibiting temporary stability, while 50:50 and 25:75 ratios consistently produced unstable emulsions. IFT measurements showed that at atmospheric conditions, crude oil-formation water had an IFT of 21.8 dyn/cm, while crude oil-distilled water had an IFT of 19.8 dyn/cm. Under HPHT conditions (225 °F, 4500 psi), the IFT of live oil-formation water was 18.8 dyn/cm, while live oil-distilled water was 8.0 dyn/cm. At atmospheric conditions, the average IFT was 20.8 dyn/cm, while under HPHT conditions (225 °F, 4500 psi), the average IFT decreased to 13.4 dyn/cm, indicating significant thermodynamic effects on interfacial behavior. Formation water was found to reduce asphaltene precipitation and enhance emulsion stability, emphasizing its role in mitigating asphaltene-related challenges. These findings highlight the importance of tailoring EOR strategies to specific reservoir conditions, including pressure, temperature, oil composition, and water content/chemistry, to optimize emulsion stability, oil displacement, and recovery rates. Future research should explore extended-duration emulsion stability and diverse environmental conditions to better understand their long-term behavior in petroleum applications.