Factors Controlling the Stability of Oil-Water Emulsions: A Case Study of the Shale Oil Emulsion in Changqing Oilfield

Water-in-oil (W/O) emulsions are frequently encountered during the development of shale oil reservoirs, and their stability constitutes a key factor influencing the production of crude oil. In this study, the stability of W/O emulsions associated with shale oil in the Changqing Oilfield was investigated using a combination of bottle test, microscopic observation, and particle size distribution analysis. The results identified and ranked key factors influencing emulsion stability, with asphaltenes, resins, wax crystals, and clay mineral particles identified as primary determinants. Notably, the effectiveness of guar gum breakage during field operations is crucial, as incomplete breakage can significantly enhance the stability of emulsions. Taking into account the experimental factors and the current development status of oilfield production, it is concluded that emulsion stability is influenced by a complex interplay of factors rather than by singular contributions. By integrating insights from existing literature and conducting three-phase contact angle experiments, it is determined that the interfacial membrane at the oil- water interface is a composite structure formed by various components, characterized by low interfacial tension and significant steric hindrance. This composite structure contributes to a homogeneous particle size distribution, leading to macroscopic emulsion stability. Additionally, this study contributes valuable insights into the mechanisms of emulsion stabilization, which have significant implications for enhancing oil recovery techniques.