Effect of Diluents and Asphaltenes on Interfacia! Properties and Steam-Assisted Gravity Drainage Emulsion Stability: Interfacia! Rheology and Wettability

摘要

In steam-assisted gravity drainage (SAGD) operations, the produced fluids are complex water-in-oil-in-water (W/ O/W) emulsions. A diluent is often added to reduce the density and viscosity of the heavy crude oil. However, the quality and composition of the diluents may in some cases increase emulsion stability and cause the dehydration of the oil to be more difficult because there are more surface-active agents added to the oil coming from the diluent streams. Thus, this work was aimed at studying the effect of three different diluents on interfacial film formation of a Canadian heavy oil. Interfacial elasticity and compressibility were evaluated, and the results were then correlated with emulsion stability. The wettability of the systems was also studied. The systems studied behaved as if a bidimensional gel near its gelation point had organized at the interface, in which adsorbed amphophilic materials, such as asphaltenes and resins, self-aggregated at the interface, forming a network that acts as a stabilizing mechanism for produced emulsions. When the interface was aged, its gel strength was much higher man the fresh interface, suggesting an explanation as to why aged emulsions are more difficult to treat. Unlike elasticity and interfacial tension, measurements, it was demonstrated that compressibility measurements can predict emulsion stability under different conditions. The higher the crumpling film ratio and the lower the compressibility, the more stable the emulsion. This test method gives more insights into the mechanisms of emulsion stabilization caused by diluents and asphaltenes and can potentially be employed to study the structure and demulsifying performance relationships of emulsion breakers (EBs) and reverse emulsion breakers (REBs).