Understanding Demulsifier Performance Beyond RSN

Demulsifiers are used in oil production to break long lasting emulsions that are stabilized by compounds occurring naturally in the crude. Demulsifiers are characterized based on their primary functions: dropper, treater, dryer, desalter, and hybrid etc. In this work standard bottle testing has been conducted on demulsifiers with different chemistries in both light and heavy crudes. Crude oil emulsions are directly used when BS&W is more than 20%, while for BS&W less than 20%, synthetic emulsions are made by mixing the crude with NaCl brine in 1:1 ratio by volume. Water-drop at elevated temperature (60-70 ^oC) in a period of 60 minutes and Thief Grind out results are recorded.

Although Relative Solubility Number (RSN) has been traditionally used to select demulsifiers for different applications, it has been found that Alkoxylated Phenolic Resins with similar RSN values can work very differently. Similarly, Di-Epoxide demulsifiers with low RSN (< 8) that are normally classified as dryer, can work well as droppers in light crudes. Demulsifiers based on EO/PO copolymers can be good treaters and improve water quality compared to Alkoxylated Phenolic Resins. Combining demulsifiers with different functions/chemistries can greatly optimize the performance in bottle tests to give faster and more water separation, especially in the heavy crude.

 
In a summary, though RSN and chemistry can provide a basic formulation guide, each demulsifier must be tested to determine how it will behave with different crude oils.  Then an optimized formulation that incorporates multi-functionality can be designed.