Yield stress behavior for crude oil-polymer emulsions

Since all industrial applications of crude oil-polymer emulsions demand emulsions transportation, it is important to study the flow characteristic in term of apparent yield stress. The yield stress measurements of crude oil-polymer emulsions were carried out using RheoStress RS100 under controlled stress mode. Controlled stress rheometers provide the most direct technique for the measurement of yield stress. The yield stress measurements were carried out for crude oil-Alcoflood polymer emulsion over the range of 0-75% by volume of crude oil concentration and 0-10⁴ ppm of polymer concentration. Three different Alcoflood polymers were employed in this investigation. These are AF1235, AF1275, and AF1285. The yield stress measurements of polymer aqueous solutions and crude oil-polymer emulsions are extensively investigated. Casson Model can be used to predict the apparent yield stress for either Alcoflood polymer aqueous solutions or crude oil-Alcoflood polymer emulsions. The increase of polymer concentration improves the initial flow resistance for the three tested polymer materials. At a polymer concentration beyond 10³ ppm, the apparent yield stress raises strongly with polymer concentration. For polymer concentration below 10³ ppm, the three polymer materials show close values of the apparent yield stress. For polymer concentration higher than 10³ ppm, the polymer material of AF1275 causes higher apparent yield stress than AF1285 and AF1235 in order. Non-linear three dimensional model is provided to predict the apparent yield stress of crude oil-Alcoflood polymer for a wide range of crude oil and Alcoflood polymer concentrations.