Crude oil foams. Part 1 – A novel methodology for studying non-aqueous foams formed by depressurization

• We have developed a test to study crude oil foams formed by depressurization.
• The defoaming kinetics show sigmoidal shapes.
• Foam stability is related to a coupled effect of the viscosity and the composition.
• Foaminess is function of both the nature of the gas and the composition of the oil.

Crude oil foams are highly complex non-aqueous foams that tend to form from the release of dissolved gas after an abrupt decrease in the pressure. These foams are typically encountered during crude oil exploitation and refining and especially in oil–gas separation processes. These kinds of foams are widely different from aqueous ones in terms of formation and stabilization and therefore classical methods developed for the study of aqueous foams are no longer useful to reproduce crude oil foam formation conditions. For this reason, we have developed a foam test based on crude oil depressurization to simulate crude oil formation during oil production. Foams can be generated through the laboratory test in a reproducible way and can be consequently characterized in terms of foaminess, stability and kinetics of rupture. Moreover, we also have developed a new methodology to characterize foam stability and liquid foaminess by modeling the crude oil defoaming kinetics. The model we propose allows an easy comparison of the behavior of crude oils foams. By studying different crude oils of known compositions, we have found a correlation between their behavior in term of stability and foaminess and a parameter that takes into account the crude viscosity and its composition.