Use of CO2-Triggered Switchable Surfactants for the Stabilization of Oil-in-Water Emulsions

Pipelining of heavy crudes can be facilitated by preparing oil-in-water (O/W) emulsions of the crude, but separation of the oil from the water after pipelining is problematic if conventional surfactants are used. Long-chain acetamidines are CO 2 -triggered switchable surfactants, being surface-active when CO 2 is present but not when CO 2 is absent. Unfortunately, in the presence of CO 2, they stabilize water-in-oil (W/O) emulsions of heavy crude rather than the desired O/W emulsions. However, in the absence of added CO 2, several compounds (Na 2 CO 3, three of the long-chain acetamidines, and two other amidines) stabilize O/W emulsions. These low-viscosity emulsions can later be broken by the addition of CO 2 . The residual oil content in the recovered water is lowest if the compound used to stabilize the original emulsion was a long-chain acetamidine.