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 CO2-triggered switchable surfactants, being surface-active when CO2 is present but not when CO2 is absent. Unfortunately, in the presence of CO2, they stabilize water-in-oil (W/O) emulsions of heavy crude rather than the desired O/W emulsions. However, in the absence of added CO2, several compounds (Na2CO3, 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 CO2. The residual oil content in the recovered water is lowest if the compound used to stabilize the original emulsion was a long-chain acetamidine.