Studies on properties of interfacial active fractions from crude and their effect on stability of crude emulsions

The influence of indigenous interfacial active fractions from crude on the interfacial property between water and crude and its effect on stability of crude emulsions were studied. It is found that the carboxylic acids in the fractions of asphaltene from Gu Dong(#)1, Gu Dong(#)4 crude, the resin from Da Qing crude, and the fatty acid in the fractions of saturate from Da Qing crude are responsible for decreasing the interfacial tension between the crude oils and water. These acids have relatively smaller molecule mass, more branch chain, and more oxygen, but they are not able to stabilize emulsion formed by model oil and water. It is the acids with relatively larger molecule mass that are responsible for stabilizing the emulsions. For model oil and alkali solution system the salt or soap formed by fast reaction of the acid, ester with relatively smaller molecule mass, and alkali are responsible for decreasing the interfacial tension between crude oil and water. The salt or soap formed by slow reaction of the acid, ester with relatively larger molecule mass, and alkali are responsible for stabilizing crude oil emulsions.