Method for selective extraction of surfactants from crude oil

A method for selective extraction of naphthenic acids from an acidic crude oil, comprising the following steps in order:

• providing an acidic crude oil comprising naphthenic acids and having a total acid number (TAN) greater than 0.4;
• mixing the acidic crude oil with an aqueous solution comprising water and a weak base to create an emulsion;
• separating an excess of the acidic crude oil from the emulsion and removing the excess acidic crude oil from the emulsion to form a separated emulsion, wherein the separated emulsion comprises the water, the naphthenic acids, and a remaining portion of the acidic crude oil;
• adding a salt to the separated emulsion, thereby causing the remaining portion of the acidic crude oil to separate from the separated emulsion;
• removing the separated remaining portion of the acidic crude oil from the separated emulsion;
• and
• extracting a portion of the naphthenic acids from the separated emulsion;
• wherein the pH of the aqueous solution is from 10.5 to 11.5 and wherein the portion of the naphthenic acids extracted have a molecular weight from 200 to 700.