Determination of the Active Soap Number of Crude Oil and Soap Partitioning Behavior
The optimal salinity of the alkali/surfactant/crude oil system in an alkali/surfactant/polymer (ASP) flooding process was found previously to be a function of the soap/surfactant ratio. Therefore, the soap number is of great importance in formulation design and simulation of ASP flooding processes for enhanced oil recovery. However, there is as yet no established way to quantitatively determine the amount of soap in crude oil relevant to an ASP process. Soaps are the salts of fatty acids, a definition generalized here to include the salts of naphthenic acids. In this paper, we present a method to determine the amount of "active soap" which consists only of soap that partitions into the aqueous phase at low ionic strength and transfers into the oleic phase at high ionic strength. Two fast and accurate methods, aqueous phase potentiometric titration and two phase colorimetric titration, were used to determine the water soluble active soap number (WSASN) a measure of the active soap. Both methods were prov.