Characteristic Curvature Evaluation of Anionic Surfactants for Enhanced Oil Recovery Applications

Antonio Benedicto Mejia Jr.

Abstract


Application of microemulsions in hydrocarbon production has re-gained its appeal with recent market interest in chemical enhanced oil recovery (cEOR). A core principal of this microemulsion application is to significantly decrease the interfacial tension between resident crude oil and connate water, resulting in the drastic improvement of hydrocarbon flow within a reservoir. A method to determine the characteristic curvature (Cc) value for anionic surfactants using hydrophilic-lipophilic difference (HLD) concepts and known Cc values as designing tools in formulating surfactant candidates for cEOR in mature oilfields is investigated. Cc values for a set of alkyl alkoxy sulfate (AAS) and alkyl alkoxy carboxylate (AAC) surfactants were determined by thorough analysis of various microemulsion systems containing equal volumes of toluene and aqueous solution.  Variable parameters included a ratio of a reference surfactant (in this case, sodium dihexyl sulfosuccinate or SDHS) to a tested AAS or AAC surfactant and system salinity. At each studied surfactant ratio, an optimal salinity at which the surfactant system exhibits an equivalent solubilization potential for the aqueous and organic phase was visually observed. Based on a deviation of the optimal salinity of surfactant mixtures from the reference surfactant, the Cc values of tested surfactant were calculated and identified as hydrophobic. A preparation methodology, Winsor-type microemulsion classification, results for Cc evaluation, and potential HLD application in cEOR will be discussed.


Keywords


EOR, Surfactants, Characteristic Curvature

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