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EOR Potential of Mixed Alkylbenzenesulfonate Surfactant at Low Salinity and the Effect of Calcium on “Optimal Ionic Strength”

Tichelkamp, Thomas, Hosseinzade Khanamiri, Hamid, Nourani, Meysam, Åge Stensen, Jan, Torsæter, Ole, Øye, Gisle
Energy & Fuels 2016 v.30 no.4 pp. 2919-2924
petroleum, surface tension, ions, salinity, calcium, floods, surfactants, oils, sodium, sodium chloride, ionic strength, prediction
The enhanced oil recovery (EOR) potential of different alkylbenzenesulfonate surfactants was investigated in a combined study of crude oil–water phase behavior and interfacial tension (IFT) and macroscopic oil displacement studies. In the presence of small amounts of calcium ions (calcium/sodium = 4 mol %), ultralow oil–brine IFT (<0.001 mN/m) was observed at ionic strengths 10 times lower than “optimal salinity” with sodium chloride only; this suggested an application in low salinity surfactant (LSS) EOR. “Optimal ionic strength” was determined for different calcium/sodium ratios in the brine, which further allowed prediction of phase behavior and IFT range for a given surfactant and a given crude oil at different brine compositions. In laboratory core floods, crude oil displacement by LSS with an optimal ionic strength electrolyte was around 9% higher than at “non-optimal” conditions.