Summary

Mixtures of anionic/cationic surfactants have never been used in enhanced oil recovery (EOR) for negatively charged sandstone reservoirs because of high adsorption. Recently, novel mixtures of anionic/cationic surfactants that produced low critical micelle concentrations (CMCs) of 3.50×10–4 wt%, ultralow interfacial tension (IFT) of 10–4 mN/m, high oil solubilization of 23, and low adsorption of 0.27 mg/g sand were developed in the laboratory for a mature sandstone reservoir with characteristics of high temperature of 81°C, high water cut of 97.8%, high recovery factor of 53.3%, and low‐acid oil of 0.021 mg/g potassium hydroxide (KOH). Coreflooding results indicated that alkali/surfactant/polymer (ASP) flooding with a preslug of crosslinked polymer (CP) increased oil recovery by 24.2% of original oil in place (OOIP) over the waterflood under the optimal chemical formulation.

Since January 2012, the first field application of ASP flooding in the world with highly efficient mixtures of anionic/cationic surfactants was performed for a high‐temperature, high‐water‐cut mature sandstone reservoir to demonstrate the potential of the novel surfactant to recover residual oil from as high as 53.3% recovery factor of reserves. ASP slug and CP slug for conformance control were alternately injected. The water cut decreased from 97.9 to 90.2% and the estimated ultimate oil recovery can be increased by 14.2% of OOIP and yield up to 67.5% of OOIP.

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