We report the results of laboratory experiments designed to test the efficacy of polyethylene glycols, PEGs, in reducing the adsorption of optimized propoxy-lated/ethoxylated alkyl sulfates, PO/EO surfactants, onto clay. We also report the results of experiments designed to determine if the PEG additives can improve the cost-effectiveness of PO/EO surfactant/polymer flooding. A PO/EO surfactant blend was designed for a reservoir with a high salinity connate brine, 190 000 mg/L total dissolved solids, a moderate temperature, 117°F, and a light crude oil, 33°API.

The addition of PEG-1000 to the PO/EO surfactant microemulsion reduced the static adsorption of the surfactant on kaolinite to undetectably low levels. In dynamic adsorption experiments, the addition of PEG-1000 to the surfactant microemulsion reduced adsorption on Berea sandstone by a factor of four. Oil recoveries in Berea cores were substantially improved when PEG-1000 was added to the PO/EO surfactant microemulsion. Most importantly, high recoveries were achieved using small pore volumes of microemulsion. Based on oil recovery results and estimates of chemical prices, the microemulsion chemical cost per barrel of tertiary oil is lowered by as much as a factor of four when PEG-1000 is added to a PO/EO surfactant microemulsion.

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