This work shows a unique method for determining the composition of an aqueous solution for chemical EOR using surfactants, salts, and polymer without the addition of a co-solvent. Phase behavior studies composed of reservoir brine, alkali, surfactants, salts, polymer and reservoir crude oil are evaluated as a function of time for onset of phase equilibrium and middle phase formation at ambient temperature and pressure. The optimal surfactant formulation was confirmed by a fast coalescence rate of formation of middle-phase microemulsion and ultra-low interfacial tension. Optimum formulations from phase behavior studies are further evaluated in 1-D sand-pack using crushed sandstone, reservoir oil, and brine at reservoir temperature. One half of a pore volume (PV) of the selected surfactant/polymer (SP) or alkali/surfactant/polymer (ASP) solution is used to flood the column and is followed with reservoir brine until no more oil is produced. The optimum SP and ASP compositions for oil mobilization from the sand pack studies are then investigated in a core flood apparatus. Residual oil saturation was first established in a Berea core at the targeted reservoir temperature and pressure. The core is then flooded with 0.5 PV of the optimum SP or ASP formulation, followed by reservoir brine until no more oil is produced. A unique aspect of this work is that the packed column studies predict core flood results. Packed bed studies are much faster, the apparatus is much less complex and much less expensive, relative to a core flood apparatus. The level of surfactant loading is 0.51% to 0.55% with 2.1% salt. The alcohol-free surfactant loading is lower that previously reported levels. Core floods show oil recoveries ranging from 55% to 64% of the residual oil after waterflooding.

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