This paper presents a new approach for flooding carbonate reservoirs using chelating agent fluid system prepared using seawater without dilution. Sequential coreflooding tests using limestone core samples following seawater flooding with an increasing concentration of the chelating agent EOR fluids revealed significant incremental oil recovery ranging from 16 to 26%OOIP without any significant increase in the pressure drops. The sequential flooding starts with small concentrations of the chelating agent EOR fluid to alter the wettability of the limestone surface to a more water wet condition through gradual surface rock dissolution.

Zeta potential measurements as a function of chelating agent EOR fluid concentrations showed that increasing the concentration of the chelating agent resulted in altering the limestone surface charges to more negative values. Interfacial tension, IFT, was measured as a function of chelating agent the concentrations and found to decrease as the chelating agent concentration increases.

This new approach minimizes the use of large quantities of chelating agent chemicals and consequently reduces the cost.

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