Oil recovery method

A method for recovering crude oil from a reservoir including at least one layer of reservoir rock having crude oil and a formation water within the pore space thereof includes injecting into the layer(s) of reservoir rock from an injection well, alternating slugs of an aqueous displacement fluid comprising a concentrated solution of a water-soluble additive in an aqueous solvent and of an aqueous spacer fluid. The number of injected slugs of aqueous displacement fluid, n, is in the range of 15 to 1000 per swept pore volume, PVR, of the layer(s) of reservoir rock. The injected pore volume of each individual slug, PVSlug-i, of aqueous displacement fluid is in the range of 10−12 to 10−2 of the swept pore volume, PVR, of the layer(s) of reservoir rock. The total injected pore volume of the slugs of aqueous displacement fluid is in the range of 10−8 to 10−1 of the swept pore volume, PVR, of the layer(s) of reservoir rock. The injected pore volume of each individual slug of aqueous spacer fluid, PVSpacer-i, is in the range of 0.0001 to 0.1000 of the swept pore volume, PVR, of the layer(s) of reservoir rock. The total injected pore volume of the slugs of aqueous spacer fluid is in the range of 0.9000000 to 0.9999999 of the swept pore volume, PVR, of the layer(s) of reservoir rock. The reservoir rock has a dispersivity, α, in the range of 1 to 30% of the interwell distance between the injection well and production well. The amount of additive delivered to the layer(s) of reservoir rock by the plurality of slugs of aqueous displacement fluid is equal to or greater than a predetermined minimum additive quantity (MAQ).