WATER AND OIL SATURATED RESERVOIR WATERFLOOD DEVELOPMENT METHOD Russian patent published in 2009 - IPC E21B43/27 

FIELD: oil and gas industry.

SUBSTANCE: invention is applicable to the oil and gas producing industry and is aimed at enhancing oil recovery of water and oil saturated reservoirs and reducing water cut of oil produced. The method that consists in successively injecting plugs of multivalent cation salt solutions and polymer and withdrawing oil through production wells uses calcium chloride or magnesium chloride brine as multivalent cation salts and all-weather water agent, "ПВВ", as polymer. Also fresh water fringe is injected before and after injecting polymer. All solutions are supplied successively and cyclically shortening supply time for fresh water fringe supply in each successive cycle. The last cycle is followed by a plug composed of a mixture of hydrochloric acid and acetic acid solutions, "ПАП-КЗД".

EFFECT: increased crude oil production and decreased water production due to an optimised reservoir waterflooding process, and restricted water influx into heavily flooded production wells as a result of uniform sedimentation throughout the flooded section.

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