Abstract:A method of recovering hydrocarbon from anargillaceous subterranean rock formation involvingthe flooding of the formation with an aqueous fluid todisplace the hydrocarbon from the formation. The methodinvolves first subjecting the formation to an acid stimu-lation treatment by injecting a strongly acidic solutionto dissolve acid soluble pore clogging materials, althoughthis first step can be omitted, if desired. The formationis then treated with a solution containing an acid, a sur-factant and a clay stabilizing agent. The concentrationof the treatment solution is initially quite high but isgradually reduced until a certain threshold concentrationis reached, after which a treatment solution having thisthreshold concentration is continuously injected into theformation to displace the hydrocarbon. The ingredientsof the treatment solution exhibit a synergistic effect inmaintaining a desirable rock permeability and a favourablemobility ratio between the treatment solution and thedisplaced hydrocarbons.
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