Oil recovery process using dilute acid

Claim 1

A method for recovering hydrocarbons from a subterranean hydrocarbon-bearing calcareous formation penetrated by an injection well and a production well in a throughput operation which comprises, injecting into said formation through said injection well a slug of dilute aqueous solution of hydrochloric acid having a concentration of hydrogen chloride in the range of from about 0.05 to about 5 percent by weight in an amount within the range of from about one-fourth to about 1 1/2 pore volumes of said formation sufficient to react with the calcareous constituents of said formation thereby substantially increasing the permeability and porosity of said subterranean formation and generating carbon dioxide within said formation, thereafter injecting water into said formation through said injection well and driving said dilute aqueous solution of hydrochloric acid and said carbon dioxide toward said production well and displacing formation hydrocarbons through said formation toward said production well, by continuing injecting slugs of said dilute aqueous solution of hydrochloric acid and water in alternate stepwise fashion, while withdrawing said formation hydrocarbons through said production well.