Drive for heavy oil recovery

Claim 1

A method for the recovery of heavy oil from a subterranean silica-containing oil-containing formation penetrated by at least one injection well and at least one spaced-apart production well, both of said injection and production wells being in fluid communication with a substantial portion of said formation, and such wells having a communicating relationship, comprising: (a) injecting into the formation via said injection well a predetermined amount of a hot aqueous solution having a pH of above 11.0 and containing sodium hydroxide and sodium bicarbonate, the concentration of said sodium hydroxide being sufficient to provide a molar ratio of sodium bicarbonate to sodium hydroxide not greater than about 3.3 to 1, said sodium bicarbonate reacting with said silica contained in the formation under conditions in the formation to form water-soluble sodium silicate, water and carbon dioxide and said sodium hydroxide reacting with said silica contained in the formation under conditions in the formation to form water-soluble sodium silicate and water plus the thermal energy necessary to provide the heat of reaction required between the sodium bicarbonate and the silica, said in-situ formed carbon dioxide dissolving in the oil reducing its viscosity and the water-soluble sodium silicate lowering the residual oil saturation of the formation; (b) injecting a driving fluid into the formation via said injection well to displace said mobilized oil through the formation toward said production well; and (c) recovering oil from the formation via said production well.

Claim 2

A method for the recovery of heavy oil from a subterranean silica-containing oil-containing formation penetrated by at least one injection well and at least one spaced-apart production well, both of said injection and production wells being in fluid communication with a substantial portion of said formation, and such wells having a communicating relationship, comprising: (a) injecting into the formation via said injection well a predetermined amount of a hot aqueous solution having a pH of above 11.0 and containing sodium hydroxide and sodium bicarbonate, the concentration of said sodium hydroxide being sufficient to provide a molar ratio of sodium bicarbonate to sodium hydroxide not greater than about 3.3 to 1, said sodium bicarbonate reacting with said silica contained in the formation under conditions in the formation to form water-soluble sodium silicate, water and carbon dioxide and said sodium hydroxide reacting with said silica contained in the formation under conditions in the formation to form water-soluble sodium silicate and water plus the thermal energy necessary to provide the heat of reaction required between the sodium bicarbonate and the silica, said in-situ formed carbon dioxide dissolving in the oil reducing its viscosity and the water-soluble sodium silicate lowering the residual oil saturation of the formation; (b) injecting a driving fluid into the formation via said injection well to displace said mobilized oil through the formation toward said production well; and (c) recovering oil from the formation via said production well.