Abstract: A method of selective plugging of undesirable high permeability streaks and channels in oil-bearing reservoirs during high temperature (250.degree. F or higher) injection recovery processes such as steamflooding, underground combustion, flooding of a naturally occurring high-temperature reservoir or the like. Improved sweep efficiency can be effected by injecting a gel-forming solution consisting essentially of sodium or ammonium lignosulfonate and water or brine in the absence of other gelation promoters and then allowing the high temperatures of the underground formation to promote gelation. Optionally, a precooling water injection step can be used prior to placement of the gel-forming solution. This system has the advantage of gel times which are sufficiently long at temperatures in excess of 250.degree. F to permit placement of large volumes characteristic of commercial use. This method is particularly useful in selectively forming firm, strong gels in thief zones for steamflooding recovery operations.

Abstract: A method of selective plugging of undesirable high permeability streaks and channels in oil-bearing reservoirs during high temperature (250.degree. F. or higher) injection recovery processes such as steamflooding, underground combustion, flooding of a naturally occurring high-temperature reservoir or the like. Improved sweep efficiency can be effected by injecting a gel-forming solution consisting essentially of sodium or ammonium lignosulfonate and water or brine in the absence of other gelation promoters and then allowing the high temperatures of the underground formation to promote gelation. Optionally, a precooling water injection step can be used prior to placement of the gel-forming solution. This system has the advantage of gel times which are sufficiently long at temperatures in excess of 250.degree. F. to permit placement of large volumes characteristic of commercial use. This method is particularly useful in selectively forming firm, strong gels in thief zones for steamflooding recovery operations.