Gelled compositions and well treating

A process for displacing oil within a subterranean formation penetrated by at least one well which comprises:

• injecting into the formation a gel forming composition comprising
• (a) water,
• (b) a water-thickening amount of a water-dispersible polymer selected from the group consisting of cellulose ethers, polyacrylamides and biopolysaccharides or heteropolysaccharides produced by the action of bacteria of the genus Xanthomonas upon carbohydrates,
• (c) a small, but effective amount in the range of 0.02 to 2 weight percent of at least one aldehyde component selected from the group consisting of aliphatic monoaldehydes having from 1 to about 10 carbon atoms per molecule, glyoxal, glutaraldehyde, and terephthaldehyde, and
• (d) a small, but effective amount in the range of 0.005 to 2 weight percent of at least one phenolic compound selected from the group consisting of phenol, catechol, resorcinol, phloroglucinol, pyrogallol, 4,4'-diphenol, 1,3-dihydroxynaphthalene, 1,4-benzoquinone, hydroquinone, quinhydrone, and quebracho which amounts of aldehyde (c) and phenolic compound (d) are sufficient to cause gelation of an aqueous dispersion of polymer (b) and form said gelled composition,
• at a pressure or rate insufficient to create cracks or fractures in the formation but sufficient to force said composition into the more permeable portions of the formation to reduce the permeability of same and
• introducing into the formation a drive fluid at a pressure and rate sufficient to force oil from the less permeable oil-rich zones to the surface, thereby increasing oil production and/or reducing the water/oil ratio of the production well.