Abstract: Visible gels are formed by mixing an inorganic crosslinking agent with a low viscosity aqueous solution having a low polyacrylamide content. The visible gels are employed to reduce the water/hydrocarbon permeability ratio of subterranean formations.

Abstract: Polymers (and especially hydroxyethylcellulose) are crosslinked using a lanthanide as a crosslinking agent. The crosslinked polymers have utility in well completion, well stimulation, enhanced oil recovery, and subterranean fluid containment operations.

Abstract: A composition for selectively reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability, such permeability reduction extending continuously from nearby the well as far into the reservoir as is desired. Said composition comprises an aqueous solution or solutions of a water-soluble polymer, a material capable under certain conditions of at least partially cross-linking the polymer to form a gelatinuous precipitate, a water-soluble alkaline material in an amount sufficient to maintain the pH of the polymer-containing composition above the pH at which cross-linking occurs until the composition has passed a desired distance through the reservoir, and a temperature-activated water-soluble acidic material dissolved in the aqueous solution in an amount sufficient to lower the pH of the overall solution to the pH at which cross-linking occurs when said solution is subjected to an elevated temperature.

Abstract: The permeability of higher permeability zones of a subterranean reservoir of heterogeneous permeability is reduced by injecting (1) an aqueous solution of a crosslinkable water-soluble polymer, a material capable under certain conditions of at least partially crosslinking the polymer to form a gelatinous precipitate, a water-soluble alkaline material in an amount sufficient to maintain the pH of the aqueous solution above the pH at which crosslinking occurs until the composition has passed a desired distance through the reservoir, and a water-soluble surface active agent; and (2) a gas mixture comprising an acid gas. A gelatinous foam forms in situ useful for blocking escape of fluids, both gaseous and liquid, into the higher permeability zones of the reservoir during enhanced recovery, typically by carbon dioxide flooding.

Abstract: A method for selectively reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability, such permeability reduction extending continuously from nearby the well as far into the reservoir as is desired. There is injected into the reservoir an aqueous solution or solutions of a water-soluble polymer, a material capable under certain conditions of at least partially cross-linking the polymer to form a gelatinous precipitate, a water-soluble alkaline material in an amount sufficient to maintain the pH of the polymer-containing composition above the pH at which cross-linking occurs until the composition has passed a desired distance through the reservoir, and a temperature-activated water-soluble acidic material dissolved in the aqueous solution in an amount sufficient to lower the pH of the overall solution to the pH at which cross-linking occurs when said solution is subjected to an elevated temperature.

Abstract: A method for selectively reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability, such permeability reduction occurring a substantial distance away from a well in which there is injected into the reservoir an aqueous solution or solutions of a water-soluble polymer, a material capable under certain conditions of at least partially cross-linking the polymer to form a gelatinous precipitate, and a water-soluble alkaline material in an amount sufficient to maintain the pH of the polymer-containing composition above about 9 until the composition has passed a substantial distance through the reservoir.