Abstract: A water permeability contrast correction process to improve the sweep efficiency of waterflooding which involves the sequential injection of (1) an optional aqueous preflush slug to adjust connate water salinity, (2) an aqueous thickened slug comprising a sequestered polyvalent metal cation such as aluminum citrate and a gelable polymeric viscosifier such as polyacrylamide, (3) carbon dioxide to decrease the pH of the polymer slug which triggers the delayed in-situ gelation of said thickened slug to preferentially decrease water permeability in highly permeable thief zones, and (4) an aqueous drive fluid.

Abstract: Mineral values, particularly uranium, are recovered in situ from a heterogeneous subsurface earth formation containing the mineral values, which formation comprises zones of both high and low permeability, including injecting a plurality of separate slugs of leach solution adapted to solvate the mineral values into at least one injection well in communication with all zones of the formation, injecting a slug of a gas which is essentially insoluble in the leach solution between each two successive volumes of leach solution and withdrawing the pregnant leach solution, containing mineral values, from at least one production well in communication with all zones of the formation. The method can be further improved by injecting a mobility modifier, adapted to decrease the mobility of the leach solution, at the trailing end and/or leading end of the leach solution which is in contact with a slug of the gas. In a preferred embodiment, the mineral values contain significant amounts of uranium.

Abstract: Thiourea functions as a solution viscosity stabilizer in aqueous compositions comprising thiourea, nonionic polymers such as polyalkylene oxides and anionic surfactants such as petroleum sulfonates. The aqueous compositions are useful in connection with fluid-drive oil recovery processes, processes for drilling, completing, or working over wells, or the like processes in which a thickened fluid is injected into or brought into contact with a subterranean earth formation.

Abstract: In a method of propping a fracture in subterranean formations, the invention comprises placing in the fractures particulate solids such as sand coated with a water-repellent coating composition such as an oil-soluble organo-silicon compound. The water-repellent coated solid particulate propping agent can be prepared by dissolving an oil-soluble organo-silicon compound in a solvent therefor, admixing the resultant solution with particulate material, and thereafter evaporating the solvent to form a coating of organo-silicon compound on the particulate material.

Abstract: Thiourea functions as a solution viscosity stabilizer in aqueous compositions comprising thiourea, nonionic polymers such as polyalkylene oxides and anionic surfactants such as petroleum sulfonates. The aqueous compositions are useful in connection with fluid-drive oil recovery processes, processes for drilling, completing or working over wells, or the like processes in which a thickened fluid is injected into or brought into contact with a subterranean earth formation.

Abstract: An improved fluid for surfactant flooding a subterranean oil-bearing reservoir is prepared by contacting polymer with fresh water in the substantial absence of a salt; thereafter combining the thus-formed polymer solution and a salt solution; and finally adding a surfactant.

Abstract: The quantity of oil which can be economically recovered from an already waterflooded predominantly oil-wet formation is increased by passing a first solution through the formation to change the formation from its oil-wet to a water-wet state, passing a second solution having high interfacial tension with the oil through the formation to force the oil from the small pores of the formation into larger ones, and passing a third solution having a low interfacial tension between the third solution and the oil through the formation, optionally passing a mobility buffer-solution through the formation to prevent fingering or channeling, and finally passing the driving fluid through the formation.