Abstract: A process for insulating a tubing string placed in a pipe and through which a fluid circulates, the insulant being a non-rigid foam produced from a liquid solution and placed in the annular space defined by the outside of the tubing string and the walls of the pipe in which these tubings are placed. A production well (1) opens, in the lower part thereof, onto a producing rock containing a fluid to be extracted. Tubing (2) is placed in production well (1). A zone (3) represents the annulus defined between the outside (5) of the tubing string and the walls of well (1) in which the tubing string is placed. A tube for injecting a liquid and/or gaseous fluid (4) is placed in annulus (3) and a liquid and/or gaseous fluid injection nozzle (6) opens into zone (3).

Abstract: The invention has as its object the use of new composition of gels that can be used for the reduction of the production of water in oil- or gas-producing wells.The compositions of gels comprise a solution of at least one water-soluble complex of a polyvalent metallic cation such as zirconium lactate able to cross link a nonionic polysaccharide such as scleroglucan, at a concentration of 2 to 10,000 parts per million of parts, expressed by weight of metal dioxide. With a preferred concentration of 2 to 100 ppm, the oil permeability is not appreciably affected.The compositions make possible the formation of aqueous gels of scleroglucan that can be used for the prevention of inflows of water into the hydrocarbon-producing wells.

Abstract: Liquid composition for the production of a gel in a well drilled in the ground which is comprised of a hydrophilic polymer. Its liquid medium consists of an organic liquid at least partially miscible with water.

Abstract: For selectively reducing permeability to water in an underground formation producing oil and/or gas, injecting into the formation a composition comprising water, at least one water soluble aldehyde compound at a concentration (by weight) of 180 to 20,000 ppm and at least one non-ionic polysaccharide at a concentration (by weight) of 200 to 5000 ppm, the concentration of aldehyde compound being higher than that of polysaccharide. The composition may be used in the water injection well or the hydrocarbon producing well and may assist in the recovery of hydrocarbons.

Abstract: This process comprises injecting a non-hydrolyzed acrylamide polymer or copolymer into the producing formation and producing hydrolysis thereof in situ by subsequent injection of an alkali metal basic compound. It is then possible to restart the well in oil or gas production.

Abstract: By a new process, inverse microlatices of watersoluble copolymers are prepared by copolymerization within an inverse microemulsion obtained by admixing an aqueous phase containing the hydrosoluble monomers to be copolymerized, an organic phase and a non-ionic surfactant or a mixture of non-ionic surfactants, whose H L B ranges from 8 to 11.The resultant microlatices can be diluted in water so as to form thickened solutions, which can be used to improve the production of hydrocarbons from oil formations, particularly in enhanced recovery methods or methods for preventing water inflows in producing wells.

Abstract: A transparent and stable microlatex is dispersed into water and the resultant solution is used for treating an oil or gas well to achieve enhanced oil recovery. The microlatex is prepared by polymerization of a water-soluble monomer in a microemulsion of the water-in-oil type.

Abstract: Stable suspension of a water-soluble polymer comprising solid particles of this water-soluble polymer in a liquid hydrocarbon medium which also comprises a thickening agent selected from the alkali or alkaline-earth metal salts of fatty acids having 6-33 carbon atoms. The resultant suspensions are stable and dissolve easily when dispersed in water; they can be used in enhanced oil recovery. They may also contain minor proportions of water and/or of C.sub.1 -C.sub.12 monoalcohols or C.sub.2 -C.sub.12 diols.

Abstract: The filtrability of xanthan gum aqueous solutions is improved by an enzymatic treatment in two successive steps, the first step by means of a polysaccharase and the second step by means of a protease, the operating conditions of each step being such that the corresponding enzyme is active in said step.

Abstract: Enzymatic treatment, in aqueous dispersion, of a xanthan gum containing bacteria cell residues and microgels, as impurities, by means of Basidiomycete cellulase, the aqueous dispersion having a pH from 3 to 7 and containing at least 0.1 equivalent/liter of at least one salt of alkali or alkaline-earth metal, said treatment being conducted at a temperature from 25.degree. to 65.degree. C., improved the injectivity and filtrability thereof.

Abstract: An aqueous composition is provided, suitable for direct use in waterflood oil recovery processes, which comprises the clarified fermentation fluid obtained by(a) culturing a polysaccharide-producing microorganism in an aqueous culture medium to produce an aqueous culture containing dissolved polysaccharide therein; and(b) clarifying the resultant aqueous culture from (a) by at least one of centrifugation and filtration, introducing therein at least one bactericidal agent, and recovering the resultant clarified fermentation fluid;said aqueous composition being obtained without precipitation and recovery of a solid polysaccharide and dissolution thereof in an aqueous medium.The above composition can be pumped into oil formations without substantial clogging thereof.

Abstract: A solid composition of coated water-soluble polymer is made from 80 to 250 parts b.w. of solid particles of at least one water-soluble polymer coated with 100 parts b.w. of at least one paraffinic product solid at room temperature and whose melting point is preferably from 40.degree. to 90.degree. C. The solid composition is made by dispersing particles of the water-soluble polymer in the molten paraffinic product and then cooling down to room temperature.

Abstract: Stable suspension of a water-soluble polymer comprising solid particles of this water-soluble polymer in a liquid hydrocarbon medium which also comprises a thickening agent selected from the alkali or alkaline-earth metal salts of fatty acids having from 6-33 carbon atoms. The resultant suspensions are stable and dissolve easily when dispersed in water; they can be used in enhanced oil recovery.