Societe Nationale Elf Aquitaine

Lino Vio

Gilles Meunier

Stabilization of aqueous solutions of polysaccharides, even in the hot, by the addition of alkali metal dialkyl-dithiocarbamate and sodium chloride or calcium chloride. Applications to drilling fluids and to the improved recovery of crude oil.

Process of thermal stabilization of aqueous solutions of polysaccharides

Improvements in the preparation of polymers of hydroxamic functions that consist in heating a polyacrylamide aqueous solution with a hydroxylamine salt at temperatures of from about 50.degree. to 85.degree. C. The polymers obtained are used as adjuvants of soil drilling muds, especially in petroleum drilling. The invention concerns itself with improvements in the preparation of polymers of hydroxamic functions, the resulting novel polymers, and applications thereof. The invention provides for the obtention of such polymers having a desired number of hydroxamic groups without noticeable formation of objectionable secondary products; it makes possible, in addition, the preparation of derivatives wherein the chain of the polymer and/or the hydroxamic groups contain different substituents.

Preparation of polymers of hydroxamic functions

The invention is clay based water drilling or completion muds with low viscosity and exceptional stability at elevated temperatures of up to 200.degree. C. The muds are characterized by containing from 1 to 10 grams per liter of a low molecular weight polymer or copolymer having functional groups wherein from 2 to 95% of the functional groups consist independently of hydroxamic or thiohydroxamic groups. The mud composition comprises (a) fresh water, water containing electrolytes such as sodium chloride, potassium chloride, calcium chloride, magnesium chloride, or seawater; (b) clay, chosen to suit the saline concentration of the water and to provide the necessary properties; and (c) one or more viscosity increasing materials.

Drilling and completion muds useful at elevated temperatures

A method for eliminating the scaling by deposit of alkaline earth compounds from an aqueous medium; to said medium is added an agent comprising a water-soluble polymer bearer of hydroxamic groups attached to a linear hydrocarbon chain.

Method for hindering the scaling by waters

A method for impeding the sedimentation of clays in water by adding a water-soluble compound. This compound is constituted by a polymer bearer of hydroxamic groups attached to a linear hydrocarbon chain. The amount of this adjuvant is small on the order of a few milligrams.

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Lino Vio