Polysaccharides, methods for preparing such polysaccharides and fluids utilizing such polysaccharides
First Claim
Patent Images
1. A water-soluble cellulose ether containing pendent vic dihydroxy structure having or capable of assuming a cis geometry and having a shear-thermal stability characteristic of at least about 30 at 250°
- F. for a 0.6 percent by weight aqueous solution of said cellulose ether crosslinked by a polyvalent metal ion.
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Abstract
Water-soluble polysaccharides, including cellulose ethers, containing pendent vicinal dihydroxy structure capable of cis geometry, which upon crosslinking with a polyvalent metal, have shear-thermal stability characteristics of at least about 30 at 250° F., are useful in oilfield applications.
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Citations
48 Claims
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1. A water-soluble cellulose ether containing pendent vic dihydroxy structure having or capable of assuming a cis geometry and having a shear-thermal stability characteristic of at least about 30 at 250°
- F. for a 0.6 percent by weight aqueous solution of said cellulose ether crosslinked by a polyvalent metal ion.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A process for preparing a water-soluble cellulose ether containing pendent vic dihydroxy structure having or capable of assuming a cis geometry which comprises:
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(a) charging a cellulose ether starting material to a diluent system including water in an amount sufficient to swell the cellulose ether starting material to provide a slurry in an enclosed reaction vessel, (b) stirring the slurry while sparging the reaction vessel with an inert gas to remove entrained air, (c) adding an alkaline material in an amount sufficient to catalyze the reaction of the cellulose ether with a reactant capable of incorporating into said cellulose ether a pendent vic dihydroxy structure, (d) adding said reactant over a predetermined period of time in an amount sufficient to incorporate in the cellulose ether a predetermined degree of substitution of pendent vic dihydroxy structure, (e) continuing stirring the slurry while allowing the reaction to be completed, the total reaction time being at least about 2 hours, the temperature being maintained throughout in the range of from about ambient conditions to reflux of the diluent system, (f) adding acid in an amount sufficient to neutralize the resulting water-soluble cellulose ether product and (g) recovering same, said cellulose ether having, upon cross-linking, a shear-thermal stability characteristic of at least about 30 at 250°
F. for a 0.6 percent by weight aqueous solution of said cellulose ether crosslinked by a polyvalent metal ion. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. A viscosified fluid comprising water, an effective viscosifying amount of a crosslinked water-soluble cellulose ether containing pendent vic dihydroxy structure having or capable of assuming a cis geometry, and a polyvalent metal cross-linker, said cellulose ether having a shear-thermal stability characteristic of at least about 30 at 250°
- F. for a 0.6 percent by weight aqueous solution of said cellulose ether crosslinked by a polyvalent metal ion.
- View Dependent Claims (35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48)
Specification