Chitosan-containing well drilling and servicing fluids
First Claim
1. A method of enhancing the thermal stability of an aqueous chitosan-containing fluid which comprises adding to the fluid aldose or ketose sugars, oligosaccharides of such sugars, and mixtures thereof, and a water soluble bisulfite compound.
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Abstract
Disclosed are a process for the preparation of pseudoplastic, shear thinning chitosan-containing fluids, and a method of enhancing the thermal stability of such fluids. Pseudoplastic fluids useful oil and/or gas wells, particularly drilling fluids, drill-in fluids, workover fluids, completion fluids, perforating fluids, filter cake removal fluids, various pills, and the like, are prepared by solublizing chitosan in an acidic solution and thereafter raising the pH above about 7.0 by the addition of a basic compound thereto. The thermal stability of such fluids is enhanced by incorporating into the fluids certain aldose or ketose sugars, oligosaccharides of such sugars, and mixtures thereof, optionally together with a water soluble bisulfite compound.
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Citations
25 Claims
- 1. A method of enhancing the thermal stability of an aqueous chitosan-containing fluid which comprises adding to the fluid aldose or ketose sugars, oligosaccharides of such sugars, and mixtures thereof, and a water soluble bisulfite compound.
- 6. A method of enhancing the thermal stability of an aqueous chitosan-containing fluid which comprises adding to the fluid a mixture of pentosans and hexosans containing from one to ten sugar units selected from the group consisting of arabinose, galactose, glucose, mannose, xylose, and mixtures thereof, wherein the mixture is selected from the group consisting of the water soluble portion of thermally hydrolyzed lignocellulose, cane syrup solids, corn solubles, and mixtures thereof.
- 11. A method of drilling a well using a conventional rotary drilling process wherein a drilling fluid is circulated in the wellbore during drilling comprising circulating as the drilling fluid an aqueous chitosan-containing fluid which additionally contains aldose or ketose sugars, oligosaccharides of such sugars, and mixtures thereof.
- 17. A method of drilling a well using a conventional rotary drilling process wherein a drilling fluid is circulated in the wellbore during drilling comprising circulating as the drilling fluid an aqueous pseudoplastic fluid prepared by the process of forming an acidic chitosan solution and thereafter adding a basic compound to raise the pH above about 7.0, wherein the concentration of chitosan is sufficient to provide a fluid with a low shear rate viscosity of at least 1,000 centipoise and a shear thinning index greater than about 10.
Specification