Chitosan-containing well drilling and servicing fluids

• US 6,258,755 B1
• Filed: 12/28/1998
• Issued: 07/10/2001
• Est. Priority Date: 12/28/1998
• Status: Expired due to Fees

• Current Assignee: Venturemd Innovations, LLC
• Original Assignee: Venturemd Innovations, LLC
• Inventors: Cowan, Jack C., House, Roy F.
• Primary Examiner(s): Tucker, Philip
• Application Number:
  US09/222,293
• Time in Patent Office: 925 Days
• Field of Search: 507/110, 507/209, 507/211, 507/141, 507/145, 586/20, 586/55.3
• US Class Current: 507/110
• CPC Class Codes: C08L 5/08 Chitin; Chondroitin sulfate; Hyaluronic acid; Derivatives thereof
• CPC Class Codes: C09K 8/08 containing natural organic compounds, e.g. polysaccharides, or derivatives thereof

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.

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.

2. The method of claim 1 wherein the sugar is selected from the group consisting of arabinose, galactose, glucose, mannose, xylose, and mixtures thereof.

3. The method of claim 2 wherein the oligosaccharide contains from two to ten combined sugar units.

4. The method of claim 1 wherein there is added to the fluid (a) lactose, (b) dextrose, (c) an oligosaccharide mixture comprising pentosans and hexosans containing from two to ten combined sugar units selected from the group consisting of arabinose, galactose, glucose, mannose, xylose, and mixtures thereof, and (d) mixtures thereof.

5. The method of claim 1 wherein there is added 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.

10. The method of claim 1, 2, 3, 4, or 5 wherein the fluid is alkaline.

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.

7. The method of claim 6 wherein the aqueous chitosan-containing fluid is alkaline.

8. The method of claim 6 wherein a water soluble bisulfite compound is added to the fluid.

9. The method of claim 6 wherein a water soluble bisulfite compound is added to the fluid and the pH of the fluid is made alkaline.

24. The method of drilling a well using a conventional rotary drilling process wherein a drilling fluid is circulated in the weilbore during drilling comprising circulating as the drilling fluid a fluid prepared by the process of claim 6, 7, 8, or 9.

25. The method of claim 24 wherein the low shea rate viscosity of the fluid is at least 5,000 centipoise.

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.

12. The method of claim 11 wherein the sugar is selected from the group consisting of arabinose, galactose, glucose, mannose, xylose, and mixtures thereof.

13. The method of claim 12 wherein the oligosaccharide contains from two to ten combined sugar units.

14. The method of claim 11 wherein there is added to the fluid (a) lactose, (b) dextrose, (c) an oligosaccharide mixture comprising pentosans and hexosans containing from two to ten combined sugar units selected from the group consisting of arabinose, galactose, glucose, mannose, xylose, and mixtures thereof, and (d) mixtures thereof.

15. The method of claim 11 wherein there is added 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, xyloy and mixtures thereof.

16. The method of claim 11, 12, 13, 14, or 15 wherein the drilling fluid is alkaline.

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.

18. The method of claim 17 wherein the acid in the acidic chitosan solution is selected from the group consisting of (a) carboxylic acids containing from one to three carbon atoms, (b) substituted carboxylic acids containing at least one radical per molecule selected from the group consisting of hydroxyl, amino, chloro, thio, and mixtures thereof, and containing from one to three carbon atoms, (c) hydrochloric acid, (d) sulfamic acid, and (e) mixtures thereof.

19. The method of claim 17 wherein the acid in the acidic chitosan solution is selected from the group consisting of formic, acetic, propionic, glycolic, choline and mixtures thereof.

20. The method of claim 17 wherein the basic compound is selected from the group consisting of ammonium hydroxide, magnesium oxide, magnesium hydroxide, an alkali metal hydroxide, an alkali metal carbonate, an alkali metal bicarbonate, an alkali metal bisulfite, and mixtures thereof.

21. The method of claim 17 wherein the basic compound is sodium carbonate and the acid in the acidic chitosan solution is selected from the group consisting of acetic, glycolic, and mixtures thereof.

22. The method of claim 17, 18, 19, 20, or 21 wherein the low shear rate viscosity of the fluid is at least 5,000 centipoise.

23. The method of claim 17, 18, 19, 20, or 21 wherein the low shear rate viscosity of the fluid is at least 10,000 centipoise.