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US4317735A
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Method of inhibiting crosslinking of aqueous xanthan gums in the presence of ferric acid ions
Assignee: Schlumberger Technology Corp
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Filing: 1980-03-18
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Granted: 1982-03-02
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Expires: 2000-03-18
Abstract
Abstract Aqueous xanthan gums normally crosslink at a pH greater than about 1.5 in the presence of ferric ions. This phenomenon is undesirable under many conditions of use, such as acidizing treatments of wells, and is inhibited or prevented by adding certain soluble alkanoic and/or alkenoic acids to the system. The alkanoic and alkenoic acids have at least 4 carbon atoms and bear at least 2 alcoholic hydroxyl groups per molecule and can be added as the organic acid per se or as a soluble salt or γ-lactone. Ascorbic acid and erythorbic acid are examples.
Inventors
- 👤 Curtis W. Crowe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 08:54
CPC Classifications
C; C09; C09K; C09K8/00; C09K8/60; C09K8/84; C09K8/86; C09K8/88; C09K8/90; C09K8/905; C09K8/62; C09K8/72; C09K8/74; E; E21; E21B; E21B43/00; E21B43/02; E21B43/025; Y; Y10; Y10S; Y10S507/00; Y10S507/933; Y10S507/934
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
74 words
A method of inhibiting the cross-linking of an aqueous solution of xanthan gum in the presence of ferric ion at a pH above about 1.3 comprising adding to an aqueous solution of non-crosslinked xanthan gum, at a pH less than about 1.5, ascorbic acid and/or erythorbic acid, and/or a soluble salt of said acid in an amount sufficient to inhibit or prevent the crosslinking of the xanthan gum in the presence of ferric ion.
Claim 2
Independent Claim
74 words
A method of inhibiting the cross-linking of an aqueous solution of xanthan gum in the presence of ferric ion at a pH above about 1.3 comprising adding to an aqueous solution of non-crosslinked xanthan gum, at a pH less than about 1.5, ascorbic acid and/or erythorbic acid, and/or a soluble salt of said acid in an amount sufficient to inhibit or prevent the crosslinking of the xanthan gum in the presence of ferric ion.
Claim 3
Independent Claim
70 words
A method of preparing an aqueous gelled acid inhibited against cross-linking in the presence of ferric ion comprising adding to an aqueous acid at a pH of less than about 1.5 (a) a xanthan gum, and (b) a soluble alkanoic and/or alkenoic acid, and/or a soluble salt of said acid in an amount sufficient to inhibit or prevent the crosslinking of the xanthan gum in the presence of ferric ion.
Claim 4
Independent Claim
70 words
A method of preparing an aqueous gelled acid inhibited against cross-linking in the presence of ferric ion comprising adding to an aqueous acid at a pH of less than about 1.5 (a) a xanthan gum, and (b) a soluble alkanoic and/or alkenoic acid, and/or a soluble salt of said acid in an amount sufficient to inhibit or prevent the crosslinking of the xanthan gum in the presence of ferric ion.
Claim 5
Dependent Claim
20 words
The method defined by claim 2 wherein (a) and (b) are added as a solid mixture or a liquid concentrate.
Claim 6
Dependent Claim
28 words
The method defined by claim 3 wherein (a) and (b) are added as a solid mixture of xanthan gum and an alkali metal or ammonium salt of (b).
Claim 7
Dependent Claim
73 words
A mixture of (a) a xanthan gum and (b) ascorbic and or erythorbic acid, and/or a soluble salt of said acid wherein the ratio of (a) to (b) is from about 4 to about 6 parts by weight of (a) per part by weight of (b); said mixture having the chemical property of forming an aqueous gelled acid inhibited against crosslinking in the presence of ferric ion when mixed with an aqueous acid.
Claim 8
Dependent Claim
73 words
A mixture of (a) a xanthan gum and (b) ascorbic and or erythorbic acid, and/or a soluble salt of said acid wherein the ratio of (a) to (b) is from about 4 to about 6 parts by weight of (a) per part by weight of (b); said mixture having the chemical property of forming an aqueous gelled acid inhibited against crosslinking in the presence of ferric ion when mixed with an aqueous acid.
Claim 9
Dependent Claim
22 words
The mixture defined by claim 5 wherein said mixture is a solid mixture or an aqueous liquid concentrate of (a) and (b).
Claim 10
Dependent Claim
25 words
The mixture defined by claim 6 wherein said mixture is a solid mixture of xanthan gum and an alkali metal or ammonium salt of (b).
Claim 11
Dependent Claim
70 words
A gelled aqueous acid composition comprising an aqueous acid at a pH of less than about 1.5, a gelling amount of a xanthan gum, and a soluble alkanoic and/or alkenoic acid having at least 4 carbon atoms and bearing at least 2 hydroxyl groups per molecule, and/or a soluble salt of said acid in an amount sufficient to inhibit crosslinking of said xanthan gum in the presence of ferric ion.
Claim 12
Dependent Claim
70 words
A gelled aqueous acid composition comprising an aqueous acid at a pH of less than about 1.5, a gelling amount of a xanthan gum, and a soluble alkanoic and/or alkenoic acid having at least 4 carbon atoms and bearing at least 2 hydroxyl groups per molecule, and/or a soluble salt of said acid in an amount sufficient to inhibit crosslinking of said xanthan gum in the presence of ferric ion.
Claim 13
Dependent Claim
35 words
In the method of increasing permeability of a subterranean formation surrounding a wellbore by contact with a treatment acid, the improvement of using the gelled aqueous acid defined by claim 8 as the treatment acid.
Claim 14
Dependent Claim
11 words
The method defined by claim 1 wherein acid is erythorbic acid.
Claim 15
Dependent Claim
11 words
The method defined by claim 2 wherein acid is erythorbic acid.
Claim 16
Dependent Claim
11 words
The mixture defined by claim 5 wherein acid is erythorbic acid.
Claim 17
Dependent Claim
11 words
The composition defined by claim 8 wherein acid is erythorbic acid.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-03-01 | 1985-08-31 | 1986-03-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-03-01 | 1989-08-31 | 1990-03-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-03-01 | 1993-08-31 | 1994-03-02 | $7700.00 | Window Closed / Lapsed |