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US4485874A
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Method for scale removal and scale inhibition in a well penetrating a subterranean formation
Assignee: Atlantic Richfield Co
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Filing: 1983-10-14
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Granted: 1984-12-04
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Expires: 2003-10-14
Abstract
Abstract Step declines in the production rate from a well following an acid treatment, and a scale inhibitor treatment are reversed by use of an EDTA treatment.
Inventors
- 👤 Kevin O. Meyers
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 15:05
CPC Classifications
C; C09; C09K; C09K8/00; C09K8/60; C09K8/62; C09K8/72; C09K8/74; C09K8/78; C09K8/52; C09K8/528; Y; Y10; Y10S; Y10S166/00; Y10S166/902; Y10S507/00; Y10S507/927
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
125 words
In a method for removing scale and inhibiting the formation of scale in a well penetrating a subterranean formation for the production of fluids from said formation, said method including; cleaning said well by injecting an aqueous solution of a suitable mineral acid into said well in an amount and for a time effective to remove scale from said well and thereafter injecting a scale inhibitor into said formation about said well through said well so that said scale inhibitor is thereafter slowly released from said formation to inhibit the formation of scale, an improvement comprising: injecting an aqueous solution of a chelating agent into said well in an amount and for a time effective to remove precipitates of multi-valent cations and said scale inhibitor.
Claim 2
Dependent Claim
125 words
In a method for removing scale and inhibiting the formation of scale in a well penetrating a subterranean formation for the production of fluids from said formation, said method including; cleaning said well by injecting an aqueous solution of a suitable mineral acid into said well in an amount and for a time effective to remove scale from said well and thereafter injecting a scale inhibitor into said formation about said well through said well so that said scale inhibitor is thereafter slowly released from said formation to inhibit the formation of scale, an improvement comprising: injecting an aqueous solution of a chelating agent into said well in an amount and for a time effective to remove precipitates of multi-valent cations and said scale inhibitor.
Claim 3
Dependent Claim
11 words
The method of claim 1 wherein said scale comprises calcium carbonate.
Claim 4
Dependent Claim
12 words
The method of claim 2 wherein said mineral acid is hydrochloric acid.
Claim 5
Dependent Claim
14 words
The method of claim 2 wherein said scale inhibitor comprises a phosphonic acid derivative.
Claim 6
Dependent Claim
13 words
The method of claim 2 wherein said scale inhibitor comprises a phosphate ester.
Claim 7
Dependent Claim
11 words
The method of claim 2 wherein said scale inhibitor comprises polyacrylamides.
Claim 8
Dependent Claim
17 words
The method of claim 2 wherein said multi-valent cations comprise ions of calcium, magnesium, barium and iron.
Claim 9
Dependent Claim
11 words
The method of claim 2 wherein said chelating agent is EDTA.
Claim 10
Dependent Claim
34 words
The method of claim 8 wherein said aqueous solution of said chelating agent is controlled to contact the wellbore, wellbore perforations and said formation about said well into which said scale inhibitor was injected.
Claim 11
Dependent Claim
27 words
The method of claim 2 wherein said aqueous solution of said chelating agent is injected after a step decline in the production of fluids from said well.
Claim 12
Dependent Claim
32 words
The method of claim 2 wherein said injection of said aqueous solution of said chelating agent is controlled to contact the wellbore, wellbore perforations and portions of said formation near said well.
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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) | 1987-12-04 | 1988-06-04 | 1988-12-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-12-04 | 1992-06-04 | 1992-12-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-12-04 | 1996-06-04 | 1996-12-04 | $7700.00 | Window Closed / Lapsed |