US3584686A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Prevention of calcium sulfate scale in a waterflooding process
Assignee: Cities Service Oil Co
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Filing: 1969-12-08
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Granted: 1971-06-15
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Expires: 1989-12-08
Abstract
Abstract A method of minimizing the deposits of calcium sulfate near the production well during the process of secondary oil recovery by waterflooding utilizing an injection fluid whose mineral content has been supplemented by the addition of salts. In order to prevent calcium sulfate from precipitating near the reduced pressure area of the production wellbore during waterflooding the total mineral salt content of the fluid drive is adjusted to a high enough concentration so that the solubility of CaSO4, which dissolves in the fluid drive as it passes through the formation, does not decrease as the pressure on the waterflood decreases. Sodium chloride may be taken alone or in combination with controlled amounts of mineral salts, such as calcium chloride, sodium sulfate, magnesium chloride, or sodium bicarbonate to adjust the mineral content of the fluid drive.
Inventors
- 👤 Richard S Fulford
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 03:21
CPC Classifications
C; C09; C09K; C09K8/00; C09K8/52; C09K8/528
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
114 words
In a process for the secondary recovery of oil comprising injecting brine from a subterranean formation, such brine containing an adverse bivalent metallic chloride concentration which aids gypsum formation and having at least about a 240 grams per liter water soluble mineral salt concentration, into an oil reservoir having a calcium sulfate content and simultaneously producing a displaced oil from a production well, the improvement which comprises removing the bivalent metallic chloride concentration from the brine prior to its injection into the oil reservoir by treatment of the brine with a water soluble metallic hydroxide which precipitates the adverse bivalent metals so as to minimize calcium sulfate deposition in the reservoir and production well.
Claim 2
Dependent Claim
12 words
The method of claim 2 in which the hydroxide is barium hydroxide.
Claim 3
Dependent Claim
58 words
The process of claim 2 in which the brine from the subterranean formation originally has a salt concentration less than 240 grams per liter water soluble mineral salt concentration and further comprising introducing additional salt into the brine to maintain at least about a 240 grams per liter salt concentration in the brine injected into the oil reservoir.
Claim 4
Dependent Claim
88 words
In a process for the secondary recovery of oil comprising injecting brine from a subterranean formation, said brine containing an adverse bivalent metallic chloride concentration which aids gypsum formation and having at least about a 240 grams per liter water soluble mineral salt concentration, into an oil reservoir having a calcium sulfate content and simultaneously producing displaced oil from a production well, the improvement which comprises neutralizing the adverse bivalent metallic chlorides by chemical means so as to minimize calcium sulfate deposition in the reservoir and production well.
Claim 5
Dependent Claim
23 words
The method of claim 5 in which the bivalent metallic chloride concentration is neutralized by the addition of sodium bicarbonate to the brine.
Claim 6
Dependent Claim
22 words
The method of claim 6 in which the sodium bicarbonate concentration of the brine is about 0.5 to 5.0 grams per liter.
Claim 7
Dependent Claim
23 words
The method of claim 5 in which the bivalent metallic chloride concentration is neutralized by the addition of sodium bicarbonate to the brine.
Claim 8
Dependent Claim
80 words
The method of claim 8 in which the sodium bicarbonate concentration of the brine is about 0.5 to 5.0 grams per liter. 10 The process of claim 5 in which the brine from the subterranean formation originally has a salt concentration less than 240 grams per liter water soluble mineral salt and further comprising introducing additional salt into the brine to maintain at least about a 240 grams per liter salt concentration in the brine injected into the oil reservoir.
Claim 9
Dependent Claim
122 words
In a process for the secondary recovery of oil comprising injecting a brine from a subterranean formation, such brine having a total salt concentration of less than 240 grams per liter, into an oil reservoir having a calcium sulfate content and simultaneously producing displaced oil from a production well, the improvement which comprises introducing additional salt into the brine to maintain at least about a 240 grams per liter salt concentration in the brine injected into the oil reservoir and in which the additional salt added includes sodium chloride up to a total sodium chloride concentration of at least about 170 grams per liter and sodium sulfate up to a total sodium sulfate concentration of at least about 63 grams per liter.
Claim 10
Dependent Claim
12 words
The method of claim 11 in which the hydroxide is barium hydroxide.
References Cited (Backward Citations)
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Cited
US3091291A
Cited
US3087539A
Cited
US3175610A
Cited
US3258071A
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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) | 1974-06-14 | 1974-12-14 | 1975-06-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-06-14 | 1978-12-14 | 1979-06-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-06-14 | 1982-12-14 | 1983-06-15 | $7700.00 | Window Closed / Lapsed |