US3889753A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Buffer regulated mud acid
Assignee: Shell USA Inc
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Filing: 1974-02-21
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Granted: 1975-06-17
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Expires: 1994-02-21
Abstract
Abstract In reacting a siliceous material with an acidic solution containing hydrogen fluoride, the reaction rate is kept relatively low by contacting the material with an aqueous solution of a fluoride salt, a weak acid and a weak acid salt in proportions that maintain a significant but low concentration of hydrogen fluoride in the solution.
Inventors
- 👤 Edwin A Richardson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 01:55
CPC Classifications
C; C09; C09K; C09K8/00; C09K8/60; C09K8/62; C09K8/72; Y; Y10; Y10S; Y10S507/00; Y10S507/933
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
120 words
A well treating process which comprises: flowing fluid into a well to contact a siliceous material to be acidized in or around the borehole of the well; and including in the fluid an aqueous solution of a fluoride salt, a weak acid, and a weak acid salt, in proportions that provide within the solution at the time it flows into the well a fluoride salt concentration equivalent to at least a clay-dissolving proportion of hydrogen fluoride, a weak acid concentration sufficient to convert at least an effective amount of fluoride salt to hydrogen fluoride, and a weak acid salt concentration sufficient to provide a ratio of weak aciD to weak acid salt that limits the rate of the acidizing reaction.
Claim 2
Dependent Claim
120 words
A well treating process which comprises: flowing fluid into a well to contact a siliceous material to be acidized in or around the borehole of the well; and including in the fluid an aqueous solution of a fluoride salt, a weak acid, and a weak acid salt, in proportions that provide within the solution at the time it flows into the well a fluoride salt concentration equivalent to at least a clay-dissolving proportion of hydrogen fluoride, a weak acid concentration sufficient to convert at least an effective amount of fluoride salt to hydrogen fluoride, and a weak acid salt concentration sufficient to provide a ratio of weak aciD to weak acid salt that limits the rate of the acidizing reaction.
Claim 3
Dependent Claim
19 words
The process of claim 1 in which the fluid is flowed into a subterranean reservoir containing a siliceous material.
Claim 4
Dependent Claim
22 words
The process of claim 2 in which the fluid is flowed into the reservoir during the forming or treating of a fracture.
Claim 5
Dependent Claim
26 words
The process of claim 1 in which a portion of strong acid is dissolved in the aqueous acidizing solution to cause an initially relatively rapid reaction.
Claim 6
Dependent Claim
44 words
The process of claim 1 in which the siliceous material is contacted with successive portions of the aqueous acidizing solution to acidize more than the amount of the material that would be acidized by a volume sufficient to merely immerse or permeate the material.
Claim 7
Dependent Claim
32 words
The process of claim 1 in which the fluoride salt is an ammonium salt of hydrofluoric acid and the weak acid and weak acid salt are, respectively, formic acid and ammonium formate.
Claim 8
Dependent Claim
32 words
The process of claim 1 in which the fluoride salt is an ammonium salt of hydrofluoric acid and the weak acid and weak acid salt are, respectively, acetic acid and ammonium acetate.
Claim 9
Dependent Claim
115 words
A PROCESS FOR ACIDIZING A SILICEOUS MATERIAL IN A REMOTE LOCATION INTO WHICH A FLUID CAN BE FLOWED, WHICH COMPRISES: FLOWING FLUID INTO SAID REMOTE LOCATION TO CONTACT THE MATERIAL TO BE ACIDIZED; AND INCLUDING IN THE FLUID AN AQUEOUS SOLUTION WHICH, AT THE TIME OF ITS INCLUSION, CONTAINS AN AMOUNT OF FLUORIDE SALT EQUIVALENT TO AT LEAST AN EFFECTIVE AMOUNT OF HYDROGEN FLUORIDE FOR ACIDIZING A SILICEOUS MATERIAL, AT LEAST ENOUGH WEAK ACID TO CONVERT THE FLUORIDE SALT TO AN EFFECTIVE AMOUNT OF HYDROGEN FLUORIDE, AND ENOUGH WEAK ACID SALT TO PROVIDE A RATIO OF WEAK ACID TO WEAK ACID SALT THAT LIMITS THE RATE OF SILICEOUS MATERIAL ACIDIZATION TO SUBSTANTIALLY A SELECTED RATE.
Claim 10
Dependent Claim
115 words
A PROCESS FOR ACIDIZING A SILICEOUS MATERIAL IN A REMOTE LOCATION INTO WHICH A FLUID CAN BE FLOWED, WHICH COMPRISES: FLOWING FLUID INTO SAID REMOTE LOCATION TO CONTACT THE MATERIAL TO BE ACIDIZED; AND INCLUDING IN THE FLUID AN AQUEOUS SOLUTION WHICH, AT THE TIME OF ITS INCLUSION, CONTAINS AN AMOUNT OF FLUORIDE SALT EQUIVALENT TO AT LEAST AN EFFECTIVE AMOUNT OF HYDROGEN FLUORIDE FOR ACIDIZING A SILICEOUS MATERIAL, AT LEAST ENOUGH WEAK ACID TO CONVERT THE FLUORIDE SALT TO AN EFFECTIVE AMOUNT OF HYDROGEN FLUORIDE, AND ENOUGH WEAK ACID SALT TO PROVIDE A RATIO OF WEAK ACID TO WEAK ACID SALT THAT LIMITS THE RATE OF SILICEOUS MATERIAL ACIDIZATION TO SUBSTANTIALLY A SELECTED RATE.
Claim 11
Dependent Claim
115 words
In a process for treating a well by injecting an acidic solution into the well to contact a siliceous material in or around the borehole, the improvement which comprises: compounding the acidic solution to be so injected by dissolving a fluoride salt, a weak acid, and a weak acid salt in an aqueous liquid in proportions providing an amount of fluoride salt equivalent to at least an effective amount of hydrogen fluoride for acidizing a siliceous material, at least enough weak acid to convert the fluoride salt to an effective amount of hydrogen fluoride, and enough weak acid to provide a ratio of weak acid to weak acid salt that limits the rate of acidization.
Claim 12
Dependent Claim
115 words
In a process for treating a well by injecting an acidic solution into the well to contact a siliceous material in or around the borehole, the improvement which comprises: compounding the acidic solution to be so injected by dissolving a fluoride salt, a weak acid, and a weak acid salt in an aqueous liquid in proportions providing an amount of fluoride salt equivalent to at least an effective amount of hydrogen fluoride for acidizing a siliceous material, at least enough weak acid to convert the fluoride salt to an effective amount of hydrogen fluoride, and enough weak acid to provide a ratio of weak acid to weak acid salt that limits the rate of acidization.
Claim 13
Dependent Claim
81 words
The process of claim 9 in which the amount of dissolved fluoride salt is equivalent to from about 0.1 to 3 moles per liter hydrogen fluoride, the amount of dissolved weak acid is at least enough to convert a significant proportion of the fluoride salt to hydrogen fluoride and the amount of dissolved weak acids salt provides a ratio of weak acid to weak acid salt that buffers the pH of the solution at a value of from 3 to 6.
Claim 14
Dependent Claim
33 words
The process of claim 9 in which the fluoride salt is an ammonium salt of a hydrofluoric acid and the weak acid and weak acid salt are, respectively, formic acid and ammonium formate.
Claim 15
Dependent Claim
32 words
The process of claim 9 in which the fluoride salt is an ammonium salt of hydrofluoric acid and the weak acid and weak acid salt are respectively acetic acid and ammonium acetate.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-06-16 | 1978-12-16 | 1979-06-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-16 | 1982-12-16 | 1983-06-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-16 | 1986-12-16 | 1987-06-17 | $7700.00 | Window Closed / Lapsed |