Claims
- 1. A composition for dissolving an alkaline earth metal sulfate scale comprising:
- a) an aqueous solution having a pH of from about 8 to about 14 which pH is obtained by adjustment with potassium hydroxide;
- b) 0.1 to about 1.0M of a diethylenetriaminepentacetic acid (DTPA) chelating agent, or salts thereof; and
- c) a catalyst comprising formate anions having an ionization constant of less than about 10.sup.2 (K.sub.a <10.sup.-2) thereby making a composition which can dissolve substantially more of said scale within a substantially reduced time period than is possible with said chelating agent alone.
- 2. The composition of claim 1 which is heated to a temperature of from about 25.degree. C. to about 100.degree. C. or higher depending upon the depth to which said composition is injected into a subterranean formation.
- 3. The composition of claim 1 where substantially high saturation levels of dissolved barium, strontium or calcium sulfate are produced from the scale.
- 4. The composition of claim 1 where about 80% to about 90% of a saturation level of barium, strontium or calcium sulfate is dissolved from scale in about 10 minutes at a temperature of about 100.degree. C.
- 5. The composition of claim 1 where the scale comprises barium sulfate.
- 6. A composition for dissolving an alkaline earth metal sulfate scale comprising:
- a) an aqueous solution having a pH of from about 8 to about 14 which pH is obtained by adjustment with potassium hydroxide;
- b) 0.1 to about 1.0M of a diethylenetriaminepentacetic acid (DTPA) chelating agent, or salts thereof; and
- c) a catalyst comprising formate anions having an ionization constant of less than about 10.sup.2 (K.sub.a <10.sup.-2) in an amount sufficient to dissolve about 80%to 90% of said scale in about 10 minutes at a temperature of up to about 100.degree. C. or higher.
- 7. The composition as recited in claim 6 which is heated to a temperature of from about 25.degree. C. to about 100.degree. C. or higher depending upon the depth to which said composition is injected into a subterranean formation.
- 8. The composition as recited in claim 6 where substantially high saturation levels of dissolved barium, strontium or calcium sulfate are produced from the scale.
- 9. The composition as recited in claim 6 where said scale comprises barium sulfate.
- 10. An aqueous composition for dissolving barium or strontium sulfate scale comprising:
- a) an aqueous solution adjusted to a pH of about 12 with potassium hydroxide;
- b) 0.1 to about 1.0M of a DTPA chelating agent; and
- c) a catalyst comprising formate anions having an ionization constant of less than about 10.sup.2 (K.sub.a <10.sup.-2) in an amount sufficient to dissolve about 80%to 90% of said scale in about 10 minutes at a temperature of up to about 100.degree. C. or higher.
- 11. The composition as recited in claim 10 which is heated to a temperature of from about 25.degree. C. to about 100.degree. C. or higher depending upon the depth to which said composition is injected into a subterranean formation.
- 12. The composition as recited in claim 10 where substantially high saturation levels of dissolved barium and strontium sulfate are produced from the scale.
Parent Case Info
This is a division of copending application Ser. No. 07/332,147 filed on Apr. 3, 1989, now U.S. Pat. No. 5,093,020.
US Referenced Citations (11)
Foreign Referenced Citations (2)
Number |
Date |
Country |
57-107297 |
Jul 1982 |
JPX |
63-17819 |
Jan 1987 |
JPX |
Non-Patent Literature Citations (1)
Entry |
Hawleys Condensed Chemical Dictionary, 11th ed., Van Nostrand Reinhold, NY 1987, pp. 391, 486. |
Divisions (1)
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Number |
Date |
Country |
Parent |
332147 |
Apr 1989 |
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