Degradation agent for viscous fluid and method for producing said degradation agent

Patent metadata

Field	Value
Publication number	US-11306242-B2
Application number	US-201917252519-A
Country	US
Kind code	B2
Filing date	Aug 1, 2019
Priority date	Aug 13, 2018
Publication date	Apr 19, 2022
Grant date	Apr 19, 2022

Abstract

A degradation agent for viscous fluids to be used in hydraulic fracturing methods is provided according to one aspect of the present invention, the degradation agent comprising a persulfate and an iron salt serving as an activator for the persulfate, wherein the persulfate and the iron salt have been coated and the ratio of the coating-film thickness (Y) in the iron salt to the coating-film thickness (X) in the persulfate, Y/X, is in the range of 0.35 to 1.0. The degradation agent for viscous fluids has properties suitable for use in hydraulic fracturing methods.

First claim

The invention claimed is:

1. A degradation agent for a viscous fluid used in a hydraulic fracturing method, the agent comprising a persulfate and an iron salt as an activator of said persulfate, wherein:
each of the persulfate and the iron salt is coated; and
the ratio (Y/X) of the coating-film thickness of the iron salt (Y) to the coating-film thickness of the persulfate (X) is in the range of 0.35 to 1.0.

2. The degradation agent according to claim 1 , wherein the persulfate is ammonium persulfate, sodium persulfate or potassium persulfate.

3. The degradation agent according to claim 1 , wherein the iron salt is an aqueous iron salt.

4. The degradation agent according to claim 3 , wherein the aqueous iron salt is ferrous sulfate, ferric sulfate, ammonium iron(II) sulfate or a hydrate thereof.

5. A viscous fluid used in a hydraulic fracturing method, the viscous fluid comprising a solvent, a gelling agent and the degradation agent according to claim 1 .

6. A method for producing a degradation agent for a viscous fluid used in a hydraulic fracturing method, the method comprising:
coating a persulfate to obtain a coated persulfate;
coating an iron salt to obtain a coated iron salt; and
mixing the coated persulfate and the coated iron salt,

wherein the ratio (Y/X) of the coating-film thickness of the iron salt (Y) to the coating-film thickness of the persulfate (X) is in the range of 0.35 to 1.0.

7. The method according to claim 6 , wherein the persulfate is ammonium persulfate, sodium persulfate or potassium persulfate.

8. The method according to claim 6 , wherein the iron salt is an aqueous iron salt.

9. The method according to claim 8 , wherein the aqueous iron salt is ferrous sulfate, ferric sulfate, ammonium iron(II) sulfate or a hydrate thereof.

10. A method for degrading a viscous fluid used in a hydraulic fracturing method, the method comprising adding a coated persulfate and a coated iron salt as an activator of said persulfate to the viscous fluid,
wherein the ratio (Y/X) of the coating-film thickness of the iron salt (Y) to the coating-film thickness of the persulfate (X) is in the range of 0.35 to 1.0.

Assignees

• Mitsubishi Gas Chemical Co

Inventors

• Tashiro norifumi
• Murai Katsuyuki

Classifications

• C09K8/706 Primary

  Encapsulated breakers · CPC title

• C09K8/805 Primary

  Coated proppants · CPC title

• C09K2208/26

  Gel breakers other than bacteria or enzymes · CPC title

• C01G49/14

  Sulfates {(C01G49/0018 takes precedence)} · CPC title

• C09K8/62

  Compositions for forming crevices or fractures · CPC title