# US 11,306,242 B2 · Degradation agent for viscous fluid and method for producing said degradation agent

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 11,306,242 B2
- Document ID: US11306242B2
- Status: Granted
- Kind: B2
- Application number: 17/252,519
- Filed: 2019-08-01
- Published: 2021-08-26
- Granted: 2022-04-19
- Earliest claimed: 2018-08-13
- Assignees: Mitsubishi Gas Chemical Company, Inc.
- Applicants: Mitsubishi Gas Chemical Company, Inc.
- Inventors: Norifumi Tashiro; Katsuyuki Murai
- Web page: https://patentgrep.com/patent/US11306242B2

## CPC

- C09K 8/706: {Encapsulated breakers}
- C09K 8/805: {Coated proppants}
- C01G 49/14: Sulfates {(C01G49/0018 takes precedence)}
- C09K 8/62: Compositions for forming crevices or fractures
- E21B 43/26: by forming crevices or fractures
- C09K 2208/26: Gel breakers other than bacteria or enzymes
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C01G: COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts or peroxyacids C01B15/00; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium, or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds containing nitrogen, other non-metals and metal C01B21/082}; metal amides C01B21/092; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; compounds having molecular sieve properties but not having base-exchange properties C01B37/00; compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites, C01B39/00; cyanides C01C3/08; salts of cyanamide C01C3/16; thiocyanates C01C3/20)
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS

## 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.

## Claims

### Claim 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.

### Claim 2 (depends on 1)

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

### Claim 3 (depends on 1)

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

### Claim 4 (depends on 3)

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.

### Claim 5 (depends on 1)

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.

### Claim 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.

### Claim 7 (depends on 6)

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

### Claim 8 (depends on 6)

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

### Claim 9 (depends on 8)

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

### Claim 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.