# US 10,246,631 B2 · Method of stimulating a subterranean formation using an acid precursor composition

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- Number: US 10,246,631 B2
- Document ID: US10246631B2
- Status: Granted
- Kind: B2
- Application number: 15/523,270
- Filed: 2014-12-31
- Published: 2017-11-23
- Granted: 2019-04-02
- Earliest claimed: 2014-12-31
- Assignees: Halliburton Energy Services, Inc.
- Applicants: Halliburton Energy Services, Inc.
- Inventors: Steven Blattel; Eric Davidson
- Web page: https://patentgrep.com/patent/US10246631B2

## CPC

- C09K 8/725: {Compositions containing polymers}
- C09K 8/72: Eroding chemicals, e.g. acids
- C09K 8/74: combined with additives added for specific purposes
- C09K 8/80: Compositions for reinforcing fractures, e.g. compositions of proppants used to keep the fractures open
- E21B 43/25: Methods for stimulating production {(by vibrating earth formations E21B43/003)}
- E21B 43/27: by use of eroding chemicals, e.g. acids
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS

## Abstract

Methods of stimulating a subterranean formation using an acid precursor composition. A method of stimulating a subterranean formation. The method includes placing a fracturing composition in a subterranean formation. The method includes hydraulically fracturing the subterranean formation with the fracturing composition, to form at least one fracture and a spent fracturing composition. The method includes flushing the subterranean formation. The method includes placing an acid precursor composition in the subterranean formation, the acid precursor composition including an acid precursor. The method includes forming an acid from the acid precursor. The method also includes acidizing the subterranean formation with the formed acid.

## Claims

### Claim 1

A method of stimulating a subterranean formation, comprising:
placing a fracturing composition in a subterranean formation;
hydraulically fracturing the subterranean formation with the fracturing composition to form at least one fracture and a spent fracturing composition;
flushing the subterranean formation;
placing an acid precursor composition in the subterranean formation, wherein the precursor composition comprises greater than 7 to about 99 wt. %, based on the total weight of the precursor composition, of an acid precursor;
forming an acid from the acid precursor; and
acidizing the subterranean formation in the fracture with the formed acid.

### Claim 2 (depends on 1)

The method of claim 1, wherein the fracturing composition comprises a second acid, and wherein the second acid is about 1 wt % to about 40 wt % of the fracturing composition.

### Claim 3 (depends on 2)

The method of claim 2, wherein the second acid is at least one of acetic acid, formic acid, lactic acid, citric acid, oxalic acid, uric acid, glutaric acid, glutamic acid, glycolic acid, malonic acid, tartaric acid, adipic acid, sulfamic acid, chloroacetic acid, phthalic acid, a monoaminopolycarboxylic acid, a polyaminopolycarboxylic acid, a salt thereof, an ester thereof, or any combination thereof.

### Claim 4 (depends on 2)

The method of claim 2, wherein the second acid comprises at least one of hydrochloric acid, sulfuric acid, hydrofluoric acid, nitric acid, phosphoric acid, hydrobromic acid, perchloric acid or any combination thereof.

### Claim 5 (depends on 2)

The method of claim 2, wherein the second acid comprises hydrochloric acid, and wherein the subterranean formation comprises calcium carbonate, calcium sulfate, or a combination thereof.

### Claim 6 (depends on 1)

The method of claim 1, wherein the hydraulic fracturing comprises forming at least one fracture in the subterranean formation, and wherein the fracture is a dendritic fracture or an acid-etched fracture.

### Claim 7 (depends on 1)

The method of claim 1, wherein the spent fracturing composition comprises calcium chloride.

### Claim 8 (depends on 1)

The method of claim 1, wherein the hydraulic fracturing comprises forming at least one fracture in the subterranean formation, wherein the placing of the acid precursor in the subterranean formation comprises contacting the acid precursor and the fracture, and wherein the placing of the acid precursor in the subterranean formation comprises placing such that the acid precursor penetrates about 5 cm to about 2 m into a fracture face of the fracture.

### Claim 9 (depends on 1)

The method of claim 1, wherein the acid precursor comprises a substituted or unsubstituted (C1-C20)hydrocarbyl ester of a substituted or unsubstituted (C1-C20)alkanoic acid.

### Claim 10 (depends on 1)

The method of claim 1, wherein the acid precursor comprises homo- or hetero-anhydride of a substituted or unsubstituted (C1-C20)alkanoic acid.

### Claim 11 (depends on 1)

The method of claim 1, wherein the acid precursor comprises a (C1-C5)alkyl ester of a substituted or unsubstituted (C1-C5)alkanoic acid.

### Claim 12 (depends on 1)

The method of claim 1, wherein the acid precursor comprises a (C1-C5)alkyl ester or anhydride of a mono- or poly-hydroxy substituted (C1-C5)alkanoic acid.

### Claim 13 (depends on 1)

The method of claim 1, wherein the acid precursor comprises a substituted or unsubstituted (C1-C20)hydrocarbyl ester or anhydride of at least one of formic acid, acetic acid, lactic acid, glycolic acid, propionic acid, or any combination thereof.

### Claim 14 (depends on 1)

The method of claim 1, wherein the acid precursor comprises a polyethylene glycol di(C1-C5)alkanoate.

### Claim 15 (depends on 1)

The method of claim 1, wherein the acid precursor comprises at least one of diethylene glycol diformate, ethylene glycol monoformate, ethyl lactate, ethyl formate, methyl formate, glycerin diacetate, methyl lactate, or any combination thereof.

### Claim 16 (depends on 1)

The method of claim 1, wherein the forming the acid from the acid precursor comprises hydrolyzing the acid precursor by maintaining the acid precursor under subterranean conditions for a time of at least about 4 half-lives of a hydrolysis reaction of the acid precursor to produce the formed acid.

### Claim 17 (depends on 1)

The method of claim 1, wherein the fracturing composition or the acid precursor further comprises a proppant.

### Claim 18 (depends on 1)

A system for performing the method of claim 1, the system comprising:
a tubular disposed in the subterranean formation; and
a pump configured to pump the fracturing composition and the acid precursor in the subterranean formation through the tubular.

### Claim 19

A method of stimulating a subterranean formation, comprising:
placing a fracturing composition comprising hydrochloric acid in a subterranean formation comprising limestone;
hydraulically fracturing the subterranean formation with the fracturing composition to form at least one fracture and a spent fracturing composition comprising calcium chloride;
flushing the spent fracturing composition from the at least one fracture;
placing an acid precursor composition in the subterranean formation, wherein the acid precursor composition comprises greater than 7 to about 99 wt. %, based on the total weight of the acid precursor composition, of an acid precursor, and wherein the acid precursor penetrates at least about 1 cm into a fracture face of the fracture;
contacting the acid precursor and the fracture for at least 4 times an acid formation half-life of the acid precursor to produce an acid from the acid precursor; and
acidizing the subterranean formation in the fracture with the formed acid.

### Claim 20

A method of stimulating a subterranean formation, comprising:
placing a fracturing composition comprising a proppant and hydrochloric acid in a subterranean formation;
hydraulically fracturing the subterranean formation with the fracturing composition to form at least one fracture and a spent fracturing composition comprising calcium chloride;
flushing the spent fracturing composition from the at least one fracture;
placing an acid precursor composition in the subterranean formation, wherein the acid precursor composition comprises greater than 7 to about 99 wt. %, based on the total weight of the acid precursor composition, of an acid precursor, and wherein the acid precursor penetrates about 5 cm to about 2 m into a fracture face of the fracture, wherein the acid precursor comprises at least one of diethylene glycol diformate, ethylene glycol monoformate, ethyl lactate, ethyl formate, methyl formate, glycerin diacetate, methyl lactate, or any combination thereof;
contacting the acid precursor and the fracture for at least 4 times an acid formation half-life of the acid precursor to produce an acid from the acid precursor; and
acidizing the subterranean formation in the fracture with the formed acid.