# US 11,441,064 B2 · Method of removing iron-containing scale from a wellbore, pipe, or surface using a biodegradable descaler solution

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

- Number: US 11,441,064 B2
- Document ID: US11441064B2
- Status: Granted
- Kind: B2
- Application number: 16/733,476
- Filed: 2020-01-03
- Published: 2021-07-08
- Granted: 2022-09-13
- Earliest claimed: 2020-01-03
- Assignees: King Fahd University of Petroleum and Minerals
- Applicants: King Fahd University of Petroleum and Minerals
- Inventors: Salaheldin Elkatatny; Mohamed Mahmoud; Hany Gamal; Abdullah Sultan
- Web page: https://patentgrep.com/patent/US11441064B2

## CPC

- C09K 8/528: inorganic depositions, e.g. sulfates or carbonates
- C09K 8/536: characterised by their form or by the form of their components, e.g. encapsulated material
- E21B 37/04: operated by fluid pressure, e.g. free-piston scrapers
- E21B 37/06: using chemical means for preventing or limiting {, e.g. eliminating,} the deposition of paraffins or like substances
- C09K 2208/32: Anticorrosion additives
- 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

A method of removing iron-containing scale from a wellbore, pipe, or metal-containing surface involving contacting the iron-containing scale with a biodegradable descaler solution of water, hydrochloric acid, formic acid, citric acid, a corrosion inhibitor, a corrosion inhibitor intensifier, and a surfactant. The method is performed at a pressure of 14 to 400 psi and a temperature of 100 to 150° C. The method removes iron-containing scale made of iron sulfide, iron carbonate, iron oxyhydroxide, and calcium carbonate. The method meets industry standard steel corrosion rates of less than 0.049 lb/ft2 per day. Also disclosed is a biodegradable descaler solution of water, hydrochloric acid, formic acid, citric acid, a corrosion inhibitor, a corrosion inhibitor intensifier, and a surfactant that meets OECD 301B thresholds for ready biodegradability.

## Claims

### Claim 1

A method for removing an iron-containing scale from a wellbore, pipe, or other metal-containing surface, the method comprising:
contacting the iron-containing scale with a biodegradable descaler solution comprising
55.75 to 80.49 wt % of water,
16.0 to 22.5 wt % of hydrochloric acid,
0.75 to 7.5 wt % of formic acid,
0.75 to 7.5 wt % of citric acid,
1.0 to 3.0 wt % of a corrosion inhibitor,
1.0 to 3.0 wt % of a corrosion inhibitor intensifier, and
0.01 to 0.75 wt % of a surfactant, each based on a total weight of the biodegradable descaler solution;
wherein the biodegradable descaler solution is contacted with the iron-containing scale at a pressure of 14 to 400 psi, and
wherein the iron-containing scale has a solubility of 75 to 95 g/L in the biodegradable descaler solution at a temperature of 100 to 150° C.,
wherein 70% of dissolved oxygen content is removed and 60% of theoretical CO2 is produced by the biodegradable descaler solution according to OECD 301B biodegradation test.

### Claim 2 (depends on 1)

The method of claim 1, wherein the iron-containing scale comprises iron sulfide, iron carbonate, iron oxyhydroxide, and calcium carbonate.

### Claim 3 (depends on 2)

The method of claim 2, wherein the iron sulfide is one or more selected from the group consisting of pyrrhotite (Fe7S8), troilite (hexagonal FeS), pyrite, (cubic FeS2), mackinawite (tetragonal FeS), and marcasite (orthorhombic FeS2).

### Claim 4 (depends on 1)

The method of claim 1, wherein the corrosion inhibitor is at least one selected from the group consisting of a salt of a N,N-diallyl-N-benzyl dodecyl ammonium cation and 3,5-diiodotyrosine.

### Claim 5 (depends on 1)

The method of claim 1, wherein the surfactant is an ionic surfactant.

### Claim 6 (depends on 5)

The method of claim 5, wherein the ionic surfactant is sodium dodecyl sulfate.

### Claim 7 (depends on 1)

The method of claim 1, wherein the corrosion inhibitor intensifier is at least one selected from the group consisting of tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione, methyl formate, and potassium iodide.

### Claim 8 (depends on 1)

The method of claim 1, wherein the biodegradable descaler solution has a density of 0.90 to 1.25 g/cm3 at 20 to 30° C.

### Claim 9 (depends on 1)

The method of claim 1, wherein the biodegradable descaler solution has a viscosity of 1.4 to 1.8 cP at 20 to 30° C. and a surface tension of 30 to 33 mN/m at 20 to 30° C.

### Claim 10 (depends on 1)

The method of claim 1, wherein the biodegradable descaler solution has a pH of −1.5 to −1.1 at 20 to 30° C.

### Claim 11 (depends on 1)

The method of claim 1, wherein the contacting is performed at a temperature of 100 to 150° C.

### Claim 12 (depends on 1)

The method of claim 1, wherein the contacting is performed for 1 to 48 hours.

### Claim 13 (depends on 1)

The method of claim 1, wherein the method removes the iron-containing scale while causing a corrosion rate of steel of less than 0.049 lb/ft2 per day at 100 to 150° C.

### Claim 14 (depends on 1)

The method of claim 1, wherein the biodegradable descaler solution is present at an initiation of the contacting in an amount of 1 L of biodegradable descaler solution per every 75 to 100 g of iron-containing scale.

### Claim 15 (depends on 1)

The method of claim 1, wherein the biodegradable descaler solution reaches a plateau of 75 to 99% of theoretical CO2 by day 40 according to OECD 301B biodegradation test.