# US 11,078,408 B2 · Methods for producing seawater based, high temperature viscoelastic surfactant fluids with low scaling tendency

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- Number: US 11,078,408 B2
- Document ID: US11078408B2
- Status: Granted
- Kind: B2
- Application number: 16/580,830
- Filed: 2019-09-24
- Published: 2020-01-16
- Granted: 2021-08-03
- Earliest claimed: 2017-07-27
- Assignees: Saudi Arabian Oil Company
- Applicants: Saudi Arabian Oil Company
- Inventors: Leiming Li; Feng Liang; Tao Chen
- Web page: https://patentgrep.com/patent/US11078408B2

## CPC

- C09K 8/68: containing organic compounds
- C02F 1/5236: {using inorganic agents}
- C09K 8/03: Specific additives for general use in well-drilling compositions
- C09K 8/602: {containing surfactants}
- C09K 8/604: {Polymeric surfactants}
- C02F 2101/101: {Sulfur compounds}
- C02F 2103/08: Seawater, e.g. for desalination
- C02F 2305/04: Surfactants, used as part of a formulation or alone
- C09K 8/506: containing organic compounds
- C09K 8/508: macromolecular compounds {(C09K8/512 takes precedence)}
- C09K 8/74: combined with additives added for specific purposes
- C09K 8/86: containing organic compounds
- C09K 8/88: macromolecular compounds
- C09K 2208/10: Nanoparticle-containing well treatment fluids
- C09K 2208/30: Viscoelastic surfactants [VES]
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes)

## Abstract

Embodiments of the present disclosure are directed to a method of producing a viscoelastic surfactant (VES) fluid, the VES fluid comprising desulfated seawater. The method of producing the VES fluid comprises adding an alkaline earth metal halide to seawater to produce a sulfate precipitate. The method further comprises removing the sulfate precipitate to produce the desulfated water. The method further comprises adding a VES and one or more of a nanoparticle viscosity modifier or a polymeric modifier to the desulfated seawater. Other embodiments are directed to VES fluids that maintain a viscosity greater than 10 cP at temperatures above 250° F.

## Claims

### Claim 1

A viscoelastic surfactant fluid comprising:
a viscoelastic surfactant comprising the general formula:
where R1 is a saturated or unsaturated hydrocarbon group of from 17 to 29 carbon atoms, R2 and R3, are each independently selected from a straight chain or branched alkyl or hydroxyalkyl group of from 1 to 6 carbon atoms, R4 is selected from H, hydroxyl, alkyl or hydroxyalkyl groups of from 1 to 4 carbon atoms; k is an integer of from 2-20; m is an integer of from 1-20; and n is an integer of from 0-20;
at least one nanoparticle viscosity modifier having a particle size of 0.1 to 500 nanometers and comprising one or more of carbon nanotubes, Zr compounds, Ce compounds, Al compounds, B compounds, Sn compounds, Cr compounds, or Si compounds;
desulfated seawater, where the desulfated water is free of CaSO4 precipitate; and
at least one stabilizing calcium salt.

### Claim 2 (depends on 1)

The viscoelastic surfactant fluid of claim 1, where the viscoelastic surfactant comprises erucamidopropyl hydroxypropylsultaine.

### Claim 3 (depends on 1)

The viscoelastic surfactant fluid of claim 1, where the viscoelastic surfactant fluid comprises from 0.1 vol. % to 20 vol. % of viscoelastic surfactant.

### Claim 4 (depends on 1)

The viscoelastic surfactant fluid of claim 1, where the viscoelastic surfactant fluid comprises from 1 wt. % to 50 wt. % of at least one stabilizing calcium salt.

### Claim 5 (depends on 1)

The viscoelastic surfactant fluid of claim 1, where the nanoparticle viscosity modifier is nonpolymeric.

### Claim 6 (depends on 1)

The viscoelastic surfactant fluid of claim 1, where the nanoparticle viscosity modifier comprises carbon nanotubes.

### Claim 7 (depends on 1)

The viscoelastic surfactant fluid of claim 1, where the viscoelastic surfactant fluid comprises from 0.001 wt. % to 5 wt. % nanoparticle viscosity modifier.

### Claim 8 (depends on 1)

The viscoelastic surfactant fluid of claim 1, where the viscoelastic fluid has a viscosity greater than or equal to 10 cP at a temperature greater than or equal to 300° F.