WO2012154332A2

WO2012154332A2 - Stable nanoparticles for highly saline conditions

Info

Publication number: WO2012154332A2
Application number: PCT/US2012/032170
Authority: WO
Inventors: Vicki L. Colvin; Huiguang Zhu
Original assignee: William Marsh Rice University
Priority date: 2011-04-04
Filing date: 2012-04-04
Publication date: 2012-11-15
Also published as: WO2012154332A3

Abstract

Surface-modified nanomaterials and methods of making surface-modified nanomaterials comprising synthesizing an amphiphilic copolymer, providing a nanomaterial, and modifying the surface of the nanomaterial with the amphiphilic copolymer.

Description

STABLE NANOPARTICLES FOR HIGHLY SALINE CONDITIONS

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No. 61/471,518 filed April 4, 2011, which is incorporated herein by reference. GOVERNMENT SUPPORT CLAUSE

This invention was made with government support under Grant No: EEC-0647452 awarded by the National Science Foundation. The government has certain rights in the invention.

BACKGROUND

Nanomaterials generally may be considered structures with at least one characteristic dimension measured in nanometers. Nanomaterials may be designed to exhibit novel and improved physical, chemical, and biological properties due to their size.

SUMMARY

The present disclosure generally relates to nanomaterials. More particularly, the present disclosure relates to surface-modified nanoparticles that are suitable for use in high salinity environments.

In an embodiment, the present disclosure provides a method of forming a surface- modified nanomaterial comprising synthesizing an amphiphilic copolymer, providing a nanomaterial, and modifying the surface of the nanomaterial with the amphiphilic copolymer.

In an embodiment, the present disclosure provides a surface-modified nanomaterial comprising a nanomaterial wherein a surface of the nanomaterial has been modified with an amphiphilic copolymer.

In an embodiment, the present disclosure provides a treatment fluid comprising a nanomaterial wherein a surface of the nanomaterial has been modified with an amphiphilic copolymer.

The features and advantages of the present invention will be apparent to those skilled in the art. While numerous changes may be made by those skilled in the art, such changes are within the spirit of the invention. DRAWINGS

The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

Some specific example embodiments of the disclosure may be understood by referring, in part, to the following description and the accompanying drawings.

Figure 1 is a drawing of two reaction mechanisms of embodiments of the present invention.

Figure 2 is structural drawing of an amphiphilic copolymer of an embodiment of the present invention.

Figure 3 is a drawing of a coating mechanism of an embodiment of the present invention.

Figure 4 is a chart depicting an effect of salt concentration on the size of QD_PAMPS nanoparticles.

Figure 5 is a chart depicting an effect of salt concentration on the size of gold nanoparticles.

Figure 6 is a photograph depicting colloidal stability of quantum dots with PAA and PAMPS coatings.

Figure 7 is a photograph depicting stability of quantum dots with PAA coatings. Figure 8 depicts photographs and a chart demonstrating an effect of pH on quantum dots.

Figure 9 depicts TEM images of quantum dots.

Figure 10 depicts charts showing an effect of salt concentration and pH on nano- magnetite particle size.

Figure 1 1 depicts a photograph demonstrating stability of nMagJPAA and nMag_PAMPS nanoparticles and TEM images of nMag_PAMPS nanoparticles.

Figure 12 is a chart depicting a result of stability studies of nMag_PAMPS nanoparticles.

Figure 13 depicts photographs demonstrating the stability of nMag_PAMPS nanoparticles.

Figure 14 is a chart depicting results of stability studies of nMag_PAMPS nanoparticles.

Figure 15 is a chart depicting a result o stability studies on nMag_PAMPS nanoparticles. Figure 16 depicts TEM images of nMagJPAMPS nanoparticles.

Figure 17 depicts a schematic diagram of subsurface oil detection by nanoreporters.

While the present disclosure is susceptible to various modifications and alternative forms, specific example embodiments have been shown in the figures and are herein described in more detail. It should be understood, however, that the description of specific example embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, this disclosure is to cover all modifications and equivalents as illustrated, in part, by the appended claims.

DESCRIPTION

The present disclosure generally relates to nanomaterials. More particularly, the present disclosure relates to surface-modified nanomaterials that are suitable for use in high salinity environments.

The surface-modified nanomaterials of the present disclosure may be useful in applications such as, among other things, sensors to provide improved information about water or oil and gas reservoirs. For example, the surface-modified nanomaterials of the present disclosure may be used as nanotracers, providing the ability for near borehole sensing and/or contrast for remote sensing.

In general, the surface-modified nanomaterials of the present disclosure may comprise a nanomaterial and an amphiphilic copolymer. Aqueous solutions (e.g., ionic strength) strongly influence nanomaterial aggregation and transport through porous media. Accordingly, the present disclosure contemplates modifying a nanomaterial 's surface charge and/or coating of nanomaterials to, among other things, control attachment, detachment, and partitioning behavior. Thus, an advantage of the surface-modified nanomaterials disclosed herein is that these materials may be stable under highly saline conditions, exhibit good transport characteristics, and may be less prone to aggregate and/or precipitate.

In some embodiments, the surface-modified nanomaterials may have at least one dimension that measures less than 1,000 nm in size. In some embodiments, the surface- modified nanomaterials may have a particle size of 1-500 nm. In other embodiments, the surface-modified nanomaterials may have a particle size of 10-100 nm. Still in other embodiments, the surface-modified nanomaterials may have a particle size of 20 to 50 nm.

Nanomaterials suitable for use in the surface-modified nanomaterials of the present disclosure may comprise any nanomaterial suitable for use in subterranean formations. For example, the nanomaterial may be a nano-magnetite material (nMag) or a quantum dot material (QD). Suitable quantum dot materials may include cadmium selenide materials, cadmium zinc sulfide materials, or a combination thereof. Suitable nano-magnetite materials include Fe₃0₄ and iron oxide nanocrystals.

In some embodiments, an amphiphilic copolymer may be used to modify or at least partially coat the surface of the nanomaterial. In some embodiments, the amphiphilic copolymer may be used to completely coat the surface of the nanomaterial. In some applications, such as in oil field applications, the surface of the nanomaterial may be modified or coated with the amphiphilic polymer to an extent that the modified nanomaterial is be capable of withstanding hostile environments (e.g., offer thermal and/or hydrolytic stability, and a resistance to hard water containing metal ions). In other applications, such as in water treatment processes, the surface of the nanomaterial may be modified or coated with the amphiphilic polymer to an extent that the amphiphilic polymer coating provides cation stability (e.g., inhibit calcium, magnesium, and silica scale, as well as control corrosion by, for example, dispersing iron oxide) or may be used to precipitate solids (e.g., in the treatment of industrial effluent streams).

In some embodiments, the amphiphilic copolymer may comprise a polymer of 2- acrylamido-2-methylpropane sulfonic acid (AMPS), poly- AMPS (PAMPS), 2-acrylamido-2- methylpropane sulfonic acid-co-lauryl acrylate (P AMPS-LA), or a copolymer thereof. AMPS is a reactive, hydrophilic, sulfonic acid acrylic monomer capable of importing a number of distinct high-performance characteristics to a wide variety of anionic polymers. The geminal dimethyl group and the sulfomethyl group of AMPS may combine to sterically hinder the amide functionality and provide both hydrolytic and thermal stability to AMPS-containing polymers. The sulfonate group gives the monomer a high degree of hydrophilicity and anionic character at a wide pH range. In addition, AMPS readily absorbs water and also imparts enhanced water absorption and transport characteristics to polymers. AMPS is very soluble in water and dimethylformamide (DMF) and also shows limited solubility in most polar organic solvents. The sulfonic acid group in AMPS is a very strong ionic group and ionizes completely in aqueous solutions. In applications where the precipitation of mineral salts is undesirable, the incorporation of a polymer containing even a small quantity of AMPS can significantly inhibit the precipitation of divalent cations. The result is a significant reduction in the precipitation of a wide variety of mineral salts, including calcium, magnesium, iron, aluminum, zinc, barium, and chromium. AMPS is potentially useful in, among other things, oil field applications and in water treatment applications.

For example, in drilling operations with high salinity, high temperature, and high pressure conditions, AMPS copolymers can inhibit fluid loss and be used in oil field environments as scale inhibitors, friction reducers, and water control polymers, and also can be used in polymer flooding applications. The cation stability of the AMPS-containing polymers is also very useful for water treatment processes. Such polymers with low molecular weights cannot only inhibit calcium, magnesium, and silica scale in cooling towers and boilers, but also can help corrosion control by dispersing iron oxide. When high molecular weight polymers are used, they can be used to precipitate solids in the treatment of industrial effluent stream.

In some embodiments, the amphiphilic copolymer may comprise polyarylic acid (PAA) or a copolymer thereof, poly(maleic anhydride-octadecene)-poly(ethylene glycol) (PMAO-PEG), poly(acrylic acid)-octylamine, poly(ethylene glycol) (PEG), or poly(maleic anhydride-octadecene) (PMAO). In some embodiments, the polymers or copolymers may further comprise multifunctional copolymer materials such as acrylic acid, acryl-PEG, acrylate, and acrylamide.

In some embodiments, a graphite layer may be added to the surface of the nanomaterial or the surface of the surface-modified nanomaterial.

In some embodiments, the present disclosure provides a treatment fluid comprising the surface-modified nanomaterial.

In one or more embodiments, the amphiphilic copolymer material may first be synthesized and then utilized to modify the surface of the nanomaterial. In an embodiment, the present disclosure provides a method comprising synthesizing a unique type of amphiphilic copolymer materials that contains 2-acrylamido-2-methylpropane sulfonic acid (AMPS) blocks and modifying the surface of a nanomaterial with the as-synthesized copolymer.

Figure 1 depicts an embodiment of the first step of this method. As can be seen in Figure 1 , AMPS may be polymerized to form PAMPS or, alternatively, AMPS may be copolymerized with lauryl acrylate to form PAMPS-LA. Figure 2 depicts the structure of PAMPS-LA. As can be seen in Figure 2, PAMPS-LA has both hydrophobic portions and hydrophilic portions, and may further comprise multifunctional copolymer materials, such as acrylic acid, acryl-PEG, acrylate, or acrylamide.

Figure 3 depicts an embodiment of the second step of the method described above. As shown in Figure 3, PAMPS-LA can be used to modify the surface of a quantum dot material to form a water-soluble nanoparticle with a PAMPS coating.

Figure 4 depicts an effect of salt concentration on the size of quantum dot nanoparticles coated with PAMPS (QD_PAMPS). As can be seen in Figure 4, the particle size of QD_PAMPS did not change significantly in solutions with high concentrations of salts. At higher concentrations, particle size was not detectable, however there was still no visible nanoparticle precipitation. Figure 5 depicts an effect of salt concentration on the size of gold nanoparticles. As can be seen in Figure 5, only at salt concentrations of 50 mM and 250 mM was there any significant increase in particle size after each nanoparticle solution was incubated in the NaCl solution. It is believed that a lack of a PAMPS coating on the gold nanoparticles results in their substantial size increase in even very low NaCl or CaCl₂ solutions.

Figure 6 shows results of colloidal stability tests of quantum dot materials coated with PAA (QD PAA) and QD PAMPS. Containers marked A contain water, containers marked B contain 8 wt% NaCl solutions, and containers marked C contain brine solutions of 8 wt% NaCl and 2 wt% CaCl₂. It can be seen from Figure 6, in containers C, the QD_PAMPS are much more stable than the QD_PAA in high saline conditions.

Figure 7 shows results of the addition of CaCl₂ solutions to QD PAA. As can be seen in Figure 7, nanoparticles with carboxylic acid groups such as PAA are easily aggregated in Ca solutions. Visible precipitations can be seen in the containers with CaCl₂ concentrations greater than 0.05 wt% CaCl₂.

Figure 8 shows results of a test comparing an effect of changes in pH on nanoparticle size of QD_PAMPS. As can be seen in Figure 8, changes in pH level does not have a substantial effect on the size of QD PAMPS nanoparticles.

Figure 9 shows the TEM images of the QD_PAMPS nanoparticles of Figure 8.

Figure 10 depicts an effect of salt and pH on nano-n agnetite particle size. As can be seen by Figure 10, salt concentration and changes in pH levels have little effect on the size of nano-magnetite particles of the present invention.

Figure 1 1 shows photographs of nMag_PAA and nMag_PAMPS in solutions of CaCl₂. As can bee seen in Figure 1 1 , PAMPS coated nMag particles are much more stable than PAA-coated nMag particles at high saline conditions. Figure 1 1 also shows a TEM images of nMag_PAMPS nanoparticles and a high resolution TEM images of one nanocrystal.

Figure 12 depicts a result of stability studies of nMag_PAMPS in a brine solution. As can be seen in Figure 12, nMag_PAMPS was stable in a brine solution at room temperature for at least up to 12 months.

Figure 13 shows photographs demonstrating the stability of nMag_PAMPS nanoparticles. As can be seen in Figure 13, the nMag_PAMPS in brine solution remained clear for at least up to 12 months.

Figure 14 depicts results of stability studies of nMag_PAMPS. As can be seen in Figure 14, nMag-PAMPS are stable at 90°C in Dl-water and are stable in brine with an additional graphite layer on the surface of the nano-magnetite particles. Figure 15 depicts results of stability studies of nMag_PAMPS. As can be seen in Figure 15, the nMag PAMPS nanoparticles are stable in a brine solution at 90°C for at least up to 30 days.

Figure 16 shows the TEM images of the nMag_PAMPS nanoparticles of Figure 16. Therefore, it can be seen that such modified nanomaterials are stable under high saline conditions, especially multivalent ions, which have great potential for oilfield and water- treatment applications. Due to the unique property of AMPS material, the AMPS polymer coated nanomaterials are very stable under high saline conditions.

In certain embodiments, the modified nanomaterials described herein may be used in a number of subterranean operations. For example, in certain embodiments, a treatment fluid comprising the modified nanomaterials may be introduced into a subterranean formation. In certain embodiments, the modified nanomaterials discuss herein may also be used in drilling fluids and in situ modification of oil detecting and oil activating particles.

In certain embodiments, the modified nanomaterials described herein may be used as nanoreporters. Figure 17 depicts a schematic diagram of subsurface oil detection by nanoreporters. Nanoreporters may be used to transport probe molecules through subterranean formations followed by selectively releasing them when the nanoreporters contact oil. The more oil the nanoreporters contact, the more probe molecules are released from the nanoreporter. The nanoreporters may then be recovered from the subterranean formation. Interrogation of the recovered nanoreporters may yield quantitative information of the oil content of the subterranean formation based upon the number of probe molecules remaining on the nanoreporter. In order for a nanomaterial to function as an effective nanoreporter, it should be stable in the subterranean conditions. As such, the modified nanomaterials described herein may be used as effective nanoreporters to trasnport probe molecules in highly saline subterranean formations.

In one embodiment, the present disclosure provides a method comprising: providing a nanoreporter comprising a surface-modified nanomaterial and a plurality probe molecules; introducing the nanoreporter into a subterranean formation; recovering the nanoreporter from the subterranean formation.

In other embodiments, the modified nanomaterials described herein may be used for imaging geological structures. U.S. Patent Application Publication No. 2009/0179649, which is herein incoiporated by reference in its entirety, describes methods for magnetic imaging of geological structures. In one embodiment, the present disclosure provides a method comprising: providing a surface-modified nanomaterial comprising a nano-magnetite material; introducing the surface- modified nanomaterial into a subterranean formation; inducing a magnetic signal in proximity to the subterranean formation; and detecting a magnetic signal from the surface-modified nanomaterial.

To facilitate a better understanding of the present invention, the following examples of certain aspects of some embodiments are given. In no way should the following examples be read to limit, or define, the entire scope of the invention.

EXAMPLES

Chemicals:

2-acrylamido-2-methylpropane sulfonic acid (AMPS) (Aldrich), Lauryl acrylate (Aldrich), poly(ethylene glycol) methacrylate (Aldrich), DMF (Aldrich), Darocur 1173 (Ciba). Synthesis of AMPS containing amphiphilic copolymers:

Three grams of AMPS were dissolved in 30 mL of DMF with stirring, followed with the addition of 2.25 mL of lauryl acrylate and 0.3 mL of D1173. The mixture was photopolymerized in a UV radiator with stirring for one hour. UVA (360 nm) was used for the polymerization. Poly(ethylene glycol) acrylate or other monomers may be added and various amphiphilic copolymers can be obtained.

Coating of nanomaterials with AMPS copolymer:

The as-synthesized polymer may be used directly to modify nanomaterials such as quantum dots or iron oxide nanocrystals (nMag). In an experiment, one mL of purified nMag/hexane solution was air dried and followed with the addition of five mL of ethyl ether. One mL of the AMPS copolymer was then added to the nMag/ether solution with stirring. Three to four mL of DMF was further added until the mixture solution become clear. 20-25 mL Dl-water was then added and the mixture was sonicated for one to two minutes using a probe sonicator. After that, the mixture was stirred overnight to allow the complete evaporation of ether. The resulted solution was passed through a 0.45 μιτι syringe filter and a stirred cell was used to remove most of the DMF. Ultracentrifugation was applied to remove excess polymer at 25,000 rpm for two hours. The nMag pellet was re-dispersed and stored in Dl-water or buffer solution.

Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. While numerous changes may be made by those skilled in the art, such changes are encompassed within the spirit of this invention as illustrated, in part, by the appended claims. Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention. While compositions and methods are described in terms of "comprising," "containing," or "including" various components or steps, the compositions and methods can also "consist essentially of or "consist of the various components and steps. All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, "from about a to about b," or, equivalently, "from approximately a to b," or, equivalently, "from approximately a-b") disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles "a" or "an," as used in the claims, are defined herein to mean one or more than one of the element that it introduces. If there is any conflict in the usages of a word or term in this specification and one or more patent or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted.

Claims

What is claimed is:

1. A method comprising:

providing an amphiphilic copolymer;

providing a nanomaterial; and

modifying the surface of the nanomaterial with the amphiphilic copolymer.

2. The method of claim 1 wherein the surface of the nanomaterial is modified with the amphiphilic copolymer to an extent that the stability of the nanomaterial in highly saline environments is increased.

3. The method of claim 1 wherein the amphiphilic copolymer comprises 2- acrylamido-2-methylpropane sulfonic acid-co-lauryl acrylate or a polymer of 2-acrylamide-2- methylpropane sulfonic acid.

4. The method of claim 1 wherein the amphiphilic copolymer comprises polyacrylic acid, poly(maleic anhydride-octadecene)-poly(ethylene glycol), poly(acrylic acid)-octylamine, poly(ethylene glycol), or poly(maleic anhydride-octadecene).

5. The method of claim 1 wherein the nanomaterial comprises a nano-magnetite material.

6. The method of claim 5 wherein the nano-magnetite material comprises Fe₃0₄ or iron oxide nanocrystals.

7. The method of claim 1 wherein the nanomaterial comprises a quantum dot material.

8. The method of claim 7 wherein the quantum dot material comprises a cadmium selenide material, a cadmium zinc sulfide material, or a combination thereof.

9. The method of claim 1 wherein the nanomaterial has a particle size of 10-100 nm.

10. The method of claim 1 further comprising adding a graphite layer to the surface of the nanomaterial.

1 1. A composition comprising a nanomaterial having a surface modified with an amphiphilic copolymer.

12. The composition of claim 1 1 wherein the surface of the nanomaterial is modified with the amphiphilic copolymer to an extent that the stability of the nanomaterial in highly saline environments is increased.

13. The composition of claim 11 wherein the amphiphilic copolymer comprises 2- acrylamido-2-methylpropane sulfonic acid-co-lauryl acrylate or a polymer of 2-acrylamide-2- methylpropane sulfonic acid.

14. The composition of claim 11 wherein the amphiphilic copolymer comprises polyacrylic acid, poly(maleic anhydride-octadecene)-poly(ethylene glycol), poly(acrylic acid)- octylamine, poly(ethylene glycol), or poly(maleic anhydride-octadecene).

15. The composition of claim 11 wherein the nanomaterial comprises a nano- magnetite material.

16. The composition of claim 15 wherein the nano-magnetite material comprises Fe₃0₄ or iron oxide nanocrystals.

17. The composition of claim 11 wherein the nanomaterial comprises a quantum dot material.

18. The composition of claim 17 wherein the quantum dot material comprises a cadmium selenide material, a cadmium zinc sulfide material, or a combination thereof.

19. The nanomaterial of claim 11 wherein the nanomaterial has a particle size of 10-

100 nm.

20. A treatment fluid comprising a nanomaterial wherein a surface of the nanomaterial has been modified with an amphiphilic copolymer.

21. The treatment fluid of claim 18, wherein the nanomaterial comprises a nano- magnetite material or a quantum dot material.

22. The treatment fluid of claim 18, wherein the amphiphilic copolymer comprises 2- acrylamido-2-methylpropane sulfonic acid-co-lauryl acrylate or a polymer of 2-acrylamide-2- methylpropane sulfonic acid.

23. A method comprising: providing a composition according to any one of claims 1 1 -19 and introducing the nanomaterial into a environment having highly saline conditions.