Co2 -responsive polymer for sealing flow paths in co2 storage wellbores and caverns and methods of making

Abstract

CO2-responsive polymer designed to be activated using CO2-sensitive microcapsules for sealing flow paths to improve the integrity of wellbores.

Description

TITLECO2 -Responsive Polymer for Sealing Flow Paths in CO2 Storage Wellbores and Caverns and Methods of MakingRELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 661,037, filed on 17 June 2024, which is incorporated herein in its entirety.BRIEF SUMMARY OF THE INVENTION

[0002] The present invention concerns CO2-responsive polymer designed to be activated using CO2-sensitive microcapsules for sealing flow paths to improve the integrity of wellbores that may leak CO2, including wellbores associated with CO2 storage facilities and wellbores employing CO2 in enhanced oil recovery operations. The microcapsules carry a catalyst / hardener / polymer / other material to enable initiating and / or controlling the polymerization of the polymer being the carrier media or released in another carrier media (e.g., brine) upon the release of their cargo when exposed to a CO2 environment. The technology aims to seal CO2 flow paths in which CO2 is leaking within wellbores by activating the CO2 -responsive polymer in flow paths with significant CO2 leakage beyond a predetermined threshold.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0003] Figure 1 shows microfluidic fabricated microcapsules adapted to release their cargo upon reduction of the surrounding water fluid pH from 9 to pH=5 by either to rupturing or dissolving or both for an embodiment of the present invention.

[0004] Figure 2 is an optical microscope image of microcapsules encapsulating Polymer hardener in the core for an embodiment of the present invention.

[0005] Figure 3 shows a pressurized CO2 gas chamber system for delivery of CO2 to microcapsule samples wherein upon exposure to CO2 gas, the color of a pH-sensitive dye changes from red to yellow, indicating a reduction in pH from 9 to pH<6 for an embodiment of the present invention.

[0006] Figure 4 are optical micrographs showing (left) microcapsules dispersed in a polymer media pre CO2 exposure (right) the microcapsule shells' rupture upon exposure to a CO2 gas stimulus and subsequently release the hardener cargo to initiate the polymerization process for an embodiment of the present invention.DETAILED DESCRIPTION OF THE INVENTION

[0007] Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting but merely as a representative basis for teaching one skilled in in the art. Further, the terms and phrases used herein are not intended to be limiting but rather to provide an understandable description of the invention.

[0008] In one embodiment, the present invention concerns processes to fabricate polymeric microcapsules using a microfluidic-based approach programmed to encapsulate and release a predetermined material or materials which may include polymer hardeners, catalysts, polymers, nanomaterials, retarders, phase-changing materials, endothermic materials, as well as others known to those of skill in the art upon exposure to CO2 gas. The microcapsules are designed to release encapsulated materials by rupturing, dissolving, or both in the presence of CO2 gas, releasing the material to initiate controlled polymerization of the carrier polymer.

[0009] The synthesis of CO2 -sensitive microcapsules involves using a cationic triblock polymerto create capsule shells. When exposed to a CO2 environment, these shells release the microcapsule cargo by losing their structural integrity by breaking up, rupturing or dissolving. Water-in-oil-in- water double emulsion drops may be prepared using a capillary microfluidic device, creating stable microcapsules that release their cargo when exposed to acidic pH conditions.

[0010] The polymer catalyst / other materials are encapsulated in microcapsules using a microfluidic and or solvent evaporation emulsion fabrication approach. The capsules demonstrated stability at pH ~8 and released their cargo when the pH was dropped to ~5.

[0011] A CO2 chamber system was assembled to expose the microcapsules to CO2. The pH of the aqueous continuous fluid decreased in the presence of CO2, causing the microcapsule shells to dissolve and release the materials, initiating controlled polymerization.

[0012] In one preferred embodiment, the present invention provides engineering and methods of making for producing CO2 -responsive polymer sealant by incorporating the CCh-sensitive microcapsules for sealing applications in CO2 storage wellbores.DETAILED SYNTHESIS AND CHARACTERIZATION:

[0013] The design of CO2 -responsive polymer sealant incorporates the making of CO2 - sensitive microcapsules with cationic triblock polymer shells that become charged and dissolve when the pH of the surrounding environment becomes acidic (pH < 6), a condition occurring when water absorbs CO2 gas in CO2 storage wellbores, caverns, and other CO2 storage facilities. Using a capillary microfluidic device, water-in-oil-in-water (W / O / W) double emulsion drops are prepared as templates; the middle oil phase contains a solution of the pH-sensitive polymer in a solvent mixture, which forms a uniform solid shell upon solvent evaporation into the outer phase. These spherical capsules remain stable at pH ~9 but dissolve and release their cargo when the pH is reduced to a pH of about 5 by adding a small amount of HC1 acid, as depicted in Figure 1.

[0014] To encapsulate the hardening agent, a micro fluidic / solvent evaporation emulsion fabrication approach may be used to create capsules that encapsulate an aqueous cargo of a polymer hardener and a double emulsion stabilizing surfactant, as depicted in Figure 2. Careful microcapsule fabrication can increase the microcapsule survivability ratio to exceed 50% when the hardener / catalyst is included as the cargo material. Standard fabrication protocol will result in some microcapsules rupturing prior to solidification but the survivability ratio can be improved by modulating interior surfactant ratio and type or modulating interior droplet viscosity.

[0015] A pressurized CO2 chamber (Figure 3) system was developed to introduce CO2 to the microcapsule dispersion and lower the pH of the aqueous continuous fluid. This pH reduction is modulated by the pressure of CO2 gas in the chamber, as Henry’s law describes. A pH-sensitive dye added to the water solution demonstrates this effect, changing color from red to yellow as the pH drops from 9 to below 6 upon CO2 exposure.

[0016] Microcapsules encapsulating the hardener / catalyst cargo are exposed to CO2 gas at a pressure of ~2 atm, as depicted in Figure 4. The polymer chains acquire a positive charge due to the local pH change, causing the microcapsule shells to break apart at a constant rate and release the hardener cargo after several minutes, initiating polymerization.

[0017] The microcapsules are dispersed in the parent polymer or polymer resin as the carrier material using standard dispersion methods such as ultrasonication and magnetic stirring. A relatively uniform dispersion of the microcapsules is achieved when the polymer is stirred using standard mixing methods.

[0018] The microcapsules' size and cargo materials weight per microcapsule are designed to have a density lower or similar to the parent / carrier polymer or polymer resin so that the microcapsules will be suspended in the parent / carrier polymer or polymer resin.

[0019] The microcapsule shell thickness is designed and made to provide the necessary shear strength of the capsules to survive the stirring process during dispersion in the parent polymer while allowing the release of microcapsule cargo when exposed to a CO2 environment beyond a specific threshold and in a relatively short exposure time period (e.g., 5-15 minutes).

[0020] The microcapsules encapsulating the hardener / catalyst cargo were dispersed in a parent polymer / polymer resin and were exposed to an aqueous solution, including CO2 gas. The experiment shows the dissolution of the microcapsules and the release of hardener / catalyst. A partial polymerization of the polymer was observed.

[0021] While the foregoing written description enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The disclosure should, therefore, not be limited by the above-described embodiments, methods, and examples but by all embodiments and methods within the scope and spirit of the disclosure.

Claims

WHAT IS CLAIMED IS:

1. A CO2-responsive polymer sealant, for closing a CO2 pathway, comprising: CO2 -sensitive microcapsules adapted release one or more different substances contained in said microcapsules when exposed to CO2.

2. The CCh-responsive polymer sealant of claim wherein said CO2 -sensitive microcapsules dissolve when exposed to CO2.

3. The CCh-responsive polymer sealant of claim wherein said CO2 -sensitive microcapsules rupture when exposed to CO2.

4. The CO2-responsive polymer sealant of claim wherein said CO2 -sensitive microcapsules break apart when exposed to CO2.

5. The CCh-sensitive microcapsule of claim 2, wherein said polymer is a phenol-based polymer.

6. The CCh-sensitive microcapsule of claim 3, wherein said polymer is a phenol-based polymer.

7. The CCh-sensitive microcapsule of claim 4, wherein said polymer is a phenol-based polymer.

8. The CCh-sensitive microcapsule of claim 2, wherein said polymer is a cationic triblock polymer.

9. The CO2-sensitive microcapsule of claim 3, wherein said polymer is a cationic triblock polymer.

10. The CO2-sensitive microcapsule of claim 4, wherein said polymer is a cationic triblock polymer.

11. Microcapsules for delivering one or more materials for sealing CO2 storage wellbores comprising: a. a hollow shell made of a polymer to form a polymer shell; b. one or more materials encapsulated within said polymer shell; and c. said polymer shell adapted to release said one or more materials upon exposure to CO2.

12. The CO2-sensitive microcapsule of claim 11, wherein said polymer shell is made from a phenol-based polymer.

13. The CO2-sensitive microcapsule of claim 11, wherein said polymer shell is made from a cationic triblock polymer.

14. A method for sealing CO2 storage wellbores using CCh-responsive polymers incorporating CO2 -sensitive microcapsules, comprising: a. injecting CO2 -sensitive microcapsules into targeted locations in a wellbore, said microcapsules are polymer shells having one or more materials therein; and b. said polymer shells adapted to release said one or more materials upon exposure to CO2.

15. The method of claim 14 wherein said CO2 -sensitive microcapsules dissolve when exposed to CO2.

16. The method of claim 14 wherein said CO2 -sensitive microcapsules rupture when exposed to CO2.

17. The method of claim 14 wherein said CO2 -sensitive microcapsules break apart when exposed to CO2.

18. The method of claim 14 wherein said polymer is a phenol -based polymer.

19. The method of claim 14 wherein said polymer is a cationic triblock polymer

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