A nanofluid, its preparation method and use
By using nanofluids composed of modified nanoparticles, surfactants, and polymers, the stability and asphaltene deposition problems of CO2 foam displacing agents in oilfield extraction were solved, achieving efficient oil recovery and increased permeability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XINJIANG ZHUNENG CHEMICAL CO LTD
- Filing Date
- 2026-04-03
- Publication Date
- 2026-06-02
AI Technical Summary
Existing CO2 foam displacement agents suffer from poor stability and severe asphalt deposition in oilfield operations, affecting recovery rates and equipment stability.
Nanofluids composed of modified nanoparticles, surfactants, and polymers are prepared through ultrasonic treatment and mixing reaction. These nanofluids combine with CO2 foam to form stable C/W foams, enhancing interfacial stability and shear resistance, and inhibiting asphalt deposition.
It significantly improved the stability and oil recovery of foam displacement agents, reduced asphaltene deposition, and enhanced permeability and oil fluidity after displacement.
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Abstract
Description
Technical Field
[0001] This application relates to the field of nanofluid technology, and in particular to a nanofluid, its preparation method, and its application. Background Technology
[0002] CO2 displacement agents can effectively improve oil recovery by reducing crude oil viscosity, lowering oil-water interfacial tension, promoting crude oil expansion, and altering wall wettability. However, the density difference between CO2 and crude oil can easily lead to gravity segregation, and the high fluidity of CO2 can cause gas channeling and viscosity finger phenomena. More seriously, direct contact between carbon dioxide and oil can lead to the deposition of large amounts of asphaltene, damaging reservoir connectivity and the stability of extraction equipment.
[0003] Carbon dioxide in water (C / W) foam flooding is an effective method to alleviate the aforementioned problems. The chemicals in the foam reduce the interfacial tension between oil and water, effectively stripping oil films from the rock surface. Furthermore, the Jamin effect allows the foam to block high-permeability layers or large channels in porous media, thereby improving sweep efficiency and overall oil recovery. However, the tightly packed polyhedral structure of C / W foam makes it thermodynamically unstable and prone to rapid coarsening through drainage, Ostwald ripening, and coalescence. Therefore, developing stable CO2 foam is a prerequisite for its practical application.
[0004] Therefore, developing nanofluids that can simultaneously enhance the stability of C / W foam displacing agents and inhibit asphaltene deposition is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention
[0005] In view of this, this application provides a nanofluid that simultaneously enhances the stability of foam displacing agents and inhibits asphalt deposition, exhibiting good comprehensive performance.
[0006] This application provides a nanofluid comprising, by mass fraction: 0.01% to 0.7% modified nanoparticles, 1% to 4% surfactant, 0.2% to 0.6% polymer and 0.01% to 0.2% short-chain alkanes, with the balance being water.
[0007] In some specific implementations, the modified nanoparticles include silica nanoparticles modified with silane coupling agents; The modified nanoparticles have a particle size of 20 nm to 50 nm; Silane coupling agents include triethoxy(3-epoxypropyloxypropyl)silane.
[0008] In some specific implementations, the surfactants include lauramidopropyl betaine and / or cocamidopropyl hydroxysulfonate betaine; Polymers include cationic polyacrylamide; Short-chain alkanes include propane and / or n-butane.
[0009] This application also provides a method for preparing the nanofluid as described above, comprising: Nanofluids are obtained by ultrasonic treatment of a mixture of modified nanoparticles, surfactants, polymers and short-chain alkanes.
[0010] In some specific implementations, the preparation methods of the above-mentioned modified nanoparticles include: The nanoparticles were mixed with a silane coupling agent and subjected to a reaction and a ring-opening reaction in sequence to obtain modified nanoparticles.
[0011] In some specific implementations, the reaction is carried out at a pH of 9 to 11, at a temperature of 100°C to 120°C, and for a time of 4 to 5 hours. The mass ratio of the nanoparticles to the silane coupling agent is 2:(0.5-1.5).
[0012] In some specific implementations, a preliminary product is obtained after the reaction. The preliminary product is mixed with an acid solution to undergo a ring-opening reaction to obtain modified nanoparticles. The volume ratio of the preliminary product to the acid solution is 1:(6-8). After the ring-opening reaction, an alkaline solution is added to adjust the pH to 7-8, followed by centrifugation, filtration, and drying. The acid solution includes hydrochloric acid and / or sulfuric acid, and the mass fraction of the acid solution is 40% to 50%.
[0013] This application also provides a CO2 foam displacing agent, comprising the nanofluid and carbon dioxide as described above.
[0014] This application also provides a method for preparing the CO2 foam displacing agent as described above, comprising: Nanofluids are mixed with carbon dioxide to obtain CO2 foam displacing agents; The volume ratio of nanofluid to carbon dioxide is 1:(3-5); Mixing is carried out under stirring; The stirring temperature is 20℃ to 30℃; The stirring speed is 800 rpm to 1200 rpm; The stirring time is 20 to 40 minutes; The pressure during stirring is 8 MPa to 12 MPa.
[0015] This application also provides the application of the CO2 foam displacement agent as described above in core flooding.
[0016] The nanofluid provided in this application utilizes a multi-component composite synergistic effect. Surfactants reduce the interfacial tension between the two phases to generate dense, high-inward C / W foam. Polymers increase the viscosity of the liquid phase to mitigate the drainage effect. Nanoparticles significantly enhance surface energy and interfacial strength through stable adsorption at the interface to prevent foam rupture. Furthermore, adsorption of asphaltenes reduces asphaltenes deposition, thereby significantly improving C / W foam stability and increasing oil recovery. Foam displacing agents prepared using nanofluids can improve permeability and asphaltenes content after displacing, exhibiting good comprehensive performance. Detailed Implementation
[0017] It should be understood that the expression “one or more of…” individually includes each of the objects described after the expression, as well as various different combinations of two or more of the described objects, unless otherwise understood from the context and usage. The expression “and / or” combined with three or more described objects should be understood to have the same meaning, unless otherwise understood from the context.
[0018] The terms “including,” “having,” or “containing,” including the use of their grammatical synonyms, should generally be understood as open-ended and non-restrictive, for example, not excluding other unstated elements or steps, unless otherwise specifically stated or understood from the context.
[0019] It should be understood that the order of steps or the sequence of actions is not important as long as this application remains operational. Furthermore, two or more steps or actions may be performed simultaneously.
[0020] The use of any and all instances or exemplary language such as “e.g.” or “include” in this document is intended merely to better illustrate the application and does not constitute a limitation on the scope of the application. No language in this specification should be construed as indicating that any unclaimed element is essential to the practice of this application.
[0021] Furthermore, the numerical ranges and parameters used to define this application are approximate values, and the relevant values in the specific embodiments have been presented as precisely as possible. However, any numerical value inevitably contains standard deviations due to individual test methods. Therefore, unless otherwise explicitly stated, it should be understood that all ranges, quantities, values, and percentages used in this disclosure are modified with the word "approximately." Here, "approximately" generally means that the actual value is within plus or minus 10%, 5%, 1%, or 0.5% of a specific value or range.
[0022] Nanoparticles possess high adsorption energy at the two-phase interface, enabling the formation of a highly elastic gas-water interface. They inhibit bubble coalescence by modulating inter-bubble interactions, thereby enhancing foam stability and shear resistance. Furthermore, nanoparticles, through their high adsorption capacity, can rapidly attract asphaltenes particles, inhibiting asphaltenes deposition and improving petroleum fluidity.
[0023] This application provides a nanofluid comprising, by mass fraction: 0.01% to 0.7% modified nanoparticles, 1% to 4% surfactant, 0.2% to 0.6% polymer and 0.01% to 0.2% short-chain alkanes, with the balance being water.
[0024] The nanofluid described in this application includes modified nanoparticles. In some specific implementations, the modified nanoparticles include silica nanoparticles modified with a silane coupling agent; the silane coupling agent includes triethoxy(3-epoxypropyloxypropyl)silane. The particle size of the modified nanoparticles is 20 nm to 50 nm, preferably 25 nm to 45 nm, more preferably 30 nm; the mass fraction of the modified nanoparticles is 0.01% to 0.7%, and can be 0.01%, 0.02%, 0.03%, 0.05%, 0.06%, 0.08%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, preferably 0.03% to 0.08%. Modified nanoparticles have high adsorption energy at the two-phase interface, which can form a highly elastic gas-water interface and inhibit bubble coalescence by regulating the interaction between bubbles, thereby enhancing the stability and shear resistance of the foam.
[0025] The nanofluids described in this application include surfactants. In some specific implementations, the surfactants include lauramidopropyl betaine and / or cocamidopropyl hydroxysulfonate betaine. The mass fraction of the surfactant is 1% to 4%, and can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, or 4%, preferably 2% to 3.5%.
[0026] The nanofluids described in this application include polymers. In some specific implementations, the polymer includes cationic polyacrylamide. The mass fraction of the polymer is 0.2% to 0.6%, and can be 0.2%, 0.3%, 0.4%, 0.5%, or 0.6%, preferably 0.4% to 0.6%.
[0027] The nanofluids described in this application include short-chain alkanes. In some specific implementations, the short-chain alkanes include, but are not limited to, propane and / or n-butane. This application does not have specific requirements for the selection of short-chain alkanes. The mass fraction of the short-chain alkanes is 0.01% to 0.2%, and can be 0.01%, 0.05%, 0.1%, 0.15%, or 0.2%, preferably 0.01% to 0.05%.
[0028] Nanofluids can significantly improve the stability of C / W foams.
[0029] This application also provides a method for preparing the above-mentioned nanofluid, comprising: Nanofluids are obtained by ultrasonic treatment of a mixture of modified nanoparticles, surfactants, polymers and short-chain alkanes.
[0030] This application first dissolves nanoparticles in deionized water, then uses a pulsed ultrasonic cell disruptor to sonicate the uniformly dispersed nanoparticles. Next, the uniformly dispersed nanoparticles are mixed and reacted with a silane coupling agent to obtain modified nanoparticles. In some specific implementations, the mass of the nanoparticles is 1g to 3g, preferably 2g, corresponding to a volume of deionized water of 80mL to 120mL, preferably 100mL. The mixing includes ultrasonic treatment with a power of 400W to 600W, preferably 500W, for a duration of 20min to 40min, preferably 20min. In some specific implementations, the reaction is carried out at a pH of 9 to 11, preferably 10, at a temperature of 100℃ to 120℃, preferably 110℃, and for a reaction time of 4h to 5h. In some specific implementations, the reaction is carried out under an inert gas protection environment, including but not limited to nitrogen. The reaction is initiated after purging with nitrogen for 20 to 40 minutes. Following the reaction, the nanoparticles are purified three times with anhydrous ethanol and dried at 30°C to 40°C for 20 to 40 hours. In some specific implementations, the mass ratio of the nanoparticles to the silane coupling agent is 2:(0.5-1.5), which can be 2:0.5, 2:0.6, 2:0.8, 2:1, 2:1.1, 2:1.2, 2:1.4, or 2:1.5. In some specific implementations, a preliminary product is obtained after the reaction. This preliminary product is mixed with an acid solution for a ring-opening reaction to obtain modified nanoparticles. The volume ratio of the preliminary product to the acid solution is 1:(6-8), preferably 1:7. After the ring-opening reaction, an alkaline solution is added to adjust the pH to 7-8, followed by centrifugation, filtration, and drying. In some specific implementations, the acid solution includes, but is not limited to, hydrochloric acid and / or sulfuric acid, and the mass fraction of the acid solution is 40% to 50%, preferably 45%; the alkaline solution includes, but is not limited to, sodium hydroxide solution, and the concentration of the sodium hydroxide solution is 0.05 g / mL to 0.15 g / mL, preferably 0.1 g / mL. In some specific implementations, the ring-opening reaction is carried out under stirring, and the stirring time is 2 min to 10 min, preferably 3 min to 8 min, more preferably 5 min.
[0031] This application also provides a CO2 foam displacing agent, comprising the nanofluid and carbon dioxide as described above.
[0032] In some specific implementations, the volume ratio of the nanofluid to carbon dioxide is 1:(3-5), preferably 1:4, that is, the volume of the nanofluid is 20v / v%, and the volume of CO2 is 80v / v.
[0033] This application also provides a method for preparing the CO2 foam displacing agent as described above, comprising: Nanofluids are mixed with carbon dioxide to obtain CO2 foam displacing agents.
[0034] In some specific implementations, the mixing is carried out under stirring; the stirring speed is 800 rpm to 1200 rpm, preferably 1000 rpm; the stirring time is 20 min to 40 min, preferably 30 min; the stirring temperature is 20°C to 30°C; the stirring pressure is 8 MPa to 12 MPa, preferably 10 MPa; and carbon dioxide is introduced to 10 MPa and stirred to obtain a CO2 foam displacing agent.
[0035] This application also provides the application of the above-mentioned CO2 foam displacement agent in core flooding to improve oil recovery, inhibit asphalt deposition, and avoid formation channel blockage.
[0036] The present application is further illustrated below with reference to embodiments. The scope of protection of the present application is not limited to the following embodiments.
[0037] Example 1
[0038] This embodiment provides a nanofluid, the preparation method of which includes: (1) Add 2g of SiO2 nanoparticles and 100mL of deionized water to a beaker, and use a pulsed ultrasonic cell disruptor at 500W power for 30 minutes to uniformly disperse the nanoparticles. Add 0.5g of GPTES silane coupling agent, stir evenly, and then add 0.1g / mL NaOH solution to adjust the pH to 10 to obtain solution A.
[0039] (2) Add solution A to the flask and purge with nitrogen for 30 min to remove oxygen. Maintain nitrogen protection, control the reaction temperature at 110℃ and the stirring speed at 300 r / min, and react for 4-5 hours under nitrogen protection and reflux. After the reaction is complete, remove impurities by centrifugation and purification with anhydrous ethanol three times. Dry the sample at 35℃ for 24 hours to obtain the preliminary product powder.
[0040] (3) Dissolve the initial product powder in acid solution at a volume ratio of 1:7, open the epoxy functional group, stir for 5 min, add alkaline solution to adjust pH to 7-8, centrifuge at 12000 rpm for 20 min, filter and dry at 80℃ for 24 h to obtain modified SiO2 nanoparticles with a particle size distribution of 20-50 nm.
[0041] (4) Dissolve 0.1% modified SiO2 nanoparticles in 10g of deionized water and use a pulsed ultrasonic cell disruptor at 500W power for 30 minutes to uniformly disperse the nanoparticles; at the same time, add 3% cocamidopropyl hydroxysulfonate betaine, 0.6% cationic polyacrylamide and 0.01% propane, stir evenly and the nanofluid is obtained.
[0042] Example 2
[0043] This embodiment provides a nanofluid, which differs from Embodiment 1 only in that the concentration of modified SiO2 nanoparticles is 0.05%.
[0044] Example 3
[0045] This embodiment provides a nanofluid, which differs from Example 1 only in that the amount of GPTES silane coupling agent added is 1.5g and the concentration of modified SiO2 nanoparticles is 0.1%.
[0046] Example 4
[0047] This embodiment provides a nanofluid, which differs from Embodiment 1 in that: the amount of GPTES silane coupling agent added is 1.5g, the concentration of modified SiO2 nanoparticles is 0.1%, and propane is replaced with n-butane.
[0048] Example 5
[0049] This embodiment provides a nanofluid, which differs from Embodiment 1 in that: the amount of GPTES silane coupling agent added is 1.5g, the concentration of modified SiO2 nanoparticles is 0.5%, and propane is replaced with n-butane.
[0050] Example 6
[0051] This embodiment provides a nanofluid, which differs from Embodiment 1 in that: the amount of GPTES silane coupling agent added is 1.5g, the concentration of modified SiO2 nanoparticles is 0.7%, and propane is replaced with n-butane.
[0052] Comparative Example 1
[0053] This comparative example provides a displacement fluid comprising carbon dioxide.
[0054] Comparative Example 2
[0055] This comparative example provides a foaming fluid comprising cocamidopropyl hydroxysulfonate betaine.
[0056] Comparative Example 3
[0057] This comparative example provides a foaming fluid that differs from Example 1 in that it does not contain modified nanoparticles and propane, and replaces cocamidopropyl hydroxysulfonate with lauramide propyl betaine.
[0058] Comparative Example 4
[0059] This comparative example provides a nanofluid, which differs from Example 1 in that it does not contain modified nanoparticles and propane.
[0060] Comparative Example 5
[0061] This comparative example provides a nanofluid that differs from Example 1 in that it does not contain propane, replaces the modified nanoparticles with unmodified nanoparticles, and does not contain propane.
[0062] Comparative Example 6
[0063] This comparative example provides a nanofluid, which differs from Example 2 in that the nanoparticles are not modified.
[0064] Comparative Example 7
[0065] This comparative example provides a nanofluid, which differs from Example 6 in that the nanoparticles are not modified.
[0066] CO2 foam displacing agent stability test: The pre-prepared nanofluid was placed in an emulsification vessel at a ratio of 0.8 (foam displacing agent by mass). CO2 was introduced into the emulsification vessel at 10 MPa, and the mixture was stirred at 1000 rpm for 30 min to obtain the specified foam displacing agent. The stability of the foam displacing agent was observed through the sapphire window of the emulsification vessel. When fine pores appeared in the foam displacing agent, it was considered to be in an unstable state, and the stabilization time was recorded.
[0067] Displacement experimental materials: Core permeability 557 mD, porosity 26.3; Petroleum 410 mPa·s asphaltene content 10.29, temperature 25℃.
[0068] Oil displacement test: A core sample with a permeability of 557 mDa, a porosity of 26.3%, and an oil content of 9.22% (410 mPa·s) was saturated and placed in a core holder. A confining pressure of 16 MPa was set on the outer ring to simulate formation pressure. After connecting all pipelines, a tail pressure of 10 MPa was set at the end of the displacement path to maintain a constant system pressure. Displacement was initiated using a foam displacement agent prepared with nanofluids. Displacement was stopped when the average water content of the outlet liquid exceeded 98%, and the oil recovery rate was calculated.
[0069] After the core flooding experiment was completed, the core was cleaned using the n-heptane Soxhlet extraction method, and the core permeability was determined using Darcy's law.
[0070] The extracted petroleum was added to a TLC-FID instrument to analyze the oil sample composition. During the experiment, the scanning speed was 30 s / time, the air flow rate was 2000 mL / min, and the hydrogen flow rate was 160 mL / min. The asphaltene content was measured.
[0071] The test results are shown in Table 1.
[0072] Table 1
[0073] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and application concept of this application, should be included within the scope of protection of this application.
Claims
1. A nanofluid, characterized in that, It comprises, by mass fraction: 0.01% to 0.7% modified nanoparticles, 1% to 4% surfactant, 0.2% to 0.6% polymer and 0.01% to 0.2% short-chain alkanes, with the balance being water.
2. The nanofluid according to claim 1, characterized in that, The modified nanoparticles include silica nanoparticles modified with silane coupling agents. The modified nanoparticles have a particle size of 20 nm to 50 nm; The silane coupling agent includes triethoxy(3-epoxypropyloxypropyl)silane.
3. The nanofluid according to claim 1, characterized in that, The surfactants include lauramidopropyl betaine and / or cocamidopropyl hydroxysulfonate betaine; The polymer includes cationic polyacrylamide; The short-chain alkanes include propane and / or n-butane.
4. A method for preparing a nanofluid as described in any one of claims 1 to 3, characterized in that, include: Nanofluids are obtained by ultrasonic treatment of a mixture of modified nanoparticles, surfactants, polymers and short-chain alkanes.
5. The preparation method according to claim 4, characterized in that, The method for preparing the modified nanoparticles includes: The nanoparticles were mixed with a silane coupling agent and subjected to a reaction and a ring-opening reaction in sequence to obtain modified nanoparticles.
6. The preparation method according to claim 5, characterized in that, The reaction is carried out at a pH of 9 to 11, at a temperature of 100°C to 120°C, and for a time of 4 to 5 hours. The mass ratio of the nanoparticles to the silane coupling agent is 2:(0.5-1.5).
7. The preparation method according to claim 5, characterized in that, The reaction yields a preliminary product, which is then mixed with an acid solution for a ring-opening reaction to obtain modified nanoparticles. The volume ratio of the preliminary product to the acid solution is 1:(6-8). After the ring-opening reaction, an alkaline solution is added to adjust the pH to 7-8, followed by centrifugation, filtration, and drying. The acid solution includes hydrochloric acid and / or sulfuric acid, and the mass fraction of the acid solution is 40% to 50%.
8. A CO2 foam displacing agent, characterized in that, Includes the nanofluid and carbon dioxide as described in any one of claims 1 to 3.
9. A method for preparing the CO2 foam displacing agent as described in claim 8, characterized in that, include: Nanofluids are mixed with carbon dioxide to obtain CO2 foam displacing agents; The volume ratio of the nanofluid to carbon dioxide is 1:(3-5). The mixing is carried out under stirring; The stirring temperature is 20°C to 30°C; The stirring speed is 800 rpm to 1200 rpm; The stirring time is 20 to 40 minutes; The pressure during stirring is 8 MPa to 12 MPa.
10. The application of the CO2 foam displacement agent as described in claim 8 in core flooding to improve oil recovery and inhibit asphalt deposition to avoid formation channel blockage.