In-situ modified nanoparticle CO2 foam sealing system, preparation method and application

Abstract

This invention discloses an in-situ modified nanoparticle CO2 foam sealing system, which is composed of the following materials: 1-5 wt% nonionic CO2 responsive surfactant; 5-10 wt% nanoparticles; 0.1-1 wt% anionic foaming agent; 1-5 wt% salt ion additive; and the balance is water. This invention discloses a method for preparing the in-situ modified nanoparticle CO2 foam sealing system, which includes the following steps: (1) adding the prescribed amount of nonionic CO2 responsive surfactant and the prescribed amount of anionic foaming agent to the prescribed amount of water, and stirring evenly to obtain a mixture a; (2) adding the prescribed amount of nanoparticles to mixture a, stirring and sonicating until completely dispersed to obtain mixture b; (3) adding mixture b to a high-temperature and high-pressure foam reaction vessel, introducing high-pressure CO2, and stirring to obtain an acidic mixture c; (4) after standing, the in-situ modified nanoparticle CO2 foam sealing system is obtained.

Description

Technical Field

[0001] This invention belongs to the field of petroleum extraction engineering, and relates to the field of CO2 gas channeling prevention in low-permeability oil reservoirs. Specifically, it relates to an in-situ modified nanoparticle CO2 foam sealing system, its preparation method, and its application. Background Technology

[0002] CO2 flooding technology is an effective way to achieve a win-win situation of increased oil production and carbon sequestration. It enables the resource utilization of greenhouse gases and improves oil and gas recovery rates. Chinese invention patent application CN 109973060A discloses an apparatus and method for improving oilfield recovery rates. Applying CO2 flooding technology to tight oil development not only improves the oil displacement effect but also effectively sequesters carbon dioxide underground, reducing the greenhouse gas effect in the atmosphere. Carbon dioxide can reduce crude oil viscosity, improve mobility ratio, and expand swept volume, effectively solving development problems such as insufficient water injection in ultra-low permeability reservoirs, difficulty in establishing effective displacement systems, and water leakage along fractures. Carbon dioxide and underground crude oil are mutually integrated (miscible), characterized by low miscibility pressure and low interfacial tension, increasing oilfield recovery rates by an average of 5%–15% compared to waterflooding, thus improving oil displacement efficiency.

[0003] However, during CO2 gas drive, due to the low density and viscosity of the gas, as well as the heterogeneity of the formation, problems such as CO2 gravity overtravel, channeling along high-permeability channels, and viscous fingering often occur, which reduce the swept volume of the gas and the efficiency of the gas drive. Therefore, gas channeling greatly affects the CO2 development effect.

[0004] To expand the swept volume of gas-driven oil recovery and improve the effectiveness of CO2 flooding, CO2 foam has become an important technical means to improve the gas-liquid mobility ratio. For example, Chinese invention patent CN 114196389B provides an ultra-low interfacial tension self-assembled carbon dioxide foam flooding agent suitable for low-permeability reservoirs, composed of the following components: {di[N-methyl-N-(3-dodecyloxy-2-hydroxy)propane-N-(2-hydroxy-3-sulfonate sodium)propane]ammonium chloride}ethane, cocamidopropyl betaine, dodecyl dimethylamine oxide, sodium salicylate, chelating agent, inorganic salt, and the balance being water. This patent also provides a method for preparing and applying this ultra-low interfacial tension self-assembled carbon dioxide foam flooding agent. This self-assembled carbon dioxide foam flooding agent exhibits good salt and acid resistance, high foaming liquid viscosity, produces fine and abundant foam with good stability, good injection performance in low-permeability reservoirs, improves the oil-water mobility ratio, significantly increases sweep efficiency, reduces oil-water interfacial tension, and significantly improves oil washing efficiency. This foaming agent does not produce salting-out phenomenon, nor does it react chemically with calcium and magnesium ions to form precipitates. For example, Chinese invention patent application CN 114196389A provides an ultra-low interfacial tension self-assembled carbon dioxide foam flooding agent suitable for low-permeability reservoirs, composed of the following components by weight percentage: {di[N-methyl-N-(3-dodecyloxy-2-hydroxy)propane-N-(2-hydroxy-3-sulfonate sodium)propane]ammonium chloride} ethane: 0.2-0.3%, cocamidopropyl betaine: 0.2-0.3%, dodecyl dimethylamine oxide: 0.1-0.35%, sodium salicylate: 0.02-0.07%, chelating agent: 0.04-0.14%, inorganic salt: 5-7%, with the balance being water. This patent also provides a method for preparing and applying this ultra-low interfacial tension self-assembled carbon dioxide foam flooding agent. This self-assembled carbon dioxide foam flooding agent exhibits good salt and acid resistance, high foaming liquid viscosity, and achieves an oil-water interfacial tension of 10. -3 The foaming agent produces fine and abundant foam with good stability at or below the mN / m level. It has good injection properties in low-permeability reservoirs, can improve the oil-water mobility ratio, significantly increase sweep efficiency, reduce oil-water interfacial tension, and significantly improve oil washing efficiency. This foaming agent does not cause salting out or react chemically with calcium and magnesium ions to form precipitates.

[0005] CO2 foam is a dispersion system with CO2 as the dispersed phase and a surfactant solution as the dispersion medium. In porous media, CO2 foam can block the liquid film, reduce gas mobility, and expand the gas-driven swept volume, thereby effectively improving phenomena such as gas channeling and fingering. However, in low-permeability reservoirs, which are deeply buried and have high temperatures and salinity, the liquid film strength of conventional CO2 foam systems decreases under high-temperature and high-salinity conditions, leading to a decline in the channeling-blocking ability of CO2 foam. Although ordinary nanoparticle-reinforced CO2 foam systems can partially solve the above problems, the modification cost of nanoparticles in ordinary nanoparticle-reinforced CO2 foam systems is high, and the modified nanoparticles are easily adsorbed into the formation rocks, resulting in a weakening of the foam reinforcement effect of nanoparticles and ultimately affecting the channeling-blocking effect of the foam. Summary of the Invention

[0006] Objective: To address the problems of poor stability of existing foam sealing materials under high-temperature conditions and reduced sealing capacity due to easy adsorption after nanoparticle modification, this invention provides an in-situ modified nanoparticle CO2 foam sealing system, its preparation method, and its application. The reinforcing nanoparticles in the in-situ modified nanoparticle CO2 foam sealing system of this invention can be modified in-situ within the formation, exhibiting characteristics of low adsorption loss, strong interfacial adsorption, and strong foam sealing.

[0007] Technical solution: In-situ modified nanoparticle CO2 foam sealing system, based on the total mass of the in-situ modified nanoparticle CO2 foam sealing system, is composed of the following materials:

[0008] 1-5 wt% nonionic CO2-responsive surfactant;

[0009] Nanoparticles 5-10 wt%;

[0010] Anionic foaming agent 0.1-1wt%;

[0011] Salt ion additive 1-5wt%;

[0012] The remainder is water.

[0013] Furthermore, the nonionic CO2-responsive surfactant is at least one of lauric acid diethanolamide, cocoyl acid diethanolamide, oleic acid diethanolamide, and palmitic acid diethanolamide.

[0014] Furthermore, the nanoparticles are nano-SiO2 particles.

[0015] Furthermore, the anionic foaming agent is at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfonate, and sodium dodecyl sulfate.

[0016] Furthermore, the salt ion auxiliary is at least one of sodium chloride, sodium benzoate, and sodium para-aminosalicylate.

[0017] The preparation method of the in-situ modified nanoparticle CO2 foam sealing system includes the following steps:

[0018] (1) Add the formula amount of nonionic CO2 responsive surfactant and the formula amount of anionic foaming agent to the formula amount of water, and stir evenly at the first stirring speed to obtain mixture a;

[0019] (2) Add the nanoparticles of the formula amount to the mixture a obtained in step (1), stir at the first stirring speed and sonicate until completely dispersed to obtain the mixture b;

[0020] (3) Add the mixture b obtained in step (2) into a high-temperature and high-pressure foam reaction vessel, introduce high-pressure CO2, and stir at the second stirring speed to make the mixture b and high-pressure CO2 mix evenly to obtain acidic mixture c.

[0021] (4) After the acidic mixture c obtained in step (3) is left to stand for a period of time, it is stirred at high speed at the third stirring speed for a certain period of time to obtain the in-situ modified nanoparticle CO2 foam sealing system.

[0022] Furthermore, in steps (1) and (2), the first stirring speed is 100-1000 rpm.

[0023] Furthermore, the stirring time in step (1) is at least 30 minutes, preferably 30-60 minutes;

[0024] The stirring time in step (2) is at least 1 hour, preferably 1-2 hours.

[0025] Preferably, the high-pressure CO2 mentioned in step (3) is CO2 with a pressure greater than 10 MPa.

[0026] Preferably, the second stirring speed in step (3) is 100-500 rpm;

[0027] Preferably, the third stirring speed in step (4) is 4000-10000 rpm, and the stirring time in step (4) is at least 10 minutes, preferably 10-60 minutes.

[0028] Furthermore, the settling time in step (4) is at least 5 minutes, preferably 5-20 minutes.

[0029] The in-situ modified nanoparticle CO2 foam sealing system is prepared by any of the above preparation methods.

[0030] The above-mentioned in-situ modified nanoparticle CO2 foam sealing system is used as a CO2 sealing agent in oil extraction.

[0031] The in-situ modified nanoparticle CO2 foam sealing system, preparation method, and application provided by this invention have the following beneficial effects:

[0032] (1) The in-situ modified nanoparticle CO2 foam sealing system provided by the present invention has good hydrophilicity and high Zeta potential before encountering CO2, good dispersion stability in water, and low adsorption loss in the formation.

[0033] (2) The in-situ modified nanoparticle CO2 foam sealing system provided by the present invention is protonated by nonionic CO2 responsive surfactant after encountering CO2, and exhibits the properties of positive ionic surfactant. Under the action of electrostatics, it is adsorbed on the surface of nanoparticles, thereby modifying the surface of nanoparticles in situ. This avoids the cumbersome grafting reaction, is simple and easy to implement, and has low cost.

[0034] (3) The in-situ modified nanoparticles have enhanced adsorption at the gas-liquid interface, which can improve the stability of CO2 foam and enhance the sealing and cross-contamination performance of CO2 foam.

[0035] (4) Compared with other nanoparticle-reinforced CO2 foam systems, nanoparticles have lower adsorption loss and only undergo in-situ modification after encountering CO2, resulting in stronger gas-liquid interface adsorption capacity, higher strength after foaming, and better sealing effect on high-permeability channels.

[0036] (5) The preparation method is simple and easy to operate, and online dispensing can be achieved. Attached Figure Description

[0037] Figure 1 A schematic diagram showing the change in conductivity of nonionic CO2-responsive surfactants before and after CO2 introduction;

[0038] Figures 2a-2b This is a schematic diagram showing the change in surface wettability of nanoparticles before and after CO2 introduction;

[0039] Figure 3 A schematic diagram of the foaming performance of the in-situ modified nanoparticle-enhanced CO2 foam system A1 prepared in Specific Example 1;

[0040] Figure 4 This is a schematic diagram of the foaming performance of the in-situ modified nanoparticle-enhanced CO2 foam system A2 prepared in Specific Example 2;

[0041] Figure 5 A schematic diagram of the foaming performance of CO2 foam system D1 prepared for Experimental Example 3;

[0042] Figure 6 A schematic diagram of the foaming performance of the nanoparticle-reinforced CO2 foam system D2 prepared for Experimental Example 4;

[0043] Figure 7A schematic diagram showing the pressure change before and after injection of A1 into the in-situ modified nanoparticle CO2 foam sealing system. Detailed Implementation

[0044] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0045] The present invention will be described in detail below through embodiments.

[0046] Characterization methods:

[0047] 1. Foaming performance of in-situ modified nanoparticle-reinforced CO2 foam system: The foaming performance of the in-situ modified nanoparticle-reinforced CO2 foam system under different stirring speeds was tested using a high-temperature and high-pressure foam reactor. A longer half-life indicates better stability of the in-situ modified nanoparticle-reinforced CO2 foam system. Specifically, the stirring speeds in the high-temperature and high-pressure reactor were 4000 r / min, 6000 r / min, 8000 r / min, and 10000 r / min.

[0048] Specific testing method: Inject 100-500 mL of mixed solution c into the reaction vessel, inject CO2 gas into the reaction vessel to the required pressure and then close the valve. First, stir at low speed to mix mixed solution c with CO2 to form an acidic solution, and then stir at high speed to obtain in-situ modified nanoparticle reinforced CO2 foam.

[0049] 2. Sealing effect of in-situ modified nanoparticle-enhanced CO2 foam sealing system: The sealing effect of the in-situ modified nanoparticle-enhanced CO2 foam sealing system was tested using a high-temperature and high-pressure core displacement device. The core used was 10cm in length and had a permeability of 1000mD.

[0050] Specific testing method: First, CO2 was injected into the fracture core using an ISCO pump, and the pressure was tested; then, 500 mL of the prepared in-situ modified nanoparticle reinforced CO2 foam system was poured into an intermediate container, and a certain amount was injected into the core using an ISCO pump. Then, a certain amount of CO2 was injected into the core again using an ISCO pump, and the pressure was tested. The injection pressure of CO2 before and after was compared. Specific Implementation Example 1

[0052] The in-situ modified nanoparticle CO2 foam encapsulation system A1, based on the total mass of the in-situ modified nanoparticle CO2 foam encapsulation system A1, is composed of the following materials:

[0053] 3 wt% nonionic CO2-responsive surfactant;

[0054] 6 wt% nanoparticles;

[0055] Anionic foaming agent 0.3 wt%;

[0056] Salt ion additive 3wt%;

[0057] The remainder is water.

[0058] Furthermore, the nonionic CO2-responsive surfactant is lauric acid diethanolamide.

[0059] Furthermore, the nanoparticles are nano-SiO2 particles.

[0060] Furthermore, the anionic foaming agent is sodium dodecylbenzenesulfonate.

[0061] Furthermore, the salt ion auxiliary is sodium chloride.

[0062] The preparation method of the in-situ modified nanoparticle CO2 foam sealing system includes the following steps:

[0063] (1) Add the formula amount of nonionic CO2 responsive surfactant and the formula amount of anionic foaming agent to the formula amount of water, and stir evenly at the first stirring speed to obtain mixture a;

[0064] (2) Add the nanoparticles of the formula amount to the mixture a obtained in step (1), stir at the first stirring speed and sonicate until completely dispersed to obtain the mixture b;

[0065] (3) Add the mixture b obtained in step (2) into a high-temperature and high-pressure foam reaction vessel, introduce high-pressure CO2, and stir at the second stirring speed to make the mixture b and high-pressure CO2 mix evenly to obtain acidic mixture c.

[0066] (4) After the acidic mixture c obtained in step (3) is left to stand for a period of time, it is stirred at high speed at the third stirring speed for a certain period of time to obtain the in-situ modified nanoparticle CO2 foam sealing system A1.

[0067] Furthermore, in steps (1) and (2), the first stirring speed is 500 rpm.

[0068] Furthermore, the stirring time in step (1) is 45 minutes;

[0069] The stirring time in step (2) is 1.5 hours.

[0070] Preferably, the high-pressure CO2 mentioned in step (3) is CO2 with a pressure of 12 MPa.

[0071] Preferably, the second stirring speed in step (3) is 300 rpm;

[0072] Preferably, the third stirring speed in step (4) is 6000 rpm, and the stirring time in step (4) is 30 minutes.

[0073] Furthermore, the settling time in step (4) is 10 minutes.

[0074] The in-situ modified nanoparticle CO2 foam sealing system A1 was prepared by any of the above preparation methods.

[0075] The above-mentioned in-situ modified nanoparticle CO2 foam sealing system A1 is used as a CO2 sealing agent in oil extraction.

[0076] Using the aforementioned method for testing the stability of CO2 foam, the half-life at different stirring speeds was obtained, and the experimental results are as follows: Figure 3 As shown in the results, it can be seen that with the increase of shear rate, the liquid half-life of the in-situ modified nanoparticle CO2 foam sealing system A1 also gradually increases. When the shear rate increases from 4000 r / min to 10000 r / min, the liquid half-life increases from 65 min to 134 min, indicating that the stability of CO2 foam is greatly improved. Specific Implementation Example 2

[0078] The in-situ modified nanoparticle CO2 foam encapsulation system A2, based on the total mass of the in-situ modified nanoparticle CO2 foam encapsulation system A2, is composed of the following materials:

[0079] 5 wt% nonionic CO2-responsive surfactant;

[0080] 10 wt% nanoparticles;

[0081] Anionic foaming agent 0.3 wt%;

[0082] Salt ion additive 3wt%;

[0083] The remainder is water.

[0084] Furthermore, the nonionic CO2-responsive surfactant is cocoyl diethanolamide.

[0085] Furthermore, the nanoparticles are nano-SiO2 particles.

[0086] Furthermore, the anionic foaming agent is sodium dodecyl sulfonate.

[0087] Furthermore, the salt ion auxiliary is sodium benzoate.

[0088] The preparation method of the in-situ modified nanoparticle CO2 foam sealing system includes the following steps:

[0089] (1) Add the formula amount of nonionic CO2 responsive surfactant and the formula amount of anionic foaming agent to the formula amount of water, and stir evenly at the first stirring speed to obtain mixture a;

[0090] (2) Add the nanoparticles of the formula amount to the mixture a obtained in step (1), stir at the first stirring speed and sonicate until completely dispersed to obtain the mixture b;

[0091] (3) Add the mixture b obtained in step (2) into a high-temperature and high-pressure foam reaction vessel, introduce high-pressure CO2, and stir at the second stirring speed to make the mixture b and high-pressure CO2 mix evenly to obtain acidic mixture c.

[0092] (4) After the acidic mixture c obtained in step (3) is left to stand for a period of time, it is stirred at high speed at the third stirring speed for a certain period of time to obtain the in-situ modified nanoparticle CO2 foam sealing system A2.

[0093] Furthermore, in steps (1) and (2), the first stirring speed is 300 rpm.

[0094] Furthermore, the stirring time in step (1) is 50 minutes;

[0095] The stirring time in step (2) is 1.5 hours.

[0096] Preferably, the high-pressure CO2 mentioned in step (3) is CO2 with a pressure of 13 MPa.

[0097] Preferably, the second stirring speed in step (3) is 200 rpm;

[0098] Preferably, the third stirring speed in step (4) is 6000 rpm, and the stirring time in step (4) is 40 minutes.

[0099] Furthermore, the settling time in step (4) is 15 minutes.

[0100] The in-situ modified nanoparticle CO2 foam sealing system A2 is prepared by any of the above preparation methods.

[0101] The above-mentioned in-situ modified nanoparticle CO2 foam sealing system A2 is used as a CO2 sealing agent in oil extraction.

[0102] Using the aforementioned method for testing the stability of CO2 foam, the half-life at different stirring speeds was obtained, and the experimental results are as follows: Figure 4As shown in the results, it can be seen that with the increase of shear rate, the liquid half-life of the in-situ modified nanoparticle CO2 foam sealing system A2 also gradually increases. When the shear rate increases from 4000 r / min to 10000 r / min, the liquid half-life increases from 78 min to 146 min. Compared with the in-situ modified nanoparticle CO2 foam sealing system A1 in Specific Example 1, the liquid half-life (stability) of the system also increases accordingly with the increase of nonionic surfactant and nanoparticle concentration. Specific Implementation Example 3

[0104] The in-situ modified nanoparticle CO2 foam sealing system A3, based on the total mass of the in-situ modified nanoparticle CO2 foam sealing system, is composed of the following materials:

[0105] 1 wt% nonionic CO2-responsive surfactant;

[0106] 5 wt% nanoparticles;

[0107] Anionic foaming agent 0.1 wt%;

[0108] Salt ion additive 1 wt%;

[0109] The remainder is water.

[0110] Furthermore, the nonionic CO2-responsive surfactant is oleic acid diethanolamide.

[0111] Furthermore, the nanoparticles are nano-SiO2 particles.

[0112] Furthermore, the anionic foaming agent is sodium dodecyl sulfate.

[0113] Furthermore, the salt ion auxiliary is sodium para-aminosalicylate.

[0114] The preparation method of the in-situ modified nanoparticle CO2 foam sealing system includes the following steps:

[0115] (1) Add the formula amount of nonionic CO2 responsive surfactant and the formula amount of anionic foaming agent to the formula amount of water, and stir evenly at the first stirring speed to obtain mixture a;

[0116] (2) Add the nanoparticles of the formula amount to the mixture a obtained in step (1), stir at the first stirring speed and sonicate until completely dispersed to obtain the mixture b;

[0117] (3) Add the mixture b obtained in step (2) into a high-temperature and high-pressure foam reaction vessel, introduce high-pressure CO2, and stir at the second stirring speed to make the mixture b and high-pressure CO2 mix evenly to obtain acidic mixture c.

[0118] (4) After the acidic mixture c obtained in step (3) is left to stand for a period of time, it is stirred at high speed at the third stirring speed for a certain period of time to obtain the in-situ modified nanoparticle CO2 foam sealing system A3.

[0119] Furthermore, in steps (1) and (2), the first stirring speed is 100 rpm.

[0120] Furthermore, the stirring time in step (1) is 60 minutes;

[0121] The stirring time in step (2) is 2 hours.

[0122] Preferably, the high-pressure CO2 mentioned in step (3) is CO2 with a pressure of 15 MPa.

[0123] Preferably, the second stirring speed in step (3) is 100 rpm;

[0124] Preferably, the third stirring speed in step (4) is 4000 rpm, and the stirring time in step (4) is 60 minutes.

[0125] Furthermore, the settling time in step (4) is 20 minutes.

[0126] The in-situ modified nanoparticle CO2 foam sealing system A3 was prepared by any of the above preparation methods.

[0127] The above-mentioned in-situ modified nanoparticle CO2 foam sealing system A3 is used as a CO2 sealing agent in oil extraction. Specific Implementation Example 4

[0129] The in-situ modified nanoparticle CO2 foam sealing system A4, based on the total mass of the in-situ modified nanoparticle CO2 foam sealing system, is composed of the following materials:

[0130] 4 wt% nonionic CO2-responsive surfactant;

[0131] 8 wt% nanoparticles;

[0132] 1 wt% anionic foaming agent;

[0133] Salt ion additive 5wt%;

[0134] The remainder is water.

[0135] Further, the nonionic CO2-responsive surfactant is palmitic acid diethanolamide. In another embodiment, the nonionic CO2-responsive surfactant is a mixture of lauric acid diethanolamide and cocoyl acid diethanolamide in equal mass ratios. In another embodiment, the nonionic CO2-responsive surfactant is a mixture of lauric acid diethanolamide, cocoyl acid diethanolamide, oleic acid diethanolamide, and palmitic acid diethanolamide in equal mass ratios.

[0136] Furthermore, the nanoparticles are nano-SiO2 particles.

[0137] Further, the anionic foaming agent is a mixture of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium dodecyl sulfate in equal mass ratios. In another embodiment, the anionic foaming agent is a mixture of sodium dodecylbenzenesulfonate and sodium dodecyl sulfate in equal mass ratios.

[0138] Further, the salt ion auxiliary is a mixture of sodium chloride and sodium benzoate in equal mass ratios. In another embodiment, the salt ion auxiliary is a mixture of sodium chloride, sodium benzoate, and sodium para-aminosalicylate in equal mass ratios.

[0139] The preparation method of the in-situ modified nanoparticle CO2 foam sealing system includes the following steps:

[0140] (1) Add the formula amount of nonionic CO2 responsive surfactant and the formula amount of anionic foaming agent to the formula amount of water, and stir evenly at the first stirring speed to obtain mixture a;

[0141] (2) Add the nanoparticles of the formula amount to the mixture a obtained in step (1), stir at the first stirring speed and sonicate until completely dispersed to obtain the mixture b;

[0142] (3) Add the mixture b obtained in step (2) into a high-temperature and high-pressure foam reaction vessel, introduce high-pressure CO2, and stir at the second stirring speed to make the mixture b and high-pressure CO2 mix evenly to obtain acidic mixture c.

[0143] (4) After the acidic mixture c obtained in step (3) is left to stand for a period of time, it is stirred at high speed at the third stirring speed for a certain period of time to obtain the in-situ modified nanoparticle CO2 foam sealing system A4.

[0144] Furthermore, in steps (1) and (2), the first stirring speed is 1000 rpm.

[0145] Furthermore, the stirring time in step (1) is 30 minutes;

[0146] The stirring time in step (2) is 1 hour.

[0147] Preferably, the high-pressure CO2 mentioned in step (3) is CO2 with a pressure of 10 MPa.

[0148] Preferably, the second stirring speed in step (3) is 500 rpm;

[0149] Preferably, the third stirring speed in step (4) is 10,000 rpm, and the stirring time in step (4) is 10 minutes.

[0150] Furthermore, the settling time in step (4) is 5 minutes.

[0151] The in-situ modified nanoparticle CO2 foam sealing system A4 was prepared by any of the above preparation methods.

[0152] The above-mentioned in-situ modified nanoparticle CO2 foam sealing system A4 is used as a CO2 sealing agent in oil extraction.

[0153] Performance and Characterization

[0154] Experimental Example 1

[0155] A 1% (w / w) aqueous solution of a nonionic CO2-responsive surfactant (cocoyl diethanolamide was used in this experiment) was prepared. After the nonionic CO2-responsive surfactant was completely dissolved, the conductivity of the solution was measured using a conductivity meter. Then, CO2 and N2 were alternately introduced, and the conductivity of the surfactant solution was measured. The experimental results are as follows: Figure 1 As shown, Figure 1 In the diagram, squares represent the introduction of carbon dioxide and circles represent the introduction of nitrogen. The results show that the conductivity gradually increases with the increase of CO2 introduction time; and gradually decreases with the increase of N2 introduction time (CO2 escapes). This indicates that nonionic surfactants have CO2-responsive characteristics. Introducing CO2 can turn nonionic surfactants into charged ionic surfactants, and after CO2 escapes, the charged ionic surfactants become uncharged nonionic surfactants.

[0156] Experimental Example 2

[0157] A mixed solution with a mass concentration of 3% nonionic CO2-responsive surfactant (cocoyl diethanolamide) and 6% nano-SiO2 particles was prepared. A small amount of the solution was centrifuged at high speed to obtain nano-SiO2 particles, and then the contact angle was measured. CO2 was introduced and stirred to form an acidic mixture. A small amount of the solution was centrifuged at high speed again to obtain nano-SiO2 particles, and the contact angle was measured. The experimental results are as follows. Figure 2a and Figure 2bAs shown in the experimental results, the surface of the nano-SiO2 particles changed from hydrophilic to hydrophobic before and after CO2 was introduced. This is mainly because the negatively charged nano-SiO2 particles reacted with the positively charged ionic surfactant after CO2 response, and the ionic surfactant was adsorbed onto the surface of the nano-SiO2 particles, thus performing in-situ hydrophobic modification on the surface of the nano-SiO2 particles.

[0158] Experimental Example 3

[0159] CO2 foam system D1 was prepared using the same method as in Specific Example 1, except that it did not contain nano-SiO2 particles.

[0160] The half-life of CO2 foam was tested under different shear rates, and the experimental results are as follows: Figure 5 As shown in the results, it can be seen that with the increase of shear rate, the liquid separation half-life of CO2 foam system D1 also gradually increases. When the shear rate increases from 4000 r / min to 10000 r / min, the liquid separation half-life increases from 35 min to 67 min. Compared with specific example 1, CO2 foam system D1 only has surfactant, and the liquid separation half-life (stability) of the system is reduced by more than half. Therefore, nano SiO2 particles have a greater weight in increasing the stability of the system.

[0161] Test Example 4

[0162] The nanoparticle-reinforced CO2 foam system D2 was prepared using the same method as in Specific Example 1, except that a common nonionic surfactant was used instead of a nonionic CO2-responsive surfactant.

[0163] The half-life of CO2 foam was tested under different shear rates, and the experimental results are as follows: Figure 6 As shown in the results, the liquid half-life of the nanoparticle-reinforced CO2 foam system D2 gradually increases with the increase of shear rate. When the shear rate increases from 4000 r / min to 10000 r / min, the liquid half-life increases from 40 min to 81 min. Compared with Example 1, the ordinary nonionic surfactant in the system does not have CO2 responsive characteristics, and therefore cannot be converted from a nonionic surfactant to an ionic surfactant to adsorb onto the surface of the nanoparticles for modification. Because the nanoparticles cannot be adsorbed onto the gas-liquid interface to improve foam stability, the liquid half-life (stability) of the nanoparticle-reinforced CO2 foam system D2 is much lower than that of the in-situ modified nanoparticle CO2 foam sealing system A1 in Example 1.

[0164] Experimental Example 5

[0165] First, water was injected separately into the water-saturated core, and the base pressure difference was tested. Then, the in-situ modified nanoparticle CO2 foam sealing system A1 and CO2 prepared in Example 1 were injected, and the injection pressure difference was tested. The experimental results are as follows: Figure 7 As shown in the figure, the initial pressure difference during water injection was very low, only a few kPa. However, after the injection of the in-situ modified nanoparticle CO2 foam sealing system A1 and CO2, the injection pressure difference reached a maximum of 80 kPa. This indicates that CO2 and the in-situ modified nanoparticles formed a foam system in the porous core medium, increasing the flow resistance.

[0166] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. In-situ modified nanoparticulate CO2 foam channeling containment system characterized by, The in-situ modified nanoparticle CO2 foam channeling system is composed of the following materials based on the total mass of the system: non-ionic CO2 responsive surfactant 1-5 wt%; nanoparticles 5-10 wt%; anionic foaming agent 0.1-1 wt%; salt ion assistant 1-5 wt%; the balance being water, wherein: the non-ionic CO2 responsive surfactant is at least one of lauric acid diethanolamide, coconut oil diethanolamide, oleic acid diethanolamide, and palmitic acid diethanolamide; the nanoparticles are nano-SiO2 particles; the anionic foaming agent is at least one of sodium dodecyl benzene sulfonate, sodium dodecyl sulfonate, and sodium dodecyl sulfate; the salt ion assistant is at least one of sodium chloride, sodium benzoate, and sodium p-aminosalicylate.

2. The method of making an in-situ modified nanoparticulate CO2 foam channeling control system of claim 1, characterized in that, The method comprises the following steps: (1) adding a formula amount of non-ionic CO2 responsive surfactant and a formula amount of anionic foaming agent to a formula amount of water, stirring uniformly at a first stirring speed to obtain a mixed solution a; (2) adding a formula amount of nanoparticles to the mixed solution a obtained in step (1), stirring at the first stirring speed and ultrasonicating until completely dispersed to obtain the mixed solution b; (3) adding the mixed solution b obtained in step (2) to a high-temperature and high-pressure foam reaction container, passing in high-pressure CO2, and stirring at a second stirring speed to uniformly mix the mixed solution b with the high-pressure CO2 to obtain an acidic mixed solution c; (4) allowing the acidic mixed solution c obtained in step (3) to stand for a period of time, and then stirring at a third stirring speed for a certain period of time to obtain the in-situ modified nanoparticle CO2 foam channeling system.

3. The method of claim 2, wherein the in-situ modified nanoparticle CO2 foam channeling control system is prepared by the steps of: The first stirring speed in steps (1) and (2) is 100-1000 rpm.

4. The method of claim 2, wherein the in-situ modified nanoparticle CO2 foam channeling control system is prepared by the steps of: The stirring time in step (1) is at least 30 minutes; The stirring time in step (2) is at least 1 hour.

5. The method of claim 4, wherein the in-situ modified nanoparticle CO2 foam channeling control system is prepared by the steps of: The stirring time in step (1) is 30-60 minutes; The stirring time in step (2) is 1-2 hours.

6. The method of claim 2, wherein the in-situ modified nanoparticle CO2 foam channeling control system is prepared by the steps of: The high-pressure CO2 in step (3) is CO2 with a pressure greater than 10 MPa; The second stirring speed in step (3) is 100-500 rpm.

7. The method of claim 2, wherein the in-situ modified nanoparticle CO2 foam channeling control system is prepared by the steps of: The third stirring speed in step (4) is 4000-10000 rpm, and the stirring time in step (4) is at least 10 minutes; The standing time in step (4) is at least 5 minutes.

8. The method of claim 7, wherein the in-situ modified nanoparticle CO2 foam channeling control system is prepared by the steps of: The stirring time in step (4) is 10-60 minutes; The standing time in step (4) is 5-20 minutes.

9. In-situ modified nanoparticulate CO2 foam channeling containment system characterized by, The in-situ modified nanoparticle CO2 foam channeling system is prepared by any one of the preparation methods of claims 2-8.

10. Use of the in-situ modified nanoparticle CO2 foam channeling system of claim 1 or 9 as a CO2 channeling agent in oil exploitation.

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