Anti-swelling nano imbibition agent for shale oil reservoir fracturing as well as preparation method and application of anti-swelling nano imbibition agent

Abstract

The invention belongs to the technical field of oilfield chemistry, and particularly discloses an anti-swelling nano imbibition agent for shale oil reservoir fracturing as well as a preparation method and application of the anti-swelling nano imbibition agent. The anti-swelling nano imbibition agent comprises the following components in parts by weight: 25-30 parts of sulfonated aminated graphene, 1-2 parts of a quaternary ammonium salt viscoelastic surfactant, 3-5 parts of a salt dissolution promoter, 5-7 parts of low-carbon alcohol and 55-65 parts of water. According to the anti-swelling nano imbibition agent for shale oil reservoir fracturing as well as the preparation method and the application of the anti-swelling nano imbibition agent, the quaternary ammonium salt viscoelastic surfactant is subjected to shear tackifying in a reservoir migration process and is matched with the sulfonated aminated graphene for use, so that the imbibition oil discharge effect and the anti-swelling performance of the nano imbibition displacement agent can be remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of oilfield chemistry, and particularly relates to an anti-swelling nano imbibition agent for shale reservoir fracturing, a preparation method thereof and an application thereof. Background Art

[0002] The potential of continental shale oil resources in China is huge, and it has become an important replacement field for conventional oil and gas resources, playing an important supporting role in ensuring the stable production of oil and increasing gas production in the country. However, in the actual development process, the reservoir energy continuously decreases, resulting in a low recovery rate improvement. The existing development of shale reservoirs is often accompanied by large-scale volume fracturing to improve the conductivity of the target reservoir. However, the fracturing technology can only improve the conductivity from the fracture of the reservoir to the bottom hole. The link from the reservoir matrix to the fracture still relies on the spontaneous imbibition of oil and water. Therefore, the imbibition displacement technology has become one of the potential development technical means for shale reservoirs. For the efficient imbibition mechanism of shale reservoirs, it is necessary to transform the passive spontaneous imbibition between oil and water into active enhanced imbibition, and the imbibition oil production method changes from static spontaneous imbibition to dynamic forced imbibition, so as to greatly improve the imbibition efficiency.

[0003] Taking the K 2qn1 shale formation in Gulong Sag as an example, the development degree of its clay minerals is second only to quartz + feldspar minerals, and the content ranges from 1.1% to 80.0%, with an average content of 33.6%. Montmorillonite and illite / smectite mixed layer minerals in clay minerals have a high degree of hydration swelling characteristics, and their strong water sensitivity causes devastating damage in shale reservoirs with low permeability and low porosity. Therefore, the problem of clay swelling must be considered and corresponding anti-swelling measures must be given during the development of shale reservoirs. So far, the anti-swelling measure with a higher usage frequency is to add 0.5wt% - 2wt% potassium chloride to the injection system. Laboratory tests show that its anti-swelling rate can be as high as 87%. However, the injection of high-concentration potassium chloride will cause the diffusion pollution of chloride ions in the formation, destroying the quality of groundwater and the soil environment. Therefore, it is urgent to find an anti-swelling agent to replace potassium chloride.

[0004] After fracturing, anionic surfactants are often used as imbibition agents. Anionic surfactants have high interfacial activity, good temperature resistance and high cloud points, but their salt resistance is poor and they cannot be used in shale reservoirs with higher temperatures. Graphene materials are two-dimensional, sheet-like, carbon-based nanomaterials with nanoscale dimensions, high specific surface area, multiple active sites, quantum effects, environmental protection and other characteristics, and are often studied for improving the recovery rate of low-permeability oil reservoirs. Amino-functionalized graphene can be obtained by graphene oxidation and has good hydrophilic characteristics. Research in the field of oil and gas field development at home and abroad shows that graphene oxide fluid has the functions of changing the fluidity of crude oil, reducing the interfacial tension between oil and water and realizing wettability reversal in the reservoir, and is an ideal environmentally friendly nano imbibition agent.

[0005] Existing Chinese invention patent: Multi-grafting site nano-carbon materials and active nano-carbon materials, their preparation methods and oil displacement systems for ultra-low permeability reservoirs, patent number: CN112980415A, studied the application of carbon nano-materials in the field of petroleum engineering. This patent demonstrated the feasibility of nano-materials in ultra-low permeability applications.

[0006] Because of their small particle size and controllable particle size, nano-materials can better enter the tiny pores and fractures of shale oil reservoirs, play an oil displacement role, and improve the recovery rate of shale oil reservoirs. However, shale oil reservoirs are usually complex environments with high temperature, high pressure, and high salinity. Nano-carbon materials or nano-magnetic materials are prone to oxidation during high-temperature use or aggregation due to the compression of the double electric layer in a high ionic strength environment, resulting in an increase in size, making it difficult for the oil displacement agent to enter the tiny pores and fractures and causing a decrease in the recovery rate.

[0007] Therefore, it is of great significance to develop an anti-swelling nano-infiltration agent with long-term stability in complex environments of high temperature, high pressure, and high salinity in this field. Summary of the Invention

[0008] The purpose of the present invention is to provide an anti-swelling nano-infiltration agent for fracturing shale oil reservoirs, its preparation method and application. By using the shear thickening of quaternary ammonium salt viscoelastic surfactant during reservoir migration in combination with sulfonated amino-functionalized graphene, the infiltration and oil displacement effect and anti-swelling performance of the nano-infiltration displacement agent can be significantly improved.

[0009] To achieve the above purpose, the present invention provides an anti-swelling nano-infiltration agent for fracturing shale oil reservoirs, which includes the following components by weight: 25-30 parts of sulfonated amino-functionalized graphene, 1-2 parts of quaternary ammonium salt viscoelastic surfactant, 3-5 parts of salt solubilizer, 5-7 parts of lower alcohol, and 55-65 parts of water.

[0010] Preferably, the lower alcohol includes but is not limited to one or a combination of two or more of methanol, ethanol, n-propanol, and isopropanol; the salt solubilizer includes but is not limited to sodium chloride.

[0011] A preparation method of an anti-swelling nano-infiltration agent for fracturing shale oil reservoirs includes the following steps:

[0012] Step S1, prepare sulfonated amino-functionalized graphene;

[0013] Step S2, prepare quaternary ammonium salt viscoelastic surfactant;

[0014] Step S3, mix sulfonated amino-functionalized graphene, quaternary ammonium salt viscoelastic surfactant, lower alcohol, salt solubilizer, and water evenly according to the above proportions to obtain the anti-swelling nano-infiltration agent.

[0015] Preferably, step S1 is specifically

[0016] Step S11: Disperse 1,5-dinitronaphthalene in ammonia water, and perform ultrasonic treatment, heating, centrifugation, dialysis, washing, and drying to obtain amino-functionalized graphene.

[0017] Step S12: Disperse a dialdehyde compound and a sodium p-aminobenzenesulfonate derivative in distilled water, perform heating, centrifugation, washing, and drying, and disperse the solid in water to obtain an aqueous solution of the dialdehyde compound with sulfonic acid groups.

[0018] Step S13: Add the amino-functionalized graphene and the aqueous solution of the dialdehyde compound with sulfonic acid groups to distilled water, mix evenly, carry out a reaction under magnetic stirring with temperature increase, and after the reaction is completed, perform reduced-pressure distillation, filtration, washing, and drying to obtain sulfonated amino-functionalized graphene.

[0019] Preferably, in step S11, the heating condition is to react at 180 - 220 °C for 18 - 22 h; the centrifugation speed is 8000 - 10000 rpm; dialysis is carried out using a dialysis bag for 48 h to remove unfused small molecules, where the cut-off molecular weight is 1000 Da; washing is to wash the centrifuged solid with distilled water 3 - 5 times; drying is to dry at a temperature of 60 - 100 °C to constant weight;

[0020] The concentration of ammonia water is 25 - 28 wt%; the mass ratio of 1,5-dinitronaphthalene to ammonia water is 1:6 - 1:4;

[0021] The particle size of the amino-functionalized graphene in water is 26 - 30 nm, and the thickness is 0.2 - 2 nm.

[0022] Preferably, in step S12, the dialdehyde compound includes but is not limited to glyoxal and malonaldehyde;

[0023] The molar ratio of the dialdehyde compound to the sodium p-aminobenzenesulfonate derivative is 6:5 - 1:1;

[0024] The sodium p-aminobenzenesulfonate derivative is one or a combination of two or more of 2-aminobenzenesulfonate, 3-aminobenzenesulfonate, and 4-aminobenzenesulfonate.

[0025] Preferably, in step S12, the heating condition is to react at 35 - 40 °C for 8 - 12 h; the centrifugation speed is 6000 - 8000 rpm; washing is to wash the centrifuged solid with distilled water 3 - 5 times; the drying condition is to dry at 80 °C for 3 h.

[0026] Preferably, in step S13, the mass ratio of the aqueous solution of the dialdehyde compound with sulfonic acid groups to the amino-functionalized graphene is 20:0.5 - 1.5;

[0027] Heat to 30-40 °C, and the reaction time is 8-12 h; the washing is repeated 4 times with distilled water; the drying is carried out at 80 °C until constant weight.

[0028] Preferably, step S2 is specifically as follows

[0029] Step S21: Add N,N-dimethylpropanolamine and bromoalkane into a three-necked flask at a molar ratio of 1.2-1.4:1, add n-butanol with a mass fraction of 40-60%, control the reaction temperature at 80-100 °C, and reflux and react in a collecting type magnetic stirrer for 5-9 h to obtain product A;

[0030] Among them, the bromoalkane includes but is not limited to hexadecane and octadecane;

[0031] Step S22: Carry out vacuum distillation on the obtained product A, then wash out the pale yellow solid with acetone, and then recrystallize 7 times with a mixed solution of acetone and acetonitrile with a volume ratio of 4:1 to obtain a white powder solid. Subsequently, place the white powder solid in a vacuum drying oven at 60 °C for drying to obtain the quaternary ammonium salt viscoelastic surfactant.

[0032] Application of an anti-swelling nano-infiltration agent for shale reservoir fracturing as a nano-infiltration displacement agent for shale reservoir.

[0033] The present invention adopts the above-mentioned anti-swelling nano-infiltration agent for shale reservoir fracturing, its preparation method and application, and the beneficial effects are as follows:

[0034] (1) The nano-infiltration displacement agent prepared by the present invention contains a sulfonated amino-functionalized graphene. The surface sulfonation treatment generates electrostatic repulsion between graphene oxide particles, improving the dispersion ability between particles; due to the addition of sulfonic acid groups, the amino-functionalized graphene generates stronger electrostatic repulsion between its particles, resulting in an increase in the double diffusion layer distance, improving the dispersion ability of graphene particles in high-temperature and high-salinity environments, avoiding agglomeration and flocculation between particles, and improving the recovery rate; the sulfonic acid groups can improve the dispersion stability of graphene and the high-temperature and salt resistance characteristics of the infiltration system;

[0035] (2) The quaternary ammonium salt viscoelastic surfactant in the present invention can adsorb and neutralize the negative charge on the clay surface, and can also adsorb between the clay crystal layers, reducing the charge on the surface and between the crystal layers, as well as the thickness of the clay surface diffusion double layer and the Zeta potential, thereby reducing the repulsion between clay minerals and achieving the anti-swelling effect; in addition to achieving the anti-swelling effect in the formation environment, the quaternary ammonium salt viscoelastic surfactant can also produce a synergistic effect with sulfonated amino-functionalized graphene, significantly improving the infiltration and displacement effect of sulfonated amino-functionalized graphene;

[0036] (3) In the present invention, the quaternary ammonium salt cationic viscoelastic surfactant and reservoir fine particles are adsorbed to each other through hydrogen bonding and electrostatic interaction, forming a stable and uniform viscous molecular film on their surfaces, realizing in-situ fixation of formation fine silt or clay particles, and capable of acting as a clay stabilizer. The swelling inhibitor molecules can adsorb on the surfaces of multiple clay particles and multiple crystal layers simultaneously with their unique functional groups and long chain lengths on the molecular chains, stabilizing and solidifying multiple clay particles, thereby effectively inhibiting their dispersion and migration.

[0037] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0038] Figure 1 Flow chart of the synthesis of sulfonated and aminated graphene for an anti-swelling nano-infiltration agent for shale reservoir fracturing, its preparation method and application examples of the present invention;

[0039] Figure 2 FTIR spectra of modified and unmodified aminated graphene for an anti-swelling nano-infiltration agent for shale reservoir fracturing, its preparation method and application examples of the present invention;

[0040] Figure 3 Schematic diagram of the relationship between salt resistance, high temperature resistance and sulfonation grafting rate of sulfonated aminated graphene for an anti-swelling nano-infiltration agent for shale reservoir fracturing, its preparation method and application examples of the present invention; among them, (a) is the applicable layout diagram with a grafting rate of 25%; (b) is the applicable layout diagram with a grafting rate of 30%; (c) is the applicable layout diagram with a grafting rate of 35%; (d) is the applicable layout diagram with a grafting rate of 40%;

[0041] Figure 4 Mass spectrum of SD-16 for an anti-swelling nano-infiltration agent for shale reservoir fracturing, its preparation method and application examples of the present invention;

[0042] Figure 5 Mass spectrum of SD-18 for an anti-swelling nano-infiltration agent for shale reservoir fracturing, its preparation method and application examples of the present invention;

[0043] Figure 6 Flow chart of the synthesis of quaternary ammonium salt viscoelastic surfactant for an anti-swelling nano-infiltration agent for shale reservoir fracturing, its preparation method and application examples of the present invention. Detailed Embodiments

[0044] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0045] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention pertains.

[0046] A preparation method of an anti-swelling nano imbibition agent for fracturing of shale reservoirs, comprising the following steps:

[0047] Step S1, prepare sulfonated amino-functionalized graphene, as Figure 1 - Figure 2 shown.

[0048] Step S11, take 1,5-dinitronaphthalene according to the mass ratio of 1,5-dinitronaphthalene to ammonia water of 1:6 - 1:4, disperse it in ammonia water with a concentration of 25 - 28 wt%, and perform ultrasonic treatment, heating, centrifugation, dialysis, washing, and drying to obtain amino-functionalized graphene. The particle size of the amino-functionalized graphene in water is 26 - 30 nm, and the thickness is 0.2 - 2 nm.

[0049] Among them, the heating condition is to react at 180 - 220 °C for 18 - 22 h, the centrifugation speed is 8000 - 10000 rpm, dialysis is to use a dialysis bag for dialysis for 48 h to remove unfused small molecules, where the cut-off molecular weight is 1000 Da, washing is to wash the centrifuged solid with distilled water 3 - 5 times, and drying is to dry at a temperature of 60 - 100 °C to constant weight.

[0050] Step S12, take dialdehyde compounds and p-aminobenzenesulfonate derivatives according to the molar ratio of dialdehyde compounds to p-aminobenzenesulfonate derivatives of 6:5 - 1:1, disperse them in distilled water, perform heating, centrifugation, washing, and drying, and disperse the product in water to obtain an aqueous solution (F) of dialdehyde compounds with sulfonic acid groups.

[0051] Among them, the dialdehyde compounds include but are not limited to glyoxal and malondialdehyde. The heating condition is to react at 35 - 40 °C for 8 - 12 h. The centrifugation speed is 6000 - 8000 rpm. Washing is to wash the centrifuged solid with distilled water 3 - 5 times. The drying condition is to dry at 80 °C for 3 h.

[0052] Step S13, add the amino-functionalized graphene and the aqueous solution (F) of dialdehyde compounds with sulfonic acid groups to distilled water and mix evenly. Among them, the mass ratio of the aqueous solution of dialdehyde compounds with sulfonic acid groups to amino-functionalized graphene is 20:0.5 - 1.5.

[0053] Heat to 30 - 40 °C and react for 8 - 12 h under magnetic stirring conditions. After the reaction, perform vacuum distillation, filtration, repeat washing with distilled water 4 times, and dry at 80 °C to constant weight to obtain sulfonated amino-functionalized graphene.

[0054] Use hydrothermal method to prepare amino-functionalized graphene with 1,5-dinitronaphthalene, and then use dialdehyde compounds as cross-linking agents to graft p-aminobenzenesulfonate derivatives onto the surface of amino-functionalized graphene to obtain a functional graphene surfactant modified with amino groups and sulfonic acid groups.

[0055] Aminated graphene is a planar two-dimensional structure material composed of carbon atoms. In the formation, small-sized aminated graphene is more likely to enter small pores to expand the swept area and improve the oil washing efficiency. Also, due to its high surface activity, specific surface area, and "aspect ratio" (lateral dimension / thickness), it can better adsorb on the rock wall, improve or even reverse the wettability of the rock surface, and make the crude oil easier to detach from the rock wall surface. By sulfonating its surface, greater electrostatic repulsion is generated between aminated graphene particles due to the introduction of sulfonate groups, improving the dispersion ability between particles and avoiding agglomeration and flocculation of particles.

[0056] Perform an orthogonal experiment on step S1, as specifically shown in Table 1 and Table 2:

[0057] Table 1 Orthogonal Experiment

[0058]

[0059] Table 2 Experimental Results

[0060]

[0061]

[0062] As can be seen from the above table, the order of influence on the yield is: reaction temperature / ℃ in step S12 > reaction time / h in step S11 = reaction temperature / ℃ in step S11 > mass ratio of solution F to aminated graphene in step S13 > reaction time / h in step S12.

[0063] The optimal condition combination is A2B3C2D3E2. The reaction temperature in step S2 is 37.5 °C, the reaction time in step S1 is 22 h, the reaction temperature in step S1 is 220 °C, the reaction time in step S2 is 22 h, and the mass ratio of solution F to aminated graphene in step S3 is 2:1. According to the experiment under the best condition combination, the yield is measured to be 90.55% and the grafting rate of sulfonate groups is 86.21% under this condition.

[0064] Continuously adjust the salinity and environmental temperature in water, and analyze the relationship between salt resistance, high-temperature resistance, and sulfonation grafting rate from the dispersion stability of sulfonated graphene in water. As Figure 3 shown, adjust the ratio to select sulfonated graphene with grafting rates of 25%, 30%, 35%, and 40% respectively. Green represents that it does not agglomerate at this salinity and temperature. The experimental results show that when the sulfonate grafting rate is greater than 80%, its salt resistance and high-temperature resistance do not increase significantly. Therefore, during the production process, while ensuring the yield, only the sulfonate grafting rate needs to be greater than 80%.

[0065] Step S2, prepare a quaternary ammonium salt viscoelastic surfactant, as Figure 4 - Figure 6 shown.

[0066] Step S21: Add N,N-dimethylpropanolamine and bromoalkane into a three-necked flask in a molar ratio of 1.2:1, add n-butanol with a mass fraction of 40 - 60%, control the reaction temperature at 80 - 100 °C, and reflux and react in a collecting type magnetic stirrer for 5 - 9 h to obtain product A.

[0067] Step S22: Subject the obtained product A to vacuum distillation, then wash out the pale yellow solid with acetone, and then recrystallize it 7 times with a mixed solution of acetone and acetonitrile with a volume ratio of 4:1 to obtain a white powder solid. Subsequently, place the white powder solid in a vacuum drying oven at 60 °C for drying to obtain the quaternary ammonium salt viscoelastic surfactant.

[0068] The quaternary ammonium salt viscoelastic surfactant has the property of shear thickening after reaching the critical micelle concentration, and also has the properties of reducing the oil-water interfacial tension and self-breaking gel in the presence of oil. The prepared quaternary ammonium salt viscoelastic surfactant is named SD. The quaternary ammonium salt viscoelastic surfactant prepared using hexadecyl bromide is collectively called SD-16, and the quaternary ammonium salt viscoelastic surfactant prepared using octadecyl bromide is collectively called SD-18.

[0069] Perform an orthogonal experiment on step S2, as shown in Table 3 and Table 4 specifically:

[0070] Table 3 Orthogonal Experiment

[0071]

[0072]

[0073] Table 4 Experimental Results

[0074] Serial number A B C D Yield % 1 A1 B1 C1 D1 74.36 2 A1 B2 C2 D2 79.64 3 A1 B3 C3 D3 85.22 4 A2 B1 C2 D3 81.23 5 A2 B2 C3 D1 79.96 6 A2 B3 C1 D2 85.54 7 A3 B1 C3 D2 88.32 8 A3 B2 C1 D3 82.65 9 A3 B3 C2 D1 84.18 Mean 1 79.74 81.3 80.85 79.5 - Mean 2 82.24 80.75 81.68 84.5 - Mean 3 85.05 84.98 84.5 83 - Range 5.31 4.23 3.65 5 -

[0075] As can be seen from the above table, the order of influence on the yield is: molar ratio of reactants > mass fraction of n-butanol% > reaction temperature / °C > reaction time / h.

[0076] The optimal condition combination is A3B3C3D2. The molar ratio of N,N-dimethylpropanolamine to hexadecyl bromide is 1.2:1, the mass fraction of n-butanol is 50%, react at 100 °C for 9 h. According to the experiment under the best condition combination, the yield measured under this condition is 91.35%.

[0077] Step S3: By weight, it includes the following components: 25 - 30 parts of sulfonated and aminated graphene, 1 - 2 parts of quaternary ammonium salt viscoelastic surfactant, 3 - 5 parts of sodium chloride, 5 - 7 parts of lower alcohol, and 55 - 65 parts of water. Mix them evenly to obtain the anti-swelling nano imbibition agent.

[0078] Among them, the lower alcohols are environmentally friendly and harmless materials, which can be those commonly used in the art, and can be selected from one or a combination of two or more of methanol, ethanol, n-propanol, and isopropanol. The salt promoter is a salt for reducing the surface tension.

[0079] Sulfonation treatment endows the amino-functionalized graphene with ion exchange properties. Salt ions undergo "adsorption and desorption" on the surface of sulfonated amino-functionalized graphene. Affected by high temperature, high salt, and the "aspect ratio" of graphene oxide, the surface charge distribution and osmotic pressure of amino-functionalized graphene are prone to unbalanced changes, resulting in aggregation and precipitation. The quaternary ammonium salt viscoelastic surfactant can be used in combination with it. On the one hand, it can utilize its steric hindrance effect and electrostatic stabilization to improve the dispersion performance of sulfonated amino-functionalized graphene under high temperature and high salt. On the other hand, it has a quaternary ammonium salt group. Therefore, the swelling inhibitor and reservoir fine particles are adsorbed to each other through hydrogen bonding and electrostatic interaction, forming a stable and uniform viscous molecular film on its surface, realizing in-situ fixation of formation fine sand or clay particles, and can act as a clay stabilizer. Among them, the dosage of the quaternary ammonium salt viscoelastic surfactant relative to sulfonated amino-functionalized graphene needs to be strictly controlled. Because the quaternary ammonium salt viscoelastic surfactant only has the effect of shear thickening after reaching the critical micelle concentration, too low dosage will make the carrying effect of the imbibition agent poor, and the improvement of the dispersion performance of sulfonated amino-functionalized graphene under high temperature and high salt is not obvious.

[0080] Example 1

[0081] The reagents used in this example are all commercially available reagents in the art: 1,5-dinitronaphthalene, purity: analytical grade. Glyoxal, purity: analytical grade. Malondialdehyde, purity: analytical grade. Sodium sulfanilate, purity: analytical grade. Ammonia water, GR, 25%-28%.

[0082] A preparation method of an anti-swelling nano-imbibition agent for fracturing shale reservoirs includes the following steps:

[0083] Step S1: Take 50 g of 1,5-dinitronaphthalene and disperse it in 300 mL of ammonia water, perform ultrasonic treatment (140 W, ultrasonic frequency 40 kHz) for 30 min, then seal the compound in a 1 L high-pressure reactor, heat it at 200 °C for 18 h. After cooling the product containing amino-functionalized graphene to room temperature, centrifuge it at 10000 rpm for 20 min, and further dialyze it for 2 days using a dialysis bag (cut-off molecular weight: 1000 Da) to remove unreacted small molecules, obtaining purified amino-functionalized graphene. Wash the centrifuged solid with distilled water 3 times and dry it at 80 °C to constant weight to obtain amino-functionalized graphene.

[0084] Step S2: Add 90 g of glyoxal and 250 g of sodium 3-aminobenzenesulfonate to 2 kg of distilled water, stir evenly with a magnetic stirrer, raise the temperature to 35 °C, and react for 10 h under magnetic stirring conditions. Wash the obtained solid by centrifugation (centrifugation speed at 6000 rpm) with distilled water, and repeat centrifugation 4 times. Dry at 80 °C for 3 h, disperse the obtained dried solid in water to obtain an aqueous glyoxal solution with sulfonic acid groups, which is hereinafter referred to as reagent (F) for short.

[0085] Step S3: Mix 2 kg of F solution with 100 g of amino-functionalized graphene evenly, and react for 10 h under magnetic stirring conditions at 30 °C. Wash the centrifuged solid with water 4 times and dry at 80 °C to constant weight to obtain sulfonated amino-functionalized graphene.

[0086] Step S4: Mix 50 g of sulfonated amino-functionalized graphene (effective content 85%), 2 g of viscoelastic surfactant SD-16 (effective content 80%), 10 g of ethanol, 7 g of sodium chloride, and 110 g of water evenly to obtain the anti-swelling nano-infiltration agent applicable to shale oil reservoirs.

[0087] Example 2

[0088] In step S2 of this example, the dosage of glyoxal is 80 g. The remaining steps are the same as those in Example 1.

[0089] Example 3

[0090] In step S2 of this example, malondialdehyde of equal mass is used to replace glyoxal. The remaining steps are the same as those in Example 1.

[0091] Example 4

[0092] In step S1 of this example, the dosage of 1,5-dinitronaphthalene is 55 g. The remaining steps are the same as those in Example 1.

[0093] Example 5

[0094] Step S1: Take 50 g of 1,5-dinitronaphthalene and disperse it in 300 mL of ammonia water, ultrasonicate it (power 140 W, ultrasonic frequency 40 kHz) for 30 min, then seal the compound in a 1 L high-pressure reactor, heat it at 200 °C for 18 h. After cooling the product containing amino-functionalized graphene to room temperature, centrifuge it at 10000 rpm for 20 min, and further dialyze it for 2 days using a dialysis bag (cut-off molecular weight: 1000 Da) to remove unreacted small molecules to obtain purified amino-functionalized graphene. Wash the centrifuged solid with water 4 times and dry at 80 °C to constant weight to obtain amino-functionalized graphene.

[0095] Step S2: Add 90 g of glyoxal and 250 g of sodium 3-aminobenzenesulfonate to 2 kg of distilled water, stir evenly with magnetic force, react for 10 h under stirring at 30°C, wash the obtained solid 4 times with distilled water and centrifuge (centrifugation speed at 6000 rpm), dry at 80°C for 3 h, and disperse the obtained solid in water to obtain reagent (F).

[0096] Step S3: Mix 2 kg of F solution evenly with 100 g of amino-functionalized graphene, react for 10 h under stirring at 30°C, wash the centrifuged solid 4 times with water, and dry at 80°C to constant weight to obtain sulfonated amino-functionalized graphene.

[0097] Step S4: Mix 50 g of sulfonated amino-functionalized graphene (effective content 85%), 2 g of viscoelastic surfactant SD-16 (effective content 80%), 10 g of ethanol, and 110 g of water evenly to obtain an anti-swelling nano-infiltration agent applicable to shale oil reservoirs.

[0098] Example VI

[0099] A preparation method of an anti-swelling nano-infiltration agent for fracturing in shale oil reservoirs, comprising the following steps:

[0100] Step S1: Take 50 g of 1,5-dinitronaphthalene and disperse it in 300 mL of ammonia water, perform ultrasonic treatment (140 W, ultrasonic frequency 40 kHz) for 30 min, then seal the compound in a 1 L high-pressure reactor, heat at 200°C for 18 h, cool the product containing amino-functionalized graphene to room temperature, centrifuge at 10000 rpm for 20 min, and further dialyze for 2 days using a dialysis bag (cut-off molecular weight: 1000 Da) to remove unreacted small molecules, obtain purified amino-functionalized graphene, wash the centrifuged solid 4 times with distilled water, and dry at 80°C to constant weight to obtain amino-functionalized graphene.

[0101] Step S2: Add 90 g of glyoxal and 250 g of sodium 2-aminobenzenesulfonate to 2 kg of distilled water, stir evenly, react for 10 h under magnetic stirring at 30°C, wash the obtained solid 4 times with distilled water and centrifuge (centrifugation speed at 6000 rpm), dry at 80°C for 3 h, and disperse the obtained solid in water to obtain solution (F).

[0102] Step S3: Mix 2 kg of F solution evenly with 100 g of amino-functionalized graphene, react for 10 h under magnetic stirring at 30°C, wash the centrifuged solid 3 times with water, and dry at 80°C to constant weight to obtain sulfonated amino-functionalized graphene.

[0103] Step S4: Mix 50 g of sulfonated and aminated graphene (effective content: 85%), 2 g of viscoelastic surfactant SD-16 (effective content: 80%), 7 g of sodium chloride, 10 g of ethanol, and 110 g of water uniformly to obtain the swelling prevention nano imbibition agent applicable to shale reservoirs.

[0104] Comparative Example 1

[0105] The remaining steps are the same as those in Example 1, except that in Step S3, the dosage of solution F is 1 kg.

[0106] Comparative Example 2

[0107] The rest is the same as in Example 1, except that in Step S4, alkyltrimethylammonium chloride (purchased as a finished product) with an equimolar amount is used to replace SD-16.

[0108] Comparative Example 3

[0109] A preparation method of a swelling prevention nano imbibition agent for fracturing in shale reservoirs includes the following steps:

[0110] Step S1: Take 50 g of 1,5-dinitronaphthalene and disperse it in 300 mL of ammonia water, perform ultrasonic treatment (140 W, ultrasonic frequency 40 kHz) for 30 min, then seal the compound in a 1 L high-pressure reactor, heat it at 200 °C for 18 h. After cooling the product containing aminated graphene to room temperature, centrifuge it at 10000 rpm for 20 min, and further dialyze it for 2 days using a dialysis bag (cut-off molecular weight: 1000 Da) to remove unreacted small molecules, obtain purified aminated graphene, wash the centrifuged solid 4 times with distilled water, and dry it at 80 °C to constant weight to obtain aminated graphene.

[0111] Step S2: Mix 50 g of aminated graphene (effective content: 85%), 2 g of viscoelastic surfactant SD-16 (effective content: 80%), 7 g of sodium chloride, 10 g of ethanol, and 110 g of water uniformly to obtain the swelling prevention nano imbibition agent.

[0112] That is, compared with Example 1, the aminated graphene in this comparative example is not sulfonated and modified.

[0113] Perform the following performance tests on the swelling prevention nano imbibition agents prepared in the above examples and comparative examples:

[0114] 1. Swelling prevention performance.

[0115] The centrifugation method is used to measure the swelling prevention rate of the swelling prevention and shrinking agent.

[0116] Measurement of the swelling prevention rate: Add 0.5 g of bentonite and 10 mL of 10% swelling prevention agent aqueous solution into a centrifuge tube, mix uniformly and let it stand for 3 h, and read the clay volume as V after high-speed centrifugation.1 Under the same conditions, a comparative experiment was conducted. Only the 10 mL swelling prevention and shrinking swelling agent aqueous solution was replaced with Wahaha purified water, and the clay volume was read again as V 2 .

[0117]

[0118] 2. Temperature and salt tolerance performance.

[0119] Mineralized water was prepared separately, as shown in Table 5, and the salinity was

[0120] Table 5 Mineralized water

[0121]

[0122]

[0123] The swelling prevention nano imbibition agent (oil displacement agent) prepared in the examples and comparative examples was added to the mineralized water to prepare an oil displacement agent solution with a mass fraction of 0.3%. The oil displacement agent solution was heated to 150 °C and aged for 6 days, and the apparent viscosity before and after aging was measured with a HAAK Viscoteste 3 rotational viscometer at a shear rate of 8 s for 30 min -1 , and the apparent viscosity retention rate at each salinity was calculated.

[0124] 3. Recovery factor.

[0125] a. The nano imbibition displacement agent was added to the simulated formation water to prepare an oil displacement agent solution with a mass concentration of 0.4%.

[0126] b. Saturating with water: An artificial homogeneous core (diameter 2.5 cm, length 30 cm, permeability 10×10 -3 μm 2 ) was evacuated and saturated with mineralized water.

[0127] c. Saturating with oil: Saturated kerosene (viscosity 2.2 mPa·s) at 90 °C was injected into the core at a flow rate of 0.1 mL / min, and the volume of crude oil saturated into the core was recorded after the saturation with oil was completed. After standing for 24 h, it was taken out and the initial oil saturation was calculated.

[0128] d. Water flooding: Water flooding (simulated formation water, displacement velocity 0.1 mL / min) was carried out until the water cut reached 98%, and the recovery factor g at a water cut of 98% was recorded.

[0129] e. Injecting the oil displacement agent: Injecting 0.5 PV of the oil displacement agent solution and subsequent water flooding until the water cut reached 98%, recording the cumulative recovery factor h, and calculating the displacement agent recovery factor i, i = h - g.

[0130] Table 6 Ion composition of simulated formation water

[0131]

[0132] Table 7 Performance test results

[0133]

[0134] It can be seen from the anti-swelling rate in Table 7 that the anti-swelling effect of SD-16 is better than that of SD-18, and the anti-swelling rates are all higher than 80%. From the test results of the recovery rate, it can be seen that after sulfonation of the amino-functionalized graphene in the present invention, the recovery rate has increased from 31.3% of the unsulfonated one to more than 37.1%, indicating that the displacing agent has an excellent function of improving the recovery rate.

[0135] It can be seen from the test results of the temperature and salt tolerance performance that after high salinity and high temperature aging, the viscosity retention rate is high, and there is no significant viscosity reduction, indicating that the displacing agent provided by the present invention has good temperature and salt tolerance performance. It can be seen from the test results of the temperature and salt tolerance performance of the examples and comparative examples that sulfonated amino-functionalized graphene has the effect of synergistically improving the temperature and salt tolerance performance of the displacing agent with the viscoelastic surfactant SD.

[0136] Therefore, the present invention adopts the above-mentioned anti-swelling nano-infiltration agent for fracturing shale reservoirs, its preparation method and application. By using the shear thickening of the quaternary ammonium salt viscoelastic surfactant during the reservoir migration process in combination with sulfonated amino-functionalized graphene, the infiltration and oil displacement effect and anti-swelling performance of the nano-infiltration displacing agent can be significantly improved.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An anti-swelling nano-imbibition agent for shale oil reservoir fracturing, characterized in that: The composition comprises the following components by weight: 25-30 parts of sulfonated aminated graphene, 1-2 parts of quaternary ammonium salt viscoelastic surfactant, 3-5 parts of salt dissolution promoter, 5-7 parts of low-carbon alcohol and 55-65 parts of water.

2. The anti-swelling nano-imbibing agent for shale oil reservoir fracturing according to claim 1, characterized in that: The low-carbon alcohol includes but is not limited to one or a combination of two or more of methanol, ethanol, n-propanol, and isopropanol; the salt solubilizing agent includes but is not limited to sodium chloride.

3. A method for preparing the anti-swelling nano-imbibing agent for shale oil reservoir fracturing according to any one of claims 1 to 2, characterized in that: The following steps are involved: Step S1, preparing sulfonated aminated graphene; Step S2, preparing a quaternary ammonium salt viscoelastic surfactant; Step S3, uniformly mix the sulfonated aminated graphene, the quaternary ammonium salt viscoelastic surfactant, the low-carbon alcohol, the salt solubilizing agent, and water according to the above proportions to obtain the anti-swelling nano-infiltrator.

4. The method for preparing an anti-swelling nano-imbibing agent for shale oil reservoir fracturing according to claim 3, characterized in that: Step S1 specifically comprises: Step S11, dispersing 1,5-dinitronaphthalene in ammonia water, performing ultrasonication, heating, centrifugation, dialysis, washing, and drying to obtain amino graphene; Step S12, dispersing the dialdehyde compound and the sodium p-aminobenzenesulfonate derivative in distilled water, heating, centrifuging, washing, and drying, and dispersing the solid in water to obtain an aqueous solution of the dialdehyde compound with a sulfonate group; Step S13, adding the aminated graphene and the aqueous solution of the dialdehyde compound with a sulfonate group to distilled water and mixing them evenly, reacting them under the condition of heating and magnetic stirring, and after the reaction is completed, distilling under reduced pressure, filtering, washing and drying to obtain the sulfonated aminated graphene.

5. The method for preparing an anti-swelling nano-imbibing agent for shale oil reservoir fracturing according to claim 4, characterized in that: In step S11, the heating condition is to react at 180-220° C. for 18-22 hours; the centrifugal speed is 8000-10000 rpm; the dialysis is to use a dialysis bag for 48 hours to remove unfused small molecules, wherein the molecular weight cutoff is 1000 Da; the washing is to wash the solid obtained by centrifugation with distilled water 3-5 times; the drying is to dry at a temperature of 60-100° C. to constant weight; The concentration of ammonia water is 25-28wt%; the mass ratio of 1,5-dinitronaphthalene to ammonia water is 1:6-1:4; The particle size of amino graphene in water is 26-30nm and the thickness is 0.2-2nm.

6. The method for preparing an anti-swelling nano-imbibing agent for shale oil reservoir fracturing according to claim 4, characterized in that: In step S12, the dialdehyde compounds include but are not limited to glyoxal and malondialdehyde; The molar ratio of the dialdehyde compound to the sodium p-aminobenzenesulfonate derivative is 6:5-1:1; The sodium aminobenzenesulfonate derivative is one of sodium 2-aminobenzenesulfonate and sodium 3-aminobenzenesulfonate or a combination of two or more thereof.

7. The method for preparing an anti-swelling nano-imbibing agent for shale oil reservoir fracturing according to claim 4, characterized in that: In step S12, the heating conditions are 35-40°C for a reaction time of 8-12 hours; the centrifugal speed is 6000-8000 rpm; the washing is washing the solid obtained by centrifugation with distilled water for 3-5 times; and the drying conditions are drying at 80°C for 3 hours.

8. The method for preparing an anti-swelling nano-imbibing agent for shale oil reservoir fracturing according to claim 4, characterized in that: In step S13, the mass ratio of the aqueous solution of the dialdehyde compound having a sulfonate group to the aminated graphene is 20:0.5-1.5; The temperature is raised to 30-40°C, and the reaction time is 8-12h; washing is repeated 4 times with distilled water; and drying is performed at 80°C to constant weight.

9. The method for preparing an anti-swelling nano-imbibing agent for shale oil reservoir fracturing according to claim 3, characterized in that: Step S2 specifically includes: Step S21, adding N,N-dimethylpropanolamine and bromoalkane in a molar ratio of 1.2-1.4:1 into a three-necked flask, adding 40-60% by mass of n-butanol, controlling the reaction temperature to 80-100° C., and reflux reacting in a heat-collecting magnetic stirrer for 5-9 hours to obtain product A; Wherein, bromoalkanes include but are not limited to hexadecane and octadecane; Step S22, distill the obtained product A under reduced pressure, wash out the light yellow solid with acetone, and then recrystallize it 7 times with a mixed solution of acetone and acetonitrile in a volume ratio of 4:1 to obtain a white powder solid, and then dry the white powder solid in a vacuum drying oven at a temperature of 60°C to obtain a quaternary ammonium salt viscoelastic surfactant.

10. Use of the anti-swelling nano-imbibition agent for shale oil reservoir fracturing as claimed in any one of claims 1 to 2 as a nano-imbibition displacement agent for shale oil reservoirs.

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