Modified nano-graphite for crosslinking in deep oil and gas reservoirs and nano-graphite hybrid crosslinked gel plugging agent and preparation method thereof

Abstract

The present invention relates to the technical field of oilfield chemical profile control and water plugging, and discloses a modified nano-graphite for crosslinking and a nano-graphite hybrid crosslinked gel plugging agent for deep oil and gas reservoirs and a preparation method thereof. The modified nano-graphite for crosslinking is obtained by modifying natural nano-graphite with an aryl sulfonic acid active free radical to obtain preliminarily modified nano-graphite; the preliminarily modified nano-graphite is crosslinked with an aryl hydroxyl active free radical. By directly participating in the hybrid crosslinking reaction of the modified nano-graphite, the crosslinking density and chemical bond energy of the hybrid crosslinked gel are improved, and a hybrid crosslinked gel plugging agent with high temperature resistance (≥130 °C), high salt resistance (≥200,000 mg / L), long-term thermal stability, and capable of adapting to the heterogeneous control of deep oil and gas reservoir formations is developed.

Description

Technical Field

[0001] The present invention belongs to the technical field of oilfield chemical profile control and water plugging, and particularly relates to a modified nano-graphite and nano-graphite hybrid crosslinked gel plugging agent for deep oil and gas reservoirs and a preparation method thereof. Background Technique

[0002] Water injection / gas injection is a relatively mature development technology for deep oil and gas reservoirs, while ultra-deep oil and gas reservoirs still mainly adopt depletion development technology. However, affected by reservoir heterogeneity, water channeling and gas channeling restrict the efficient development of deep oil and gas reservoirs. Reservoir heterogeneity control has become an effective way to inhibit water channeling and gas channeling in deep oil and gas reservoirs, and the core is a high-temperature and high-salt resistant plugging agent. Gel-type plugging agents have become widely used plugging agents because of their adjustable gelation time, controllable gelation strength, and simple preparation. However, due to the complex conditions of deep oil and gas reservoirs, such as deep burial (≥2500 m), high temperature (≥110 °C), high salinity (Na + ≥100,000 mg / L), high hardness (Ca 2+ , Mg 2+ ≥2000 mg / L), etc., traditional gels are prone to dehydration and have low water plugging efficiency, making them difficult to apply in deep oil and gas reservoirs. Therefore, it is urgent to develop high-temperature and high-salt resistant gels to meet the regulation of reservoir heterogeneity in deep oil and gas reservoirs.

[0003] CN113897189A discloses a gel system suitable for profile control of high-temperature and high-salt fracture-cavity type oil reservoirs, which is composed of an AM / AMPS copolymer, a non-ionic polyacrylamide, hexamethylenetetramine, hydroquinone and the balance of water. This system has good stability and gelation strength under the conditions of 130 °C and 220,000 mg / L, and at the same time, the gelation time is controllable and it is less affected by formation water dilution. This gel system is only composed of organic materials and has good application potential under the investigated test conditions, and does not involve nano-graphite hybrid crosslinking reaction.

[0004] CN108300440A discloses a bulk gel system, a composition and a preparation method and application thereof strengthened by nano-graphite emulsion for gel dispersion. This system is composed of a polymer matrix, a resin crosslinking agent, a coagulant and nano-graphite emulsion, and can form a high-strength bulk gel system within 85 - 95 °C and 3 - 6 hours. This nano-graphite emulsion does not involve hybrid crosslinking reaction, and is only a rapidly crosslinked gel formed after physical doping. In addition, this bulk gel plugging agent forms gel on the ground and does not involve in-situ gel formation.

[0005] CN111040750A discloses a composite temperature-resistant gel plugging agent, its preparation method, and its application in profile control and water plugging of ultra-deep reservoirs. It is composed of a modified nano-graphite / polyacrylamide composite material, a phenolic cross-linking agent, an aldehyde cross-linking agent, and a liquid preparation water. The gelation time can be controlled within 6 - 48 hours, and after gelation, it has high strength and strong stability. It is suitable for heterogeneous regulation of ultra-deep reservoirs with reservoir temperatures of 130°C - 180°C and salinity up to 200,000 mg / L. The modified nano-graphite undergoes a polymerization reaction by contacting with acrylamide monomers to obtain a modified nano-graphite / polyacrylamide composite material, and then the composite material reacts with the cross-linking agent to form a gel system. However, in this reaction, the modified nano-graphite is one of the raw materials for synthesizing the polymer composite material and does not involve cross-linking reactions. Summary of the Invention

[0006] Aiming at the problem of insufficient temperature and salt resistance of existing gel-type plugging agents for deep oil and gas reservoirs, a modified nano-graphite for cross-linking and a nano-graphite hybrid cross-linked gel plugging agent for deep oil and gas reservoirs and their preparation methods are provided. By directly participating in the hybrid cross-linking reaction of the modified nano-graphite, the cross-linking density and chemical bond energy of the hybrid cross-linked gel are improved, and a hybrid cross-linked gel plugging agent with high temperature resistance (≥130°C), high salt resistance (≥200,000 mg / L), and long-term thermal stability, which can adapt to the heterogeneous regulation of deep oil and gas reservoir formations, is developed. It is mainly applied to the heterogeneous regulation of deep oil and gas reservoir formations and also meets the heterogeneous regulation of some ultra-deep oil and gas reservoir formations.

[0007] To achieve the above object, in the first aspect of the present invention, a modified nano-graphite for cross-linking is provided, wherein the modified nano-graphite for cross-linking is obtained by modifying natural nano-graphite with a sulfonic acid aryl active radical to obtain a preliminarily modified nano-graphite; the preliminarily modified nano-graphite is cross-linked with a hydroxy aryl active radical.

[0008] In the second aspect of the present invention, a preparation method of the aforementioned modified nano-graphite for cross-linking is provided, wherein the preparation method includes:

[0009] (a) Disperse the diazonium salt of sulfanilic acid shown in formula (2) in deionized water to release nitrogen to obtain a dispersion liquid containing sulfonic acid aryl active radicals;

[0010] (b) Contact the dispersion liquid in step (a) with natural nano-graphite shown in formula (3) to obtain a preliminarily modified nano-graphite solution;

[0011] (c) Wash, dry, and grind and disperse the preliminarily modified nano-graphite solution to obtain preliminarily modified nano-graphite;

[0012] (d) Disperse the aminophenol diazonium salt shown in any one of formulas (4)-(6) in deionized water to release nitrogen gas to obtain a dispersion containing hydroxyaryl active radicals;

[0013] (e) Contact the dispersion described in step (d) with the preliminarily modified nano-graphite described in step (c) to obtain a modified nano-graphite solution for crosslinking;

[0014] (f) Wash, dry and grind and disperse the modified nano-graphite solution for crosslinking to obtain modified nano-graphite for crosslinking;

[0015]

[0016] The third aspect of the present invention provides a nano-graphite hybrid crosslinked gel plugging agent for deep oil and gas reservoirs, wherein the hybrid crosslinked gel plugging agent includes the modified nano-graphite for crosslinking described above.

[0017] The fourth aspect of the present invention provides a preparation method of the nano-graphite hybrid crosslinked gel plugging agent for deep oil and gas reservoirs described above, wherein the preparation method includes:

[0018] (a1) Disperse the chelating agent in the liquid preparation water;

[0019] (b1) Disperse the modified nano-graphite for crosslinking in the liquid preparation water to obtain a dispersion of modified nano-graphite for crosslinking; wherein, the modified nano-graphite for crosslinking is the modified nano-graphite for crosslinking described above;

[0020] (c1) Contact polyacrylamide with the dispersion of modified nano-graphite for crosslinking;

[0021] (d1) Contact the aldehyde crosslinking agent with the solution obtained in step (c1);

[0022] (e1) Contact the phenolic crosslinking agent with the solution obtained in step (d1) to obtain a gelling solution;

[0023] (f1) Carry out a crosslinking reaction on the gelling solution to obtain a nano-graphite hybrid crosslinked gel plugging agent for deep oil and gas reservoirs.

[0024] Through the above technical solutions, compared with the prior art, the present invention has the following advantages:

[0025] (1) The modified nano-graphite for crosslinking of the present invention is prepared by a diazotization reaction, has hydroxyl groups and sulfonic acid groups, can directly participate in the hybrid crosslinking reaction, and has a simple synthesis method, mild reaction conditions, simple operation, and is convenient for industrial production.

[0026] (2) Compared with the simple physical doping of previous nanomaterials, the modified nano-graphite for crosslinking in the present invention can directly participate in the crosslinking reaction, and by increasing the crosslinking density and enhancing the crosslinking bond energy, significantly improve the temperature and salt resistance performance of the hybrid gel plugging agent.

[0027] (3) The deep reservoir hybrid crosslinked gel plugging agent of the present invention is applicable to the heterogeneous regulation of reservoirs with temperatures of 130°C - 150°C and salinities of 200,000 - 300,000 mg / L. The gelation time can be controlled within 4 - 24 hours, and after gelation, it has high strength and strong thermal stability.

[0028] (4) The components of the deep reservoir hybrid crosslinked gel plugging agent have good compatibility with each other, and the preparation of the gelling solution is simple. It can be prepared with either fresh water or re-injected water that meets the standards of the oilfield, alleviating the problem of shortage of fresh water resources during complex and demanding construction processes such as in coastal beaches and deserts.

[0029] (5) The raw materials of the modified nano-graphite for crosslinking in deep reservoirs and its hybrid crosslinked gel plugging agent have a wide range of sources, and are suitable for industrial production and large-scale on-site preparation operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the infrared spectrum of the modified nano-graphite for crosslinking in Example 1;

[0031] Figure 2 is the initial state of the nano-graphite hybrid crosslinked gel plugging agent after gelation in Example 4;

[0032] Figure 3 is the state of the nano-graphite hybrid crosslinked gel plugging agent after 60 days of aging in Example 4;

[0033] Figure 4 is the initial state of the deep reservoir gel plugging agent after gelation in Comparative Example 1;

[0034] Figure 5 is the state of the deep reservoir gel plugging agent after 60 days of aging in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0035] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0036] As mentioned above, the first aspect of the present invention provides a modified nanographite for crosslinking, wherein the modified nanographite for crosslinking is obtained by modifying natural nanographite with active free radicals containing sulfonic acid aromatic groups to obtain preliminary modified nanographite; and the preliminary modified nanographite is obtained by crosslinking with active free radicals containing hydroxyl aromatic groups.

[0037] According to the present invention, the active free radical containing sulfonic acid aromatic group is

[0038] According to the present invention, the active free radical containing hydroxyl aromatic group is One or more of .

[0039] According to the present invention, based on the total weight of free radicals included in the modified nanographite for cross-linking, the content of the active free radicals containing sulfonic acid aromatic groups is 20-40%; the content of the active free radicals containing hydroxy aromatic groups is 20-40%.

[0040] According to the present invention, preferably, the structure of the modified nanographite for cross-linking includes one or more structures shown in formula (I) to formula (III);

[0041]

[0042] According to the present invention, the cross-linking modified nanographite has a sheet diameter of 1-3 μm and a thickness of 1-5 nm.

[0043] The second aspect of the present invention provides a method for preparing the aforementioned modified nanographite for cross-linking, wherein the preparation method comprises:

[0044] (a) dispersing the diazonium salt of p-aminobenzenesulfonic acid represented by formula (2) in deionized water to release nitrogen to obtain a dispersion containing sulfonic acid aromatic active free radicals;

[0045] (b) contacting the dispersion of step (a) with natural nanographite represented by formula (3) to obtain a preliminary modified nanographite solution;

[0046] (c) washing, drying and grinding the preliminary modified nanographite solution to obtain preliminary modified nanographite;

[0047] (d) dispersing an aminophenol diazonium salt represented by any one of formulas (4) to (6) in deionized water to release nitrogen to obtain a dispersion containing hydroxyl aromatic active free radicals;

[0048] (e) contacting the dispersion of step (d) with the preliminarily modified nanographite of step (c) to obtain a modified nanographite solution for crosslinking;

[0049] (f) washing, drying and grinding the modified nanographite solution for cross-linking to obtain modified nanographite for cross-linking;

[0050]

[0051] According to the present invention, in (a), the method for preparing the dispersion containing sulfonic acid aromatic active free radicals comprises:

[0052] (a-1) contacting p-aminobenzenesulfonic acid, sodium hydroxide and deionized water to obtain a first mixed solution;

[0053] (a-2) contacting the first mixed solution with sodium nitrite under ice-salt bath conditions to obtain a second mixed solution;

[0054] (a-3) adding hydrochloric acid dropwise to the second mixed solution to obtain the diazonium salt of p-aminobenzenesulfonic acid represented by formula (2);

[0055] (a-4) The diazonium p-aminobenzenesulfonic acid salt releases nitrogen molecules to form a dispersion containing sulfonic acid aromatic radicals.

[0056] According to the present invention, in (a-2), the conditions of the ice-salt bath include: a temperature of 0-8°C, preferably 0-5°C.

[0057] According to the present invention, in (a-3), the conditions for the dropwise addition include: a temperature of 0-8°C, preferably 0-5°C.

[0058] According to the present invention, in (a-4), the conditions for releasing nitrogen molecules include: maintaining the diazonium salt of p-aminobenzenesulfonic acid at a temperature of 0-8°C, preferably maintaining it at a temperature of 0-5°C.

[0059] According to the present invention, the weight ratio of p-aminobenzenesulfonic acid, sodium hydroxide, deionized water, sodium nitrite and hydrochloric acid is (1-2): (1-2): (60-80): (0.8-1.6): (3-6).

[0060] According to a preferred embodiment of the present invention, in (a), the method for preparing the dispersion containing sulfonic acid aromatic active free radicals comprises:

[0061] Step (i): dissolve 1-2 g of p-aminobenzenesulfonic acid and 1-2 g of sodium hydroxide in 60-80 g of deionized water;

[0062] Step (ii): place the p-aminobenzenesulfonic acid and sodium hydroxide aqueous solution in step (i) in a 0-8°C ice-salt bath and add 0.8g-1.6g of sodium nitrite thereto;

[0063] Step (III): Maintain the mixed solution obtained in step (II) at 0 - 8°C, and slowly add dropwise 10 - 20 g of hydrochloric acid with a mass fraction of 30% to obtain the diazonium salt of sulfanilic acid of formula (2).

[0064] Step (IV): Maintain the diazonium salt of sulfanilic acid obtained in step (III) at 0 - 8°C to form an aqueous solution containing sulfonic acid aryl radicals by releasing nitrogen molecules.

[0065] According to the present invention, in (d), the method for preparing the dispersion liquid containing hydroxyaryl active radicals includes:

[0066] (d - 1) Contact aminophenol, sodium hydroxide, and deionized water to obtain a third mixed solution;

[0067] (d - 2) Mix the third mixed solution with sodium nitrite to obtain a fourth mixed solution;

[0068] (d - 3) Add dropwise hydrochloric acid to the fourth mixed solution to obtain a diazonium salt of aminophenol shown in any one of formulas (4) - (6);

[0069] (d - 4) Form a dispersion liquid containing hydroxyaryl radicals by releasing nitrogen molecules from the diazonium salt of aminophenol.

[0070] According to the present invention, in (d - 3), the conditions for the dropwise addition include: the temperature is 0 - 8°C, preferably 0 - 5°C.

[0071] According to the present invention, in (d - 4), the conditions for releasing nitrogen molecules include: maintaining the diazonium salt of sulfanilic acid at a temperature of 0 - 8°C, preferably at a temperature of 0 - 5°C.

[0072] According to the present invention, the weight ratio of the amounts of aminophenol, sodium hydroxide, deionized water, sodium nitrite, and hydrochloric acid used is (1 - 2):(1 - 2):(60 - 80):(0.8 - 1.6):(3 - 6).

[0073] According to a preferred specific embodiment of the present invention, in (d), the method for preparing the dispersion liquid containing hydroxyaryl active radicals includes:

[0074] Step (I): Dissolve 1 - 2 g of aminophenol and 1 - 2 g of sodium hydroxide in 60 - 80 g of deionized water;

[0075] Step (II): Place the aqueous solution of aminophenol and sodium hydroxide obtained in step (I) in an ice - salt bath at 0 - 8°C and add 0.8 g - 1.6 g of sodium nitrite thereto;

[0076] Step (III): Maintain the mixed solution obtained in Step (II) at 0 - 5 °C, and slowly add dropwise 10 - 20 g of hydrochloric acid with a mass fraction of 30% to obtain the diazonium salt of 2 - aminophenol of formula (2).

[0077] Step (IV): Maintain the diazonium salt of aminophenol obtained in Step (III) at 0 - 8 °C to form an aqueous solution containing hydroxyaryl radicals by releasing nitrogen molecules.

[0078] According to the present invention, in Step (a), the dispersion conditions include: a stirring rate of 400 - 800 revolutions per minute, a temperature of 0 - 8 °C, and a time of 1 - 6 h; preferably, the stirring rate is 500 - 600 revolutions per minute, the temperature is 0 - 5 °C, and the time is 2 - 4 h.

[0079] According to the present invention, in Step (b), the contact conditions include: a stirring rate of 400 - 800 revolutions per minute, a temperature of 0 - 8 °C, and a time of 4 - 10 h; preferably, the stirring rate is 500 - 600 revolutions per minute, the temperature is 0 - 5 °C, and the time is 6 - 8 h.

[0080] According to the present invention, in Step (c), the drying conditions include: a temperature of 35 - 50 °C; and washing with a mixed solution of deionized water and ethanol; wherein, the volume ratio of deionized water to ethanol in the mixed solution is 1:(1 - 1.5); preferably 1:1.

[0081] According to the present invention, in Step (d), the dispersion conditions include: a stirring rate of 400 - 800 revolutions per minute, a temperature of 0 - 8 °C, and a time of 1 - 6 h; preferably, the stirring rate is 500 - 600 revolutions per minute, the temperature is 0 - 5 °C, and the time is 2 - 4 h.

[0082] According to the present invention, in Step (e), the contact conditions include: a stirring rate of 400 - 800 revolutions per minute, a temperature of 0 - 8 °C, and a time of 4 - 10 h; preferably, the stirring rate is 500 - 600 revolutions per minute, the temperature is 0 - 5 °C, and the time is 6 - 8 h.

[0083] According to the present invention, in Step (f), the drying conditions include: a temperature of 35 - 50 °C; and washing with a mixed solution of deionized water and ethanol; wherein, the volume ratio of deionized water to ethanol in the mixed solution is 1:(1 - 1.5); preferably 1:1.

[0084] According to the present invention, the monomer shown in formula (3) is natural nano - graphite, that is, unmodified nano - graphite, which can also be called bulk nano - graphite. In the present invention, the size of natural nano - graphite is 0.5 - 2 μm, and the sheet thickness is 1 - 3 nm.

[0085] According to a preferred specific embodiment of the present invention, the preparation method of the crosslinking modified nano-graphite includes:

[0086] At room temperature (20±5°C), p-aminobenzenesulfonic acid is first added to deionized water, and sodium hydroxide is added under the condition that the stirring rate is 400 - 800 revolutions per minute and stirred for 10 - 30 minutes, and then sodium nitrite is added at an ice-salt bath temperature of 0 - 8°C and stirred for 10 - 30 minutes. Hydrochloric acid is slowly added under the condition that the stirring rate is 400 - 800 revolutions per minute and the ice-salt bath temperature is 0 - 8°C and stirred for 1 - 5 h to obtain a sulfonic acid aryl radical dispersion; natural nano-graphite powder shown in formula (3) is added while stirring, and stirring is continued for 6 - 8 h at an ice-salt bath temperature of 0 - 8°C to obtain a preliminarily modified nano-graphite dispersion; the solution obtained above is washed three times with a mixed solution of deionized water and alcohol in a ratio of 1:1 to remove unreacted sulfonic acid aryl radicals; the washed solution is placed in an oven at 35°C for drying, ground and dispersed to obtain preliminarily modified nano-graphite particles; and then at room temperature (20±5°C), aminophenol is first added to deionized water, and sodium hydroxide is added under the condition that the stirring rate is 400 - 800 revolutions per minute and stirred for 10 - 30 minutes, and then sodium nitrite is added at an ice-salt bath temperature of 0 - 8°C and stirred for 10 - 30 minutes. Hydrochloric acid is slowly added under the condition that the stirring rate is 400 - 800 revolutions per minute and the ice-salt bath temperature is 0 - 8°C and stirred for 1 - 5 h to obtain a hydroxyl aryl radical dispersion; the above-mentioned preliminarily modified nano-graphite particles are added while stirring, and stirring is continued for 6 - 8 h at an ice-salt bath temperature of 0 - 8°C to obtain crosslinking modified nano-graphite; the solution obtained above is washed three times with a mixed solution of deionized water and alcohol in a ratio of 1:1 to remove unreacted hydroxyl aryl radicals; the washed solution is placed in an oven at 35°C for drying, ground and dispersed to obtain crosslinking modified nano-graphite.

[0087] The present invention also provides a crosslinking modified nano-graphite prepared by the aforementioned method.

[0088] The third aspect of the present invention provides a nano-graphite hybrid crosslinked gel plugging agent for deep oil and gas reservoirs, wherein the hybrid crosslinked gel plugging agent includes the aforementioned crosslinking modified nano-graphite.

[0089] According to the present invention, the deep oil and gas reservoir hybrid crosslinked gel plugging agent includes one or more of preparation water, polyacrylamide, crosslinking modified nano-graphite, aldehyde crosslinking agent, phenolic crosslinking agent, and chelating agent.

[0090] In the present invention, the "preparation water" is simulated brine with a salinity of 200,000 - 300,000 mg / L.

[0091] According to the present invention, the polyacrylamide is an AM / AMPS copolymer, one or a combination of non-ionic polyacrylamides. The weight-average molecular weight of the AM / AMPS copolymer is 8 million - 10 million g / mol, the hydrolysis degree is 3% - 4%, and the AM / AMPS content is 30% - 40%; the relative molecular weight of the non-ionic polyacrylamide is 5 million - 8 million, and the hydrolysis degree is 2% - 10%.

[0092] According to the present invention, the aldehyde crosslinking agent is one or a combination of hexamethylenetetramine and formaldehyde.

[0093] According to the present invention, the phenolic crosslinking agent is one or a combination of hydroquinone, resorcinol, and catechol; the chelating agent is one or a combination of ethylenediaminetetraacetic acid, sodium nitrite, and sodium formate.

[0094] According to the present invention, based on the total weight of the hybrid crosslinked gel plugging agent, the dosage of the modified nano-graphite for crosslinking is 0.05 - 0.2 wt%, the dosage of the polyacrylamide is 0.3 - 0.8 wt%, the dosage of the aldehyde crosslinking agent is 0.2 - 0.8 wt%, the dosage of the phenolic crosslinking agent is 0.2 - 0.6 wt%, the dosage of the chelating agent is 1 - 3 wt%, and the dosage of the liquid preparation water is 94.8 - 96.7 wt%.

[0095] According to the present invention, preferably, based on the total weight of the hybrid crosslinked gel plugging agent, the dosage of the modified nano-graphite for crosslinking is 0.1 - 0.2 wt%, the dosage of the aldehyde crosslinking agent is 0.4 - 0.6 wt%, the dosage of the phenolic crosslinking agent is 0.4 - 0.6 wt%, the dosage of the polyacrylamide is 0.4 - 0.8 wt%, the dosage of the chelate is 2 - 3 wt%, and the dosage of the liquid preparation water is 94.8 - 96.7 wt%.

[0096] The fourth aspect of the present invention provides a preparation method of the deep oil and gas reservoir nano-graphite hybrid crosslinked gel plugging agent described above, wherein the preparation method includes:

[0097] (a1) Disperse the chelating agent in the liquid preparation water;

[0098] (b1) Disperse the modified nano-graphite for crosslinking in the liquid preparation water to obtain a dispersion liquid of the modified nano-graphite for crosslinking; wherein, the modified nano-graphite for crosslinking is the modified nano-graphite for crosslinking described above;

[0099] (c1) Contact the polyacrylamide with the dispersion liquid of the modified nano-graphite for crosslinking;

[0100] (d1) Contact the aldehyde crosslinking agent with the solution obtained in step (c1);

[0101] (e1) Contact the phenolic crosslinking agent with the solution obtained in step (d1) to obtain a gel-forming solution;

[0102] (f1) Carry out a crosslinking reaction on the gel-forming solution to obtain a deep reservoir nano-graphite hybrid crosslinked gel plugging agent.

[0103] According to the present invention, in step (a1), the dispersion conditions include: a stirring rate of 500 - 600 revolutions per minute, a temperature of normal temperature (20 ± 5 °C), and a time of 10 - 20 minutes;

[0104] According to the present invention, in step (b1), the dispersion conditions include: a stirring rate of 500 - 600 revolutions per minute, a temperature of normal temperature (20 ± 5 °C), and a time of 30 - 50 minutes.

[0105] According to the present invention, in step (c1), the contact conditions include: a stirring rate of 500 - 600 revolutions per minute, a temperature of normal temperature (20 ± 5 °C), and a time of 90 - 120 minutes.

[0106] According to the present invention, in step (d1), the contact conditions include: a stirring rate of 500 - 600 revolutions per minute, a temperature of normal temperature (20 ± 5 °C), and a time of 20 - 30 minutes.

[0107] According to the present invention, in step (e1), the contact conditions include: a stirring rate of 500 - 600 revolutions per minute, a temperature of normal temperature (20 ± 5 °C), and a time of 20 - 30 minutes.

[0108] According to the present invention, in step (f1), place the gel-forming solution at a certain temperature for crosslinking reaction, wherein the crosslinking reaction conditions include: a temperature of 130 - 150 °C and a time of 4 - 24 h.

[0109] According to a preferred embodiment of the present invention, the preparation method of the deep reservoir modified nano-graphite hybrid crosslinked gel plugging agent includes:

[0110] At room temperature (20 ± 5°C), first add a chelating agent with a weight fraction of 2% - 3% to the preparation water, and stir for 10 - 20 minutes under the condition that the stirring rate is 500 - 600 revolutions per minute to obtain a uniformly dispersed solution; while stirring, add a modified nano - graphite for cross - linking with a weight fraction of 0.1% - 0.2%, and stir for 30 - 50 minutes until it dissolves to obtain a modified nano - graphite solution for cross - linking; then while stirring, add a polymer with a weight fraction of 0.4% - 0.8%, and stir for 90 - 120 minutes; while stirring, add an aldehyde cross - linking agent with a weight fraction of 0.4% - 0.6%, and stir for 20 - 30 minutes; finally, while stirring, add a phenolic cross - linking agent with a weight fraction of 0.4% - 0.6%, and stir for 20 - 30 minutes to obtain a gelling solution, and then gel at 130 - 150°C to obtain a nano - graphite hybrid cross - linked gel plugging agent for deep oil and gas reservoirs.

[0111] The present invention will be further described below through examples and comparative examples, but not limited thereto.

[0112] Example 1

[0113] This example is to illustrate the modified nano - graphite for cross - linking prepared by the method of the present invention.

[0114] Raw materials: 0.25 g of nano - graphite powder; 2 g of p - aminobenzenesulfonic acid; 2 g of p - aminophenol; 2 g of sodium hydroxide; 1.6 g of sodium nitrite; 20 g of hydrochloric acid with a mass fraction of 30%; 120 g of deionized water.

[0115] Steps: At room temperature (20°C), first add 2 g of p - aminobenzenesulfonic acid to 60 g of deionized water, and add 1 g of sodium hydroxide and stir for 10 minutes under the condition that the stirring rate is 600 revolutions per minute to obtain an aqueous solution containing p - aminobenzenesulfonic acid and sodium hydroxide; place the aqueous solution containing p - aminobenzenesulfonic acid and sodium hydroxide in an ice - salt bath at 5°C and add 0.8 g of sodium nitrite while stirring for 20 minutes; while maintaining the temperature at 5°C, slowly add 10 g of hydrochloric acid with a mass fraction of 30% while stirring for 2 h to obtain a sulfonic acid aryl radical dispersion;

[0116] Maintain the temperature at 5°C, add 0.25 g of nano - graphite (flake diameter 1 μm, thickness 2 nm), and continuously stir for 6 h to obtain a preliminary modified nano - graphite aqueous solution;

[0117] Wash the above - obtained solution three times with a mixed solution of deionized water and ethanol in a ratio of 1:1 to remove the unreacted sulfonic acid aryl radicals; place the washed solution in an oven at 35°C for drying, grind and disperse to obtain preliminary modified nano - graphite particles;

[0118] And at room temperature (20 °C), 2 g of p-aminophenol was first added to 60 g of deionized water, and 1 g of sodium hydroxide was added with stirring at a rate of 600 revolutions per minute and stirred for 10 minutes to obtain an aqueous solution containing p-aminophenol and sodium hydroxide; the aqueous solution containing p-aminophenol and sodium hydroxide was placed in an ice-salt bath at 5 °C and 0.8 g of sodium nitrite was added while stirring for 20 minutes; while maintaining the temperature at 5 °C, 10 g of 30% hydrochloric acid was slowly added dropwise while stirring for 2 h to obtain a hydroxyaryl radical dispersion;

[0119] Maintaining the temperature at 5 °C, the preliminarily modified nano-graphite particles prepared above were added, and continuously stirred for 6 h to obtain a cross-linking modified nano-graphite aqueous solution;

[0120] The solution obtained above was washed three times with a mixed solution of deionized water and ethanol in a ratio of 1:1 to remove unreacted hydroxyaryl radicals; the washed solution was placed in an oven at 35 °C for drying, ground and dispersed to obtain cross-linking modified nano-graphite particles.

[0121] As a result, cross-linking modified nano-graphite particles with a sheet diameter of 1.5 μm and a thickness of 2 nm were obtained. The grafting rate by thermogravimetric analysis was 37%, and its structure is shown in formula (I):

[0122]

[0123] In addition, the content of sulfonic acid aryl active radicals was 32%, and the content of hydroxyaryl active radicals was 41%.

[0124] In addition, Figure 1 is the infrared spectrum of the cross-linking modified nano-graphite of Example 1. From Figure 1 it can be seen that: sulfonic acid groups and hydroxyl groups appeared on the surface of the cross-linking modified nano-graphite, indicating that the nano-graphite was successfully modified.

[0125] Example 2

[0126] This example is to illustrate the cross-linking modified nano-graphite prepared by the method of the present invention.

[0127] Raw materials: 0.5 g of nano-graphite powder; 2 g of p-aminobenzenesulfonic acid; 2 g of o-aminophenol; 2 g of sodium hydroxide; 1.6 g of sodium nitrite; 20 g of hydrochloric acid, with a mass fraction of 30%; 120 g of deionized water.

[0128] Procedure: At room temperature (25 °C), first add 2 g of sulfanilic acid to 60 g of deionized water, and add 1 g of sodium hydroxide while stirring at a rate of 500 revolutions per minute and stir for 10 minutes to obtain an aqueous solution containing sulfanilic acid and sodium hydroxide; place the aqueous solution containing sulfanilic acid and sodium hydroxide in a 5 °C ice-salt bath and add 0.8 g of sodium nitrite while stirring for 20 minutes; while maintaining the temperature at 5 °C, slowly add 10 g of 30% hydrochloric acid while stirring for 2 h to obtain an arylsulfonic acid radical dispersion;

[0129] Maintain the temperature at 5 °C, add 0.5 g of nano-graphite (flake diameter 1.5 μm, thickness 3 nm), and continuously stir for 6 h to obtain a preliminarily modified nano-graphite aqueous solution;

[0130] Wash the solution obtained above three times with a mixed solution of deionized water and ethanol in a ratio of 1:1 to remove the unreacted arylsulfonic acid radicals; place the washed solution in an oven at 45 °C for drying, grinding and dispersion to obtain preliminarily modified nano-graphite particles;

[0131] And at room temperature (25 °C), first add 2 g of o-aminophenol to 60 g of deionized water, and add 1 g of sodium hydroxide while stirring at a rate of 500 revolutions per minute and stir for 10 minutes to obtain an aqueous solution containing o-aminophenol and sodium hydroxide; place the aqueous solution containing o-aminophenol and sodium hydroxide in a 5 °C ice-salt bath and add 0.8 g of sodium nitrite while stirring for 20 minutes; while maintaining the temperature at 5 °C, slowly add 10 g of 30% hydrochloric acid while stirring for 2 h to obtain a hydroxyaryl radical dispersion;

[0132] Maintain the temperature at 5 °C, add the preliminarily modified nano-graphite particles prepared above, and continuously stir for 6 h to obtain a cross-linking modified nano-graphite aqueous solution;

[0133] Wash the solution obtained above three times with a mixed solution of deionized water and ethanol in a ratio of 1:1 to remove the unreacted hydroxyaryl radicals; place the washed solution in an oven at 45 °C for drying, grinding and dispersion to obtain cross-linking modified nano-graphite particles.

[0134] As a result, cross-linking modified nano-graphite particles with a flake diameter of 1.5 μm and a thickness of 3 nm are obtained. The grafting rate by thermogravimetric analysis is 24%, and its structure is shown in formula (II):

[0135]

[0136] In addition, the content of arylsulfonic acid active radicals is 27%, and the content of hydroxyaryl active radicals is 21%.

[0137] Example 3

[0138] This example aims to illustrate the crosslinking-modified nano-graphite prepared by the method of the present invention.

[0139] Raw materials: 0.5 g of nano-graphite powder; 2 g of p-aminobenzenesulfonic acid; 2 g of m-aminophenol; 2 g of sodium hydroxide; 1.6 g of sodium nitrite; 40 g of hydrochloric acid, with a mass fraction of 30%; 120 g of deionized water.

[0140] Steps: At room temperature (25 °C), first add 2 g of p-aminobenzenesulfonic acid to 60 g of deionized water, and add 1 g of sodium hydroxide under the condition of a stirring rate of 500 revolutions per minute and stir for 10 minutes to obtain an aqueous solution containing p-aminobenzenesulfonic acid and sodium hydroxide; place the aqueous solution containing p-aminobenzenesulfonic acid and sodium hydroxide in a 5 °C ice-salt bath and add 0.8 g of sodium nitrite while stirring for 20 minutes; while maintaining the temperature at 5 °C, slowly add 20 g of hydrochloric acid with a mass fraction of 30% dropwise over 2 h while stirring to obtain a sulfonic aryl radical dispersion;

[0141] Maintain the temperature at 5 °C, add 0.5 g of nano-graphite (flake diameter 1 μm, thickness 3 nm), and continuously stir for 6 h to obtain a preliminarily modified nano-graphite aqueous solution;

[0142] Wash the above-obtained solution three times with a mixed solution of deionized water and ethanol in a ratio of 1:1 to remove the unreacted sulfonic aryl radicals; place the washed solution in an oven at 35 °C for drying, grind and disperse to obtain preliminarily modified nano-graphite particles;

[0143] And at room temperature (25 °C), first add 2 g of m-aminophenol to 60 g of deionized water, and add 1 g of sodium hydroxide under the condition of a stirring rate of 500 revolutions per minute and stir for 10 minutes to obtain an aqueous solution containing m-aminophenol and sodium hydroxide; place the aqueous solution containing m-aminophenol and sodium hydroxide in a 5 °C ice-salt bath and add 0.8 g of sodium nitrite while stirring for 20 minutes; while maintaining the temperature at 5 °C, slowly add 20 g of hydrochloric acid with a mass fraction of 30% dropwise over 2 h while stirring to obtain a hydroxy aryl radical dispersion;

[0144] Maintain the temperature at 5 °C, add the above-prepared preliminarily modified nano-graphite particles, and continuously stir for 6 h to obtain a crosslinking-modified nano-graphite aqueous solution;

[0145] Wash the above-obtained solution three times with a mixed solution of deionized water and ethanol in a ratio of 1:1 to remove the unreacted hydroxy aryl radicals; place the washed solution in an oven at 35 °C for drying, grind and disperse to obtain crosslinking-modified nano-graphite particles.

[0146] Finally, crosslinking-modified nano-graphite particles with a flake diameter of 1.5 μm and a thickness of 3 nm are obtained. The grafting rate by thermogravimetric analysis is 27%, and its structure is shown in formula (Ⅲ):

[0147]

[0148] In addition, the content of aryl sulfonic acid active radicals is 22%, and the content of aryl hydroxyl active radicals is 32%.

[0149] Example 4

[0150] This example is to prepare a nano-graphite hybrid cross-linked gel plugging agent for deep oil and gas reservoirs by using the cross-linked modified nano-graphite prepared in Example 1.

[0151] The method for preparing the nano-graphite hybrid cross-linked gel system for deep oil and gas reservoirs includes: the cross-linked modified nano-graphite prepared in Example 1, with a mass fraction of 0.2 wt%; the aldehyde cross-linking agent hexamethylenetetramine, with a mass fraction of 0.6 wt%; the phenolic cross-linking agent is a combination of hydroquinone and catechol, with mass fractions of 0.2 wt% and 0.4 wt% respectively; the chelating agent ethylenediaminetetraacetic acid, with a mass fraction of 3 wt%; the polymer is a non-ionic polyacrylamide with a hydrolysis degree of 8 wt% and a molecular weight of 8 million g / mol, with a mass fraction of 0.8 wt%; the balance is the preparation water, with a mass fraction of 94.8 wt%, and the sum of the mass fractions of each component is 100 wt%.

[0152] At room temperature (20 ± 5 °C), 1.5 g of the chelating agent ethylenediaminetetraacetic acid was added to 47.4 g of the preparation water with a salinity of 200,000 mg / L (where the sodium ion is 71,538 mg / L, the calcium ion is 2,000 mg / L, and the magnesium ion is 2,000 mg / L) at a stirring rate of 600 revolutions per minute, and stirred for 20 minutes until it was dissolved; 0.1 g of the cross-linked modified nano-graphite was added while stirring, and stirred for 30 minutes to obtain a cross-linked modified nano-graphite dispersion; then 0.4 g of non-ionic polyacrylamide with a molecular weight of 8 million and a hydrolysis degree of 8% was slowly added while stirring, and stirred for 120 minutes until it was fully dissolved; then 0.3 g of the aldehyde cross-linking agent hexamethylenetetramine was added while stirring, and stirred for 20 minutes; finally, 0.1 g of the phenolic cross-linking agent hydroquinone and 0.2 g of the phenolic cross-linking agent catechol were added while stirring, and stirred for 20 minutes to obtain a gelling solution, and then gelled at 130 °C for 6 hours to obtain a nano-graphite hybrid cross-linked gel plugging agent A1 for deep oil and gas reservoirs. The stable period of this hybrid cross-linked gel plugging agent can reach 90 days, the strength retention rate is 92%, and the core plugging rate is 92%.

[0153] Figure 2 is the initial state after the nano-graphite hybrid cross-linked gel plugging agent in Example 4 gels. From Figure 2 It can be seen that no dehydration phenomenon was observed in the initial stage of the gelation of the nano-graphite hybrid cross-linked gel plugging agent, indicating that the nano-graphite hybrid cross-linked gel plugging agent has a relatively high structural strength.

[0154] Figure 3This is the state of the nano-graphite hybrid crosslinked gel plugging agent in Example 4 after 60 days of aging. It can be seen from Figure 3 that after 60 days of aging, no significant dehydration phenomenon was found in the nano-graphite hybrid crosslinked gel plugging agent. The modified nano-graphite used for crosslinking can significantly improve the high-temperature and high-salt aging stability of the gel plugging agent, enabling it to be applicable to the high-temperature and high-salt conditions of deep oil and gas reservoirs.

[0155] Example 5

[0156] This example is to prepare a nano-graphite hybrid crosslinked gel plugging agent for deep oil and gas reservoirs by using the modified nano-graphite for crosslinking prepared in Example 2.

[0157] The method for preparing a nano-graphite hybrid crosslinked gel system for deep oil and gas reservoirs includes: the modified nano-graphite for crosslinking prepared in Example 2, with a mass fraction of 0.2 wt%; the aldehyde crosslinking agent hexamethylenetetramine, with a mass fraction of 0.6 wt%; the phenolic crosslinking agents are a combination of hydroquinone, catechol, and resorcinol, with mass fractions of 0.2 wt%, 0.2 wt%, and 0.2 wt% respectively; the chelating agent is a combination of ethylenediaminetetraacetic acid and sodium nitrite, with mass fractions of 2 wt% and 1 wt% respectively; the polymer is a copolymer with a molecular weight of 8 million g / mol, a hydrolysis degree of 4 wt%, and an AM / AMPS content of 40 wt%, with a mass fraction of 0.8 wt%; the balance is the formulation water, with a mass fraction of 94.8 wt%. The sum of the mass fractions of each component is 100 wt%.

[0158] At room temperature (20 ± 5 °C), 1 g of the chelating agent ethylenediaminetetraacetic acid and 0.5 g of the chelating agent sodium nitrite were added to 47.4 g of formulation water with a salinity of 200,000 mg / L (where the sodium ion is 71,538 mg / L, the calcium ion is 2,000 mg / L, and the magnesium ion is 2,000 mg / L) at a stirring rate of 600 revolutions per minute, and stirred for 20 minutes until dissolved; 0.1 g of the modified nano-graphite for crosslinking was added while stirring, and stirred for 30 minutes to obtain a dispersed solution of the modified nano-graphite for crosslinking; then 0.4 g of the copolymer with a molecular weight of 8 million, a hydrolysis degree of 4%, and an AM / AMPS content of 40% was slowly added while stirring, and stirred for 120 minutes until fully dissolved; then 0.3 g of the aldehyde crosslinking agent hexamethylenetetramine was added while stirring, and stirred for 20 minutes; finally, 0.1 g of the phenolic crosslinking agent hydroquinone, 0.1 g of the phenolic crosslinking agent catechol, and 0.1 g of the phenolic crosslinking agent resorcinol were added while stirring, and stirred for 20 minutes to obtain a gelling solution, and then it was placed at 150 °C for 4 hours to form a gel, obtaining the nano-graphite hybrid crosslinked gel plugging agent A2 for deep oil and gas reservoirs. The system has a gel strength of 87% and a core plugging rate of 90%.

[0159] Example 6

[0160] This embodiment is to use the crosslinking modified nano-graphite prepared in Example 3 to prepare a nano-graphite hybrid crosslinked gel system for deep oil and gas reservoirs.

[0161] The method for preparing the nano-graphite hybrid crosslinked gel plugging agent for deep oil and gas reservoirs includes: the crosslinking modified nano-graphite prepared in Example 3, with a mass fraction of 0.1 wt%; the combination of aldehyde crosslinking agents hexamethylenetetramine and formaldehyde, with mass fractions of 0.4 wt% and 0.2 wt% respectively; the phenolic crosslinking agent catechol, with a mass fraction of 0.4 wt%; the chelating agent is sodium formate, with a mass fraction of 2 wt%; the polymer is a copolymer with a molecular weight of 8 million g / mol, a hydrolysis degree of 3 wt%, and an AM / AMPS content of 40 wt%, with a mass fraction of 0.6 wt%; the balance is the preparation water, with a mass fraction of 96.3 wt%, and the sum of the mass fractions of each component is 100 wt%.

[0162] At room temperature (20 ± 5 °C), add 1 g of the chelating agent sodium formate to 48.15 g of the preparation water with a salinity of 200,000 mg / L (where the sodium ion is 71,538 mg / L, the calcium ion is 2,000 mg / L, and the magnesium ion is 2,000 mg / L) at a stirring rate of 600 revolutions per minute, and stir for 20 minutes until it dissolves; add 0.05 g of the crosslinking modified nano-graphite while stirring, and stir for 20 minutes to obtain a crosslinking modified nano-graphite dispersion; then slowly add 0.3 g of the copolymer with a molecular weight of 8 million g / mol, a hydrolysis degree of 3%, and an AM / AMPS content of 40% while stirring, and stir for 120 minutes until it is fully dissolved; then add 0.2 g of the aldehyde crosslinking agent hexamethylenetetramine and 0.1 g of the aldehyde crosslinking agent formaldehyde while stirring, and stir for 20 minutes; finally, add 0.2 g of the phenolic crosslinking agent catechol while stirring, and stir for 20 minutes to obtain a gelling solution, and then place it at 130 °C for 8 hours to form a gel, obtaining the nano-graphite hybrid crosslinked gel plugging agent A3 for deep oil and gas reservoirs. The gelation rate of this system is 90%, and the core plugging rate is 91%.

[0163] Comparative Example 1

[0164] According to the method described in Example 4, the difference is that the "crosslinking modified nano-graphite prepared in Example 1" is not added, obtaining a gel system B1. The gelation time is 10 hours, the stable period is only 6 days, the strength retention rate is 15%, and the core plugging rate is 27%.

[0165] Figure 4 is the initial state after the gelation of the deep oil and gas reservoir gel plugging agent in Comparative Example 1. From Figure 4 it can be seen that dehydration phenomenon is found in the deep oil and gas reservoir gel plugging agent at the initial stage of gelation, indicating that without adding crosslinking nano-graphite, the plugging agent cannot maintain stability under the conditions of deep oil and gas reservoirs, and the network structure of this gel plugging agent is weaker than that of the nano-graphite hybrid crosslinked gel.

[0166] Figure 5 It is the state of the deep oil and gas reservoir gel plugging agent in Comparative Example 1 after 60 days of aging. From Figure 5 It can be seen that: after 60 days of aging, a large amount of dehydration phenomenon is found in the deep oil and gas reservoir gel plugging agent, indicating that the gel plugging agent without the crosslinking modified nano-graphite is difficult to maintain long-term stability under the conditions of deep oil and gas reservoirs and cannot be applied to deep oil and gas reservoirs.

[0167] Comparative Example 2

[0168] According to the method described in Example 5, the difference is that "the crosslinking modified nano-graphite prepared in Example 2" is not added, and the gel system B2 is obtained. The gelation time is 7 hours, the stable period is only 2 days, the strength retention rate is 10%, and the core plugging rate is 22%.

[0169] Comparative Example 3

[0170] According to the method described in Example 4, the difference is that "unmodified nano-graphite" is added, that is, natural nano-graphite is added, and the gel system B3 is obtained. The gelation time is 8 hours, the stable period is only 15 days, the strength retention rate is 35%, and the core plugging rate is 50%.

[0171] Comparative Example 4

[0172] According to the method described in Example 5, the difference is that "unmodified nano-graphite" is added, that is, natural nano-graphite is added, and the gel system B4 is obtained. The gelation time is 6 hours, the stable period is only 12 days, the strength retention rate is 31%, and the core plugging rate is 46%.

[0173] Test Example

[0174] The above-prepared gel systems were characterized, and the results are shown in Table 1.

[0175] Table 1

[0176] Number Gelation time Stable period Strength retention rate Core plugging rate A1 6h 90d 92％ 92％ A2 4h 90d 87％ 90％ A3 8h 90d 90％ 91％ B1 10h 6d 15％ 27％ B2 7h 2d 10％ 22％ B3 8h 15d 35％ 50％ B4 6h 12d 31％ 46％

[0177] It can be seen from Table 1 that after adding the crosslinking modified nano-graphite, the stable period, strength retention rate and core plugging rate of the gel are significantly improved under high temperature and high salt conditions (150 °C, 200,000 mg / L), indicating that the crosslinking modified nano-graphite can improve the temperature and salt tolerance of the gel, and the crosslinking modified nano-graphite hybrid gel plugging agent can be applied to deep gas reservoirs.

[0178] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A nano-graphite hybrid crosslinked gel plugging agent for deep oil and gas reservoirs, characterized in that, The hybrid crosslinked gel plugging agent includes crosslinking modified nano-graphite, which is obtained by modifying natural nano-graphite with aryl sulfonic acid active free radicals to obtain preliminarily modified nano-graphite; the preliminarily modified nano-graphite is crosslinked with aryl hydroxyl active free radicals; and the hybrid crosslinked gel plugging agent also contains formulated water, polyacrylamide, aldehyde crosslinking agent, phenolic crosslinking agent and chelating agent; Among them, the aryl sulfonic acid-containing active radical is ; The hydroxyaryl active radical contained is , and one or more of the following.

2. The hybrid crosslinked gel plugging agent according to claim 1, wherein, Based on the total free radicals contained in the crosslinking modified nano-graphite, the content of the aryl sulfonic acid active free radicals is 20-40%, and the content of the aryl hydroxyl active free radicals is 20-40%.

3. The hybrid crosslinked gel plugging agent according to claim 1, wherein The structure of the crosslinking modified nano-graphite includes one or more of the structures shown in formula (I) to formula (III); , formula (I); , formula (II); , formula (III).

4. The hybrid crosslinked gel plugging agent according to any one of claims 1-3, wherein, The sheet diameter of the crosslinking modified nano-graphite is 1-3 μm, and the thickness is 1-5 nm.

5. The hybrid crosslinked gel plugging agent according to claim 1, wherein, The preparation method of the crosslinking modified nano-graphite includes: (a) Disperse the diazonium salt of sulfanilic acid shown in formula (2) in deionized water to release nitrogen to obtain a dispersion containing aryl sulfonic acid active free radicals; (b) Contact the dispersion in step (a) with natural nano-graphite shown in formula (3) to obtain a solution of preliminarily modified nano-graphite; (c) Wash, dry and grind and disperse the solution of preliminarily modified nano-graphite to obtain preliminarily modified nano-graphite; (d) Disperse the diazonium salt of any one of formula (4) - formula (6) in deionized water to release nitrogen to obtain a dispersion containing aryl hydroxyl active free radicals; (e) Contact the dispersion in step (d) with the preliminarily modified nano-graphite in step (c) to obtain a solution of crosslinking modified nano-graphite; (f) Wash, dry and grind and disperse the solution of crosslinking modified nano-graphite to obtain crosslinking modified nano-graphite; , formula (2); , formula (3); , formula (4); , formula (5); , formula (6).

6. The hybrid crosslinked gel plugging agent according to claim 5, wherein, In (a), the preparation method of the dispersion containing aryl sulfonic acid active free radicals includes: (a-1) Contact sulfanilic acid, sodium hydroxide and deionized water to obtain a first mixed solution; (a-2) Under the condition of an ice-salt bath, contact the first mixed solution with sodium nitrite to obtain a second mixed solution; (a-3) Dropwise add hydrochloric acid to the second mixed solution to prepare the diazonium salt of sulfanilic acid shown in formula (2); (a-4) Form a dispersion containing aryl sulfonic acid free radicals by releasing nitrogen molecules from the diazonium salt of sulfanilic acid.

7. The hybrid crosslinked gel plugging agent according to claim 6, wherein, In (d), the preparation method of the dispersion containing aryl hydroxyl active free radicals includes: (d-1) Contact aminophenol, sodium hydroxide and deionized water to obtain a third mixed solution; (d-2) Contact the third mixed solution with sodium nitrite to obtain a fourth mixed solution; (d-3) Dropwise add hydrochloric acid to the fourth mixed solution to prepare the diazonium salt of any one of formula (4) - formula (6); (d-4) Form a dispersion containing aryl hydroxyl free radicals by releasing nitrogen molecules from the diazonium salt of aminophenol.

8. The hybrid crosslinked gel plugging agent according to claim 7, wherein, In (a-2), the conditions of the ice-salt bath include: the temperature is 0-8°C; And / or, in (a-3) and (d-3), the conditions for dropping include: the temperature is 0-5°C; And / or, in (a-4), the conditions for releasing nitrogen molecules include: maintaining the sulfanilic acid diazonium salt at a temperature of 0-8°C.

9. The hybrid crosslinked gel plugging agent according to claim 6, wherein, The weight ratio of the amounts of sulfanilic acid, sodium hydroxide, deionized water, sodium nitrite, and hydrochloric acid is (1-2):(1-2):(60-80):(0.8-1.6):(3-6).

10. The hybrid crosslinked gel plugging agent according to claim 7, wherein, The weight ratio of the amounts of aminophenol, sodium hydroxide, deionized water, sodium nitrite, and hydrochloric acid is (1-2):(1-2):(60-80):(0.8-1.6):(3-6).

11. The hybrid crosslinked gel plugging agent according to claim 5, wherein, In step (b), the conditions for contacting include: the stirring rate is 500-600 revolutions per minute, the temperature is 0-5°C, and the time is 6-8 h; And / or, in step (e), the conditions for contacting include: the stirring rate is 500-600 revolutions per minute, the temperature is 0-5°C, and the time is 6-8 h.

12. The hybrid crosslinked gel plugging agent according to claim 1, wherein, The chelating agent is selected from one or more of ethylenediaminetetraacetic acid, sodium nitrite, and sodium formate; And / or, the polyacrylamide is an AM / AMPS copolymer and / or non-ionic polyacrylamide; And / or, the aldehyde crosslinking agent is selected from hexamethylenetetramine and / or formaldehyde; And / or, the phenolic crosslinking agent is one or more of hydroquinone, resorcinol, and catechol.

13. The hybrid crosslinked gel plugging agent according to claim 1, wherein, Based on the total weight of the hybrid crosslinked gel plugging agent, the amount of the modified nano-graphite for crosslinking is 0.05-0.2 wt%, the amount of the polyacrylamide is 0.3-0.8 wt%, the amount of the aldehyde crosslinking agent is 0.2-0.8 wt%, the amount of the phenolic crosslinking agent is 0.2-0.6 wt%, the amount of the chelating agent is 1-3 wt%, and the amount of the liquid-making water is 94.8-96.7 wt%.

14. A method for preparing the deep oil and gas reservoir nano-graphite hybrid crosslinked gel plugging agent according to any one of claims 1-13, characterized in that, The described preparation method includes: (a1) Disperse the chelating agent in the liquid-making water; (b1) Disperse the modified nano-graphite for crosslinking in the liquid-making water to obtain a dispersion of the modified nano-graphite for crosslinking; (c1) Contact the polyacrylamide with the dispersion of the modified nano-graphite for crosslinking; (d1) Contact the aldehyde crosslinking agent with the solution obtained in step (c1); (e1) Contact the phenolic crosslinking agent with the solution obtained in step (d1) to obtain a gelling solution; (f1) Carry out a crosslinking reaction on the gelling solution to obtain a nano-graphite hybrid crosslinked gel plugging agent for deep oil and gas reservoirs.

15. The preparation method according to claim 14, wherein In step (c1), the conditions for contacting include: the stirring rate is 500-600 revolutions per minute, and the time is 90-120 minutes; And / or, in step (d1), the conditions for contacting include: the stirring rate is 500-600 revolutions per minute, and the time is 20-30 minutes; And / or, in step (e1), the conditions for contacting include: the stirring rate is 500-600 revolutions per minute, and the time is 20-30 minutes; And / or, the conditions for the crosslinking reaction include: the temperature is 130-150°C, and the time is 4-24 h.

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