A dual-based nano oil and water fracturing temporary plugging agent

Abstract

The present invention relates to the technical field of oil and gas development, and discloses a double-based nano oil and water fracturing temporary plugging agent, which comprises the following raw materials in parts by mass: 10-12 parts of starch, 10-15 parts of acrylic acid, 20-22 parts of acrylamide, 10-12 parts of styrene, 5-6 parts of a composite reinforcing material, 0.05-0.15 parts of an initiator, 0.5-0.6 parts of a crosslinking agent, and 60-80 parts of a solvent. The starch, acrylic acid, acrylamide, and styrene form a crosslinked network oil and water fracturing temporary plugging agent, which has amphiphilicity and high pressure-bearing capacity, and also has good degradability. After degradation, the core permeability recovery rate is high, and it has a good temporary plugging diversion effect. Moreover, the formed composite reinforcing material is covalently crosslinked in the oil and water fracturing temporary plugging agent system, increasing the crosslinking density of the oil and water fracturing temporary plugging agent and improving the compressive strength.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas development, and specifically to a double-based nano oil and water fracturing temporary plugging agent. Background Art

[0002] Oil and natural gas are currently the most widely used non-renewable energy sources. With the large-scale exploitation of oil and gas energy, the exploitation of low-permeability oil and gas resources is particularly important. The reserves of low-permeability oil and gas resources account for 30% of the total oil reserves, and the unexploited low-permeability reservoirs account for more than 50% of all unexploited reservoirs. Therefore, the development of low-permeability oil and gas fields is of great significance to the development of China's petroleum industry; by adding temporary plugging materials to the fracturing fluid (temporary plugging balls block the holes, and the temporary plugging agent blocks the ends of the fractures along with the fracturing fluid), the flow direction of the original liquid can be changed, promoting the opening of new fractures in other perforation clusters or formations, and finally forming multiple new branch fractures to achieve the purpose of fine reservoir reconstruction.

[0003] The temporary plugging and diversion fracturing technology is an important high-efficiency development technology for oil and gas reservoir resources, that is, using a temporary plugging agent to effectively temporarily plug the fractures, effectively preventing the fracturing fluid from entering the old fractures, and then conducting diversion fracturing to generate one or more new fractures, so that the fractures can be extended, and finally a new fracture network is formed. After the fracturing construction is completed, the temporary plugging agent can be dissolved in the formation and discharged with the production, restoring the formation permeability, maximizing the contact between the wellbore and the oil and gas reservoir, and improving the recovery rate; however, the existing fracturing temporary plugging agent has low compressive strength and is easy to fall off, resulting in low sealing efficiency. By adding inorganic materials to the temporary plugging agent, the compressive strength of the temporary plugging agent can be effectively improved, but the inorganic materials have poor dispersibility in the temporary plugging agent and are easy to migrate and precipitate, affecting the plugging effect of the temporary plugging agent, and the fracturing temporary plugging agent has a fast water absorption rate and poor long-term stability under high salinity, affecting the effective temporary plugging of the fracturing temporary plugging agent. Summary of the Invention

[0004] The present invention provides a double-based nano oil and water fracturing temporary plugging agent, which solves the problems of low compressive strength, easy falling off, poor long-term stability under high salinity and easy migration and precipitation of nano particles in the temporary plugging agent of the fracturing temporary plugging agent.

[0005] The technical solution of the present invention:

[0006] A double-based nano oil and water fracturing temporary plugging agent, comprising the following raw materials in parts by mass: 10 - 12 parts of starch, 10 - 15 parts of acrylic acid, 20 - 22 parts of acrylamide, 10 - 12 parts of styrene, 5 - 6 parts of a composite reinforcing material, 0.05 - 0.15 parts of an initiator, 0.5 - 0.6 parts of a crosslinking agent, and 60 - 80 parts of a solvent;

[0007] A preparation method of a double-based nano oil and water fracturing temporary plugging agent, comprising the following preparation steps:

[0008] Starch, acrylic acid, acrylamide, styrene and a composite reinforcing material are added to a solvent, stirred evenly, an initiator and a crosslinking agent are added, and after stirring at 45 - 55 °C for 25 - 35 min, the mixture is stirred and reacted at 70 - 75 °C for 2 - 4 h, cooled to room temperature, the precipitated solid is washed, and after the solid is dried, an oil and water fracturing temporary plugging agent is obtained.

[0009] The composite reinforcing material is prepared by mixing and reacting shell powder loaded with nano - zirconia, modified montmorillonite and stearic acid;

[0010] The shell powder loaded with nano - zirconia is prepared by acidifying the shell powder, then mixing it with zirconium oxychloride octahydrate and performing a hydrothermal reaction;

[0011] The modified montmorillonite is prepared by reacting 1 - bromohexadecane with 2 - (dimethylamino) ethyl methacrylate and then mixing it with montmorillonite.

[0012] Furthermore, the starch is corn starch.

[0013] Furthermore, the crosslinking agent is N,N'-methylenebisacrylamide.

[0014] Furthermore, the initiator is benzoyl peroxide.

[0015] Furthermore, the solvent is ethyl acetate.

[0016] Furthermore, the composite reinforcing material is specifically prepared by the following steps:

[0017] A1. 1 - bromohexadecane and 2 - (dimethylamino) ethyl methacrylate are added to ethanol, stirred evenly, heated to 45 - 55 °C, stirred and reacted for 20 - 22 h, then after rotary evaporation, recrystallized with acetone, taken out, washed, to obtain a monomer;

[0018] A2. Montmorillonite is added to deionized water, stirred evenly, the monomer is added, and stirring is continued for 10 - 12 h. After washing with ethanol, the precipitate is obtained by filtration. After the precipitate is dried, modified montmorillonite is obtained;

[0019] A3. The shell powder is impregnated in a nitric acid solution with a mass fraction of 5 - 6% for 40 - 50 min, taken out, washed, dried, placed in a pulverizer and pulverized, and passed through a 500 - 600 - mesh sieve to obtain acidified shell powder;

[0020] A4. Zirconium oxychloride octahydrate is added to deionized water, stirred evenly, ammonia water, glycine and potassium chloride with a mass fraction of 25 - 30% are added, stirred evenly, acidified shell powder is added, stirred evenly, placed in a reaction kettle, and hydrothermal reaction is carried out at 175 - 185 °C for 20 - 24 h. After cooling to room temperature, it is filtered, washed, and dried to obtain shell powder loaded with nano - zirconia;

[0021] A5. Add the shell powder loaded with nano-zirconia into N,N-dimethylformamide, stir evenly, add stearic acid, and stir until the stearic acid is dissolved. Stir and react at 70-80 °C for 20-22 h, then filter, wash, and dry to obtain the composite.

[0022] A6. Add the composite and the modified montmorillonite into ethanol, stir evenly, stir at 50-60 °C for 1-2 h, then raise the temperature to 80-85 °C and stir until the ethanol evaporates. Take out the solid, wash and dry the solid to obtain the composite reinforcing material.

[0023] Furthermore, during the above A1 reaction process, the bromine atom in 1-bromohexadecane can react with the tertiary amino group in 2-(dimethylamino)ethyl methacrylate, enabling 1-bromohexadecane to graft onto 2-(dimethylamino)ethyl methacrylate to synthesize the monomer.

[0024] Furthermore, during the above A2 reaction process, the cationic functional groups contained in the monomer can undergo an ion exchange reaction with the cations between the layers of sodium-based montmorillonite, enabling the monomer to intercalate into the interlayer of sodium-based montmorillonite. After vigorous stirring, exfoliated sodium-based montmorillonite is formed, and the monomer is adsorbed on the surface of the exfoliated sodium-based montmorillonite to form the modified montmorillonite.

[0025] Furthermore, during the above A3 reaction process, nitric acid can react with calcium carbonate in the shell powder to generate soluble nitrates, and can remove the organic substances and impurities in the shell powder, exposing the original pore structure of the shell powder, increasing the specific surface area and pore structure of the shell powder, and increasing the contact area between the shell powder and the cracks.

[0026] Furthermore, during the above A4 reaction process, the porous structure of the acidified shell powder has excellent adsorption performance and can adsorb zirconium ions in zirconium oxychloride octahydrate into the pores of the shell powder. And ammonia water, as a basic precipitating agent, can react with zirconium ions in zirconium oxychloride octahydrate to form zirconium hydroxide precipitate, forming zirconium hydroxide precipitate on the surface and in the pores of the acidified shell powder. Perform a hydrothermal reaction at 180 °C for 24 h to decompose the formed zirconium hydroxide precipitate, and the additives glycine and potassium chloride can adjust the crystal phase of zirconia, realizing the formation of nano-zirconia with a size of 100-200 nm on the surface and in the pores of the acidified shell powder.

[0027] Furthermore, during the above A5 reaction process, in the organic solvent N,N-dimethylformamide, the carboxyl group contained in stearic acid can chemically bond with the hydroxyl groups on the surface of the shell powder loaded with nano-zirconia, enabling stearic acid to graft onto the surface of the shell powder loaded with nano-zirconia to form the composite.

[0028] Further, during the above A6 reaction process, the long alkyl chains on the surface of the modified montmorillonite can intertwine with the stearic acid chains on the surface of the complex to form a hydrophobic channel, enabling the modified montmorillonite to deposit on the surface of the complex and form a composite reinforcing material.

[0029] Further, in step A1, the volume ratio of 1-bromohexadecane, 2-(dimethylamino)ethyl methacrylate, and ethanol is (18 - 22):(10 - 12):(80 - 120).

[0030] Further, in step A2, the dosage ratio of montmorillonite, deionized water, and monomer is (4 - 6) g:(45 - 55) mL:(0.3 - 0.6) g.

[0031] Further, in step A3, the dosage ratio of shell powder and nitric acid solution is (8 - 12) g:(45 - 55) mL.

[0032] Further, in step A4, the dosage ratio of zirconium oxychloride octahydrate, deionized water, ammonia water, glycine, potassium chloride, and acidified shell powder is (3.9 - 4.3) g:(18 - 22) mL:(8 - 12) mL:(0.5 - 1.5) g:(1 - 3) g:(5 - 6) g.

[0033] Further, in step A5, the dosage ratio of shell powder loaded with nano-zirconium dioxide, N,N-dimethylformamide, and stearic acid is (5 - 7) g:(45 - 55) mL:(2 - 3) g.

[0034] Further, in step A6, the dosage ratio of the complex, modified montmorillonite, and ethanol is (5 - 6 g):(1 - 2) g:(45 - 55) mL.

[0035] Further, the montmorillonite is sodium-based montmorillonite, with a particle size of 2 - 3 μm and a content of 84.5 - 86.5%.

[0036] Further, the particle size of the shell powder is 1 - 2 mm, and the calcium carbonate content is 95%.

[0037] The present invention has the following beneficial effects:

[0038] (1) In the technical solution of the present invention, 1-bromohexadecane reacts with ethyl 2-(dimethylamino)acrylate to form a monomer, which is mixed with sodium-based montmorillonite. The cationic functional groups contained in the monomer can undergo an ion exchange reaction with the cations between the layers of sodium-based montmorillonite, enabling the monomer to intercalate into the interlayer of sodium-based montmorillonite. After vigorous stirring, exfoliated sodium-based montmorillonite is formed. The long hydrophobic chains of the monomer will entangle with each other, forming a hydrophobic network structure on the surface of the exfoliated sodium-based montmorillonite, reducing the water absorption rate of the oil-water fracturing temporary plugging agent, promoting the uniform distribution of the oil-water fracturing temporary plugging agent in the fracture, increasing the plugging rate, and alleviating the water absorption and swelling rate of the oil-water fracturing temporary plugging agent, avoiding the too-fast water absorption and swelling rate of the fracturing temporary plugging agent, which may cause the fracturing temporary plugging agent to agglomerate and become ineffective, affecting the plugging efficiency. This allows the oil-water fracturing temporary plugging agent to have sufficient time to reach the bottom layer and plug the fracture, improving the recovery rate. In addition, the exfoliated sodium-based montmorillonite also has good salt tolerance and long-term stability, enhancing the long-term stability of the oil-water fracturing temporary plugging agent under high salinity.

[0039] (2) In the technical solution of the present invention, the shell powder is acid-treated, which can increase the specific surface area and pore structure of the shell powder, increase the contact area between the shell powder and the fracture, facilitate entry into the microchannels of the fracture, and improve the density of the temporary plugging layer. Nano-zirconia is formed on the surface and in the pores of the acid-treated shell powder, which can refine the pore size of the acid-treated shell powder, reduce the water absorption rate of the acid-treated shell powder, and avoid the poor long-term stability of the oil-water fracturing temporary plugging agent under high salinity due to the relatively fast water absorption rate of the shell powder, which affects the effective temporary plugging of the fracturing temporary plugging agent. In addition, the addition of nano-zirconia can effectively improve the compressive strength of the fracturing temporary plugging agent. Moreover, when the oil-water fracturing temporary plugging agent absorbs water and swells to form a colloid, the shell powder slowly absorbs water, causing the nano-zirconia in the shell powder to be released, which can block the rough pore surface of the colloid, improving the compressive strength and sealing effect of the colloid.

[0040] (3) In the technical solution of the present invention, the carboxyl group contained in stearic acid can chemically bond with the hydroxyl groups on the surface of the shell powder loaded with nano-zirconia, enabling stearic acid to graft onto the surface of the shell powder loaded with nano-zirconia, forming a composite, converting the shell powder loaded with nano-zirconia from a hydrophilic to a hydrophobic structure, and avoiding the aggregation of the shell powder loaded with nano-zirconia.

[0041] (4) In the technical solution of the present invention, the composite is mixed with modified montmorillonite. The long alkyl chains on the surface of the modified montmorillonite can entangle with the stearic acid chains on the surface of the composite, causing the modified montmorillonite to deposit on the surface of the composite and entangle with each other to form a hydrophobic channel, making it difficult for the water adsorbed inside the oil-water fracturing temporary plugging agent to overflow, providing a large amount of water absorption and retention space for the oil-water fracturing temporary plugging agent, and avoiding the dehydration of the oil-water fracturing temporary plugging agent when it absorbs water and swells to form colloid particles, which may cause the colloid particles to become fragile and easily broken, affecting the plugging effect.

[0042] (5) In the technical solution of the present invention, starch, acrylic acid, acrylamide, and styrene are used as raw materials. Under the action of an initiator and a crosslinking agent, a crosslinked network oil and water fracturing temporary plugging agent is formed, which has amphiphilicity and high pressure-bearing capacity. It can plug the crack end with the fracturing fluid, change the inflow direction of the original liquid, and prompt other perforation clusters or formations to open new cracks. The formed oil and water fracturing temporary plugging agent also has good degradability. After degradation, the core permeability recovery rate is high, and it has a good temporary plugging and diversion effect. Moreover, the monomers contained on the surface of the formed composite reinforcing material and the carried double bonds can also crosslink and copolymerize with acrylic acid, acrylamide, and styrene, so that the composite reinforcing material acts in the oil and water fracturing temporary plugging agent system, increasing the crosslinking density of the oil and water fracturing temporary plugging agent and improving the compressive strength. In addition, the composite reinforcing material and the oil and water fracturing temporary plugging agent are combined by covalent bonds, improving the binding force between the composite reinforcing material and the matrix of the oil and water fracturing temporary plugging agent. Specific embodiments

[0043] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0044] In the embodiments of the present invention, the raw materials used are as follows, and all the reagents used are of analytical grade.

[0045] Among them, the starch is corn starch, food grade, from Beijing Xiangyu Biotechnology Co., Ltd.

[0046] The crosslinking agent is N,N'-methylenebisacrylamide;

[0047] The initiator is benzoyl peroxide.

[0048] The solvent is ethyl acetate.

[0049] The montmorillonite is sodium-based montmorillonite, with a particle size of 2.5 μm and a content of 85.5%, from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0050] The particle size of the shell powder is 1.5 mm, and the calcium carbonate content is 95%, from Qingdao Wanyuan Biotechnology Co., Ltd. Embodiment

[0051] A dual-based nano oil and water fracturing temporary plugging agent comprises the following raw materials in parts by mass: 10 parts of starch, 10 parts of acrylic acid, 20 parts of acrylamide, 10 parts of styrene, 5 parts of composite reinforcing material, 0.05 part of benzoyl peroxide, 0.5 part of N,N'-methylenebisacrylamide, and 60 parts of ethyl acetate;

[0052] A preparation method of a double-base nano oil-water fracturing temporary plugging agent, comprising the following preparation steps:

[0053] Add starch, acrylic acid, acrylamide, styrene and composite reinforcing material into a solvent, stir evenly, add benzoyl peroxide and N,N'-methylenebisacrylamide, stir at 45°C for 25 min until the starch is gelatinized, then stir and react at 70°C for 2 h, cool to room temperature, wash with deionized water until solid precipitates, and after drying the solid, obtain the oil-water fracturing temporary plugging agent.

[0054] The composite reinforcing material is specifically prepared by the following steps:

[0055] A1. Add 18 mL of 1-bromohexadecane and 10 mL of 2-(dimethylamino)ethyl methacrylate into 80 mL of ethanol, stir evenly, heat up to 45°C, stir and react for 20 h, then after rotary evaporation, add acetone for recrystallization, take out, wash with acetone 3 times to obtain the monomer.

[0056] A2. Add 4 g of sodium-based montmorillonite into 45 mL of deionized water, stir evenly, heat up to 35°C, continue to stir until no aggregates are observed, add 0.3 g of the monomer, stir for 10 h, wash the obtained product with ethanol to remove water and excess monomer, filter to obtain the precipitate, and dry the precipitate in an oven at 50°C for 20 min to obtain the modified montmorillonite.

[0057] A3. Immerse 8 g of shell powder into 45 mL of a 5% nitric acid solution, immerse for 40 min, take out, wash with deionized water until the washing liquid is neutral, dry in an oven at 70°C for 10 min, place in a pulverizer, pulverize, and pass through a 500-mesh sieve to obtain acidified shell powder.

[0058] A4. Add 3.9 g of zirconium oxychloride octahydrate into 18 mL of deionized water, stir evenly, add 8 mL of 25% ammonia water, 0.5 g of glycine and 1 g of potassium chloride, stir evenly, add 5 g of acidified shell powder, stir at 85°C for 10 min, place in a reaction kettle, carry out hydrothermal reaction at 175°C for 20 h, cool to room temperature, filter, wash with deionized water until no chloride ions can be detected in the supernatant with silver nitrate solution, and dry in an oven at 80°C for 3 h to obtain shell powder loaded with nano zirconia.

[0059] A5. Add 5 g of shell powder loaded with nano zirconia into 45 mL of N,N-dimethylformamide, stir evenly, add 2 g of stearic acid, stir until the stearic acid dissolves, stir and react at 70°C for 20 h, filter, wash with deionized water 3 times, and dry in an oven at 70°C for 20 min to obtain the composite.

[0060] A6. Add 5 g of the composite and 1 g of the modified montmorillonite to 45 mL of ethanol, stir evenly, stir at 50 °C for 1 h, raise the temperature to 80 °C, stir until the ethanol evaporates, take out the solid, wash the solid 3 times with deionized water, and dry it in an oven at 80 °C for 10 min to obtain the composite reinforcing material. Example

[0061] A kind of double-base nano oil-water fracturing temporary plugging agent, comprising the following raw materials in parts by mass: 11 parts of starch, 13 parts of acrylic acid, 21 parts of acrylamide, 11 parts of styrene, 5.5 parts of composite reinforcing material, 0.1 part of benzoyl peroxide, 0.55 part of N,N'-methylenebisacrylamide, and 70 parts of ethyl acetate;

[0062] A preparation method of a double-base nano oil-water fracturing temporary plugging agent, comprising the following preparation steps:

[0063] Add starch, acrylic acid, acrylamide, styrene and the composite reinforcing material to a solvent, stir evenly, add benzoyl peroxide and N,N'-methylenebisacrylamide, stir at 50 °C for 30 min until the starch is gelatinized, then stir and react at 73 °C for 3 h, cool to room temperature, wash with deionized water until a solid precipitates, and after drying the solid, obtain the oil-water fracturing temporary plugging agent.

[0064] The composite reinforcing material is specifically prepared by the following steps:

[0065] A1. Add 20 mL of 1-bromohexadecane and 11 mL of 2-(dimethylamino)ethyl methacrylate to 100 mL of ethanol, stir evenly, raise the temperature to 50 °C, stir and react for 21 h, then after rotary evaporation, add acetone for recrystallization, take out, and wash 3 times with acetone to obtain the monomer;

[0066] A2. Add 5 g of sodium-based montmorillonite to 50 mL of deionized water, stir evenly, raise the temperature to 35 °C, continue to stir until no aggregates are observed, add 0.5 g of the monomer, stir for 11 h, wash the obtained product with ethanol to remove water and excess monomer, filter to obtain a precipitate, and dry the precipitate in an oven at 50 °C for 20 min to obtain the modified montmorillonite;

[0067] A3. Immerse 10 g of shell powder in 50 mL of a nitric acid solution with a mass fraction of 5.5% for 45 min, take out, wash with deionized water until the washing liquid is neutral, dry in an oven at 70 °C for 10 min, place in a pulverizer and pulverize, and pass through a 550-mesh sieve to obtain acidified shell powder;

[0068] A4. Add 4.1 g of zirconium oxychloride octahydrate to 20 mL of deionized water, stir evenly, add 10 mL of ammonia water with a mass fraction of 28%, 1 g of glycine, and 2 g of potassium chloride, stir evenly, add 5.5 g of acidified shell powder, stir at 85 °C for 10 min, place it in a reaction kettle, carry out hydrothermal reaction at 180 °C for 22 h, cool to room temperature, filter, wash with deionized water until no chloride ions can be detected in the supernatant with silver nitrate solution, and dry in an oven at 80 °C for 3 h to obtain shell powder loaded with nano zirconia;

[0069] A5. Add 6 g of shell powder loaded with nano zirconia to 50 mL of N,N-dimethylformamide, stir evenly, add 2.5 g of stearic acid, stir until stearic acid dissolves, stir and react at 75 °C for 21 h, filter, wash with deionized water 3 times, and dry in an oven at 70 °C for 20 min to obtain a composite;

[0070] A6. Add 5.5 g of the composite and 1.5 g of modified montmorillonite to 50 mL of ethanol, stir evenly, stir at 55 °C for 1.5 h, raise the temperature to 83 °C, stir until the ethanol evaporates, take out the solid, wash the solid with deionized water 3 times, and dry in an oven at 80 °C for 10 min to obtain a composite reinforcing material. Example

[0071] A kind of double-base nano oil and water fracturing temporary plugging agent, comprising the following raw materials in parts by mass: 12 parts of starch, 15 parts of acrylic acid, 22 parts of acrylamide, 12 parts of styrene, 6 parts of composite reinforcing material, 0.15 part of dibenzoyl peroxide, 0.6 part of N,N'-methylenebisacrylamide, and 80 parts of ethyl acetate;

[0072] A preparation method of a double-base nano oil and water fracturing temporary plugging agent, comprising the following preparation steps:

[0073] Add starch, acrylic acid, acrylamide, styrene, and composite reinforcing material to a solvent, stir evenly, add dibenzoyl peroxide and N,N'-methylenebisacrylamide, stir at 55 °C for 35 min until the starch is gelatinized, then stir and react at 75 °C for 4 h, cool to room temperature, wash with deionized water until solid precipitates, and after drying the solid, obtain an oil and water fracturing temporary plugging agent.

[0074] The composite reinforcing material is specifically prepared by the following steps:

[0075] A1. Add 22 mL of 1-bromohexadecane and 12 mL of 2-(dimethylamino)ethyl methacrylate to 120 mL of ethanol, stir evenly, raise the temperature to 55 °C, stir and react for 22 h, then after rotary evaporation, add acetone for recrystallization, take out, and wash with acetone 3 times to obtain a monomer;

[0076] A2. Add 6 g of sodium-based montmorillonite to 55 mL of deionized water, stir evenly, heat up to 35 °C, continue stirring until no aggregates are observed, add 0.6 g of monomer, stir for 12 h, wash the obtained product with ethanol to remove water and excess monomer, filter to obtain a precipitate, and dry the precipitate in an oven at 50 °C for 20 min to obtain modified montmorillonite;

[0077] A3. Immerse 12 g of shell powder into 55 mL of nitric acid solution with a mass fraction of 6%, immerse for 50 min, take out, wash with deionized water until the washing liquid is neutral, dry in an oven at 70 °C for 10 min, place in a pulverizer and pulverize, and pass through a 600-mesh sieve to obtain acidified shell powder;

[0078] A4. Add 4.3 g of zirconium oxychloride octahydrate to 22 mL of deionized water, stir evenly, add 12 mL of ammonia water with a mass fraction of 30%, 1.5 g of glycine, and 3 g of potassium chloride, stir evenly, add 6 g of acidified shell powder, stir at 85 °C for 10 min, place in a reaction kettle, carry out hydrothermal reaction at 185 °C for 24 h, cool to room temperature, filter, wash with deionized water until no chloride ions can be detected in the supernatant with silver nitrate solution, and dry in an oven at 80 °C for 3 h to obtain shell powder loaded with nano-zirconium dioxide;

[0079] A5. Add 7 g of shell powder loaded with nano-zirconium dioxide to 55 mL of N,N-dimethylformamide, stir evenly, add 3 g of stearic acid, stir until stearic acid dissolves, stir and react at 80 °C for 22 h, filter, wash with deionized water 3 times, and dry in an oven at 70 °C for 20 min to obtain a composite;

[0080] A6. Add 6 g of the composite and 2 g of modified montmorillonite to 55 mL of ethanol, stir evenly, stir at 60 °C for 2 h, heat up to 85 °C, stir until the ethanol evaporates, take out the solid, wash the solid with deionized water 3 times, and dry in an oven at 80 °C for 10 min to obtain a composite reinforcing material.

[0081] Comparative Example 1

[0082] A kind of double-base nano-oil and water fracturing temporary plugging agent, comprising the following raw materials in parts by mass: 12 parts of starch, 15 parts of acrylic acid, 22 parts of acrylamide, 12 parts of styrene, 6 parts of composite reinforcing material, 0.15 part of dibenzoyl peroxide, 0.6 part of N,N'-methylenebisacrylamide, and 80 parts of ethyl acetate;

[0083] A preparation method of a double-base nano-oil and water fracturing temporary plugging agent, comprising the following preparation steps:

[0084] Starch, acrylic acid, acrylamide, styrene and a composite reinforcing material are added to a solvent, stirred evenly, benzoyl peroxide and N,N'-methylenebisacrylamide are added, and after stirring at 55 °C for 35 min until the starch is gelatinized, the reaction is stirred at 75 °C for 4 h, cooled to room temperature, washed with deionized water until a solid precipitates, and after the solid is dried, an oil-water fracturing temporary plugging agent is obtained.

[0085] The composite reinforcing material is specifically prepared by the following steps:

[0086] A1. Immerse 12 g of shell powder into 55 mL of a nitric acid solution with a mass fraction of 6%, immerse for 50 min, take out, wash with deionized water until the washing liquid is neutral, dry in an oven at 70 °C for 10 min, place in a pulverizer, and pass through a 600-mesh sieve to obtain acidified shell powder;

[0087] A2. Add 4.3 g of zirconium oxychloride octahydrate to 22 mL of deionized water, stir evenly, add 12 mL of ammonia water with a mass fraction of 30%, 1.5 g of glycine and 3 g of potassium chloride, stir evenly, add 6 g of acidified shell powder, stir at 85 °C for 10 min, place in a reaction kettle, carry out a hydrothermal reaction at 185 °C for 24 h, cool to room temperature, filter, wash with deionized water until no chloride ions can be detected in the supernatant with silver nitrate solution, and dry in an oven at 80 °C for 3 h to obtain shell powder loaded with nano-zirconium dioxide;

[0088] A3. Add 7 g of shell powder loaded with nano-zirconium dioxide to 55 mL of N,N-dimethylformamide, stir evenly, add 3 g of stearic acid, stir until the stearic acid dissolves, stir and react at 80 °C for 22 h, filter, wash with deionized water 3 times, and dry in an oven at 70 °C for 20 min to obtain a composite;

[0089] A4. Add 6 g of the composite and 2 g of sodium-based montmorillonite to 55 mL of ethanol, stir evenly, stir at 60 °C for 2 h, raise the temperature to 85 °C, stir until the ethanol evaporates, take out the solid, wash the solid with deionized water 3 times, and dry in an oven at 80 °C for 10 min to obtain the composite reinforcing material.

[0090] Comparative Example 2

[0091] A double-base nano oil-water fracturing temporary plugging agent, comprising the following raw materials in parts by mass: 12 parts of starch, 15 parts of acrylic acid, 22 parts of acrylamide, 12 parts of styrene, 6 parts of composite reinforcing material, 0.15 part of benzoyl peroxide, 0.6 part of N,N'-methylenebisacrylamide, and 80 parts of ethyl acetate;

[0092] A preparation method of a double-base nano oil-water fracturing temporary plugging agent, comprising the following preparation steps:

[0093] Starch, acrylic acid, acrylamide, styrene and a composite reinforcing material are added to a solvent, stirred evenly, benzoyl peroxide and N,N'-methylenebisacrylamide are added, and after stirring at 55 °C for 35 min until the starch is gelatinized, the reaction is stirred at 75 °C for 4 h, cooled to room temperature, washed with deionized water until a solid precipitates, and after the solid is dried, an oil and water fracturing temporary plugging agent is obtained.

[0094] The composite reinforcing material is specifically prepared by the following steps:

[0095] A1. 22 mL of 1-bromohexadecane and 12 mL of 2-(dimethylamino)ethyl methacrylate are added to 120 mL of ethanol, stirred evenly, heated to 55 °C, and after stirring and reacting for 22 h, after rotary evaporation, recrystallized with acetone, taken out, and washed 3 times with acetone to obtain a monomer;

[0096] A2. 6 g of sodium montmorillonite is added to 55 mL of deionized water, stirred evenly, heated to 35 °C, and continuously stirred until no aggregates are observed, 0.6 g of the monomer is added, stirred for 12 h, the obtained product is washed with ethanol to remove water and excess monomer, and after filtration, a precipitate is obtained. The precipitate is dried in an oven at 50 °C for 20 min to obtain modified montmorillonite;

[0097] A3. 4.3 g of zirconium oxychloride octahydrate is added to 22 mL of deionized water, stirred evenly, 12 mL of 30% ammonia water, 1.5 g of glycine and 3 g of potassium chloride are added, stirred evenly, 6 g of shell powder is added, stirred at 85 °C for 10 min, placed in a reaction kettle, and hydrothermally reacted at 185 °C for 24 h, cooled to room temperature, filtered, and washed with deionized water until no chloride ions can be detected in the supernatant with silver nitrate solution, and dried in an oven at 80 °C for 3 h to obtain shell powder loaded with nano-zirconia;

[0098] A4. 7 g of shell powder loaded with nano-zirconia is added to 55 mL of N,N-dimethylformamide, stirred evenly, 3 g of stearic acid is added, stirred until the stearic acid is dissolved, and stirred and reacted at 80 °C for 22 h, filtered, washed 3 times with deionized water, and dried in an oven at 70 °C for 20 min to obtain a composite;

[0099] A5. 6 g of the composite and 2 g of modified montmorillonite are added to 55 mL of ethanol, stirred evenly, stirred at 60 °C for 2 h, heated to 85 °C, stirred until the ethanol evaporates, the solid is taken out, the solid is washed 3 times with deionized water, and dried in an oven at 80 °C for 10 min to obtain a composite reinforcing material.

[0100] Comparative Example 3

[0101] A double-base nano oil and water fracturing temporary plugging agent, comprising the following raw materials in parts by mass: 12 parts of starch, 15 parts of acrylic acid, 22 parts of acrylamide, 12 parts of styrene, 6 parts of composite reinforcing material, 0.15 part of dibenzoyl peroxide, 0.6 part of N,N'-methylenebisacrylamide, and 80 parts of ethyl acetate;

[0102] A preparation method of a double-base nano oil and water fracturing temporary plugging agent, comprising the following preparation steps:

[0103] Add starch, acrylic acid, acrylamide, styrene and composite reinforcing material into a solvent, stir evenly, add dibenzoyl peroxide and N,N'-methylenebisacrylamide, stir at 55 °C for 35 min until the starch is gelatinized, then stir and react at 75 °C for 4 h, cool to room temperature, wash with deionized water until solid precipitates, and after drying the solid, obtain the oil and water fracturing temporary plugging agent.

[0104] The composite reinforcing material is specifically prepared by the following steps:

[0105] A1. Add 22 mL of 1-bromohexadecane and 12 mL of 2-(dimethylamino)ethyl methacrylate into 120 mL of ethanol, stir evenly, heat up to 55 °C, stir and react for 22 h, then after rotary evaporation, add acetone for recrystallization, take out, wash with acetone 3 times to obtain the monomer;

[0106] A2. Add 6 g of sodium montmorillonite into 55 mL of deionized water, stir evenly, heat up to 35 °C, continue to stir until no aggregates are observed, add 0.6 g of monomer, stir for 12 h, wash the obtained product with ethanol to remove water and excess monomer, filter to obtain the precipitate, and dry the precipitate in an oven at 50 °C for 20 min to obtain the modified montmorillonite;

[0107] A3. After washing the shell powder with water to remove sludge, immerse 12 g of shell powder into 55 mL of a 6% nitric acid solution, immerse for 50 min, take out, wash with deionized water until the washing liquid is neutral, dry in an oven at 70 °C for 10 min, place in a pulverizer and pulverize, and pass through a 600-mesh sieve to obtain acidified shell powder;

[0108] A4. Add 7 g of acidified shell powder into 55 mL of N,N-dimethylformamide, stir evenly, add 3 g of stearic acid, stir until the stearic acid is dissolved, stir and react at 80 °C for 22 h, filter, wash with deionized water 3 times, and dry in an oven at 70 °C for 20 min to obtain the composite;

[0109] A5. Add 6 g of the composite and 2 g of modified montmorillonite to 55 mL of ethanol, stir evenly, stir at 60 °C for 2 h, raise the temperature to 85 °C, stir until the ethanol evaporates, take out the solid, wash the solid 3 times with deionized water, and dry it in an oven at 80 °C for 10 min to obtain the composite reinforcing material.

[0110] Comparative Example 4

[0111] A kind of double-base nano oil and water fracturing temporary plugging agent, comprising the following raw materials in parts by mass: 12 parts of starch, 15 parts of acrylic acid, 22 parts of acrylamide, 12 parts of styrene, 6 parts of composite reinforcing material, 0.15 parts of dibenzoyl peroxide, 0.6 parts of N,N'-methylenebisacrylamide, and 80 parts of ethyl acetate;

[0112] A preparation method of a double-base nano oil and water fracturing temporary plugging agent, comprising the following preparation steps:

[0113] Add starch, acrylic acid, acrylamide, styrene and the composite reinforcing material to a solvent, stir evenly, add dibenzoyl peroxide and N,N'-methylenebisacrylamide, stir at 55 °C for 35 min until the starch is gelatinized, and then stir and react at 75 °C for 4 h. Cool to room temperature, wash with deionized water until a solid precipitates, and after drying the solid, obtain the oil and water fracturing temporary plugging agent.

[0114] The composite reinforcing material is specifically prepared by the following steps:

[0115] A1. Add 22 mL of 1-bromohexadecane and 12 mL of 2-(dimethylamino)ethyl methacrylate to 120 mL of ethanol, stir evenly, raise the temperature to 55 °C, stir and react for 22 h, then after rotary evaporation, add acetone for recrystallization, take out, and wash 3 times with acetone to obtain the monomer;

[0116] A2. Add 6 g of sodium-based montmorillonite to 55 mL of deionized water, stir evenly, raise the temperature to 35 °C, continue to stir until no aggregates are observed, add 0.6 g of the monomer, stir for 12 h, wash the obtained product with ethanol to remove water and excess monomer, filter to obtain a precipitate, and dry the precipitate in an oven at 50 °C for 20 min to obtain the modified montmorillonite;

[0117] A3. After washing the shell powder with water to remove sludge, immerse 12 g of shell powder in 55 mL of a 6% nitric acid solution, immerse for 50 min, take out, wash with deionized water until the washing liquid is neutral, dry in an oven at 70 °C for 10 min, place in a pulverizer and pulverize, and pass through a 600-mesh sieve to obtain acidified shell powder;

[0118] A4. Add 4.3 g of zirconium oxychloride octahydrate to 22 mL of deionized water, stir evenly, add 12 mL of ammonia water with a mass fraction of 30%, 1.5 g of glycine, and 3 g of potassium chloride, stir evenly, add 6 g of acidified shell powder, stir at 85 °C for 10 min, place it in a reaction kettle, carry out hydrothermal reaction at 185 °C for 24 h, cool to room temperature, filter, wash with deionized water until no chloride ions can be detected in the supernatant with silver nitrate solution, and dry in an oven at 80 °C for 3 h to obtain shell powder loaded with nano-zirconia;

[0119] A5. Add 6 g of shell powder loaded with nano-zirconia and 2 g of modified montmorillonite to 55 mL of ethanol, stir evenly, stir at 60 °C for 2 h, raise the temperature to 85 °C, stir until the ethanol evaporates, take out the solid, wash the solid with deionized water 3 times, and dry in an oven at 80 °C for 10 min to obtain a composite reinforcing material.

[0120] Now, perform performance tests on the oil and water fracturing temporary plugging agents prepared in Examples 1-3 and Comparative Examples 1-4.

[0121] Dissolution time test: After mixing 5 g of the above-prepared oil and water fracturing temporary plugging agent and 100 g of fracturing fluid (84.6% clear water, 0.4% guar gum solution, and 15% hydrochloric acid), add them to the oil-water mixture of simulated formation water and kerosene, place them in a 60 °C water bath, and observe and record the time when the oil and water fracturing temporary plugging agent is completely dissolved.

[0122] Degradation rate detection: Add 5 g (denoted as m1) of the above-prepared oil and water fracturing temporary plugging agent to 50 mL of deionized water, place it in an oven at 60 °C for 24 h, filter, dry, weigh, and denote it as m2. The degradation rate = (m1 - m2) / m1 × 100%.

[0123] Salt tolerance performance: Add the above-prepared oil and water fracturing temporary plugging agent to formation water and 13.5 g / L sodium chloride solution respectively, fully absorb water and swell at 20 °C, take it out after 4 h and dry it with filter paper, and measure the shear resistance with a bulk expansion particle strength shear tester;

[0124] Compressive strength test: Extrude the above-prepared oil and water fracturing temporary plugging agent into a cylinder with a diameter of 6 mm and a height of 4 mm, and then perform the compressive strength test with a universal pressure tester;

[0125] Permeability recovery rate test: After passing the artificial core (with a known permeability of K0) through the fracturing fluid carrying the oil and water fracturing temporary plugging agent, measure the permeability K1 of the artificial core, and then measure the permeability K2 of the artificial core after backwashing with brine. The temporary plugging rate = (K0 - K1) / K0 × 100%, and the core permeability recovery rate = K2 / K0 × 100%. As shown in Table 1 below.

[0126] Table 1 Performance Detection of Oil and Water Fracturing Temporary Plugging Agents Prepared in Examples 1-3 and Comparative Examples 1-4

[0127] Project Dissolution time / h Shear resistance / N Compressive strength / MPa Temporary plugging rate / % Core permeability recovery rate / % Degradation rate / % Example 1 20 216 116.6 99.6 99.4 99.8 Example 2 22 220 118.5 99.8 99.6 99.9 Example 3 21 214 115.9 99.5 99.2 99.7 Comparative example 1 8 135 75.6 66.2 90.3 99.3 Comparative example 2 10 146 80.1 75.6 92.3 99.5 Comparative example 3 9 131 70.3 65.1 90.1 99.1 Comparative example 4 19 155 81.2 61.3 92.3 99.2

[0128] As can be seen from the data in Table 1, the oil and water fracturing temporary plugging agents prepared in Examples 1-3 have good compressive strength and plugging rate, and have good biodegradability and core permeability recovery rate, showing good temporary plugging and diversion effects. In Comparative Example 1, when the composite reinforcing material prepared by replacing the modified montmorillonite with sodium-based montmorillonite was added to the oil and water fracturing temporary plugging agent, its salt tolerance decreased and the dissolution rate was fast, which proved that the monomer formed a hydrophobic network structure on the surface of exfoliated sodium-based montmorillonite, avoiding the too-fast water absorption and swelling rate of the fracturing temporary plugging agent, resulting in the agglomeration and failure of the fracturing temporary plugging agent and affecting the plugging efficiency. Moreover, the monomer also has good salt tolerance.

[0129] In Comparative Example 2, when the composite reinforcing material prepared by replacing the acidified shell powder with shell powder was added to the oil and water fracturing temporary plugging agent, its compressive strength and plugging efficiency decreased, indicating that the high specific surface area and pore structure of the acidified shell powder increased the contact area between the shell powder and the fracture, improved the density of the temporary plugging layer, and was conducive to the formation of nano-zirconia on the surface and pores of the acidified shell powder.

[0130] In Comparative Example 3, when the composite reinforcing material prepared by replacing the shell powder loaded with nano-zirconia with acidified shell powder was added to the oil and water fracturing temporary plugging agent, its compressive strength and plugging efficiency decreased, and the dissolution rate was fast, indicating that the formation of nano-zirconia on the surface and pores of the acidified shell powder reduced the water absorption rate of the acidified shell powder, avoiding the relatively fast water absorption rate of the shell powder and affecting the effective temporary plugging of the fracturing temporary plugging agent. Moreover, nano-zirconia can effectively improve the compressive strength of the fracturing temporary plugging agent.

[0131] In Comparative Example 4, when the composite reinforcing material prepared by replacing the composite with shell powder loaded with nano-zirconia was added to the oil and water fracturing temporary plugging agent, it was proved that the stearic acid grafted on the surface of the shell powder loaded with nano-zirconia could entangle with the long alkyl chains on the surface of the modified montmorillonite to form a hydrophobic channel, making it difficult for the water adsorbed inside the oil and water fracturing temporary plugging agent to overflow, providing a large amount of water absorption and retention space for the oil and water fracturing temporary plugging agent, and avoiding the dehydration of the colloidal particles formed by the water absorption and swelling of the oil and water fracturing temporary plugging agent, which makes the colloidal particles become fragile and easy to break, affecting the plugging effect.

[0132] In the description of the specification, the description with reference to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0133] The above content is only an illustration and explanation of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should fall within the protection scope of the present invention.

Claims

1. A dual-base nano oil-water fracturing temporary plugging agent, characterized in that: The method comprises the following raw materials in parts by weight: 10-12 parts of starch, 10-15 parts of acrylic acid, 20-22 parts of acrylamide, 10-12 parts of styrene, 5-6 parts of composite reinforcing material, 0.05-0.15 parts of initiator, 0.5-0.6 parts of cross-linking agent, and 60-80 parts of solvent; The composite reinforcement material is prepared by mixing shell powder loaded with nano zirconium dioxide, modified montmorillonite and stearic acid; The shell powder loaded with nano zirconium dioxide is prepared by subjecting shell powder to an acidification treatment, and then mixing it with zirconium oxychloride octahydrate, and then subjecting it to a hydrothermal reaction; The modified montmorillonite is prepared by reacting 1-bromohexadecane with 2-(dimethylamino)ethyl methacrylate and then mixing with montmorillonite; The composite reinforced material is specifically prepared by the following steps: A1. Add 1-bromohexadecane and 2-(dimethylamino)ethyl methacrylate to ethanol, stir evenly, heat to 45-55°C, stir and react for 20-22h, evaporate by rotary evaporation, add acetone for recrystallization, take out, wash and obtain a monomer; A2. The montmorillonite was added to deionized water, stirred evenly, the monomer was added, and stirring was continued for 10-12 hours. After washing with ethanol, the precipitate was filtered and dried to obtain the modified montmorillonite; A3. The shell powder is immersed in a nitric acid solution having a mass fraction of 5-6%, immersed for 40-50min, removed, washed, dried, placed in a grinder, and sieved through a 500-600 mesh screen to obtain acidified shell powder; A4. Add zirconium oxychloride octahydrate to deionized water, stir evenly, add 25-30% by mass of ammonia water, glycine and potassium chloride, stir evenly, add acidified shell powder, stir evenly, place in a reactor, perform hydrothermal reaction at 175-185°C for 20-24h, cool to room temperature, filter, wash and dry to obtain shell powder loaded with nano zirconium dioxide; A5. The shell powder loaded with nano zirconium dioxide is added to N, N-dimethylformamide, stirred evenly, stearic acid is added, stirred until the stearic acid is dissolved, stirred at 70-80 ° C for 20-22h, filtered, washed, and dried to obtain a composite; A6. Add the composite and modified montmorillonite to ethanol, stir evenly, stir at 50-60°C for 1-2h, heat to 80-85°C, stir until ethanol evaporates, take out the solid, wash and dry the solid to obtain a composite reinforced material.

2. The double-base nano oil-water fracturing temporary plugging agent according to claim 1, characterized in that: In step A1, the volume ratio of 1-bromohexadecane, 2-(dimethylamino)ethyl methacrylate and ethanol is (18-22):(10-12):(80-120).

3. The double-base nano oil-water fracturing temporary plugging agent according to claim 1, characterized in that: In step A2, the ratio of the amount of montmorillonite, deionized water and monomer is (4-6) g: (45-55) mL: (0.3-0.6) g.

4. The double-base nano oil-water fracturing temporary plugging agent according to claim 1, characterized in that: In step A3, the ratio of the shell powder to the nitric acid solution is (8-12) g: (45-55) mL.

5. The double-base nano oil-water fracturing temporary plugging agent according to claim 1, characterized in that: In step A4, the dosage ratio of zirconium oxychloride octahydrate, deionized water, ammonia water, glycine, potassium chloride and acidified shell powder is (3.9-4.3) g: (18-22) mL: (8-12) mL: (0.5-1.5) g: (1-3) g: (5-6) g.

6. The double-base nano oil-water fracturing temporary plugging agent according to claim 1, characterized in that: In step A5, the amount ratio of the shell powder loaded with nano zirconium dioxide, N,N-dimethylformamide and stearic acid is (5-7) g: (45-55) mL: (2-3) g.

7. The double-base nano oil-water fracturing temporary plugging agent according to claim 1, characterized in that: In step A6, the ratio of the composite, modified montmorillonite and ethanol is (5-6 g):(1-2) g:(45-55) mL.

8. The double-base nano oil-water fracturing temporary plugging agent according to claim 1, characterized in that: Prepared by the following steps: Add starch, acrylic acid, acrylamide, styrene and composite reinforcing material to the solvent, stir evenly, add initiator and cross-linking agent, stir at 45-55°C for 25-35 minutes, stir and react at 70-75°C for 2-4 hours, cool to room temperature, wash and precipitate solids, and dry the solids to obtain an oil-water fracturing temporary plugging agent.