Temperature-resistant and compression-resistant temporary plugging agent as well as preparation method and application thereof

Abstract

The invention relates to the field of oilfield chemical industry. The invention relates to a temporary plugging agent, in particular to a temperature-resistant and compression-resistant temporary plugging agent and a preparation method and application thereof. The temperature-resistant and compression-resistant temporary plugging agent comprises the following raw material components in parts by weight: 60-80 parts of polyimide; 5-10 parts of calcium carbonate nanofibers of which the surfaces are assembled with amphiphilic block copolymers; 0.2 to 4 parts of an auxiliary agent; wherein the polyimide is prepared by taking biphenyl tetracarboxylic dianhydride, p-phenylenediamine and phenylacetylene phthalic anhydride as polymerization reaction raw materials; the amphiphilic block copolymer assembled on the surface of the calcium carbonate nanofiber is polystyrene-b-polyacrylic acid. The temperature-resistant and compression-resistant temporary plugging agent provided by the invention has excellent high temperature resistance, compression resistance and plugging capacity, can be quickly hydrolyzed and crushed after temporary plugging is finished, can realize quick plugging removal, and is suitable for a high-temperature and high-pressure mining environment with the formation temperature (use environment) of 281-295 DEG C and the formation pressure of more than or equal to 130 MPa.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical engineering. More specifically, it relates to a temperature- and pressure-resistant temporary plugging agent, its preparation method, and its application. Background Technology

[0002] With the continued growth of global energy demand, conventional high-permeability oil and gas reservoirs are becoming increasingly depleted due to long-term exploitation, resulting in significant production decline. Meanwhile, abundant low-permeability oil and gas reservoirs (accounting for more than two-thirds of my country's geological oil reserves) face extremely high extraction difficulties due to their dense formations and high flow resistance. Against this backdrop, fracturing technology, as a key means of enhancing oil and gas well production and water injection well injection, plays an irreplaceable role in improving reservoir utilization. This technology creates or expands fractures in the formation, establishing efficient channels for oil and gas flow, and is a core technology for the effective development of low-permeability oil and gas reservoirs and the enhancement and stimulation of high-permeability oil and gas reservoirs.

[0003] In fracturing technology, temporary plugging agents are key materials for achieving precise reservoir stimulation. Their working principle involves entering the opened fractures with the fracturing fluid and forming a low-permeability barrier through physical sealing or chemical action, forcing subsequent pressure to redirect towards the insufficiently stimulated area, thereby opening a new fracture network. This "in-fracture temporary plugging and redirection" process can significantly increase the reservoir stimulation volume. As oil and gas exploration expands into deeper and ultra-deep formations (such as shale gas and hot dry rock, and other unconventional resources), downhole temperature and pressure conditions are becoming increasingly demanding, with temperatures reaching 280-300℃ and pressures exceeding 100MPa. This places extremely high demands on the temperature resistance, pressure resistance, and environmental performance of temporary plugging agents. Different well conditions vary significantly; for example, shale gas wells require temporary plugging agents to remain effective at 150-200℃ for 3-5 days before self-degradation, while hot dry rock development requires materials to withstand pressures of at least 50MPa in ultra-high temperature environments above 250℃. These complex and diverse operating conditions impose multifaceted and extremely stringent requirements on the performance of temporary plugging agents.

[0004] Currently available temporary plugging agents have significant limitations under extreme conditions. Traditional water-soluble temporary plugging agents (such as bone glue and modified starch systems) generally have a temperature resistance limit below 100℃; acid-pressurization temporary plugging agents, while able to withstand formation temperatures of 100℃ and achieve a plugging rate exceeding 96%, lack high-temperature stability. Although polyimide-based temporary plugging agents impart good thermal stability and mechanical strength through the imide rings in the molecular backbone, they may experience a 10% mass loss above 250℃, and their compressive strength decreases significantly with increasing temperature. Existing technologies generally suffer from the following problems: First, insufficient temperature and compressive strength; conventional polymeric temporary plugging agents are prone to thermal degradation or softening above 160℃; second, a contradiction exists between plugging strength and unplugging efficiency; high-strength metal alloy temporary plugging agents require strong acids for unplugging and have high residue rates, while easily unpluggable water-soluble polymers lack sufficient compressive strength; third, poor controllability of unplugging, with degradation behavior largely controlled by temperature alone, making it difficult to precisely regulate the unplugging time.

[0005] In summary, current temporary plugging agent technologies are insufficient to meet the extreme operating conditions required for the development of deep / ultra-deep oil and gas reservoirs and geothermal resources. Especially under conditions exceeding 280℃ and 50MPa, existing products often exhibit significant performance degradation, leading to plugging failure or reservoir damage. Therefore, developing a new generation of temporary plugging agents capable of withstanding ultra-high temperatures above 280℃, possessing excellent pressure resistance (e.g., above 130MPa), and exhibiting controllable unplugging behavior has become a key research direction in the fields of oil and gas field chemical materials and fracturing engineering. Through innovative applications of high-performance polymer matrices such as polyimide, combined with new material design concepts such as fiber reinforcement and nanocomposite materials, breakthroughs are expected in ultra-high temperature and high pressure temporary plugging agent technology, promoting the efficient and clean development of low-permeability oil and gas reservoirs and unconventional energy sources in my country. Summary of the Invention

[0006] Based on the above-mentioned shortcomings, the first objective of this invention is to provide a temperature- and pressure-resistant temporary plugging agent. This temperature- and pressure-resistant temporary plugging agent possesses both excellent high-temperature resistance and pressure resistance, making it suitable for fracturing operations with formation temperatures of 281-295℃ and ground pressures exceeding 130MPa.

[0007] The second objective of this invention is to provide a method for preparing the temperature-resistant and pressure-resistant temporary plugging agent as described above.

[0008] A third objective of this invention is to provide an application of the temperature-resistant and pressure-resistant temporary plugging agent described above in oil and gas extraction or geothermal extraction.

[0009] To achieve the first objective mentioned above, the present invention adopts the following technical solution: This invention discloses a temperature-resistant and pressure-resistant temporary plugging agent, which comprises the following raw material components by weight: 60-80 parts of polyimide; 5-10 parts of calcium carbonate nanofibers with amphiphilic block copolymers assembled on their surface; 0.2-4 parts of auxiliary agent; The polyimide is prepared using biphenyltetracarboxylic dianhydride, p-phenylenediamine, and phenylacetylene phthalic anhydride as polymerization raw materials. The amphiphilic block copolymer assembled on the surface of calcium carbonate nanofibers is polystyrene-b-polyacrylic acid.

[0010] Furthermore, the graphene-modified polyimide is prepared according to the following steps: Biphenyltetracarboxylic dianhydride, p-phenylenediamine, and phenylacetylene phthalic anhydride were dissolved in dimethyl sulfoxide at room temperature. The reaction system was then heated to 80-100°C and refluxed to obtain polyimide. After filtration and drying, polyimide powder was obtained.

[0011] The matrix resin polyimide powder of the present invention is prepared using biphenyltetracarboxylic dianhydride as an aromatic dianhydride monomer, p-phenylenediamine as an aromatic diamine monomer, and phenylacetylene phthalic anhydride as a capping agent. All three contain aryl benzene ring structures. The polyimide structure prepared has a high proportion of benzene ring structures, which is much higher than that of polyimides commonly used in the field, resulting in better thermal stability of the polyimide powder prepared by the present invention.

[0012] Furthermore, the polyimide has a melting point higher than 330°C and a weight-average molecular weight of 15,000-35,000, preferably a melting point of 335-355°C, exhibiting excellent thermal stability.

[0013] Furthermore, the molar ratio of biphenyltetracarboxylic dianhydride, p-phenylenediamine, and phenylacetylene phthalic anhydride is 1:1.2:0.2.

[0014] Furthermore, the calcium carbonate nanofibers with amphiphilic block copolymers assembled on their surface are prepared according to the following steps: Calcium carbonate nanofibers were dispersed in ethanol, a coupling agent was added, and the mixture was stirred at 25-60℃ for 1-2 hours to obtain surface-modified calcium carbonate nanofibers. Then, the amphiphilic block copolymer polystyrene-b-polyacrylic acid was added, and the mixture was stirred for another 1-2 hours to obtain the final product.

[0015] The calcium carbonate nanofibers of this invention are grafted with a coupling agent (e.g., KH570) to reduce the surface energy of the calcium carbonate nanofibers, changing the surface from hydrophilic to hydrophobic. Furthermore, this invention creatively utilizes the amphiphilic block copolymer polystyrene-b-polyacrylic acid to self-assemble on the surface of the surface-modified calcium carbonate nanofibers, resulting in calcium carbonate nanofibers with an amphiphilic block copolymer assembled on their surface. One end of the amphiphilic block copolymer polystyrene-b-polyacrylic acid is connected to the calcium carbonate nanofiber, and the other end is connected to polyimide; specifically, the lipophilic end of the polystyrene-b-polyacrylic acid first self-assembles on the surface of the surface-modified calcium carbonate nanofiber, and then the hydrophilic end of the polystyrene-b-polyacrylic acid connects to the polar groups of the polyimide, making the connection between the calcium carbonate nanofiber and the matrix resin polyimide more compact, improving the stability of the temporary plugging agent, and enabling it to withstand high temperatures in high-temperature environments. This directional assembly and interfacial bonding mode based on a specific chemical structure is difficult to achieve with ordinary block copolymers or other amphiphilic block copolymers. In particular, the rigid aromatic ring structure of polystyrene segments and polyimide molecular chains can produce a π-π stacking effect, while polyacrylic acid segments have ionization and swelling properties in acidic environments. The synergistic effect of the two not only significantly enhances the interfacial bonding strength between the fiber and the matrix, but also improves the overall stability of the temporary plugging agent under high temperature and high pressure.

[0016] The calcium carbonate nanofibers of this invention can be prepared by methods in the prior art, particularly by electrospinning. The calcium carbonate used in this invention is in nanofiber form, unlike the granular calcium carbonate powder used in the prior art. In this invention, the nanofiber-like calcium carbonate is more uniformly dispersed in polyimide through a coupling agent (e.g., KH570) and the amphiphilic block polymer polystyrene-b-polyacrylic acid, and the bond with the polyimide is tighter. Compared to granular calcium carbonate, the nanofiber-like calcium carbonate, due to its longer fiber length, enhances the strength of the resin through its bridging effect, thus improving the compressive strength of the temporary plugging agent. Moreover, during deblocking under acidic conditions, the uniformly dispersed nanofiber-like calcium carbonate, due to its larger specific surface area and longer fiber length, reacts more readily with acid, generating more voids after the reaction, accelerating the hydrolysis and breakup of the polyimide, and increasing the deblocking speed.

[0017] Furthermore, the calcium carbonate nanofibers have a length of 40-60 μm and a diameter of 80-150 nm; The polystyrene-b-polyacrylic acid fragment has a molecular weight of 13,000-17,000 g / mol and a molecular weight of 1,200-2,000 g / mol. The coupling agent is KH570.

[0018] Furthermore, the mass ratio of the calcium carbonate nanofibers, coupling agent, and polystyrene-b-polyacrylic acid is 10:1-3:1-3.

[0019] Furthermore, by weight, the additives include 0.1-2 parts lubricant and 0.1-2 parts antioxidant.

[0020] Furthermore, the lubricant is selected from one or more of polyethylene wax, polyamide wax, hydrogenated castor oil, and paraffin wax.

[0021] Furthermore, the antioxidant is selected from one or more of antioxidants DNP, MB, and 168.

[0022] To achieve the second objective mentioned above, the present invention adopts the following technical solution: This invention discloses a method for preparing the temperature-resistant and pressure-resistant temporary plugging agent as described above, comprising the following steps: Polyimide, calcium carbonate nanofibers with amphiphilic block copolymers assembled on their surfaces, and additives are mixed according to the formula. The mixture is then extruded through a twin-screw extruder, pelletized, dried, and cryogenically pulverized to obtain a temperature-resistant and pressure-resistant temporary plugging agent with a particle size of 0.075-2.0 mm.

[0023] In this invention, the twin-screw extruder is used for extrusion, pelletizing, and drying, all of which are conventional operating methods in the prior art and will not be described in detail here. Preferably, the temperature for extrusion is 330-370℃.

[0024] Furthermore, the cryogenic pulverization is carried out in a cryogenic pulverizer and cooled by liquid nitrogen, with the cryogenic pulverization temperature ≤ -50℃.

[0025] To achieve the third objective mentioned above, the present invention adopts the following technical solution: This invention discloses the application of the temperature-resistant and pressure-resistant temporary plugging agent described above in oil and gas extraction or geothermal extraction. The temperature-resistant and pressure-resistant temporary plugging agent is suitable for extraction environments with formation temperatures of 281-295℃ and formation pressures of 130MPa or higher.

[0026] The beneficial effects of this invention are as follows: The temporary plugging agent of the present invention has good high temperature resistance, excellent pressure resistance and plugging ability, and can be used in high temperature environment (281-295℃) and high pressure environment (≥130MPa); it can be rapidly hydrolyzed and broken down after the temporary plugging ends, so as to achieve rapid unblocking.

[0027] The polyimide powder of the present invention is prepared using biphenyltetracarboxylic dianhydride as an aromatic dianhydride monomer, p-phenylenediamine as an aromatic diamine monomer, and phenylacetylene phthalic anhydride as a capping agent, and has good thermal stability. The calcium carbonate nanofibers of the present invention are grafted with KH570 on their surface and connected to the resin matrix polyimide through the amphiphilic block polymer polystyrene-b-polyacrylic acid, which improves stability and enables them to withstand high temperatures in high-temperature environments. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this article can be purchased from the market or prepared by existing methods.

[0030] Example 1 This example provides a method for preparing a temporary plugging agent, including the following steps: Step (1): Biphenyltetracarboxylic dianhydride, p-phenylenediamine and phenylacetylene phthalic anhydride in a molar ratio of 1:1.2:0.2 are dissolved in dimethyl sulfoxide at room temperature. The reaction system is then heated to 90°C and refluxed to obtain polyimide. After filtration and drying, polyimide powder is obtained. Step (2): Prepare calcium carbonate nanofibers, KH570 and polystyrene-b-polyacrylic acid according to a mass ratio of 10:2:2; disperse calcium carbonate nanofibers with a fiber length of 50 μm and a diameter of 90 nm in ethanol, add coupling agent KH570, stir at 30 °C for 2 h to obtain surface-modified calcium carbonate nanofibers, then add amphiphilic block copolymer polystyrene-b-polyacrylic acid (the molecular weight of polystyrene fragment in polystyrene-b-polyacrylic acid is 13000 g / mol, and the molecular weight of polyacrylic acid fragment is 1500 g / mol), continue stirring for 2 h to obtain calcium carbonate nanofibers with amphiphilic block copolymer assembled on the surface; Step (3): By weight, 80 parts of the polyimide powder obtained in step (1), 10 parts of the calcium carbonate nanofibers with amphiphilic block copolymers on the surface obtained in step (2), 1 part of the lubricant polyethylene wax and 1 part of the antioxidant DNP are mixed, extruded by a twin-screw extruder, pelletized and dried to obtain extruded granules. Step (4) involves cryogenically grinding the extruded particles from step (3) at -50°C in a cryogenic pulverizer to obtain a temporary blockage agent with a particle size of 0.075 mm to 2.0 mm.

[0031] Example 2 This example provides a method for preparing a temporary plugging agent, including the following steps: Step (1): Biphenyltetracarboxylic dianhydride, p-phenylenediamine and phenylacetylene phthalic anhydride in a molar ratio of 1:1.2:0.2 are dissolved in dimethyl sulfoxide at room temperature. The reaction system is then heated to 90°C and refluxed to obtain polyimide. After filtration and drying, polyimide powder is obtained. Step (2): Prepare calcium carbonate nanofibers, KH570 and polystyrene-b-polyacrylic acid according to a mass ratio of 10:2:2; disperse calcium carbonate nanofibers with a fiber length of 50 μm and a diameter of 90 nm in ethanol, add coupling agent KH570, stir at 40 °C for 2 h to obtain surface-modified calcium carbonate nanofibers, then add amphiphilic block copolymer polystyrene-b-polyacrylic acid (the molecular weight of polystyrene fragment in polystyrene-b-polyacrylic acid is 15000 g / mol, and the molecular weight of polyacrylic acid fragment is 1200 g / mol), continue stirring for 2 h to obtain calcium carbonate nanofibers with amphiphilic block copolymer assembled on the surface; Step (3): By weight, 60 parts of the polyimide powder obtained in step (1), 10 parts of the calcium carbonate nanofibers with amphiphilic block copolymers on the surface obtained in step (2), 1 part of the lubricant polyethylene wax and 1 part of the antioxidant DNP are mixed; the mixture is extruded through a twin-screw extruder, granulated and dried to obtain extruded granules. Step (4) involves cryogenically grinding the extruded particles from step (3) at -50°C in a cryogenic pulverizer to obtain a temporary blockage agent with a particle size of 0.075 mm to 2.0 mm.

[0032] Example 3 This example provides a method for preparing a temporary plugging agent, including the following steps: Step (1): Biphenyltetracarboxylic dianhydride, p-phenylenediamine and phenylacetylene phthalic anhydride in a molar ratio of 1:1.2:0.2 are dissolved in dimethyl sulfoxide at room temperature. The reaction system is then heated to 90°C and refluxed to obtain polyimide. After filtration and drying, polyimide powder is obtained. Step (2): Prepare calcium carbonate nanofibers, KH570 and polystyrene-b-polyacrylic acid according to a mass ratio of 10:2:2; disperse calcium carbonate nanofibers with a fiber length of 50 μm and a diameter of 90 nm in ethanol, add coupling agent KH570, stir at 50 °C for 2 h to obtain surface-modified calcium carbonate nanofibers, then add amphiphilic block copolymer polystyrene-b-polyacrylic acid (the molecular weight of polystyrene fragment in polystyrene-b-polyacrylic acid is 16000 g / mol, and the molecular weight of polyacrylic acid fragment is 1600 g / mol), continue stirring for 2 h to obtain calcium carbonate nanofibers with amphiphilic block copolymer assembled on the surface; Step (3): By weight, 60 parts of the polyimide powder obtained in step (1), 6 parts of the calcium carbonate nanofibers with amphiphilic block copolymers on the surface obtained in step (2), 1 part of the lubricant polyethylene wax and 1 part of the antioxidant DNP are mixed; the mixture is extruded through a twin-screw extruder, granulated and dried to obtain extruded granules. Step (4) involves cryogenically grinding the extruded particles from step (3) at -50°C in a cryogenic pulverizer to obtain a temporary blockage agent with a particle size of 0.075 mm to 2.0 mm.

[0033] Example 4 This example provides a method for preparing a temporary plugging agent, including the following steps: Step (1): Biphenyltetracarboxylic dianhydride, p-phenylenediamine and phenylacetylene phthalic anhydride in a molar ratio of 1:1.2:0.2 are dissolved in dimethyl sulfoxide at room temperature. The reaction system is then heated to 90°C and refluxed to obtain polyimide. After filtration and drying, polyimide powder is obtained. Step (2): Prepare calcium carbonate nanofibers, KH570 and polystyrene-b-polyacrylic acid according to a mass ratio of 10:2:2; disperse calcium carbonate nanofibers with a fiber length of 50 μm and a diameter of 90 nm in ethanol, add coupling agent KH570, stir at 60 °C for 2 h to obtain surface-modified calcium carbonate nanofibers, then add amphiphilic block copolymer polystyrene-b-polyacrylic acid (the molecular weight of polystyrene fragment in polystyrene-b-polyacrylic acid is 17000 g / mol, and the molecular weight of polyacrylic acid fragment is 1800 g / mol), continue stirring for 2 h to obtain calcium carbonate nanofibers with amphiphilic block copolymer assembled on the surface; Step (3): By weight, 80 parts of the polyimide powder obtained in step (1), 5 parts of the calcium carbonate nanofibers with amphiphilic block copolymers on the surface obtained in step (2), 1 part of the lubricant polyethylene wax and 1 part of the antioxidant DNP are mixed; the mixture is extruded through a twin-screw extruder, granulated and dried to obtain extruded granules. Step (4) involves cryogenically grinding the extruded particles from step (3) at -50°C in a cryogenic pulverizer to obtain a temporary blockage agent with a particle size of 0.075 mm to 2.0 mm.

[0034] Example 5 This example provides a method for preparing a temporary plugging agent, including the following steps: Step (1): Biphenyltetracarboxylic dianhydride, p-phenylenediamine and phenylacetylene phthalic anhydride in a molar ratio of 1:1.2:0.2 are dissolved in dimethyl sulfoxide at room temperature. The reaction system is then heated to 90°C and refluxed to obtain polyimide. After filtration and drying, polyimide powder is obtained. Step (2): Prepare calcium carbonate nanofibers, KH570 and polystyrene-b-polyacrylic acid according to a mass ratio of 10:2:2; disperse calcium carbonate nanofibers with a fiber length of 50 μm and a diameter of 90 nm in ethanol, add coupling agent KH570, stir at 30 °C for 2 h to obtain surface-modified calcium carbonate nanofibers, then add amphiphilic block copolymer polystyrene-b-polyacrylic acid (the molecular weight of polystyrene fragment in polystyrene-b-polyacrylic acid is 17000 g / mol, and the molecular weight of polyacrylic acid fragment is 2000 g / mol), continue stirring for 2 h to obtain calcium carbonate nanofibers with amphiphilic block copolymer assembled on the surface; Step (3): By weight, 70 parts of the polyimide powder obtained in step (1), 6 parts of the calcium carbonate nanofibers with amphiphilic block copolymers on the surface obtained in step (2), 1 part of the lubricant polyethylene wax and 1 part of the antioxidant DNP are mixed; the mixture is extruded through a twin-screw extruder, granulated and dried to obtain extruded granules. Step (4) involves cryogenically grinding the extruded particles from step (3) at -50°C in a cryogenic pulverizer to obtain a temporary blockage agent with a particle size of 0.075 mm to 2.0 mm.

[0035] Example 6 This example provides a method for preparing a temporary plugging agent. The preparation method is the same as in Example 1, except that in step (3), 80 parts of polyimide powder are mixed with 5 parts of modified calcium carbonate nanofibers.

[0036] Comparative Example 1 This example provides a method for preparing a temporary plugging agent, including the following steps: By weight, 70 parts of polyimide powder (excluding aryl benzene ring structure), 6 parts of calcium carbonate powder with a particle size of 50μm, 1 part of lubricant polyethylene wax and 1 part of antioxidant DNP are mixed, extruded by a twin-screw extruder, pelletized and dried to obtain extruded granules; the extruded granules are then cryogenically pulverized at -50℃ in a cryogenic pulverizer to obtain a temporary plugging agent with a particle size of 0.075mm-2.0mm.

[0037] Comparative Example 2 This example provides a method for preparing a temporary plugging agent. The preparation method is the same as in Example 1, except that in step (2), the coupling agent KH570 is replaced with an equal mass of silane coupling agent KH550.

[0038] Comparative Example 3 This example provides a method for preparing a temporary plugging agent. The preparation method is the same as in Example 1, except that in step (2), the amphiphilic block copolymer polystyrene-b-polyacrylic acid is replaced with an equal mass of polystyrene-b-polyethylene glycol.

[0039] Comparative Example 4 This example provides a method for preparing a comparative temporary plugging agent. The preparation method is the same as in Example 1, except that in step (1), the monomer biphenyltetracarboxylic dianhydride is replaced with an equimolar amount of aliphatic dianhydride-succinic anhydride, which is then polymerized with p-phenylenediamine to prepare polyimide.

[0040] Performance testing Temporary plugging agent particles with a particle size of 0.075-2.0 mm obtained after extrusion processing and cryogenic pulverization in Examples 1-5 and Comparative Example 1 were heat-treated for 120 hours in hot water at 285℃ (saturated vapor pressure 6.9-7.0 MPa), 295℃ (saturated vapor pressure 7.9-8.0 MPa), and 305℃ (saturated vapor pressure 9.2-9.3 MPa). The mass loss rate and compressive strength were then tested. The test results are shown in Table 1.

[0041] Table 1

[0042] It can be seen that Examples 1-5 of the present invention can withstand high-temperature environments of 285°C and 295°C, but at 305°C, there is a significant mass loss, making them unsuitable for use at temperatures above 305°C. Therefore, the temporary plugging agent composition of the present invention can be used at 281-295°C. Comparative Examples 1-4 exhibit significant mass loss in the temperature range of 285°C to 295°C, making them unsuitable for high-temperature use.

[0043] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A temperature- and pressure-resistant temporary plugging agent, characterized in that, By weight, it includes the following raw material components: 60-80 parts of polyimide; 5-10 parts of calcium carbonate nanofibers with amphiphilic block copolymers assembled on their surface; 0.2-4 parts of auxiliary agent; The polyimide is prepared using biphenyltetracarboxylic dianhydride, p-phenylenediamine, and phenylacetylene phthalic anhydride as polymerization raw materials. The amphiphilic block copolymer assembled on the surface of calcium carbonate nanofibers is polystyrene-b-polyacrylic acid.

2. The temperature-resistant and pressure-resistant temporary plugging agent according to claim 1, characterized in that, The graphene-modified polyimide was prepared according to the following steps: Biphenyltetracarboxylic dianhydride, p-phenylenediamine, and phenylacetylene phthalic anhydride were dissolved in dimethyl sulfoxide at room temperature. The reaction system was then heated to 80-100°C and refluxed to obtain polyimide. After filtration and drying, polyimide powder was obtained.

3. The temperature-resistant and pressure-resistant temporary plugging agent according to claim 1, characterized in that, The polyimide has a melting point above 330°C and a weight-average molecular weight of 15,000-35,000.

4. The temperature-resistant and pressure-resistant temporary plugging agent according to claim 2, characterized in that, The molar ratio of biphenyltetracarboxylic dianhydride, p-phenylenediamine, and phenylacetylene phthalic anhydride is 1:1.2:0.

2.

5. The temperature-resistant and pressure-resistant temporary plugging agent according to claim 1, characterized in that, The calcium carbonate nanofibers with amphiphilic block copolymers assembled on their surfaces were prepared according to the following steps: Calcium carbonate nanofibers were dispersed in ethanol, a coupling agent was added, and the mixture was stirred at 25-60℃ for 1-2 hours to obtain surface-modified calcium carbonate nanofibers. Then, the amphiphilic block copolymer polystyrene-b-polyacrylic acid was added, and the mixture was stirred for another 1-2 hours to obtain the final product.

6. The temperature-resistant and pressure-resistant temporary plugging agent according to claim 5, characterized in that, The calcium carbonate nanofibers have a length of 40-60 μm and a diameter of 80-150 nm. The polystyrene-b-polyacrylic acid fragment has a molecular weight of 13,000-17,000 g / mol and a molecular weight of 1,200-2,000 g / mol. The coupling agent is KH570.

7. The temperature-resistant and pressure-resistant temporary plugging agent according to claim 5, characterized in that, The mass ratio of the calcium carbonate nanofibers, coupling agent, and polystyrene-b-polyacrylic acid is 10:1-3:1-3.

8. The temperature-resistant and pressure-resistant temporary plugging agent according to claim 1, characterized in that, The additives comprise, by weight, 0.1-2 parts lubricant and 0.1-2 parts antioxidant; Preferably, the lubricant is selected from one or more of polyethylene wax, polyamide wax, hydrogenated castor oil, and paraffin wax; Preferably, the antioxidant is selected from one or more of antioxidants DNP, MB, and 168.

9. The method for preparing the temperature-resistant and pressure-resistant temporary plugging agent according to any one of claims 1-8, characterized in that, Includes the following steps: Polyimide, calcium carbonate nanofibers with amphiphilic block copolymers assembled on their surfaces, and additives are mixed according to the formula. The mixture is then extruded through a twin-screw extruder, pelletized, dried, and cryogenically pulverized to obtain a temperature-resistant and pressure-resistant temporary plugging agent with a particle size of 0.075-2.0 mm.

10. The application of the temperature-resistant and pressure-resistant temporary plugging agent according to any one of claims 1-8 in oil and gas extraction or geothermal extraction, characterized in that, The temperature-resistant and pressure-resistant temporary plugging agent is suitable for mining environments with formation temperatures of 281-295℃ and formation pressures of 130MPa or higher.

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