Strong-polarity modified polyester fiber for preventing backflow of proppant and preparation method of strong-polarity modified polyester fiber

Abstract

The invention discloses a strong-polarity modified polyester fiber for preventing backflow of a proppant and a preparation method of the strong-polarity modified polyester fiber, and relates to the technical field of petrochemical engineering, and the method comprises three key steps of high-molecular polymerization, spinning and surface modification. The preparation method comprises the following steps: firstly, preparing a high-molecular polymer, selecting phthalic acid, ethylene glycol and a functional monomer as raw material monomers, and performing esterification reaction under the action of a transesterification catalyst and heating to form the high-molecular polymer; then preparing the high-molecular polymer into polyester fibers by adopting an organic solvent wet-method gel spinning process; and finally, modifying the surface of the polyester fiber, adding the polyester fiber into the preheated modification solution, stirring at constant temperature, cooling to normal temperature, carrying out suction filtration, and drying to obtain the fiber material for preventing the proppant from reflowing. The proppant backflow prevention fiber prepared by the method can effectively solve the problem of proppant backflow after tight reservoir volume fracturing, and the influence of sand production on normal production of oil and gas wells is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of petrochemical industry, and in particular to a highly polar modified polyester fiber for preventing proppant reflux and a preparation method thereof. Background Art

[0002] The main development method for tight oil and gas reservoirs is horizontal well + volume fracturing, which forms a complex fracture network structure in the reservoir, increases the reservoir transformation volume, and achieves long-term stable production of oil and gas wells. However, as the scale of transformation increases, the width of the proppant fracture near the well increases, the structural strength of the proppant sand pile decreases, and the stability is poor. During the drainage and production process, affected by factors such as fluid flow rate and viscosity, the proppant particles lose stability and migrate and accumulate in the wellbore, resulting in sand production in the oil well.

[0003] The proppant backflow not only destroys the original sand-laying profile, reduces the proppant's supporting effect on the fracturing cracks, and has a certain impact on the long-term flow conductivity of the cracks and the normal production of the oil wells. At the same time, the proppant that flows back into the wellbore will be deposited at the bottom of the well and will bury the production layer, which also increases the difficulty of wellbore treatment and oil mud sand well field treatment. If the fracturing fluid is backflowed or the oil and gas production rate is high, it will also flow back to the ground, puncture the oil nozzle, erode the ground pipeline, and cause certain safety hazards.

[0004] The main technical measures currently taken to prevent proppant reflux are: ① Fracture forced closure technology, which uses a controlled release method to force fracture closure and reduce proppant spitting. Due to differences in geological conditions, construction conditions, and drainage conditions of different wells, the implementation is relatively complicated; ② The application of resin-coated proppants, through the mutual bonding between proppants, forms a proppant network barrier, but this technology easily leads to a decrease in fracture conductivity and a decrease in fracturing effect; ③ Fiber filling technology, using the effect of fibers and particles to form a spatial network structure, thereby achieving the purpose of inhibiting proppant spitting. The use of fiber anti-proppant reflux process can effectively improve the proppant sedimentation profile and achieve the purpose of preventing proppant reflux. In recent years, China has explored the application of fiber anti-proppant reflux technology in tight oil and gas horizontal wells. However, conventional fibers lack active functional groups on the surface, have poor dispersibility in fracturing fluids, poor compatibility with proppants, cannot form a stable structure with proppants, and are very easy to escape. Moreover, due to the large difference in density between the fiber and the proppant, in the low-viscosity slick water fracturing fluid system used in the main body of tight reservoir transformation, the fiber and the proppant are prone to form gravity differentiation along the longitudinal profile of the fracture, and the actual application effect is not ideal.

[0005] The process of sand prevention for oil and gas wells involves chemical sand prevention and physical sand prevention. Among them: Patent document CN106833585A discloses "a water-based resin sand prevention agent and its preparation method", CN111635745A discloses "the application of an aqueous solution diluent composition in oil and gas well sand prevention", CN103266877A discloses "a proppant reflux control system and control method based on magnetic proppant", CN104695931A discloses "a fracturing method for preventing proppant reflux in low permeability horizontal wells", CN109853083A discloses "a water-soluble degradable fiber and its preparation method", CN115012901A discloses "a proppant efficient laying multi-stage fiber sand prevention experimental method", the above disclosed prior art involves chemical agent composite coating, magnetic proppant, degradable fiber, experimental method, etc., which are obviously different from the content of the present invention and this patent.

[0006] Patent document CN104946229B discloses "composite synergist for fiber fracturing fluid and its preparation method and use method", which prepares a composite synergist and improves the dispersion performance of the fiber by adding it in fracturing. This patent uses the addition of auxiliary synergist to the system to improve the dispersion performance of the fiber, and does not perform any modification on the fiber itself.

[0007] Patent document CN107090715B discloses "a modified fiber for fracturing, a mixed injection device and a mixed injection method for the modified fiber". A modified fiber for fracturing is obtained by modifying a base fiber. The fiber is treated with a phosphoric acid type monoalkoxy titanate coupling agent, butylated hydroxytoluene, a hydrophilic oil agent, and n-octanol to improve the fiber's dispersibility and sand suspension capacity. This patent improves the fiber's dispersibility by grafting and modifying the base fiber surface, but it cannot solve the problem of large density difference between the fiber and the liquid system, poor compatibility with the sticky water system, and easy shearing and escaping.

[0008] Patent document CN109403038B discloses "a cationic polymer surface grafted vinylon fiber and its preparation method", which uses epichlorohydrin-dimethylamine cationic polymer to graft and modify the fiber to improve the fiber dispersibility. Similarly, this patent improves the fiber dispersibility by grafting vinylon fiber on the surface of cationic polymer, but cannot solve the problem of large density difference between fiber and liquid system, poor adaptability of sticky water system, and easy escape by shear.

[0009] Patent document CN111961460A discloses a "high-efficiency energy-saving, bridge channel fully coupled fiber proppant system", which uses a composite modifier of Tween 40 and sodium α-olefin sulfonate (12 carbons) to treat the fiber to improve the dispersibility of the fiber in clean water or low-viscosity fracturing fluid and the affinity of the coated proppant. This patent improves the affinity with the coated proppant through surfactant grafting modification, but ordinary quartz sand or ceramsite is different from the coated proppant, and has few coupling sites. It is impossible to improve its coupling ability with the proppant by relying solely on surfactant grafting.

[0010] Therefore, in view of the problems that conventional fibers have poor dispersibility in fracturing fluids, poor compatibility with proppants, and cannot form a stable structure with proppants, it is urgent to develop a new type of fiber material modification research to enhance the coupling effect between fibers and proppants and improve the anti-proppant backflow effect of the fiber system in reservoir transformation applications. Summary of the invention

[0011] The present invention aims to provide a strongly polar modified polyester fiber for preventing proppant backflow and a preparation method thereof. Through two key improvement processes, the synthesis of strongly polar functional monomers is introduced, and the surface is modified by grafting strongly polar long-chain groups, which significantly improves the hydrophilicity of the fiber and balances the density of the material, so that the fiber can be evenly and stably dispersed in both clean water and slick water fracturing fluids, and at the same time enhances the coupling effect between the fiber, the drag reducing agent and the proppant particles, synthesizes a strongly polar modified polyester fiber system for preventing proppant backflow with good dispersibility, fully solves the problem of insufficient adaptability of conventional fibers in slick water sand-carrying fluids, improves the stability of the composite structure of the fiber and the proppant, enhances the anti-proppant backflow effect of the fiber material, and effectively solves the problem of proppant backflow after volume fracturing of dense reservoirs; at the same time, the preparation method of the modified polyester fiber has the advantages of simple synthesis steps, convenient operation and low cost.

[0012] To achieve the above object, the present invention provides the following technical solutions:

[0013] The present invention provides a method for preparing a highly polar modified polyester fiber for preventing proppant backflow, the method comprising the following steps:

[0014] Step S1, polymer polymerization: adding the reaction raw materials into a U-shaped esterification kettle, and carrying out an esterification reaction under the action of an ester exchange catalyst, stirring and heating at a temperature of 240 to 290° C., and forming a polymer by reverse suspension polymerization; the reaction raw materials include: terephthalic acid, ethylene glycol and a strong polar functional monomer;

[0015] Step S2, spinning: adding the high molecular polymer of step S1 into white oil, swelling and dissolving the high molecular polymer in a twin screw, then extruding it from a spinneret, and quenching it into a gel fiber in a coagulation bath; using dichloromethane as an extractant to perform multi-stage extraction, extracting and drying to obtain dry fiber, and then super-multiple heat stretching;

[0016] Step S3, surface modification: adding a fiber surface modifier into a reactor and heating it to a set temperature, adding the functional polyester fiber of step S2 into the reactor under stirring conditions, reacting fully at a constant temperature, and filtering and drying in sequence after the reaction to obtain a strongly polar modified polyester fiber for preventing proppant reflux.

[0017] Preferably, in step S1, the dosage ratio of the reaction raw materials includes:

[0018] The mass of terephthalic acid accounts for 35-45% of the total mass of the raw materials, the mass of ethylene glycol accounts for 20-40% of the total mass of the raw materials, the mass of the strong polar functional monomer accounts for 10-20% of the total mass of the raw materials, and the ester exchange catalyst accounts for 1-5% of the total mass of the raw materials.

[0019] Preferably, in step S1, the highly polar functional monomer is one of acryloyl glycinamide, N,N-dimethylacrylamide or methacryloyloxyethyl trimethyl ammonium chloride; and the transesterification catalyst is manganese acetate.

[0020] Preferably, in step S1, the esterification reaction conditions include: temperature of 240-290° C.; time of 2-4 h.

[0021] Preferably, in step S2, the functional polyester fiber formed by the spinning process has a size of 7 to 20 μm in diameter and a length of 3 to 12 mm.

[0022] Preferably, in step S3, the heating temperature is 40-60° C.; the constant temperature is 40-60° C., and the constant temperature reaction time is 60-80 min.

[0023] Preferably, in step S3, the fiber surface modifier is prepared by mixing various raw material components, heating, stirring and fully mixing.

[0024] Preferably, the fiber surface modifier comprises the following components by weight:

[0025] Vinyl triethoxysilane: 18% to 36%; long-chain strong polar surface modifier is one or more of fatty acid glyceride derivatives, fatty acid glyceride derivatives, and ricinoleic acid derivatives: 6% to 20%; dibutyl hydroxytoluene: 2% to 8%; polyacrylate emulsion: 5% to 14%; polyethylene glycol: 3% to 13%; isopropyl alcohol: 10% to 45%.

[0026] Preferably, in step S3, the drying temperature is 60-80° C., and the drying time is 16-24 hours.

[0027] The present invention also provides a strongly polar modified polyester fiber for preventing proppant backflow, which is prepared by the above method.

[0028] Compared with the prior art, the present invention is beneficial in that:

[0029] (1) The present invention adopts a functional monomer with a strong polar group and introduces a specially designed strong polar functional monomer into the molecular chain by a controlled free radical polymerization method during the polycondensation process of polyester fibers, so that the molecular weight of the fiber matrix polymer is uniform and the molecular structure is regular, making the polymer performance more uniform and stable, while balancing the density of the material. The introduction of the strong polar functional monomer greatly improves the hydrophilicity of the fiber polymer, so that the strong polar fiber after polymerization modification has a high density compatibility with various liquid systems and greatly improves its dispersibility.

[0030] (2) The present invention further performs surface grafting modification on the fibers made by polymer melt spinning, and modifies the surface of the fiber material with specific strong polar long-chain groups to further enhance the hydrophilicity of the fiber, thereby fundamentally solving the problem that the fiber is easy to escape after shearing due to the large density difference between the fiber and the liquid, and has poor compatibility with the proppant and low-viscosity liquid system.

[0031] (3) The present invention improves the hydrophilicity and material density of the fiber by introducing the above two steps of strong polar groups (introducing polar functional monomer synthesis, plus surface grafting strong polar long chain group modification), enhances the coupling effect between the fiber, drag reducing agent and proppant particles, and improves the stability of the fiber and proppant composite structure. It effectively solves the problem of insufficient adaptability of conventional fibers in slick water sand-carrying fluids and improves the anti-proppant backflow effect of fiber materials.

[0032] (4) The preparation method of the fiber material has simple synthesis steps, convenient operation and low cost. This method can effectively support the efficient development of tight oil and gas reservoirs and solve the problem of proppant reflux after compression.

[0033] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 This is a comparison chart of the dispersion performance in clean water of the modified polyester fiber prepared in Example 1 of the present invention and the ordinary polyester fiber prepared in Comparative Examples 1-2;

[0036] Figure 2 This is a comparison chart of the static sand suspension performance of the modified polyester fiber prepared in Example 2 of the present invention and the ordinary polyester fiber prepared in Comparative Example 1;

[0037] Figure 3 Schematic diagram of the sand bank laying of 40-70 mesh quartz sand in slippery water without fiber addition;

[0038] Figure 4 It is a schematic diagram of laying a sand bank of quartz sand of 40-70 mesh in slippery water containing highly polar modified polyester fiber for preventing proppant backflow prepared in Example 3 of the present invention;

[0039] Figure 5 This is a comparison chart of the effects of the highly polar modified polyester fiber for preventing proppant backflow in Example 4 of the present invention and the ordinary polyester fiber in Comparative Example 1 on the critical sand flow rate of the 40-70 mesh quartz sand proppant filling layer;

[0040] Figure 6 is a scanning electron microscope photograph of the sand mixing liquid without the strongly polar modified polyester fiber in Example 5;

[0041] Figure 7 This is a scanning electron microscope photograph of the sand mixing liquid containing the strongly polar modified polyester fiber in Example 5. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] The design concept of the present invention includes: in the process of polyester fiber polycondensation, a controlled free radical polymerization method is used to controllably introduce a specially designed strong polar functional monomer into the molecular chain, so that the molecular weight of the fiber matrix polymer is uniform, the molecular structure is regular, and the polymer performance is more uniform and stable, while balancing the density of the material. The introduction of the strong polar monomer greatly improves the hydrophilicity of the fiber polymer, so that the strong polar fiber after polymerization modification has a high density compatibility with various liquid systems, and the dispersibility is greatly improved. The fiber made by polymer melt spinning is further subjected to surface grafting modification, and specific strong polar long chain groups are modified on the surface of the functional material to further enhance the hydrophilicity of the fiber, fundamentally solving the problem that the fiber and the liquid have a large density difference and are easy to escape after shearing, and the compatibility with the proppant and low-viscosity liquid system is poor. The introduction of two-step strong polar groups effectively improves the coupling effect between the fiber and the proppant and the liquid system, improves the stability of the composite structure of the fiber and the proppant, and has the advantages of simple steps, convenient operation, and low cost in the preparation process.

[0044] To this end, the present invention discloses a method for preparing a highly polar modified polyester fiber for preventing proppant reflux, the method comprising the following steps:

[0045] Step S1, polymer polymerization: terephthalic acid, ethylene glycol, and functional monomers are selected as reaction raw material monomers, and an esterification reaction is carried out for 2 to 4 hours under the action of an ester exchange catalyst, with stirring and heating at a temperature of 240 to 290° C., and a polymer is formed by reverse suspension polymerization; the functional monomer is selected from one of strongly polar acrylyl glycinamide, N,N-dimethyl acrylamide, or methacryloyloxyethyl trimethyl ammonium chloride;

[0046] Step S2, spinning: using an organic solvent wet gel spinning process, adding a high molecular polymer to white oil, swelling and dissolving the polymer in a twin-screw, then extruding it from a spinneret, and quenching it into gel fiber in a coagulation bath; using dichloromethane as an extractant for multi-stage extraction, obtaining dry fiber after extraction and drying, and then obtaining polyester fiber with a diameter of 7-20um and a length of 3-12mm through super-multiple heat stretching.

[0047] Step S3, surface modification: adding a fiber surface modifier into a three-necked flask, heating the flask and rapidly stirring the solution to raise the temperature of the solution to 40-60° C., adding the functional polyester fiber of step S2 into the three-necked flask, and stirring sufficiently for 60-80 minutes at a constant temperature of 40-60° C.;

[0048] Step S4, suction filtration: moving the surface-modified functional polyester fiber onto filter paper, cooling it to room temperature, and then suction filtration;

[0049] Step S5, drying: the filtered fiber is placed in an oven at 60-80° C. for drying for 16-24 hours, thereby obtaining a highly polar modified polyester fiber for preventing proppant reflux.

[0050] In step S1 of the present invention, the addition amount of terephthalic acid, ethylene glycol, strongly polar functional monomer and transesterification catalyst is controlled, a slurry suspension is prepared by a slurry preparation tank, and a high molecular polymer is formed by reverse suspension polymerization and copolymerization. The dosage of the reaction raw materials is as follows:

[0051] The mass of terephthalic acid accounts for 35% to 45% of the total mass of the raw materials, the mass of ethylene glycol accounts for 20% to 40% of the total mass of the raw materials, the mass of the strong polar functional monomer accounts for 10% to 20% of the total mass of the raw materials, and the ester exchange catalyst accounts for 1% to 5% of the total mass of the raw materials.

[0052] In step S1 of the present invention, the transesterification catalyst is preferably manganese acetate. The strong polar functional monomer is one of acryloyl glycinamide, N,N-dimethyl acrylamide or methacryloyloxyethyl trimethyl ammonium chloride.

[0053] In step S2 of the present invention, the functional polyester fiber formed by the spinning process is in the form of white filaments and can form fiber materials with different diameters of 7 to 20 μm. The fiber length can be distributed in the range of 3 to 12 mm, and has a large aspect ratio.

[0054] In step S3 of the present invention, a strongly polar long-chain group is grafted onto the fiber surface by means of a surface modifier, wherein the fiber surface modifier is composed of the following raw materials in parts by weight:

[0055] Vinyltriethoxysilane: 18% to 36%;

[0056] Long-chain strong polar surface modifier: including one or more of fatty acid glyceride derivatives, fatty acid glyceride derivatives, and ricinoleic acid derivatives: 6% to 20%;

[0057] Butylated hydroxytoluene: 2% to 8%; polyacrylate emulsion: 5% to 14%; polyethylene glycol: 3% to 13%; isopropyl alcohol: 10% to 45%.

[0058] Comparative Example 1:

[0059] This comparative example 1 provides an unmodified conventional polyester fiber material, which is prepared from the following raw materials in the following mass ratio:

[0060] The mass of terephthalic acid accounts for 55% of the total mass of the raw materials, the mass of ethylene glycol accounts for 35% of the total mass of the raw materials, and the ester exchange catalyst accounts for 10% of the total mass of the raw materials.

[0061] This comparative example 1 also provides a method for preparing an unmodified conventional polyester fiber, which comprises the following steps:

[0062] Step S1, polymer polymerization: adding the reaction raw materials into a U-shaped esterification kettle for reaction, the terephthalic acid slurry undergoes esterification reaction under stirring and heating conditions of a heat medium, and the reaction conditions are changed by controlling the material amount of ethylene glycol to increase the product esterification rate;

[0063] Step S2, spinning: using an organic solvent wet gel spinning process, the polyester fiber product is added to white oil, the polymer is swollen and dissolved in a twin screw, and then extruded from a spinneret, and quenched into a gel fiber in a coagulation bath. Multi-stage extraction is performed using dichloromethane as an extractant, and dry fibers are obtained after extraction and drying, and then a functional polyester fiber material is obtained by super-multiple heat stretching.

[0064] Comparative Example 2:

[0065] This comparative example 2 provides a polyester fiber material modified by introducing a strong polar monomer into the polymerization, which is prepared from the following raw materials in the following mass ratio:

[0066] The mass of terephthalic acid accounts for 55% of the total mass of the raw materials, the mass of ethylene glycol accounts for 28% of the total mass of the raw materials, the strong polar monomer acrylylglycinamide accounts for 12% of the total mass of the raw materials, and the ester exchange catalyst accounts for 5% of the total mass of the raw materials.

[0067] This comparative example 2 also provides a method for preparing a modified polyester fiber, which comprises the following steps:

[0068] Step S1, polymer polymerization: Add the reaction raw materials into the U-shaped esterification kettle for reaction, and the terephthalic acid slurry is subjected to esterification reaction under the conditions of stirring and heating with a heat medium. The esterification rate of the product is increased by changing the reaction conditions by controlling the amount of ethylene glycol. The controlled free radical polymerization method is used to controllably introduce the specially designed strong polar functional monomer into the molecular chain, making the polymer molecular structure more regular;

[0069] Step S2, spinning: using an organic solvent wet gel spinning process, the functional polyester fiber product is added to white oil, the polymer is swollen and dissolved in a twin screw, and then extruded from a spinneret, and quenched into a gel fiber in a coagulation bath. Multi-stage extraction is performed using dichloromethane as an extractant, and dry fibers are obtained after extraction and drying, and then the functional polyester fiber material is obtained by super-heat stretching; the functional polyester fiber formed by the spinning process is white filamentous, and can form fiber materials with different diameters of 7 to 20 μm, and the fiber length can be distributed in the range of 3 to 12 mm, with a large aspect ratio.

[0070] Embodiment 1:

[0071] This embodiment 1 provides a highly polar modified polyester fiber material for high-efficiency anti-proppant backflow for fracturing after two-step highly polar modification, which is prepared from the following raw materials in the following mass ratio:

[0072] The mass of terephthalic acid accounts for 45% of the total mass of the raw materials, the mass of ethylene glycol accounts for 30% of the total mass of the raw materials, the mass of acrylylglycinamide accounts for 20% of the total mass of the raw materials, and the ester exchange catalyst accounts for 5% of the total mass of the raw materials.

[0073] After the functional polyester fiber is formed by a spinning process, a strong polar long-chain group is grafted on the fiber surface by means of a surface modifier, wherein the fiber surface modifier is composed of the following raw materials in parts by weight:

[0074] Vinyl triethoxysilane: 30%; Palmitic acid monoglyceride: 11%;

[0075] Butylated hydroxytoluene: 2%; Polyacrylate emulsion: 6%;

[0076] Polyethylene glycol: 6%; Isopropyl alcohol: 45%.

[0077] This embodiment 1 also provides a method for preparing a highly polar modified polyester fiber for high-efficiency anti-proppant backflow, which comprises the following steps:

[0078] Step S1, polymer polymerization: the raw material mixture is sent to a U-shaped esterification kettle to continue the reaction, and the mixture is stirred and heated to 260°C for esterification reaction to generate a polymer of ethylene terephthalate, and the reaction residence time is 2 to 4 hours. When the degree of polymerization of the polymer reaches 4 to 5, the polymer is sent to a pre-polycondensation reactor, heated to 290°C, and the polymer continues to undergo polycondensation reaction under catalyst and vacuum conditions to obtain polyethylene terephthalate. In this process, the water and excess ethylene glycol generated by the reaction are sent to a separation tower for distillation separation. When the degree of polymerization of the polymer generated by the pre-polycondensation reactor reaches 15 to 35, it enters the final polycondensation reactor through a loop sealing pipeline, and a larger contact area is provided for the raw material through an agitator to promote the polycondensation reaction to continue to proceed forward to generate a polymer, and finally the degree of polymerization of the polymer generated in the final polycondensation stage reaches 100.

[0079] Step S2, using an organic solvent wet gel spinning process, the polyester melt and white oil prepared in the previous step are added to the swelling kettle, and the solution is configured to be 16% by mass, emulsified for 15 minutes, and then the swelling kettle is heated to 180°C and maintained for 1 hour. The polyethylene terephthalate polymer swells and dissolves in the white oil system, and then passes through a metering pump, a twin-screw extruder and a spinning manifold, extruded from a spinneret, and quenched in an alcohol solution coagulation bath, pre-stretched and shaped, and then dropped into a barrel to form a primary gel filament. The gel filament is subjected to multi-stage extraction using dichloromethane as an extractant, and dry fibers are obtained after extraction and drying, and then finally rolled into finished fibers after super-multiple heat stretching. The prepared fiber material has a diameter of 7-20um and a length of 3-12mm.

[0080] Step S3, surface modification: add the components of the modified solution into a three-necked flask, heat the flask and quickly stir the solution to raise the temperature to 50° C., add polyester fiber into the three-necked flask, stir thoroughly at a constant temperature of 50° C. for 3 h, and then cool.

[0081] Step S4, suction filtration: the surface-modified functional polyester fiber is moved onto filter paper, cooled to room temperature, and then suction filtered.

[0082] Step S5, drying: the filtered fiber is placed in an oven at 60° C. for drying for 18 hours, thereby obtaining a highly polar modified polyester fiber for preventing proppant reflux.

[0083] The dispersion performance in water of the highly polar modified polyester fiber for preventing proppant reflux prepared in Example 1 was compared with that of the polyester fiber prepared in Comparative Examples 1 and 2. Three polyester fiber materials with a mass concentration of 0.5% were weighed and added into 200 mL of clean water, and the mixture was rapidly stirred at 800 r / min by a magnetic stirrer to observe the dispersion time and dispersion conditions of the three fibers in the clean water.

[0084] Figure 1 : is a comparison chart of the dispersion performance in clear water of the modified polyester fiber prepared in Example 1 of the present invention and the ordinary polyester fiber prepared in Comparative Examples 1-2, as shown in FIG. Figure 1As shown, the dispersion time of the polyester fiber obtained in Comparative Example 1 in water is about 30s, and it can be evenly dispersed. However, due to the low fiber density, most of the fibers float to the upper part of the beaker 10 minutes after stopping stirring, and the dispersion stability is poor; the dispersion time of the polyester fiber obtained in Comparative Example 2 in water is about 15s, and it can be quickly and evenly dispersed, but the density of this modified fiber is higher than the density of water. Most of the fibers settle to the bottom of the beaker 10 minutes after stopping stirring, and the dispersion stability is also poor; while the strongly polar modified polyester fiber for anti-proppant reflux of the same concentration can be quickly dispersed in clean water by mechanical stirring, and the dispersion time in clean water is less than 15s. After stopping stirring for 10 minutes, the fibers can still be evenly distributed in the system, and no fiber agglomeration is observed, indicating that the developed strongly polar modified polyester fiber for anti-proppant reflux has excellent dispersion performance and good dispersion stability.

[0085] This is because the fiber has been through two key improvement processes, introducing strong polar groups and surface grafting modification, the fiber has stronger hydrophilicity, and the density of the material itself is close to the density of the solution, and the dispersion stability in the solution has been greatly improved. The two-step improvement process is indispensable, and the modified functional polyester fiber obtained by this method can better meet the requirements of fiber sand fracturing for rapid and uniform fiber dispersion.

[0086] Embodiment 2:

[0087] This embodiment 2 provides a highly polar modified polyester fiber material for high-efficiency anti-proppant backflow for fracturing, which is prepared from the following raw materials in the following mass ratio:

[0088] The mass of terephthalic acid accounts for 45% of the total mass of the raw materials, the mass of ethylene glycol accounts for 35% of the total mass of the raw materials, the mass of N,N-dimethylacrylamide accounts for 15% of the total mass of the raw materials, and the ester exchange catalyst accounts for 5% of the total mass of the raw materials.

[0089] After the functional polyester fiber is formed by a spinning process, a strong polar long-chain group is grafted on the fiber surface by means of a surface modifier, wherein the fiber surface modifier is composed of the following raw materials in parts by weight:

[0090] Vinyl triethoxysilane: 20%; Stearic acid monoglyceride: 15%;

[0091] Butylated hydroxytoluene: 5%; Polyhydroxyethyl acrylate emulsion: 7%;

[0092] Polyethylene glycol: 13%; Isopropyl alcohol: 40%.

[0093] The preparation method of the highly polar modified polyester fiber for high-efficiency anti-proppant backflow in this embodiment 2 is the same as that in embodiment 1.

[0094] The highly polar modified polyester fiber for high-efficiency anti-proppant reflux prepared in Example 2 and the ordinary polyester fiber were evaluated for static sand suspension performance. 0.5% of the high-efficiency anti-proppant reflux fiber and the unmodified ordinary polyester fiber were weighed and added to 100mL ultrapure water, and the fibers were stirred and dispersed for 2 minutes by a magnetic stirrer; after the fibers were evenly dispersed, 30% of the sand ratio of 70-140 mesh quartz sand proppant was added and stirred evenly, and then 0.1% of the mass fraction of salt-resistant variable viscosity and drag reducing agent was added and stirred for 5 minutes to make it evenly dispersed. After the solution was prepared, the mixed solution was poured into a 100mL measuring cylinder, and the sedimentation state of the proppant in the two solutions was compared. Figure 2 This is a comparison chart of the static suspended sand performance of the modified polyester fiber prepared in Example 2 of the present invention and the ordinary polyester fiber prepared in Comparative Example 1. The final sedimentation result of the system is shown in FIG. Figure 2 In the slippery water system with the addition of modified polyester fibers, the modified fibers can be fully compounded into the proppant sand body, so that the height of the sand body formed by the accumulation is significantly higher than that of the ordinary polyester fiber slippery water system.

[0095] As shown in Table 1, in the unmodified ordinary polyester fiber drag reducing agent solution, the proppant settling time was 388s, the proppant settling rate was 0.278cm / s, and the proppant stacking height was 6.4cm. In the same concentration of anti-proppant backflow fiber drag reducing agent solution, the proppant settling time was 852s, the proppant settling rate was 0.233cm / s, a year-on-year decrease of 119.6%; the stacking height was 10.6cm, a year-on-year increase of 65.6%. Compared with unmodified ordinary polyester fiber, the high-efficiency anti-proppant backflow fiber has better sand suspension performance, can greatly reduce the proppant settling rate in slick water fracturing fluid, and effectively increase the proppant stacking volume.

[0096] Table 1 Evaluation results of static suspended sand performance

[0097]

[0098] Embodiment 3:

[0099] This embodiment 3 provides a highly polar modified polyester fiber material for high-efficiency anti-proppant backflow for fracturing, which is prepared from the following raw materials in the following mass ratio:

[0100] The mass of terephthalic acid accounts for 45% of the total mass of the raw materials, the mass of ethylene glycol accounts for 32% of the total mass of the raw materials, the mass of methacryloyloxyethyltrimethylammonium chloride accounts for 18% of the total mass of the raw materials, and the ester exchange catalyst accounts for 5% of the total mass of the raw materials.

[0101] After the functional polyester fiber is formed by a spinning process, a strong polar long-chain group is grafted on the fiber surface by means of a surface modifier, wherein the fiber surface modifier is composed of the following raw materials in parts by weight:

[0102] The mass of vinyl triethoxysilane accounts for 35% of the total mass of raw materials; the mass of stearic acid monoglyceride accounts for 20% of the total mass of raw materials; the mass of butylated hydroxytoluene accounts for 4% of the total mass of raw materials; the mass of polyhydroxyethyl acrylate emulsion accounts for 5% of the total mass of raw materials; the mass of polyethylene glycol accounts for 6% of the total mass of raw materials; and the mass of isopropanol accounts for 30% of the total mass of raw materials.

[0103] The preparation method of the highly polar modified polyester fiber for high-efficiency anti-proppant backflow in this embodiment 3 is the same as that in embodiment 1.

[0104] The dynamic transport experiment of proppant in the flat plate crack in the fiber slippery water was carried out by using the flat plate crack visualization device to study the effect of adding the highly polar modified polyester fiber for high-efficiency anti-proppant backflow prepared in Example 3 on the proppant transport and sand bank laying morphology. The uniformly mixed sand mixture (mixture of fiber, drag reducer, proppant and clean water) was pumped into the 6mm crack at a displacement of 18L / min. When the proppant particles flowed through the observation area, the dynamic data during the experiment was obtained through the high-definition video acquisition system. Later, the transport and sedimentation state of the particles were observed through image analysis. The experimental results are shown in the figure. Figure 3 , 4 shown.

[0105] Figure 3 This is a schematic diagram of the laying of a sand bank with 40-70 mesh quartz sand in slippery water without adding fiber. Due to the weak sand-carrying capacity of slippery water alone, the proppant settles more at the front end of the fracture and then advances to the rear end. The final settlement distance is relatively short, and the upward growth process of the entire sand bank is relatively slow. Figure 4 The figure is a schematic diagram of the laying of a sand bank of 40-70 mesh quartz sand in slippery water containing the strongly polar modified polyester fiber for preventing proppant backflow prepared in Example 3 of the present invention. After the strongly polar modified polyester fiber for preventing proppant backflow with a mass concentration of 0.4% is added to the slippery water fracturing fluid system, the fibers are entangled to form clusters, which play the role of suspending and dragging the proppant, and can carry the proppant into the far end of the fracture to improve the supporting effect on the far end fracture. The 0.4% added fiber can increase the proppant migration distance by more than 50%, and also greatly improve the sand laying profile, so as to achieve uniform filling of the proppant in the fracture in the horizontal and vertical directions, and improve the volume fracturing transformation effect of the tight oil and gas reservoir.

[0106] Embodiment 4:

[0107] This embodiment 4 provides a highly polar modified polyester fiber material for high-efficiency anti-proppant backflow for fracturing, which is prepared from the following raw materials in the following mass ratio:

[0108] The mass of terephthalic acid accounts for 35% of the total mass of the raw materials, the mass of ethylene glycol accounts for 40% of the total mass of the raw materials, the mass of acrylylglycinamide accounts for 20% of the total mass of the raw materials, and the ester exchange catalyst accounts for 5% of the total mass of the raw materials.

[0109] After the functional polyester fiber is formed by a spinning process, a strong polar long-chain group is grafted on the fiber surface by means of a surface modifier, wherein the fiber surface modifier is composed of the following raw materials in parts by weight:

[0110] Vinyl triethoxysilane: 30%; Diglycerol palmitate: 15%;

[0111] Butylated hydroxytoluene: 8%; Polyhydroxyethyl acrylate emulsion: 10%;

[0112] Polyethylene glycol: 10%; Isopropyl alcohol: 27%.

[0113] The preparation method of the highly polar modified polyester fiber for high-efficiency anti-proppant backflow in Example 4 is the same as that in Example 1.

[0114] The highly efficient anti-proppant backflow strong polar modified polyester fiber prepared in Example 4 and ordinary polyester fiber were used to evaluate the anti-proppant backflow performance. The critical sand flow rate was measured by using a flow conductivity test system and fracture surface rock samples, 70-140 mesh quartz sand proppants were selected, and a salt-resistant variable viscosity and drag reducing agent solution with a mass concentration of 0.01% was used to simulate the gel breaking and backflow stage of the fracturing fluid. The critical sand flow rate of the artificial fracture after adding the highly efficient anti-proppant backflow strong polar modified polyester fiber and ordinary polyester fiber was compared, and the advantages of the developed highly efficient anti-proppant backflow strong polar modified polyester fiber in improving the stability of the proppant filling layer and preventing proppant backflow were evaluated. The experimental results are as follows: Figure 5 shown.

[0115] Figure 5 The following is a comparison chart of the effects of the highly polar modified polyester fiber for preventing proppant backflow in Example 4 of the present invention and the ordinary polyester fiber in Comparative Example 1 on the critical sand flow rate of the 40-70 mesh quartz sand proppant filling layer. Figure 5As shown in the figure, the addition of the two fiber materials has played a significant role in improving the critical sand flow rate of the proppant. Under the closure pressure of 2MPa, the critical sand flow rate of the ordinary polyester fiber with an addition of 0.5% is 117mL / min, and the critical sand flow rate of the strong polar modified polyester fiber for anti-proppant reflux under the same conditions is 246mL / min; under the closure pressure of 8MPa, the critical sand flow rate of the ordinary polyester fiber with an addition of 0.5% is 341mL / min, and the critical sand flow rate of the strong polar modified polyester fiber for anti-proppant reflux under the same conditions is 723mL / min. Within the experimental test range, under various pressure conditions, the critical sand flow rate of the proppant filling layer can be increased by more than 1 times by adding the strong polar modified polyester fiber for anti-proppant reflux compared with the ordinary polyester fiber. This shows that the strong polar modified polyester fiber for anti-proppant reflux has more outstanding advantages in anti-proppant reflux than ordinary polyester fiber, can better improve the stability of the proppant filling layer, and effectively solve the sand problem in the production process after fracturing wells.

[0116] Embodiment 5:

[0117] This embodiment 5 provides a highly polar modified polyester fiber material for high-efficiency anti-proppant backflow for fracturing, which is prepared from the following raw materials in the following mass ratio:

[0118] The mass of terephthalic acid accounts for 44% of the total mass of the raw materials, the mass of ethylene glycol accounts for 35% of the total mass of the raw materials, the mass of N,N-dimethylacrylamide accounts for 16% of the total mass of the raw materials, and the ester exchange catalyst accounts for 5% of the total mass of the raw materials.

[0119] After the functional polyester fiber is formed by a spinning process, a strong polar long-chain group is grafted on the fiber surface by means of a surface modifier, wherein the fiber surface modifier is composed of the following raw materials in parts by weight:

[0120] The mass of vinyltriethoxysilane accounts for 30% of the total mass of raw materials; the mass of palmitic acid monoglyceride accounts for 15% of the total mass of raw materials; the mass of butylated hydroxytoluene accounts for 5% of the total mass of raw materials; the mass of polyhydroxyethyl acrylate emulsion accounts for 13% of the total mass of raw materials; the mass of polyethylene glycol accounts for 10% of the total mass of raw materials; and the mass of isopropanol accounts for 27% of the total mass of raw materials.

[0121] The preparation method of the highly polar modified polyester fiber for high-efficiency anti-proppant backflow in Example 5 is the same as that in Example 1.

[0122] The high-efficiency anti-proppant backflow fiber obtained in Example 5 was added to 100 mL of ultrapure water at a mass fraction of 0.5%. After the fiber was evenly dispersed, 100 / 200 mesh quartz sand with a sand ratio of 20% and a salt-resistant variable viscosity drag reducer with a mass fraction of 0.1% were added to prepare a low-viscosity fiber drag reducer mixed sand liquid, and a fiber-free drag reducer mixed sand liquid was prepared in the same way. A small amount of each of the two groups of liquids was taken to make a scanning sample, and the microscopic morphology of the fiber, drag reducer and quartz sand mixed system was observed and analyzed under an environmental scanning electron microscope ESEM. The experimental results are shown in FIG. Figure 6 , 7 shown.

[0123] like Figure 6 As shown in the figure, in the low-viscosity drag reducer mixed sand solution, the drag reducer polymer molecular chain swells and stretches to form a mesh structure with meshes, which wraps and covers the surface of the quartz sand particles and has a certain fixing effect on the proppant. However, due to the weak network structure formed by the low drag reducer concentration, its effect is also weak. After adding strong polar fibers to the system, such as Figure 7 As shown, the fibers are dispersed into filaments and interspersed in the proppant particles. The drag reducing agent molecules not only wrap the proppant but also connect different filamentary fibers. The two materials bond to form a three-dimensional network structure with higher strength, which can resist external interference caused by the fluid and fix the proppant network in its original position, thereby maintaining the stability of the sand body structure and preventing the backflow of the proppant.

[0124] Embodiment 6:

[0125] This embodiment 6 provides a highly polar modified polyester fiber material for high-efficiency anti-proppant backflow for fracturing, which is prepared from the following raw materials in the following mass ratio:

[0126] The mass of terephthalic acid accounts for 42% of the total mass of the raw materials, the mass of ethylene glycol accounts for 35% of the total mass of the raw materials, the mass of methacryloyloxyethyltrimethylammonium chloride accounts for 19% of the total mass of the raw materials, and the mass of catalyst manganese acetate accounts for 4% of the total mass of the raw materials.

[0127] After the functional polyester fiber is formed by a spinning process, a strong polar long-chain group is grafted on the fiber surface by means of a surface modifier, wherein the fiber surface modifier is composed of the following raw materials in parts by weight:

[0128] The mass of vinyltriethoxysilane accounts for 30% of the total mass of raw materials; the mass of stearic acid monoglyceride accounts for 10% of the total mass of raw materials; the mass of butylated hydroxytoluene accounts for 8% of the total mass of raw materials; the mass of polyhydroxyethyl acrylate emulsion accounts for 14% of the total mass of raw materials; the mass of polyethylene glycol accounts for 13% of the total mass of raw materials; and the mass of isopropanol accounts for 25% of the total mass of raw materials.

[0129] The preparation method of the highly polar modified polyester fiber for high-efficiency anti-proppant backflow in Example 6 is the same as that in Example 1.

[0130] Embodiment 7:

[0131] This embodiment 7 provides a highly polar modified polyester fiber material for high-efficiency anti-proppant backflow for fracturing, which is prepared from the following raw materials in the following mass ratio:

[0132] The mass of terephthalic acid accounts for 40% of the total mass of the raw materials, the mass of ethylene glycol accounts for 35% of the total mass of the raw materials, the mass of acrylylglycinamide accounts for 20% of the total mass of the raw materials, and the mass of catalyst manganese acetate accounts for 5% of the total mass of the raw materials.

[0133] After the functional polyester fiber is formed by a spinning process, a strong polar long-chain group is grafted on the fiber surface by means of a surface modifier, wherein the fiber surface modifier is composed of the following raw materials in parts by weight:

[0134] The mass of vinyl triethoxysilane accounts for 20% of the total mass of the raw materials; the mass of diglycerol palmitate accounts for 20% of the total mass of the raw materials; the mass of dibutyl hydroxytoluene accounts for 5% of the total mass of the raw materials; the mass of polyhydroxyethyl acrylate emulsion accounts for 14% of the total mass of the raw materials; the mass of polyethylene glycol accounts for 6% of the total mass of the raw materials; and the mass of isopropanol accounts for 35% of the total mass of the raw materials.

[0135] The preparation method of the highly polar modified polyester fiber for high-efficiency anti-proppant backflow in this embodiment 7 is the same as that in embodiment 1.

[0136] Embodiment 8:

[0137] This Example 8 provides a highly polar modified polyester fiber material for high-efficiency anti-proppant backflow for fracturing, which is prepared from the following raw materials in the following mass ratio:

[0138] The mass of terephthalic acid accounts for 37% of the total mass of the raw materials, the mass of ethylene glycol accounts for 40% of the total mass of the raw materials, the mass of N,N-dimethylacrylamide accounts for 18% of the total mass of the raw materials, and the mass of catalyst manganese acetate accounts for 5% of the total mass of the raw materials.

[0139] After the functional polyester fiber is formed by a spinning process, a strong polar long-chain group is grafted on the fiber surface by means of a surface modifier, wherein the fiber surface modifier is composed of the following raw materials in parts by weight:

[0140] The mass of vinyltriethoxysilane accounts for 36% of the total mass of raw materials; the mass of palmitic acid monoglyceride accounts for 8% of the total mass of raw materials; the mass of butylated hydroxytoluene accounts for 6% of the total mass of raw materials; the mass of polyhydroxyethyl acrylate emulsion accounts for 10% of the total mass of raw materials; the mass of polyethylene glycol accounts for 5% of the total mass of raw materials; and the mass of isopropanol accounts for 35% of the total mass of raw materials.

[0141] The preparation method of the highly polar modified polyester fiber for high-efficiency anti-proppant backflow in Example 8 is the same as that in Example 1.

[0142] Embodiment 9:

[0143] This Example 9 provides a highly polar modified polyester fiber material for high-efficiency anti-proppant backflow for fracturing, which is prepared from the following raw materials in the following mass ratio:

[0144] The mass of terephthalic acid accounts for 40% of the total mass of the raw materials, the mass of ethylene glycol accounts for 40% of the total mass of the raw materials, the mass of methacryloyloxyethyltrimethylammonium chloride accounts for 15% of the total mass of the raw materials, and the ester exchange catalyst accounts for 5% of the total mass of the raw materials.

[0145] After the functional polyester fiber is formed by a spinning process, a strong polar long-chain group is grafted on the fiber surface by means of a surface modifier, wherein the fiber surface modifier is composed of the following raw materials in parts by weight:

[0146] Vinyl triethoxysilane: 36%; Diglyceryl stearate: 8%;

[0147] Butylated hydroxytoluene: 6%; Polyhydroxyethyl acrylate emulsion: 10%;

[0148] Polyethylene glycol: 5%; Isopropyl alcohol: 35%.

[0149] The preparation method of the highly polar modified polyester fiber for high-efficiency anti-proppant backflow in Example 9 is the same as that in Example 1.

[0150] Embodiment 10:

[0151] This embodiment 10 provides a highly polar modified polyester fiber material for high-efficiency anti-proppant backflow for fracturing, which is prepared from the following raw materials in the following mass ratio:

[0152] The mass of terephthalic acid accounts for 45% of the total mass of the raw materials, the mass of ethylene glycol accounts for 30% of the total mass of the raw materials, the mass of acrylylglycinamide accounts for 20% of the total mass of the raw materials, and the ester exchange catalyst accounts for 5% of the total mass of the raw materials.

[0153] After the functional polyester fiber is formed by a spinning process, a strong polar long-chain group is grafted on the fiber surface by means of a surface modifier, wherein the fiber surface modifier is composed of the following raw materials in parts by weight:

[0154] Vinyl triethoxysilane: 36%; Stearic acid monoglyceride: 9%;

[0155] Butylated hydroxytoluene: 5%; Polyhydroxyethyl acrylate emulsion: 10%;

[0156] Polyethylene glycol: 5%; Isopropyl alcohol: 35%.

[0157] The preparation method of the highly polar modified polyester fiber for high-efficiency anti-proppant backflow in this embodiment 10 is the same as that in embodiment 1.

[0158] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a highly polar modified polyester fiber for preventing proppant backflow, characterized in that: The method comprises the following steps: Step S1, polymer polymerization: adding the reaction raw materials into a U-shaped esterification kettle, carrying out esterification reaction under stirring and heating conditions under the action of an ester exchange catalyst, and forming a high molecular polymer through reverse suspension polymerization and copolymerization; the reaction raw materials include: terephthalic acid, ethylene glycol and a strong polar functional monomer; Step S2, spinning: adding the high molecular polymer of step S1 into white oil, swelling and dissolving the high molecular polymer in a twin screw, then extruding it from a spinneret, and quenching it into a gel fiber in a coagulation bath; using dichloromethane as an extractant to perform multi-stage extraction, extracting and drying to obtain dry fiber, and then super-multiple heat stretching; Step S3, surface modification: adding a fiber surface modifier into a reactor and heating it to a set temperature, adding the functional polyester fiber of step S2 into the reactor under stirring conditions, reacting fully at a constant temperature, and filtering and drying in sequence after the reaction to obtain a strongly polar modified polyester fiber for preventing proppant reflux.

2. The method for preparing a highly polar modified polyester fiber for preventing proppant backflow according to claim 1, characterized in that: In step S1, the dosage ratio of the reaction raw materials includes: The mass of terephthalic acid accounts for 35-45% of the total mass of the raw materials, the mass of ethylene glycol accounts for 20-40% of the total mass of the raw materials, the mass of the strong polar functional monomer accounts for 10-20% of the total mass of the raw materials, and the ester exchange catalyst accounts for 1-5% of the total mass of the raw materials.

3. The method for preparing a highly polar modified polyester fiber for preventing proppant backflow according to claim 1 or 2, characterized in that: In step S1, the highly polar functional monomer is one of acryloyl glycinamide, N,N-dimethylacrylamide or methacryloyloxyethyl trimethyl ammonium chloride; and the transesterification catalyst is manganese acetate.

4. The method for preparing a highly polar modified polyester fiber for preventing proppant backflow according to claim 2, characterized in that: In step S1, the esterification reaction conditions include: The temperature is 240-290°C; the time is 2-4h.

5. The method for preparing a highly polar modified polyester fiber for preventing proppant backflow according to claim 1, characterized in that: In step S2, the functional polyester fiber formed by the spinning process has a size of 7 to 20 μm in diameter and a length of 3 to 12 mm.

6. The method for preparing a highly polar modified polyester fiber for preventing proppant backflow according to claim 1, characterized in that: In step S3, the heating temperature is 40-60°C; the constant temperature is 40-60°C, and the constant temperature reaction time is 60-80 minutes.

7. The method for preparing a highly polar modified polyester fiber for preventing proppant backflow according to claim 1, characterized in that: In step S3, the fiber surface modifier is prepared by mixing various raw material components, heating, stirring and fully mixing.

8. The method for preparing a highly polar modified polyester fiber for preventing proppant backflow according to claim 7, characterized in that: The fiber surface modifier comprises the following components by weight: Vinyl triethoxysilane: 18% to 36%; long-chain strong polar surface modifier is one or more of fatty acid glyceride derivatives, fatty acid glyceride derivatives, and ricinoleic acid derivatives: 6% to 20%; dibutyl hydroxytoluene: 2% to 8%; polyacrylate emulsion: 5% to 14%; polyethylene glycol: 3% to 13%; isopropyl alcohol: 10% to 45%.

9. The method for preparing a highly polar modified polyester fiber for preventing proppant backflow according to claim 1, characterized in that: In step S3, the drying temperature is 60-80°C, and the drying time is 16-24 hours.

10. A highly polar modified polyester fiber for preventing proppant backflow, characterized in that: The method is prepared by the method according to any one of claims 1 to 9.

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