A fiber fracturing fluid system and its preparation process

Abstract

This invention relates to the field of fracturing fluid systems, specifically to a fiber-based fracturing fluid system and its preparation process. The acetylated modified cellulose in this invention introduces active groups on the cellulose surface, improving its interfacial compatibility with polylactic acid (PLA). After acetylation modification, the polarity of the cellulose molecular chain decreases, its hydrophobicity increases, and its compatibility with PLA is further optimized, forming a uniform composite structure during spinning. This composite fiber serves as a supporting framework in fracturing operations, enhancing the viscoelasticity and proppant carrying capacity of the fracturing fluid through the fiber network. Furthermore, it can achieve controlled degradation after fracturing due to the biodegradability of PLA, avoiding reservoir damage caused by traditional fiber residues and achieving a dynamic balance between support and degradation. The ceramic proppant is uniformly dispersed in the fracturing fluid, achieving uniform settling and fracture filling through the dual encapsulation effect of the fiber network and cross-linked network. The degradation characteristics of the biodegradable PLA composite fiber gradually release space after fracturing.

Description

Technical Field

[0001] This invention relates to the field of fracturing fluid systems, specifically to a fiber fracturing fluid system and its preparation process. Background Technology

[0002] In the field of oil and gas fracturing operations, traditional fracturing fluid systems often employ a combination of conventional non-degradable fibers such as glass fiber and polypropylene fiber with synthetic polymer thickeners. This is achieved by adding proppant to enhance fracture propagation and conductivity. While this technology has established a stable application model in the development of unconventional oil and gas resources such as shale gas and tight oil, traditional non-degradable fibers are prone to leaving residues in the underground reservoir after fracturing operations, potentially causing reservoir damage such as fracture blockage and insufficient conductivity, while also leading to environmental pollution.

[0003] While existing technologies offer optimized solutions to address these issues, such as adding high-temperature resistant materials or increasing polymer crosslinking, these solutions often lack a system design that leverages the synergistic effects of multiple components. For example, the synergistic load-bearing effect of non-degradable fibers and proppant is limited, leading to insufficient long-term fracture conductivity; poor interfacial compatibility between inorganic fillers and organic matrices, along with uneven dispersion causing stress concentration, affects the material's mechanical properties and durability. Furthermore, the non-degradable nature of traditional fibers poses a long-term environmental pollution risk, while existing environmentally friendly alternatives still face technical bottlenecks in terms of degradability, temperature and salt resistance. Therefore, developing a two-component fiber fracturing fluid system with both high stability and controllable degradation has become a core technical challenge urgently needing to be solved in oil and gas field fracturing operations. Summary of the Invention

[0004] Technical problems to be solved To address the aforementioned shortcomings of existing technologies, this invention provides a fiber fracturing fluid system and its preparation process, which can effectively solve the technical defect of non-degradable fibers in existing fiber fracturing fluid systems.

[0005] Technical solution To achieve the above objectives, the present invention provides the following technical solution: A fiber fracturing fluid system, the fiber fracturing fluid system being composed of the following raw materials: biodegradable polylactic acid composite fiber, dodecylamine modified guar gum, organozirconium crosslinking agent, crosslinking accelerator sodium bicarbonate, and ceramsite proppant; The biodegradable polylactic acid composite fiber is obtained by spinning a mixture of acetylated modified cellulose and polylactic acid. The acetylated modified cellulose is obtained by acetylation modification of a coupling modified cellulose suspension. The dodecylamine-modified guar gum is prepared by etherification modification of hydroxypropyl guar gum.

[0006] Furthermore, the preparation steps of the coupling-modified cellulose suspension are as follows: Step A: Weigh 20g of cellulose nanofibers and pour them into 200mL of 80% ethanol solution. Stir at 400-500r / min for 30min, then add 1mL of silane coupling agent KH-550. Continue stirring at room temperature for 1h. The result is recorded as the mixed component. Step B: After washing the mixed components with deionized water, wash with anhydrous ethanol, and finally add 200 mL of anhydrous ethanol to obtain the coupling modified cellulose suspension.

[0007] Furthermore, the preparation steps of the acetylated modified cellulose are as follows: Step 1: Replace the ethanol solvent in the coupling-modified cellulose suspension with 200 mL of acetone, repeat 3 times, then replace the acetone solvent with 200 mL of N,N-dimethylformamide, repeat 3 times, then place it at 60℃ and distill under reduced pressure to remove excess water, and add 200 mL of N,N-dimethylformamide again. The resulting solution is called the N,N-dimethylformamide solution of cellulose. Step 2: Measure 100 mL of N,N-dimethylformamide solution of cellulose and pour it into a flask. Then, under stirring, add 30-35 mL of acetic anhydride and 0.5-1 g of 4-dimethylaminopyridine. Stir the reaction at 60°C for 1 h, wash twice with anhydrous ethanol, then wash twice with deionized water, and filter. The result is acetylated modified cellulose.

[0008] Furthermore, the stirring speed in step 2 is 300-400 r / min, and the stirring speed of the reaction in step 2 is 300-400 r / min.

[0009] Furthermore, the preparation steps of the biodegradable polylactic acid composite fiber are as follows: Step i: Weigh 3-5g of acetylated modified cellulose and disperse it in 100-150mL of dichloromethane. After stirring and dispersing, add 10-15g of polylactic acid and stir until the polylactic acid is completely dissolved. Continue stirring for 1 hour and let it stand to remove air bubbles. The resulting solution is called the spinning solution. Step ii: The solution to be spun is extruded through a spinneret into anhydrous ethanol to form fibers. After filtering to remove the filtrate, the fibers are dried in a 60°C oven for 12 hours and then cut to a fiber length of 3-12 mm. The resulting fiber is a biodegradable polylactic acid composite fiber.

[0010] Furthermore, the method of stirring and dispersing in step i is to stir at a stirring speed of 400-600 r / min for 10 min.

[0011] Furthermore, the preparation method of the dodecylamine-modified guar gum is as follows: S1. Weigh 50g of ethanol solution and 21-22g of dodecylamine and mix them. Place the mixture in a water bath at 60℃ and stir. Add glacial acetic acid to adjust the pH to 7. Add 9-10g of epichlorohydrin in 4 portions within 1 hour. The mixture after 3 hours of reaction is recorded as the etherification modifier. S2. Weigh 4-5g of hydroxypropyl guar gum and add it to 30g of ethanol solution. Add 4-5g of sodium hydroxide solution and alkalize at room temperature for 30min. Add 2-2.5g of etherification modifier and etherify at 50℃ for 3h. The result is recorded as the product component. S3. Wash the product components with anhydrous ethanol and filter them 3-5 times. Then dry them in an oven at 50°C for 24 hours. The result is dodecylamine modified guar gum.

[0012] Furthermore, the ethanol solution in S1 has a mass fraction of 95%, and the mixing method in S1 is to stir at a stirring speed of 300-500 r / min for 30 min. The ethanol solution in S2 has a mass fraction of 70%, and the sodium hydroxide solution in S2 has a mass fraction of 1%.

[0013] A preparation process for a fiber fracturing fluid system, wherein the preparation process is as follows: Step 1: Add 0.3-0.5 parts by weight of dodecylamine-modified guar gum to 100 parts by weight of deionized water, stir evenly, adjust the pH value to 4-5 with 2% sodium hydroxide solution, add 0.1-0.2 parts by weight of organozirconium crosslinking agent and stir to mix. The result is called fracturing fluid base fluid. Step 2: Add 0.5-0.6 parts by weight of biodegradable polylactic acid composite fiber, 0.2-0.3 parts by weight of crosslinking accelerator sodium bicarbonate and 20-30 parts by weight of ceramic proppant to the fracturing fluid base fluid. After stirring and dispersing, the resulting product is the fiber fracturing fluid system.

[0014] Furthermore, the method for uniform mixing in Step 1 is to stir at a speed of 400-600 r / min for 30 minutes, the method for mixing in Step 1 is to stir at a speed of 200-300 r / min for 10 minutes, and the method for dispersing in Step 2 is to stir at a speed of 300-500 r / min for 20 minutes.

[0015] Beneficial effects This invention provides a fiber fracturing fluid system and its preparation process. Compared with the prior art, this invention has the following advantages: 1. The acetylated modified cellulose in this invention is coupled with silane coupling agent KH-550 to introduce active groups on the cellulose surface, thereby improving the interfacial compatibility with polylactic acid. After acetylation modification, the polarity of the cellulose molecular chain is reduced, the hydrophobicity is enhanced, and the compatibility with polylactic acid is further optimized, enabling the formation of a uniform composite structure during the spinning process. This composite fiber serves as a supporting skeleton in fracturing operations, which can improve the viscoelasticity and proppant carrying capacity of the fracturing fluid through the fiber network, and can also achieve controlled degradation after fracturing due to the biodegradation characteristics of polylactic acid. This avoids reservoir damage caused by traditional fiber residues and achieves a dynamic balance between effective support during fracturing and timely degradation after fracturing. Secondly, the ceramsite proppant is uniformly dispersed in the fracturing fluid. Through the dual encapsulation effect of the fiber network and cross-linked network, it can achieve uniform settling and effective filling of the fracture. The degradation characteristics of the biodegradable polylactic acid composite fiber gradually release the channel space after fracturing, so that the ceramsite proppant forms a stable flow channel, improving the long-term flow capacity of the fracture, thereby avoiding the problem of proppant backflow or embedment in traditional fracturing fluids.

[0016] 2. In this invention, the hydroxypropyl guar gum, after being modified by dodecyl tertiary amine etherification, introduces long-chain alkyl and tertiary amine groups into its molecular chain. The cationic properties of dodecyl amine enhance the electrostatic repulsion between guar gum molecular chains, improving solution dispersibility. The etherification structure enhances the flexibility and salt resistance of the molecular chains. The modified guar gum forms a three-dimensional network structure in the fracturing fluid base, enabling it to undergo a synergistic crosslinking reaction with the organozirconium crosslinking agent, forming a high-strength, shear-resistant gel network. This effectively improves the temperature and shear resistance of the fracturing fluid, ensuring stable proppant carrying capacity under high temperature and high pressure conditions. Furthermore, the organozirconium crosslinking agent and the dodecyl amine-modified guar gum form a dynamic crosslinking network through coordination bonds. The crosslinking accelerator, sodium bicarbonate, adjusts the pH value of the system, promoting zirconium ion dissociation and crosslinking reaction rate, achieving controllable crosslinking process. This crosslinking network can form a dual-support structure with the fiber network of biodegradable polylactic acid composite fibers, providing both initial support strength and ensuring viscosity stability during fracturing. The synergistic effect of these two components achieves a balance between rapid initial fracturing and long-term support.

[0017] 3. The fiber fracturing fluid system prepared by this invention can achieve full-process functional optimization between fracturing, support, degradation and flow through the dynamic support of biodegradable composite fibers, intelligent thickening of modified guar gum, controllable crosslinking of the crosslinking system and synergistic effect of ceramic proppant. Each component forms functional complementarity at the microscopic molecular level through chemical modification and physical synergy, and achieves performance improvement at the macroscopic engineering level, ultimately achieving efficient, environmentally friendly and high-quality fracturing operations. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] The present invention will be further described below with reference to embodiments.

[0020] The sources of some components in the examples and comparative examples are as follows: Cellulose nanofibers, Ningbo Annail Nanotechnology Co., Ltd. Ethanol, Shandong Jinli Chemical Co., Ltd.; KH-550 silane coupling agent, Nanjing Tengchuan Technology Co., Ltd.; Acetone, Wuxi Dongneng Chemical Technology Co., Ltd.; N,N-Dimethylformamide, Shanghai Denuo Chemical Co., Ltd.; Acetic anhydride, Shandong Kaiyue Chemical Co., Ltd.; 4-Dimethylaminopyridine, Shandong Duoju Chemical Co., Ltd.; Dichloromethane, Shanghai Denuo Chemical Co., Ltd.; Polylactic acid, grade PLA2003D, has a number-average molecular weight of 155,500 and a weight-average molecular weight of 253,000. Dodecylamine, Shanghai Lingfeng Chemical Reagent Co., Ltd.; Glacial acetic acid, Shanghai Lingfeng Chemical Reagent Co., Ltd.; Epichlorohydrin, Shanghai Lingfeng Chemical Reagent Co., Ltd.; Hydroxypropyl guar gum, Beijing Baofengchun Petroleum Technology Co., Ltd.; Sodium hydroxide, Shanghai Lingfeng Chemical Reagent Co., Ltd. Ceramsite proppant, 20-40 mesh, Yixing Oriental Ceramsite Factory; Sodium bicarbonate, a cross-linking accelerator, is manufactured by Tianjin Tianda Chemical Reagent Factory in Dongli District, Tianjin.

[0021] Example 1 This embodiment provides a fiber fracturing fluid system, which is composed of the following raw materials: biodegradable polylactic acid composite fiber, dodecylamine-modified guar gum, organozirconium crosslinking agent, crosslinking accelerator sodium bicarbonate, and ceramsite support agent. The biodegradable polylactic acid composite fiber is obtained by spinning a mixture of acetylated modified cellulose and polylactic acid. The acetylated modified cellulose is obtained by acetylation modification of a coupling modified cellulose suspension. The preparation steps of the coupling-modified cellulose suspension are as follows: Step A: Weigh 20g of cellulose nanofibers and pour them into 200mL of 80% ethanol solution. Stir at 400r / min for 30min, then add 1mL of silane coupling agent KH-550. Continue stirring at room temperature for 1h. The result is recorded as the mixed component. Step B: After washing the mixed components with deionized water, wash with anhydrous ethanol, and finally add 200 mL of anhydrous ethanol to obtain the coupling modified cellulose suspension.

[0022] The preparation steps of acetylated modified cellulose are as follows: Step 1: Replace the ethanol solvent in the coupling-modified cellulose suspension with 200 mL of acetone, repeat 3 times, then replace the acetone solvent with 200 mL of N,N-dimethylformamide, repeat 3 times, then place it at 60℃ and distill under reduced pressure to remove excess water, and add 200 mL of N,N-dimethylformamide again. The resulting solution is called the N,N-dimethylformamide solution of cellulose. Step 2: Measure 100 mL of N,N-dimethylformamide solution of cellulose and pour it into a flask. Then, add 30 mL of acetic anhydride and 0.5 g of 4-dimethylaminopyridine while stirring at 300 r / min. After stirring at 60 °C for 1 h, wash twice with anhydrous ethanol and then twice with deionized water. Filter the solution to obtain acetylated modified cellulose.

[0023] The preparation steps of biodegradable polylactic acid composite fibers are as follows: Step i: Weigh 3g of acetylated modified cellulose and disperse it in 100mL of dichloromethane. Stir at 400r / min for 10min, then add 10g of polylactic acid and stir until the polylactic acid is completely dissolved. Continue stirring for 1h and let it stand to remove air bubbles. The resulting solution is called the spinning solution. Step ii: The solution to be spun is extruded through a spinneret into anhydrous ethanol to form fibers. After filtering to remove the filtrate, the fibers are dried in a 60°C oven for 12 hours and then cut to a fiber length of 3 mm. The resulting fiber is a biodegradable polylactic acid composite fiber.

[0024] Dodecylamine-modified guar gum is prepared by etherification modification of hydroxypropyl guar gum; The preparation method of dodecylamine-modified guar gum is as follows: S1. Weigh 50g of 95% ethanol solution and 21g of dodecylamine and mix them. Place the mixture in a water bath at 60℃ and stir at 300r / min for 30min. Add glacial acetic acid to adjust the pH to 7. Add 9g of epichlorohydrin in 4 portions over 1 hour. The mixture is then reacted for 3 hours and the resulting product is called the etherification modifier. S2. Weigh 4g of hydroxypropyl guar gum and add it to 30g of 70% ethanol solution. Add 4g of 1% sodium hydroxide solution and alkalize at room temperature for 30min. Add 2g of etherification modifier and etherify at 50℃ for 3h. The result is recorded as the product component. S3. After washing the product components with anhydrous ethanol and filtering them three times, dry them in an oven at 50°C for 24 hours. The result is dodecylamine-modified guar gum.

[0025] A preparation process for a fiber fracturing fluid system, the preparation process is as follows: Step 1: Add 0.3 parts by weight of dodecylamine-modified guar gum to 100 parts by weight of deionized water, stir at 400 r / min for 30 min, adjust the pH value to 4 with 2% sodium hydroxide solution, add 0.1 parts by weight of organozirconium crosslinking agent, and stir at 200 r / min for 10 min. The result is called fracturing fluid base fluid. Step 2: Add 0.5 parts by weight of biodegradable polylactic acid composite fiber, 0.2 parts by weight of crosslinking accelerator sodium bicarbonate and 20 parts by weight of ceramic proppant to the fracturing fluid base fluid. Stir at 300 r / min for 20 min to obtain the fiber fracturing fluid system.

[0026] Example 2 This embodiment provides a fiber fracturing fluid system, which is composed of the following raw materials: biodegradable polylactic acid composite fiber, dodecylamine-modified guar gum, organozirconium crosslinking agent, crosslinking accelerator sodium bicarbonate, and ceramsite support agent. The biodegradable polylactic acid composite fiber is obtained by spinning a mixture of acetylated modified cellulose and polylactic acid. The acetylated modified cellulose is obtained by acetylation modification of a coupling modified cellulose suspension. The preparation steps of the coupling-modified cellulose suspension are as follows: Step A: Weigh 20g of cellulose nanofibers and pour them into 200mL of 80% ethanol solution. Stir at 500r / min for 30min, then add 1mL of silane coupling agent KH-550. Continue stirring at room temperature for 1h. The result is recorded as the mixed component. Step B: After washing the mixed components with deionized water, wash with anhydrous ethanol, and finally add 200 mL of anhydrous ethanol to obtain the coupling modified cellulose suspension.

[0027] The preparation steps of acetylated modified cellulose are as follows: Step 1: Replace the ethanol solvent in the coupling-modified cellulose suspension with 200 mL of acetone, repeat 3 times, then replace the acetone solvent with 200 mL of N,N-dimethylformamide, repeat 3 times, then place it at 60℃ and distill under reduced pressure to remove excess water, and add 200 mL of N,N-dimethylformamide again. The resulting solution is called the N,N-dimethylformamide solution of cellulose. Step 2: Measure 100 mL of N,N-dimethylformamide solution of cellulose and pour it into a flask. Then, add 35 mL of acetic anhydride and 1 g of 4-dimethylaminopyridine while stirring at 400 r / min. Stir the mixture at 60 °C for 1 h at 400 r / min. Wash the mixture twice with anhydrous ethanol and twice with deionized water. Filter the mixture to obtain acetylated modified cellulose.

[0028] The preparation steps of biodegradable polylactic acid composite fibers are as follows: Step i: Weigh 5g of acetylated modified cellulose and disperse it in 150mL of dichloromethane. Stir at 600r / min for 10min, then add 15g of polylactic acid and stir until the polylactic acid is completely dissolved. Continue stirring for 1h and let it stand to remove air bubbles. The resulting solution is called the spinning solution. Step ii: The solution to be spun is extruded through a spinneret into anhydrous ethanol to form fibers. After filtering to remove the filtrate, the fibers are dried in a 60°C oven for 12 hours and then cut to a fiber length of 12 mm. The resulting fiber is a biodegradable polylactic acid composite fiber.

[0029] Dodecylamine-modified guar gum is prepared by etherification modification of hydroxypropyl guar gum; The preparation method of dodecylamine-modified guar gum is as follows: S1. Weigh 50g of 95% ethanol solution and 22g of dodecylamine and mix them. Place the mixture in a water bath at 60℃ and stir at 500r / min for 30min. Add glacial acetic acid to adjust the pH to 7. Add 10g of epichlorohydrin in 4 portions over 1 hour. The mixture after 3 hours of reaction is recorded as the etherification modifier. S2. Weigh 5g of hydroxypropyl guar gum and add it to 30g of 70% ethanol solution. Add 5g of 1% sodium hydroxide solution and alkalize at room temperature for 30min. Add 2.5g of etherification modifier and etherify at 50℃ for 3h. The result is recorded as the product component. S3. After washing the product components with anhydrous ethanol and filtering them 5 times, dry them in an oven at 50°C for 24 hours. The result is dodecylamine-modified guar gum.

[0030] A preparation process for a fiber fracturing fluid system, the preparation process is as follows: Step 1: Add 0.5 parts by weight of dodecylamine-modified guar gum to 100 parts by weight of deionized water, stir at 600 r / min for 30 min, adjust the pH value to 5 with 2% sodium hydroxide solution, add 0.2 parts by weight of organozirconium crosslinking agent, and stir at 300 r / min for 10 min. The result is called fracturing fluid base fluid. Step 2: Add 0.6 parts by weight of biodegradable polylactic acid composite fiber, 0.3 parts by weight of crosslinking accelerator sodium bicarbonate and 30 parts by weight of ceramic proppant to the fracturing fluid base fluid. Stir at 500 r / min for 20 min to obtain the fiber fracturing fluid system.

[0031] Example 3 This embodiment provides a fiber fracturing fluid system, which is composed of the following raw materials: biodegradable polylactic acid composite fiber, dodecylamine-modified guar gum, organozirconium crosslinking agent, crosslinking accelerator sodium bicarbonate, and ceramsite support agent. The biodegradable polylactic acid composite fiber is obtained by spinning a mixture of acetylated modified cellulose and polylactic acid. The acetylated modified cellulose is obtained by acetylation modification of a coupling modified cellulose suspension. The preparation steps of the coupling-modified cellulose suspension are as follows: Step A: Weigh 20g of cellulose nanofibers and pour them into 200mL of 80% ethanol solution. Stir at 500r / min for 30min, then add 1mL of silane coupling agent KH-550. Continue stirring at room temperature for 1h. The result is recorded as the mixed component. Step B: After washing the mixed components with deionized water, wash with anhydrous ethanol, and finally add 200 mL of anhydrous ethanol to obtain the coupling modified cellulose suspension.

[0032] The preparation steps of acetylated modified cellulose are as follows: Step 1: Replace the ethanol solvent in the coupling-modified cellulose suspension with 200 mL of acetone, repeat 3 times, then replace the acetone solvent with 200 mL of N,N-dimethylformamide, repeat 3 times, and then place it at 60℃ for vacuum distillation to remove excess water. After adding 200 mL of N,N-dimethylformamide again, the resulting solution is called the N,N-dimethylformamide solution of cellulose. Step 2: Measure 100 mL of N,N-dimethylformamide solution of cellulose and pour it into a flask. Add 32 mL of acetic anhydride and 0.8 g of 4-dimethylaminopyridine while stirring at 400 r / min. Stir the mixture at 60 °C for 1 h at 400 r / min. Wash the mixture twice with anhydrous ethanol and twice with deionized water. Filter the mixture to obtain acetylated modified cellulose.

[0033] The preparation steps of biodegradable polylactic acid composite fibers are as follows: Step i: Weigh 4g of acetylated modified cellulose and disperse it in 120mL of dichloromethane. Stir at 500r / min for 10min, then add 13g of polylactic acid and stir until the polylactic acid is completely dissolved. Continue stirring for 1h and let it stand to remove air bubbles. The resulting solution is called the spinning solution. Step ii: The solution to be spun is extruded through a spinneret into anhydrous ethanol to form fibers. After filtering to remove the filtrate, the fibers are dried in a 60°C oven for 12 hours and then cut to a fiber length of 8 mm. The resulting fiber is a biodegradable polylactic acid composite fiber.

[0034] Dodecylamine-modified guar gum is prepared by etherification modification of hydroxypropyl guar gum; The preparation method of dodecylamine-modified guar gum is as follows: S1. Weigh 50g of 95% ethanol solution and 22g of dodecylamine and mix them. Place the mixture in a water bath at 60℃ and stir at 400r / min for 30min. Add glacial acetic acid to adjust the pH to 7. Add 10g of epichlorohydrin in 4 portions over 1 hour. The mixture is then reacted for 3 hours and the resulting product is called the etherification modifier. S2. Weigh 5g of hydroxypropyl guar gum and add it to 30g of 70% ethanol solution. Add 5g of 1% sodium hydroxide solution and alkalize at room temperature for 30min. Add 2.2g of etherification modifier and etherify at 50℃ for 3h. The result is recorded as the product component. S3. After washing and filtering the product components with anhydrous ethanol four times, dry them in an oven at 50°C for 24 hours to obtain dodecylamine-modified guar gum.

[0035] A preparation process for a fiber fracturing fluid system, the preparation process is as follows: Step 1: Add 0.4 parts by weight of dodecylamine-modified guar gum to 100 parts by weight of deionized water, stir at 500 r / min for 30 min, adjust the pH value to 5 with 2% sodium hydroxide solution, add 0.2 parts by weight of organozirconium crosslinking agent, and stir at 300 r / min for 10 min. The result is called fracturing fluid base fluid. Step 2: Add 0.6 parts by weight of biodegradable polylactic acid composite fiber, 0.3 parts by weight of crosslinking accelerator sodium bicarbonate and 25 parts by weight of ceramic proppant to the fracturing fluid base fluid. Stir at 400 r / min for 20 min to obtain the fiber fracturing fluid system.

[0036] Comparative Example 1 The fiber fracturing fluid system and its preparation process provided in this comparative example are roughly the same as those in Example 1. The main difference is that the biodegradable polylactic acid composite fiber in Example 1 is replaced with polylactic acid fiber in this comparative example.

[0037] Comparative Example 2 The fiber fracturing fluid system and its preparation process provided in this comparative example are roughly the same as those in Example 1. The main difference is that the dodecylamine-modified guar gum in Example 1 is replaced with hydroxypropyl guar gum in this comparative example.

[0038] Performance testing The fiber fracturing fluid systems prepared in Examples 1-3 and Comparative Examples 1-2 were labeled as Example 1, Example 2, Example 3, Comparative Example 1, and Comparative Example 2, respectively. Performance tests were conducted on Examples 1-3 and Comparative Examples 1-2, and the test items and data were recorded as follows: 1. The settling rates of Examples 1-3 and Comparative Examples 1-2 were tested, and the data obtained are recorded in Table 1; 2. The fiber escape rate of Examples 1-3 and Comparative Examples 1-2 was tested, and the data obtained are recorded in Table 2; Table 1 Settlement Rate Data Table 2 Fiber Escape Rate Data Table The data in the table above shows that the settling velocity and fiber escape rate of the fiber fracturing fluid system prepared in Examples 1-3 are significantly lower than those in Comparative Examples 1-2, indicating that the fiber fracturing fluid system prepared by the present invention has better sand suspension performance and more stable and uniform fiber dispersion, and has good promotion value.

[0039] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between such entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only such elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Without further limitations, an element qualified as "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that comprise that element.

[0040] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fiber fracturing fluid system, characterized in that, The fiber fracturing fluid system is composed of the following raw materials: biodegradable polylactic acid composite fiber, dodecylamine modified guar gum, organozirconium crosslinking agent, crosslinking accelerator sodium bicarbonate, and ceramsite support agent; The biodegradable polylactic acid composite fiber is obtained by spinning a mixture of acetylated modified cellulose and polylactic acid. The acetylated modified cellulose is obtained by acetylation modification of a coupling modified cellulose suspension. The dodecylamine-modified guar gum is prepared by etherification modification of hydroxypropyl guar gum.

2. The fiber fracturing fluid system according to claim 1, characterized in that, The preparation steps of the coupling-modified cellulose suspension are as follows: Step A: Weigh 20g of cellulose nanofibers and pour them into 200mL of 80% ethanol solution. Stir at 400-500r / min for 30min, then add 1mL of silane coupling agent KH-550. Continue stirring at room temperature for 1h. The result is recorded as the mixed component. Step B: After washing the mixed components with deionized water, wash with anhydrous ethanol, and finally add 200 mL of anhydrous ethanol to obtain the coupling modified cellulose suspension.

3. The fiber fracturing fluid system according to claim 1, characterized in that, The preparation steps of the acetylated modified cellulose are as follows: Step 1: Replace the ethanol solvent in the coupling-modified cellulose suspension with 200 mL of acetone, repeat 3 times, then replace the acetone solvent with 200 mL of N,N-dimethylformamide, repeat 3 times, then place it at 60℃ and distill under reduced pressure to remove excess water, and add 200 mL of N,N-dimethylformamide again. The resulting solution is called the N,N-dimethylformamide solution of cellulose. Step 2: Measure 100 mL of N,N-dimethylformamide solution of cellulose and pour it into a flask. Then, under stirring, add 30-35 mL of acetic anhydride and 0.5-1 g of 4-dimethylaminopyridine. Stir the reaction at 60°C for 1 h, wash twice with anhydrous ethanol, then wash twice with deionized water, and filter. The result is acetylated modified cellulose.

4. The fiber fracturing fluid system according to claim 3, characterized in that, The stirring speed in step 2 is 300-400 r / min, and the stirring speed for the reaction in step 2 is 300-400 r / min.

5. The fiber fracturing fluid system according to claim 1, characterized in that, The preparation steps of the biodegradable polylactic acid composite fiber are as follows: Step i: Weigh 3-5g of acetylated modified cellulose and disperse it in 100-150mL of dichloromethane. After stirring and dispersing, add 10-15g of polylactic acid and stir until the polylactic acid is completely dissolved. Continue stirring for 1 hour and let it stand to remove air bubbles. The resulting solution is called the spinning solution. Step ii: The solution to be spun is extruded through a spinneret into anhydrous ethanol to form fibers. After filtering to remove the filtrate, the fibers are dried in a 60°C oven for 12 hours and then cut to a fiber length of 3-12 mm. The resulting fiber is a biodegradable polylactic acid composite fiber.

6. The fiber fracturing fluid system according to claim 5, characterized in that, The method for stirring and dispersing in step i is to stir at a stirring speed of 400-600 r / min for 10 min.

7. The fiber fracturing fluid system according to claim 1, characterized in that, The preparation method of the dodecylamine-modified guar gum is as follows: S1. Weigh 50g of ethanol solution and 21-22g of dodecylamine and mix them. Place the mixture in a water bath at 60℃ and stir. Add glacial acetic acid to adjust the pH to 7. Add 9-10g of epichlorohydrin in 4 portions within 1 hour. The mixture after 3 hours of reaction is recorded as the etherification modifier. S2. Weigh 4-5g of hydroxypropyl guar gum and add it to 30g of ethanol solution. Then add 4-5g of sodium hydroxide solution and alkalize at room temperature for 30min. Add 2-2.5g of etherification modifier and etherify at 50℃ for 3h. The result is recorded as the product component. S3. Wash the product components with anhydrous ethanol and filter them 3-5 times. Then dry them in an oven at 50°C for 24 hours. The result is dodecylamine modified guar gum.

8. The fiber fracturing fluid system according to claim 7, characterized in that, The ethanol solution in S1 has a mass fraction of 95%, and the mixing method in S1 is to stir at a stirring speed of 300-500 r / min for 30 min. The ethanol solution in S2 has a mass fraction of 70%, and the sodium hydroxide solution in S2 has a mass fraction of 1%.

9. The preparation process of a fiber fracturing fluid system according to any one of claims 1-8, characterized in that, The preparation process is as follows: Step 1: Add 0.3-0.5 parts by weight of dodecylamine-modified guar gum to 100 parts by weight of deionized water, stir evenly, adjust the pH value to 4-5 with 2% sodium hydroxide solution, add 0.1-0.2 parts by weight of organozirconium crosslinking agent and stir to mix. The result is called fracturing fluid base fluid. Step 2: Add 0.5-0.6 parts by weight of biodegradable polylactic acid composite fiber, 0.2-0.3 parts by weight of crosslinking accelerator sodium bicarbonate and 20-30 parts by weight of ceramic proppant to the fracturing fluid base fluid. After stirring and dispersing, the resulting product is the fiber fracturing fluid system.

10. The preparation process of a fiber fracturing fluid system according to claim 9, characterized in that, The method for mixing evenly in Step 1 is to stir at a stirring speed of 400-600 r / min for 30 minutes. The method for mixing in Step 1 is to stir at a stirring speed of 200-300 r / min for 10 minutes. The method for dispersing in Step 2 is to stir at a stirring speed of 300-500 r / min for 20 minutes.

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