Environment-friendly drag reducer for fracturing as well as preparation process and application of drag reducer

Abstract

The invention relates to the technical field of oilfield exploitation, and particularly discloses an environment-friendly drag reducer for fracturing as well as a preparation process and application thereof. The environment-friendly drag reducer for fracturing comprises the following raw materials in parts by weight: 30-50 parts of hydrophobic modified cellulose, 15-25 parts of a zwitterionic surfactant, 5-8 parts of an organic zirconium cross-linking agent, 1-3 parts of a pH regulator and 100-200 parts of deionized water, and the hydrophobic modified cellulose is hydroxypropyl methyl cellulose esterified and modified by maleic anhydride; the preparation method comprises the following steps: dissolving the ampholytic surfactant in deionized water to form a homogeneous solution, sequentially adding the hydrophobic modified cellulose and the organic zirconium cross-linking agent, regulating the pH to 6.5-7.5 by using the pH regulator, and fully stirring; and homogenizing and curing at 20-40 MPa to obtain the environment-friendly drag reducer for fracturing. The product provided by the invention can be used in oil and gas field fracturing operation, and has the advantages of good drag reduction effect and high stability.

Description

Technical Field

[0001] The present application relates to the technical field of oilfield exploitation, and more specifically, to an environmentally friendly drag reducer for fracturing, and its preparation process and application. Background Art

[0002] In the oil and gas production process, fracturing is a key technology for increasing oil and gas well production. As the core working medium in fracturing operations, the properties of fracturing fluid directly impact fracturing effectiveness and production efficiency. Drag reduction is a key indicator of fracturing fluid quality. Good drag reduction can effectively reduce flow resistance in the wellbore and fractures, minimizing turbulent energy consumption and improving fluid delivery efficiency, thereby reducing energy consumption and costs during fracturing operations.

[0003] However, traditional fracturing drag reducers present numerous challenges in practical application. First, some traditional drag reducers struggle to maintain high drag reduction performance in complex formation conditions. Under high temperature and pressure, the structure of traditional drag reducers is easily damaged, significantly reducing their drag reduction capacity and making them inadequate for actual fracturing operations. For example, some polymer-based drag reducers degrade at high temperatures, breaking down their molecular chains and significantly reducing their drag reduction effectiveness.

[0004] Secondly, traditional fracturing drag reducers significantly impact the formation environment. Many contain strong acidic or alkaline components. These components, when in contact with formation rock, can severely corrode it, damaging the formation structure and impacting formation stability and the integrity of oil and gas reservoirs. Furthermore, traditional drag reducers are poorly biodegradable, leaving harmful residues in the formation after use, polluting the environment and failing to meet current green mining requirements. Summary of the Invention

[0005] In order to solve the above problems, the present application provides an environmentally friendly drag reducer for fracturing and its preparation process and application.

[0006] In the first aspect, the present application provides an environmentally friendly drag reducer for fracturing, which adopts the following technical solution: An environmentally friendly drag reducer for fracturing, comprising the following raw materials in parts by weight: 30-50 parts of hydrophobically modified cellulose, 15-25 parts of zwitterionic surfactant, 5-8 parts of organic zirconium crosslinking agent, 1-3 parts of pH regulator, and 100-200 parts of deionized water. The hydrophobically modified cellulose is hydroxypropyl methylcellulose modified by maleic anhydride esterification.

[0007] By adopting the above technical solution, this environmentally friendly drag reducer forms a hydrophobic branched structure through maleic anhydride-esterified hydroxypropyl methylcellulose, creating a spatial network framework in the fracturing fluid to enhance viscoelasticity. This structure synergizes with the electrostatic adsorption and interfacial lubrication of zwitterionic surfactants to reduce fluid frictional resistance. An organic zirconium crosslinker forms dynamic crosslinking points with the carboxyl groups of the cellulose backbone through multinuclear hydroxyl bridge complexes, enhancing the system's heat and shear resistance. A pH regulator maintains a weakly acidic environment, promoting the controlled crosslinking reaction while preventing strong acid corrosion of formation rocks. Deionized water serves as a solvent to uniformly disperse all components. Through the synergistic action of these components, the drag reducer reduces turbulent energy consumption during wellbore flow through viscoelastic effects and interfacial drag reduction mechanisms. Furthermore, the crosslinked network maintains fracture width as the fracture extends, ultimately achieving the dual functions of efficient drag reduction and formation protection.

[0008] Optionally, the hydrophobically modified cellulose specifically comprises the following steps: esterifying cellulose with maleic anhydride at 75-85° C. for 4 hours under nitrogen protection to obtain the hydrophobically modified cellulose, wherein the weight ratio of the cellulose to maleic anhydride is 1:0.2-0.4.

[0009] By adopting the above technical solution, the hydrophobically modified cellulose undergoes an esterification reaction with maleic anhydride through the hydroxyl groups of the cellulose molecular chain. Under mild reaction conditions under nitrogen protection, the carboxylic anhydride ring is opened and hydrophobic ester side chains are directionally grafted, thereby retaining the natural hydrophilic network structure of the cellulose skeleton and giving it controllable hydrophobic properties. The nitrogen environment in the reaction isolates the interference of water and oxygen, avoids side reactions, and makes the ester groups evenly distributed on the molecular chain in the form of stable covalent bonds, forming a modified product with both hydrophilic and hydrophobic dual-phase structures. This structure can enhance the entanglement between molecular chains through hydrophobic association, while the carboxyl groups retain the subsequent cross-linking active sites, significantly improving the viscoelasticity and shear resistance of the drag reducer solution.

[0010] Optionally, the organic zirconium cross-linking agent is a complex of zirconium lactate and acetylacetone, with a zirconium content greater than 8%, and the preparation comprises the following steps: a) mixing zirconium lactate and acetylacetone in a weight ratio of 1:1-1.4 and dissolving in anhydrous ethanol; b) reflux the reaction at 60-70° C. for 6-8 hours, and remove the solvent by distillation under reduced pressure to obtain an orange-red viscous liquid.

[0011] By adopting the above technical scheme, the coordination and complex reaction of zirconium lactate and acetylacetone constructs a dynamic cross-linked core structure: in ethanol solvent, the zirconium ions of zirconium lactate and the β-diketone structure of acetylacetone undergo strong coordination to form a zirconium-acetylacetone complex with a five-membered ring chelate configuration, and its high zirconium content is designed to ensure the density of cross-linking sites; the specific molar ratio regulation not only avoids precipitation caused by excessive zirconium ions, but also inhibits excessive cross-linking through the steric hindrance effect of acetylacetone, giving the system controllable delayed cross-linking properties; the coordination bonds are gradually and stably formed in the reflux reaction, and after the solvent is removed by vacuum distillation, the product exists as an orange-red viscous liquid with both high reactivity and storage stability; the cross-linking agent realizes the reversible construction of the cross-linked network through the dynamic equilibrium of carboxyl-zirconium coordination-dissociation in the fracturing fluid, significantly improving the temperature and shear resistance of the system, while avoiding the residue pollution caused by traditional cross-linking agents, and having the advantages of high efficiency gelation and environmental protection.

[0012] Optionally, the pH regulator is any one of sodium citrate or triethanolamine.

[0013] By adopting the above technical solution, sodium citrate, as a polycarboxylate buffer, can maintain a weak acid to neutral range through the dissociation balance between its carboxyl group and hydroxide, thereby avoiding the damage of strong acid to the zirconium cross-linker or cellulose. At the same time, the carboxylate anion can form a weak coordination with the zirconium ion to assist in regulating the cross-linking dynamics; triethanolamine achieves pH buffering through the protonation / deprotonation of the tertiary amine group, and its alcoholic hydroxyl group can form a hydrogen bond network with water molecules, thereby enhancing the water retention of the system and inhibiting the risk of precipitation of zirconium ions under alkaline conditions; both achieve pH control through a non-corrosive mechanism, which not only ensures the active window of the cross-linking reaction, but also avoids acid and alkali corrosion of the formation rock, while improving the overall stability and environmental friendliness of the fracturing fluid system, and is suitable for pH-sensitive formation conditions.

[0014] Optionally, the zwitterionic surfactant is cocamidopropyl hydroxysulfobetaine, and the critical micelle concentration is ≤0.5 g / L.

[0015] By adopting the above technical solution, a dense adsorption layer and a micellar structure are formed at the interface through the synergistic effect of the amide group and the sulfonic acid group in the molecule, which effectively reduces the internal friction resistance of the fluid. At the same time, its zwitterionic properties give it strong resistance to hard water and biodegradability, avoiding the pollution of traditional drag reducers to the environment, and forming a composite system with the other components in the drag reducer, further enhancing the drag reduction effect.

[0016] Optionally, the deionized water contains 1-3 wt% of nano-silicon dioxide with a particle size of 10-20 nm.

[0017] By adopting the above technical solution, nano-silica, with its nanoscale particle size and large specific surface area, can form a highly dispersed colloidal system in deionized water. Its surface hydroxyl groups associate with water molecules through hydrogen bonding, effectively preventing particle agglomeration. At the same time, its surface potential can form a double-layer structure with trace ions in deionized water, further enhancing the steric hindrance effect, thereby significantly improving the dispersion stability and wetting properties of deionized water. In the fracturing fluid system, nano-silica can form a synergistic effect with cocamidopropyl hydroxysulfobetaine. Its tiny particle size fills the gaps between micelles, inhibiting micelle aggregation through a dual mechanism of physical barrier and electrostatic repulsion. The surface hydroxyl groups interact weakly with the polar groups of the betaine molecules to form a dynamically stable composite dispersion system. This synergistic effect not only enhances the dispersion uniformity of the drag reducer, but also reduces fluid flow resistance through the ball-bearing effect of the nanoparticles. At the same time, the micro-nanostructure of nano-silica can adsorb and inhibit the hydration expansion of clay minerals in the formation, which, together with the environmentally friendly properties of the drag reducer, improves the efficiency of fracturing operations and the effectiveness of formation protection.

[0018] In a second aspect, the present application provides a process for preparing an environmentally friendly drag reducer for fracturing, which adopts the following technical solution: A process for preparing an environmentally friendly drag reducer for fracturing, comprising the following steps: S1. Dissolve the amphoteric surfactant in deionized water and stir at a constant temperature of 30-40°C for 1-1.5 hours to form a homogeneous solution; S2. To the above solution, hydrophobically modified cellulose and an organic zirconium crosslinker were sequentially added, and the pH was adjusted to 6.5-7.5 using a pH adjuster, and stirred at 200-400 rpm for 20-30 min; S3. After high-pressure homogenization at 20-40 MPa and aging at 55-65°C for 10-12 hours, an amber transparent colloid is obtained, which is an environmentally friendly drag reducer for fracturing.

[0019] By adopting the above technical solution, first, the amphoteric surfactant is dissolved in deionized water and stirred at a constant temperature to form a homogeneous solution. This step provides a stable basic environment for subsequent reactions; then, hydrophobically modified cellulose and an organic zirconium cross-linker are added in sequence, and the pH is adjusted to an appropriate range and stirred. The hydrophobically modified cellulose can enhance the structural stability and drag reduction performance of the system, and the organic zirconium cross-linker can promote the cross-linking reaction between molecules at a suitable pH to form a more stable network structure; finally, high-pressure homogenization treatment is used to make the system more uniform and delicate, and then the molecules are further allowed to interact and optimize the structure through a maturation process, ultimately obtaining an amber-colored, transparent, colloidal, and environmentally friendly drag reducer for fracturing.

[0020] In a third aspect, the present application provides an application of an environmentally friendly drag reducer for fracturing in oil production fracturing.

[0021] In summary, this application has the following beneficial effects: 1. Due to the synergistic effect of the spatial network skeleton constructed by hydrophobically modified cellulose and the zwitterionic surfactant in this application, the friction resistance of the fluid in the wellbore and fractures is significantly reduced, and the turbulent energy consumption is reduced, thereby improving the delivery efficiency of the fracturing fluid, enabling the fracturing operation to be carried out more efficiently, and reducing energy consumption and operating costs.

[0022] 2. This application uses sodium citrate or triethanolamine as a pH adjuster to maintain a weakly acidic environment in the system, preventing strong acid corrosion of the formation rock and protecting the formation structure. Furthermore, the zwitterionic surfactant has strong resistance to hard water and biodegradability. The addition of nanosilica further enhances the environmental friendliness of the system, reducing environmental pollution and meeting the requirements of green mining.

[0023] 3. The organic zirconium crosslinker in this application forms dynamic crosslinking points with the carboxyl groups of the cellulose backbone via multinuclear hydroxyl bridge complexes, enhancing the system's heat and shear resistance, allowing the drag reducer to maintain a stable network structure even under high-temperature and high-pressure environments. As the crack extends, this crosslinked network maintains the crack width, promoting efficient distribution of the fracturing fluid within the crack and enhancing the fracturing effect. This avoids residue contamination associated with traditional crosslinkers, ensuring the long-term effectiveness of the fracturing operation. DETAILED DESCRIPTION

[0024] The present application is further described in detail below with reference to the embodiments.

[0025] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0026] Hydroxypropyl methylcellulose, viscosity 2000-4000 mPa·s; maleic anhydride, industrial grade, purity ≥99%.

[0027] Preparation examples of raw materials and / or intermediates Preparation Example 1 A hydrophobically modified cellulose, the preparation of which comprises the following steps: Under nitrogen protection, 10 kg of hydroxypropyl methylcellulose was added to 30 kg of dimethyl sulfoxide and stirred to disperse uniformly. 3 kg of maleic anhydride was added and continued to stir and heat to 60 ° C for pre-dispersion for 30 minutes. 0.1 kg of concentrated sulfuric acid was added dropwise as a catalyst, and the temperature was gradually increased to 80 ° C. and the reaction was maintained at 500 rpm for 4 hours. After the reaction was completed, glacial acetic acid was added to slowly adjust the pH of the system to 5.5 to terminate the reaction. After washing, centrifugation and drying, the hydrophobically modified cellulose was obtained.

[0028] Preparation Example 2 A hydrophobically modified cellulose, the preparation of which comprises the following steps: Under nitrogen protection, 10 kg of hydroxypropyl methylcellulose was added to 30 kg of dimethyl sulfoxide and uniformly dispersed, 2 kg of maleic anhydride was added, stirring was continued, and the mixture was heated to 60° C. for pre-dispersion for 30 minutes. 0.1 kg of concentrated sulfuric acid was added dropwise as a catalyst, and the temperature was gradually increased to 75° C., and the reaction was maintained at a speed of 500 rpm for 4 hours. After the reaction was completed, glacial acetic acid was added to slowly adjust the pH of the system to 5.0 to terminate the reaction. After washing, centrifugation, and drying, the hydrophobically modified cellulose was obtained.

[0029] Preparation Example 3 A hydrophobically modified cellulose, the preparation of which comprises the following steps: Under nitrogen protection, 10 kg of hydroxypropyl methylcellulose was added to 30 kg of dimethyl sulfoxide and uniformly dispersed, 4 kg of maleic anhydride was added, stirring was continued, and the mixture was heated to 60° C. for pre-dispersion for 30 minutes. 0.1 kg of concentrated sulfuric acid was added dropwise as a catalyst, and the temperature was gradually increased to 85° C., and the reaction was maintained at a speed of 500 rpm for 4 hours. After the reaction was completed, glacial acetic acid was added to slowly adjust the pH of the system to 6.0 to terminate the reaction. The mixture was washed, centrifuged, and dried to obtain the hydrophobically modified cellulose.

[0030] Preparation Example 4 An organic zirconium cross-linking agent, the preparation of which comprises the following steps: a) Mix 5 kg of zirconium lactate and 5 kg of acetylacetone, add them into 30 kg of anhydrous ethanol and stir evenly; b) heating to 65° C. and subjecting the mixture to reflux reaction for 7 hours. After the reaction, the solvent was removed by distillation under reduced pressure to obtain an orange-red viscous liquid, which was the organic zirconium cross-linking agent.

[0031] Preparation Example 5 An organic zirconium cross-linking agent, the preparation of which comprises the following steps: a) Mix 5 kg of zirconium lactate and 6 kg of acetylacetone, add to 30 kg of anhydrous ethanol and stir evenly; b) heating to 60° C. and subjecting the mixture to reflux reaction for 8 hours. After the reaction, the solvent was removed by distillation under reduced pressure to obtain an orange-red viscous liquid, which was the organic zirconium cross-linking agent.

[0032] Preparation Example 6 An organic zirconium cross-linking agent, the preparation of which comprises the following steps: a) Mix 5 kg of zirconium lactate and 7 kg of acetylacetone, add to 30 kg of anhydrous ethanol and stir evenly; b) heating to 70° C. and subjecting the mixture to reflux reaction for 6 hours. After the reaction, the solvent was removed by distillation under reduced pressure to obtain an orange-red viscous liquid, which was the organic zirconium cross-linking agent. Example

[0033] Example 1 An environmentally friendly drag reducer for fracturing, the preparation of which comprises the following steps: S1. 2 kg of cocamidopropyl hydroxysulfobetaine (amphoteric surfactant) was dissolved in 15 kg of deionized water and stirred at 400 rpm for 1 h at 35 ° C to form a homogeneous solution; S2. To the above solution were added 4kg of the hydrophobically modified cellulose prepared in Preparation Example 1, 0.65kg of the organic zirconium crosslinker prepared in Preparation Example 4, and 0.15kg of sodium citrate was added to adjust the pH to 6.5-7.5, and stirred at 300rpm for 30min; S3. After high-pressure homogenization at 30 MPa and aging at 60°C for 11 hours, an amber transparent colloid was obtained, which is an environmentally friendly drag reducer for fracturing.

[0034] Example 2 An environmentally friendly drag reducer for fracturing, the preparation of which comprises the following steps: S1. 1.5 kg of cocamidopropyl hydroxysulfobetaine (amphoteric surfactant) was dissolved in 20 kg of deionized water and stirred at 400 rpm for 1 h at 30 ° C to form a homogeneous solution; S2. To the above solution were added 5kg of the hydrophobically modified cellulose prepared in Preparation Example 2, 0.8kg of the organic zirconium crosslinker prepared in Preparation Example 5, and 0.1kg of sodium citrate was added to adjust the pH to 6.5-7.5, and stirred at 200rpm for 30min; S3. After high-pressure homogenization at 40 MPa and aging at 55°C for 10 h, an amber transparent colloid was obtained, which is an environmentally friendly drag reducer for fracturing.

[0035] Example 3 An environmentally friendly drag reducer for fracturing, the preparation of which comprises the following steps: S1. 2.5 kg of cocamidopropyl hydroxysulfobetaine (amphoteric surfactant) was dissolved in 10 kg of deionized water and stirred at 400 rpm for 1 h at 40 ° C to form a homogeneous solution; S2. To the above solution were added 3kg of the hydrophobically modified cellulose prepared in Preparation Example 3, 0.5kg of the organic zirconium crosslinker prepared in Preparation Example 6, and 0.3kg of sodium citrate was added to adjust the pH to 6.5-7.5, and stirred at 400rpm for 20min; S3. After high-pressure homogenization at 20 MPa and aging at 65°C for 12 hours, an amber transparent colloid is obtained, which is an environmentally friendly drag reducer for fracturing.

[0036] Example 4 An environmentally friendly drag reducer for fracturing, which is different from Example 1 in that the amphoteric surfactant used in this example is dodecyl dimethyl betaine.

[0037] Example 5 An environmentally friendly drag reducer for fracturing is different from Example 1 in that the pH regulator used in this example is triethanolamine.

[0038] Example 6 An environmentally friendly drag reducer for fracturing, which is different from Example 1 in that the pH regulator used in this example is sodium hydroxide.

[0039] Example 7 An environmentally friendly drag reducer for fracturing, which differs from Example 1 in that 0.15 kg of nano-silica with a particle size of 10-20 nm is added to the deionized water in this embodiment, 0.15 kg of nano-silica is added to 15 kg of deionized water and dispersed evenly, and then 2 kg of cocamidopropyl hydroxysulfobetaine (amphoteric surfactant) is added to dissolve it, and the remaining steps are the same as in Example 1.

[0040] Example 8 An environmentally friendly drag reducer for fracturing, which is different from Example 7 in that 0.3 kg of nano-silicon dioxide with a particle size of 10-20 nm is added to the deionized water added in this example.

[0041] Example 9 An environmentally friendly drag reducer for fracturing, which is different from Example 7 in that 0.45 kg of nano-silicon dioxide with a particle size of 10-20 nm is added to the deionized water in this example.

[0042] Example 10 An environmentally friendly drag reducer for fracturing, which is different from Example 1 in that the cellulose added in this example is not modified.

[0043] Comparative Example Comparative Example 1 An environmentally friendly drag reducer for fracturing is disclosed. The difference from Example 1 is that in this comparative example, an equal amount of unmodified hydroxypropyl methylcellulose is used to replace the hydrophobically modified cellulose, and an equal amount of borax crosslinking agent is used to replace the organic zirconium crosslinking agent. The rest is the same as Example 1.

[0044] Comparative Example 2 An environmentally friendly drag reducer for fracturing is disclosed. The difference from Example 1 is that in this comparative example, an organic zirconium cross-linking agent is replaced by an equal amount of a borax cross-linking agent. The rest is the same as in Example 1.

[0045] Comparative Example 3 An environmentally friendly drag reducer for fracturing is disclosed, which differs from Example 1 in that cocamidopropyl hydroxysulfobetaine is not added in this comparative example.

[0046] Application Examples 1-13 Application of the environmentally friendly drag reducers for fracturing prepared in Examples 1-10 and Comparative Examples 1-3 in oil production fracturing.

[0047] Performance testing Detection method / test method Drag reduction rate: tested in accordance with the relevant methods described in SY / T 6376-2008 "General Technical Requirements for Fracturing Fluids"; Temperature resistance: Viscosity retention rate was tested after hot rolling at 150℃ for 16 hours; Biodegradation rate: The biodegradation rate (%) of the drag reducer after 28 days was tested by OECD 301B rapid biodegradability test for chemicals.

[0048] Table 1 Test data Combining Examples 1-3 and Comparative Example 1 with Table 1, it can be seen that the experimental data of Examples 1-3 are better than those of Comparative Example 1, indicating that the combined effect of hydrophobically modified cellulose and organic zirconium crosslinking agent significantly improves the performance of the drag reducer.

[0049] Combining Examples 1-3 and Comparative Example 2 with Table 1, it can be seen that the experimental data of Examples 1-3 are better than those of Comparative Example 2, indicating that the organic zirconium crosslinker has obvious advantages over other crosslinkers in improving the performance of environmentally friendly drag reducers for fracturing. The organic zirconium crosslinker has better synergistic effects with other components in the system and can more effectively improve the comprehensive performance of the drag reducer.

[0050] Combining Examples 1-3 and Comparative Example 3 with Table 1, it can be seen that the experimental data of Examples 1-3 are better than those of Comparative Example 3, indicating that the cocamidopropyl hydroxysulfobetaine amphoteric surfactant plays an important role in environmentally friendly drag reducers for fracturing. It can improve the dispersibility of the drag reducer system and reduce the interfacial tension, thereby improving the overall performance of the drag reducer. At the same time, its strong resistance to hard water and biodegradability also help to improve environmental protection.

[0051] Combining Examples 1-4 and Table 1, it can be seen that the experimental data of Examples 1-3 are better than those of Example 4, indicating that cocamidopropyl hydroxysulfobetaine amphoteric surfactant is more suitable for preparing environmentally friendly drag reducers for fracturing than dodecyl dimethyl betaine, and can better interact with other components in the system, thereby improving the drag reduction effect, stability and other properties of the drag reducer.

[0052] Combining Example 1 with Examples 5-6 and Table 1, it can be seen that the experimental data of Example 1 and Example 5 are better than those of Example 6, indicating that sodium citrate and triethanolamine are more conducive to improving the performance of environmentally friendly drag reducers for fracturing than sodium hydroxide in the selection of pH adjusters. In addition, sodium citrate and triethanolamine, as weak bases or organic bases, can more gently adjust the pH of the system and maintain the stability of the system, thereby better exerting the function of the drag reducer.

[0053] Combining Example 1 with Examples 7-9 and Table 1, it can be seen that the experimental data of Examples 7-9 are better than those of Example 1, indicating that adding an appropriate amount of nano-silica with a particle size of 10-20 nm to the environmentally friendly drag reducer system for fracturing can further improve its performance. Nano-silica can form a synergistic effect with cocamidopropyl hydroxysulfobetaine, enhance the dispersion uniformity of the drag reducer, reduce fluid flow resistance, and inhibit the hydration expansion of clay minerals in the formation, thereby improving the efficiency of the fracturing operation and the formation protection effect.

[0054] Combining Example 1 with Example 10 and Table 1, it can be seen that the experimental data of Example 1 are better than those of Example 10, indicating that hydrophobically modified cellulose is more suitable for preparing environmentally friendly drag reducers for fracturing than unmodified hydroxypropyl methylcellulose. The hydrophobic modification treatment can give cellulose new properties, such as better hydrophobicity and stronger interaction with other components in the system, thereby improving the drag reduction effect, stability and other properties of the drag reducer.

[0055] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. An environmentally friendly drag reducer for fracturing, characterized in that: It includes the following raw materials in parts by weight: 30-50 parts of hydrophobically modified cellulose, 15-25 parts of zwitterionic surfactant, 5-8 parts of organic zirconium crosslinking agent, 1-3 parts of pH regulator, and 100-200 parts of deionized water. The hydrophobically modified cellulose is hydroxypropyl methylcellulose modified by maleic anhydride esterification.

2. The environmentally friendly drag reducer for fracturing according to claim 1, characterized in that: The hydrophobically modified cellulose specifically includes the following preparation steps: esterifying cellulose and maleic anhydride at 75-85° C. for 4 hours under nitrogen protection to obtain the hydrophobically modified cellulose, wherein the weight ratio of the cellulose to the maleic anhydride is 1:0.2-0.

4.

3. The environmentally friendly drag reducer for fracturing according to claim 1, characterized in that: The organic zirconium cross-linking agent is a complex of zirconium lactate and acetylacetone, and its preparation comprises the following steps: a) mixing zirconium lactate and acetylacetone in a weight ratio of 1:1-1.4 and dissolving in anhydrous ethanol; b) reflux the reaction at 60-70° C. for 6-8 hours, and remove the solvent by distillation under reduced pressure to obtain an orange-red viscous liquid.

4. The environmentally friendly drag reducer for fracturing according to claim 1, characterized in that: The pH regulator is any one of sodium citrate or triethanolamine.

5. The environmentally friendly drag reducer for fracturing according to claim 1, characterized in that: The zwitterionic surfactant is cocamidopropyl hydroxysulfobetaine, and the critical micelle concentration is ≤0.5 g / L.

6. The environmentally friendly drag reducer for fracturing according to claim 1, characterized in that: The deionized water contains 1-3 wt% of nano-silicon dioxide with a particle size of 10-20 nm.

7. A process for preparing the environmentally friendly drag reducer for fracturing according to claim 1, characterized in that: The steps include: S1. Dissolve the amphoteric surfactant in deionized water and stir at a constant temperature of 30-40°C for 1-1.5 hours to form a homogeneous solution; S2. To the above solution, hydrophobically modified cellulose and an organic zirconium crosslinker were sequentially added, and the pH was adjusted to 6.5-7.5 using a pH adjuster, and stirred at 200-400 rpm for 20-30 min; S3. After high-pressure homogenization at 20-40 MPa and aging at 55-65°C for 10-12 hours, an amber transparent colloid is obtained, which is an environmentally friendly drag reducer for fracturing.

8. Use of the environmentally friendly drag reducer for fracturing according to any one of claims 1 to 7 in oil production fracturing.

Images