Fiber water-based dispersion system, method for preparing same, and use thereof

Abstract

The application discloses a fiber water-based dispersion system and a preparation method and application thereof. The dispersion agent for fracturing fluid provided by the application has a general formula shown in formula I. The application provides a preparation method of the dispersion agent, which comprises the following steps: after amino acid is protected by amino and carboxyl, a sulfonic acidization reaction is performed, and deprotection is performed to obtain sulfonated amino acid. The application uses a small-molecule natural amino acid with good biodegradability and low environmental toxicity as a dispersion agent, and uses a composite reagent of sulfur trioxide and an organic base to introduce a sulfonic acid group to the side chain of the amino acid in a mild, controllable and low-toxicity manner, so that good dispersibility of fibers in a hydraulic fracturing process is achieved. Meanwhile, the space steric hindrance of the natural amino acid enables the water-based dispersion system to use a smaller amount of a polymer as a stabilizer compared with a traditional system.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology, specifically relating to a novel fiber-based water dispersion system, its preparation method, and its application. Background Technology

[0002] In the extraction of oil and natural gas reservoirs, hydraulic fracturing technology is often used. This technique utilizes hydraulic force to create fractures in the oil and gas reservoir, hence the name hydraulic fracturing. Traditional hydraulic fracturing aims to create highly conductive channels by uniformly distributing proppant within the fractures. However, conventional fracturing fluids suffer from limitations such as limited proppant transport distance and low fracture filling efficiency.

[0003] To address these challenges, some researchers have attempted to add fibers to fracturing fluids to improve proppant distribution efficiency in fractures. Currently used fibers are typically ordinary industrial fibers (such as polypropylene and polyester fibers), which often exhibit problems such as easy fiber agglomeration and entanglement, or floating on the fracturing fluid surface without effective dispersion. Furthermore, fibers are even more difficult to disperse uniformly in low-viscosity fracturing fluids such as slickwater, leading to pipeline blockage and hindering proppant delivery.

[0004] To improve the dispersibility of fibers in fracturing fluids, current methods primarily focus on two aspects: fiber material modification and specialized dispersion and injection equipment. Fiber modification technology uses coupling agents, hydrophilic oil agents, and other materials to treat the fiber surface, enhancing its hydrophilicity and thus improving its dispersibility in water. While this method can improve fiber dispersion to some extent, the modification process needs to be completed in advance at the factory, making the entire process more complex and increasing fiber costs. Furthermore, the stability of this modification method in high-temperature, high-mineralization formations needs further improvement. Commonly used dispersion equipment utilizes various physical dispersion methods such as centrifugal dispersion, physical agitation, wind pressure expansion, and water flow dispersion to improve fiber dispersion during injection and prevent the addition of whole fiber clumps. However, this method still cannot fundamentally solve the problem of fiber agglomeration in fracturing fluids.

[0005] Therefore, it is necessary to develop a new type of high-temperature resistant fiber dispersant for fracturing to improve the dispersion effect of fibers in fracturing fluid under high temperature conditions. Summary of the Invention

[0006] The purpose of this invention is to provide a novel fiber-based water dispersion system that can effectively improve the dispersion effect of fibers in fracturing fluid under high temperature conditions.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides a dispersant for fracturing fluids, wherein the dispersant is an amino acid with a sulfonic acid group as a side chain; the dispersant is an amino acid with a -NH group as a side chain. 3+ and -COO - It exists in zwitterionic form.

[0009] The amino acid is selected from one or more of lysine, serine, threonine, and tyrosine.

[0010] Secondly, the present invention provides a method for preparing the above-mentioned dispersant, comprising the following steps: subjecting an amino group to amino protection, a carboxyl group to carboxyl protection, a sulfonation reaction, and deprotection to obtain a sulfonated amino acid.

[0011] The sulfonating agent used in the sulfonation reaction is a complex obtained by mixing sulfur trioxide and an organic base; The mass ratio of the amino acid to the sulfonating agent is 1:(2-3). In the sulfonating agent, the mass ratio of sulfur trioxide to organic base is 1:(0.9-1.5). The organic base is selected from pyridine and / or triethylamine; The sulfonation reaction process is as follows: under the protection of inert nitrogen gas and under ice-water bath conditions, amino acids with protected amino and carboxyl groups are dissolved in an aprotic solvent, and sulfonation reagents are slowly added in batches, while the temperature is increased and the mixture is stirred to carry out the sulfonation reaction. The aprotic solvent is one or more of dichloromethane, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, 1,4-dioxane, acetonitrile, acetone, toluene, and carbon tetrachloride; The conditions for the sulfonation reaction are: temperature 10-60℃, time 4-12h.

[0012] The amino protecting agent used for amino protection is tert-butyloxycarbonyl; the conditions for amino protection are: temperature 0℃, time 12h; The carboxyl protecting agent used for the carboxyl protection is methanol; the conditions for the carboxyl protection are: heating under reflux for 4 hours with concentrated sulfuric acid as the catalyst.

[0013] Thirdly, the present invention provides a fiber-based water-based dispersion system for fracturing fluid, comprising the following components: a dispersant; wherein the dispersant is the aforementioned dispersant.

[0014] The fiber-based water-based dispersion system also includes a polymeric stabilizer; The polymeric stabilizer is one or more of polyacrylamide, xanthan gum, and cellulose derivatives; the polymeric stabilizer is adsorbed on the fiber surface, increasing the steric hindrance of the fiber and reducing the occurrence of aggregation.

[0015] The mass ratio of the dispersant to the polymeric stabilizer is 1:(0.9-1.1).

[0016] Fourthly, the present invention provides a fracturing fluid comprising the following components: fibers, proppant, water, and a fiber dispersion; wherein the fiber dispersion is the aforementioned water-based fiber dispersion system.

[0017] In the fracturing fluid, the mass fraction of the fiber is 0.01-0.5%, the mass fraction of the proppant is 1%-40%, and the mass fraction of the fiber dispersion is 0.05%-0.5%.

[0018] The fiber is one or more of the following: polypropylene fiber, polyester fiber, polyamide fiber, polyvinyl alcohol fiber, basalt fiber, and polylactic acid fiber.

[0019] In this invention, natural amino acids, using their own side chains (hydroxyl, amino, etc.), act as nucleophiles to undergo nucleophilic substitution with complexes of sulfur trioxide and organic bases in aprotic solutions (such as tetrahydrofuran, dichloromethane, etc.), thereby introducing sulfonic acid groups (-SO3). - This improves the heat resistance and electrostatic repulsion of amino acids; while also considering -NH 3+ To enhance the adsorption strength of amino acids on the fiber surface and maintain the amphiphilicity of amino acids (positive charge (-NH4+)). 3+ ), negative charge (-COO) - When sulfonating amino acids, amino and carboxyl protecting agents are used.

[0020] (1) The sulfonation reaction mechanism with an amino side chain is as follows: R 1 -CH(NH-PG 1 )-COO-PG 2 +SO3·Py→R 1 -CH(NH-PG 1 )-COO-PG 2 +Pyridine in: R 1 The derivatives are -CH2OSO3H (serine), -CH(CH3)OSO3H (threonine), and -CH2-C6H4-OSO3H (tyrosine). SO3·Py is a composite reagent of sulfur trioxide and organic base; PG 1 It is an amino protecting group; PG 2 It is a carboxyl protecting group.

[0021] (2) The sulfonation reaction mechanism with hydroxyl side chains is as follows: R3 -CH(NH-PG 1 )-COO-PG 2 +SO3·Py→R 3 -CH(NH-PG 1 )-COO-PG 2 +Pyridine in: R 3 -(CH2)4-NHSO3H (lysine); SO3·Py is a composite reagent of sulfur trioxide and organic base; PG 1 It is an amino protecting group; PG 2 It is a carboxyl protecting group.

[0022] In one specific embodiment of the present invention, the sulfonated amino acid is prepared according to the following steps: In an inert gas environment, using di-tert-butyl dicarbonate and methanol as protecting agents for the amino and carboxyl groups, respectively, the amino and carboxyl-protected amino acids were completely dissolved in an aprotic solution at 0°C. A sulfonating agent, a complex of sulfur trioxide and an organic base, was slowly added, maintaining a mass ratio of amino acids to the sulfur trioxide and organic base complex of 1:(2-3). The reaction temperature was maintained at 10-60°C, and after stirring for 4-12 hours, the temperature was quenched to 0°C to complete the reaction. The product was extracted with dichloromethane, washed with brine, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain the crude sulfonated amino acid product. Importantly, all reagents and containers must be thoroughly dried before the reaction.

[0023] Furthermore, the obtained crude sulfonated amino acid product was subjected to a mild alkaline condition, with trifluoroacetic acid used to remove the amino protecting agent and lithium hydroxide solution used to remove the carboxyl protecting agent, ultimately yielding the sulfonated amino acid.

[0024] Compared with the prior art, the beneficial effects achieved by the present invention are: 1. This invention uses small-molecule natural amino acids with good biodegradability and low environmental toxicity as raw materials. It utilizes a complex formed by sulfur trioxide and an organic base to introduce mild, controllable, and low-toxicity sulfonic acid groups into the side chains of the amino acids, thus preparing amino acids with positively charged (-NH4+) groups. 3+ ) and negative charge (-COO) - Sulfonated amino acids exist in zwitterionic form. The resulting sulfonated amino acids can be used as dispersants, fixed to the fiber surface through electrostatic adsorption or hydrogen bonding. Their charge repulsion overcomes van der Waals attraction, thus effectively preventing fiber aggregation in fracturing fluid. Figure 1As shown; at the same time, due to the introduction of sulfonic acid groups, the obtained sulfonated amino acids can still maintain good dispersion performance even under high temperature conditions, thereby reducing the amount of polymeric stabilizers used in the fiber water-based dispersion system.

[0025] 2. The sulfonated amino acids provided by this invention can be further combined with a polymeric stabilizer to prepare a fiber-based water-based dispersion system, which can further reduce fiber aggregation by reducing surface energy, increasing electrostatic repulsion, and increasing steric hindrance. Attached Figure Description

[0026] Figure 1 This is the working principle of the fiber-based water dispersion system provided by the present invention.

[0027] Figure 2 This is a diagram showing the fiber dispersion effect of the fracturing fluid obtained in Example 3.

[0028] Figure 3 The image shows the fiber dispersion effect of the fracturing fluid obtained in Comparative Example 2.

[0029] Figure 4 This is a diagram showing the fiber dispersion effect of the fracturing fluid obtained in Example 3 under high temperature conditions.

[0030] Figure 5 The image shows the fiber dispersion effect of the fracturing fluid obtained in Comparative Example 1 under high temperature conditions. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0032] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0033] Unless otherwise specified, all reagents, materials, instruments, etc. used in the following examples are commercially available.

[0034] Example 1 This embodiment provides a method for preparing sulfonated serine (a dispersant), and the preparation steps are as follows: (1) Serine was selected as the raw material. Serine (1.05 g) was suspended in a mixture of 20 mL of dioxane and water (volume ratio 1:1). 2.1 mL of triethylamine was added and stirred until the serine was completely dissolved. After the temperature of the system was lowered to 0℃, 11 mM di-tert-butyl dicarbonate solution of dioxane was slowly added dropwise. The reaction was stirred overnight. The solvent was removed by vacuum evaporation and the residue was dissolved in 30 mL of ethyl acetate. The residue was washed with 1 M HCl and water, and finally the organic phase was dried with anhydrous sodium sulfate. After filtration, the solution was reduced under reduced pressure to obtain amino-protected serine (Boc-serine). (2) The product obtained above was dissolved in methanol, and the mixture was heated under reflux for 4 hours with concentrated sulfuric acid (0.5 mL) as a catalyst. After cooling to room temperature, the system was washed with saturated sodium bicarbonate solution to neutralize it. The methanol was removed by concentration under reduced pressure. The residue was dissolved in ethyl acetate, washed with water, and the organic phase was dried with anhydrous sodium sulfate to obtain serine (Boc-serine-methyl ester) with amino and carboxyl groups protected. (3) Under inert nitrogen atmosphere and ice-water bath (0°C) conditions, dissolve Boc-serine-methyl ester in dichloromethane (20 mL) and slowly add 1.75 g of sulfur trioxide-pyridine complex in portions while stirring. After the addition is complete, allow the reaction mixture to gradually rise to room temperature and continue stirring, or reflux at a certain temperature (e.g., 60°C) for several hours.

[0035] Post-processing: After the 12-hour reaction, the mixture was cooled in an ice-water bath, and the reaction was quenched by slowly adding a dilute acid solution or a specific quencher. After quenching, some solvent and pyridine were removed by rotary evaporation. The product was initially separated by adjusting the pH, extraction, precipitation, or dialysis. The final product was obtained as a solid by freeze-drying. Using a suitable deprotecting agent, the product was dissolved in 10 mL of dichloromethane, trifluoroacetic acid was added, and the mixture was stirred at room temperature for 1 hour. The product was then concentrated under reduced pressure to obtain the deprotected Boc protecting agent. For the removal of methyl esters, the above product was dissolved in a mixture of 20 mL of methanol and water (volume ratio 1:1), 240 mg of lithium hydroxide was added, and the mixture was stirred at room temperature for 2 hours. The pH was adjusted to 3-4 with 1 M HCl to remove the methyl esters from the protecting agent. The product was then concentrated under reduced pressure to obtain the final product, sulfonated serine, which is the dispersant.

[0036] Example 2 This embodiment provides a fiber-based water-based dispersion system, the preparation steps of which are as follows: Weigh 20g of the sulfonated serine dispersant prepared in Example 1 and add 20g of the stabilizer polyacrylamide. Continue stirring until completely mixed to obtain the final fiber water-based dispersion system.

[0037] Example 3 This embodiment provides a fracturing fluid, the preparation steps of which are as follows: Weigh 100g of water, then add 0.1g of the fiber-based water dispersion system prepared in Example 2, stir until completely mixed, then add 10g of proppant and 0.1g of polyamide fiber to finally obtain fracturing fluid.

[0038] Comparative Example 1 A fracturing fluid, which differs from Example 3 in that the dispersant in the fiber-based aqueous dispersion system is unsulfonated serine.

[0039] The preparation steps are as follows: Weigh 100g of water, then add 0.1g of fiber-based water dispersion system, stir until completely mixed, then add 10g of proppant and 0.1g of polyamide fiber to finally obtain fracturing fluid.

[0040] Comparative Example 2 A fracturing fluid, which differs from Example 3 in that the fiber-based water dispersion system is replaced with polyacrylamide.

[0041] Effect verification: 1. Fiber dispersibility test: The test method is as follows: Stir the fracturing fluid at a speed of 100 rad / min for 5 min. Observe the fiber dispersion in the fracturing fluid.

[0042] The experimental results are as follows: The fracturing fluid obtained in Example 3 was tested according to the above method, and the fiber dispersion results are as follows. Figure 2 As shown, the fibers can be evenly dispersed in the fracturing fluid, and from the top, the fibers can occupy most of the area of ​​the agitator.

[0043] The fracturing fluid obtained in Comparative Example 2 was tested according to the above method, and the fiber dispersion results are as follows. Figure 3 As shown, the fibers exhibited significant agglomeration, and viewed from the top, they occupied only a small portion of the stirrer's area. This demonstrates that the fiber-based water dispersion system provided by this invention can significantly improve the fiber dispersion effect.

[0044] 2. High-temperature stability test The test method is as follows: place the fracturing fluid in an 80℃ water bath, let it stand for 20 minutes, and then stir it at a speed of 100 rad / min for 5 minutes to observe the dispersion of the fiber in the fracturing fluid.

[0045] The experimental results are as follows: The fracturing fluid obtained in Example 3 was tested according to the above method, and the fiber dispersion results are as follows. Figure 4 As shown, even at 80℃, the fibers can still disperse rapidly and uniformly in the fracturing fluid, and from the top, the fibers occupy most of the agitator area. The fracturing fluid obtained in Comparative Example 1 was tested using the above method, and the fiber dispersion results are as follows. Figure 5 As shown, the fiber dispersion effect is significantly worse when affected by temperature. This indicates that the water-based fiber dispersion system provided by this invention can significantly improve the fiber dispersion effect in high-temperature environments.

[0046] 3. Comparison of the dosage of polymeric stabilizers Traditional fracturing fluids consist of proppant, water, and polymeric stabilizers. The amount of polymeric stabilizers used accounts for more than 0.1% of the total mass. When the stabilizer content is low, the dispersion effect is poor.

[0047] In the fracturing fluid obtained in Example 3 of this invention, the polymeric stabilizer polyacrylamide accounts for 50% of the total mass of the fiber-based water dispersion system. Calculations show that the polymeric stabilizer accounts for 0.05% of the total mass of the fracturing fluid prepared in Example 3. Comparison shows that using the dispersion system provided by this invention can effectively reduce the amount of polymeric stabilizer required.

[0048] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A dispersant for fracturing fluids, characterized in that, The dispersant is an amino acid with a sulfonic acid group on its side chain; The dispersant is in the form of -NH 3+ and -COO - It exists in zwitterionic form.

2. The dispersant according to claim 1, characterized in that, The amino acid is selected from one or more of lysine, serine, threonine, and tyrosine.

3. The method for preparing the dispersant according to claim 1 or 2, characterized in that, The process includes the following steps: amino acid is protected, carboxyl group is protected, sulfonated, and deprotected to obtain sulfonated amino acid.

4. The preparation method according to claim 3, characterized in that, The sulfonating agent used in the sulfonation reaction is a complex obtained by mixing sulfur trioxide and an organic base; The mass ratio of the amino acid to the sulfonating agent is 1:(2-3). In the sulfonating agent, the mass ratio of sulfur trioxide to organic base is 1:(0.9-1.5). The organic base is selected from pyridine and / or triethylamine; The sulfonation reaction process is as follows: under the protection of inert nitrogen gas and under ice-water bath conditions, amino acids with protected amino and carboxyl groups are dissolved in an aprotic solvent, and sulfonation reagents are slowly added in batches, while the temperature is increased and the mixture is stirred to carry out the sulfonation reaction. The aprotic solvent is one or more of dichloromethane, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, 1,4-dioxane, acetonitrile, acetone, toluene, and carbon tetrachloride; The conditions for the sulfonation reaction are: temperature 10-60℃, time 4-12h.

5. The preparation method according to claim 4, characterized in that, The amino protecting agent used in the amino protection is tert-butyloxycarbonyl; The carboxyl protecting agent used for the carboxyl protection is methanol.

6. A fiber-based water-based dispersion system for fracturing fluid, characterized in that, It includes the following components: dispersant; The dispersant is the dispersant according to claim 1 or 2, or the dispersant prepared by any one of the preparation methods in claims 3-5.

7. The fiber-based water-based dispersion system according to claim 6, characterized in that, The fiber-based water-based dispersion system also includes a polymeric stabilizer; The polymeric stabilizer is one or more of polyacrylamide, xanthan gum, and cellulose derivatives; The mass ratio of the dispersant to the polymeric stabilizer is 1:(0.9-1.1).

8. A fracturing fluid, characterized in that, It comprises the following components: fiber, support agent, water, and fiber dispersion; wherein the fiber dispersion is the water-based fiber dispersion system as described in claim 6 or 7.

9. The fracturing fluid according to claim 8, characterized in that, In the fracturing fluid, the mass fraction of the fiber is 0.01-0.5%, the mass fraction of the proppant is 1%-40%, and the mass fraction of the fiber dispersion is 0.05%-0.5%.

10. The fracturing fluid according to claim 9, characterized in that, The fiber is one or more of the following: polypropylene fiber, polyester fiber, polyamide fiber, polyvinyl alcohol fiber, basalt fiber, and polylactic acid fiber.

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