Dry powder drag reducer for fracturing fluid and preparation method of dry powder drag reducer

Abstract

The invention relates to a dry powder drag reducer for fracturing fluid and a preparation method thereof, and belongs to the technical field of drag reducers. The dry powder drag reducer is subjected to copolymerization modification by preparing the polymerizable modifier, an aromatic ring and sulfonic acid ion structure is introduced into the dry powder drag reducer, the high temperature resistance and salt resistance of the dry powder drag reducer are effectively improved, in addition, the modified dry powder drag reducer structure further has a catechol structure, and the modified dry powder drag reducer has a good application prospect. The dry powder drag reducer can form stable five-membered ring boric acid ester with a boron cross-linking agent, when the boron drag reducer is used, the dry powder drag reducer can be mixed with a guar gum drag reducer for use, and the problem that the dry powder drag reducer is poor in sand carrying capacity is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of drag-reducing agent technology, specifically, it relates to a dry powder drag-reducing agent for fracturing fluid and its preparation method. Background Technology

[0002] Dry powder drag reducers, namely polyacrylamide drag reducers, have advantages such as high drag reduction efficiency, fast dissolution rate, minimal formation damage, high temperature and shear resistance, and convenient storage. They are currently the most commonly used drag reducers in fracturing fluids. However, because polyacrylamide drag reducers do not increase the viscosity of fracturing fluids, the fracturing fluid cannot effectively suspend the proppant, resulting in poor proppant carrying capacity. In existing technologies, polyacrylamide drag reducers and guar gum drag reducers are usually used alternately or in combination to improve the proppant carrying capacity of fracturing fluids. However, since guar gum drag reducers and polyacrylamide drag reducers use different crosslinking agents, when they are mixed, the crosslinking agent usually only interacts with one of the drag reducers, resulting in low crosslinking efficiency. To solve this problem, this invention provides a dry powder drag reducer for fracturing fluids and its preparation method by modifying polyacrylamide drag reducers. Summary of the Invention

[0003] The purpose of this invention is to provide a dry powder drag reducer for fracturing fluid and its preparation method, in order to solve the problems mentioned in the background art.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A method for preparing a dry powder drag-reducing agent for fracturing fluid includes the following steps:

[0006] The first step is to react dopamine with acrylic acid via an amidation reaction to obtain the modifier precursor.

[0007] The amidation reaction process is as follows: Dopamine hydrochloride, acrylic acid, N-hydroxysuccinimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, and deionized water are mixed in a reaction vessel and stirred until completely dissolved. The pH of the system is then adjusted to 4-5, and the reaction is carried out at room temperature for 24-48 hours. After the reaction is completed, the mixture is extracted with ethyl acetate, the organic phase is separated, washed with saturated sodium bicarbonate solution, dried, and then the solvent is removed by rotary evaporation to obtain the modifier precursor.

[0008] The second step is to sulfonate the modifier precursor to obtain the modifier.

[0009] The sulfonation reaction process is as follows: The modifier precursor and concentrated sulfuric acid are mixed in a reaction vessel equipped with a thermometer and a reflux condenser, and reacted at a temperature of 70-90℃ for 1-2 hours. After the reaction is completed, the mixture is cooled to room temperature and barium carbonate is added to the reaction solution until no more bubbles are generated. The solid is then filtered off, and the remaining filtrate is dried to obtain the modifier.

[0010] The third step involves polymerizing the modifier, acrylate, and acrylamide under the action of an initiator, followed by granulation, drying, and sieving of the polymerized product to obtain the dry powder drag reducer.

[0011] The polymerization process is as follows: The modifier, acrylate, acrylamide and water are mixed in a reaction vessel and stirred until completely dissolved. The pH of the system is then adjusted to 7-8. An initiator is then added to the system and allowed to stand for 2-4 hours to obtain the polymerization product. The polymerization product is then granulated, dried and sieved to obtain a dry powder drag reducer.

[0012] Furthermore, the initiator is composed of persulfate and sodium bisulfite mixed in a mass ratio of 0.4-1:0.7-1.2, wherein the persulfate is at least one of sodium persulfate, potassium persulfate, and ammonium persulfate.

[0013] Furthermore, the acrylate is at least one of sodium acrylate and potassium acrylate.

[0014] Furthermore, the mass fraction ratio of dopamine hydrochloride, acrylic acid, N-hydroxysuccinimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, and deionized water used in the first step is 4.6–7.3:1.8–2.9:1.08–1.74:2.52–4.06:90–150.

[0015] Furthermore, the concentrated sulfuric acid used in the second step has a mass fraction of 98%, and the mass fraction ratio of the modifier precursor to the concentrated sulfuric acid is 3.2–5.4:9–15.

[0016] Furthermore, the mass ratio of the modifier, acrylate, acrylamide, water, and initiator used in the third step is 3–5:20–25:100–120:350–450:0.08–0.12.

[0017] The present invention also provides a dry powder drag reducer for fracturing fluid prepared by the above preparation method.

[0018] The beneficial effects of this invention are:

[0019] 1) This invention prepares a modifier with polymerizable double bonds, sulfonic acid groups, and catechol structure in the molecule, and uses the modifier to copolymerize and modify polyacrylamide. The modifier of this invention can introduce sulfonic acid structure and aromatic ring structure into polyacrylamide, which effectively improves the salt resistance and high temperature resistance of polyacrylamide dry powder drag-reducing agent.

[0020] 2) This invention introduces a catechol structure into polyacrylamide-based dry powder drag reducers through copolymerization modification. The catechol structure can form a very stable five-membered ring borate ester with the boron-based crosslinking agent used in guar gum-based liquid drag reducers. This effectively solves the compatibility defects that exist when polyacrylamide-based dry powder drag reducers and guar gum-based liquid drag reducers are mixed. It allows the boron-based crosslinking agent to crosslink both guar gum-based liquid drag reducers and polyacrylamide-based dry powder drag reducers simultaneously, forming a dense and uniform crosslinked network structure. This significantly improves the overall performance of fracturing fluids using a mixture of polyacrylamide-based dry powder drag reducers and guar gum-based liquid drag reducers. Attached Figure Description

[0021] Figure 1 The graph shows the retention viscosity test results of the fracturing fluid prepared with the dry powder drag reducer obtained in Examples 1-3 and Comparative Example 1.

[0022] Figure 2 The figures show the viscosity test results of the fracturing fluid prepared with the dry powder drag reducer obtained in Examples 1-3 and Comparative Example 1. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] The raw materials used in this invention are not particularly restricted in terms of their source; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0025] The room temperature was 25±5℃.

[0026] Example 1

[0027] A method for preparing a dry powder drag-reducing agent for fracturing fluid includes the following steps:

[0028] Step 1: By mass, 4.6 parts of dopamine hydrochloride, 1.8 parts of acrylic acid, 1.08 parts of N-hydroxysuccinimide, 2.52 parts of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, and 90 parts of deionized water were mixed in a reaction vessel and stirred until completely dissolved. The pH of the system was then adjusted to 4, and the reaction was stirred at room temperature for 24 hours. After the reaction was completed, the mixture was extracted with ethyl acetate, and the organic phase was separated. The organic phase was then washed with saturated sodium bicarbonate solution and dried. The solvent was then removed by rotary evaporation to obtain the modifier precursor.

[0029] Step 2: According to the mass fraction, 3.2 parts of the modifier precursor and 9 parts of 98% concentrated sulfuric acid are mixed in a reaction vessel equipped with a thermometer and a reflux condenser, and reacted at 70°C for 2 hours. After the reaction is completed, the mixture is cooled to room temperature and barium carbonate is added to the reaction solution until no more bubbles are generated. Then the solid is filtered off, and the remaining filtrate is dried to obtain the modifier.

[0030] Third step: According to the mass fraction, mix 3 parts modifier, 20 parts sodium acrylate, 100 parts acrylamide and 350 parts water in a reaction vessel, stir until completely dissolved, adjust the pH of the system to 7, add 0.08 parts initiator to the system, let it stand for 2 hours to obtain the polymerization product, then granulate, dry and sieve the polymerization product to obtain dry powder drag reducer.

[0031] In this embodiment, the initiator is a mixture of sodium persulfate and sodium bisulfite in a mass ratio of 1:1.2.

[0032] A dry powder drag reducer for fracturing fluid is prepared by the above preparation steps.

[0033] Example 2

[0034] A method for preparing a dry powder drag-reducing agent for fracturing fluid includes the following steps:

[0035] Step 1: According to the mass fractions, 5.95 parts of dopamine hydrochloride, 2.35 parts of acrylic acid, 1.41 parts of N-hydroxysuccinimide, 3.29 parts of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, and 120 parts of deionized water were mixed in a reaction vessel and stirred until completely dissolved. The pH of the system was then adjusted to 4.5, and the reaction was stirred at room temperature for 36 hours. After the reaction was completed, the mixture was extracted with ethyl acetate, and the organic phase was separated. The organic phase was then washed with saturated sodium bicarbonate solution and dried. The solvent was then removed by rotary evaporation to obtain the modifier precursor.

[0036] Step 2: According to the mass fraction, 4.8 parts of the modifier precursor and 12 parts of 98% concentrated sulfuric acid are mixed in a reaction vessel equipped with a thermometer and a reflux condenser, and reacted at 80°C for 1.5 hours. After the reaction is completed, the mixture is cooled to room temperature and barium carbonate is added to the reaction solution until no more bubbles are generated. Then the solid is filtered off, and the remaining filtrate is dried to obtain the modifier.

[0037] Third step: According to the mass fraction, mix 4 parts modifier, 22.5 parts sodium acrylate, 110 parts acrylamide and 400 parts water in a reaction vessel, stir until completely dissolved, adjust the pH of the system to 7.5, add 0.1 parts initiator to the system, let it stand for 3 hours to obtain the polymerization product, then granulate, dry and sieve the polymerization product to obtain dry powder drag reducer.

[0038] In this embodiment, the initiator is composed of potassium persulfate and sodium bisulfite mixed in a mass ratio of 0.7:0.95.

[0039] A dry powder drag reducer for fracturing fluid is prepared by the above preparation steps.

[0040] Example 3

[0041] A method for preparing a dry powder drag-reducing agent for fracturing fluid includes the following steps:

[0042] Step 1: According to the mass fractions, 7.3 parts of dopamine hydrochloride, 2.9 parts of acrylic acid, 1.74 parts of N-hydroxysuccinimide, 4.06 parts of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, and 150 parts of deionized water were mixed in a reaction vessel and stirred until completely dissolved. The pH of the system was then adjusted to 5, and the reaction was stirred at room temperature for 48 hours. After the reaction was completed, the mixture was extracted with ethyl acetate, the organic phase was separated, washed with saturated sodium bicarbonate solution, dried, and then the solvent was removed by rotary evaporation to obtain the modifier precursor.

[0043] Step 2: According to the mass fraction, 5.4 parts of the modifier precursor and 15 parts of 98% concentrated sulfuric acid are mixed in a reaction vessel equipped with a thermometer and a reflux condenser, and reacted at 90°C for 2 hours. After the reaction is completed, the mixture is cooled to room temperature and barium carbonate is added to the reaction solution until no more bubbles are generated. Then the solid is filtered off, and the remaining filtrate is dried to obtain the modifier.

[0044] Third step: According to the mass fraction, mix 5 parts modifier, 25 parts potassium acrylate, 120 parts acrylamide and 450 parts water in a reaction vessel, stir until completely dissolved, adjust the pH of the system to 8, add 0.12 parts initiator to the system, let it stand for 4 hours to obtain the polymerization product, then granulate, dry and sieve the polymerization product to obtain dry powder drag reducer.

[0045] In this embodiment, the initiator is a mixture of ammonium persulfate and sodium bisulfite in a mass ratio of 0.4:0.7.

[0046] A dry powder drag reducer for fracturing fluid is prepared by the above preparation steps.

[0047] Comparative Example 1

[0048] A method for preparing a dry powder drag-reducing agent for fracturing fluid includes the following steps:

[0049] By mass, 20 parts sodium acrylate, 100 parts acrylamide, and 350 parts water were mixed in a reaction vessel and stirred until completely dissolved. The pH of the system was then adjusted to 7, and 0.08 parts initiator were added to the system. The reaction was allowed to stand for 2 hours to obtain the polymerization product. The polymerization product was then granulated, dried, and sieved to obtain a dry powder drag reducer.

[0050] In this embodiment, the initiator is a mixture of sodium persulfate and sodium bisulfite in a mass ratio of 1:1.2.

[0051] A dry powder drag reducer for fracturing fluid is prepared by the above preparation steps.

[0052] Experimental Example 1

[0053] Fracturing fluids were prepared using the dry powder drag reducer obtained in Examples 1-3 and Comparative Example 1. The pH of the fracturing fluid was 10. The mass fractions of each raw material were as follows: 0.2% dry powder drag reducer, 0.3% guar gum powder, 0.1% borax crosslinking agent, and the balance being water. A fracturing fluid without the dry powder drag reducer was set up as a blank control. The fracturing fluids of each component were then placed in water baths at temperatures of 60°C and 90°C, respectively, and incubated for 170 seconds. －1 Under shear conditions for 120 min, the retention viscosity of each component of the fracturing fluid was tested using a rheometer. The test results are shown in [Figure number missing]. Figure 1 :

[0054] Experiment Example 2

[0055] Fracturing fluid was prepared using the dry powder drag reducer obtained in Examples 1-3 and Comparative Example 1. The pH of the fracturing fluid was 10. The mass fractions of each raw material were as follows: 0.5% dry powder drag reducer, 0.1% crosslinking agent (borax in Examples 1-3, aluminum citrate in Comparative Example 1), and the balance being high-hardness water (total salinity > 20000 ppm). After continuous stirring for 3 minutes, the viscosity of each component of the fracturing fluid was tested using a rheometer. The test results are shown in [Figure 1]. Figure 2 :

[0056] As can be seen from Examples 1 and 2, the dry powder drag reducer of the present invention not only has good salt resistance, but can also crosslink with guar gum drag reducers to obtain better sand carrying capacity. In addition, after the dry powder drag reducer and guar gum drag reducer crosslink with each other under the action of boron-based crosslinking agent, the temperature resistance of guar gum drag reducers can also be improved.

[0057] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a dry powder drag-reducing agent for fracturing fluid, characterized in that, Includes the following steps: Step 1: Dopamine is reacted with acrylic acid via an amidation reaction to obtain the modifier precursor; The second step is to sulfonate the modifier precursor to obtain the modifier; The third step involves polymerizing the modifier, acrylate, and acrylamide under the action of an initiator, followed by granulation, drying, and sieving of the polymerized product to obtain the dry powder drag reducer.

2. The method for preparing a dry powder drag-reducing agent for fracturing fluid according to claim 1, characterized in that, The initiator is a mixture of persulfate and sodium bisulfite in a mass ratio of 0.4-1:0.7-1.2, wherein the persulfate is at least one of sodium persulfate, potassium persulfate, and ammonium persulfate.

3. The method for preparing a dry powder drag-reducing agent for fracturing fluid according to claim 1, characterized in that, The acrylate is at least one of sodium acrylate and potassium acrylate.

4. The method for preparing a dry powder drag-reducing agent for fracturing fluid according to claim 1, characterized in that, The amidation reaction process is as follows: Dopamine hydrochloride, acrylic acid, N-hydroxysuccinimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, and deionized water were mixed in a reaction vessel and stirred until completely dissolved. The pH of the system was then adjusted to 4-5, and the reaction was carried out at room temperature for 24-48 hours.

5. The method for preparing a dry powder drag-reducing agent for fracturing fluid according to claim 1, characterized in that, The sulfonation process is as follows: The modifier precursor and concentrated sulfuric acid were mixed in a reaction vessel equipped with a thermometer and a reflux condenser, and reacted at a temperature of 70–90°C for 1–2 hours.

6. The method for preparing a dry powder drag-reducing agent for fracturing fluid according to claim 1, characterized in that, The polymerization process is as follows: Mix the modifier, acrylate, acrylamide, and water in a reaction vessel and stir until completely dissolved. Adjust the pH of the system to 7-8, then add an aqueous solution of the initiator to the system and let it stand for 2-4 hours.

7. The method for preparing a dry powder drag-reducing agent for fracturing fluid according to claim 1, characterized in that, The mass fraction ratio of dopamine hydrochloride, acrylic acid, N-hydroxysuccinimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, and deionized water used in the first step is 4.6–7.3:1.8–2.9:1.08–1.74:2.52–4.06:90–150.

8. The method for preparing a dry powder drag-reducing agent for fracturing fluid according to claim 1, characterized in that, The concentrated sulfuric acid used in the second step has a mass fraction of 98%, and the mass ratio of the modifier precursor to the concentrated sulfuric acid is 3.2–5.4:9–15.

9. The method for preparing a dry powder drag-reducing agent for fracturing fluid according to claim 1, characterized in that, The mass fraction ratio of the modifier, acrylate, acrylamide, water, and initiator used in the third step is 3-5:20-25:100-120:350-450:0.08-0.

12.

10. The dry powder drag reducer for fracturing fluid obtained by the preparation method of claim 1.

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