A viscosity reducing synergist, a viscosity reducer, and a method for treating high-viscosity wastewater from oil fracturing.

Abstract

This invention discloses a viscosity-reducing and enhancing agent, a viscosity reducer, and a method for treating high-viscosity wastewater from oil fracturing, belonging to the field of high-viscosity wastewater treatment from oil fracturing. It comprises 1000 parts of a dendritic polyamide-amine macromolecular compound; 0.1-200 parts of granular or powdered solid acid; and 65-3000 parts of ferrous salt. This invention uses a composition of dendritic polyamide-amine macromolecular compound, aminosulfonic acid, and ferrous salt as a viscosity-reducing and enhancing agent. It can effectively activate persulfate for oxidation at room temperature. The activation of persulfate by the activator of this invention can rapidly reduce the viscosity of fracturing fluid return wastewater, reducing it to near-viscosity within 3-10 minutes. Furthermore, the dosage of the activator is small, accounting for only 10-30% of the persulfate amount, making it more environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of oil fracturing high-viscosity wastewater treatment, and in particular, a viscosity reducing agent, a viscosity reducer, and a method for treating oil fracturing high-viscosity wastewater. Background Technology

[0002] In the process of oil, shale oil or shale gas extraction, in order to obtain more oil and gas, fracturing fluid is needed to fracture the rock formation to release the oil and gas. Fracturing flowback fluid wastewater usually contains a large amount of high molecular polymers such as polyacrylamide or guar gum, which makes the wastewater viscosity high and seriously affects the subsequent flocculation, sedimentation and other treatment processes. Therefore, it is necessary to first treat the fracturing fluid to reduce viscosity.

[0003] Advanced oxidation is a commonly used method for reducing the viscosity of fracturing fluids. Among these methods, persulfate oxidation is a popular choice due to its good stability and high efficiency. However, simply adding persulfate is not very effective; it requires high temperatures (e.g., >85℃) or low pH (e.g., pH <3.0) and a relatively long time (e.g., >2 hours) to achieve the desired viscosity reduction. Some metal ions, such as Fe... 2+ Cu 2+ Mn 2+ Ce 2+ Co 2+ Ag + These can be used as activators to significantly increase the viscosity reduction rate of high-viscosity fracturing fluids by persulfate under normal temperature and neutral conditions. However, besides Fe... 2+ Other metal ions are toxic heavy metal ions and are expensive, such as Fe. 2+ It is inexpensive and readily available, but requires a larger dosage and has slightly inferior treatment effect. (Fe) 2+ The dosage is usually 200-1000% of the persulfate. Summary of the Invention

[0004] To overcome the above-mentioned technical defects, the present invention provides a viscosity reducing and enhancing agent, a viscosity reducing agent, and a method for treating high-viscosity wastewater from oil fracturing, so as to solve the problems involved in the background art.

[0005] In a first aspect, the present invention provides a viscosity-reducing and synergistic agent, comprising, by weight parts:

[0006] 1000 parts of dendritic polyamide-amine macromolecular compound;

[0007] 0.1 to 200 parts of granular or powdered solid acid;

[0008] Ferrous salts: 65–3000 parts.

[0009] Preferably or optionally, the dendritic polyamide-amine macromolecular compound is a 0.5G to 2.0G dendritic macromolecular PAMAM synthesized with ethylenediamine as the core and methyl acrylate.

[0010] Preferably or optionally, the dendritic polyamide-amine macromolecular compound is a 1.0 G dendritic macromolecular PAMAM synthesized with ethylenediamine as the core and methyl acrylate.

[0011] Preferably or optionally, the method for preparing the 1.0G dendritic macromolecule PAMAM includes the following steps:

[0012] Add ethylenediamine to the reactor, start stirring, start cooling to lower the material to 0-5°C, and introduce nitrogen gas to remove oxygen;

[0013] Methyl acrylate was added under nitrogen protection and mixed evenly. Methanol solvent was added evenly over 25-30 minutes. The temperature was raised to 40°C and the mixture was stirred for 10-30 hours.

[0014] Then, after vacuum distillation of the product, methanol solvent is added to fully dissolve the vacuum distillation product.

[0015] Under nitrogen protection, ethylenediamine is added and the mixture is stirred at 30°C for 10–30 h. Then, the mixture is distilled under reduced pressure. The powder obtained after distillation is 1.0 G of dendritic macromolecule PAMAM.

[0016] Preferably or optionally, the granular or powdered solid acid is one or more of trichloroacetic acid, aminosulfonic acid, oxalic acid, tartaric acid, and citric acid.

[0017] Preferably or optionally, the ferrous salt is ferrous chloride, ferrous sulfate, ferrous ammonium sulfate, or ferrous nitrate.

[0018] Secondly, the present invention also provides a viscosity reducer for high-viscosity fracturing fluid wastewater, comprising, by weight parts:

[0019] Persulfate 4000–20000 parts;

[0020] 1000 parts of dendritic polyamide-amine macromolecular compound;

[0021] 0.1 to 200 parts of granular or powdered solid acid;

[0022] Ferrous salts: 65–3000 parts.

[0023] Preferably or optionally, the persulfate is one or more of potassium persulfate, sodium persulfate, and ammonium persulfate.

[0024] Preferably or optionally, the dendritic polyamide-amine macromolecular compound is a 1.0 G dendritic macromolecular PAMAM synthesized with ethylenediamine as the core and methyl acrylate.

[0025] Preferably or optionally, the granular or powdered solid acid is one or more of trichloroacetic acid, aminosulfonic acid, oxalic acid, tartaric acid, and citric acid.

[0026] Preferably or optionally, the ferrous salt is ferrous chloride, ferrous sulfate, ferrous ammonium sulfate, or ferrous nitrate.

[0027] Thirdly, the present invention also provides a method for treating high-viscosity oil fracturing wastewater based on the aforementioned viscosity-reducing and enhancing agent for high-viscosity fracturing fluid, comprising the following steps:

[0028] Take a certain amount of oilfield fracturing fluid wastewater, add 200 ppm of persulfate, stir evenly, then add 20-50 ppm of fracturing fluid high viscosity wastewater viscosity reducer and enhancer, and continue stirring until the viscosity drops below the desired value.

[0029] This invention relates to a viscosity reducing agent, a viscosity reducer, and a method for treating high-viscosity wastewater from oil fracturing. Compared with existing technologies, it has the following advantages: This invention uses a composition of dendritic polyamide-amine macromolecular compound, aminosulfonic acid, and ferrous salt as a viscosity reducing agent. It can effectively activate persulfate for oxidation at room temperature. The persulfate activated by the activator of this invention can quickly reduce the viscosity of fracturing fluid return wastewater, reducing the wastewater to a level with no significant viscosity within 3 to 10 minutes. Moreover, the dosage of ferrous salt is small, accounting for only 10 to 30% of the amount of persulfate, making it more environmentally friendly. Detailed Implementation

[0030] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention. Invention Overview

[0032] Advanced oxidation is a commonly used method for reducing the viscosity of fracturing fluids. Among these methods, persulfate oxidation is a popular choice due to its good stability and high efficiency. However, simply adding persulfate is not very effective; it requires high temperatures (e.g., >85℃) or low pH (e.g., pH <3.0) and a relatively long time (e.g., >2 hours) to achieve the desired viscosity reduction. Studies have found that certain metal ions, such as Fe... 2+ Cu 2+ Mn 2+ Ce2+ Co 2+ Ag + These can be used as activators to significantly increase the viscosity reduction rate of high-viscosity fracturing fluids by persulfate under normal temperature and neutral conditions. However, besides Fe... 2+ Other metal ions are toxic heavy metal ions and are expensive, such as Fe. 2+ It is inexpensive and readily available, but requires a larger dosage and has slightly inferior treatment effect. (Fe) 2+ The dosage is usually 200-1000% of the persulfate.

[0033] This invention uses a combination of dendritic polyamide-amine macromolecular compounds, granular or powdered solid acids, and ferrous salts as a viscosity-reducing and synergistic agent. The dendritic macromolecules in this invention contain highly active primary and tertiary amines, which can rapidly activate persulfate to generate strongly oxidizing sulfate free radicals (SO4). - The dendritic macromolecules of this invention have very high densities of primary and tertiary amines, which can effectively reduce the amount of activator required. Furthermore, the dendritic macromolecules of this invention possess excellent surface activity, enabling them to rapidly carry persulfate and sulfate free radicals (SO42-). - • It can be quickly dispersed into the interior of high-viscosity waste liquid and can quickly and effectively activate persulfate for oxidation at room temperature. The persulfate activated by the activator of this invention can quickly reduce the viscosity of fracturing fluid wastewater, and can reduce the viscosity of wastewater to zero within 3 to 10 minutes. Moreover, the amount of ferrous salt added is small, accounting for only 10 to 30% of the amount of persulfate, which is more green and environmentally friendly.

[0034] The dendritic polyamide-amine macromolecular compound is a 0.5G to 2.0G dendritic macromolecular PAM synthesized with ethylenediamine as the core and methyl acrylate; preferably, the dendritic polyamide-amine macromolecular compound is a 1.0G dendritic macromolecular PAM synthesized with ethylenediamine as the core and methyl acrylate, wherein the 1.0G dendritic macromolecular PAM has an amino group at its terminal, which can rapidly activate persulfate to generate a strong oxidizing sulfate radical (SO4). - ·), and can rapidly carry sulfate and sulfate free radicals (SO4). - •) Rapidly disperse into the interior of highly viscous waste liquid. However, the 0.5G dendritic macromolecular PAMAM has ester groups at the end, so it cannot activate persulfate; while the 2.0G dendritic macromolecular PAMAM has too large a molecular weight, making it difficult to penetrate the gaps between viscous molecules and disperse into the interior of highly viscous waste liquid.

[0035] The granular or powdered solid acid is primarily used to adjust the pH value of high-viscosity wastewater. Solid acids are chosen for storage and transportation after mixing with other solid components. The solid acid is a commercially available product and can be, but is not limited to, trichloroacetic acid, aminosulfonic acid, oxalic acid, tartaric acid, citric acid, etc. In this embodiment, the granular or powdered solid acid is preferably aminosulfonic acid. An aqueous solution of aminosulfonic acid has a strong acidity equivalent to hydrochloric acid and sulfuric acid, which can quickly provide acidic conditions to meet the requirements for the action of persulfate. Metal ions such as Fe... 2+ Cu 2+ Mn 2+ Ce 2+ Co 2+ Ag + These can be used as activators to significantly increase the viscosity reduction rate of high-viscosity fracturing fluids by persulfate under normal temperature and neutral conditions. However, besides Fe... 2+ Other metal ions are toxic heavy metal ions. Therefore, in this embodiment, the ferrous salt is selected as an activator to improve the oxidation capacity of persulfate. Specifically, the ferrous salt is ferrous chloride, ferrous sulfate, ferrous ammonium sulfate, and ferrous nitrate.

[0036] The present invention will be further described below with reference to the embodiments. The examples described are intended to explain the present invention and should not be construed as limiting the present invention.

[0037] Example 1

[0038] Preparation of a viscosity-reducing and enhancing agent for high-viscosity fracturing fluid wastewater: 100 kg of ethylenediamine was added to a reactor, stirring was started, and the temperature was lowered to 0–5 °C. Nitrogen gas was introduced for deoxygenation. Under nitrogen protection, 1100 kg of methyl acrylate was added and mixed thoroughly. Then, 1200 kg of methanol was added uniformly over 25–30 minutes. The temperature was raised to 40 °C, and the reaction was stirred for 20 hours. The product was then distilled under reduced pressure for 1 hour, followed by the addition of 700 kg of methanol to fully dissolve the product. Under nitrogen protection, 790 kg of ethylenediamine was added, and the reaction was stirred at 30 °C for 20 hours, followed by another 1 hour of reduced pressure distillation. The distilled product was then... 766kg The powder was weighed, 760g of the above powder was added, 10g of aminosulfonic acid was added and stirred thoroughly, and then 50g of ferrous sulfate was added and stirred for 1 hour to mix thoroughly, thus obtaining the viscosity reducer and enhancer A for high-viscosity fracturing fluid wastewater.

[0039] Example 2

[0040] Preparation of a viscosity-reducing and enhancing agent for high-viscosity fracturing fluid wastewater: 100 kg of ethylenediamine was added to a reactor, stirring was started, and the temperature was lowered to 0–5 °C. Nitrogen gas was introduced for deoxygenation. Under nitrogen protection, 1100 kg of methyl acrylate was added and mixed thoroughly. Then, 1200 kg of methanol was added uniformly over 25–30 minutes. The temperature was raised to 40 °C, and the reaction was stirred for 20 hours. The product was then distilled under reduced pressure for 1 hour, followed by the addition of 700 kg of methanol to fully dissolve the product. Under nitrogen protection, 790 kg of ethylenediamine was added, and the reaction was stirred at 30 °C for 20 hours, followed by another 1 hour of reduced pressure distillation. The distilled product was then... 766kg The powder was weighed out. 760g of the powder was added to 10k aminosulfonic acid and stirred thoroughly. Then 2000k ferrous sulfate was added and stirred for 1 hour to mix thoroughly, thus obtaining the viscosity reducer B for fracturing fluid high viscosity wastewater.

[0041] Example 3

[0042] Preparation of a viscosity-reducing and enhancing agent for high-viscosity fracturing fluid wastewater: 100 kg of ethylenediamine was added to a reactor, stirring was started, and the temperature was lowered to 0–5 °C. Nitrogen gas was introduced for deoxygenation. Under nitrogen protection, 1100 kg of methyl acrylate was added and mixed thoroughly. Then, 1200 kg of methanol was added uniformly over 25–30 minutes. The temperature was raised to 40 °C, and the reaction was stirred for 20 hours. The product was then distilled under reduced pressure for 1 hour, followed by the addition of 700 kg of methanol to fully dissolve the product. Under nitrogen protection, 790 kg of ethylenediamine was added, and the reaction was stirred at 30 °C for 20 hours, followed by another 1 hour of reduced pressure distillation. The distilled product was then... 766kg The powder was weighed, 760g of the above powder was added, 10g of aminosulfonic acid was added and stirred thoroughly, and then 200g of ferrous sulfate was added and stirred for 1 hour to mix thoroughly, thus obtaining the viscosity reducer and enhancer C for high viscosity fracturing fluid wastewater.

[0043] Example 4

[0044] Preparation of a viscosity-reducing and enhancing agent for high-viscosity fracturing fluid wastewater: 100 kg of ethylenediamine was added to a reactor, stirring was started, and the temperature was lowered to 0–5 °C. Nitrogen gas was introduced for deoxygenation. Under nitrogen protection, 1100 kg of methyl acrylate was added and mixed thoroughly. Then, 1200 kg of methanol was added uniformly over 25–30 minutes. The temperature was raised to 40 °C, and the reaction was stirred for 20 hours. The product was then distilled under reduced pressure for 1 hour, followed by the addition of 700 kg of methanol to fully dissolve the product. Under nitrogen protection, 790 kg of ethylenediamine was added, and the reaction was stirred at 30 °C for 20 hours, followed by another 1 hour of reduced pressure distillation. The distilled product was then... 766kg The powder was weighed, 760g of the above powder was added, 10g of aminosulfonic acid was added and stirred thoroughly, and then 600g of ferrous sulfate was added and stirred for 1 hour to mix thoroughly, thus obtaining the viscosity reducer D for fracturing fluid high viscosity wastewater.

[0045] Testing and Discussion

[0046] Method 1 for treating high-viscosity wastewater from oil fracturing: Prepare an aqueous solution with a viscosity of 3200 mPa·s using anionic polyacrylamide as high-viscosity test water A. Take nine 250 mL beakers, labeled Test #1, Test #2, Test #3, Test #4, Test #5, Test #6, Test #7, Test #8, and Test #9, and one 2 L beaker, labeled Test #10. Add 200 mL of high-viscosity test water A to each of the nine 250 mL beakers, and add 2 L of high-viscosity test water A to the 3 L beaker in Test #10. Then add 200 ppm of ammonium persulfate to each of the ten beakers and stir thoroughly. After stirring thoroughly, add... In Experiment #2, 50 ppm of viscosity-reducing synergist A for high-viscosity fracturing fluid wastewater was added; in Experiment #3, 50 ppm of viscosity-reducing synergist C for high-viscosity fracturing fluid wastewater was added; in Experiment #4, 50 ppm of viscosity-reducing synergist D for high-viscosity fracturing fluid wastewater was added; in Experiment #5, 20 ppm of viscosity-reducing synergist A for high-viscosity fracturing fluid wastewater was added; in Experiment #6, 500 ppm of ferrous sulfate was added; in Experiment #7, 1000 ppm of ferrous sulfate was added; in Experiment #8, 50 ppm of the dendritic macromolecules prepared in Example 1 of this invention was added; and in Experiment #9, no reagents were added as a blank control group.

[0047] Tests #1 to #9 were stirred at 300 RPM at room temperature using a mechanical mixer. Test #10 was placed in a water bath at 85°C and stirred at 300 RPM using a mechanical mixer. The viscosity was measured at regular intervals.

[0048]

[0049] As can be seen from the table above, this invention has an excellent viscosity-reducing effect, significantly reducing wastewater viscosity to below 15 mPa·s within 10 minutes at room temperature. While the effect is far superior to the control group, the dosage is also much lower than that of ferrous sulfate activator alone. Among the four agents A, B, C, and D for high-viscosity wastewater viscosity-reducing synergists, agent C is relatively better than the other three. Furthermore, comparative experiments #1 and #8 show that, at the same concentration, high-viscosity wastewater viscosity-reducing synergist A has a greater activation effect on persulfate than a single dendritic macromolecule.

[0050] Method 2 for treating high-viscosity wastewater from oil fracturing: High-viscosity wastewater from fracturing flowback fluid in a Daqing oilfield, after preliminary sedimentation to remove larger precipitates, is used as high-viscosity test water B, with a viscosity of 121.4 mPa·s. Nine 250 mL beakers are designated as Test #11, Test #12, Test #13, Test #14, Test #15, Test #16, Test #17, Test #18, and Test #19, and one 2 L beaker is designated as Test #20. 200 mL of high-viscosity test water B is added to each of the nine 250 mL beakers, and 2 L of high-viscosity test water B is added to the 3 L beaker in Test #20. Then, 200 ppm of ammonium persulfate is added to each of the ten beakers, and the mixture is thoroughly stirred. In Experiment #11, 50 ppm of viscosity-reducing synergist A for high-viscosity fracturing fluid wastewater was added; in Experiment #12, 50 ppm of viscosity-reducing synergist B for high-viscosity fracturing fluid wastewater was added; in Experiment #13, 50 ppm of viscosity-reducing synergist C for high-viscosity fracturing fluid wastewater was added; in Experiment #14, 50 ppm of viscosity-reducing synergist D for high-viscosity fracturing fluid wastewater was added; in Experiment #15, 20 ppm of viscosity-reducing synergist A for high-viscosity fracturing fluid wastewater was added; in Experiment #16, 500 ppm of ferrous sulfate was added; in Experiment #17, 1000 ppm of ferrous sulfate was added; in Experiment #18, 50 ppm of the dendritic macromolecules prepared in Example 1 of this invention was added; and in Experiment #19, no reagents were added as a blank control group.

[0051] Tests #11 to #19 were stirred at 300 RPM at room temperature using a mechanical mixer. Test #20 was placed in a water bath at 85°C and stirred at 300 RPM using a mechanical mixer. The viscosity was measured at regular intervals.

[0052]

[0053] The table above shows that, compared to laboratory-prepared high-viscosity wastewater, the fracturing flowback fluid retrieved from the Daqing site is relatively more difficult to treat, but the viscosity reduction trend is consistent. This invention still exhibits superior viscosity reduction compared to the other methods, with a dosage far lower than the control group and significantly lower than that of ferrous sulfate activator alone. Among the four high-viscosity wastewater viscosity reducing agents A, B, C, and D, A and C are relatively better than the other two. Furthermore, comparative experiments #11 and #18 show that, at the same concentration, high-viscosity wastewater viscosity reducing agent A has a greater activation effect on persulfate than a single dendritic macromolecule.

[0054] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. A viscosity-reducing and synergistic agent for high-viscosity fracturing fluid wastewater, characterized in that, Used to enhance the viscosity-reducing effect of persulfate oxidation; the viscosity-reducing synergist comprises, by weight parts: 1000 parts of dendritic polyamide-amine macromolecular compound; the dendritic polyamide-amine macromolecular compound is 1.0 G of dendritic macromolecular PAMAM synthesized with ethylenediamine as the core and methyl acrylate; 0.1 to 200 parts of granular or powdered solid acid; Ferrous salts: 65–3000 parts.

2. The viscosity-reducing and synergistic agent for high-viscosity fracturing fluid wastewater according to claim 1, characterized in that, The method for preparing the 1.0G dendritic macromolecule PAMAM includes the following steps: Add ethylenediamine to the reactor, start stirring, start cooling to lower the material to 0-5°C, and introduce nitrogen gas to remove oxygen; Methyl acrylate was added under nitrogen protection and mixed evenly. Then, methanol solvent was added evenly over 25-30 minutes. The temperature was raised to 40°C and the reaction was stirred for 10-30 hours. The product was then distilled under reduced pressure, and methanol solvent was added to fully dissolve the product. Under nitrogen protection, ethylenediamine is added and the mixture is stirred at 30°C for 10–30 h. Then, the mixture is distilled under reduced pressure, and the powder obtained after distillation is 1.0 G of dendritic macromolecule PAMAM.

3. The viscosity-reducing and synergistic agent for high-viscosity fracturing fluid wastewater according to claim 1, characterized in that, The granular or powdered solid acid is one or more of trichloroacetic acid, aminosulfonic acid, oxalic acid, tartaric acid, and citric acid.

4. The viscosity-reducing and synergistic agent for high-viscosity fracturing fluid wastewater according to claim 1, characterized in that, The ferrous salt is ferrous chloride, ferrous sulfate, ferrous ammonium sulfate, or ferrous nitrate.

5. A method for treating high-viscosity oilfield fracturing wastewater based on the viscosity-reducing and enhancing agent for high-viscosity fracturing fluid as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Take a certain amount of oilfield fracturing fluid wastewater, add 200 ppm of persulfate, stir evenly, then add 20-50 ppm of fracturing fluid high viscosity wastewater viscosity reducer and enhancer, and continue stirring until the viscosity drops below the desired value.

6. A viscosity reducer for high-viscosity fracturing fluid wastewater based on the synergist according to any one of claims 1 to 4, characterized in that, By weight, it includes: Persulfate 4000–20000 parts; 1000 parts of dendritic polyamide-amine macromolecular compound; the dendritic polyamide-amine macromolecular compound is 1.0 G of dendritic macromolecular PAMAM synthesized with ethylenediamine as the core and methyl acrylate; 0.1 to 200 parts of granular or powdered solid acid; Ferrous salts: 65–3000 parts.

7. The viscosity reducer for high-viscosity fracturing fluid wastewater according to claim 6, characterized in that, The persulfate is one or more of potassium persulfate, sodium persulfate, and ammonium persulfate.

Images