A clean and environmentally friendly self-degradable inverse emulsion polymer and a preparation method thereof

Abstract

This invention relates to the field of oil and gas field development, specifically to a clean and environmentally friendly self-degradable reverse emulsion polymer and its preparation method. The technical solution is as follows: a water-soluble monomer is dissolved in water to prepare an aqueous phase, and the pH of the aqueous phase is adjusted to neutral; an emulsifier is added to an environmentally friendly dispersant as a continuous phase; the aqueous phase and the continuous phase are mixed and stirred at high speed to form a reverse microemulsion; after nitrogen purging to remove oxygen, an initiator is slowly added to initiate polymerization, resulting in a clean and environmentally friendly self-degradable emulsion polymer. This invention uses reverse emulsion polymerization to prepare a clean and environmentally friendly self-degradable reverse emulsion polymer, achieving spontaneous gel breaking of polyacrylamide while reducing the use of solvent oil, making it cleaner and more environmentally friendly. The continuous phase uses a degradable ester compound, which can self-degrade into alcohols and acids. When used as a fracturing fluid, this helps the polymer break down and reduces the water-locking damage to the reservoir caused by external fluids.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development, specifically to a clean and environmentally friendly self-degradable reverse emulsion polymer and its preparation method. Background Technology

[0002] Reverse emulsion polymerization is one of the ideal methods for obtaining high molecular weight polymers, playing an irreplaceable role in the preparation and application of polymer materials. Droplet nucleation is the main mechanism of acrylamide reverse emulsion polymerization. Free radicals are formed by monomers at the oil-water interface, which diffuse and transfer into the reaction nucleus, encapsulating the polymerized hydrogel within an oily droplet to form a reverse emulsion.

[0003] In reverse emulsion polymerization, the quality of the emulsifier and oil phase directly affects the size of polymer particles and polymerization efficiency, thus impacting product quality. Application CN101805423A discloses a method for preparing a polyacrylamide nanosphere system. The method is characterized by the following steps: First, an oil-soluble solvent and emulsifier are mixed uniformly. An aqueous phase containing acrylamide monomers, a crosslinking agent, and an oxidant is added. After thorough stirring and deoxygenation by purging with N2, a reducing agent is added to the mixture to initiate the reaction. After the exothermic peak, the reaction continues for 0.5-2 hours. Second, an aqueous phase containing acrylamide monomers, a crosslinking agent, and an oxidant is added to the system. After thorough stirring and deoxygenation by purging with N2, a reducing agent is added to initiate the reaction. After the exothermic peak, a transparent or translucent polyacrylamide nanosphere system is obtained. The oil-soluble solvent used in this invention is gasoline, kerosene, diesel, white oil, paraffin wax, vegetable oil, toluene, cyclohexane, or isooctane. Oil-soluble solvents such as white oil are produced from fossil raw materials, and the consumption of raw materials is unavoidable, resulting in high costs. Due to the environmental damage caused by the large amount of oil-soluble solvents during use, the products are not environmentally friendly. Furthermore, the inverse emulsion polymer has an unsatisfactory gel breaking effect, and external fluids can cause water-locking damage to the reservoir.

[0004] In conclusion, continuously optimizing reverse emulsion polymerization and its preparation methods has become a key research direction for researchers in this field. Summary of the Invention

[0005] This invention provides a clean and environmentally friendly self-degradable reverse emulsion polymer and its preparation method, in order to solve the problems of environmental unfriendliness, difficulty in self-degradation, and water-locking damage in the prior art.

[0006] To achieve the objectives of this invention, the present invention provides the following technical solution: a clean and environmentally friendly self-degradable reverse emulsion polymer, comprising the following steps:

[0007] (1) Preparation of oil and aqueous phases:

[0008] Add 200-300 parts of the oil phase dispersion and 20-30 parts of the emulsifier to a beaker, and stir until they are completely mixed to obtain the oil phase for later use.

[0009] Dissolve 200-300 parts of the aqueous phase reactant in 200-400 parts of water under magnetic stirring. After mixing evenly, add 1-3 parts of 1% ammonium persulfate, adjust the pH to 8 using NaOH solution, add 1-3 parts of initiator and stir evenly. After cooling to room temperature, the aqueous phase is ready for use.

[0010] (2) Mix the aqueous phase and the oil phase, and stir at high speed to obtain a water-in-oil preemulsion;

[0011] (3) Pour the pre-emulsion into a flask, purge with nitrogen to remove oxygen, and control the system temperature at 10-18℃;

[0012] (4) Slowly add 0.5-1.5% of the initiator by mass of the aqueous phase reactant to carry out the polymerization reaction. The temperature of the system is 10-40℃. The reaction time is 4-6h. Add 3.5% of the phase inversion agent by mass of the total emulsion and stir evenly to obtain a self-degradable reverse emulsion thickener.

[0013] Furthermore, the above-mentioned oil phase dispersion is one or a mixture of two or more of methyl methacrylate, isoamyl butyrate, ethyl acetate, and methyl benzoate in any proportion.

[0014] Furthermore, the emulsifier mentioned above is one or a mixture of two or more of the following in any proportion: Span80, Span60, Tween80, Tween60, and OP-10.

[0015] Furthermore, the aqueous phase reaction monomers mentioned above are acrylamide (AM), acrylic acid (AA), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS), with a mass ratio of 13-17:5-8:2-5.

[0016] Furthermore, the aforementioned initiator is one or a mixture of two or more of ammonium persulfate, ascorbic acid, and sodium formaldehyde sulfoxylate in any proportion.

[0017] Furthermore, the aforementioned phase-transforming agent is one or a mixture of two or more of the nonionic surfactants OP-10, TX-10, Tween80, Tween60, and FC-4430 in any proportion.

[0018] The above preparation method yields a clean and environmentally friendly self-degradable reverse emulsion polymer.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. This invention uses ester compounds instead of traditional white oil as the oil phase dispersion phase and employs reverse emulsion polymerization to prepare a clean, environmentally friendly, self-degradable reverse emulsion polymer. This achieves spontaneous gel breaking of polyacrylamide and reduces the use of solvent oil. During the preparation process, nonionic surfactants are selected as the system phase inversion agents to improve the solubility of the emulsion and make the prepared product cleaner and more environmentally friendly.

[0021] 2. The continuous phase uses a biodegradable ester compound, which can self-degrade into alcohols and acids. When used as a fracturing fluid, it can help break down the polymer and effectively reduce the water-locking damage to the reservoir caused by external fluids. Attached Figure Description

[0022] Figure 1 The rheological properties at 90°C of this invention;

[0023] Figure 2 The rheological properties of this invention at 120°C;

[0024] Figure 3 The molecular weight of the GPC test degradation solution of this invention;

[0025] Figure 4 This is for particle size testing of the degradation solution of the present invention. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0027] This invention provides a clean and environmentally friendly self-degradable reverse emulsion polymer, comprising the following steps:

[0028] (1) Preparation of oil and aqueous phases:

[0029] Add 200-300 parts of oil phase dispersion and 20-30 parts of emulsifier to a beaker, stir until they are completely mixed to obtain the oil phase (ester continuous phase) for later use.

[0030] Dissolve 200-300 parts of the aqueous phase reactant in 200-400 parts of water under magnetic stirring. After mixing evenly, add 1-3 parts of 1% ammonium persulfate, adjust the pH to 8 using NaOH solution, add 1-3 parts of initiator and stir evenly. After cooling to room temperature, the aqueous phase is ready for use.

[0031] (2) Mix the aqueous phase and the oil phase, and stir at high speed to obtain a water-in-oil preemulsion. The preemulsion has a yogurt-like appearance and is evenly coated on the wall.

[0032] (3) Pour the pre-emulsion into a flask, purge with nitrogen to remove oxygen, and control the system temperature at 10-18℃;

[0033] (4) Slowly add 0.5-1.5% of the initiator by mass of the aqueous phase reactant to carry out the polymerization reaction. The temperature of the system is 10-40℃. The reaction time is 4-6h. Add 3.5% of the phase inversion agent by mass of the total emulsion and stir evenly to obtain a self-degradable reverse emulsion thickener.

[0034] All quantities mentioned in the following examples are by weight.

[0035] Example 1: A method for preparing a clean and environmentally friendly self-degradable reverse emulsion polymer, comprising the following steps:

[0036] (1) Preparation of oil and aqueous phases:

[0037] Dissolve 130 parts AM, 50 parts AA, and 20 parts AMPS in 200 parts water under magnetic stirring. After mixing evenly, add 1 part 1% ammonium persulfate and adjust the pH to 8 with 48% NaOH solution. After cooling to room temperature, the aqueous phase is obtained for later use.

[0038] 10 parts of Span80, 5 parts of Tween80, 5 parts of Span60, and 200 parts of isoamyl butyrate were mixed evenly under magnetic stirring to obtain the oil phase for later use.

[0039] (2) Mix the aqueous phase and oil phase and stir at high speed to obtain a reversed preemulsion.

[0040] (3) Pour the pre-emulsion into a flask equipped with a stirring vessel, thermometer, and nitrogen inlet, purge with nitrogen to remove oxygen, and control the system temperature at 10-18℃.

[0041] (4) Slowly add 0.5% of the initiator ascorbic acid solution of the aqueous phase reaction monomer to carry out the polymerization reaction. Control the temperature of the system at 30-40℃ and maintain the reaction for 6 hours. At this time, the temperature drops and the polymerization is completed. Add 3.5% of the phase inversion agent TX-10 of the total emulsion mass and stir evenly to obtain a clean and environmentally friendly self-degradable reverse emulsion polymer.

[0042] Example 2: A method for preparing a clean and environmentally friendly self-degradable reverse emulsion polymer, comprising the following steps:

[0043] (1) Preparation of oil and aqueous phases:

[0044] Dissolve 140 parts AM, 60 parts AA, and 30 parts AMPS in 240 parts water under magnetic stirring. After mixing the aqueous phase thoroughly, add 1.5 parts of 1% ammonium persulfate and adjust the pH to 8 using 48% NaOH solution. After cooling to room temperature, the aqueous phase is ready for use.

[0045] 10 parts of Span80, 7 parts of Tween80, 7 parts of Span60, and 240 parts of ester were mixed evenly under magnetic stirring to obtain the oil phase for later use.

[0046] (2) Mix the aqueous phase and oil phase and stir at high speed to obtain a reversed preemulsion.

[0047] (3) Pour the pre-emulsion into a flask equipped with a stirring vessel, thermometer, and nitrogen inlet, purge with nitrogen to remove oxygen, and control the system temperature at 10-18℃.

[0048] (4) Slowly add 0.5% of the initiator ascorbic acid solution of the aqueous phase reaction monomer to carry out the polymerization reaction. Control the temperature of the system at 30-40℃ and maintain the reaction for 4 hours. At this time, the temperature drops and the polymerization is completed. Add 3.5% of the phase inversion agent TX-10 according to the emulsion mass to obtain a clean and environmentally friendly self-degradable reverse emulsion polymer.

[0049] Example 3: A method for preparing a clean and environmentally friendly self-degradable reverse emulsion polymer, comprising the following steps:

[0050] (1) Preparation of oil and aqueous phases:

[0051] Dissolve 160 parts AM, 70 parts AA, and 40 parts AMPS in 300 parts water under magnetic stirring. After mixing the aqueous phase thoroughly, add 2 parts of 1% ammonium persulfate and adjust the pH to 8 using 48% NaOH solution. After cooling to room temperature, the aqueous phase is ready for use.

[0052] 20 parts of Span80, 4 parts of Tween80, 4 parts of Span60, and 280 parts of 8 ester were mixed evenly under magnetic stirring to obtain the oil phase for later use.

[0053] (2) Mix the aqueous phase and oil phase and stir at high speed to obtain a reversed preemulsion.

[0054] (3) Pour the pre-emulsion into a flask equipped with a stirring vessel, thermometer, and nitrogen inlet, purge with nitrogen to remove oxygen, and control the system temperature at 10-18℃.

[0055] (4) Slowly add 0.5% of the initiator ascorbic acid solution of the aqueous phase reaction monomer to carry out the polymerization reaction. Control the temperature of the system at 30-40℃ and maintain the reaction for 6 hours. At this time, the temperature drops and the polymerization is completed. Add 3.5% of the phase inversion agent TX-10 according to the emulsion mass and stir evenly to obtain a clean and environmentally friendly self-degradable reverse emulsion polymer.

[0056] Example 4: A method for preparing a clean and environmentally friendly self-degradable reverse emulsion polymer, comprising the following steps:

[0057] (1) Preparation of oil and aqueous phases:

[0058] Dissolve 170 parts AM, 80 parts AA, and 50 parts AMPS in 400 parts water under magnetic stirring. After mixing the aqueous phase thoroughly, add 3 parts of 1% ammonium persulfate and adjust the pH to 8 using 48% NaOH solution. After cooling to room temperature, the aqueous phase is ready for use.

[0059] 20 parts of Span80, 5 parts of Tween80, 5 parts of Span60, and 300 parts of ester were mixed evenly under magnetic stirring to obtain the oil phase for later use.

[0060] (2) Mix the aqueous phase and oil phase and stir at high speed to obtain a reversed preemulsion.

[0061] (3) Pour the pre-emulsion into a flask equipped with a stirring vessel, thermometer, and nitrogen inlet, purge with nitrogen to remove oxygen, and control the system temperature at 10-18℃.

[0062] (4) Slowly add 0.5% of the initiator ascorbic acid solution of the aqueous phase reaction monomer to carry out the polymerization reaction. Control the temperature of the system to below 40℃ and maintain the reaction for 6 hours. At this time, the temperature drops and the polymerization is completed. Add 3.5% of the phase inversion agent TX-10 according to the emulsion mass and stir evenly to obtain a clean and environmentally friendly self-degradable reverse emulsion polymer.

[0063] Performance testing

[0064] (1) Molecular weight test

[0065] Using 1 mol / L sodium chloride solution as a standard control, the time it took for the polymer solution to flow through an undiluted capillary viscometer was measured, and the intrinsic viscosity of the polymer [η] was calculated. The molecular weights of the polymers were obtained as shown in Table 1. The molecular weights of the synthesized polymers were all greater than 15 million, with the polymer obtained in Example 2 having the highest molecular weight and the best performance.

[0066] Table 1. Molecular weight of clean and environmentally friendly self-degradable reverse emulsion polymers

[0067]

[0068] (2) Rheological property testing

[0069] The product obtained in the preferred embodiment 2 was subjected to the following tests: A 1.0% clean and environmentally friendly self-degradable reverse emulsion polymer was prepared, and its temperature and shear resistance were tested. Figure 1 It can be seen that this fracturing fluid operates at a shear rate of 170 s⁻¹. -1 After shearing at 90℃ for 1 hour, the final viscosity is 92.45 mPa·s, and after shearing at 120℃ for 1 hour, the final viscosity is 75.92 mPa·s, demonstrating excellent temperature and shear resistance.

[0070] (3) Degradation performance

[0071] The product obtained in the best example 2 was subjected to the following tests: Preparation of degradation solution: A 0.5% clean and environmentally friendly self-degradable reverse emulsion polymer aqueous solution was prepared and placed at 30°C for 48 hours. The polymer can spontaneously degrade.

[0072] See Figure 3 As can be seen from the GPC test of the molecular weight of the degradation solution, the viscosity-average molecular weight of the degradation solution is around 35,000, indicating complete polymer breakdown. For the particle size of the degradation solution, please refer to [link / reference needed]. Figure 4 We can see that the average particle size is D50 = 825 nm.

[0073] (4) Evaluation of the waterproof lock effect

[0074] Simulated core samples were used to evaluate the water-locking effect of the clean and environmentally friendly self-degradable reverse emulsion according to the method of SY / T 6540-2002. The test results are shown in Table 2. The polymer of the synthesized clean and environmentally friendly self-degradable reverse emulsion showed high permeability and repair rate, all greater than 80%, indicating that the clean and environmentally friendly self-degradable reverse emulsion prepared in this invention can effectively reduce the water-locking damage to the reservoir caused by foreign fluids when used as a fracturing fluid.

[0075] Table 2. Waterproofing and locking effect test results of clean and environmentally friendly self-degradable reverse emulsions.

[0076] project Example 1 Example 2 Example 3 Example 4 Core number 1# 2# 3# 4# Damage fluid 2% KCl 2% KCl 2% KCl 2% KCl Permeability repair rate, % 80.26 85.68 89.27 88.38

[0077] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a clean, environmentally friendly, self-degradable reverse emulsion polymer, characterized in that, Includes the following steps: (1) Preparation of oil phase and aqueous phase: Add 200-300 parts of the oil phase dispersion and 20-30 parts of the emulsifier to a beaker, and stir until they are completely mixed to obtain the oil phase for later use. Dissolve 200-300 parts of the aqueous phase reactant in 200-400 parts of water under magnetic stirring. After mixing evenly, add 1-3 parts of 1% ammonium persulfate, adjust the pH to 8 using NaOH solution, add 1-3 parts of initiator and stir evenly. After cooling to room temperature, the aqueous phase is ready for use. (2) Mix the aqueous phase and the oil phase, and stir at high speed to obtain a water-in-oil preemulsion; (3) Pour the pre-emulsion into a flask, purge with nitrogen to remove oxygen, and control the system temperature at 10-18℃; (4) Slowly add 0.5-1.5% of the initiator by mass of the aqueous phase reactant to carry out the polymerization reaction. The temperature of the system is 10-40℃. The reaction time is 4-6h. Add 3.5% of the phase inversion agent by mass of the emulsion and stir evenly to obtain a self-degradable reverse emulsion thickener. The oil phase dispersed in step one is isoamyl butyrate; The aqueous phase reaction monomers in step (1) are acrylamide (AM), acrylic acid (AA) and 2-acrylamide-2-methylpropanesulfonic acid (AMPS), with a mass ratio of 13-17:5-8:2-5.

2. The method for preparing a clean and environmentally friendly self-degradable reverse emulsion polymer according to claim 1, characterized in that, The emulsifier in step (1) is one or a mixture of two or more of the following in any proportion: Span80, Span60, Tween80, Tween60, and OP-10.

3. The method for preparing a clean and environmentally friendly self-degradable reverse emulsion polymer according to claim 1, characterized in that, The initiator in step (1) is one or a mixture of two or more of ammonium persulfate, ascorbic acid, and sodium formaldehyde sulfoxylate in any proportion.

4. The method for preparing a clean and environmentally friendly self-degradable reverse emulsion polymer according to claim 1, characterized in that, The phase-transforming agent in step (4) is one or a mixture of two or more of the nonionic surfactants OP-10, TX-10, Tween80, Tween60, and FC-4430 in any proportion.

5. A clean and environmentally friendly self-degradable reverse emulsion polymer prepared by the preparation method according to claim 1.

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