Instant ternary copolymer emulsion type fracturing fluid thickening agent and preparation method thereof

Abstract

The application provides a quick-dissolving ternary copolymer emulsion type fracturing fluid thickening agent and a preparation method, and relates to the field of oil and gas exploitation. N,N,N'-trimethyl-N'-allyl ethylenediamine (TMPEMA) is prepared by reacting chloropropylene with N,N,N'-trimethyl ethylenediamine, and (N,N-dimethyl-N-ethyl-N'-allyl-N'-methyl-N'-ethyl)-ethyldibromide functional monomer is prepared by reacting TMPEMA with bromoethane. A monomer solution is prepared by using acrylamide, sodium p-styrene sulfonate and the functional monomer as an aqueous phase, using an emulsifier and liquid paraffin as an oil phase, slowly adding the aqueous phase into the oil phase, stirring uniformly under N2, and then adding an initiator drop by drop to perform inverse emulsion polymerization, so as to prepare the fracturing fluid thickening agent. The ternary copolymer fracturing fluid thickening agent has excellent viscosity increasing property, quick-dissolving capacity, salt resistance, temperature resistance and shear resistance. The prepared fracturing fluid has good viscoelasticity, gel breaking property, sand carrying property, filtration loss reducing property and the like, can be used as slick water at a low concentration and can be used as a sand carrying liquid at a high concentration, and has a good application prospect in offshore and shale oil and gas development.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fracturing fluid thickening agent system, and relates to a synthetic polymer fracturing fluid thickening agent and a preparation method. BACKGROUND

[0002] Fracturing technology is one of the main stimulation measures for oil and gas fields, and its purpose is to press the reservoir out of the cracks to increase production, and the performance of the fracturing fluid is directly related to the construction efficiency. With the continuous development of oil exploration technology, the development of oil and gas fields is continuously extended vertically, and the geological conditions of underground reservoirs are various, including porosity, permeability, rock type and other factors. Some formations may need to inject slick water in fracturing operations to reduce frictional resistance, while some formations may need to use sand-carrying fluid in fracturing operations to increase fracture stability. The existing fracturing fluid is usually composed of thickening agent, crosslinking agent, anti-swelling agent, bactericide and other additives, among which the thickening agent is the main additive of the fracturing fluid system, and the thickening agent can be divided into solid powder type and emulsion type. The solid powder type has problems such as the need for pre-liquid preparation construction, low construction efficiency, single function, and inability to meet the needs of different reservoir reconstruction environments at the same time. Chinese patent CN115703724A discloses a sulfonic acid compound and a fast-dissolving temperature-resistant and salt-resistant polyacrylamide for oil displacement and its preparation method and application, which improves the solubility of the polymer by introducing a sulfonic acid group and increases the molecular chain structure rigidity by introducing a benzene ring group, but the actual polyacrylamide dissolution time is still not ideal, which is more than 40 min at 20,000 mineralization degree and 80℃, and it is difficult to meet the needs of field application. Chinese patent CN109134752A discloses a fast-dissolving polyacrylamide for offshore oil displacement and its synthesis method, which is synthesized by using acrylamide and 2-acrylamido-2-methylpropanesulfonic acid as monomers, and the fast-dissolving effect is not ideal, which is slow at 32,000 mineralization degree and 85℃, and cannot meet the needs of field application. Therefore, it is urgent to develop a fracturing fluid thickening agent with good fast-dissolving effect, which can be flexibly adjusted in concentration under different geological conditions to meet the needs of offshore oil and gas fracturing operations and shale oil and gas fracturing operations. SUMMARY

[0003] In order to improve the fast-dissolving effect of the fracturing fluid thickening agent solution, save time and cost, and improve the operation efficiency, and make it have good viscoelasticity, salt resistance and temperature resistance, and gel breaking property, a new type of cationic monomer is first synthesized, and then a fast-dissolving ternary copolymer emulsion type fracturing fluid thickening agent is prepared by copolymerization of non-ionic monomer, cationic monomer and anionic monomer, so that it has excellent drag reduction performance at low concentration and can be used as slick water, and has excellent thickening performance at high concentration and can be used as sand-carrying fluid.

[0004] The invention discloses a kind of instant ternary copolymer emulsion type fracturing fluid thickening agent and preparation method, it is characterized in that, the fracturing fluid thickening agent is prepared by the following raw materials by inverse emulsion polymerization, the raw materials include by mass percentage:

[0005] Monomer: 10-20%;

[0006] Emulsifier: 2.0-4.0%;

[0007] Initiator: 0.02-0.05%;

[0008] Liquid paraffin: 50-60%;

[0009] The balance is deionized water.

[0010] Preferably, the instant ternary copolymer emulsion type fracturing fluid thickening agent is characterized in that the monomer is acrylamide, (N,N-dimethyl-N-ethyl-N'-allyl-N'-methyl-N'-ethyl)-ethyldibromide, sodium p-styrenesulfonate, and the mass ratio of the three is 10-14:2-3:0.008-0.1.

[0011] Preferably, the instant ternary copolymer emulsion type fracturing fluid thickening agent is characterized in that the emulsifier is Span-80, Tween-80, and the mass ratio of the two is 5:1.

[0012] Preferably, the instant ternary copolymer emulsion type fracturing fluid thickening agent is characterized in that the initiator is composed of ammonium persulfate and sodium sulfite, and the mass ratio of the two is 1:1.

[0013] Preferably, the instant ternary copolymer emulsion type fracturing fluid thickening agent is characterized in that the oil-water mass ratio is 5.5-6.0:4.5-4.0.

[0014] Preferably, the instant ternary copolymer emulsion type fracturing fluid thickening agent is characterized in that the monomer (N,N-dimethyl-N-ethyl-N'-allyl-N'-methyl-N'-ethyl)-ethyldibromide has the following structural formula: It is obtained by the reaction of N,N,N'-trimethyl-N'-allyl ethylenediamine (TMPEMA) and bromoethane; wherein TMPEMA is obtained by the reaction of chloropropylene and N,N,N'-trimethylethylenediamine under the catalysis of triethylamine base, and the reaction formula is as follows:

[0015]

[0016] Preferably, the instant ternary copolymer emulsion type fracturing fluid thickening agent is characterized in that the synthesis method of the monomer (N,N-dimethyl-N-ethyl-N'-allyl-N'-methyl-N'-ethyl)-ethyldibromide comprises the following steps:

[0017] S1. 0.11 mol of chloropropene and 0.10 mol of N,N,N'-trimethyl ethylenediamine are added to a round-bottom flask containing 100 mL of acetone, the solution is stirred uniformly using a magnetic stirrer, then 5 g of the basic catalyst triethylamine is added to the solution, the temperature is raised to 30°C, N2 is continuously introduced for 40 min, and rotary evaporation is performed at 45°C for 30 min, thereby obtaining the intermediate product N,N,N'-trimethyl-N'-allyl ethylenediamine (TMPEMA);

[0018] S2. 0.10 mol of TMPEMA is dissolved in 75 mL of anhydrous acetonitrile, 0.22 mol of bromoethane is added, transferred to a high-pressure reaction kettle, reacted at 60°C for 16 h, removed from the volatile substances by distillation under reduced pressure, washed with diethyl ether, and dried in a vacuum oven, thereby obtaining the monomer (N,N-dimethyl-N-ethyl-N'-allyl-N'-methyl-N'-ethyl)-ethyldibromide.

[0019] Preferably, the instant ternary copolymer emulsion type fracturing fluid thickening agent is characterized in that the synthesis method of the instant ternary copolymer emulsion type fracturing fluid thickening agent comprises the following steps:

[0020] S1. The emulsifier and liquid paraffin are stirred and mixed uniformly, thereby obtaining an oil phase;

[0021] S2. The monomers acrylamide, sodium p-styrenesulfonate, and (N,N-dimethyl-N-ethyl-N'-allyl-N'-methyl-N'-ethyl)-ethyldibromide are added to deionized water, stirred to completely dissolve, and the pH of the water phase is adjusted to 8 using a 2% sodium hydroxide solution, thereby obtaining a water phase;

[0022] S3. The oil phase is added to a three-necked flask, the water phase is slowly added to the oil phase at a speed of 500 revolutions per minute, and after the addition is completed, the emulsion is continuously stirred for 50 min, thereby obtaining a stable water-in-oil pre-emulsion;

[0023] S4. The three-necked flask is connected to nitrogen, a thermometer, and an initiator dropping tube, oxygen is removed by passing nitrogen for 15 min, the temperature is raised to 25-35°C, the initiator is slowly added, and the reaction time is 3-6 h, thereby obtaining the instant ternary copolymer emulsion type fracturing fluid thickening agent.

[0024] The instant ternary copolymer emulsion type fracturing fluid thickening agent has the following advantages:

[0025] (1) has good thermal stability at 120℃; (2) has good salt resistance, temperature resistance and shear resistance; (3) meets the required standards of SY / T 6376-2008 general technical conditions for fracturing fluid; (4) at low concentration, the drag reduction performance meets the performance index and evaluation method of NB / T 14003.1-2015 shale gas fracturing fluid part 1: slickwater, and can be used as slickwater; (5) at high concentration, the thickening performance meets the general technical conditions of SY / T 6376-2008 fracturing fluid, and can be used as sand-carrying fluid; (6) can meet the needs of fracturing operation under different geological conditions; (7) has excellent viscosity increasing property and rapid dissolving capacity, good viscoelasticity, salt resistance, temperature resistance and gel breaking property, and has a good application prospect in offshore oil and gas fracturing and shale oil and gas fracturing; (8) the emulsion type fracturing thickening agent has a fast dissolving time, which is 30-60min less than the dissolving time of a solid powder, saves the construction time, and improves the operation efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is the rheological curve of the fracturing fluid thickening agent solution of example 3 of the present application at 120℃;

[0027] Figure 2 is the influence of NaCl concentration on the fracturing fluid thickening agent solution of example 3 of the present application;

[0028] Figure 3 is the influence of CaCl2 concentration on the fracturing fluid thickening agent solution of example 3 of the present application;

[0029] Figure 4 is the drag reduction rate curve of the slickwater fracturing fluid system of example 3 of the present application;

[0030] Figure 5 is the static filtration curve of the fracturing fluid system of example 3 of the present application at 120℃. DETAILED DESCRIPTION

[0031] The present application is not limited by the following examples, and the specific implementation can be determined according to the technical scheme of the present application and the actual situation. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor belong to the scope of protection of the present application. The various chemical reagents and chemical supplies mentioned in the present application are well-known and commonly-used chemical reagents and chemical supplies in the prior art, unless otherwise specified.

[0032] Example 1

[0033] The synthesis experimental steps of the rapid-dissolving ternary copolymer emulsion type fracturing fluid thickening agent are as follows:

[0034] S1. 2.5g Span-80 emulsifier, 0.5g Tween-80 emulsifier and 52.0g liquid paraffin were stirred and mixed uniformly to obtain an oil phase;

[0035] S2. 12.0g acrylamide, 3.0g (N,N-dimethyl-N-ethyl-N'-allyl-N'-methyl-N'-ethyl)-ethyldibromide, 0.012g sodium p-styrenesulfonate were added to 29.988g deionized water, stirred to completely dissolve, and the water phase pH was adjusted to 8 with 2% sodium hydroxide solution to obtain a water phase;

[0036] S3. The oil phase was added to a three-necked flask, and the water phase was slowly added to the oil phase at a speed of 500 rpm, and after the addition was completed, the emulsion was stirred for 50 min to obtain a stable water-in-oil pre-emulsion;

[0037] S4. The three-necked flask was connected to nitrogen, a thermometer and an initiator dropping tube, nitrogen was passed for 15 min to remove oxygen, the temperature was raised to 30°C, 0.015g ammonium persulfate and 0.015g sodium sulfite were slowly added, the reaction time was 4h, and a quick-release ternary copolymer emulsion type fracturing fluid thickening agent was obtained.

[0038] Example 2

[0039] The synthesis experimental steps of a quick-release ternary copolymer emulsion type fracturing fluid thickening agent are as follows:

[0040] S1. 2.0g Span-80 emulsifier, 0.4g Tween-80 emulsifier and 52.6g liquid paraffin were stirred and mixed uniformly to obtain an oil phase;

[0041] S2. 14.0g acrylamide, 2.0g (N,N-dimethyl-N-ethyl-N'-allyl-N'-methyl-N'-ethyl)-ethyldibromide, 0.08g sodium p-styrenesulfonate were added to 28.92g deionized water, stirred to completely dissolve, and the water phase pH was adjusted to 8 with 2% sodium hydroxide solution to obtain a water phase;

[0042] S3. The oil phase was added to a three-necked flask, and the water phase was slowly added to the oil phase at a speed of 500 rpm, and after the addition was completed, the emulsion was stirred for 50 min to obtain a stable water-in-oil pre-emulsion;

[0043] S4. The three-necked flask was connected to nitrogen, a thermometer and an initiator dropping tube, nitrogen was passed for 15 min to remove oxygen, the temperature was raised to 30°C, 0.020g ammonium persulfate and 0.020g sodium sulfite were slowly added, the reaction time was 5h, and a quick-release ternary copolymer emulsion type fracturing fluid thickening agent was obtained.

[0044] Example 3

[0045] The synthesis experiment procedure of the instant ternary copolymer emulsion type fracturing fluid thickening agent is as follows:

[0046] S1. 3.0g Span-80 emulsifier, 0.6g Tween-80 emulsifier and 55.4g liquid paraffin are stirred and mixed uniformly to obtain an oil phase;

[0047] S2. 13.0g acrylamide, 3.0g (N,N-dimethyl-N-ethyl-N'-allyl-N'-methyl-N'-ethyl)-ethyldibromide, 0.1g sodium p-styrenesulfonate are added to 23.9g deionized water, stirred and dissolved completely, and the water phase pH is adjusted to 8 with 2% sodium hydroxide solution to obtain a water phase;

[0048] S3. The oil phase is added to a three-necked flask, and the water phase is slowly added to the oil phase at a speed of 500 revolutions per minute, and after the addition is completed, the emulsion is stirred for 50 minutes to obtain a stable water-in-oil pre-emulsion;

[0049] S4. The three-necked flask is connected to nitrogen, a thermometer and an initiator dropping tube, nitrogen is passed for 15 minutes to remove oxygen, the temperature is raised to 30°C, 0.018g ammonium persulfate and 0.018g sodium sulfite are slowly added, the reaction time is 6h, and an instant ternary copolymer emulsion type fracturing fluid thickening agent is obtained.

[0050] Thickening agent solubility and apparent viscosity test

[0051] At a constant stirring speed of 300 revolutions per minute and a temperature of 25°C, 0.2wt% instant ternary copolymer emulsion type fracturing fluid thickening agent, polyacrylamide solid thickening agent and polyacrylamide emulsion type thickening agent solutions are prepared in the same size beaker, and the time when the viscosity no longer increases is determined as the solubility time of the thickening agent, as shown in Table 1.

[0052] Table 1 Comparison of solubility times of three thickening agents (25°C, 0.2wt%)

[0053]

[0054] As shown in Table 1, all three examples of the fast-dissolving ternary copolymer emulsion fracturing fluid thickener dissolved completely within 5 minutes, while the dissolution times for polyacrylamide solid thickener and polyacrylamide emulsion thickener were 56 minutes and 15 minutes, respectively. This demonstrates that using the thickener of this invention can significantly save construction time and improve work efficiency. The apparent viscosity of the three examples of the fast-dissolving ternary copolymer emulsion fracturing fluid thickener after dissolution was greater than that of the polyacrylamide solid thickener and polyacrylamide emulsion thickener, indicating stronger thickening ability. This is mainly because the (N,N-dimethyl-N-ethyl-N'-allyl-N'-methyl-N'-ethyl)-ethyldibromide monomer unit on the polymer chain segment has two quaternary ammonium salt groups, making the polymer molecules more extended and increasing the hydrodynamic volume of the polymer molecules in water, resulting in a larger mean square end-to-end distance of the formed random coils.

[0055] The apparent viscosities of 0.1wt%, 0.2wt%, and 0.3wt% fast-dissolving terpolymer emulsion thickener solutions were tested using a Brookfield viscometer at 25℃, with a No. 64 rotor and a rotation speed of 100 rpm. The test results are shown in the table.

[0056] Table 2 Apparent viscosity of fast-dissolving terpolymer emulsion fracturing fluid thickener solution

[0057] As shown in Table 2, the apparent viscosity increases with the increase of the concentration of the fast-dissolving terpolymer emulsion fracturing fluid thickener solution. Among them, the apparent viscosity of Example 3 is the highest at the same concentration. Therefore, the other properties of the thickener were tested using Example 3.

[0058] Thickener temperature and shear resistance test

[0059] The temperature and shear resistance of the product obtained in Example 3 were tested using a MARS rotational rheometer, and a 0.2 wt% terpolymer emulsion-type fracturing fluid thickener solution was prepared. Test conditions: initial temperature 30℃, heating rate 0.33℃ / min, shear rate 170s. -1 Heat to 120℃, shear for 2 hours, and the test results are as follows. Figure 1 As shown. By Figure 1 It can be seen that the viscosity of the solution after shearing is 127 mPa·s. According to SY / T 6376-2008 "General Technical Conditions for Fracturing Fluids", the viscosity after shearing is greater than 50 mPa·s. The fast-dissolving terpolymer emulsion type fracturing fluid thickener meets the construction requirements of high-temperature reservoirs.

[0060] Thickener salt resistance test

[0061] The apparent viscosity of the 0.2wt% instant ternary copolymer emulsion type fracturing fluid thickener solution was tested at different CaCl2 concentrations and different NaCl concentrations. The experimental conditions were at room temperature using a twelve-speed rotational viscometer for 170 seconds -1 The tests were conducted, and the results are shown in Figure 2 and Figure 3 As the salt concentration increased, the apparent viscosity of the instant ternary copolymer emulsion type fracturing fluid thickener decreased. When the NaCl concentration was 15wt%, the apparent viscosity of the emulsion solution reached 14.1 mPa·s; when the CaCl2 concentration was 4wt%, the apparent viscosity of the solution reached 23.4 mPa·s, showing excellent salt tolerance.

[0062] Fracturing fluid drag reduction performance test

[0063] The product obtained in Example 3 was used to prepare a slick water fracturing fluid system. The 0.01wt% instant ternary copolymer emulsion type fracturing fluid thickener was used, with 0.15wt% of a cleanup agent, 0.3wt% of an anti-swelling agent, and the rest being water. The cleanup agent was a non-ionic gemini fluorocarbon surfactant (FCF-206, brand Karamar) and methanol (mass ratio 1:2); the anti-swelling agent was potassium chloride.

[0064] The drag reduction performance test conditions for the slick water fracturing fluid system were: temperature 25℃, pipeline diameter 0.01m, pipeline length 3.95m, flow rate 42L / min; the test results are shown in Figure 4 The experimental results showed that the drag reduction rate was 72.2%, with excellent drag reduction effect, meeting the national slick water use standards.

[0065] Fracturing fluid sand carrying property, gel breaking property, and static filtration property test

[0066] The product obtained in Example 3 was used to prepare a high concentration formula fracturing fluid system. The system composition included 0.2wt% ternary copolymer emulsion type fracturing fluid thickener, 0.4wt% iron ion stabilizer, 1.5wt% anti-swelling agent, 0.5wt% crosslinking agent, 1.5wt% cleanup agent, and the rest being water. The anti-swelling agent was KCl; the crosslinking agent was sodium borate; the cleanup agent was a non-ionic gemini fluorocarbon surfactant (FCF-206, brand Karamar) and methanol (mass ratio 1:2).

[0067] (1) Test the sand-carrying property of the high-concentration formula fracturing fluid system. Mix the fracturing fluid system with 20wt%, 30wt%, and 40wt% content of quartz sand particles (20-40 mesh) uniformly, and place them in a specific specification (100 mL) graduated cylinder. According to the SY / T 7627-2021 water-based fracturing fluid technical requirements, read the settling distance of the quartz sand particles in the oven at 120°C over time, and measure it at 15 min, 30 min, 60 min, and 120 min, and calculate the settling rate (settling rate = settling distance / time). The test results are shown in Table 3.

[0068] Table 3 Sand-carrying settling rate of high-concentration formula emulsion fracturing fluid system (120°C)

[0069] Settling time (min) 15 30 60 120 Settling rate of 20 wt% quartz sand particles (cm / min) 0.00000 0.00670 0.050 0.0038 Settling rate of 30 wt% quartz sand particles (cm / min) 0.00033 0.00067 0.0067 0.0042 Settling rate of 40 wt% quartz sand particles (cm / min) 0.00670 0.0083 0.0580 0.0041

[0070] The experimental results show that at 120°C, the settling rate of quartz sand particles in the high-concentration formula fracturing fluid system with 20wt%, 30wt%, and 40wt% content is 0.05 cm / min, 0.0067 cm / min, and 0.058 cm / min respectively in the first 60 min. It is observed that the settling rate of quartz sand particles with 30wt% content is the smallest, which is the best sanding amount. The content of 20wt% quartz sand particles is low under the action of gravity, the distance between quartz sand particles is large, and the falling space is too large, so the settling is faster. The content of 40wt% quartz sand particles is high, the distance between quartz sand particles is smaller, and the settling rate is fast under the influence of gravity. However, the overall settling rate is small, indicating that it has good viscoelastic sand-carrying property.

[0071] (2) Test the gel breaking property of the high-concentration formula emulsion fracturing fluid system. Add different content of gel breaker ammonium persulfate to 50 mL of the fracturing fluid system, and break the gel in the 120°C oven according to the SY / T 7627-2021 water-based fracturing fluid technical requirements. Record the time of complete gel breaking of the fracturing fluid, measure the viscosity and residue amount of the gel breaking fluid, and test the surface tension and interfacial tension of the gel breaking fluid using JJ2000 surface tension meter and TX-500 ultra-low rotation drop interfacial tension meter respectively (the oil phase is kerosene when measuring the interfacial tension); the test results are shown in Table 4.

[0072] Table 4 Gel breaking performance of high-concentration formula emulsion fracturing fluid system (120°C)

[0073]

[0074] The experimental results show that the gel breaking time of the emulsion type fracturing fluid system is short at 120 DEG C. In high temperature formation, the gel breaking agent dosage can be selected as 0.04wt%, the gel breaking agent dosage is small and the gel breaking time is short. In medium and low temperature formation, the gel breaking agent dosage can be selected as 0.07wt%, the surface tension of the gel breaking fluid is less than or equal to 28mN / m, the interfacial tension is less than or equal to 2mN / m, and the standard is met. As shown in Table 3, the surface tension and the interfacial tension of the gel breaking fluid are low, on the one hand, the cleanup aid is a surfactant, which reduces the surface and interfacial tension, and on the other hand, the quaternary ammonium salt cation and sulfonate ion contained in the thickening agent are hydrophilic groups, which also play the role of surfactants, and can effectively reduce the surface and interfacial tension of the gel breaking fluid. The residue content of each test gel breaking fluid is less than or equal to 600mg / L, the test results meet the requirements of the general technical conditions of fracturing fluid, and the test data after gel breaking also meet the standard 'General Technical Conditions of Fracturing Fluid', which shows that the thickening agent has good gel breaking performance.

[0075] (3) The static filtration of the high-concentration formula emulsion type fracturing fluid system is tested, the initial filtration Q SP , the filtration rate V c and the static filtration coefficient C3 of the fracturing fluid system are tested under the condition of high temperature (120 DEG C) according to the technical requirements of the water-based fracturing fluid SY / T 7627-2021, and the test results are shown in Figure 5 and Table 5.

[0076] Table 5 Static filtration parameters of the high-concentration formula emulsion type fracturing fluid system (120 DEG C)

[0077] Q SP Leak-off coefficient (m / min 1 / 2 )]]> V c rate (m / min) [C3 initial fluid loss (ml 3 / m 2 )]]> 7.5 x 10 -6 ]]> 1.2 x 10 -7 ]]> 2.178 x 10 -4 ]]>

[0078] The experimental results show that the initial filtration Q SP , the filtration rate V c and the static filtration coefficient C3 all meet the standard (Q SP ≤1x10 - 2 m 3 / m 2 , V c ≤1x10 -4 m / min, C3≤6x10 -3 m / min 1 / 2 ), and have good filtration performance.

[0079] In summary, the instantaneously dissolved ternary copolymer emulsion type fracturing fluid thickening agent developed in the application has the advantages of fast dissolution, high apparent viscosity, good temperature resistance, shear resistance and salt resistance, and the fracturing fluid system prepared by the thickening agent has excellent properties such as drag reduction, sand carrying, gel breaking, static filtration and the like, meets the corresponding index requirements of oil and gas field fracturing, and has a good application prospect in offshore oil and gas and shale oil and gas development.

Claims

1. A fast dissolving terpolymer emulsion type fracturing fluid viscosifier characterized in that, The fracturing fluid thickening agent is prepared by inverse emulsion polymerization of the following raw materials, which include, by mass percentage: Monomer: 10-20%; Emulsifier: 2.0-4.0%; Initiator: 0.02-0.04%; Liquid paraffin: 50-60%; The rest is deionized water; The monomers are acrylamide, (N,N-dimethyl-N-ethyl-N'-allyl-N'-methyl-N'-ethyl)-ethyldimonium bromide, and sodium p-styrenesulfonate, in a mass ratio of 10-14:2-3:0.008-0.1, respectively, wherein the (N,N-dimethyl-N-ethyl-N'-allyl-N'-methyl-N'-ethyl)-ethyldimonium bromide has the following structure:

2. A quick-dissolving terpolymer emulsion fracturing fluid viscosifier according to claim 1, characterized in that, The emulsifier is Span-80 and Tween-80, and the mass ratio of the two is 5:

1.

3. A quick-dissolving terpolymer emulsion fracturing fluid viscosifier according to claim 1, wherein the monomer mixture comprises 20 to 30 wt% of the acrylic acid, 20 to 30 wt% of the methacrylic acid, and 40 to 60 wt% of the maleic anhydride. The initiator is composed of ammonium persulfate and sodium sulfite, and the mass ratio of the two is 1:

1.

4. The instant terpolymer emulsion fracturing fluid viscosifier of claim 1 wherein, The mass ratio of the liquid paraffin to the deionized water is 5.5-6.0:4.5-4.

0.

5. The fast-dissolving terpolymer emulsion-type fracturing fluid thickener as described in claim 2, characterized in that, The (N,N-dimethyl-N-ethyl-N'-allyl-N'-methyl-N'-ethyl)-ethyldibromide ammonium is obtained by the reaction of N,N,N'-trimethyl-N'-allyl ethylenediamine (TMPEMA) and bromoethane; wherein the TMPEMA is obtained by the reaction of chloropropylene and N,N,N'-trimethyl ethylenediamine under the catalysis of a basic triethylamine catalyst.

6. A quick-dissolving terpolymer emulsion fracturing fluid viscosifier according to claim 1, wherein the monomer mixture comprises 20 to 30 wt% of the acrylic acid, 20 to 30 wt% of the methacrylic acid, and 40 to 60 wt% of the maleic anhydride. The synthesis method of the monomer (N,N-dimethyl-N-ethyl-N'-allyl-N'-methyl-N'-ethyl)-ethyldibromide ammonium includes the following steps: S1. 0.11 mol of chloropropylene and 0.10 mol of N,N,N'-trimethyl ethylenediamine are added to a round-bottom flask containing 100 mL of acetone, a magnetic stirrer is used to stir the solution uniformly, then 5 g of the basic catalyst triethylamine is added to the solution, the temperature is raised to 30°C, N2 is continuously introduced for continuous reaction for 40 min, and rotary evaporation is performed at 45°C for 30 min to obtain an intermediate product TMPEMA; S2. 0.10 mol of TMPEMA is dissolved in 75 mL of anhydrous acetonitrile, 0.22 mol of bromoethane is added, it is transferred to a high-pressure reaction kettle, it is reacted at 60°C for 16 h, volatile substances are removed by reduced-pressure distillation, it is washed with diethyl ether and dried in a vacuum oven to obtain the monomer (N,N-dimethyl-N-ethyl-N'-allyl-N'-methyl-N'-ethyl)-ethyldibromide ammonium.

7. A quick-dissolving terpolymer emulsion fracturing fluid viscosifier according to any one of claims 1 to 6, characterized in that, The preparation method of the instant ternary copolymer emulsion type fracturing fluid thickening agent includes the following steps: S1. The emulsifier and the liquid paraffin are stirred and mixed uniformly to obtain an oil phase; S2. The monomer acrylamide, sodium p-styrenesulfonate, and (N,N-dimethyl-N-ethyl-N'-allyl-N'-methyl-N'-ethyl)-ethyldibromide ammonium are added to deionized water, stirred and completely dissolved, and the pH of the water phase is adjusted to 8 with a 2% sodium hydroxide solution to obtain a water phase; S3. The oil phase is added to a three-necked flask, the water phase is slowly added to the oil phase at a speed of 500 revolutions per minute, and after the addition is completed, the stirring and emulsification are continued for 50 min to obtain a stable water-in-oil pre-emulsion; S4. The three-necked flask is connected to nitrogen, a thermometer, and an initiator dropping tube, oxygen is removed by nitrogen for 15 min, the temperature is raised to 25-35°C, the initiator is slowly added, the reaction time is 3-6 h, and the instant ternary copolymer emulsion type fracturing fluid thickening agent is obtained.

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