Salt-tolerant associated emulsion type fracturing fluid thickening agent as well as preparation method and application thereof

Abstract

The invention relates to the technical field of oil-gas field development, in particular to a salt-tolerant associated emulsion type fracturing fluid thickener as well as a preparation method and application thereof, and the salt-tolerant associated emulsion type fracturing fluid thickener is prepared by polymerizing a water-phase mixed solution and an oil-phase mixed solution; wherein the water-phase mixed solution is prepared by mixing the following components in parts by weight: 10 to 15 parts of acrylamide, 8 to 12 parts of 2-acrylamido-2-methylpropanesulfonic acid, 6 to 10 parts of methacryloyloxyethyl (4-sulfo) benzyl dimethyl ammonium chloride, 4 to 8 parts of 2-acrylic acid-2-(2-hexadecyl piperazine) ethyl ester and 50 parts of water; the oil-phase mixed solution is prepared by mixing 4-6 parts by weight of an emulsifier and 30-50 parts by weight of white oil; the preparation method comprises the following steps: uniformly mixing an oil-phase mixed solution and a water-phase mixed solution, and reacting at 45-70 DEG C for 2-4 hours under the initiation of azodiisobutyronitrile, the salt-tolerant association emulsion type fracturing fluid thickener can realize hydrophobic association tackifying in water, has the functions of salt tolerance, resistance reduction, sand carrying and the like, is low in residue, small in damage and good in temperature resistance and shear resistance, and meets the construction requirements.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development, and in particular to a salt-resistant associative emulsion type fracturing fluid thickener, a preparation method thereof and application thereof. Background Art

[0002] With the deepening of volume fracturing development of unconventional oil and gas resources, the scale of production enhancement measures is getting larger and larger, and the consumption of fresh water resources is also increasing. More and more high-mineralized water such as flowback fluid and produced water is used as fracturing fluid, and the requirements for fracturing fluid salt resistance are getting higher and higher. Conventional polymer fracturing fluid thickeners have insufficient salt resistance, which causes the molecular chain to curl in high-mineralization solutions, resulting in a decrease in solution viscosity, and limited resistance reduction, sand carrying and other performance. Summary of the invention

[0003] The purpose of the present invention is to provide a salt-resistant associative emulsion fracturing fluid thickener, a preparation method and an application thereof. The salt-resistant associative emulsion fracturing fluid thickener is obtained by inverse emulsion copolymerization, has the functions of salt resistance, drag reduction, sand carrying, etc., and solves the problems that the current polymer fracturing fluid thickener has poor performance due to insufficient salt resistance.

[0004] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0005] The present invention provides a salt-tolerant associative emulsion type fracturing fluid thickener, which is prepared by polymerizing a water phase mixed liquid and an oil phase mixed liquid;

[0006] The components of the aqueous phase mixed liquid include, by weight, 10-15 parts of acrylamide, 8-12 parts of 2-acrylamido-2-methylpropanesulfonic acid, 6-10 parts of methacryloyloxyethyl (4-sulfonic acid) benzyldimethylammonium chloride, 4-8 parts of 2-acrylic acid-2-(2-hexadecylpiperazine)ethyl ester and 50 parts of water; the components of the oil phase mixed liquid include, by weight, 4-6 parts of emulsifier and 30-50 parts of white oil.

[0007] The specific chemical structure of the salt-tolerant associative emulsion fracturing fluid thickener is as follows:

[0008] Preferably, the emulsifier is a mixture of span-80 and tween-60.

[0009] More preferably, the weight ratio of span-80 to tween-60 is (10-30):1.

[0010] In a second aspect, the present invention provides a method for preparing the salt-tolerant associative emulsion fracturing fluid thickener, comprising the following steps:

[0011] S1, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, methacryloyloxyethyl (4-sulfonic acid) benzyl dimethyl ammonium chloride, 2-acrylic acid-2-(2-hexadecylpiperazine)ethyl ester and water are mixed and stirred uniformly, and the pH of the system is adjusted with a sodium hydroxide solution to obtain an aqueous phase mixture;

[0012] S2, mixing the emulsifier and the white oil evenly to obtain an oil phase mixed liquid;

[0013] S3, uniformly mix the oil phase mixture and the water phase mixture, and heat them; drop diisobutyronitrile is added to the reaction mixture, and the reaction is continued at the temperature for 2h-4h to obtain a salt-resistant associative emulsion fracturing fluid thickener.

[0014] Preferably, in step S1, the concentration of the sodium hydroxide solution is 20%.

[0015] Preferably, the pH of the aqueous phase system is adjusted to 6.5-7.5.

[0016] Preferably, in step S3, the oil phase mixed liquid and the water phase mixed liquid are uniformly mixed, nitrogen is passed through the mixed liquid to deoxygenate the mixed liquid under stirring conditions, and the mixed liquid is heated to 45° C.-70° C.

[0017] Preferably, in step S3, 0.015 wt. % to 0.025 wt. % of azobisisobutyronitrile based on the total weight of the monomers is added dropwise to the reaction mixture.

[0018] In a third aspect, the present invention provides an application of the salt-resistant associative emulsion fracturing fluid thickener in fracturing construction.

[0019] Based on the above technical solutions, the technical effects that can be achieved by the present invention are:

[0020] Compared with the existing technology, the salt-resistant associative emulsion fracturing fluid thickener can achieve hydrophobic associative viscosity increase in water, has the functions of salt resistance, drag reduction, sand carrying, etc., has low residue, little damage, good temperature and shear resistance, and meets the construction requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 The salt-tolerant associative emulsion fracturing fluid thickener of Example 4 of the present invention is 12×10 4 mg / L mineralized water and clean water were prepared into fracturing fluid effect diagram according to the ratio of 0.8wt.%;

[0023] Figure 2 This is a static sand suspension effect diagram of the salt-tolerant associative emulsion fracturing fluid thickener of Example 4 of the present invention after being prepared into a fracturing fluid at a ratio of 0.8wt.%;

[0024] Figure 3 This is the heat and shear resistance rheology diagram of Example 4;

[0025] Figure 4 This is the temperature and shear resistance rheology diagram of the comparative example. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all of the embodiments.

[0027] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0028] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the reagents, materials, etc. used in the following examples, unless otherwise specified, can be obtained from commercial channels.

[0029] Example 1

[0030] A salt-resistant associative emulsion fracturing fluid thickener is prepared by the following preparation method:

[0031] S1, 10 parts by weight of acrylamide, 8 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 10 parts by weight of methacryloyloxyethyl (4-sulfonic acid) benzyldimethylammonium chloride, 4 parts by weight of 2-acrylic acid-2-(2-hexadecylpiperazine)ethyl ester and 50 parts by weight of water were mixed and stirred uniformly, and the pH was adjusted to 6.5 with a 20% concentration of sodium hydroxide solution to obtain an aqueous phase mixture;

[0032] S2, 6 parts by weight of an emulsifier and 30 parts by weight of white oil are mixed uniformly to obtain an oil phase mixture; wherein the emulsifier is a mixture of span-60 and tween-60, and the weight ratio of the two is 10:1;

[0033] S3, the oil phase mixed liquid and the water phase mixed liquid are uniformly mixed, nitrogen is passed through the mixed liquid for deoxygenation under stirring conditions, and the mixture is heated to 45°C, 0.015 wt.% of azobisisobutyronitrile accounting for the total weight of the monomers is added dropwise, and the reaction is continued at the temperature for 2 hours to obtain a salt-resistant associative emulsion type fracturing fluid thickener.

[0034] The total weight of monomers is the sum of the weights of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, methacryloyloxyethyl (4-sulfonic acid) benzyldimethylammonium chloride, and 2-(2-hexadecylpiperazine)ethyl acrylate.

[0035] Example 2

[0036] A salt-resistant associative emulsion fracturing fluid thickener is prepared by the following preparation method:

[0037] S1, 12 parts by weight of acrylamide, 12 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 7 parts by weight of methacryloyloxyethyl (4-sulfonic acid) benzyldimethylammonium chloride, 5 parts by weight of 2-acrylic acid-2-(2-hexadecylpiperazine)ethyl ester and 50 parts by weight of water were mixed and stirred uniformly, and the pH was adjusted to 7.5 with a 20% concentration of sodium hydroxide solution to obtain an aqueous phase mixture;

[0038] S2, 4 parts by weight of an emulsifier and 35 parts by weight of white oil were mixed uniformly to obtain an oil phase mixture; wherein the emulsifier was a mixture of span-60 and tween-60, and the weight ratio of the two was 15:1;

[0039] S3, the oil phase mixed liquid and the water phase mixed liquid are uniformly mixed, nitrogen is passed through the mixed liquid under stirring to deoxygenate, and the mixture is heated to 50°C, 0.022 wt.% of azobisisobutyronitrile accounting for the total weight of the monomers is added dropwise, and the reaction is continued at the temperature for 3 hours to obtain a salt-resistant associative emulsion type fracturing fluid thickener.

[0040] The total weight of monomers is the sum of the weights of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, methacryloyloxyethyl (4-sulfonic acid) benzyldimethylammonium chloride, and 2-(2-hexadecylpiperazine)ethyl acrylate.

[0041] Example 3

[0042] A salt-resistant associative emulsion fracturing fluid thickener is prepared by the following preparation method:

[0043] S1, 13 parts by weight of acrylamide, 11 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 9 parts by weight of methacryloyloxyethyl (4-sulfonic acid) benzyldimethylammonium chloride, 7 parts by weight of 2-acrylic acid-2-(2-hexadecylpiperazine)ethyl ester and 50 parts by weight of water were mixed and stirred uniformly, and the pH was adjusted to 6.8 with a 20% concentration of sodium hydroxide solution to obtain an aqueous phase mixture;

[0044] S2, 5 parts by weight of an emulsifier and 45 parts by weight of white oil are mixed uniformly to obtain an oil phase mixture; wherein the emulsifier is a mixture of span-60 and tween-60, and the weight ratio of the two is 20:1;

[0045] S3, the oil phase mixed liquid and the water phase mixed liquid are uniformly mixed, nitrogen is passed through under stirring conditions to deoxygenate, and the mixture is heated to 55°C, 0.018 wt.% of azobisisobutyronitrile accounting for the total weight of the monomers is added dropwise, and the reaction is continued at the temperature for 4 hours to obtain a salt-resistant associative emulsion type fracturing fluid thickener.

[0046] The total weight of monomers is the sum of the weights of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, methacryloyloxyethyl (4-sulfonic acid) benzyldimethylammonium chloride, and 2-(2-hexadecylpiperazine)ethyl acrylate.

[0047] Example 4

[0048] A salt-resistant associative emulsion fracturing fluid thickener is prepared by the following preparation method:

[0049] S1, 14 parts by weight of acrylamide, 10 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 8 parts by weight of methacryloyloxyethyl (4-sulfonic acid) benzyldimethylammonium chloride, 6 parts by weight of 2-acrylic acid-2-(2-hexadecylpiperazine)ethyl ester and 50 parts by weight of water were mixed and stirred uniformly, and the pH was adjusted to 7.2 with a 20% concentration of sodium hydroxide solution to obtain an aqueous phase mixture;

[0050] S2, 5 parts by weight of an emulsifier and 40 parts by weight of white oil are mixed uniformly to obtain an oil phase mixture; wherein the emulsifier is a mixture of span-60 and tween-60, and the weight ratio of the two is 25:1;

[0051] S3, the oil phase mixed liquid and the water phase mixed liquid are uniformly mixed, nitrogen is passed through under stirring conditions to deoxygenate, and the mixture is heated to 60°C, 0.020 wt.% of azobisisobutyronitrile accounting for the total weight of the monomers is added dropwise, and the reaction is continued at the temperature for 3 hours to obtain a salt-resistant associative emulsion type fracturing fluid thickener.

[0052] The total weight of monomers is the sum of the weights of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, methacryloyloxyethyl (4-sulfonic acid) benzyldimethylammonium chloride, and 2-(2-hexadecylpiperazine)ethyl acrylate.

[0053] Example 5

[0054] A salt-resistant associative emulsion fracturing fluid thickener is prepared by the following preparation method:

[0055] S1, 15 parts by weight of acrylamide, 9 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 6 parts by weight of methacryloyloxyethyl (4-sulfonic acid) benzyldimethylammonium chloride, 8 parts by weight of 2-acrylic acid-2-(2-hexadecylpiperazine)ethyl ester and 50 parts by weight of water were mixed and stirred uniformly, and the pH was adjusted to 7.0 with a 20% concentration of sodium hydroxide solution to obtain an aqueous phase mixture;

[0056] S2, 6 parts by weight of an emulsifier and 50 parts by weight of white oil are mixed uniformly to obtain an oil phase mixture; wherein the emulsifier is a mixture of span-60 and tween-60, and the weight ratio of the two is 30:1;

[0057] S3, the oil phase mixed liquid and the water phase mixed liquid are uniformly mixed, nitrogen is passed through under stirring conditions to deoxygenate, and the mixture is heated to 70°C, 0.025 wt.% of azobisisobutyronitrile accounting for the total weight of the monomers is added dropwise, and the reaction is continued at the temperature for 4 hours to obtain a salt-resistant associative emulsion type fracturing fluid thickener.

[0058] The total weight of monomers is the sum of the weights of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, methacryloyloxyethyl (4-sulfonic acid) benzyldimethylammonium chloride, and 2-(2-hexadecylpiperazine)ethyl acrylate.

[0059] Performance Test:

[0060] (1) Apparent viscosity test

[0061] The salt-tolerant associative emulsion fracturing fluid thickener prepared in Examples 1 to 5 was added to the mixture of 12×10 4 The fracturing fluid was prepared by mixing mg / L salt water and clean water, and the apparent viscosity was tested. The specific test results are shown in Table 1 below.

[0062] Table 1: Apparent viscosity of examples in clean water and salt water Viscosity, mPa.s Implementation 1 Implementation 2 Implementation 3 Implementation 4 Implementation 5 brine 75 79 84 90 81 Shimizu 79 81 86 93 83

[0063] 12×10 4 The apparent viscosity of the fracturing fluid prepared in 200 mg / L salt water and clean water is not much different, indicating that the thickener provided by the present invention has good salt resistance.

[0064] (2) Low viscosity drag reduction and viscosity

[0065] The salt-tolerant associative emulsion fracturing fluid thickener prepared in Examples 1 to 5 was added to the mixture of 12×10 4 A 0.05 wt.% low-viscosity fracturing fluid was prepared in 100 mg / L brine, and the viscosity and drag reduction performance were tested. The specific test results are shown in Table 2 below.

[0066] Table 2: Viscosity and drag reduction rate of the examples in salt water performance Implementation 1 Implementation 2 Implementation 3 Implementation 4 Implementation 5 Viscosity, mPa.s 2.9 3.1 3.4 3.8 3.6 Drag reduction rate, % 76.9 76.4 77.7 77.8 76.9

[0067] It can be seen from the table that the thickener prepared in the embodiment of the present invention has a 4 The fracturing fluid prepared in mg / L brine still has a drag reduction rate of more than 76% under high salinity conditions.

[0068] (3) Heat and shear resistance

[0069] According to the standard "SY / T 5107 Water-based Fracturing Fluid Performance Evaluation Method", the test was carried out with a mineralization of 12×10 4 The 0.8 wt.% fracturing fluids of Examples 1 to 5 prepared with mg / L brine were heated to 100 s. -1 , and the viscosity after shearing for 120 minutes at 150°C to verify its heat resistance and shear resistance. The specific test results are shown in Table 3 below.

[0070] Table 3: Heat and shear resistance of the examples in salt water

[0071] From the test results in Table 3, it can be seen that the viscosity of the fracturing fluids prepared in Examples 1 to 5 is maintained above 50 mPa.s after the shear test, which meets the standard requirements, proving that the fracturing fluids have good temperature and shear resistance at high mineralization.

[0072] (4) Sand carrying performance

[0073] The test was conducted by mineralization 12×10 4 The fracturing fluid of Example 4 (0.8 wt.%) prepared with 100 mg / L salt water was added with 20 / 40 mesh ceramsite proppant with a sand-liquid ratio of 36% to suspend sand. The specific test results are as follows Figure 2 shown.

[0074] (5) Performance after gel breaking

[0075] Referring to the standard "SY / T 5107 Water-Based Fracturing Fluid Performance Evaluation Method", the surface, interfacial tension, anti-swelling performance, residue and core damage rate of the 0.8wt.% fracturing fluid prepared in Examples 1 to 5 were tested at 95°C for 120 minutes. The specific test results are shown in Table 4 below.

[0076] Table 4: Performance of fracturing fluid prepared in the examples after gel breaking

[0077] As shown in Table 4, the viscosity of the fracturing fluids prepared in Examples 1 to 5 after gel breaking is 2.9 to 3.3 mPa.s, the core damage rate is kept below 10%, and the residue content is kept below 7 mg / L, which can achieve truly low damage.

[0078] (6) Comparative Example

[0079] The thickener of Example 4 and the polyacrylamide thickener of Comparative Example were mixed with a mineralization degree of 12×10 4 mg / L brine was used to prepare low-viscosity slippery water at a ratio of 0.05wt.% and high-viscosity sand-carrying fluid at a ratio of 0.8wt.%, and their performances were tested respectively. The results are shown in Table 5. Figure 3 and Figure 4 shown.

[0080] It can be seen from the table that, compared with the comparative example, the thickener prepared in the embodiment provided by the present invention has a higher drag reduction rate, better temperature resistance and shear resistance, lower residue and less damage, indicating better salt resistance.

[0081] Table 5 Comparative performance

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A salt-tolerant associative emulsion fracturing fluid thickener, characterized in that: The salt-resistant associative emulsion fracturing fluid thickener is prepared by polymerizing a water phase mixed liquid and an oil phase mixed liquid; The components of the aqueous phase mixed liquid include, by weight, 10-15 parts of acrylamide, 8-12 parts of 2-acrylamido-2-methylpropanesulfonic acid, 6-10 parts of methacryloyloxyethyl (4-sulfonic acid) benzyldimethylammonium chloride, 4-8 parts of 2-acrylic acid-2-(2-hexadecylpiperazine)ethyl ester and 50 parts of water; the components of the oil phase mixed liquid include, by weight, 4-6 parts of emulsifier and 30-50 parts of white oil.

2. The salt-tolerant associative emulsion fracturing fluid thickener according to claim 1, characterized in that: The emulsifier is a mixture of span-80 and tween-60.

3. The salt-tolerant associative emulsion fracturing fluid thickener according to claim 2, characterized in that: The weight ratio of span-80 to tween-60 is (10-30):

1.

4. A method for preparing the salt-tolerant associative emulsion fracturing fluid thickener according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, methacryloyloxyethyl (4-sulfonic acid) benzyl dimethyl ammonium chloride, 2-acrylic acid-2-(2-hexadecylpiperazine)ethyl ester and water are mixed and stirred uniformly, and the pH of the system is adjusted with a sodium hydroxide solution to obtain an aqueous phase mixture; S2, mixing the emulsifier and the white oil evenly to obtain an oil phase mixed liquid; S3, uniformly mixing the oil phase mixed liquid and the water phase mixed liquid, and heating; dropping diisobutyronitrile into the reaction mixed liquid, and continuing the reaction at the same temperature to obtain a salt-resistant associative emulsion type fracturing fluid thickener.

5. The preparation method according to claim 4, characterized in that: In step S1, the concentration of the sodium hydroxide solution is 20%.

6. The preparation method according to claim 4, characterized in that: The pH of the aqueous phase system was adjusted to 6.5-7.

5.

7. The preparation method according to claim 4, characterized in that: In step S3, the oil phase mixed liquid and the water phase mixed liquid are uniformly mixed, nitrogen is passed through the mixed liquid to deoxygenate the mixed liquid under stirring conditions, and the mixed liquid is heated to 45° C.-70° C.

8. The preparation method according to claim 4, characterized in that: In step S3, 0.015 wt. % to 0.025 wt. % of azobisisobutyronitrile based on the total weight of the monomers is added dropwise to the reaction mixture.

9. The preparation method according to claim 4, characterized in that: In step S3, the reaction is continued for 2 h to 4 h.

10. Use of the salt-resistant associative emulsion fracturing fluid thickener according to any one of claims 1 to 3 in fracturing construction.

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