Preparation method and application of low-concentration clean fracturing fluid with thermal thickening performance

Abstract

The invention discloses a preparation method and application of a low-concentration clean fracturing fluid with thermal thickening performance, and belongs to the technical field of high-temperature-resistant and thermal thickening fracturing agents. The invention provides the surfactant with the following structure, the novel fracturing fluid which not only can meet the fracturing requirements of high-temperature oil and gas reservoirs but also meets the environmental protection requirements can be obtained under the condition of lower concentration, powerful technical support is provided for efficient and green development of oil and gas resources, and the surfactant has wide application prospects and important practical significance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-temperature-resistant and heat-thickening fracturing agents, and particularly relates to a preparation method and application of a low-concentration clean fracturing fluid with heat-thickening performance. BACKGROUND

[0002] With the increasing difficulty of oil and gas resource exploitation in China, the development of low-permeability, ultra-low-permeability oil and gas reservoirs and deep high-temperature oil and gas reservoirs gradually increases, and the hydraulic fracturing technology as an important stimulation measure plays a crucial role in the development of these complex oil and gas reservoirs. As a key substance in the hydraulic fracturing construction, the performance of the fracturing fluid directly affects the fracturing effect and the productivity of the oil and gas well.

[0003] At present, common fracturing fluid systems include polymer fracturing fluid and surfactant fracturing fluid. However, these traditional fracturing fluid systems have many problems in practical application. For example, the polymer fracturing fluid has many disadvantages such as easy damage to the reservoir due to much residue, incomplete gel breaking affecting flowback and permeability, unstable performance due to sensitivity to temperature and shear, difficult treatment of flowback fluid and great environmental protection pressure, poor compatibility with the reservoir and high cost; although the existing surfactant fracturing fluid has certain advantages, it also has obvious disadvantages, and the most common problem is limited temperature resistance, that is, when the temperature rises, the viscosity is difficult to maintain, so that the sand carrying capacity becomes weak, and even completely lost. It is pointed out in the related review literature [Drilling & Production Technology, 2009, 32(3): 93-96.] by Zhang Chaohu et al. that when the temperature of the viscoelastic surfactant (VES) fracturing fluid exceeds 80℃, the viscosity will decrease significantly, resulting in insufficient sand carrying capacity and unable to effectively support the fracture. This phenomenon will seriously affect the fracturing effect in practical application, especially in high-temperature formations, the performance of the surfactant fracturing fluid decreases more obviously. In order to make the viscoelastic surfactant fracturing fluid still maintain sufficient viscosity at high temperature to meet the sand carrying demand, the common method is to increase its concentration. However, this measure greatly increases the exploitation cost, compresses the profit space, and brings challenges to the economic and efficient exploitation of oilfields. SUMMARY

[0004] Therefore, the present application innovatively designs and synthesizes a brand-new surfactant, and the unique molecular structure of the surfactant gives the fracturing fluid a prominent advantage: excellent viscoelastic properties at a lower use concentration, and more outstandingly excellent high-temperature resistance, and even the effect of viscosity increase with temperature rise, that is, with the increase of temperature, the viscosity not only does not decrease, but further increases, which makes the fracturing fluid still maintain good sand carrying capacity and significant viscoelastic properties in a high-temperature environment.

[0005] The application starts from the molecular design of surfactants, and successfully develops a new fracturing fluid which meets the fracturing requirements of high-temperature oil and gas reservoirs at a lower concentration and meets the environmental protection requirements through innovative molecular structure design and synthesis method, thereby providing strong technical support for efficient and green development of oil and gas resources, and having wide application prospect and important practical significance.

[0006] The first object of the application is to provide a double-quaternary ammonium salt cationic surfactant containing two amide groups, which has the following structural formula:

[0007]

[0008] In an embodiment, the surfactant has a long saturated alkane hydrophobic tail chain with up to 22 carbon atoms, two consecutive quaternary ammonium salt hydrophilic head groups; the hydrophobic tail chain and the hydrophilic head group are linked by a transition segment containing two amide groups; and the number of main chain atoms is up to 30 except for the hydrophilic head group.

[0009] In an embodiment, the surfactant contains two amide bonds, so that it is more easily degradable under natural conditions and has environmental friendly characteristics.

[0010] The second object of the application is to provide a synthesis method of the surfactant.

[0011] In an embodiment, the synthesis route of the surfactant is as follows:

[0012]

[0013] In an embodiment, the synthesis method of the surfactant comprises:

[0014] 1) Preparation of dodecanoyl chloride: dichlorosulfoxide is slowly added to dodecanoic acid at 60-80°C, and the generated acidic gas is absorbed with sodium hydroxide aqueous solution; the reaction is stopped when the system is clear and transparent and no acidic gas is generated; then dichlorosulfoxide is removed under reduced pressure to obtain a light yellow viscous liquid, which is dodecanoyl chloride;

[0015] 2) Synthesis of intermediate 1: β-alanine methyl ester hydrochloride and triethylamine are dissolved uniformly with CH2Cl2, then dodecanoyl chloride is slowly added dropwise under ice bath condition, and the reaction is continued for 2-5 h after the dropwise addition is completed; after the reaction is completed, the reaction solution is extracted with hydrochloric acid aqueous solution, and the lower clear liquid is dried with appropriate anhydrous magnesium sulfate; then the filtrate is filtered and the CH2Cl2 in the filtrate is removed under reduced pressure at 30-40°C to obtain white solid, which is intermediate 1;

[0016] 3) Synthesis of intermediate 2: N,N-dimethyl-1,3-propanediamine was reacted with intermediate 1 at 80-120℃ for 20-40 h. After the reaction was completed, the mixture was allowed to stand at room temperature, recrystallized with ethyl acetate / ethanol, and dried to obtain a white powder, which is intermediate 2.

[0017] 4) Synthesis of the surfactant: 3-bromopropyltrimethylammonium bromide and intermediate 2 were dissolved together in anhydrous ethanol and reacted at 80-100℃ for 20-50 h. After the reaction was completed, the solvent was removed under reduced pressure, and then washed with ethanol / ethyl acetate and dried to obtain a pure surfactant, which was a white solid, denoted as CADQA-22.

[0018] A third objective of this invention is to provide a viscoelastic solution with thermal thickening properties, which contains the aforementioned surfactant.

[0019] The fourth objective of this invention is to provide a method for improving the temperature resistance of fracturing fluid, which involves increasing the viscosity of the fracturing fluid at high temperatures by adding the aforementioned surfactant.

[0020] A fifth objective of this invention is to provide a heat-resistant, thickened fracturing fluid containing the aforementioned surfactant.

[0021] In one embodiment, the fracturing fluid contains the aforementioned surfactant and sodium palmitate.

[0022] In one embodiment, the total mass concentration of the above-mentioned surfactant and sodium palmitate in the fracturing fluid is not less than 1 wt%.

[0023] In one embodiment, the total mass concentration of the surfactant and sodium palmitate in the fracturing fluid is 1 wt%-2 wt%. More preferably, it is 1 wt%-1.2 wt%.

[0024] In one embodiment, the fracturing fluid contains a total mass concentration of 1wt%-2wt% of surfactant and sodium palmitate at a shear rate of 100 s. -1 At 80°C, the viscosity can still be maintained at 100 mPa·s.

[0025] In one embodiment, the fracturing fluid formulation, by mass fraction, comprises 0.65%–0.77% surfactant (CADQA-22), 0.36%–0.43% sodium palmitate (SP), 0–2% inorganic salt, and the balance being water.

[0026] In one embodiment, the inorganic salt is potassium chloride (KCl).

[0027] In one embodiment, the fracturing fluid is prepared as follows:

[0028] The deionized water is added with 0.36wt%-0.43wt% of sodium palmitate (SP), 0.65wt%-0.77wt% of surfactant CADQA-22 and 0-2wt% of inorganic salt, and is uniformly mixed to obtain the fracturing fluid.

[0029] In an embodiment, the step of uniformly mixing can specifically include stirring at 40-90℃ for a period of time, and then standing and diffusing for a period of time.

[0030] In an embodiment, the stirring is performed at 40-90℃ for 20-60 minutes.

[0031] In an embodiment, the standing and diffusing can specifically include being first placed in a thermostat at 70-90℃ for 5-50h, and then being taken out; and being placed in a thermostat at 20-30℃ for 5-50h.

[0032] A sixth object of the present application is to provide the use of the above-mentioned surfactant or the above-mentioned temperature-resistant and heat-thickening fracturing fluid in the exploitation of oil and gas resources.

[0033] A sixth object of the present application is to provide the use of the above-mentioned surfactant or the above-mentioned temperature-resistant and heat-thickening fracturing fluid in the fracturing operation of high-temperature oil and gas reservoirs, shale oil exploitation and oil and gas reservoirs with higher environmental protection requirements.

[0034] Advantages:

[0035] High-temperature resistance and significantly improved heat-thickening performance: the fracturing fluid system of the present application overcomes the defect of viscosity reduction of traditional surfactant fracturing fluid under high-temperature environment through innovative surfactant molecular structure and formula design. The system can not only maintain a high viscosity when the temperature rises, but also achieve heat-thickening effect. This characteristic enables the fracturing fluid to still maintain strong sand-carrying capacity in high-temperature formations, effectively supporting the fractures, thereby significantly improving the fracturing effect and the productivity of oil and gas wells.

[0036] Compared with the prior art, the fracturing fluid obtained based on the specific surfactant and sodium palmitate in the present application can still maintain a high viscosity under high-temperature conditions above 80℃, and the viscosity further increases with the increase of temperature, ensuring the efficiency and reliability of the fracturing operation. Moreover, when the total mass concentration of the surfactant and sodium palmitate in the fracturing fluid is only 1wt%-2wt%, the viscosity at 80℃ can still be maintained at 100mPa·s at a shear rate of 100s -1

[0037] ​Comprehensive performance optimization, reduce the cost of mining: the fracturing fluid system of the application improves the high temperature resistance performance while optimizing the overall formula, reduces the use concentration of surfactant. Compared with the traditional high temperature resistant VES fracturing fluid which enhances the performance by increasing the concentration, the application effectively reduces the material cost and construction cost under the premise of ensuring the fracturing effect. BRIEF DESCRIPTION OF DRAWINGS

[0038] The drawings accompanying the specification of this application are used to provide further understanding of the application, the illustrative embodiments of the application and the description thereof are used to explain the application, and do not constitute undue limitation on the application.

[0039] Figure 1 The nuclear magnetic spectrum of the new surfactant CADQA-22 prepared for example 1 of the application (H NMR); 1

[0040] Figure 2 The macroscopic real photo of the fracturing fluid system (0.74wt% CADQA-22, 0.41wt% SP) of example 2 of the application;

[0041] Figure 3 The freeze transmission electron microscope (Croy-TEM) of the fracturing fluid system (0.74wt% CADQA-22, 0.41wt% SP) of example 2 of the application;

[0042] Figure 4 The steady-state rheological diagram of the fracturing fluid system (0.74wt% CADQA-22, 0.41wt% SP) of example 2 of the application;

[0043] Figure 5 The dynamic rheological diagram of the fracturing fluid system (0.74wt% CADQA-22, 0.41wt% SP) of example 2 of the application;

[0044] Figure 6 The steady-state rheological diagram of the fracturing fluid system (0.74wt% CADQA-22, 0.41wt% SP, 1wt% KCl) of example 3 of the application (shear rate 100s -1 );

[0045] Figure 7 The temperature scanning rheological diagram of the fracturing fluid system (0.74wt% CADQA-22, 0.41wt% SP, 1wt% KCl) of example 3 of the application;

[0046] Figure 8 ​Macroscopic photograph of Comparative Example 1 of the present application (0.74 wt% OTAB, 0.41 wt% SP), Comparative Example 2 (0.74 wt% OTAB, 0.41 wt% SP, 1 wt% KCl);

[0047] Figure 9 Temperature sweep rheogram of Comparative Example 1 of the present application (0.74 wt% OTAB, 0.41 wt% SP), Comparative Example 2 (0.74 wt% OTAB, 0.41 wt% SP, 1 wt% KCl);

[0048] Figure 10 Temperature sweep rheogram of Comparative Example 3 of the present application (0.74 wt% C18-DQA, 0.41 wt% SP);

[0049] Figure 11 Steady state rheogram of Comparative Example 3 of the present application (0.74 wt% C18-DQA, 0.41 wt% SP) at 80°C. DETAILED DESCRIPTION

[0050] Example 1:

[0051]

[0052] (1) Preparation of docosanoyl β-alanine methyl ester (Intermediate 1)

[0053] Docosanoic acid (100 g, 0.29 mol) was placed in a 1000 mL three-necked flask, dichlorosulfoxide (42 g, 0.35 mol) was placed in a constant pressure dropping funnel, and the dichlorosulfoxide was slowly added dropwise at 70°C, with sodium hydroxide aqueous solution being used to absorb the acid gas generated, and the reaction was continued for 3 h until the system was clear and transparent and no acid gas was generated. Subsequently, dichlorosulfoxide was removed under reduced pressure to obtain a light yellow viscous liquid, which was docosanoyl chloride. Subsequently, β-alanine methyl ester hydrochloride (46.65 g, 0.33 mol) and triethylamine (100 g, 0.99 mol) were weighed into a 1000 mL three-necked flask, an appropriate amount of CH2Cl2was added, and stirring was performed to dissolve uniformly, and docosanoyl chloride (100 g, 0.28 mol) was slowly added dropwise under ice bath conditions, and after the addition was completed, the reaction was continued for 3 h. After the reaction was completed, the reaction system was extracted with hydrochloric acid aqueous solution three times, and the lower clear liquid was dried with an appropriate amount of anhydrous magnesium sulfate. Subsequently, filtration was performed, and CH2Cl2in the filtrate was removed under reduced pressure at 35°C to obtain a white solid, which was docosanoyl β-alanine methyl ester (110 g, 0.26 mol).

[0054] (2) Preparation of Intermediate 2

[0055] Weigh 40 g (0.39 mol) of N,N-dimethyl-1,3-propanediamine and 1 (110 g (0.26 mol) together and place them in a 500 mL round-bottom flask. React at 100 °C for 36 h. After the reaction is complete, allow it to stand at room temperature, recrystallize it three times with ethyl acetate / ethanol, and dry it to obtain a white powder, which is intermediate 2 (111 g).

[0056] (3) Preparation of novel ultra-long alkane chain bisquaternary ammonium salt surfactant CADQA-22

[0057] Finally, 63 g (0.24 mol) of 3-bromopropyltrimethylammonium bromide and 111 g (0.24 mol) of intermediate 2 were weighed and placed together in a 1000 mL round-bottom flask. An appropriate amount of anhydrous ethanol was added as solvent, and the mixture was reacted at 90 °C for 48 h. After the reaction was complete, the solvent was removed by rotary evaporation at 60 °C under reduced pressure. The mixture was then washed three times with ethanol / ethyl acetate and dried to obtain pure CADQA-22 as a white solid (145 g). The proton nuclear magnetic resonance spectrum of the obtained surfactant CADQA-22 is shown below. Figure 1 As shown. From Figure 1 It can be seen that the hydrogen shifts in the spectrum correspond one-to-one with the target product, indicating that the target product was obtained and its purity meets the requirements for subsequent testing.

[0058] Example 2:

[0059] Preparation of a heat-resistant thickened fracturing fluid

[0060] Add 0.74wt% CADQA-22 and 0.41wt% sodium palmitate (SP) to deionized water, stir at 60℃ for 20-60 minutes until well mixed, then place in an 80℃ constant temperature oven and let stand for 12 hours before removing; then let stand in a 25℃ constant temperature oven for 48 hours to obtain a heat-resistant thickened fracturing fluid.

[0061] The fracturing fluid obtained in Example 2 exhibited superior viscoelasticity in both 25°C and 80°C constant-temperature chambers, with the viscoelastic properties at 80°C being superior to those at 25°C. Its macroscopic state is as follows: Figure 3 As shown (left: 25℃, right: 80℃).

[0062] Cryo-transmission electron microscopy: The morphology of micelles formed by surfactant self-assembly in fracturing fluid was investigated using cryo-transmission electron microscopy. The Croy-TEM images are shown below. Figure 3 As shown (the left image is taken at 45000x and the right image is taken at 92000x), the results indicate that there are a large number of ultra-long worm micelles in the system. The average diameter of the worm micelles is about 6nm, and their length exceeds the observation range of electron microscopy.

[0063] Rheological property test: the viscosity of the fracturing fluid obtained in Example 2 at 25℃, 55℃ and 85℃ was measured as a function of shear rate, as shown in Figure 4 As shown in the figure, the zero shear viscosity η0 of the system does not decrease but increases with the increase of temperature, and the η0 at 25℃, 55℃ and 85℃ is 9997 mPa·s, 12846 mPa·s and 22045 mPa·s, respectively. It is worth noting that the viscosity retention rate of the fracturing fluid obtained in Example 2 at 55℃ is as high as 130%, and the viscosity retention rate at 85℃ is as high as 361%, which shows outstanding temperature resistance and heat thickening performance. (Viscosity retention rate: the ratio of viscosity at high temperature to viscosity at low temperature)

[0064] The dynamic rheological test shows the same response rule. Within the test range, the fracturing fluid obtained in Example 2 always shows a typical elastic gel state with a storage modulus G' greater than a loss modulus G", and the size of the storage modulus G' is almost not affected by the oscillation frequency, indicating that the elasticity of the system is strong and the internal mesostructure is stable. As shown in Figure 5 With the increase of temperature, the winding density of the worm-like micelles increases, which also proves that the fracturing fluid has not only excellent high temperature resistance, but also its viscoelasticity performance is significantly improved with the increase of temperature, which is very rare.

[0065] Example 3

[0066] Preparation of a salt-resistant and temperature-resistant heat thickening fracturing fluid

[0067] 0.74wt% CADQA-22, 0.41wt% sodium palmitate (SP) and 1wt% KCl were added to deionized water, and stirred at 60℃ for 20-60 minutes, uniformly mixed, then placed in a 80℃ constant temperature box for 12 hours, and then taken out; and then placed in a 25℃ constant temperature box for 48 hours to obtain a salt-resistant and temperature-resistant heat thickening fracturing fluid.

[0068] Rheological property test:

[0069] The viscosity of the fracturing fluid obtained in Example 3 at 25℃, 55℃ and 85℃ was measured as a function of shear rate, as shown in Figure 6 As shown in the figure, the zero shear viscosity of the system does not decrease but increases with the increase of temperature, and the η0 at 25℃, 55℃ and 85℃ is 15607 mPa·s, 49446 mPa·s and 60066 mPa·s, respectively, showing outstanding temperature resistance and heat thickening performance. At different temperatures, the viscosity of the fracturing fluid obtained in Example 3 is greater than that of Example 2, which shows that the fracturing fluid system has outstanding salt resistance, and the addition of KCl improves the original temperature resistance and heat thickening properties to some extent.

[0070] At 110s -1The viscosity of Example 3 was measured at different temperatures and the results are shown in Figure 1. Figure 7 As shown in Figure 1, the system exhibits a significant thermal thickening effect in the temperature range of 30-80℃, and the viscosity increases significantly with the increase of temperature, and the viscosity at 80℃ is as high as 107mPa·s, far exceeding that of other temperature-resistant fracturing fluids.

[0071] Suspended sand performance test: The sand-carrying capacity of the fracturing fluid obtained in Example 3 was evaluated by single-particle gravel settling method at ambient temperatures of 25℃, 60℃ and 85℃, respectively. The smaller the settling speed, the stronger the sand-carrying capacity of the fracturing fluid. In this experiment, 40-70 mesh fracturing fluid special ceramsite sand was used, and the test results are shown in Table 1. The test results at the three ambient temperatures are all much smaller than the standard (<5cm / min), and the sand settling speed gradually decreases with the increase of temperature, indicating that the sand-carrying capacity of the fracturing fluid significantly increases with the increase of temperature, which is consistent with the rheological property test data.

[0072] Table 1

[0073]

[0074] Comparative Example 1:

[0075] 0.74wt% octadecyltrimethylammonium bromide (OTAB) and 0.41wt% sodium palmitate (SP) were added to deionized water, stirred at 60℃ for 20-60 minutes, mixed uniformly, and then placed in an 80℃ constant temperature box for 12h. After taking out, it was observed that the system was still in an incomplete dissolved state. Then it was placed in a 25℃ constant temperature box for 48h, and the turbidity of the system was further enhanced, but the viscosity also increased significantly. The macroscopic image is shown in Figure 2. Figure 8

[0076] Rheological test: The viscosity of the composite system obtained in Comparative Example 1 was measured at a shear rate of 10s -1 The viscosity of the composite system obtained in Comparative Example 1 gradually decreased with the increase of temperature, as shown in Figure 3 (the test range was 25-85℃), and the viscosity η sharply decreased after reaching the critical temperature of 45℃, and finally stabilized at about 4mPa·s, indicating that the composite system obtained in Comparative Example 1 obviously does not have the potential to be used as a fracturing fluid. Figure 9

[0077] Comparative Example 2:

[0078] ​​To the deionized water, 0.74wt% octadecyl trimethyl ammonium bromide (OTAB), 0.41wt% sodium palmitate (SP), 1wt% KCl were added, stirred at 60℃ for 20-60min, mixed uniformly, then placed in an 80℃ constant temperature box for 12h, after taking out, it was observed that the system was still in an incomplete dissolution state; then placed in a 25℃ constant temperature box for 48h, the turbidity of the system was further enhanced, but the viscosity did not have a significant increase. The macroscopic graph is shown in Figure 8 .

[0079] Rheological test: at a shear rate of 10s -1 , the viscosity of the composite system obtained in Comparative Example 2 was measured as a function of temperature, as shown in Figure 9 . The viscosity of Comparative Example 2 as a function of temperature was the same as that of Comparative Example 1, and the viscosity η dropped sharply after 45℃, but the final viscosity was stabilized at about 11mPa·s, which indicated that the addition of KCl helped to improve the viscosity of the system, but Comparative Example 2 also did not have the potential to be used as a fracturing fluid.

[0080] In summary, OTAB and SP cannot form a stable viscoelastic solution, and the mixed solution also does not have temperature resistance or heat thickening performance, and the addition of KCl cannot change this fact, which is sufficient to show that the unique molecular structure of CADQA-22 makes the mixed aqueous solution with sodium palmitate (SP) have outstanding viscoelastic properties and temperature resistance and heat thickening ability.

[0081] Comparative Example 3:

[0082] Surfactant N 1 , N 1 , N 1 , N 3 , N 3 - pentamethyl-N3-(3-stearoylpropyl) propane-1,3-dibromide (abbreviated as C18-DQA) has the following structure:

[0083]

[0084] The surfactant C18-DQA can be prepared according to the existing patent document CN115537193A.

[0085] To the deionized water, 0.74wt% C18-DQA, 0.41wt% sodium palmitate (SP) were added, stirred at 60℃ for 20-60min, mixed uniformly, then placed in an 80℃ constant temperature box for 12h, after taking out, placed in a 25℃ constant temperature box for 48h, the composite system obtained in Comparative Example 3 remained clear and transparent at 80℃, but during the standing process at 25℃, crystals were found to precipitate, and the system became turbid, which indicated that C18-DQA could not form a stable viscoelastic solution with SP.

[0086] Rheology test: The solubility limit of the composite system of Comparative Example 3 was only measured at 45-80℃, the viscosity-temperature curve was measured at a shear rate of 10 s -1 As shown in Figure 3, the viscosity of the composite system of Comparative Example 3 gradually decreased with the increase of temperature, and did not have a thermal thickening behavior. Figure 10

[0087] As shown in Figure 3, the viscosity of the composite system of Comparative Example 3 gradually decreased with the increase of temperature, and did not have a thermal thickening behavior. Figure 11 As shown in Figure 3, the viscosity of the composite system of Comparative Example 3 gradually decreased with the increase of temperature, and did not have a thermal thickening behavior. -1 The zero shear viscosity η0 of Comparative Example 3 at 80℃ was 200 mPa·s, and the viscosity at a shear rate of 110 s was only 3.6 mPa·s, which did not meet the national standard.​

Claims

1. A surfactant for a temperature-resistant heat thickening fracturing fluid, characterized by, The structural formula of the surfactant is as follows:

2. A method of synthesizing the surfactant of claim 1, characterized by, The synthetic route is as follows: The method comprises the following steps: 1) Preparation of docosanoyl chloride: dichloro sulfoxide is slowly added to docosanoic acid, and the reaction is continued until the system is clear and transparent and no acid gas is generated, and then the dichloro sulfoxide is removed by rotary evaporation under reduced pressure to obtain docosanoyl chloride; 2) Synthesis of intermediate 1: β-alanine methyl ester hydrochloride and triethylamine are dissolved in CH2Cl2, and docosanoyl chloride is added dropwise in an ice bath, and the reaction is continued for 2-5 hours, and then crystallization treatment is performed after the reaction to obtain intermediate 1; 3) Synthesis of intermediate 2: N,N-dimethyl 1,3-propanediamine is reacted with intermediate 1 at 80-120 °C for 20-40 hours, and then recrystallization and drying are performed to obtain intermediate 2; 4) Synthesis of the surfactant: 3-bromo-propyl trimethyl ammonium bromide and intermediate 2 are dissolved in anhydrous ethanol, and the reaction is continued at 80-100 °C to obtain the surfactant.

3. A temperature resistant, heat thickening fracturing fluid, characterized in that, The surfactant comprises the surfactant of claim 1.

4. The thermally-tolerant thickening fracturing fluid of claim 3, wherein, The surfactant comprises the surfactant of claim 1.

5. The thermally thickening fracturing fluid of claim 4, wherein, The total mass concentration of the surfactant and sodium palmitate in the fracturing fluid is not less than 1 wt%.

6. The thermally thickening fracturing fluid of claim 5, wherein, The total mass concentration of the surfactant and sodium palmitate in the fracturing fluid is 1 wt%-2 wt%.

7. The temperature-tolerant thickening fracturing fluid according to any one of claims 3-6, characterized in that, The formula of the fracturing fluid comprises, in terms of mass fraction, 0.65%-0.77% of the surfactant of claim 1, 0.36%-0.43% of sodium palmitate, 0-2% of inorganic salt, and the balance being water.

8. A method of preparing the temperature resistant thermal thickening fracturing fluid of claim 7, characterized in that, The method is to add 0.36 wt%-0.43 wt% of sodium palmitate, 0.65 wt%-0.77 wt% of the surfactant of claim 1, and 0-2 wt% of inorganic salt to deionized water, and then mix well to obtain the fracturing fluid.

9. The surfactant of claim 1, or the heat-resistant heat-thickening fracturing fluid of any one of claims 3-7, is applied in the exploitation of oil and gas resources.

10. The surfactant of claim 1, or the heat-resistant heat-thickening fracturing fluid of any one of claims 3-7, is applied in the fracturing operation of high-temperature oil and gas reservoirs, shale oil exploitation, or oil and gas reservoirs with higher environmental protection requirements.

Images