Method for regulating and controlling supramolecular aggregation form to monomolecular form

Abstract

The invention discloses a method for regulating and controlling a supramolecular aggregation form to a monomolecular form, which is specifically implemented according to the following steps: step 1, compounding a long-chain primary amine surfactant and a nonionic surfactant in proportion to prepare a high-viscosity compound system; step 2, adding a sodium nitrite aqueous solution into the high-viscosity compound system prepared in the step 1, reacting, adjusting the pH value to an acidic condition, and uniformly stirring; and step 3, placing the system prepared in the step 2 in a constant-temperature water bath, and continuously stirring to obtain the product. Viscosity optimization of a high-viscosity compound system is achieved by adjusting the proportion, hydrophilic groups of the long-chain primary amine surfactant are eliminated by reacting with sodium nitrite, and the hydrophilic-oleophylic proportion of the long-chain primary amine surfactant is changed; the problem that an existing fracturing fluid is low in viscosity and poor in flowback effect is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of clean fracturing fluids and relates to a method for regulating the supramolecular aggregation morphology to the single-molecule morphology. Background Art

[0002] In the application of fracturing fluids in oil exploitation, long-chain primary amine surfactants have attracted much attention due to their excellent interfacial activity and high-temperature tolerance. In the literature "LEastoe, J.; Gold, S.; Rogers, S. E.; Paul, A.; Welton, T.; Heenan, R.K.; Grillo, I. Langmuir 2006, 22(24), 9960–9965. DOI: [10.1021 / la061303w]", Eastoe et al. adjusted the hydrophobic chain length of long-chain primary amine surfactants so that they could still form stable micelle structures at high temperatures (>80°C) and high-salt environments, meeting the requirements of fracturing fluids for carrying proppants with high-viscosity liquids.

[0003] In order to further improve the comprehensive performance of fracturing fluids, long-chain primary amine surfactants are often used in combination with non-ionic surfactants. In the existing literature "Song, P.; Xue, Z.; Wang, L. Energy&Fuels 2018, 32(3), 2873–2881. DOI: [10.1021 / acs.energyfuels.7b03276]", Song Panpan et al. formed a worm-like micelle system by mixing anionic and non-ionic surfactants. The viscosity of this system remained above 200 mPa·s at 120°C and high-salt conditions; the Zemb team also confirmed that the mixed system could significantly improve the densification degree of three-dimensional network-like aggregated micelles, and the viscosity of the system increased sharply to 500 mPa·s–2000 mPa·s, enhancing the suspension stability of proppants. However, the fluidity of both of the above two systems during the flowback stage was severely hindered due to their too high viscosities. Traditional viscosity reduction methods, by injecting low-salinity fluids for dilution or adding chemical triggers such as strong acids and reducing agents, can temporarily reduce the viscosity, but are prone to problems such as reservoir mineral dissolution and sulfide residues. The addition of additives significantly increases the operation cost, and the viscosity reduction effect is limited by the uncontrollability of formation temperature and ionic strength.

[0004] The gel-breaking methods of long-chain primary amine surfactants mainly focus on chemical triggering and physical regulation. For the chemical triggering gel-breaking method, such as adding strong acid to protonate the -NH2 group of primary amine, which weakens the micelle stability. Although the acid solution gel-breaking is fast and effective, it is easy to cause the dissolution of formation minerals (such as calcite, clay), resulting in damage to the reservoir permeability. For the physical regulation gel-breaking method, by injecting low salinity fluid to dilute the micelle concentration and reduce the viscosity. Although the dilution method is simple and easy to operate, the proppant settlement rate is still as high as 15% - 30%, and it is limited by the formation water ionic strength. Existing fracturing fluids have not solved the core contradiction of "high viscosity for sand carrying and low viscosity for flowback". The low viscosity flowback effect is poor, the operation is complex, and the process cost is high. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for regulating the supramolecular aggregation morphology to the single molecule morphology, which solves the problem of poor low viscosity flowback effect existing in existing fracturing fluids.

[0006] One technical solution adopted by the present invention is a method for regulating the supramolecular aggregation morphology to the single molecule morphology, which is specifically implemented according to the following steps: Step 1, compound the long-chain primary amine surfactant and the non-ionic surfactant in proportion to prepare a high-viscosity compound system; Step 2, add an aqueous sodium nitrite solution to the high-viscosity compound system prepared in Step 1, react to adjust the pH to acidic conditions, and stir evenly; Step 3, place the system prepared in Step 2 in a constant temperature water bath and continuously stir to obtain it.

[0007] The characteristics of the present invention are as follows: The long-chain primary amine surfactant and the non-ionic surfactant are weighed according to a mass ratio of 1:1 to 3:1.

[0008] Under the room temperature condition of 20°C to 25°C, add the long-chain primary amine surfactant and the non-ionic surfactant into a stirring container and stir. Use a magnetic stirrer or a mechanical stirrer, and the stirrer speed is 300 rpm to 500 rpm, and continuously stir for 10 min to 30 min.

[0009] The long-chain primary amine surfactant has a straight-chain or branched-chain primary amine and its derivatives with a chain length of C 12 ~C 22 and any one of dodecylamine, isohexadecylamine, docosylamine is adopted.

[0010] The non-ionic surfactant is a polyoxyethylene ether surfactant.

[0011] The polyoxyethylene ether surfactant adopts any one of polyoxyethylene lauryl ether and nonylphenol polyoxyethylene ether.

[0012] After the long-chain primary amine surfactant is compounded with the non-ionic surfactant, the viscosity shows a high-viscosity compounding system of 500 mPa·s to 2000 mPa·s.

[0013] In step 2, the reaction conditions are under acidic conditions with pH = 3 - 4, the temperature is controlled at 40°C - 50°C, and the reaction time is 20 min - 30 min. In step 2, sodium nitrite is prepared as a 10% aqueous solution, and the molar ratio of the long-chain primary amine surfactant to sodium nitrite is 1:1.2.

[0014] The system prepared in step 2 is placed in a constant temperature water bath at 20°C - 50°C and stirred for 5 min - 30 min.

[0015] The beneficial effects of the present invention are as follows: The method for regulating the supramolecular aggregation morphology to the single-molecule morphology of the present invention precisely controls the transformation of micelles from the supramolecular aggregation morphology to the single-molecule morphology by regulating the hydrophilic group structure of the long-chain primary amine surfactant, realizing the rapid gel breaking of the fracturing fluid and significantly reducing the viscosity of the flowback fluid. The present invention realizes self-gel breaking through molecular structure design, simplifies the construction process, improves the operation efficiency, is applicable to compounding systems of various long-chain primary amine surfactants and non-ionic surfactants, and has excellent gel breaking methods and post-gel breaking properties for the primary amine compounding system. As an efficient, stable and low-cost viscosity reduction method, it has important industrial application prospects. Detailed implementation manners

[0016] The present invention will be described in detail below in conjunction with the specific implementation manners.

[0017] Example 1 The method for regulating the supramolecular aggregation morphology to the single-molecule morphology of the present invention is specifically implemented according to the following steps: Step 1, compound the long-chain primary amine surfactant and the non-ionic surfactant in proportion to prepare a high-viscosity compounding system. Step 2, add an aqueous solution of sodium nitrite to the high-viscosity compounding system prepared in step 1, react to adjust the pH to acidic conditions, and stir evenly. Step 3, place the system prepared in step 2 in a constant temperature water bath and continuously stir to obtain the product.

[0018] Example 2 The method for regulating the supramolecular aggregation morphology to the single-molecule morphology of the present invention is specifically implemented according to the following steps: Step 1, compound the long-chain primary amine surfactant and the non-ionic surfactant in proportion to prepare a high-viscosity compounding system. Weigh the long-chain primary amine surfactant and the non-ionic surfactant according to a mass ratio of 1:1 to 3:1. At room temperature of 20°C to 25°C, add the long-chain primary amine surfactant and the non-ionic surfactant to a stirring container and stir. Then add deionized water. Use a magnetic stirrer or a mechanical stirrer with a stirrer speed of 300 rpm to 500 rpm and continuously stir for 5 min to 30 min.

[0019] The long-chain primary amine surfactant has a chain length of C 12 ~C 22 linear or branched primary amines and derivatives, and any one of dodecyl primary amine, isohexadecyl primary amine, and docosyl primary amine is used.

[0020] The non-ionic surfactant is a polyoxyethylene ether surfactant, and any one of polyoxyethylene lauryl ether and nonylphenol polyoxyethylene ether is used.

[0021] After the long-chain primary amine surfactant and the non-ionic surfactant are compounded, due to the change of the micelle morphology from a single-molecule form to a super-aggregated molecular structure, the viscosity shows a high-viscosity compounding system of 500 mPa·s to 2000 mPa·s.

[0022] Step 2: Add an aqueous solution of sodium nitrite to the high-viscosity compounding system prepared in Step 1, adjust the reaction to an acidic condition by stirring evenly; The reaction condition is under an acidic condition of pH = 3 to 4, control the temperature at 40°C to 50°C, and the reaction time is 20 min to 30 min; configure sodium nitrite into a 10% aqueous solution, and the molar ratio of the long-chain primary amine surfactant to sodium nitrite is 1:1.2.

[0023] Step 3: Place the system prepared in Step 2 in a constant temperature water bath and continuously stir; place the system prepared in Step 2 in a constant temperature water bath of 20°C - 50°C and stir for 5 min - 30 min.

[0024] The method for regulating the supramolecular aggregation morphology to a single-molecule morphology in the present invention is to change the ratio of hydrophilic groups to hydrophobic groups in the high-viscosity compounding system by adjusting the hydrophilic group structure of the surfactant in the high-viscosity compounding system, thereby regulating the aggregation morphology of the micelles and obtaining a method for reducing the viscosity of the high-viscosity compounding system. By chemically reacting to eliminate the hydrophilic groups of the long-chain primary amine surfactant, the micelles are changed from a tight rod-like structure or a three-dimensional network structure to a single-molecule dispersed state, thereby effectively reducing the system viscosity. The present invention realizes the regulation of the micelle morphology by eliminating the hydrophilic groups in the long-chain primary amine surfactant and effectively reduces the system viscosity.

[0025] Example 3 The method for regulating the supramolecular aggregation morphology to a single-molecule morphology in the present invention is specifically implemented according to the following steps: Step 1: Mix a long-chain primary amine surfactant and a non-ionic surfactant in proportion to prepare a highly viscous mixed system. Specifically in Step 1, the long-chain primary amine surfactant is selected as docosylamine; the non-ionic surfactant is selected as polyoxyethylene lauryl ether. Weigh 1.0 g of docosylamine and 1.0 g of polyoxyethylene lauryl ether, mix them in a mass ratio of 1:1, add 50 mL of deionized water, and stir for 5 min under magnetic stirring at 500 rpm to form a uniform highly viscous mixed system.

[0026] Step 2: Slowly add 4.5 ml of 10% sodium nitrite aqueous solution to the highly viscous mixed system prepared in Step 1, and adjust the pH to 3 with dilute hydrochloric acid; after stirring evenly; Step 3: Place the system prepared in Step 2 in a constant temperature water bath at 20 °C and continue to stir for 10 min. The system gradually becomes clear and the viscosity significantly decreases.

[0027] Example 4 The method for regulating the supramolecular aggregation morphology to the single-molecule morphology of the present invention is specifically implemented according to the following steps: Step 1: Mix a long-chain primary amine surfactant and a non-ionic surfactant in proportion to prepare a highly viscous mixed system. Specifically in Step 1, the long-chain primary amine surfactant is selected as isohexadecylamine; the non-ionic surfactant is selected as polyoxyethylene lauryl ether. Weigh 2.0 g of isohexadecylamine and 1.0 g of polyoxyethylene lauryl ether, mix them in a mass ratio of 2:1, add 50 mL of deionized water, and stir for 5 min under magnetic stirring at 300 rpm to form a uniform and transparent highly viscous mixed system.

[0028] Step 2: Add 6.9 ml of 10% sodium nitrite aqueous solution to the solution of the highly viscous mixed system prepared in Step 1, adjust the pH to 3 with dilute sulfuric acid, and stir evenly; Step 3: Transfer the system prepared in Step 2 to a constant temperature water bath at 30 °C and stir for 20 min. The system changes from the original milky white to light yellow, indicating that the micelle structure has changed and the viscosity has decreased.

[0029] Example 5 The method for regulating the supramolecular aggregation morphology to the single-molecule morphology of the present invention is specifically implemented according to the following steps: Step 1: Mix a long-chain primary amine surfactant and a non-ionic surfactant in proportion to prepare a highly viscous mixed system. Step 1 specifically is that the long-chain primary amine surfactant is selected as docosyl primary amine; the non-ionic surfactant is selected as nonylphenol polyoxyethylene ether; 3.0 g of docosyl primary amine and 1.0 g of nonylphenol polyoxyethylene ether are weighed, and the two are mixed at a mass ratio of 3:1, 50 mL of deionized water is added, and under magnetic stirring of a magnetic stirrer at a rotation speed of 500 rpm, it is stirred for 10 min to obtain a uniform and highly viscous compound system solution.

[0030] Step 2, slowly add 7.6 ml of 10% sodium nitrite aqueous solution dropwise to the highly viscous compound system solution prepared in Step 1, adjust the pH = 4 with dilute sulfuric acid, and stir evenly; Step 3, transfer the system prepared in Step 2 to a constant temperature water bath at 40 °C and stir for 30 min. The color of the system gradually becomes lighter, the micelles are gradually dissociated, and the fluidity is enhanced.

[0031] Example 6 The method for regulating the supramolecular aggregation morphology to the single-molecule morphology of the present invention is specifically implemented according to the following steps: Step 1, compound the long-chain primary amine surfactant and the non-ionic surfactant in proportion to prepare a highly viscous compound system; Step 1 specifically is that the long-chain primary amine surfactant is selected as dodecyl primary amine; the non-ionic surfactant is selected as polyoxyethylene lauryl ether; 1.0 g of dodecyl primary amine and 1.0 g of polyoxyethylene lauryl ether are weighed, and the two are mixed at a mass ratio of 1:1, 50 mL of deionized water is added, and under magnetic stirring of a magnetic stirrer at a rotation speed of 500 rpm, it is stirred for 5 min to form a uniform and transparent system, and a highly viscous compound system solution is obtained.

[0032] Step 2, gradually add 4.5 ml of 10% sodium nitrite aqueous solution dropwise to the highly viscous compound system solution prepared in Step 1, adjust the pH = 4 with dilute sulfuric acid, and stir evenly; Step 3, transfer the system prepared in Step 2 to a constant temperature water bath at 50 °C and stir for 10 min. The color of the system gradually becomes lighter, the micelles are gradually dissociated, and the fluidity is enhanced.

[0033] Example 7 The method for regulating the supramolecular aggregation morphology to the single-molecule morphology of the present invention is specifically implemented according to the following steps: Step 1, compound the long-chain primary amine surfactant and the non-ionic surfactant in proportion to prepare a highly viscous compound system; Step 1 specifically involves selecting docosylamine as the long-chain primary amine surfactant and nonylphenol polyoxyethylene ether as the non-ionic surfactant. Weigh 3.0 g of docosylamine and 1.0 g of nonylphenol polyoxyethylene ether, mix them in a mass ratio of 3:1, add 50 mL of deionized water, and stir for 10 min under magnetic stirring at a speed of 500 rpm to form a stable high-viscosity compound system.

[0034] Step 2: Slowly add 7.6 ml of 10% sodium nitrite aqueous solution to the high-viscosity compound system prepared in Step 1, adjust the pH to 5 with phosphoric acid, and stir evenly. Step 3: Place the system prepared in Step 2 in a constant temperature water bath at 50°C and continue stirring for 30 min. The color of the system becomes lighter, the super-aggregation structure is completely destroyed, the viscosity decreases significantly, and the system tends to be in a single-molecule dispersion state.

[0035] Before and after the regulation of the compound systems obtained in Examples 3 - 7, dynamic light scattering (DLS) monitoring and viscosity tests were carried out. According to the experimental data analysis of Examples 3 - 7, after the long-chain primary amine surfactant is compounded with the non-ionic surfactant, due to the super-aggregation morphology of the micelle structure, its initial viscosity is relatively high (500 - 2000 mPa·s). After the viscosity reduction reaction induced by sodium nitrite, the micelles in the system dissociate, and the viscosity is significantly reduced to less than 10 mPa·s, meeting the requirements of gel breaking and viscosity reduction. Different combinations of primary amines and non-ionic surfactants have different initial viscosities, but the final viscosity is reduced to less than 10 mPa·s.

[0036] The method for regulating the supramolecular aggregation morphology to a single-molecule morphology in the present invention precisely controls the transformation of the micelle aggregation morphology from the supramolecular aggregation morphology to the single-molecule morphology by adjusting the hydrophilic group structure of the long-chain primary amine surfactant, thereby effectively reducing the viscosity of the fracturing fluid and achieving gel breaking. Under acidic conditions, the long-chain primary amine surfactant reacts with sodium nitrite to eliminate the hydrophilic group of the long-chain primary amine surfactant, change the hydrophilic-lipophilic ratio of the long-chain primary amine surfactant, and transform the micelle structure of the compound system from a rod-like structure or a three-dimensional network structure to a single-molecule dispersion state, thereby reducing the viscosity of the system. The micelles of the high-viscosity compound system change from a tight rod-like micelle structure to a single-molecule morphology, and the viscosity reduction amplitude can reach more than 90%, improving the fluidity.

[0037] The gel breaking of the fracturing fluid in the present invention does not rely on a large amount of chemical solvents or diluents, avoiding environmental pollution. It can quickly and completely break the gel on the premise of not damaging the performance of the fracturing fluid. The backflow fluid after gel breaking can be directly used, reducing the harm to the formation, meeting the requirements of green environmental protection and sustainable development, and providing a more environmentally friendly solution for the oil exploitation industry.

Claims

1. A method for regulating the supramolecular aggregation morphology to a single-molecule morphology, characterized in that, The implementation is carried out according to the following steps: Step 1: Compound a long-chain primary amine surfactant and a non-ionic surfactant in proportion to prepare a high-viscosity compound system; Step 2: Add an aqueous sodium nitrite solution to the high-viscosity compound system prepared in Step 1, adjust the reaction pH to acidic conditions, and stir evenly; Step 3: Place the system prepared in Step 2 in a constant-temperature water bath and continuously stir to obtain the product.

2. The method for regulating the supramolecular aggregation morphology to the single-molecule morphology according to claim 1, wherein The long-chain primary amine surfactant and the non-ionic surfactant are weighed in a mass ratio of 1:1 to 3:

1.

3. The method for regulating the supramolecular aggregation morphology to the single-molecule morphology according to claim 1, characterized in that, Under the room temperature condition of 20°C to 25°C, add the long-chain primary amine surfactant and the non-ionic surfactant to a stirring container and stir. Use a magnetic stirrer or a mechanical stirrer, with the stirrer speed being 300 rpm to 500 rpm, and continuously stir for 10 min to 30 min.

4. The method for controlling supramolecular aggregation to unimolecular morphology according to claim 1, characterized in that: The chain length of the long-chain primary amine surfactant is C 12 ~C 22 The straight-chain or branched primary amine and its derivatives are any one of dodecyl primary amine, isohexadecyl primary amine and behenyl primary amine.

5. The method for regulating the supramolecular aggregation morphology to the single-molecule morphology according to claim 1, wherein The non-ionic surfactant is a polyoxyethylene ether surfactant.

6. The method for regulating the supramolecular aggregation morphology to the single-molecule morphology according to claim 5, characterized in that, The polyoxyethylene ether surfactant adopts any one of polyoxyethylene lauryl ether and nonylphenol polyoxyethylene ether.

7. The method for regulating the supramolecular aggregation morphology to the single-molecule morphology according to claim 1, wherein After the long-chain primary amine surfactant and the non-ionic surfactant are compounded, the viscosity shows a high-viscosity compound system of 500 mPa·s to 2000 mPa·s.

8. The method for regulating the supramolecular aggregation morphology to the single-molecule morphology according to claim 1, wherein In Step 2, the reaction conditions are under acidic conditions with pH = 3 to 4, the temperature is controlled at 40°C to 50°C, and the reaction time is 20 min to 30 min.

9. The method for regulating the supramolecular aggregation morphology to the single-molecule morphology according to claim 1, wherein In Step 2, sodium nitrite is configured into a 10% aqueous solution, and the molar ratio of the long-chain primary amine surfactant to sodium nitrite is 1:1.

2.

10. The method for regulating the supramolecular aggregation morphology to the single-molecule morphology according to claim 1, wherein, Place the system prepared in Step 2 in a constant-temperature water bath at 20°C - 50°C and stir for 5 min - 30 min.