A supramolecular fracturing fluid and preparation method thereof

Abstract

The invention relates to the technical field of fracturing fluid preparation, and in particular to a supramolecular fracturing fluid and a preparation method thereof. The hydrophobic association and electrostatic action between sodium salicylate and a surfactant in a crosslinking agent provided by the invention can form micellar gel, and a thickener can be embedded in the micellar gel through the association of hydrophobic groups to form a supramolecular network, thereby enhancing the network structure strength of the fracturing fluid, improving the rheological properties of the supramolecular fracturing fluid, and having a stronger sand suspension capacity. In addition, a solubilizing agent and a co-solvent reduce the decrease in water solubility caused by a large number of hydrophobic groups contained in the thickener, and sodium dodecylbenzene sulfonate can inhibit a crosslinking reaction to a certain extent through the shielding effect and steric hindrance effect of metal cations, prolonging the gelling time of the system, effectively solving the problem of large wellbore friction during ultra-deep fracturing, and effectively reducing shear damage, thereby having broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of fracturing fluid preparation, and in particular to a supramolecular fracturing fluid and a preparation method thereof. Background Art

[0002] Hot dry rock is a dense rock mass without water and steam, mainly distributed below 3,000 meters in the stratum. At this time, the temperature of the hot dry rock mass is about 150-160℃. In conventional undeveloped hot dry rock strata, the geothermal energy stored in the rock cannot be directly extracted. This is because the natural fracture network in the reservoir of the hot dry rock high-temperature strata is extremely scarce, resulting in poor connectivity of the reservoir fractures. If the high-temperature geothermal energy stored in the hot dry rock is to be developed and utilized, it is necessary to establish an enhanced geothermal system, that is, to change the extremely low permeability rock formation conditions through artificial means such as hydraulic fracturing or blasting, thereby forming a seepage channel with high permeability, and using the low-temperature working fluid injected into the stratum to replace the huge heat in the reservoir of the hot dry rock from the underground.

[0003] As one of the hot dry rock reservoir transformation and treatment technologies, hydraulic fracturing technology has been used in the transformation of low-permeability hot dry rock reservoirs for decades. The principle of this method is to inject high-pressure water medium into the closed wellbore of the injection well to cause the rock formation to break. The fracturing medium then penetrates into the cracks to expand the formed cracks. The high-pressure fracturing medium is injected repeatedly to form a larger crack network in the hot dry rock reservoir, thereby connecting the injection well and the production well. At the same time, the fracturing fluid is a crucial factor in the fracturing reservoir transformation process. It can transmit pressure, break the formation, extend cracks, and carry proppants into the cracks to prevent the cracks from closing, thereby effectively improving the seepage conditions and increasing the heat production of a single well.

[0004] According to the summary of on-site construction experience, in order to meet the needs of on-site fracturing construction, the fracturing fluid must have the following properties: good viscoelasticity to ensure the effective suspension of the fracturing fluid and the carrying of proppants into the cracks, good compatibility with reservoir rocks and formation fluids, low filtration loss to reduce matrix damage, good drag reduction rate to avoid excessive pump pressure to improve construction safety and success rate, and to achieve large-volume fracturing construction, easy backflow and low residue after construction to avoid secondary pollution of the reservoir, good temperature and shear resistance to avoid the viscoelasticity of the fracturing fluid being reduced to the point where it cannot suspend and carry proppants during high temperature and high-speed flow in the formation.

[0005] Traditional fracturing fluids often contain a large amount of polymers to increase their viscosity, help carry sand particles into cracks, thereby preventing the cracks from closing and keeping them open for oil and gas flow. For example, patent document CN114805115B discloses a temperature-resistant dihydroxy cationic viscoelastic surfactant and its preparation method, fracturing fluid and its application. The invention designs a double benzene ring structure, a double hydroxyl structure and a double tail structure in the surfactant molecular structure to obtain a fracturing fluid with good temperature resistance and shear resistance. However, this type of polymer still has the problem of "high agent concentration and high wellbore friction" in actual application.

[0006] Therefore, according to the above-mentioned related technologies, it is urgent to develop a supramolecular fracturing fluid and a preparation method thereof. Summary of the invention

[0007] In view of this, the purpose of the present invention is to provide a supramolecular fracturing fluid and a preparation method thereof, so as to solve the problem of high concentration of polymer fracturing fluid in practical application in the prior art.

[0008] Based on the above objectives, the present invention provides a supramolecular fracturing fluid and a preparation method thereof.

[0009] A supramolecular fracturing fluid comprises the following raw materials in parts by weight: 80-90 parts of a thickener, 1-3 parts of a solubilizer, 3-5 parts of a cosolvent, and 50-60 parts of a crosslinking agent;

[0010] The thickener is prepared from the reaction product of polyethyleneimine, acrylamide, allyl chloride and long-chain alkyl tertiary amine;

[0011] The mass ratio of the reaction product of polyethyleneimine, acrylamide, allyl chloride and long carbon chain alkyl tertiary amine is 2-4:21.32-35.54:2-3;

[0012] The cross-linking agent is prepared from potassium chloride, sodium salicylate and a surfactant;

[0013] The mass ratio of potassium chloride, sodium salicylate and surfactant is 25-30:20-24:5-6.

[0014] Preferably, the preparation process of the reaction product of allyl chloride and long carbon chain alkyl tertiary amine is as follows:

[0015] Add allyl chloride and long-chain alkyl tertiary amine into acetone, react at 45-50° C. for 22-24 hours under nitrogen atmosphere, rotary evaporate, collect samples, and vacuum dry to obtain the reaction product of allyl chloride and long-chain alkyl tertiary amine.

[0016] Preferably, the molar ratio of the allyl chloride to the long-chain alkyl tertiary amine is 0.019-0.026:0.019-0.026, and the dosage ratio of the allyl chloride to acetone is 0.019-0.026 mol:15-18 mL.

[0017] Preferably, the preparation process of the thickener is as follows:

[0018] Step S1. Add polyethyleneimine into deionized water and stir magnetically for 60 hours to obtain a mixed solution A;

[0019] Step S2. adding the reaction product of the crosslinking agent, acrylamide, allyl chloride and long-chain alkyl tertiary amine into deionized water, and ultrasonically treating for 5-8 minutes to obtain a mixed solution B;

[0020] Step S3. Mix the mixed solution A and the mixed solution B evenly, add the initiator and the co-initiator under nitrogen, and react at 30-35° C. for 10-12 hours to obtain a thickener.

[0021] Preferably, the dosage ratio of polyethyleneimine to deionized water in step S1 is 2-4 g: 100-110 mL.

[0022] Preferably, the mass ratio of the reaction product of the cross-linking agent, acrylamide, allyl chloride and long-chain alkyl tertiary amine in step S2 is 0.8-1:21.32-35.54:2-3, and the cross-linking agent in step S2 is N,N-dimethylacrylamide.

[0023] Preferably, in step S2, the usage ratio of acrylamide to deionized water is 21.32-35.54 g: 100-110 mL, and the molecular weight of polyethyleneimine is 70000-80000 g / mol.

[0024] Preferably, in step S3, the volumes of the mixed solution A, the mixed solution B, the initiator and the co-initiator are 100-110 mL: 1-3 mL: 30-35 μL, the initiator is potassium persulfate, and the co-initiator is N', N', N, N-tetramethylethylenediamine.

[0025] Preferably, the solubilizer is octadecyl hydroxypropyl sulfobetaine, the cosolvent is β-cyclodextrin, and the surfactant is sodium dodecylbenzenesulfonate.

[0026] A method for preparing a supramolecular fracturing fluid comprises the following steps:

[0027] The thickener, solubilizer, co-solvent and cross-linking agent are mixed in a stirrer and stirred at a rotation speed of 1000-1500 rpm for 18-22 minutes to obtain a supramolecular fracturing fluid.

[0028] Beneficial effects of the present invention:

[0029] The hydrophobic association and electrostatic action between the sodium salicylate and the surfactant in the cross-linking agent provided by the present invention can form micellar gel, which is then compounded with a thickener. The hydrophobic long chains in the reaction product of a relatively small amount of polyethyleneimine, a relatively large amount of acrylamide segments, and a relatively small amount of allyl chloride and a long-chain alkyl tertiary amine can be embedded in the micellar gel through the association of hydrophobic groups to form a strongly branched supramolecular network, which can enhance the network structure strength of the fracturing fluid, improve the rheological properties of the supramolecular fracturing fluid, and enable the supramolecular fracturing fluid to have a stronger sand suspension capacity.

[0030] The solubilizer and cosolvent provided by the present invention minimize the decrease in water solubility caused by a large number of hydrophobic groups contained in the thickener, and ensure the solution structure capacity while allowing the polymer thickener molecular chain to contain as many water-soluble structural units as possible. In addition, the sodium ions and long alkyl sulfonate ions ionized from the sodium dodecylbenzene sulfonate surfactant can inhibit the cross-linking reaction to a certain extent through the shielding effect and steric hindrance effect of the metal cations, and the potassium chloride introduced into the compound cross-linking agent can prolong the gelation time, effectively solve the problem of large wellbore friction during ultra-deep fracturing, and effectively reduce shear damage, thereby having broad application prospects. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0032] The sources and properties of some of the raw materials used in the present invention are as follows:

[0033] Octadecylhydroxypropyl sulfobetaine was chemically pure and purchased from Suzhou Weidu Chemical Co., Ltd.;

[0034] Hexadecyltrimethylammonium bromide was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0035] Sodium dodecylbenzenesulfonate was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0036] Sodium salicylate was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0037] Embodiment 1: A method for preparing a supramolecular fracturing fluid comprises the following steps:

[0038] S1. Add 0.019 mol of allyl chloride and 0.019 mol of long-chain alkyl tertiary amine into 15 mL of acetone, react at 45°C for 22 h under a nitrogen atmosphere, rotary evaporate, collect the sample, and vacuum dry to obtain a reaction product of allyl chloride and long-chain alkyl tertiary amine;

[0039] S2. Add 2 g of polyethyleneimine to 100 mL of deionized water and stir magnetically for 60 h to obtain a mixed solution A;

[0040] S3. 0.8 g of N, N-dimethylacrylamide, 21.32 g of acrylamide and 2 g of the reaction product of allyl chloride and a long-chain alkyl tertiary amine were added to deionized water and ultrasonically treated for 5 min to obtain a mixed solution B;

[0041] S4. 100 mL of mixed solution A and 100 mL of mixed solution B were mixed evenly, 1 mL of potassium persulfate and 30 μL of N', N', N, N-tetramethylethylenediamine were added under a nitrogen atmosphere, and the mixture was reacted at 30 ° C for 10 h to obtain a thickening agent;

[0042] S5. 25 g of potassium chloride, 20 g of sodium salicylate and 5 g of sodium dodecylbenzene sulfonate were mixed to obtain a crosslinking agent;

[0043] S6. 80 g of a thickener, 1 g of octadecylhydroxypropyl sulfobetaine, 3 g of β-cyclodextrin and 50 g of a cross-linking agent were mixed in a stirrer and stirred at a rotation speed of 1000 rpm for 18 min to obtain a supramolecular fracturing fluid.

[0044] Embodiment 2: A method for preparing a supramolecular fracturing fluid comprises the following steps:

[0045] S1. Add 0.02 mol of allyl chloride and 0.02 mol of long-chain alkyl tertiary amine into 16 mL of acetone, react at 46 °C for 23 h under nitrogen atmosphere, rotary evaporate, collect the sample, and vacuum dry to obtain the reaction product of allyl chloride and long-chain alkyl tertiary amine;

[0046] S2. Add 3 g of polyethyleneimine to 102 mL of deionized water and stir magnetically for 60 h to obtain a mixed solution A;

[0047] S3. 0.9 g N, N-dimethylacrylamide, 25 g acrylamide and 2.2 g of the reaction product of allyl chloride and a long-chain alkyl tertiary amine were added to deionized water and ultrasonically treated for 6 min to obtain a mixed solution B;

[0048] S4. 102 mL of mixed solution A and 102 mL of mixed solution B were mixed evenly, 1.63 mL of potassium persulfate and 32 μL of N', N', N, N-tetramethylethylenediamine were added under nitrogen, and the mixture was reacted at 32° C. for 11 h to obtain a thickening agent;

[0049] S5. 26 g of potassium chloride, 21 g of sodium salicylate and 5.2 g of sodium dodecylbenzene sulfonate were mixed to obtain a crosslinking agent;

[0050] S6. 82 g of a thickener, 2 g of octadecylhydroxypropyl sulfobetaine, 4 g of β-cyclodextrin and 52 g of a cross-linking agent were mixed in a stirrer and stirred at a rotation speed of 1100 rpm for 19 min to obtain a supramolecular fracturing fluid.

[0051] Embodiment 3: A method for preparing a supramolecular fracturing fluid comprises the following steps:

[0052] S1. Add 0.021 mol of allyl chloride and 0.021 mol of long-chain alkyl tertiary amine into 17 mL of acetone, react at 47 °C for 24 h under nitrogen atmosphere, rotary evaporate, collect the sample, and vacuum dry to obtain the reaction product of allyl chloride and long-chain alkyl tertiary amine;

[0053] S2. Add 4 g of polyethyleneimine to 108 mL of deionized water and stir magnetically for 60 h to obtain a mixed solution A;

[0054] S3. 1 g of N, N-dimethylacrylamide, 27 g of acrylamide and 2.4 g of the reaction product of allyl chloride and a long-chain alkyl tertiary amine were added to deionized water and ultrasonically treated for 7 min to obtain a mixed solution B;

[0055] S4. 108 mL of mixed solution A and 108 mL of mixed solution B were mixed evenly, 2 mL of potassium persulfate and 33 μL of N', N', N, N-tetramethylethylenediamine were added under nitrogen, and the mixture was reacted at 33° C. for 12 h to obtain a thickener;

[0056] S5. 27g of potassium chloride, 22g of sodium salicylate and 5.5g of sodium dodecylbenzene sulfonate were mixed to obtain a crosslinking agent;

[0057] S6. 86 g of a thickener, 3 g of octadecylhydroxypropyl sulfobetaine, 5 g of β-cyclodextrin and 56 g of a cross-linking agent were mixed in a stirrer and stirred at a rotation speed of 1200 rpm for 20 min to obtain a supramolecular fracturing fluid.

[0058] Embodiment 4: A method for preparing a supramolecular fracturing fluid comprises the following steps:

[0059] S1. Add 0.022 mol of allyl chloride and 0.022 mol of long-chain alkyl tertiary amine into 18 mL of acetone, react at 49 °C for 23 h under nitrogen atmosphere, rotary evaporate, collect the sample, and vacuum dry to obtain the reaction product of allyl chloride and long-chain alkyl tertiary amine;

[0060] S2. Add 3 g of polyethyleneimine to 106 mL of deionized water and stir magnetically for 60 h to obtain a mixed solution A;

[0061] S3. 0.95 g of N, N-dimethylacrylamide, 30 g of acrylamide and 2.6 g of the reaction product of allyl chloride and a long-chain alkyl tertiary amine were added to deionized water and ultrasonically treated for 6 min to obtain a mixed solution B;

[0062] S4. 106 mL of mixed solution A and 106 mL of mixed solution B were mixed evenly, 2.8 mL of potassium persulfate and 34 μL of N', N', N, N-tetramethylethylenediamine were added under nitrogen, and the mixture was reacted at 34° C. for 11 h to obtain a thickening agent;

[0063] S5. 28g of potassium chloride, 23g of sodium salicylate and 5.9g of sodium dodecylbenzene sulfonate were mixed to obtain a cross-linking agent;

[0064] S6. 88 g of a thickener, 2 g of octadecylhydroxypropyl sulfobetaine, 4 g of β-cyclodextrin and 59 g of a cross-linking agent were mixed in a stirrer and stirred at a rotation speed of 1300 rpm for 21 min to obtain a supramolecular fracturing fluid.

[0065] Embodiment 5: A method for preparing a supramolecular fracturing fluid comprises the following steps:

[0066] S1. Add 0.026 mol of allyl chloride and 0.026 mol of long-chain alkyl tertiary amine into 17 mL of acetone, react at 50 °C for 24 h under nitrogen atmosphere, rotary evaporate, collect the sample, and vacuum dry to obtain the reaction product of allyl chloride and long-chain alkyl tertiary amine;

[0067] S2. 4 g of polyethyleneimine was added to 110 mL of deionized water and magnetically stirred for 60 h to obtain a mixed solution A;

[0068] S3. 1 g of N, N-dimethylacrylamide, 35.54 g of acrylamide and 3 g of the reaction product of allyl chloride and a long-chain alkyl tertiary amine were added to deionized water and ultrasonically treated for 8 min to obtain a mixed solution B;

[0069] S4. 110 mL of mixed solution A and 110 mL of mixed solution B were mixed evenly, 3 mL of potassium persulfate and 35 μL of N', N', N, N-tetramethylethylenediamine were added under nitrogen, and the mixture was reacted at 35 ° C for 10 h to obtain a thickening agent;

[0070] S5. 30 g of potassium chloride, 24 g of sodium salicylate and 6 g of sodium dodecylbenzene sulfonate were mixed to obtain a crosslinking agent;

[0071] S6. 90 g of a thickener, 3 g of octadecylhydroxypropyl sulfobetaine, 3 g of β-cyclodextrin and 60 g of a cross-linking agent were mixed in a stirrer and stirred at a rotation speed of 1500 rpm for 22 min to obtain a supramolecular fracturing fluid.

[0072] Comparative Example 1:

[0073] Compared with Example 1, this comparative example does not add polyethyleneimine during the preparation of the thickener, and the remaining steps and parameters are the same, which will not be repeated in this comparative example. Finally, a supramolecular fracturing fluid is obtained.

[0074] Comparative Example 2:

[0075] Compared with Example 1, the reaction product of allyl chloride and long-chain alkyl tertiary amine was not added during the preparation of the thickener in this comparative example. The remaining steps and parameters were the same and will not be repeated in this comparative example. Finally, a supramolecular fracturing fluid was obtained.

[0076] Comparative Example 3:

[0077] Compared with Example 1, acrylamide was not added in the preparation process of the thickener in this comparative example, and the remaining steps and parameters were the same, which will not be repeated in this comparative example. Finally, a supramolecular fracturing fluid was obtained.

[0078] Comparative Example 4:

[0079] Compared with Example 1, this comparative example only increases the amount of polyethyleneimine in the thickener from "2g" to "21.32g", and the remaining steps and parameters are the same, which will not be repeated in this comparative example, and finally a supramolecular fracturing fluid is obtained.

[0080] Comparative Example 5:

[0081] Compared with Example 1, this comparative example only increases the amount of the reaction product of allyl chloride and long-chain alkyl tertiary amine in the thickener from "2g" to "21.32g", and the remaining steps and parameters are the same, which will not be repeated in this comparative example, and finally a supramolecular fracturing fluid is obtained.

[0082] Performance Test:

[0083] Apparent viscosity test: using a ZNN-D6Ⅱ viscometer, at room temperature and a rotation speed of 100 r / min, the apparent viscosity of the supramolecular fracturing fluids prepared in Examples 1 to 5 and Comparative Examples 1 to 5 was tested, and each sample was tested 3 times to obtain an average value;

[0084] Drag reduction rate test: Fill a clean friction meter batching tank with 50L of clean water, turn on the pipeline test flow control switch, adjust the pipeline flow to stabilize at 28.2L / min, stabilize for ≥3min, and record the clean water pressure difference P0. Close the pipeline test flow control switch, turn on the stirring kettle, add the fracturing fluid thickener, continue stirring for 20min, dissolve the polymer and mix evenly, prepare a low-viscosity system, and turn off the stirring kettle. Enter the clean water pressure difference P0 on the computer operation page, turn on the pipeline test flow control switch, adjust the pipeline flow to stabilize at 28.2L / min, stabilize for ≥3min, start measuring, and record the drag reduction rate of each group of samples in Example 1-Example 5 and Comparative Example 1-Comparative Example 5.

[0085] Sand suspension performance test: prepare fracturing fluids with different mass fractions, pour 200L of the prepared fracturing fluid into a constant speed mixer, adjust the speed of the constant speed mixer to a low speed gear, select quartz sand with a diameter of 0.42-0.84mm (20-40 mesh) as a proppant, mix the proppant and the fracturing fluid at a mass ratio of 30:70, stir and mix evenly, and immediately transfer to a 250L glass column to observe the sand suspension performance of the fracturing fluid. By testing the sedimentation distance and time of a single quartz sand, record the sedimentation rate of each group of samples in Example 1-Example 5 and Comparative Example 1-Comparative Example 5;

[0086] Surface / interfacial tension test of gel-breaking liquid: 100g of each group of fracturing fluid in Example 1-Example 5 and Comparative Example 1-Comparative Example 5 were taken, 0.04g of (NH4)2S2O8 was added, stirred and mixed evenly, and gel-breaking was carried out in a constant temperature water bath at 90°C for 2h, and the apparent viscosity of the gel-breaking liquid was measured. The surface / interfacial tension of the gel-breaking liquid was tested at room temperature using a fully automatic surface / interfacial tension meter using the Du-Nouy ring method, and the same sample was measured 3 times to obtain the average value; the results are shown in Table 1 below:

[0087] Table 1 Summary of experimental results in Examples 1 to 5 and Comparative Examples 1 to 5

[0088] project Apparent viscosity / mPa·s Drag reduction rate / % Sedimentation rate / mm / s Surface tension / mN / m Interfacial tension / mN / m Example 1 146 72 0.0014 24.92 1.07 Example 2 147 70.4 0.0053 25.32 1.12 Example 3 145 71.9 0.0038 25.78 1,16 Example 4 146 72.5 0.0029 24.29 1.08 Example 5 143 71.3 0.0019 25.16 1.15 Comparative Example 1 89 68.6 0.0073 26.88 1.25 Comparative Example 2 82 68.2 0.0075 27.52 1.26 Comparative Example 3 79 67.9 0.0076 28.11 1.28 Comparative Example 4 110 69.8 0.0071 26.45 1.21 Comparative Example 5 128 70.1 0.0069 25.99 1.18

[0089] Data Analysis:

[0090] As can be seen from Table 1, the supramolecular fracturing fluid prepared by the present invention has higher apparent viscosity, higher drag reduction rate, lower sedimentation rate, lower surface tension and lower interfacial tension, which indicates that the supramolecular fracturing fluid prepared by the present invention can still present high viscoelastic fluid properties even when the agent concentration is not high, and has good drag reduction performance and high sand suspension, and can meet the requirements of oil field fracturing construction. This may be because the sodium salicylate in the cross-linking agent provided by the present invention can form micelle gel with the surfactant through hydrophobic association and electrostatic action, and then the thickener is compounded and used. The hydrophobic long chain in the reaction product of a relatively small amount of polyethyleneimine, a relatively large amount of acrylamide segments and a relatively small amount of propylene chloride and a long-chain alkyl tertiary amine in the thickener can be embedded in the micelle gel through the association of hydrophobic groups and form a strongly branched supramolecular network, which can enhance the network structure strength of the fracturing fluid and improve the supramolecular fracturing performance. The rheological properties of the fluid make the supramolecular fracturing fluid have a stronger sand suspension ability. In addition, the solubilizer and co-solvent provided by the present invention minimize the decrease in water solubility caused by the large number of hydrophobic groups contained in the thickener, while ensuring the solution structure capacity, so that the polymer thickener molecular chain contains as many water-soluble structural units as possible, and the sodium ions and long alkyl sulfonate ions ionized by the sodium dodecylbenzene sulfonate surfactant can inhibit the cross-linking reaction to a certain extent through the shielding effect and steric hindrance effect of the metal cation, and the potassium chloride introduced into the compound cross-linking agent can prolong the gelation time, effectively solve the problem of large wellbore friction during ultra-deep fracturing, and effectively reduce shear damage. However, in Comparative Examples 4 and 5, due to the increase in the amount of the reaction product of polyethyleneimine, propylene chloride and long carbon chain alkyl tertiary amine, the system cross-linking degree is too large, which in turn reduces the performance of the supramolecular fracturing fluid.

[0091] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0092] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A supramolecular fracturing fluid, characterized in that: The raw materials include the following parts by weight: 80-90 parts of thickener, 1-3 parts of solubilizer, 3-5 parts of cosolvent, and 50-60 parts of crosslinking agent; The thickener is prepared from the reaction product of polyethyleneimine, acrylamide, allyl chloride and long-chain alkyl tertiary amine; The mass ratio of the reaction product of polyethyleneimine, acrylamide, propylene chloride and long carbon chain alkyl tertiary amine is 2-4:21.32-35.54:2-3; The cross-linking agent is prepared from potassium chloride, sodium salicylate and a surfactant; The mass ratio of potassium chloride, sodium salicylate and surfactant is 25-30:20-24:5-6; The preparation process of the reaction product of allyl chloride and long carbon chain alkyl tertiary amine is as follows: Add allyl chloride and long-chain alkyl tertiary amine to acetone, react at 45-50° C. for 22-24 hours under a nitrogen atmosphere, rotary evaporate, collect the sample, and vacuum dry to obtain a reaction product of allyl chloride and long-chain alkyl tertiary amine; The solubilizer is octadecyl hydroxypropyl sulfobetaine, the cosolvent is beta-cyclodextrin, and the surfactant is sodium dodecylbenzene sulfonate.

2. The supramolecular fracturing fluid according to claim 1, characterized in that: The molar ratio of the allyl chloride to the long-chain alkyl tertiary amine is 0.019-0.026:0.019-0.026, and the dosage ratio of the allyl chloride to acetone is 0.019-0.026 mol:15-18 mL.

3. The supramolecular fracturing fluid according to claim 1, characterized in that: The preparation process of the thickener is as follows: Step S1. Add polyethyleneimine into deionized water and stir magnetically for 60 hours to obtain a mixed solution A; Step S2. adding the reaction product of the crosslinking agent, acrylamide, allyl chloride and long-chain alkyl tertiary amine into deionized water, and ultrasonically treating for 5-8 minutes to obtain a mixed solution B; Step S3. Mix the mixed solution A and the mixed solution B evenly, add the initiator and the co-initiator under nitrogen, and react at 30-35° C. for 10-12 hours to obtain a thickener.

4. The supramolecular fracturing fluid according to claim 3, characterized in that: The dosage ratio of polyethyleneimine and deionized water in step S1 is 2-4 g: 100-110 mL.

5. The supramolecular fracturing fluid according to claim 3, characterized in that: The mass ratio of the reaction product of the crosslinking agent, acrylamide, allyl chloride and long-chain alkyl tertiary amine in step S2 is 0.8-1:21.32-35.54:2-3, and the crosslinking agent in step S2 is N,N-dimethylacrylamide.

6. The supramolecular fracturing fluid according to claim 3, characterized in that: In step S2, the usage ratio of acrylamide to deionized water is 21.32-35.54 g: 100-110 mL, and the molecular weight of polyethyleneimine is 70000-80000 g / mol.

7. The supramolecular fracturing fluid according to claim 3, characterized in that: In step S3, the volumes of the mixed solution A, the mixed solution B, the initiator and the co-initiator are 100-110 mL: 1-3 mL: 30-35 μL, the initiator is potassium persulfate, and the co-initiator is N', N', N, N-tetramethylethylenediamine.

8. A method for preparing the supramolecular fracturing fluid according to any one of claims 1 to 7, characterized in that: The following steps are involved: The thickener, solubilizer, co-solvent and cross-linking agent are mixed in a stirrer and stirred at a rotation speed of 1000-1500 rpm for 18-22 minutes to obtain a supramolecular fracturing fluid.