A CO 2 Responsive high-efficiency drag-reducing and easy-flow fracturing fluid and its preparation method and application

Abstract

The present invention discloses a CO2-responsive high-efficiency drag-reducing and easily flowback fracturing fluid, its preparation method and application, which relate to the technical field of fracturing fluids for oil and gas exploitation. The fracturing fluid is prepared from 0.5 - 2.0 parts of thickening drag reducer, 0.3 - 5.0 parts of clay stabilizer, 0.5 - 2.0 parts of CO2 and 1000 parts of clear water. The clay stabilizer is a low-molecular-weight hyperbranched amine, and its aqueous solution has CO2-responsive characteristics. After the clay stabilizer responds to CO2, it can improve the sand-carrying and drag-reducing effects of the fracturing fluid. After the fracturing fluid enters the formation, as the clay stabilizer and CO2 are adsorbed by the formation, the fracturing fluid automatically breaks gel and flows back, with a high flowback rate and the flowback fracturing fluid can be reused. The fracturing fluid provided by this application has the characteristics of simple preparation, environmental friendliness and low cost, and is an important product for CO2 emission reduction and oil and gas production increase.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas production fracturing fluid, and in particular to a CO 2 The invention discloses a highly efficient drag-reducing and easy-flowback fracturing fluid and a preparation method and application thereof. Background Art

[0002] CO 2 It is one of the main greenhouse gases, causing global warming, affecting the ecological environment, and posing a serious threat to human survival. 2 The concentration increases year by year. By July 2023, the atmospheric CO 2 The concentration has reached 422.14ppm. In order to actively respond to climate and environmental challenges, China has proposed a "dual carbon" goal and multiple paths to control carbon emissions, including several reliable CO 2 Emission reduction measures include: ① using clean energy (such as shale gas), ② reducing CO 2 ③ Use CO as raw material for other production 2 Geological storage.

[0003] Shale gas is recognized as the cleanest fossil energy. my country is rich in shale gas resources, with proven reserves ranking first in the world, and has great mining value. Unlike conventional natural gas, shale gas is stored in shale, which has very small pores and low permeability inside the reservoir, making it more difficult to mine. In order to improve the economic benefits of mining, hydraulic fracturing technology must be used. Shale hydraulic fracturing is to inject fracturing fluid into the formation. The pressure is transmitted through the fracturing fluid, which expands the formation cracks and creates new cracks, and carries proppants into the cracks to prevent the cracks from closing, thereby improving the ability of shale gas to seep into the wellbore. Therefore, the complexity of crack creation and the effect of proppant laying are the key factors that determine the effect of fracturing. In the process of shale gas hydraulic fracturing, slick water is needed as the working fluid, and a large amount of fracturing fluid is retained in the formation after construction, which has the risk of causing water-sensitive damage to shale. Clay stabilizers must be added to the working fluid.

[0004] Clay stabilizers used in hydraulic fracturing of low permeability reservoirs can generally be divided into inorganic salts and quaternary ammonium salts. Inorganic salt clay stabilizers are stabilizers that stabilize the soil by metal ions (such as K + ) exchange Na between clay crystal layers + To achieve the effect of inhibiting clay expansion and dispersion, but usually K + The Na in the formation water +Replace again, can not maintain the effect for a long time.Compared to inorganic salts, quaternary ammonium salt clay stabilizers often have better water washing resistance.For example, patent CN116120547B discloses a quaternary ammonium salt cationic polymer, its main chain contains more positive charge, can be adsorbed with multiple clay particles simultaneously, form multi-point adsorption, suppress the hydration expansion of clay, large freedom of movement, strong control effect is arranged for the dispersion and migration of clay particles, and has very strong water washing resistance.But it is generally believed that the chemical bond of conventional quaternary ammonium salt is unstable, and it is difficult to meet the high temperature formation demand.

[0005] In addition, shale gas recovery is usually lower than that of conventional natural gas reservoirs. 2 Injection into the formation is a feasible technology. For example, the article (Liu Li, Wang Yimin, Li Jiqing, et al.) 2 Research progress on improving shale gas recovery. Contemporary Chemical Research. 2023(12):14-16) proposed that CO injection 2 The technology is seen as a way to improve shale gas recovery and permanently achieve CO 2 Geological storage is an important method. 2 Injection into the formation, CO 2 Molecules and CH 4 There is competitive adsorption of molecules in shale nanopores, and CO 2 The adsorption capacity of CH 4 The molecules have strong adsorption capacity and can occupy the original CH 4 The space occupied by the molecule forces CH 4 The molecules desorb from the adsorbed state to the free state, thereby improving the shale gas recovery rate.

[0006] Therefore, an efficient fracturing fluid was developed to take into account ① efficient sand carrying, ② long-term reservoir protection, and ③ CO 2 Requirements such as emission reduction and geological storage, and ④ improving shale gas recovery rate will be of great significance to my country's energy security, environmental protection and economic transformation. Summary of the invention

[0007] In order to solve the deficiencies in the prior art, the present invention aims to provide a CO 2 The invention discloses a highly efficient drag-reducing and easy-flowback fracturing fluid and a preparation method and application thereof.

[0008] To achieve the above purpose, the technical solution of the present invention is as follows.

[0009] First, the present invention discloses a CO 2 The high-efficiency drag-reducing and easy-flow fracturing fluid contains thickening drag reducer, clay stabilizer, CO 2The fracturing fluid is composed of the following components by weight: 0.5 to 2.0 parts of thickening drag reducer, 0.3 to 5.0 parts of clay stabilizer, 0.5 to 2.0 parts of CO 2 and 1000 parts of water.

[0010] The thickening drag reducing agent is anionic polyacrylamide, which can be quickly dissolved in water and increase the viscosity of the water phase, thereby reducing the resistance during the pumping process of the fracturing fluid.

[0011] The clay stabilizer is a low molecular weight hyperbranched amine that is easily soluble in water and has a CO 2 Response characteristics. Clay stabilizer and CO 2 After the response, the tertiary amine groups on the molecules are protonated and carry a certain positive charge. The positively charged clay stabilizer can interact with the negatively charged thickening drag reducer to form a three-dimensional network molecular structure in the solution, further increasing the viscosity of the fracturing fluid and improving the sand carrying and drag reduction effects. After entering the reservoir, the clay stabilizer is adsorbed on the surface of the clay mineral, which inhibits the hydration expansion, dispersion and migration of the clay mineral. The multi-tertiary amine structure of the hyperbranched amine improves the stability of the clay stabilizer adsorption, is not easily washed away by other fluids, and prolongs the protection period of the reservoir.

[0012] The CO 2 The fracturing fluid has different effects at different stages of use. 2 It can be used as a stimulus response factor for clay stabilizers to promote the formation of a three-dimensional network structure of polymers in the fracturing fluid, thereby improving the sand carrying and drag reduction effects of the fracturing fluid. 2 It can interact with shale formations to promote shale gas desorption, and it can also mix with formation crude oil to increase crude oil fluidity, thereby improving oil and gas recovery.

[0013] Furthermore, the clay stabilizer is a hyperbranched amine with a rigid ring at the center, which has a general structural formula of Formula 1 and Formula 2:

[0014]

[0015]

[0016] In the above formula, R 1 The group has a structural formula of Formula 3 to Formula 6:

[0017]

[0018] The method for preparing the hyperbranched amine with a rigid ring as the center comprises the following steps:

[0019] S1. A certain amount of polyamine is put into a reaction vessel, a solvent is added, and stirred to dissolve to obtain a mixture A; a certain amount of alkoxy acyl polysubstituted benzene is taken, a solvent is added to dissolve, and a mixture B is obtained;

[0020] S2. Under stirring, the mixture A is kept at a constant temperature of 50 to 75° C. for 5 to 20 minutes, and then the mixture B is slowly added dropwise to the reaction vessel; after the addition is complete, the reaction is continued at a constant temperature of 50 to 75° C. for 4 to 12 hours to obtain a mixture C;

[0021] S3. The mixture C is distilled under reduced pressure to remove the solvent to obtain an intermediate raw material D;

[0022] S4. Pure water was added to the intermediate raw material D to obtain a solution, and formic acid was added and stirred to obtain a mixture E;

[0023] S5. The mixture E is heated to 70 to 100 ° C, and the formaldehyde aqueous solution is slowly added dropwise under stirring; after the addition is complete, the reaction is continued at a constant temperature of 70 to 100 ° C for 2 to 12 hours to obtain a mixture F;

[0024] S6. The obtained mixture F is cooled to room temperature, the pH is adjusted to 9-12, ether is added to extract the organic phase, the liquids are separated, and vacuum distillation is performed to obtain a hyperbranched amine with a rigid ring at the center.

[0025] Furthermore, the polyamine in step S1 is one of ethylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine.

[0026] Furthermore, the solvent in step S1 is one of methanol, ethanol, isopropanol, and ethylene glycol, or a combination thereof.

[0027] Furthermore, the feed ratio of polyamine to solvent in the mixture A in step S1 is 1:5-20.

[0028] Furthermore, the feed ratio of alkoxy acyl polysubstituted benzene to solvent in the mixture B in step S1 is 1:5-20.

[0029] Furthermore, the feed ratio of polyamine to alkoxy acyl polysubstituted benzene in step S1 is 0.62-3.6:1.

[0030] Furthermore, the alkoxyacyl polysubstituted benzene in step S1 is one of alkoxyacyl disubstituted benzene and alkoxyacyl trisubstituted benzene; the alkoxyacyl disubstituted benzene has a structural formula of Formula 7:

[0031]

[0032] In formula (7), R 2 The group is one of methyl, ethyl, propyl and isopropyl.

[0033] Furthermore, the alkoxy acyl trisubstituted benzene in step S1 has a structural formula of Formula 8:

[0034]

[0035] In formula (8), R 3 The group is one of methyl, ethyl, propyl and isopropyl.

[0036] Furthermore, the dropping speed of the mixture B in step S2 is 1 s / drop to 20 s / drop.

[0037] Furthermore, the mass ratio of the intermediate raw material D, pure water and formic acid required for preparing the mixture E in step S4 is 1:3-20:0.8-3.5.

[0038] Furthermore, the mass ratio of the formaldehyde aqueous solution required for preparing the mixture F in step S5 to the formic acid in step S4 is 1.8-3.6:1.

[0039] Secondly, the present invention discloses a CO 2 The preparation method of the responsive high-efficiency drag-reducing and easy-flowback fracturing fluid comprises the following steps:

[0040] S7. Add a certain amount of clean water to the liquid storage tank, add a certain amount of thickening drag reducer under stirring, and mix well to obtain a viscous liquid;

[0041] S8. Add a certain amount of clay stabilizer and other fracturing fluid additives into a liquid storage tank, stir and mix evenly to obtain component F;

[0042] S9. When fracturing is required, a certain amount of CO 2 Inject into component F, stir and mix evenly to obtain CO 2 Response to high efficiency drag reduction and easy flowback fracturing fluid.

[0043] Furthermore, the other fracturing fluid additives in step S8 include drainage aids, bactericides, foaming agents, defoaming agents, etc., which are well known to those skilled in the art and can be added according to specific construction requirements. 2 The highly efficient drag-reducing and easy-flowback fracturing fluid can automatically break the gel in the formation, so the other fracturing fluid additives do not include a gel breaker.

[0044] Finally, the present invention discloses the above-mentioned CO 2 The application of high-efficiency drag-reducing and easy-flowback fracturing fluid includes:

[0045] First, the CO 2 The highly efficient drag-reducing and easy-to-flow back fracturing fluid and proppant are mixed and injected into the fractured cracks. After completion, the pump is stopped and the well is shut down to return and discharge the fracturing fluid.

[0046] Furthermore, the returned fracturing fluid can be reused.

[0047] The beneficial effects of the present invention are:

[0048] (1) CO provided in this application 2 Highly efficient drag reduction and easy flowback fracturing fluid can reduce greenhouse gas CO 2 As a usable raw material, CO 2 Reduction and utilization.

[0049] (2) In conventional fracturing fluids, there is no synergistic effect between thickening drag reducers and clay stabilizers; however, the CO 2 Response to high-efficiency drag reduction and easy-flow fracturing fluid, after CO 2 Stimulation, thickening drag reducer and clay stabilizer interact with each other to form a three-dimensional network to increase the thickening effect of thickening drag reducer, further increasing the drag reduction and sand carrying performance of fracturing fluid. 2 Stimulation, the thickening drag reducing agent provided in the present application has a better thickening effect and can reduce the amount of the thickening drag reducing agent used.

[0050] (3) CO provided in this application 2 After the high-efficiency drag-reducing and easy-flow fracturing fluid enters the formation, the clay stabilizer and CO 2 It can react with clay minerals in the formation and desorb them from the fracturing fluid system; the three-dimensional network structure of the fracturing fluid is destroyed (i.e., degelling), and the viscosity is reduced, which is conducive to the return of the fracturing fluid; the degelling process occurs spontaneously in the formation, and there is no need to add degelling agents, which can reduce the cost of degelling agents and avoid formation damage caused by incomplete degelling due to uneven degelling agents.

[0051] (4) CO provided in this application 2 After the high-efficiency drag-reducing and easy-flow fracturing fluid enters the formation, the clay stabilizer and CO 2 After being absorbed by the formation, the thickened drag reducer in the fracturing fluid returns to the ground along with the flowback fluid; after being processed on the ground to remove impurities such as solid particles, the thickened drag reducer can be used again in fracturing construction, which is reusable and environmentally friendly.

[0052] (5) CO provided in this application 2 After the highly efficient drag-reducing and easy-flow fracturing fluid enters the shale gas formation, the CO 2 Can be used with shale gas (mainly CH 4 ) competitive adsorption, promoting faster desorption of shale gas in the shale matrix and improving shale gas recovery rate.

[0053] (6) CO provided in this application 2After the high-efficiency drag-reducing and easy-flow fracturing fluid enters the reservoir, the CO 2 It can be mixed with formation crude oil, increasing the volume and fluidity of crude oil and improving crude oil recovery rate.

[0054] In summary, the CO provided by the present invention 2 The responsive, high-efficiency, drag-reducing and easy-flow fracturing fluid has the characteristics of simple preparation, green environmental protection and low cost. It is an important product for improving the recovery rate of shale gas and crude oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 Schematic diagram of the structure of a hyperbranched amine with a rigid ring at its center according to the present invention;

[0056] Figure 2 The synthetic route of the hyperbranched amine described in Example 1;

[0057] Figure 3 This is the synthetic route of the hyperbranched amine described in Example 3. DETAILED DESCRIPTION

[0058] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0059] Example 1: Preparation of a hyperbranched amine with a rigid ring at the center

[0060] The hyperbranched amine described in the present application has a rigid ring center. Figure 1 The general structure shown in FIG. 1 shows that when the benzene ring is disubstituted at the para position and R 1 The group is R 1 When -1, the structure of the hyperbranched amine is shown in Formula 9:

[0061]

[0062] A synthetic route for the hyperbranched amine of the rigid ring shown in formula 9 is as follows Figure 2 shown.

[0063] The hyperbranched amine with a rigid ring as the center of this embodiment is prepared by the following method:

[0064] (1) Weigh 12.0 g of ethylenediamine into a 250 mL three-necked flask, add 60 g of methanol and stir to dissolve, to obtain a mixture A; take 19.4 g of dimethyl terephthalate, add 97 g of methanol and dissolve, to obtain a mixture B;

[0065] (2) Under stirring, the mixture A was kept at a constant temperature of 50° C. for 5 minutes, and then the mixture B was slowly added dropwise to the three-necked flask at a dropping speed of 1 s / drop. After the dropping was complete, the mixture was kept at a constant temperature of 50° C. for 12 hours to obtain a mixture C;

[0066] (3) distilling the mixture C under reduced pressure to remove the solvent, thereby obtaining an intermediate raw material D;

[0067] (4) Add 75 g of pure water to the intermediate raw material D to dissolve it to obtain a solution, add 19.2 g of formic acid, and stir evenly to obtain a mixture E;

[0068] (5) The mixture E was heated to 70° C., and 34.6 g of 35% formaldehyde aqueous solution was slowly added dropwise under stirring; after the addition was complete, the reaction was continued at 70° C. for 12 h to obtain a mixture F;

[0069] (6) The obtained mixture F was cooled to room temperature, and the pH value was adjusted to 9 with 1% NaOH solution. 300 mL of ether was added to extract the organic phase. The mixture was separated and distilled under reduced pressure to obtain a hyperbranched amine with a rigid ring at the center.

[0070] Example 2: Preparation of a hyperbranched amine with a rigid ring at the center

[0071] The hyperbranched amine described in the present application has a rigid ring center. Figure 1 The general structure shown in FIG. 1 is that when the benzene ring is disubstituted at the meta position and R 1 The group is R 1 When -2, the structure of the hyperbranched amine is shown in Formula 10:

[0072]

[0073] The hyperbranched amine of the rigid ring shown in formula 10 is prepared by the following method:

[0074] (1) Weigh 21.6 g of diethylenetriamine into a 1000 mL three-necked flask, add 330 g of isopropanol, stir and dissolve to obtain a mixture A; take 22.2 g of diethyl isophthalate, add 320 g of isopropanol and dissolve to obtain a mixture B;

[0075] (2) Under stirring, the mixture A was kept at a constant temperature of 70° C. for 15 min, and then the mixture B was slowly added dropwise to the three-necked flask at a dropping speed of 15 s / drop. After the dropping was complete, the mixture was kept at a constant temperature of 70° C. for 8 h to obtain a mixture C;

[0076] (3) distilling the mixture C under reduced pressure to remove the solvent, thereby obtaining an intermediate raw material D;

[0077] (4) Add 300 g of pure water to the intermediate raw material D to dissolve the solution, add 53.8 g of formic acid, stir evenly, and obtain a mixture E;

[0078] (5) The mixture E was heated to 80° C., and 129 g of 35% formaldehyde aqueous solution was slowly added dropwise under stirring; after the addition was complete, the reaction was continued at 80° C. for 8 h to obtain a mixture F;

[0079] (6) The obtained mixture F was cooled to room temperature, and the pH value was adjusted to 10 with 1% NaOH solution. 350 mL of ether was added to extract the organic phase. The mixture was separated and distilled under reduced pressure to obtain a hyperbranched amine with a rigid ring at the center.

[0080] Example 3: Preparation of a hyperbranched amine with a rigid ring at the center

[0081] The hyperbranched amine described in the present application has a rigid ring center. Figure 1 The general structure shown in the figure, when the benzene ring is trisubstituted and R 1 The group is R 1 When -3, the structure of the hyperbranched amine is shown in Formula 11:

[0082]

[0083] A synthetic route for the rigid ring hyperbranched amine shown in formula 11 is as follows Figure 3 The hyperbranched amine with a rigid ring as the center of this embodiment is prepared by the following method:

[0084] (1) Weigh 46.8 g of triethylenetetramine into a 2000 mL three-necked flask, add 470 g of ethanol and stir to dissolve, to obtain a mixture A; take 33.6 g of tripropyl trimesic acid, add 340 g of isopropanol and dissolve, to obtain a mixture B;

[0085] (2) Under stirring, the mixture A was kept at a constant temperature of 75° C. for 10 min, and then the mixture B was slowly added dropwise to the three-necked flask at a dropping speed of 10 s / drop. After the dropping was complete, the mixture was kept at a constant temperature of 75° C. for 4 h to obtain a mixture C;

[0086] (3) distilling the mixture C under reduced pressure to remove the solvent, thereby obtaining an intermediate raw material D;

[0087] (4) Add 900 g of pure water to the intermediate raw material D to dissolve the solution, add 152.2 g of formic acid, stir evenly, and obtain a mixture E;

[0088] (5) Mixture E was heated to 90° C., and 456.6 g of 35% formaldehyde aqueous solution was slowly added dropwise under stirring; after the addition was complete, the reaction was continued at 90° C. for 4 h to obtain mixture F;

[0089] (6) The obtained mixture F was cooled to room temperature, the pH was adjusted to 11 with 1% NaOH solution, 300 mL of ether was added to extract the organic phase, the liquids were separated, and the mixture was distilled under reduced pressure to obtain a hyperbranched amine with a rigid ring at the center.

[0090] Example 4: Preparation of a hyperbranched amine with a rigid ring at the center

[0091] The hyperbranched amine described in the present application has a rigid ring center. Figure 1 The general structural formula shown in the figure is that when the benzene ring is partially trisubstituted and R 1 The group is R 1 When -4, the structure of the hyperbranched amine is shown in Formula 12:

[0092]

[0093] The hyperbranched amine of the rigid ring shown in formula 12 is prepared by the following method:

[0094] (1) Weigh 62.5 g of tetraethylene pentamine into a 3000 mL three-necked flask, add 940 g of ethylene glycol and stir to dissolve, to obtain a mixture A; take 33.6 g of triisopropyl trimesic acid, add 500 g of ethylene glycol and dissolve, to obtain a mixture B;

[0095] (2) Under stirring, the mixture A was kept at a constant temperature of 60° C. for 20 min, and then the mixture B was slowly added dropwise to the three-necked flask at a dropping speed of 20 s / drop. After the dropping was complete, the mixture was kept at a constant temperature of 60° C. for 10 h to obtain a mixture C;

[0096] (3) distilling the mixture C under reduced pressure to remove the solvent, thereby obtaining an intermediate raw material D;

[0097] (4) 1450 g of pure water was added to the intermediate raw material D to dissolve to obtain a solution, and 253.4 g of formic acid was added and stirred to obtain a mixture E;

[0098] (5) The mixture E was heated to 100° C., and 912.2 g of a 35% formaldehyde aqueous solution was slowly added dropwise under stirring; after the addition was complete, the mixture was kept at 100° C. for 2 h to obtain a mixture F;

[0099] (6) The obtained mixture F was cooled to room temperature, and the pH value was adjusted to 10 with 1% NaOH solution. 360 mL of ether was added to extract the organic phase. The mixture was separated and distilled under reduced pressure to obtain a hyperbranched amine with a rigid ring at the center.

[0100] Example 5: Structural characterization of a hyperbranched amine with a rigid ring at the center

[0101] The hyperbranched amine with a rigid ring center prepared in Example 3 was selected as a clay stabilizer. 2O was used as solvent, and the dried carboxylic acid betaine zwitterions were analyzed using a Bruker Avance III HD NMR spectrometer. 1 H NMR characterization. The results are as follows: 1 H NMR (400MHz) δ: 7.76 (s, 3H), 4.01-4.16 (m, 12H), 2.51-2.82 (m, 24H), 2.36 (m, 9H), 2.27 (m, 36H). The NMR results confirmed that the prepared product was consistent with the designed structure.

[0102] Example 6: CO 2 Evaluation on response characteristics of high-efficiency drag-reducing and easy-flowback fracturing fluid

[0103] Using viscosity and sand carrying capacity as indicators, CO 2 Response characteristics of high-efficiency drag-reducing and easy-flowback fracturing fluid.

[0104] The hyperbranched amine with a rigid ring at the center prepared in Examples 1 to 4 was selected as a clay stabilizer, anionic polyacrylamide used for preparing slick water on site in oil fields was selected as a thickening drag reducing agent, and dry ice was selected as a CO 2 Source, prepare fracturing fluid. The specific steps are as follows:

[0105] (1) Measure 200 mL of pure water and add it to a 500 mL beaker. Add a certain amount of thickening drag reducer powder while stirring. Continue stirring for 5 minutes to ensure that the thickening drag reducer is evenly dissolved to obtain solution A.

[0106] (2) Weigh a certain amount of the hyperbranched amine with a rigid ring center prepared in Examples 1 to 4, add it to Solution A under stirring, and continue stirring for 5 minutes to ensure that the hyperbranched amine is evenly dissolved to obtain Solution B;

[0107] (3) Transfer all of Solution B to a 250 mL thick-walled pressure-resistant bottle, add a certain amount of dry ice, seal the thick-walled pressure-resistant bottle, and vigorously stir the solution to allow CO to 2 Fully dissolved in the solution to obtain solution C;

[0108] (4) A high temperature rheometer (HAAKE MARS III, Thermo Fisher Scientific (China) Co., Ltd.) was used to measure the flow rate at 25°C and 170 s. -1 The apparent viscosity η of solution C under 1 ;

[0109] (5) Take 100 mL of solution C, add 20 g of shale powder (500-800 mesh), stir for 10 min and let stand for 30 min, take the supernatant D, and measure the apparent viscosity η of solution D using a high temperature rheometer. 2 ;

[0110] (6) Recover the fracturing fluid after step (5), add an equal amount of the same hyperbranched amine as in step (2), stir and mix evenly, and then transfer to a 250 mL thick-walled pressure bottle; add a certain amount of dry ice, seal the thick-walled pressure bottle, and vigorously stir the solution to allow CO 2 The solution was fully dissolved into the solution to obtain solution E; the apparent viscosity η of solution E was measured by a high temperature rheometer. 3 .

[0111] The test results of fracturing fluid performance of different groups are shown in Table 1.

[0112] Table 1 Apparent viscosity of different fracturing fluids

[0113]

[0114] As can be seen from Table 1, compared with the conventional clay stabilizer prepared fracturing fluid (Group 1), the CO 2 The high-efficiency drag-reducing and easy-flow fracturing fluid (Group 3) has a significantly higher apparent viscosity η 1 After shale adsorption, the apparent viscosity of group 3 fracturing fluid returned to a similar value as group 1, which indicates that CO 2 The clay stabilizer has been adsorbed by the shale. Groups 2 to 5, after adsorption by shale, the apparent viscosity of the fracturing fluid η 2 The results show that the corresponding fracturing fluid has obvious gel breaking, which meets the requirements of shale gas fracturing construction. 2 After that, the apparent viscosity η of the corresponding fracturing fluid 3 Obviously restored to the initial state (η 1 ), which shows that the fracturing fluid has a good recycling effect.

[0115] Example 7: CO 2 Evaluation of sand-carrying performance of high-efficiency drag-reducing and easy-flow fracturing fluid

[0116] The hyperbranched amine with a rigid ring at the center prepared in Examples 1 to 4 was selected as a clay stabilizer, anionic polyacrylamide used for preparing slick water on site in oil fields was selected as a thickening drag reducer, quartz sand with a diameter of 0.42 to 0.84 mm (20 to 40 mesh) was selected as a proppant, and dry ice was selected as a CO 2 Source, prepare fracturing fluid. The specific steps are as follows:

[0117] (1) Measure 200 mL of pure water and add it to a 500 mL beaker. Add a certain amount of thickening drag reducer powder while stirring. Continue stirring for 5 minutes to ensure that the thickening drag reducer is evenly dissolved to obtain solution A.

[0118] (2) Weigh a certain amount of the hyperbranched amine with a rigid ring center prepared in Examples 1 to 4, add it to Solution A under stirring, and continue stirring for 5 minutes to ensure that the hyperbranched amine is evenly dissolved to obtain Solution B;

[0119] (3) Transfer all of Solution B to a 250 mL thick-walled pressure-resistant bottle, add a certain amount of dry ice, seal the thick-walled pressure-resistant bottle, and vigorously stir the solution to allow CO to 2 Fully dissolved in the solution to obtain solution C;

[0120] (4) Pour 200 mL of the prepared fracturing fluid into a constant speed mixer, adjust the speed of the constant speed mixer to a low gear, mix the proppant and the fracturing fluid at a mass ratio of 30:100, stir and mix evenly, and immediately transfer to a 250 mL glass column. By testing the sedimentation distance and time of a single quartz sand, calculate the sedimentation rate of the proppant, and examine the static sand suspension performance of the fracturing fluid.

[0121] The negotiation performance of different groups of fracturing fluids is shown in Table 2.

[0122] Table 2 Settling velocity of proppant in different fracturing fluids

[0123]

[0124] It can be seen from Table 2 that the proppant provided in this patent is CO 2 The sedimentation rate in the high-efficiency drag-reducing and easy-flow fracturing fluid is significantly lower than that in the conventional fracturing fluid, which indicates that the CO 2 The highly efficient drag-reducing and easy-flow fracturing fluid has better sand-carrying performance.

[0125] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A CO 2 Respond to the high-efficiency drag-reducing and easy-flow fracturing fluid. It is characterized in that It is prepared from a thickening drag reducer, a clay stabilizer, CO 2 and water in four components; the feeding ratio of the four components is 0.5-2.0: 0.3-5.0: 0.5-2.0: 1000; the thickening drag reducer is an anionic polyacrylamide; the clay stabilizer is a hyperbranched amine with a rigid ring at the center, and it has one of the structural general formulas in Formula 1 and Formula 2: In formula 1 and formula 2, R 1 The group has a structural formula of Formula 3 to Formula 6:

2. The CO according to claim 1 2 Respond to the high-efficiency drag-reducing and easy-flow fracturing fluid. It is characterized in that The hyperbranched amine can be prepared according to the following method: S1. A certain amount of polyamine is put into a reaction vessel, a solvent is added, and stirred to dissolve to obtain a mixture A; a certain amount of alkoxy acyl polysubstituted benzene is taken, a solvent is added to dissolve, and a mixture B is obtained; S2. Under stirring, the mixture A is kept at a constant temperature of 50 to 75° C. for 5 to 20 minutes, and then the mixture B is slowly added dropwise to the reaction vessel; after the addition is complete, the reaction is continued at a constant temperature of 50 to 75° C. for 4 to 12 hours to obtain a mixture C; S3. The mixture C is distilled under reduced pressure to remove the solvent to obtain an intermediate raw material D; S4. Pure water was added to the intermediate raw material D to obtain a solution, and formic acid was added and stirred to obtain a mixture E; S5. The mixture E is heated to 70 to 100 ° C, and the formaldehyde aqueous solution is slowly added dropwise under stirring; after the addition is complete, the reaction is continued at a constant temperature of 70 to 100 ° C for 2 to 12 hours to obtain a mixture F; S6. The obtained mixture F is cooled to room temperature, the pH is adjusted to 9-12, ether is added to extract the organic phase, the liquids are separated, and vacuum distillation is performed to obtain a hyperbranched amine with a rigid ring at the center.

3. CO according to claim 2 2 Respond to the high-efficiency drag-reducing and easy-flow fracturing fluid. It is characterized in that The raw material polyamine of the hyperbranched amine is one of ethylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine.

4. The CO according to claim 2 2 Respond to the high-efficiency drag-reducing and easy-flow fracturing fluid. It is characterized in that In step S1, the solvent of the polyamine and the alkoxy acyl polysubstituted benzene is one of methanol, ethanol, isopropanol and ethylene glycol or a combination thereof.

5. The CO according to claim 2 2 Respond to the high-efficiency drag-reducing and easy-flow fracturing fluid. It is characterized in that In step S1, the feed ratio of polyamine to solvent in mixture A is 1:5-20; the feed ratio of alkoxy acyl polysubstituted benzene to solvent in mixture B is 1:5-20; and the feed ratio of polyamine to alkoxy acyl polysubstituted benzene is 0.62-3.6:

1.

6. The CO according to claim 2 2 Respond to the high-efficiency drag-reducing and easy-flow fracturing fluid. It is characterized in that The raw material alkoxyacyl polysubstituted benzene of the hyperbranched amine in step S1 is one of alkoxyacyl disubstituted benzene as shown in formula 7 and alkoxyacyl trisubstituted benzene as shown in formula 8; The alkoxy acyl disubstituted benzene has a structural formula of Formula 7: In formula (7), R 2 The group is one of methyl, ethyl, propyl, and isopropyl; The alkoxy acyl trisubstituted benzene has the structural formula 8: In formula (8), R 3 The group is one of methyl, ethyl, propyl and isopropyl.

7. The CO according to claim 2 2 Respond to the high-efficiency drag-reducing and easy-flow fracturing fluid. It is characterized in that The mass ratio of the intermediate raw material D, pure water and formic acid required for preparing the mixture E in step S4 is 1:3-20:0.8-3.5; the mass ratio of the formaldehyde aqueous solution required for preparing the mixture F in step S5 to the formic acid in step S4 is 1.8-3.6:

1.

8. CO according to claims 1-7 2 The preparation method of high-efficiency drag-reducing and easy-flow fracturing fluid is provided. Features The following steps are involved: S7. Add a certain amount of clean water to the liquid storage tank, add a certain amount of thickening drag reducer under stirring, and mix well to obtain a viscous liquid; S8. Add a certain amount of clay stabilizer and other fracturing fluid additives into a liquid storage tank, stir and mix evenly to obtain component F; S9. When fracturing is required, a certain amount of CO 2 Inject into component F, stir and mix evenly to obtain CO 2 Response to high efficiency drag reduction and easy flowback fracturing fluid.

9. The CO according to claim 8 2 The preparation method of high-efficiency drag-reducing and easy-flow fracturing fluid is provided. It is characterized in that The other fracturing fluid additives in step S8 include one or a combination of a drainage aid, a bactericide, a foaming agent, and a defoaming agent.

10. The CO according to any one of claims 1 to 7 2 Response to high-efficiency drag-reducing and easy-flow fracturing fluid or the CO according to any one of claims 8-9 2 Application of the fracturing fluid prepared by the preparation method of the high-efficiency drag-reducing and easy-flowback fracturing fluid, It is characterized in that The CO 2 The highly efficient drag-reducing and easy-to-flow back fracturing fluid is mixed with proppant and injected into the fractured cracks. After completion, the pump is stopped and the well is shut down to return the fracturing fluid; the returned fracturing fluid can be reused.

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