Depressurization and augmented injection agent for water injection well and preparation method of decompression and augmented injection agent

Abstract

The invention discloses a water injection well depressurization and augmented injection agent and a preparation method thereof, and relates to the technical field of augmented injection agent materials. The pressure-reducing and injection-increasing agent for the water injection well comprises the following raw materials in parts by weight: 50-60 parts of a betaine type ampholytic surfactant, 10-15 parts of a nonionic surfactant, 20-30 parts of a quaternary ammonium salt surfactant, 3-5 parts of a scale inhibitor, 2-3 parts of a stabilizer and 150 parts of deionized water. The preparation method comprises the following steps: preparing a first-generation polymer from urotropine and tromethamine, then reacting the first-generation polymer with epoxy chloropropane to prepare a graft polymer, and finally reacting the graft polymer with hexadecyl dimethyl tertiary amine to prepare the quaternary ammonium salt surfactant. The water injection well depressurization and augmented injection agent prepared by the invention has the characteristics of large unblocking radius, good depressurization and augmented injection effects and the like.

Description

Technical Field

[0001] The invention relates to the technical field of injection agent materials, and in particular to a water injection well pressure reduction and injection agent and a preparation method thereof. Background Art

[0002] Water injection development is the main exploitation method for low permeability oil fields. However, due to the insufficient natural formation energy and rapid formation pressure decay of low permeability oil reservoirs, low permeability oil wells all have problems such as high water injection pressure, small water injection volume, and imbalance between injection and production. How to achieve pressure reduction and injection increase in low permeability oil reservoirs under the existing pressure system is a common problem that needs to be solved. For water well injection, acidification and fracturing are currently the main measures, and sometimes auxiliary means such as shock waves and hydraulic oscillation are also used. In most oil and gas field fracturing and acidizing fluid systems, surfactants are an important component. With the advancement of technology, the development of new functional surfactants and the research and development of application technologies in oilfield chemistry can enable the technical achievements of oilfield chemical applications to continue to make breakthroughs, thereby further improving the application effect and economic benefits.

[0003] The Chinese invention patent with publication number CN109913193A discloses a pressure reducing and injection enhancing agent for low permeability oil reservoir water injection wells and a preparation method thereof, wherein the pressure reducing and injection enhancing agent comprises the following components and their weight parts: 50-55 parts of dehydrogenated rosin type surfactant, 7-11 parts of betaine type amphoteric surfactant, 18-22 parts of cationic surfactant, 5-8 parts of cetyl alcohol, and 100 parts of ethanol. The pressure reducing and injection enhancing agent has good surface tension, solubilizing ability, wettability changing ability and anti-swelling effect, but its pressure reducing rate is low. Summary of the invention

[0004] In view of the deficiencies in the prior art, the object of the present invention is to provide a water injection well pressure reducing and injection enhancing agent and a preparation method thereof.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions:

[0006] A water injection well pressure reduction and injection enhancement agent, comprising the following raw materials in parts by weight:

[0007] Betaine type amphoteric surfactant: 50-60 parts,

[0008] Nonionic surfactant: 10-15 parts,

[0009] Quaternary ammonium salt surfactant: 20-30 parts,

[0010] Antiscalant: 3-5 parts,

[0011] Stabilizer: 2-3 parts,

[0012] Deionized water: 150 parts;

[0013] The quaternary ammonium salt surfactant is prepared by the following method:

[0014] S1: Deionized water, hexamethylenetetramine, tromethamine, and glacial acetic acid are added to the reactor in sequence, stirred and dissolved, heated to 65-70°C, reacted for 1-2h, cooled to room temperature and separated, the water layer was removed, and washed with deionized water for 3 times to obtain a first-generation polymer. The reaction equation is as follows:

[0015]

[0016] S2: DMSO, first-generation polymer, and potassium hydroxide are added to the reactor in sequence, stirred and dissolved, heated to 40-60°C, and then epichlorohydrin is added dropwise. The reaction is carried out under nitrogen protection for 8-10 hours, cooled to room temperature, and the polymer filter cake is obtained after centrifugal filtration. The polymer is washed three times with dichloromethane and distilled under reduced pressure at 50-60°C to obtain the grafted polymer. The reaction equation is shown as follows:

[0017]

[0018] S3: Add graft polymer, anhydrous ethanol, hydrochloric acid, and hexadecyl dimethyl tertiary amine to a stirred reactor and reflux for 40-48 hours. After the reaction is completed, perform rotary evaporation at 40-50°C, then recrystallize three times with acetone, and dry under vacuum at 60-70°C to obtain a quaternary ammonium surfactant. The reaction equation is as follows:

[0019]

[0020] Among them, m=o+p+q+r, and m, o, p, q, and r are natural numbers.

[0021] The mass ratio of the deionized water, hexamethylenetetramine, tromethamine and glacial acetic acid is 10:2.5:(1.0-1.2):(0.8-1.0).

[0022] The mass ratio of DMSO, first-generation polymer, epichlorohydrin and potassium hydroxide is 100:(6-8):(18-20):(1-1.5).

[0023] The feed ratio of anhydrous ethanol, hydrochloric acid, graft polymer and hexadecyl dimethyl tertiary amine is 100:100:(2-4):(8-20).

[0024] The betaine-type surfactant is one of erucic acid amidopropyl betaine, dodecyl sulfopropyl betaine, and tetradecanoyl amidopropyl hydroxypropyl sulfobetaine.

[0025] The nonionic surfactant is one of lauric acid diethanolamide, lauric acid monoethanolamide and fatty alcohol polyoxyethylene ether.

[0026] The scale inhibitor is one or more combinations of ethylenediaminetetramethylenephosphonic acid, tetrasodium aminotrimethylenephosphonic acid, and tetrasodium hydroxyethylidene diphosphonic acid.

[0027] The stabilizer is one or more combinations of potassium carbonate, potassium chloride and potassium humate.

[0028] A method for preparing a water injection well pressure reducing and injection enhancing agent comprises the following steps:

[0029] S1: weigh by weight: betaine type amphoteric surfactant: 50-60 parts, nonionic surfactant: 10-15 parts, quaternary ammonium salt surfactant: 20-30 parts, scale inhibitor: 3-5 parts, stabilizer: 2-3 parts, deionized water: 150 parts;

[0030] S2: Add deionized water, betaine-type surfactant, nonionic surfactant, quaternary ammonium salt-type surfactant, scale inhibitor and stabilizer to the reactor in sequence, stir, slowly heat up to 40-45°C, and keep warm for 1-2 hours to obtain the water injection well pressure reduction and injection enhancement agent.

[0031] Due to the adoption of the above technical solution, the beneficial effects of the present invention include:

[0032] (1) The present invention prepares a first-generation polymer by using urotropine and tromethamine, then reacts the first-generation polymer with epichlorohydrin to prepare a graft polymer, and then reacts the graft polymer with hexadecyl dimethyl tertiary amine to prepare a quaternary ammonium salt surfactant.

[0033] (2) The quaternary ammonium salt surfactant prepared by the present invention contains a large number of hydrophilic groups in the molecular structure, can form more hydrogen bonds in water, and has excellent water solubility; at the same time, strong interactions are easily generated between the hydrophobic alkyl chains, thereby enhancing the hydrophobic association, and the ability to adsorb at the gas-liquid interface and form micelles in aqueous solution is stronger. The prepared quaternary ammonium salt surfactant has better water solubility and higher surface activity than traditional monomer surfactants, effectively reduces the interfacial tension of the solution, and then reduces the flow resistance of the injected water, achieving the effect of reducing the water injection pressure, and improving the recovery rate of the corresponding oil well. DETAILED DESCRIPTION

[0034] The invention will be further described below in conjunction with the embodiments, but the invention is not limited to these embodiments.

[0035] Example 1 Preparation of quaternary ammonium salt surfactant:

[0036] S1: 100 g of deionized water, 25 g of urotropine, 10 g of tromethamine, and 8 g of glacial acetic acid were added to the reactor in sequence, stirred and dissolved, heated to 65°C, reacted for 2 h, cooled to room temperature to separate layers, removed the water layer, and washed with deionized water for 3 times (50 g of deionized water each time) to obtain a first-generation polymer;

[0037] S2: 100g DMSO, 6g first-generation polymer, and 1g potassium hydroxide were added to the reactor in sequence, stirred and dissolved, heated to 40°C, and then 18g epichlorohydrin was added dropwise. The mixture was reacted for 10h under nitrogen protection, cooled to room temperature, and centrifuged to obtain a polymer filter cake, which was washed with dichloromethane for 3 times (50g dichloromethane was used each time), and distilled under reduced pressure at 50°C for 1h to obtain a grafted polymer;

[0038] S3: Add 2g of grafted polymer, 100ml of anhydrous ethanol, 100ml of hydrochloric acid (36%wt), and 8g of hexadecyldimethylamine into a stirred reactor and reflux for 40h. After the reaction is completed, rotary evaporation is performed at 40°C, and then recrystallization is performed three times with acetone (using 20ml of acetone each time), and vacuum drying is performed at 60°C for 8h to obtain a quaternary ammonium surfactant with a number average molecular weight of 11200.

[0039] Embodiment 2 Preparation of quaternary ammonium salt surfactant:

[0040] S1: 100 g of deionized water, 25 g of urotropine, 11 g of tromethamine, and 9 g of glacial acetic acid were added to the reactor in sequence, stirred and dissolved, heated to 70°C, reacted for 1.5 h, cooled to room temperature to separate the layers, removed the water layer, and washed with deionized water for 3 times (50 g of deionized water each time) to obtain a first-generation polymer;

[0041] S2: 100g DMSO, 7g first-generation polymer, and 1.25g potassium hydroxide were added to the reactor in sequence, stirred and dissolved, heated to 50°C, and then 19g epichlorohydrin was added dropwise. The mixture was reacted for 9h under nitrogen protection, cooled to room temperature, and centrifuged to obtain a polymer filter cake, which was washed with dichloromethane for 3 times (50g dichloromethane was used each time), and distilled under reduced pressure at 55°C for 1h to obtain a grafted polymer;

[0042] S3: Add 3g of grafted polymer, 100ml of anhydrous ethanol, 100ml of hydrochloric acid (36%wt), and 14g of hexadecyldimethylamine into a stirred reactor and reflux for 44h. After the reaction is completed, rotary evaporation is performed at 45°C, and then recrystallization is performed three times with acetone (using 20ml of acetone each time), and vacuum drying is performed at 65°C for 8h to obtain a quaternary ammonium surfactant with a number average molecular weight of 15800.

[0043] Example 3 Preparation of quaternary ammonium salt surfactant:

[0044] S1: 100 g of deionized water, 25 g of urotropine, 12 g of tromethamine, and 10 g of glacial acetic acid were added to the reactor in sequence, stirred and dissolved, heated to 65°C, reacted for 2 h, cooled to room temperature to separate layers, removed the water layer, and washed with deionized water for 3 times (50 g of deionized water each time) to obtain a first-generation polymer;

[0045] S2: 100g DMSO, 8g first-generation polymer, and 1.5g potassium hydroxide were added to the reactor in sequence, stirred and dissolved, heated to 60°C, and then 20g epichlorohydrin was added dropwise. The mixture was reacted for 8h under nitrogen protection, cooled to room temperature, and centrifuged to obtain a polymer cake, which was washed with dichloromethane for 3 times (50g dichloromethane was used each time), and distilled under reduced pressure at 60°C for 1h to obtain a grafted polymer;

[0046] S3: 4 g of grafted polymer, 100 ml of anhydrous ethanol, 100 ml of hydrochloric acid (36% wt), and 20 g of hexadecyldimethylamine were added to a stirred reactor and refluxed for 48 h. After the reaction was completed, rotary evaporation was performed at 50° C., and then recrystallization was performed three times with acetone (using 20 ml of acetone each time), and vacuum drying was performed at 70° C. for 7 h to obtain a quaternary ammonium surfactant with a number average molecular weight of 20,500.

[0047] Example 4 Preparation of water injection well pressure reducing and injection enhancing agent:

[0048] (1) Weigh by weight: betaine type amphoteric surfactant (erucic acid amide propyl betaine): 50 g, nonionic surfactant (lauric acid diethanolamide): 10 g, quaternary ammonium salt type surfactant (prepared in Example 1): 20 g, scale inhibitor (ethylenediaminetetramethylenephosphonic acid): 3 g, stabilizer (potassium carbonate): 2 g, deionized water: 150 g;

[0049] (2) Deionized water, betaine-type surfactant, nonionic surfactant, quaternary ammonium salt-type surfactant, scale inhibitor and stabilizer are added to the reactor in sequence, stirred, and slowly heated to 40°C, and kept warm for 2 hours to obtain a water injection well pressure reduction and injection enhancement agent.

[0050] Example 5 Preparation of water injection well pressure reducing and injection enhancing agent:

[0051] (1) Weigh by weight: betaine type amphoteric surfactant (dodecyl sulfopropyl betaine): 55 g, nonionic surfactant (lauric acid monoethanolamide): 12 g, quaternary ammonium salt surfactant (prepared in Example 2): 25 g, scale inhibitor (tetrasodium aminotrimethylenephosphonate): 4 g, stabilizer (potassium chloride): 2.5 g, deionized water: 150 parts;

[0052] (2) Deionized water, betaine-type surfactant, nonionic surfactant, quaternary ammonium salt-type surfactant, scale inhibitor and stabilizer are added to the reactor in sequence, stirred, and slowly heated to 45°C, and kept warm for 1.5 hours to obtain a water injection well pressure reduction and injection enhancement agent.

[0053] Example 6 Preparation of water injection well pressure reducing and injection enhancing agent:

[0054] (1) Weigh by weight: betaine type amphoteric surfactant (myristyl amide propyl hydroxypropyl sulfobetaine): 60 g, nonionic surfactant (fatty alcohol polyoxyethylene ether): 15 g, quaternary ammonium salt surfactant (prepared in Example 3): 30 g, scale inhibitor (tetrasodium hydroxyethylidene diphosphonate): 5 g, stabilizer (potassium humate): 3 g, deionized water: 150 parts;

[0055] (2) Deionized water, betaine-type surfactant, nonionic surfactant, quaternary ammonium salt-type surfactant, scale inhibitor and stabilizer are added to the reactor in sequence, stirred, and slowly heated to 50°C, and kept warm for 1 hour to obtain a water injection well pressure reduction and injection enhancement agent.

[0056] Comparative Example 1

[0057] The preparation method of a water injection well pressure reducing and injection enhancing agent is basically the same as that of Example 5, except that no quaternary ammonium salt surfactant is added in step (2).

[0058] Comparative Example 2

[0059] A method for preparing a water injection well pressure-reducing and injection-increasing agent is substantially the same as that in Example 5, except that the quaternary ammonium salt surfactant added in step (2) is prepared by the following method:

[0060] S1: 100 g of deionized water, 10 g of urotropine, 6 g of tromethamine, and 5 g of glacial acetic acid were added to the reactor in sequence, stirred and dissolved, heated to 50°C, reacted for 0.5 h, cooled to room temperature to separate the layers, removed the water layer, and washed with deionized water for 3 times (50 g of deionized water was used each time) to obtain a first-generation polymer;

[0061] S2: 100g DMSO, 3g first-generation polymer, and 0.5g potassium hydroxide were added to the reactor in sequence, stirred to dissolve, heated to 40°C, and then 8g epichlorohydrin was added dropwise. The mixture was reacted for 5h under nitrogen protection, cooled to room temperature, and centrifuged to obtain a polymer cake, which was washed with dichloromethane for 3 times and distilled under reduced pressure at 60°C to obtain a grafted polymer;

[0062] S3: Add 2 g of grafted polymer, 80 ml of anhydrous ethanol, 80 ml of hydrochloric acid, and 10 g of hexadecyldimethylamine into a stirred reactor and reflux for 40 hours. After the reaction is completed, rotary evaporate at 50°C, then recrystallize three times with acetone, and vacuum dry at 65°C to obtain a quaternary ammonium surfactant with a number average molecular weight of 8530.

[0063] Comparative Example 3

[0064] A method for preparing a water injection well pressure-reducing and injection-increasing agent is substantially the same as that in Example 5, except that the quaternary ammonium salt surfactant added in step (2) is prepared by the following method:

[0065] S1: 100 g of deionized water, 40 g of urotropine, 20 g of tromethamine, and 15 g of glacial acetic acid were added to the reactor in sequence, stirred and dissolved, heated to 70°C, reacted for 3 h, cooled to room temperature to separate layers, removed the water layer, and washed with deionized water for 3 times (50 g of deionized water each time) to obtain a first-generation polymer;

[0066] S2: 100g DMSO, 12g first-generation polymer, and 3g potassium hydroxide were added to the reactor in sequence, stirred and dissolved, heated to 40°C, and then 25g epichlorohydrin was added dropwise. The mixture was reacted for 10h under nitrogen protection, cooled to room temperature, and centrifuged to obtain a polymer filter cake, which was washed with dichloromethane for 3 times and distilled under reduced pressure at 60°C to obtain a grafted polymer;

[0067] S3: Add 8 g of grafted polymer, 120 ml of anhydrous ethanol, 120 ml of hydrochloric acid, and 25 g of hexadecyldimethylamine into a stirred reactor and reflux for 50 hours. After the reaction is completed, rotary evaporate at 60°C, then recrystallize three times with acetone, and vacuum dry at 65°C to obtain a quaternary ammonium surfactant with a number average molecular weight of 25,700.

[0068] Comparative Example 4

[0069] The preparation method of a water injection well pressure reducing and injection increasing agent is basically the same as that of Example 5, except that the hexadecyl dimethyl tertiary amine added in step (3) of preparing the quaternary ammonium salt surfactant in Example 2 is replaced by an equal weight of dodecyl dimethyl tertiary amine.

[0070] Comparative Example 5

[0071] The preparation method of a water injection well pressure reducing and injection increasing agent is basically the same as that of Example 5, except that the hexadecyl dimethyl tertiary amine added in step (3) of preparing the quaternary ammonium salt surfactant in Example 2 is replaced by an equal weight of octadecyl dimethyl tertiary amine.

[0072] Comparative Example 6

[0073] A pressure reducing and injection enhancing agent for low permeability oil reservoir water injection wells is prepared by using the raw materials and method of Example 2 in publication number CN109913193A.

[0074] The nonionic surfactant lauric acid diethanolamide used in the examples and comparative examples of the present application is produced by Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.; the betaine-type zwitterionic surfactant erucic acid amide propyl betaine, model EAB-40, used in the examples and comparative examples of the present application, is produced by Shengci (Hubei) Industrial Materials Co., Ltd.; the betaine-type zwitterionic surfactant dodecyl sulfopropyl betaine, model BS-12, used in the examples and comparative examples of the present application, is produced by Shengci (Hubei) Industrial Materials Co., Ltd.; the tetrasodium aminotrimethylenephosphonic acid is a 30wt% aqueous solution, the ethylenediaminetetramethylenephosphonic acid is a 35wt% aqueous solution, and the tetrasodium hydroxyethylidene diphosphonic acid is a 50wt% aqueous solution used in the examples and comparative examples of the present application, which are produced by Shandong Taihe Technology Co., Ltd.

[0075] The injection agents prepared in the examples and comparative examples were tested for surface / interfacial tension, anti-swelling performance, and core displacement experiments. The test results are shown in Table 1.

[0076] Determination of surface tension: Referring to the provisions of the ring method in the petroleum and natural gas industry standard "Surface and interfacial tension determination method" (SY / T5370-2018), the gas-liquid surface tension values ​​of different surfactant solutions were determined. The experimental instrument was the QBZY-2 fully automatic surface interfacial tension meter.

[0077] Determination of anti-swelling performance: According to the provisions of the industry standard "Performance Evaluation Method of Clay Stabilizers for Oil and Gas Field Fracturing Acidification and Water Injection" (SY / T 5971-2016), the anti-swelling effect of the surfactant depressurization and injection system on the cuttings in the reservoir section of the target block was determined. The experimental instrument was KC-GDP1 high-temperature dynamic linear expansion instrument.

[0078] Core flooding experiment:

[0079] 1) The natural core (length 7.5 cm, diameter 2.5 cm) was washed with oil, dried and weighed, and saturated simulated formation water (mineralization 35600 mg·L -1 ), and after 24 h of saturation, the core was taken out and weighed, and the pore volume and porosity were calculated.

[0080] 2) The core was saturated with degassed crude oil from the reservoir, and the crude oil injection rate was 0.05 mL min -1 , and then placed at a reservoir temperature of 80℃ for aging for 24 hours before use.

[0081] 3) Use NaCl brine with the same salinity as the injected water to displace the core at a displacement rate of 0.5 mL min -1, record the pressure changes at different displacement PVs until the pressure stabilizes.

[0082] 4) Inject the surfactant solution at the same displacement flow rate and record the pressure changes.

[0083] 5) Continue to use NaCl brine to displace the core, with the displacement flow rate the same as before, record the change in displacement pressure, stop after displacing 20PV, record the final displacement pressure, and calculate the pressure reduction rate.

[0084] 6) The various indicators of pressure reduction and injection performance in Table 1 are the results of taking the average value of 3 core numbers.

[0085] Table 1

[0086]

[0087] It can be seen from Table 1 that the anti-swelling rate of the pressure-reducing and injection-increasing agent prepared in the present application reaches more than 95%, and the pressure reduction rate reaches more than 38%, indicating that the pressure-reducing and injection-increasing agent prepared in the present application has a good pressure-reducing and injection-increasing effect.

[0088] Comparative Example 1 is different from Example 5 in that no quaternary ammonium salt surfactant is added. As can be seen from Table 1, its blood pressure reduction rate is only 19.6%, and the blood pressure reduction effect is not obvious.

[0089] Comparative Example 2 and Comparative Example 3 are different from those of Example 5, except that the number average molecular weight of the quaternary ammonium salt surfactant used is different. It can be seen from the data in Table 1 that when the number average molecular weight of the quaternary ammonium salt surfactant is lower than 10,000 and higher than 20,000, the anti-swelling rates are 95.3% and 95.8%, respectively, and the pressure reduction rates are lower than 31%, and the pressure reduction and injection enhancement effect is poor.

[0090] Comparative Examples 4 and 5 are different from Example 5 in that the number of carbon atoms of the tertiary amine used in the preparation of the quaternary ammonium salt surfactant is different. It can be seen from the data in Table 1 that the reduction and increase of the alkyl chain will affect the pressure reduction and injection increase performance. The pressure reduction rate is lower than 31%, and the pressure reduction and injection increase effect is poor.

[0091] Comparative Example 6 is a low permeability oil reservoir water injection well pressure reduction and injection enhancement agent prepared using the raw materials and methods of Example 2 in Publication No. CN109913193A. It can be seen from the data in Table 1 that its anti-swelling rate is only 92.0%, and the pressure reduction rate is 22.3%. Both the anti-swelling effect and the pressure reduction and injection enhancement effect are poor.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. However, any equivalent changes, modifications and evolutions made by ordinary technicians in the field without departing from the scope of the technical solution of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A water injection well pressure reducing and injection enhancing agent, characterized in that: The invention comprises the following raw materials in parts by weight: Betaine type amphoteric surfactant: 50-60 parts, Nonionic surfactant: 10-15 parts, Quaternary ammonium salt surfactant: 20-30 parts, Antiscalant: 3-5 parts, Stabilizer: 2-3 parts, Deionized water: 150 parts; The quaternary ammonium salt surfactant is prepared by the following method: S1: Deionized water, hexamethylenetetramine, tromethamine, and glacial acetic acid are added to the reactor in sequence, stirred to dissolve, heated to 65-70°C, reacted for 1-2h, cooled to room temperature, separated, the water layer was removed, and washed with deionized water for 3 times to obtain a first-generation polymer; S2: DMSO, first-generation polymer, and potassium hydroxide are added to the reactor in sequence, stirred and dissolved, heated to 40-60°C, and then epichlorohydrin is added dropwise, reacted under nitrogen protection for 8-10 hours, cooled to room temperature, centrifuged to obtain a polymer filter cake, washed with dichloromethane 3 times, and distilled under reduced pressure at 50-60°C to obtain a grafted polymer; S3: Add grafted polymer, anhydrous ethanol, hydrochloric acid and hexadecyldimethylamine into a stirred reactor and reflux for 40-48 hours. After the reaction is completed, perform rotary evaporation at 40-50°C, then recrystallize three times with acetone, and vacuum dry at 60-70°C to obtain a quaternary ammonium surfactant.

2. A water injection well pressure reducing and injection enhancing agent according to claim 1, characterized in that: In step S1, the mass ratio of deionized water, hexamethylenetetramine, tromethamine and glacial acetic acid is 10:2.5:(1.0-1.2):(0.8-1.0).

3. A water injection well pressure reduction and injection-increasing agent according to claim 1, characterized in that: In step S2, the mass ratio of DMSO, first-generation polymer, epichlorohydrin and potassium hydroxide is 100:(6-8):(18-20):(1-1.5).

4. The water injection well pressure reduction and injection-increasing agent according to claim 1, characterized in that: In step S3, the mass ratio of anhydrous ethanol, hydrochloric acid, graft polymer and hexadecyl dimethyl tertiary amine is 100:100:(2-4):(8-20).

5. The water injection well pressure reduction and injection-increasing agent according to claim 1, characterized in that: The betaine-type surfactant is one of erucic acid amidopropyl betaine, dodecyl sulfopropyl betaine, and tetradecanoyl amidopropyl hydroxypropyl sulfobetaine.

6. The water injection well pressure reduction and injection-increasing agent according to claim 1, characterized in that: The nonionic surfactant is one of lauric acid diethanolamide, lauric acid monoethanolamide and fatty alcohol polyoxyethylene ether.

7. The water injection well pressure reduction and injection-increasing agent according to claim 1, characterized in that: The scale inhibitor is a combination of one or more of ethylenediaminetetramethylenephosphonic acid, tetrasodium aminotrimethylenephosphonic acid, and tetrasodium hydroxyethylidene diphosphonic acid.

8. The water injection well pressure reduction and injection-increasing agent according to claim 1, characterized in that: The stabilizer is a combination of one or more of potassium carbonate, potassium chloride and potassium humate.

9. A method for preparing the water injection well pressure reducing and injection enhancing agent according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) Weigh by weight: 50-60 parts of betaine type amphoteric surfactant, 10-15 parts of nonionic surfactant, 20-30 parts of quaternary ammonium salt surfactant, 3-5 parts of scale inhibitor, 2-3 parts of stabilizer, and 150 parts of deionized water; (2) Deionized water, betaine-type surfactant, nonionic surfactant, quaternary ammonium salt-type surfactant, scale inhibitor, and stabilizer are sequentially added to the reactor, stirred, and slowly heated to 40-45° C., and kept warm for 1-2 hours to obtain a water injection well pressure reduction and injection enhancement agent.

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