Composite self-thickening diverting acid and preparation method thereof

Abstract

The invention relates to the technical field of auxiliary materials for oil and gas exploitation, and particularly discloses a composite self-thickening diverting acid and a preparation method thereof, the composite self-thickening diverting acid comprises hydrochloric acid, a diverting agent, a cationic surfactant and a betaine zwitterionic surfactant according to a mass ratio of (10-20): (1-1.2): (0.1-0.5): (0.1-0.5); the diverting agent is prepared from the following components in parts by mole: 1.5 to 3 parts of an acrylamide monomer, 1 to 2.5 parts of a methacryloyloxyethyl trimethyl ammonium chloride monomer, 0.5 to 2 parts of a 2-acrylamide-2-methylpropanesulfonic acid monomer and 0.6 to 1.2 parts of an alkene dimethyl allyl octadecyl ammonium chloride monomer through a polymerization reaction. The method has the advantages that the cost is low, the fresh acid viscosity is low, the method is easy to pump into the reservoir, the temperature resistance is good, iron ion and zirconium ion cross-linking agents harmful to the reservoir are not added, the self-thickening effect is achieved through calcium ions generated through acid-rock reaction, the steering effect can be effectively achieved, and then uniform acid distribution is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of auxiliary materials for oil and gas exploitation, in particular to a composite self-thickening diverting acid and a preparation method thereof. Background Art

[0002] Acidizing is an important measure to increase the production and injection of oil and gas reservoirs. my country's carbonate reservoirs are relatively old in geological age, buried deep, with high formation temperature and heterogeneity. When acidizing heterogeneous reservoirs, the acid often moves along the high permeability area, reducing the acidizing effect. In order to improve the effect, acidizing diversion technology is usually used.

[0003] At present, acidizing diversion technology is divided into mechanical diversion and chemical diversion. Mechanical diversion is mainly achieved by lowering packers or plugging balls. Packers are mainly suitable for wells with good downhole structures and obvious boundary layers; plugging balls are mainly suitable for oil and gas wells with perforated completion, and high displacement is required during construction. Chemical diversion mainly includes foam, polymer and viscoelastic surfactant. Foam blocks the high permeability layer through the Jamin effect, reduces acid injection, and improves the acidizing efficiency of the low permeability layer. However, problems such as poor high temperature stability and filtration loss of high permeability reservoirs restrict its scope of application and effectiveness. Polymers cross-link with cross-linking agents under formation conditions to form high-viscosity fluids to block high permeability layers. This type of diversion has a narrow pH range, is not easy to break, and has great damage to the formation. Viscoelastic surfactants mainly achieve diversion through changes in viscosity under different conditions. This technology has problems such as large amount of surfactant, high cost, and poor temperature resistance. Therefore, it is difficult for the current acidizing diversion technology to simultaneously meet the bottleneck problems of high temperature resistance, low damage, and low cost.

[0004] Based on this, our company has developed a composite self-thickening diversion acid, which is a non-cross-linked polymer diversion acid system. In this diversion acid system, the corresponding acid can react with the acid rock, and the viscosity changes, so as to achieve the diversion of the acid in the high permeability layer. In addition, the system does not require cross-linking agents and has little damage to the formation. In addition, it is a polymer with the advantages of small addition amount, strong temperature resistance and relatively low cost. This solves the bottleneck problem encountered by the existing diversion acid and provides a new research idea for acid diversion technology. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a composite self-thickening diverter acid and a preparation method thereof, which solves the problems of large amount of diverter added in the prior art diverter acid, high cost, poor temperature resistance, and irreversible damage to the formation caused by the cross-linking agent therein, and also solves the problem that the prior art diverter acid cannot effectively and uniformly acidify heterogeneous carbonate reservoirs.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] According to the first aspect of the present application, a composite self-thickening diverting acid is provided, comprising: hydrochloric acid, a diverting agent, a cationic surfactant, and a betaine zwitterionic surfactant, wherein the weight ratio of the four is (10-20): (1-1.2): (0.1-0.5): (0.1-0.5), prepared;

[0008] The diverting agent is prepared by polymerization reaction of 1.5-3 parts of acrylamide monomer, 1-2.5 parts of methacryloyloxyethyl trimethyl ammonium chloride monomer, 0.5-2 parts of 2-acrylamide-2-methylpropane sulfonic acid monomer and 0.6-1.2 parts of allyl dimethyl allyl octadecyl ammonium chloride monomer in molar ratio.

[0009] In some embodiments, the mass fraction of the cationic surfactant is octadecyltrimethylammonium chloride cationic surfactant, and the betaine zwitterionic surfactant is cocamidopropyl hydroxysulfobetaine zwitterionic surfactant.

[0010] According to the second aspect of the present application, a method for preparing a composite self-thickening steering acid is provided, the preparation steps being:

[0011] S1. Preparation of diverting agent;

[0012] First, allyl dimethyl allyl octadecyl ammonium chloride and methacryloyloxyethyl trimethyl ammonium chloride are weighed, and the two are placed in a container together, and a certain amount of water is added to initially dissolve them; then, acrylamide and 2-acrylamide-2-methylpropane sulfonic acid are weighed and placed in the container together, and then stirred until fully dissolved to obtain a mixed solution;

[0013] The mixed solution was placed in a constant temperature water bath and heated and stirred for preheating, the pH value was adjusted to neutral, and then heated and stirred again;

[0014] When the temperature rises to the specified reaction temperature, the initiator solution is added, and after a certain period of constant temperature reaction, it is cooled to room temperature to obtain the preliminary product of the diverting agent;

[0015] The gel solid of the preliminary product of the diverting agent is fully soaked in anhydrous ethanol, washed and shredded for multiple times, and the shredded particles are dried in a vacuum oven, and then crushed to obtain a finished diverting agent product in the form of white powder;

[0016] S2, preparation of steering acid;

[0017] According to the proportion, a diverting agent is added to hydrochloric acid with a concentration of 10%-20%, and then octadecyl trimethyl ammonium chloride cationic surfactant and cocamidopropyl hydroxysulfobetaine zwitterionic surfactant are added.

[0018] In some embodiments, the initiator is selected from one or more of azobisisobutyramidine hydrochloride, ammonium persulfate / sodium bisulfite and potassium persulfate / sodium bisulfite. The initiator is preferably azobisisobutyramidine hydrochloride.

[0019] In some embodiments, the amount of the initiator is 0.4%-0.8% of the total weight of dimethylallyl octadecyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, acrylamide, and 2-acrylamide-2-methylpropane sulfonic acid in the diverter; when used, the initiator is first dissolved in water to form an initiator solution with a concentration of 25%-30%.

[0020] For ease of understanding, the principles and core points of this solution are explained:

[0021] In the synthesized diverter monomer, since allyl dimethyl octadecyl ammonium chloride has a -C=C- double bond, it can be ion polymerized with methacryloyloxyethyl trimethyl ammonium chloride monomer and acrylamide, which also have a -C=C- double bond, under the action of the hair dryer to form a new copolymer, thereby obtaining a polymer acid diverter. Among them, acrylamide can increase the molecular weight of the polymer and improve the viscosity when preparing the diverter acid; the hydrophobic long chain structure of allyl dimethyl octadecyl ammonium chloride can ensure that the molecular structure of the diverter acid undergoes rich associative entanglement behavior; methacryloyloxyethyl trimethyl ammonium chloride increases the water solubility and acid resistance of the diverter; 2-acrylamide-2-methylpropane sulfonic acid is added with sulfonate ions to enhance the temperature resistance, and also provides conditions for the self-assembly behavior of the cationic surfactant. In addition, the cocoamidopropyl hydroxysulfobetaine zwitterionic surfactant is used for reverse stimulation to promote the associative behavior; the cationic head group used can be electrostatically bonded with the polymer, and the hydrophobic long chain structure further increases the volume of the associative aggregate.

[0022] The present invention has the following advantages:

[0023] (1) The polymers that have been hydrophobically modified and temperature-resistant have better viscosity-increasing and temperature-resistant properties; (2) The cocamidopropyl hydroxysulfobetaine zwitterionic surfactant is used for reverse stimulation to promote the association behavior, and the hydrophobic long-chain structure in the octadecyltrimethylammonium chloride cationic surfactant further increases the volume of the association aggregates to ensure the high efficiency of the steering behavior; (3) The self-thickening steering acid has a small molecular weight, good flow properties in fresh acid liquid, and is easy to pump into the reservoir; (4) The entire steering acid system is a non-cross-linked polymer steering acid system, and does not use iron ion and zirconium ion cross-linking agents that are harmful to the reservoir, so it causes less damage to the reservoir; (5) The amount added is small, and the raw materials used are low in cost and easy to obtain. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1The structural composition of the temperature-acidification resistant diverter prepared in Example 2 was determined using an infrared spectrometer. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following description.

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are 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 creative work are within the scope of protection of the present invention.

[0027] According to the first aspect of the present application, a composite self-thickening steering acid is provided in this specific embodiment.

[0028] In the composite self-thickening diverting acid, hydrochloric acid with a concentration of 10%-20%, a diverting agent, a cationic surfactant, and a betaine zwitterionic surfactant, the mass ratio of the four is (10-20): (1-1.2): (0.1-0.5): (0.1-0.5), and the diverting acid is formed by preparation;

[0029] Among them, in the diverting agent, calculated by molar ratio, it is prepared by polymerization reaction of 1.5-3 parts of acrylamide monomer, 1-2.5 parts of methacryloyloxyethyl trimethyl ammonium chloride monomer, 0.5-2 parts of 2-acrylamide-2-methylpropane sulfonic acid monomer, and 0.6-1.2 parts of allyl dimethyl allyl octadecyl ammonium chloride monomer.

[0030] In some embodiments, the cationic surfactant is octadecyltrimethylammonium chloride cationic surfactant, and the betaine zwitterionic surfactant is cocamidopropylhydroxysulfobetaine zwitterionic surfactant.

[0031] According to the second aspect of the present application, this specific embodiment also provides a method for preparing a composite self-thickening steering acid.

[0032] The specific preparation steps of the steering acid are:

[0033] S1. Preparation of diverting agent;

[0034] Weigh allyl dimethyl octadecyl ammonium chloride and methacryloyloxyethyl trimethyl ammonium chloride, put them together in a three-necked flask, add a certain amount of pure water to initially dissolve; then weigh acrylamide and 2-acrylamide-2-methylpropane sulfonic acid and put them together in the three-necked flask, stir until fully dissolved, and obtain a mixed solution;

[0035] The mixed solution is placed in a constant temperature water bath and heated and stirred for preheating, and the pH value of the solution is adjusted to neutral, and then heated and stirred;

[0036] When the temperature rises to the specified reaction temperature (predetermined system reaction temperature), add the initiator solution prepared by dissolving the initiator in pure water in advance, react at constant temperature for a certain period of time, and then cool to room temperature to obtain the preliminary product of the diverting agent;

[0037] The gel solid of the preliminary product of the diverting agent is fully soaked in anhydrous ethanol, and washed and shredded multiple times to form particles; the shredded particles are dried in a vacuum oven, and crushed by a machine to obtain a finished diverting agent product in the form of white powder;

[0038] S2, preparation of steering acid;

[0039] 1-1.2 parts of a diverting agent are added to 10-20 parts of 10%-20% hydrochloric acid, and then 0.1-0.5 parts of octadecyl trimethyl ammonium chloride cationic surfactant and 0.1-0.5 parts of cocamidopropyl hydroxysulfobetaine zwitterionic surfactant are added.

[0040] In some embodiments, the initiator is selected from one or more of azobisisobutyramidine hydrochloride, ammonium persulfate / sodium bisulfite and potassium persulfate / sodium bisulfite. Azobisisobutyramidine hydrochloride is preferred.

[0041] In some embodiments, the amount of initiator used is 0.4%-0.8% of the total weight of dimethylallyl octadecyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, acrylamide, and 2-acrylamide-2-methylpropane sulfonic acid in the diverter; when the initiator is used, it is first dissolved in water to form an initiator solution with a concentration of 25%-30%.

[0042] The idea of ​​the present invention is specifically exemplified below.

[0043] (Example 1)

[0044] The preparation method of the second aspect is adopted; wherein the molar ratio of the monomers is acrylamide: methacryloyloxyethyl trimethyl ammonium chloride: 2-acrylamide-2-methylpropane sulfonic acid: allyl dimethyl octadecyl ammonium chloride = 1.5:1:1:0.6, and the monomers are placed in a container and dissolved and then the pH is adjusted to about 7; the reaction is carried out at a reaction temperature of 50°C for 5 hours, azobisisobutyramidine hydrochloride (V50) is adopted as an initiator, and the concentration obtained after the initiator is dissolved in water is 25%, and the amount of the initiator is 0.8% of the total weight of acrylamide, methacryloyloxyethyl trimethyl ammonium chloride, 2-acrylamide-2-methylpropane sulfonic acid, and allyl dimethyl octadecyl ammonium chloride; after the polymerization reaction is completed, the initial initiator product is washed, shredded, dried, and crushed to obtain the finished initiator product. A steering agent is added to hydrochloric acid with a concentration of 20%, and then octadecyl trimethyl ammonium chloride cationic surfactant and cocamidopropyl hydroxysulfobetaine zwitterionic surfactant are added to prepare a steering acid, and the mass ratio of the four is 20:1:0.1:0.5.

[0045] (Example 2)

[0046] The preparation method of the second aspect is adopted; wherein the molar ratio of the monomers is acrylamide: methacryloyloxyethyl trimethyl ammonium chloride: 2-acrylamide-2-methylpropane sulfonic acid: allyl dimethyl octadecyl ammonium chloride = 2:1:0.5:0.8, and the monomers are placed in a container and dissolved and then the pH is adjusted to about 7; the reaction is carried out at a reaction temperature of 50°C for 5 hours, azobisisobutyramidine hydrochloride (V50) is used as an initiator, and the concentration obtained after the initiator is dissolved in water is 30%, and the amount of the initiator is 0.4% of the total weight of acrylamide, methacryloyloxyethyl trimethyl ammonium chloride, 2-acrylamide-2-methylpropane sulfonic acid, and allyl dimethyl octadecyl ammonium chloride; after the polymerization reaction is completed, the initial initiator product is washed, shredded, dried, and crushed to obtain the finished initiator product. A steering agent is added to hydrochloric acid with a concentration of 20%, and then octadecyl trimethyl ammonium chloride cationic surfactant and cocamidopropyl hydroxysulfobetaine zwitterionic surfactant are added to prepare a steering acid, and the mass ratio of the four is 20:1:0.5:0.1.

[0047] (Example 3)

[0048] The preparation method of the second aspect is adopted; wherein the molar ratio of the monomers is acrylamide: methacryloyloxyethyl trimethyl ammonium chloride: 2-acrylamide-2-methylpropane sulfonic acid: allyl dimethyl octadecyl ammonium chloride = 3:2.5:1:1.2, and the monomers are placed in a container and dissolved and then the pH is adjusted to about 7; the reaction is carried out at a reaction temperature of 50°C for 5 hours, azobisisobutyramidine hydrochloride (V50) is used as an initiator, and the concentration obtained after the initiator is dissolved in water is 30%, and the amount of the initiator is 0.6% of the total weight of acrylamide, methacryloyloxyethyl trimethyl ammonium chloride, 2-acrylamide-2-methylpropane sulfonic acid, and allyl dimethyl octadecyl ammonium chloride; after the polymerization reaction is completed, the initial initiator product is washed, shredded, dried, and crushed to obtain the finished initiator product. A diverting agent is added to hydrochloric acid with a concentration of 20%, and then octadecyl trimethyl ammonium chloride cationic surfactant and cocamidopropyl hydroxysulfobetaine zwitterionic surfactant are added to prepare a diverting acid, and the mass ratio of the four is 20:1.2:0.1:0.1.

[0049] (Example 4)

[0050] The preparation method of the second aspect is adopted; wherein the molar ratio of the monomers is acrylamide: methacryloyloxyethyl trimethyl ammonium chloride: 2-acrylamide-2-methylpropane sulfonic acid: allyl dimethyl octadecyl ammonium chloride = 1.5:2:2:0.8, and the monomers are placed in a container and dissolved and then the pH is adjusted to about 7; the reaction is carried out at a reaction temperature of 50°C for 5 hours, azobisisobutyramidine hydrochloride (V50) is used as an initiator, and the concentration obtained after the initiator is dissolved in water is 25%, and the amount of the initiator is 0.4% of the total weight of acrylamide, methacryloyloxyethyl trimethyl ammonium chloride, 2-acrylamide-2-methylpropane sulfonic acid, and allyl dimethyl octadecyl ammonium chloride; after the polymerization reaction is completed, the initial initiator product is washed, shredded, dried, and crushed to obtain the finished initiator product. A steering agent is added to hydrochloric acid with a concentration of 20%, and then octadecyl trimethyl ammonium chloride cationic surfactant and cocamidopropyl hydroxysulfobetaine zwitterionic surfactant are added to prepare a steering acid, and the mass ratio of the four is 20:1:0.2:0.2.

[0051] (Example 5)

[0052] The preparation method of the second aspect is adopted; wherein the molar ratio of the monomers is acrylamide: methacryloyloxyethyl trimethyl ammonium chloride: 2-acrylamide-2-methylpropane sulfonic acid: allyl dimethyl octadecyl ammonium chloride = 1.5:1:0.5:0.8, and the monomers are placed in a container and dissolved and then the pH is adjusted to about 7; the reaction is carried out at a reaction temperature of 50°C for 5 hours, azobisisobutyramidine hydrochloride (V50) is used as an initiator, and the concentration obtained after the initiator is dissolved in water is 30%, and the amount of the initiator is 0.6% of the total weight of acrylamide, methacryloyloxyethyl trimethyl ammonium chloride, 2-acrylamide-2-methylpropane sulfonic acid, and allyl dimethyl octadecyl ammonium chloride; after the polymerization reaction is completed, the initial initiator product is washed, shredded, dried, and crushed to obtain the finished initiator product. A steering agent is added to hydrochloric acid with a concentration of 20%, and then octadecyl trimethyl ammonium chloride cationic surfactant and cocamidopropyl hydroxysulfobetaine zwitterionic surfactant are added to prepare a steering acid, and the mass ratio of the four is 20:1:0.2:0.3.

[0053] (Example 6)

[0054] The preparation method of the second aspect is adopted; wherein the molar ratio of the monomers is acrylamide: methacryloyloxyethyl trimethyl ammonium chloride: 2-acrylamide-2-methylpropane sulfonic acid: allyl dimethyl octadecyl ammonium chloride = 1.5:1:0.5:0.8, and the monomers are placed in a container and dissolved and then the pH is adjusted to about 7; the reaction is carried out at a reaction temperature of 50°C for 5 hours, azobisisobutyramidine hydrochloride (V50) is used as an initiator, and the concentration obtained after the initiator is dissolved in water is 25%, and the amount of the initiator is 0.6% of the total weight of acrylamide, methacryloyloxyethyl trimethyl ammonium chloride, 2-acrylamide-2-methylpropane sulfonic acid, and allyl dimethyl octadecyl ammonium chloride; after the polymerization reaction is completed, the initial initiator product is washed, shredded, dried, and crushed to obtain the finished initiator product. A steering agent is added to hydrochloric acid with a concentration of 10%, and then octadecyl trimethyl ammonium chloride cationic surfactant and cocamidopropyl hydroxysulfobetaine zwitterionic surfactant are added to prepare a steering acid, and the mass ratio of the four is 10:1:0.5:0.5.

[0055] (Example 7)

[0056] The preparation method of the second aspect is adopted; wherein the molar ratio of the monomers is acrylamide: methacryloyloxyethyl trimethyl ammonium chloride: 2-acrylamide-2-methylpropane sulfonic acid: allyl dimethyl octadecyl ammonium chloride = 1.5:1:0.5:0.8, and the monomers are placed in a container and dissolved and then the pH is adjusted to about 7; the reaction is carried out at a reaction temperature of 50°C for 5 hours, azobisisobutyramidine hydrochloride (V50) is used as an initiator, and the concentration obtained after the initiator is dissolved in water is 26%, and the amount of the initiator is 0.8% of the total weight of acrylamide, methacryloyloxyethyl trimethyl ammonium chloride, 2-acrylamide-2-methylpropane sulfonic acid, and allyl dimethyl octadecyl ammonium chloride; after the polymerization reaction is completed, the initial initiator product is washed, shredded, dried, and crushed to obtain the finished initiator product. A steering agent is added to hydrochloric acid with a concentration of 15%, and then octadecyl trimethyl ammonium chloride cationic surfactant and cocamidopropyl hydroxysulfobetaine zwitterionic surfactant are added to prepare a steering acid, and the mass ratio of the four is 15:1.2:0.1:0.5.

[0057] The diverted acid solution obtained in the above Examples 1-5 was evaluated by placing the acid solution in a constant temperature water bath at 90°C, adding CaCO3 powder 4 times to simulate different stages of the acid-rock reaction according to the stoichiometric relationship, covering the beaker with plastic wrap to prevent a large amount of hydrochloric acid from volatilizing, and after sufficient stirring and defoaming in the constant temperature water bath, placing the acid solution with different reaction degrees in the sample cup of a six-speed rotary viscometer, and measuring the apparent viscosity at a speed of 100 r / min until the acid solution reacts to residual acid (pH = 5-6). The results are shown below:

[0058] Table 1: Apparent viscosity of the diverting acid at different reaction stages (90°C)

[0059]

[0060] In Table 1, AM refers to acrylamide, DMC refers to methacryloyloxyethyltrimethylammonium chloride, AMPS refers to 2-acrylamide-2-methylpropanesulfonic acid, and C-18 refers to allyl dimethylallyl octadecyl ammonium chloride.

[0061] Test Example 1

[0062] The structural composition of the temperature-acidification resistant diverter prepared in Example 2 was determined using an infrared spectrometer.

[0063] The temperature-resistant acidification diverter obtained by the preparation method of Example 2 is characterized by its infrared spectrum as follows: Figure 1 As shown, the 3N-H stretching vibration absorption peak is at 3440 cm -1 and 3200cm -1 The stretching vibration absorption peak of -CH3 is at 2927cm -1The stretching vibration absorption peak of -CH2- is at 2854cm -1 The C=O stretching vibration absorption peak on the ester is at 1733 cm -1 The stretching vibration absorption peak of C=O on the amide is at 1688 cm -1 The in-plane bending vibration absorption peak of NH is at 1550cm -1 The CN in-plane bending vibration absorption peak is at 1475 cm -1 The stretching vibration absorption peak of CO is at 1200 cm -1 The sulfonate stretching vibration absorption peak is at 1041 cm -1 Place.

[0064] According to the above analysis, it can be seen that the temperature-resistant and acid-resistant diverting agent prepared in Example 2 contains the initially designed groups, which indicates that the structure of the diverting agent is consistent with the target product.

[0065] The above embodiments only express preferred implementation modes, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Claims

1. A composite self-thickening diverter acid, characterized in that: include: Hydrochloric acid, diverting agent, cationic surfactant, betaine zwitterionic surfactant, and the mass ratio of the four is (10-20): (1-1.2): (0.1-0.5): (0.1-0.5); The diverting agent is prepared by polymerization reaction of 1.5-3 parts of acrylamide monomer, 1-2.5 parts of methacryloyloxyethyl trimethyl ammonium chloride monomer, 0.5-2 parts of 2-acrylamide-2-methylpropane sulfonic acid monomer and 0.6-1.2 parts of allyl dimethyl allyl octadecyl ammonium chloride monomer in molar ratio.

2. A composite self-thickening steering acid according to claim 1 or 2, characterized in that: The mass fractions are as follows: the cationic surfactant is octadecyltrimethylammonium chloride cationic surfactant, and the zwitterionic surfactant is cocamidopropylhydroxysulfobetaine zwitterionic surfactant.

3. The method for preparing the composite self-thickening steering acid according to any one of claims 1 or 2, characterized in that: The preparation steps are: S1. Preparation of diverting agent; First, allyl dimethyl allyl octadecyl ammonium chloride and methacryloyloxyethyl trimethyl ammonium chloride are weighed, and the two are placed in a container together, and a certain amount of water is added to initially dissolve them; then, acrylamide and 2-acrylamide-2-methylpropane sulfonic acid are weighed and placed in the container together, and then stirred until fully dissolved to obtain a mixed solution; The mixed solution was placed in a constant temperature water bath and heated and stirred for preheating, the pH value was adjusted to neutral, and then heated and stirred again; When the temperature rises to the specified reaction temperature, the initiator solution is added, and after a certain period of constant temperature reaction, it is cooled to room temperature to obtain the preliminary product of the diverting agent; The gel solid of the preliminary product of the diverting agent is fully soaked in anhydrous ethanol, washed and shredded for multiple times, and the shredded particles are dried in a vacuum oven, and then crushed to obtain a finished diverting agent product in the form of white powder; S2, preparation of steering acid; According to the proportion, a diverting agent is added to hydrochloric acid with a concentration of 10%-20%, and then octadecyl trimethyl ammonium chloride cationic surfactant and cocamidopropyl hydroxysulfobetaine zwitterionic surfactant are added.

4. The method for preparing the composite self-thickening steering acid according to claim 3, characterized in that: The initiator is selected from one or more of azobisisobutylamidine hydrochloride, ammonium persulfate / sodium bisulfite and potassium persulfate / sodium bisulfite.

5. The method for preparing the composite self-thickening steering acid according to claim 4, characterized in that: The amount of the initiator is 0.4%-0.8% of the total weight of allyl dimethyl octadecyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, acrylamide, and 2-acrylamide-2-methylpropane sulfonic acid in the diverter; When used, the initiator is first dissolved in water to form an initiator solution with a concentration of 25%-30%.

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