Anti-swelling agent, preparation method and application of anti-swelling agent in fracturing

Abstract

The invention provides an anti-swelling agent, a preparation method and application of the anti-swelling agent in fracturing. The anti-swelling agent is prepared from the following raw materials: dimethyl diallyl ammonium chloride, an auxiliary agent, an initiator and water. The anti-swelling agent disclosed by the invention is a cationic polymer taking dimethyl diallyl ammonium chloride as a main body, has good water solubility, is neutral in aqueous solution, generates a quaternary ammonium salt linear acting group with positive charges after being ionized in the aqueous solution, and has bridging and sweeping functions of a common viscosity stabilizer; and the material also has very strong electricity neutralization capability. According to the principle, cationic groups attract clay ions with negative charges, surface charges of colloid particles are reduced and neutralized, meanwhile, a clay colloid diffusion layer is compressed to enable the particles to be agglomerated, flocculation sedimentation is generated by means of the adhesion bridging effect of molecular chains, and clay expansion and dispersion migration are rapidly prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield exploitation, and specifically, to an anti-swelling agent, a preparation method thereof, and an application thereof in fracturing. Background Art

[0002] Low-permeability tight reservoirs and shale oil reservoirs have a relatively high shale content. Fracturing operations can cause the hydration swelling, dispersion, and migration of shale minerals in the reservoir, reducing the fracturing effect and affecting the construction success rate. To improve the fracturing effect, during the fracturing process of oil and gas wells, an anti-swelling agent is generally required to inhibit shale swelling.

[0003] Currently, commonly used anti-swelling agents at home and abroad include inorganic salts, cationic polymers, and small molecules. Inorganic salt anti-swelling agents have disadvantages such as poor performance under alkaline conditions and poor erosion resistance; cationic polymer anti-swelling agents have good anti-swelling effects and erosion resistance. However, the results of indoor core flow tests show that high-molecular-weight organic cationic polymer anti-swelling agents are not suitable for low-permeability reservoirs because they are large in molecular weight and easily form plugs in pores, blocking the reservoir; conventional small-molecule anti-swelling agents also have disadvantages such as a large dosage and poor anti-swelling effects.

[0004] Most conventional clay stabilizers are applied in drilling fluids and water injection processes. There is little research on the problem of the decline in natural gas permeability caused by the binding effect of organic matter on water. If it is to be applicable to low-permeability tight and shale oil reservoirs, the high-efficiency clay anti-swelling agent used in fracturing needs to simultaneously meet performance requirements such as being positively charged, having a low molecular weight, being able to produce multi-point adsorption, having strong water washing resistance, and being well soluble in water. There are few clay stabilizer products that meet the above requirements, or the price of foreign-made clay stabilizers that meet the requirements is too high.

[0005] Therefore, there is an urgent need to develop an anti-swelling agent for fracturing with a low dosage and a high anti-swelling rate that is applicable to domestic low-permeability tight reservoirs and shale oil reservoirs. Summary of the Invention

[0006] In view of this, the present invention aims to solve the technical problems of high dosage and low anti-swelling rate of conventional anti-swelling agents.

[0007] The first aspect of the present invention provides an anti-swelling agent.

[0008] The second aspect of the present invention provides a preparation method of an anti-swelling agent.

[0009] The third aspect of the present invention provides an application of an anti-swelling agent.

[0010] Specifically, the present invention is realized through the following technical solutions:

[0011] The first aspect of the technical solution of the present invention provides an anti-swelling agent, and the raw materials for preparing the anti-swelling agent include dimethyldiallylammonium chloride, an auxiliary agent, an initiator and water.

[0012] In some technical solutions, optionally, the mass percentage of dimethyldiallylammonium chloride in the raw materials for preparation is greater than or equal to 50% and less than or equal to 55%; the mass percentage of the auxiliary agent in the raw materials for preparation is greater than or equal to 0.08% and less than or equal to 0.12%; the mass percentage of the initiator in the raw materials for preparation is greater than or equal to 1% and less than or equal to 1.4%.

[0013] In some technical solutions, optionally, dimethyldiallylammonium chloride is prepared from dimethylamine and allyl chloride.

[0014] In some technical solutions, optionally, the auxiliary agent includes disodium ethylenediaminetetraacetate.

[0015] In some technical solutions, optionally, disodium ethylenediaminetetraacetate is prepared from chloroacetic acid, ethylenediamine, ice, sodium hydroxide, and hydrochloric acid.

[0016] In some technical solutions, optionally, the initiator includes ammonium persulfate.

[0017] The second aspect of the present invention provides a method for preparing an anti-swelling agent, including the following steps: adding dimethyldiallylammonium chloride, an auxiliary agent, an initiator and water into a reaction kettle to cause the dimethyldiallylammonium chloride to undergo a polymerization reaction to generate an anti-swelling agent in the reaction kettle; wherein, the reaction pressure in the reaction kettle is less than or equal to 0.25 MPa, and the reaction temperature is greater than or equal to 60 °C.

[0018] In some technical solutions, optionally, the preparation steps of dimethyldiallylammonium chloride are as follows: dropping allyl chloride into a first mixed solution including dimethylamine, a basic resin and a phase transfer catalyst to obtain a second mixed solution; heating the second mixed solution to greater than or equal to 40 °C and refluxing for 3 to 8 hours, and when the pH value of the second mixed solution is greater than 7, performing reduced pressure and distillation on the second mixed solution in sequence to obtain dimethyldiallylammonium chloride.

[0019] In some technical solutions, optionally, the basic resin includes a basic styrene anion exchange resin.

[0020] In some technical solutions, optionally, the phase transfer catalyst includes at least one of tetraethylammonium bromide or tetraethylammonium chloride.

[0021] In some technical solutions, optionally, the mass ratio of dimethylamine to allyl chloride is greater than or equal to 1:1.4 and less than or equal to 1:1.

[0022] In some technical solutions, optionally, the auxiliary agent includes disodium ethylenediaminetetraacetate. The preparation steps of disodium ethylenediaminetetraacetate are as follows: Mix chloroacetic acid, ice and sodium hydroxide to obtain a third mixed solution, stir the third mixed solution and add ethylenediamine to the third mixed solution to generate disodium ethylenediaminetetraacetate.

[0023] The third aspect of the present invention provides an application of an anti-swelling agent, where the anti-swelling agent is the anti-swelling agent provided by any one of the technical solutions in the first aspect of the present invention, or the anti-swelling agent is prepared by the preparation method of the anti-swelling agent provided by any one of the technical solutions in the second aspect of the present invention.

[0024] In addition, optionally, the present invention also provides a method for determining the content of an anti-swelling agent. The anti-swelling agent is the anti-swelling agent provided by any one of the technical solutions in the first aspect of the present invention or the anti-swelling agent prepared by the preparation method of the anti-swelling agent provided by any one of the technical solutions in the second aspect of the present invention. The method for determining the content of the anti-swelling agent includes: determining the shale content of the formation; and determining the content of the anti-swelling agent required for the formation according to the shale content of the formation and the corresponding relationship between the shale content and the anti-swelling agent content.

[0025] In addition, optionally, the present invention also provides a device for determining the content of an anti-swelling agent, including: a determination module for determining the shale content of the formation; and the determination module is further configured to determine the content of the anti-swelling agent required for the formation according to the shale content and the corresponding relationship between the shale content and the anti-swelling agent content.

[0026] In addition, optionally, the present invention also provides a device for determining the content of an anti-swelling agent, including: a memory and a processor. The memory stores a program, and when the processor executes the program, the steps of the method for determining the content of the anti-swelling agent provided by the fourth aspect of the present invention are implemented. Description of the Drawings

[0027] The drawings here are incorporated into the specification and form a part of this specification, showing the embodiments consistent with the present invention, and are used together with the specification to explain the principles of the present invention.

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or related technologies. Obviously, for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0029] Figure 1 One of the preparation process schematic diagrams of the preparation method of the anti-swelling agent provided by the embodiment of the present invention;

[0030] Figure 2 Another preparation process schematic diagram of the preparation method of the anti-swelling agent provided by the embodiment of the present invention. Detailed Description of the Invention

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0032] An embodiment of the first aspect of the present invention provides an anti-swelling agent. The raw materials for preparing the anti-swelling agent include dimethyldiallylammonium chloride, an auxiliary agent, an initiator, and water.

[0033] The anti-swelling agent of the present invention is a cationic polymer with dimethyldiallylammonium chloride as the main body. It has good water solubility, the aqueous solution is neutral, and after ionization in the aqueous solution, it generates positively charged quaternary ammonium salt linear functional groups. In addition to the bridging and sweeping functions of general viscosifiers, it also has a relatively strong electro-neutralization ability. The principle is that the cationic groups attract negatively charged clay ions, reduce and neutralize the surface charges of colloidal particles, and at the same time compress the diffuse layer of the clay colloid to cause the fine particles to aggregate, and produce flocculation sedimentation by means of the adhesion and bridging action of the molecular chains, quickly preventing clay swelling and dispersion migration. The polymerization reaction equation of dimethyldiallylammonium chloride is as follows:

[0034]

[0035] The present invention researches and develops a small-molecule anti-swelling agent for fracturing with a small dosage and good anti-swelling effect. It has the function of protecting the reservoir, good anti-swelling performance, low use concentration, small adsorption damage to the formation, long anti-swelling period, good water washing resistance, can extend the water injection period, and can achieve good effects of increasing oil production in oil wells and increasing water injection in water wells. It has the characteristics of good temperature and salt resistance, low price, and simple process, and is especially suitable for the exploitation of low-permeability tight reservoirs and shale oil reservoirs.

[0036] In some embodiments, optionally, the mass percentage of dimethyldiallylammonium chloride in the raw materials for preparation is greater than or equal to 50% and less than or equal to 55%; the mass percentage of the auxiliary agent in the raw materials for preparation is greater than or equal to 0.08% and less than or equal to 0.12%; the mass percentage of the initiator in the raw materials for preparation is greater than or equal to 1% and less than or equal to 1.4%; the balance is water, that is, the mass percentage of water in the raw materials for preparation is greater than or equal to 44% and less than or equal to 48%.

[0037] In this embodiment, by controlling the mass ratios of dimethyldiallylammonium chloride, the auxiliary agent, the initiator, and water, the polymerization reaction of dimethyldiallylammonium chloride can occur better, thereby improving the anti-swelling performance. Optionally, the mass percentage of dimethyldiallylammonium chloride in the preparation raw materials is equal to 55%; the mass percentage of the auxiliary agent in the preparation raw materials is equal to 0.1%; the mass percentage of the initiator in the preparation raw materials is equal to 1.2%; the balance is water.

[0038] In some embodiments, optionally, dimethyldiallylammonium chloride is prepared from dimethylamine and allyl chloride.

[0039] In some embodiments, optionally, the auxiliary agent includes disodium ethylenediaminetetraacetate.

[0040] In this embodiment, the auxiliary agent includes disodium ethylenediaminetetraacetate. Using disodium ethylenediaminetetraacetate as the auxiliary agent can greatly accelerate the polymerization rate of dimethyldiallylammonium chloride. Of course, conventional auxiliary agents can also be selected, such as one or a combination of two or more of tetrasodium ethylenediaminetetraacetate, sodium gluconate, or sodium ethylenediaminetetramethylenephosphonate.

[0041] In some embodiments, optionally, disodium ethylenediaminetetraacetate is prepared from chloroacetic acid, ethylenediamine, ice, sodium hydroxide, and hydrochloric acid.

[0042] In some embodiments, optionally, the initiator includes ammonium persulfate.

[0043] In this embodiment, using ammonium persulfate as the initiator can accelerate the polymerization rate of dimethyldiallylammonium chloride. Of course, conventional initiators can also be selected, such as one or a combination of two or more of ammonium sulfate, potassium persulfate, sodium persulfate, or azobisisobutyramidine hydrochloride.

[0044] An embodiment of the second aspect of the present invention provides a preparation method of an anti-swelling agent.

[0045] Example 1

[0046] As Figure 1 shown, the preparation method of the anti-swelling agent provided in this embodiment includes the following steps:

[0047] S102: Configure the preparation raw materials of the anti-swelling agent; wherein, the preparation raw materials include dimethyldiallylammonium chloride, the auxiliary agent disodium ethylenediaminetetraacetate, the initiator ammonium persulfate, and water. The proportion of dimethyldiallylammonium chloride is 52%, the proportion of the auxiliary agent disodium ethylenediaminetetraacetate is 0.10%, the proportion of the initiator ammonium persulfate is 1.2%, and the rest is water;

[0048] S104: Start the reaction tank, and sequentially add the measured water and dimethyldiallylammonium chloride into the reaction tank. After adding, start timing and stir for 10 min;

[0049] S106: Heat the reaction tank to 70 °C, continuously stir during this period, control the pressure during the reaction to be less than or equal to 0.25 MPa, add the initiator ammonium persulfate, and the amount of water used for the initiator is 9 mL;

[0050] S108: Continue to add the auxiliary agent disodium ethylenediaminetetraacetate, add it all within 15 minutes, and react at 70 °C for 6 hours. After the reaction is completed, when the sample cools to room temperature, release 10 kg of the material from the discharge port, and check whether the material is evenly mixed and whether there is layering. If the material is not evenly stirred and there is agglomeration, return it to the reaction tank from the feeding point and continue to stir and react until the material is evenly stirred to obtain the swelling inhibitor.

[0051] Next, conduct the swelling inhibition rate and water washing resistance experiments on the swelling inhibitor for fracturing prepared in Example 1.

[0052] Conduct a comparison test on the swelling inhibitor for fracturing prepared above with two common swelling inhibitors on the market.

[0053] First, prepare an aqueous solution with the required concentration for the experiment, and then sequentially measure the swelling inhibition rate and water washing resistance of the sample according to the centrifugation method in SY / T5971 - 2016 standard. The experimental results are shown in Table 1 below:

[0054]

[0055]

[0056] Table 1

[0057] It can be seen from Table 1 that the swelling inhibitor prepared by the preparation method of the present invention has a higher swelling inhibition rate and stronger water washing resistance than the swelling inhibitors of Market 1 and Market 2 at the same test concentration.

[0058] Conduct a temperature resistance experiment on the swelling inhibitor for fracturing prepared by the preparation method of Example 1.

[0059] Specifically, prepare an aqueous solution with the required concentration for the above swelling inhibitor, measure 200 mL of the aqueous solution and put it into a 250 mL temperature-resistant and pressure-resistant container (the range of the temperature-resistant and pressure-resistant container is 250 mL, meeting the requirements of 21.5.3 in GB / T29170 - 2012), lock the threaded seal, place the container in a constant temperature drying oven that has been heated to 95 °C, take it out after 6 hours of constant temperature, cool it to room temperature, open the cooled temperature-resistant and pressure-resistant container, measure 10 mL of the solution to be tested, and measure the swelling inhibition rate of the sample according to the centrifugation method in SY / T5971 - 2016. The results are shown in Table 2.

[0060] Anti-swelling agent test concentration Anti-swelling rate results at room temperature (%) Anti-swelling rate results after 95°C / 6h (%) Difference (%) 0.5％ 87.58 86.92 0.66 0.6％ 91.42 91.23 0.19 0.7％ 93.68 93.54 0.14

[0061] Table 2

[0062] As can be seen from Table 2, the swelling inhibitor prepared by the present invention has good temperature resistance. Even when kept at a high temperature of 95 °C for 6 hours, its swelling prevention rate basically remains unchanged, which is fully applicable to the oilfield exploitation of low-permeability tight reservoirs and shale oil reservoirs.

[0063] Next, a compatibility experiment was carried out on the swelling inhibitor for fracturing prepared in Example 1 and plant gum fracturing fluid or polymer fracturing fluid. The viscosity values of the fracturing fluid before and after adding the sample were measured, and the viscosity retention rate was calculated.

[0064] Compatibility of the swelling inhibitor with plant gum fracturing fluid: Add 500 mL of test water to a stirrer, turn on the stirrer, and adjust the stirrer speed until the vortex formed by the liquid can see the top of the central axis of the stirrer blade. Slowly add the additives used in the field application. According to this step, prepare 2 portions of the base fluid. One portion is added with 3.50 mL of the swelling inhibitor sample of this application, and the other portion is a blank control sample. Stir for 5 minutes, place the two stirrers in wide-mouth bottles respectively, and let them stand for 2 hours at 25 °C and 90 °C in sequence. Compare the apparent viscosities of the solutions of the blank control sample and the test sample after adding the swelling inhibitor of the present invention, and calculate the viscosity retention rate. The test method is carried out in accordance with SY / T5672-2021, and the results are shown in Table 3 below.

[0065] Compatibility of the swelling inhibitor with polymer fracturing fluid: Add 500 mL of test water to a stirrer, turn on the stirrer, and prepare 2 portions of polymer fracturing fluid according to the operation method of 6.7.1.1. Slowly add various additives required by the formula. One portion is added with 3.50 mL of the swelling inhibitor sample of this application, and the other portion is a blank control sample. Stir for 5 minutes, place the two stirrers in wide-mouth bottles respectively, and let them stand for 2 hours at 25 °C and 90 °C in sequence. Compare the apparent viscosities of the solutions of the blank control sample and the test sample after adding the swelling inhibitor of the present invention, and calculate the retention rate. The test method is carried out in accordance with SY / T5672-2021, and the results are shown in Table 3 below.

[0066] Anti-swelling agent test concentration Viscosity retention rate of plant gum (%) Viscosity retention rate of polymer (%) 0.5％ 87.74 87.88 0.6％ 89.73 90.06 0.7％ 90.70 90.73

[0067] Table 3

[0068] As can be seen from Table 3, the swelling inhibitor prepared by the present invention has good compatibility with plant gum fracturing fluid or polymer fracturing fluid. For the swelling inhibitor of Market No. 1, under the same test concentration of 0.5% and the same test conditions, when it is compatible with plant gum fracturing fluid, the viscosity retention rate of plant gum is only about 80%, and when it is compatible with polymer fracturing fluid, the viscosity retention rate of polymer is only about 85%. It can be seen that the swelling inhibitor prepared by the present invention has more excellent compatibility compared with the swelling inhibitor of Market No. 1.

[0069] Next, a compatibility experiment was carried out on the swelling inhibitor for fracturing prepared in this Example 1 and formation water.

[0070] Specifically, the swelling inhibitor for fracturing prepared as above is formulated into an aqueous solution with a concentration of 0.5%, and then mixed with formation water according to a weight ratio of 1:1, and kept at 25°C and 90°C for 0.5 hours to 4 hours respectively. The results are shown in Table 4.

[0071]

[0072] Table 4

[0073] As can be seen from Table 4, the swelling inhibitor prepared by the present invention has good compatibility with water. Whether at 25°C or 90°C, after mixing for 4.0 h, the solution can be clear and transparent. For the swelling inhibitor of Market No. 1, after mixing with water for 4.0 h, the solution shows a turbid state.

[0074] Example 2

[0075] The preparation method of the swelling inhibitor provided in this example is the same as that of the swelling inhibitor provided in Example 1, and the difference is only in the components of the raw materials for preparation. The difference is that in this example, the proportion of dimethyldiallylammonium chloride is 55%, the proportion of the auxiliary agent ethylenediaminetetraacetic acid disodium is 0.12%, the proportion of the initiator ammonium persulfate is 1.4%, and the balance is water.

[0076] Example 3

[0077] The preparation method of the swelling inhibitor provided in this example is the same as that of the swelling inhibitor provided in Example 1, and the difference is only in the components of the raw materials for preparation. The difference is that in this example, the proportion of dimethyldiallylammonium chloride is 50%, the proportion of the auxiliary agent ethylenediaminetetraacetic acid disodium is 0.08%, the proportion of the initiator ammonium persulfate is 1.0%, and the balance is water.

[0078] Comparative Example 1

[0079] The preparation method of the swelling inhibitor provided in this comparative example is the same as that of the swelling inhibitor provided in Example 1, and the difference is only in the components of the raw materials for preparation. The difference is that in this comparative example, the proportion of dimethyldiallylammonium chloride is 52%, the proportion of the auxiliary agent ethylenediaminetetraacetic acid disodium is 0.3%, the proportion of the initiator ammonium persulfate is 1.2%, and the balance is water.

[0080] Comparative Example 2

[0081] The preparation method of the swelling inhibitor provided in this comparative example is the same as that of the swelling inhibitor provided in Example 1, and the difference is only in the components of the raw materials for preparation. The difference is that in this comparative example, the proportion of dimethyldiallylammonium chloride is 52%, the proportion of the auxiliary agent ethylenediaminetetraacetic acid disodium is 0.05%, the proportion of the initiator ammonium persulfate is 1.2%, and the balance is water.

[0082] Comparative Example III

[0083] The preparation method of the anti-swelling agent provided in this comparative example is the same as the preparation method of the anti-swelling agent provided in Example 1, and the difference is only in the components of the raw materials for preparation. The difference lies in that in this comparative example, the proportion of dimethyldiallylammonium chloride is 52%, the proportion of the auxiliary agent disodium ethylenediaminetetraacetate is 0.1%, the proportion of the initiator ammonium persulfate is 2%, and the balance is water.

[0084] Comparative Example IV

[0085] The preparation method of the anti-swelling agent provided in this comparative example is the same as the preparation method of the anti-swelling agent provided in Example 1, and the difference is only in the components of the raw materials for preparation. The difference lies in that in this comparative example, the proportion of dimethyldiallylammonium chloride is 52%, the proportion of the auxiliary agent disodium ethylenediaminetetraacetate is 0.1%, the proportion of the initiator ammonium persulfate is 0.5%, and the balance is water.

[0086] Comparative Example V

[0087] The preparation method of the anti-swelling agent provided in this comparative example is the same as the preparation method of the anti-swelling agent provided in Example 1, and the difference is only in the components of the raw materials for preparation. The difference lies in that in this comparative example, the proportion of dimethyldiallylammonium chloride is 52%, the proportion of the auxiliary agent tetrasodium ethylenediaminetetraacetate is 0.10%, the proportion of the initiator ammonium persulfate is 1.2%, and the balance is water.

[0088] Comparative Example VI

[0089] The preparation method of the anti-swelling agent provided in this comparative example is the same as the preparation method of the anti-swelling agent provided in Example 1, and the difference is only in the components of the raw materials for preparation. The difference lies in that in this comparative example, the proportion of dimethyldiallylammonium chloride is 52%, the proportion of the auxiliary agent disodium ethylenediaminetetraacetate is 0.10%, the proportion of the initiator sodium persulfate is 1.5%, and the balance is water.

[0090] Select conventional ammonium persulfate as the initiator (the ratio of dimethyldiallylammonium chloride, auxiliary agent, initiator and water is the same as that in Example 1).

[0091] The anti-swelling agents prepared by the methods of Examples 1 to 3 and Comparative Examples 1 to 6 of the present invention were successively subjected to anti-swelling rate and water washing resistance experiments, temperature resistance experiments, and compatibility experiments. Among them, the test conditions are the same as the test conditions stated above and will not be elaborated here. The test concentration of the anti-swelling agent is 0.5%. The experimental results are shown in Table 5 below:

[0092]

[0093] Table 5

[0094] Example VI

[0095] As Figure 2 shown, the preparation method of the anti-swelling agent provided in this embodiment includes the following steps:

[0096] S202: Add dimethyldiallylammonium chloride, additives, initiator and water into the reaction kettle to cause the polymerization reaction of dimethyldiallylammonium chloride to generate an anti-swelling agent in the reaction kettle; wherein, the reaction pressure in the reaction kettle is less than or equal to 0.25 MPa, and the reaction temperature is greater than or equal to 60 °C.

[0097] The anti-swelling agent prepared by the preparation method of the anti-swelling agent provided by the present invention is a cationic polymer with dimethyldiallylammonium chloride as the main body. It has good water solubility, the aqueous solution is neutral, and after ionization in the aqueous solution, it generates positively charged quaternary ammonium salt linear functional groups. In addition to the bridging and sweeping functions of general viscosifiers, it also has a relatively strong electro-neutralization ability, has the function of protecting the reservoir, has good anti-swelling performance, low use concentration, small adsorption damage to the formation, long anti-swelling period, good water washing resistance, can extend the water injection cycle, can achieve good effects of increasing oil production in oil wells and increasing water injection in water wells, has good temperature and salt resistance, low price and simple process, and is especially suitable for the exploitation of low-permeability tight reservoirs and shale oil reservoirs.

[0098] In some embodiments, optionally, the preparation steps of dimethyldiallylammonium chloride are as follows: Drop allyl chloride into the first mixed solution including dimethylamine, basic resin and phase transfer catalyst to obtain a second mixed solution; Heat the second mixed solution to greater than or equal to 40 °C and reflux for 3 to 8 hours. When the pH value of the second mixed solution is greater than 7, carry out vacuum distillation on the second mixed solution in sequence to obtain dimethyldiallylammonium chloride.

[0099] In this embodiment, the preparation method of dimethyldiallylammonium chloride is: Drop allyl chloride into the solution containing 33% dimethylamine, strongly basic resin and phase transfer catalyst at a temperature of 15 °C to 20 °C; After the dropwise addition of allyl chloride is completed, raise the temperature of the mixed solution to greater than or equal to 40 °C, for example, about 50 °C, and reflux for 3 to 8 hours. When the pH value is greater than 7, for example, when the pH is about 8, stop the reaction, and then obtain dimethyldiallylammonium chloride through vacuum distillation.

[0100] In some embodiments, optionally, the basic resin includes basic styrene anion exchange resin.

[0101] In this embodiment, using basic styrene anion exchange resin can improve the production efficiency of dimethyldiallylammonium chloride.

[0102] In some embodiments, optionally, the phase transfer catalyst includes at least one of tetraethylammonium bromide or tetraethylammonium chloride.

[0103] In this embodiment, using tetraethylammonium bromide and / or tetraethylammonium chloride as the phase transfer catalyst can improve the production efficiency of dimethyldiallylammonium chloride.

[0104] In some embodiments, optionally, the mass ratio of dimethylamine to allyl chloride is greater than or equal to 1:1.4 and less than or equal to 1:1.

[0105] In this embodiment, the mass ratio of dimethylamine to allyl chloride is greater than or equal to 1:1.4 and less than or equal to 1:1. For example, the mass ratio of dimethylamine to allyl chloride is equal to 1:1.2. This can avoid material waste and improve the production efficiency of dimethyldiallylammonium chloride.

[0106] In some embodiments, optionally, the auxiliary agent includes disodium ethylenediaminetetraacetate. The preparation steps of disodium ethylenediaminetetraacetate are as follows: Mix chloroacetic acid, ice and sodium hydroxide to obtain a third mixed solution, stir the third mixed solution and add ethylenediamine to the third mixed solution to generate disodium ethylenediaminetetraacetate.

[0107] In this embodiment, disodium ethylenediaminetetraacetate is prepared by the chloroacetic acid method. Specifically, first mix 100 kg of chloroacetic acid, 100 kg of ice and 135 kg of 30% sodium hydroxide solution (mass percentage), add 18 kg of 83% - 84% ethylenediamine (mass percentage) under stirring, keep it warm at 15 °C for 1 h, then slowly add the 30% sodium hydroxide solution in batches until the reactant shows alkalinity, and keep it at room temperature for 12 h, then heat to 90 °C, add activated carbon for decolorization, filter, adjust the pH value of the filtrate to 4.5 with hydrochloric acid, concentrate and filter at 90 °C, cool the filtrate to crystallize, separate and wash, and dry at 70 °C to obtain disodium ethylenediaminetetraacetate.

[0108] Example Seven

[0109] The preparation method of the anti-swelling agent provided in this embodiment.

[0110] Specifically, after the operator starts the reaction tank, the metered water and dimethyldiallylammonium chloride with a raw material concentration of 50% to 55% are sequentially added into the reaction tank. After adding, stir for 10 minutes and time the stirring. Heat the reaction tank to 70°C, and continue stirring during this period. Control the pressure during the reaction to be less than or equal to 0.25 MPa. Add ammonium persulfate as the initiator, and the dosage of ammonium persulfate is 1.0% to 1.4%. The amount of water used for the initiator is 7 ml to 10 ml. Then continue to add disodium ethylenediaminetetraacetate as the auxiliary agent, and the dosage of disodium ethylenediaminetetraacetate is 0.08% to 0.12%. Add it all within 15 minutes. React at 70°C for 6 hours. After the reaction is completed and the sample is cooled to room temperature, about 10 kg of the material is discharged from the discharge port to check whether the material is evenly mixed and whether there is layering. If the material is not evenly stirred and there is agglomeration, return it to the reaction tank from the feeding point and continue to stir and react until the material is evenly stirred. If the material is evenly mixed, then start discharging and transfer it to the material transfer point.

[0111] In the third aspect of the embodiments of the present invention, an application of an anti-swelling agent is provided. The anti-swelling agent is the anti-swelling agent provided in any one of the embodiments of the first aspect of the present invention, or the anti-swelling agent is prepared by the preparation method of the anti-swelling agent provided in any one of the embodiments of the second aspect of the present invention.

[0112] In addition, optionally, the present invention also provides a method for determining the content of the anti-swelling agent. The anti-swelling agent is the anti-swelling agent provided in any one of the embodiments of the first aspect of the present invention or the anti-swelling agent prepared by the preparation method of the anti-swelling agent provided in any one of the embodiments of the second aspect of the present invention. The method for determining the content of the anti-swelling agent includes: determining the shale content of the formation; and determining the content of the anti-swelling agent required for the formation according to the shale content of the formation and the corresponding relationship between the shale content and the anti-swelling agent content.

[0113] The present invention can determine the recommended use concentration of the anti-swelling agent for formations with different shale contents according to the shale content of the formation, solving the problem that the dosage of the anti-swelling agent used in previous fracturing is not strongly targeted to the formation characteristics. When determining the shale content of the formation, the shale content of the formation can be calculated according to the results of radioactive logging data, and the calculation steps are as follows:

[0114] Calculate the shale content V of the rock using the natural gamma ray curve sh profile, and calculate it using the following formula:

[0115] SH = (GR - GR min ) / (GR max - GR min ) (1)

[0116] V sh = 2 GCUR·SH-1 / 2 GCUR-1 (2)

[0117] Wherein, SH is the relative value of natural gamma, dimensionless; GR is the natural gamma value of the target layer, dimensionless; GR min is the natural gamma value of the pure shale formation, dimensionless; GR max is the natural gamma value of the pure lithologic formation, dimensionless; V sh is the shale content, in decimals; GCUR is the experience coefficient related to the age, taking 3.7 for old formations and 2 for new formations.

[0118] According to the calculation results of logging data:

[0119] For formations with a shale content below 10%, the recommended concentration of the swelling inhibitor is 0.2% to 0.4%;

[0120] For formations with a shale content of 10% to 20%, the recommended concentration of the swelling inhibitor is 0.5% to 0.6%;

[0121] For formations with a shale content of 20% to 30%, the recommended concentration of the swelling inhibitor is 0.7% to 0.8%;

[0122] For formations with a shale content of 30% to 40%, the recommended concentration of the swelling inhibitor is 0.9% to 1.0%;

[0123] For formations with a shale content above 40%, the recommended concentration of the swelling inhibitor is 1.1% to 1.2%.

[0124] Prepare the fracturing fluid according to the recommended ratio and conduct subsequent fracturing operations.

[0125] When the swelling inhibitor for fracturing in the present invention is applied in fracturing of low-permeability tight and shale oil reservoirs, the use concentration of the swelling inhibitor (ranging from 0.2% to 1.2%) can be determined according to the different shale contents of the formations. The swelling inhibitor can be directly added to the fracturing fluid for individual use, or the swelling inhibitor can be compounded with potassium chloride as an intermediate to achieve the best on-site application effect.

[0126] The following details the application of the swelling inhibitor of the present invention in oil extraction.

[0127] Application Example 1

[0128] Basic situation of Fracturing Well 1: Completion time is March 2023, total depth of the completed well is 3381m, maximum well deviation is 24.25°, surface casing steel grade is J55, outer diameter is 244.5mm, setting depth is 806m, production casing steel grade is P110, outer diameter is 139.7mm, setting depth is 3372m. The fracturing target layer is from 3215.7m to 3239.2m, the designed fracturing fluid volume is 540m 3 , sand volume is 41.2m 3 , construction displacement is 4m 3 / min to 4.5m3 / min.

[0129] Preparation of swelling inhibitor for fracturing: After the operator starts the reaction tank, the metered water and 52% dimethyldiallylammonium chloride as raw materials are added into the reaction tank in sequence. After adding, start timing and stir for 10 min. The temperature of the reaction tank rises to 70 °C, and continuous stirring is maintained during this period. The pressure during the reaction process is controlled to be less than or equal to 0.25 MPa. Add ammonium persulfate as the initiator, with a dosage of 1.0%, and then continue to add disodium ethylenediaminetetraacetate as the auxiliary agent, with a dosage of 0.12%. Add it all within 15 min. The reaction time at 70 °C is 6 h. After the reaction is completed, wait for the sample to cool to room temperature, then discharge about 10 kg of materials from the discharge port, and check whether the materials are evenly mixed and whether there is layering. If the materials are not evenly stirred and there is agglomeration, return them to the reaction tank from the feeding point and continue to stir and react until the materials are evenly stirred. If the materials are evenly mixed, then start discharging and transfer them to the material transfer point.

[0130] The mineral components of the experimental block are mainly illite and chlorite, the content of kaolinite is relatively low, the permeability is mainly concentrated in the range of 0.02 mD to 0.14 mD, the porosity of mixed shale is mainly in the range of 0.94% to 1.94%, mainly fine sandstone. According to the radioactive logging data, the shale content is calculated to be 14.3%, between 10% and 20%, and the addition concentration of the swelling inhibitor is determined to be 0.5%.

[0131] Prepare the fracturing fluid in proportion for subsequent fracturing construction. The fracturing fluid adopts a low-damage fracturing fluid system, with a construction displacement of 4 m 3 / min to 4.5 m 3 / min, the construction pressure is 50.0 MPa, the injected fracturing fluid volume is 540 m 3 , the sand volume is 41.2 m 3 , and the dosage of the swelling inhibitor is 2700 kg.

[0132] Implementation effect: Before fracturing, the oil casing is unobstructed and there is no oil and gas display. After fracturing, the pump is discharged, with a daily oil production of 4.5 t and a daily water production of 5.68 m 3 .

[0133] Application Example 2

[0134] Basic situation of Well 2 for fracturing: The completion time is May 2022, the total depth of the drilled well is 3780 m, the maximum well deviation is 84.1°, the surface casing steel grade is J55, the outer diameter is 339.7 mm, the wall thickness is 9.65 mm, and the setting depth is 411 m. The technical casing steel grade is N80, the outer diameter is 244.5 mm, the wall thickness is 10.03 mm, and the setting depth is 2499 m. The production casing steel grade is TP125V, the outer diameter is 139.7 mm, the wall thickness is 12.7 mm, and the setting depth is 3774 m. The fracturing target interval is from 3208.5 m to 3751 m. The fracturing target interval has a total of 9 segments and 66 clusters. The designed fracturing fluid volume is 18688 m 3, sand volume: 1702 m 3 , construction displacement: 14 m 3 / min to 16 m 3 / min.

[0135] Preparation of swelling inhibitor for fracturing: After the operator starts the reaction tank, the measured water and 60% of dimethyldiallylammonium chloride as raw materials are added into the reaction tank in sequence. After adding, start timing and stir for 10 min. The temperature of the reaction tank rises to 70 °C, and continuous stirring is maintained during this period. The pressure during the reaction process is controlled to be less than or equal to 0.25 MPa. Add ammonium persulfate as the initiator, and the dosage of ammonium persulfate is 1.0%. Then continue to add ethylenediaminetetraacetic acid disodium as the auxiliary agent, with a dosage of 0.12%, and finish adding within 15 min. The reaction time at 70 °C is 6 h. After the reaction is completed, when the sample cools to room temperature, about 10 kg of the material is discharged from the discharge port, and check whether the material is evenly mixed and whether there is layering. If the material is not evenly stirred and there is agglomeration, return it to the reaction tank from the feeding point and continue to stir and react until the material is evenly stirred. If the material is evenly mixed, start discharging and transfer it to the material transfer point.

[0136] The permeability mainly concentrates in the range of 0.02 mD to 0.6 mD, and the porosity of felsic shale is mainly in the range of 0.57% to 5.1%. According to the radioactive logging data, the shale content is calculated to be 21.8%, which is between 20% and 30%, and the addition concentration of the swelling inhibitor is determined to be 0.7%.

[0137] Prepare the fracturing fluid in proportion for subsequent fracturing construction. The fracturing fluid uses a low-damage fracturing fluid system, with a construction displacement of 14 m 3 / min to 16 m 3 / min, construction pressure: 60.5 MPa, injected fracturing fluid volume: 18688 m 3 , sand volume: 1702 m 3 , dosage of swelling inhibitor: 130816 kg.

[0138] Implementation effect: After fracturing, it produces by natural flow with a 2-mm choke, with a daily oil production of 25.8 t and a daily water production of 12.2 m 3 .

[0139] Application Example 3

[0140] Basic information of the fractured well 3: Completion time was in January 2022, total depth of the completed well was 5395 m, maximum well deviation was 80.5°, surface casing steel grade was J55, outer diameter was 339.7 mm, wall thickness was 9.65 mm, setting depth was 600 m, technical casing steel grade was N80, outer diameter was 244.5 mm, wall thickness was 10.05 mm, setting depth was 2899 m, production casing steel grade was BG125SG, outer diameter was 139.7 mm, wall thickness was 12.7 mm, setting depth was 5388 m, fractured target zone was from 4035 m to 5353 m, there were 23 stages and 172 clusters in the fractured target zone, designed fracturing fluid volume was 32327 m 3 , sand volume was 2300 m 3 , construction displacement was 14 m 3 / min to 16 m 3 / min.

[0141] Preparation of swelling inhibitor for fracturing: After the operator starts the reaction tank, the measured water and 50% dimethyldiallylammonium chloride as raw materials are added into the reaction tank in sequence. After adding, start timing and stir for 10 min. The temperature of the reaction tank rises to 70 °C, and continuous stirring is maintained during this period. The pressure during the reaction process is controlled to be less than or equal to 0.25 MPa. Add ammonium persulfate as the initiator, with a dosage of 0.8%, and continue to add disodium ethylenediaminetetraacetate as the auxiliary agent, with a dosage of 0.10%. Finish adding within 15 min. The reaction time at 70 °C is 6 h. After the reaction is completed, when the sample cools to room temperature, add 5% potassium chloride, start timing and stir for 30 minutes, then stop stirring. Release about 10 kg of material from the discharge port, and check whether the material is evenly mixed and whether there is layering. If the material is not evenly stirred and there are agglomerates, return it to the reaction tank from the feeding point and continue to stir and react until the material is evenly stirred. If the material is evenly mixed, then start discharging and transfer it to the material transfer point.

[0142] The permeability mainly concentrates in the range of 0.17 mD to 0.34 mD, and the porosity of the shale mainly ranges from 0.94% to 1.94%. According to the radioactive logging data, the shale content is calculated to be 28.6%, which is between 20% and 30%. Determine the swelling inhibitor addition concentration to be 0.7%.

[0143] Prepare fracturing fluid in proportion for subsequent fracturing construction. The fracturing fluid adopts a slickwater fracturing fluid system. The construction displacement is 14 m 3 / min to 16 m 3 / min, the construction pressure is 62.0 MPa, the injected fracturing fluid volume is 32327 m 3 , the sand volume is 2300 m 3 , and the dosage of swelling inhibitor is 226289 kg.

[0144] Implementation effect: After fracturing, it flows by itself with a 2 mm choke, with a daily oil production of 23.75 t and a daily water production of 11.25 m 3 .

[0145] Application Example 4

[0146] Basic conditions of the fracturing well 4: Completion time was in May 2022, total depth of the drilled well was 4257 m, maximum well deviation was 78.5°, surface casing steel grade was J55, outer diameter was 339.7 mm, wall thickness was 9.65 mm, setting depth was 600 m, technical casing steel grade was N80, outer diameter was 244.5 mm, wall thickness was 10.05 mm, setting depth was 3765 m, production casing steel grade was BG125SG, outer diameter was 139.7 mm, wall thickness was 12.7 mm, setting depth was 4200 m, fracturing target interval was from 3847.9 m to 3877.0 m, a total of 555 m 3 of ceramsite was 39.6 m 3 , and the fracture pressure gradient was 0.022 mPa / m.

[0147] Preparation of swelling inhibitor for fracturing: After the operator started the reaction tank, the measured water and 55% dimethyldiallylammonium chloride as raw materials were successively added into the reaction tank. After adding, timing and stirring were carried out for 10 min, and the temperature of the reaction tank was raised to 70 °C. During this period, continuous stirring was maintained, and the pressure during the reaction process was controlled to be less than or equal to 0.25 MPa. Ammonium persulfate as an initiator was added, and the dosage was 1.0%. Ethylenediaminetetraacetic acid disodium as an auxiliary agent was continuously added, and the dosage was 0.10%. It was added within 15 min, and the reaction time at 70 °C was 6 h. After the reaction was completed, when the sample cooled to room temperature, about 10 kg of the material was discharged from the discharge port to check whether the material was evenly mixed and whether there was layering. If the material was not evenly stirred and there was agglomeration, it was returned to the reaction tank from the feeding point and continued to be stirred and reacted until the material was evenly stirred. If the material was evenly mixed, then discharging started and it was transported to the material transfer point.

[0148] The permeability mainly concentrated in the range of 0.96 mD to 1.54 mD, and the porosity of the shale mainly ranged from 0.94% to 1.94%. According to the radioactive logging data, the shale content was calculated to be 32.4%, which was between 30% and 40%. The addition concentration of the swelling inhibitor was determined to be 0.9%.

[0149] The fracturing fluid was proportionally prepared for subsequent fracturing construction. The fracturing fluid adopted a slickwater fracturing fluid system, with a construction displacement of 5.5 to 6.5 m 3 / min, construction pressure of 56.0 MPa, injection volume of fracturing fluid of 555 m3, ceramsite of 39.6 m 3 , and the dosage of the swelling inhibitor was 4995 kg.

[0150] Implementation effect: The daily production before fracturing was 0.16 t, the pump pressure after fracturing was 25 MPa, the daily oil production was 5.53 tons, and the cumulative oil production in 14 days was 28.28 tons.

[0151] In addition, optionally, the present invention further provides a device for determining the content of the anti-swelling agent, including: a memory and a processor, where the memory stores a program, and when the processor executes the program, it implements the steps of the method for determining the content of the anti-swelling agent provided in the fourth aspect of the present invention.

[0152] In addition, optionally, the present invention further provides a device for determining the content of the anti-swelling agent, including: a determination module for determining the shale content of the formation; the determination module is further configured to determine the content of the anti-swelling agent required for the formation according to the shale content and the corresponding relationship between the shale content and the anti-swelling agent content.

[0153] Beneficial effects: The present invention provides an anti-swelling agent formulation for fracturing, as well as a preparation and use method. This anti-swelling agent can effectively prevent the swelling of shale and muddy shale, has a low use concentration, causes little adsorption damage to the formation, and has a long anti-swelling period. The composition of this anti-swelling agent is simple, the proportion of additives is small, the main agent is degradable, and it does not contain any flammable or volatile substances. It can be applied to the fracturing of low-permeability tight and shale oil reservoirs, can improve the fracturing treatment effect, is suitable for use in large-scale volume fracturing fluids in oil and gas fields. In addition, it can formulate personalized use methods for formations with different shale contents, has good compatibility with existing fracturing fluids, achieves an efficient anti-swelling effect, and solves the problems in the prior art such as the unclear dosage of the anti-swelling agent and the lack of formation specificity.

[0154] Although this specification contains many specific implementation details, these should not be construed as limiting the scope of any invention or the scope of what is claimed, but are mainly used to describe the features of specific embodiments of a particular invention. Certain features described in multiple embodiments in this specification can also be implemented in combination in a single embodiment. On the other hand, the various features described in a single embodiment can also be implemented separately in multiple embodiments or in any suitable sub-combination. In addition, although features may function in certain combinations as described above and are even initially claimed as such, one or more features from the claimed combination can in some cases be removed from the combination, and the claimed combination can be directed to a sub-combination or a variant of the sub-combination.

[0155] Similarly, although the operations are depicted in a specific order in the drawings, this should not be construed as requiring these operations to be performed in the specific order shown or sequentially, or requiring all illustrated operations to be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. In addition, the separation of the various system modules and components in the above embodiments should not be construed as required in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

[0156] Accordingly, specific embodiments of the subject matter have been described. Other embodiments are within the scope of the appended claims. In some cases, the acts recited in the claims can be performed in a different order and still achieve the desired result. In addition, the processes depicted in the figures are not necessarily in the particular order or sequential order shown to achieve the desired result. In some implementations, multitasking and parallel processing may be advantageous.

[0157] It should be noted that in this document, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0158] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. An anti-swelling agent, characterized in that, The raw materials for preparing the anti-swelling agent include dimethyldiallylammonium chloride, auxiliary agent, initiator and water.

2. The anti-swelling agent according to claim 1, characterized in that, The mass percentage of the dimethyldiallylammonium chloride in the raw materials for preparation is greater than or equal to 50% and less than or equal to 55%. The mass percentage of the auxiliary agent in the raw materials for preparation is greater than or equal to 0.08% and less than or equal to 0.12%. The mass percentage of the initiator in the raw materials for preparation is greater than or equal to 1% and less than or equal to 1.4%.

3. The anti-swelling agent according to claim 1, characterized in that, The dimethyldiallylammonium chloride is prepared from dimethylamine and allyl chloride.

4. The anti-swelling agent according to claim 1, characterized in that, The auxiliary agent includes disodium ethylenediaminetetraacetate.

5. The anti-swelling agent according to claim 4, characterized in that, The disodium ethylenediaminetetraacetate is prepared from chloroacetic acid, ethylenediamine, ice, sodium hydroxide and hydrochloric acid.

6. The anti-swelling agent according to claim 1, characterized in that, The initiator includes ammonium persulfate.

7. A preparation method of an anti-swelling agent, characterized in that, It includes the following steps: Add dimethyldiallylammonium chloride, auxiliary agent, initiator and water into a reaction kettle to make the dimethyldiallylammonium chloride undergo a polymerization reaction to generate the anti-swelling agent in the reaction kettle. Among them, the reaction pressure in the reaction kettle is less than or equal to 0.25 MPa, and the reaction temperature is greater than or equal to 60 °C.

8. The preparation method of the anti-swelling agent according to claim 7, characterized in that, The preparation steps of the dimethyldiallylammonium chloride are as follows: Drop allyl chloride into a first mixed solution including dimethylamine, basic resin and phase transfer catalyst to obtain a second mixed solution. Heat the second mixed solution to be greater than or equal to 40 °C and reflux it on a reflux device for 3 to 8 hours. When the pH value of the second mixed solution is greater than 7, carry out decompression and distillation on the second mixed solution in sequence to obtain the dimethyldiallylammonium chloride.

9. The preparation method of the anti-swelling agent according to claim 8, characterized in that, The basic resin includes basic styrene anion exchange resin; and / or The phase transfer catalyst includes at least one of tetraethylammonium bromide or tetraethylammonium chloride.

10. The preparation method of the anti-swelling agent according to claim 8, characterized in that, The mass ratio of the dimethylamine to the allyl chloride is greater than or equal to 1:1.4 and less than or equal to 1:

1.

11. The preparation method of the anti-swelling agent according to claim 7, characterized in that, The auxiliary agent includes disodium ethylenediaminetetraacetate, and the preparation steps of the disodium ethylenediaminetetraacetate are as follows: (HOOCCH2)2NCH2CH2N(CH2COOH)2 + 2NaOH → (NaOOCCH2)2NCH2CH2N(CH2COOH)2·2H2O Mix chloroacetic acid, ice and sodium hydroxide to obtain a third mixed solution, stir the third mixed solution and add ethylenediamine to the third mixed solution to generate the disodium ethylenediaminetetraacetate.

12. Application of the anti-swelling agent prepared by the preparation method of the anti-swelling agent according to any one of claims 1 to 6 or any one of claims 7 to 11 in fracturing.

Images