A kind of oligomeric cationic quaternary ammonium salt clay stabilizer and preparation method thereof

Abstract

The present application relates to the technical field of clay stabilizers, and in particular to a kind of oligomeric cationic quaternary ammonium salt clay stabilizer and its preparation method. The preparation method of the oligomeric cationic quaternary ammonium salt clay stabilizer of the present application comprises the following steps: N-methylaniline and epichlorohydrin react under a first reaction condition to generate a target monomer; the target monomer undergoes a self-polymerization reaction under a second reaction condition to generate a target polymer; the target polymer undergoes a hydrolysis reaction to generate a crude product; the crude product is subjected to an impurity removal treatment to obtain an oligomeric cationic quaternary ammonium salt clay stabilizer. The anti-swelling performance and water washing resistance of the oligomeric cationic quaternary ammonium salt clay stabilizer of the present application are significantly improved, and the preparation mechanism is clear, the reaction conditions are simple, and the post-processing operation is simple, and it is easy to scale up production.

Description

Technical Field

[0001] The invention belongs to the technical field of clay stabilizers, and particularly relates to an oligomeric cationic quaternary ammonium salt clay stabilizer and a preparation method thereof. Background Art

[0002] During oilfield waterflooding, clay minerals in the formation hydrate and expand, blocking formation pores and severely reducing reservoir permeability. This is primarily due to the fact that clay minerals, primarily composed of montmorillonite and kaolin, carry a significant amount of negative charge. Upon hydration, the repulsive forces between these negative charges cause the clay minerals to rapidly expand, blocking reservoir pores and hindering oil and gas production.

[0003] Currently, the primary clay anti-swelling measure used in oil recovery is to inject clay stabilizers into clay minerals to reduce their swelling when exposed to water. Common clay stabilizers include potassium chloride and small-molecule quaternary ammonium salts. The potassium ions in potassium chloride have a small atomic radius and can penetrate the interior of clay minerals, forming a double electron layer and thus reducing clay mineral swelling. Small-molecule quaternary ammonium salts, on the other hand, neutralize charges, reducing negative charge density and thus reducing clay swelling.

[0004] The advantage of the above conventional clay stabilizers is a high anti-swelling rate. The disadvantage is that during the process of water injection into the formation, inorganic salts and small molecular quaternary ammonium salts are easily washed away, causing their concentration to drop rapidly, resulting in poor resistance to water washing and poor anti-swelling stability. Summary of the Invention

[0005] The purpose of this application is to provide an oligomeric cationic quaternary ammonium salt clay stabilizer and a preparation method thereof to address the shortcomings of conventional clay stabilizers such as poor anti-swelling effect and poor water resistance. The embodiments of this application are achieved as follows:

[0006] The first aspect of the embodiments of the present application provides an oligomeric cationic quaternary ammonium salt clay stabilizer having the following structural formula:

[0007]

[0008] Among them, n=3-10.

[0009] A second aspect of the embodiments of the present application provides a method for preparing an oligomeric cationic quaternary ammonium salt clay stabilizer, the preparation method comprising the following steps:

[0010] N-methylaniline and epichlorohydrin are reacted under first reaction conditions to generate a target monomer, wherein the molar ratio of the N-methylaniline to the epichlorohydrin is 1:0.95-1.05, and the first reaction conditions include a reaction temperature of 50° C. to 60° C. and a reaction time of 1 hour to 1.5 hours;

[0011] Under the second reaction conditions, the target monomer undergoes a self-polymerization reaction to generate a target polymer, wherein the second reaction conditions include a reaction temperature of 70° C. to 90° C. and a reaction time of 1 h to 2 h;

[0012] The target polymer undergoes a hydrolysis reaction to generate a crude product, wherein the hydrolysis reaction of the target polymer comprises: reacting the target polymer with potassium hydroxide, wherein the amount of the potassium hydroxide is 1% to 2% of the sum of the mass of the N-methylaniline and epichlorohydrin;

[0013] The crude product is subjected to impurity removal treatment to obtain an oligomeric cationic quaternary ammonium salt clay stabilizer.

[0014] In some embodiments, the crude product is subjected to impurity removal treatment to obtain an oligomeric cationic quaternary ammonium salt clay stabilizer, comprising:

[0015] Adjust pH to neutral;

[0016] A mixed solvent consisting of an organic solvent and water is selected as an extractant, and the crude product is extracted at least three times with the extractant to separate an organic phase;

[0017] Rotary evaporation is performed on the organic phase to obtain an oligomeric cationic quaternary ammonium salt clay stabilizer;

[0018] The organic solvent is toluene or methyl isobutyl ketone, and the mass ratio of the organic solvent to water in the extractant is 1-3:1.

[0019] Beneficial effects of the present application: The cation density in the main chain segment of the oligomeric cationic quaternary ammonium salt clay stabilizer of the present application is relatively high, which can neutralize the negative charge of the clay mineral to a great extent, thereby greatly reducing the negative charge density to achieve the purpose of reducing the swelling effect of the clay mineral; and there are a large number of benzene ring groups and polar hydroxyl groups in the oligomeric cationic quaternary ammonium salt clay stabilizer, which can form multi-point effective adsorption with the hydrophobic structure or polar structure on the surface of the clay mineral in the formation environment, effectively preventing the secondary swelling problem of the clay mineral caused by the reduction of cations in the clay due to hydraulic scouring; further, the positive charge carried by the quaternary ammonium cation of the oligomeric cationic quaternary ammonium salt clay stabilizer of the present application can form multi-point tight adsorption with the negative charge carried by the clay mineral, effectively overcoming the problem of loss of the clay stabilizer or reduction in concentration due to water washing. It can be seen that the oligomeric cationic quaternary ammonium salt clay stabilizer of the present application exhibits excellent water-washing resistance and anti-swelling effect;

[0020] At the same time, the residual organic chlorine of the oligomeric cationic quaternary ammonium salt clay stabilizer of the present application is 0, which can avoid the problem of catalyst failure in the crude oil refining stage;

[0021] The oligomeric cationic quaternary ammonium salt clay stabilizer of the present application has a clear preparation mechanism, simple reaction conditions, and simple post-processing operation, and is easy to scale up for production. DETAILED DESCRIPTION

[0022] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0023] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0024] All features, such as values, amounts, contents, and concentrations, described herein as numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to include and specifically disclose all possible subranges and individual values ​​within the range (including integers and fractions).

[0025] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0026] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0027] The following is a further description of the oligomeric cationic quaternary ammonium salt clay stabilizer, the preparation and application of the oligomeric cationic quaternary ammonium salt clay stabilizer provided in the present application in conjunction with specific examples.

[0028] The first aspect of the embodiments of the present application provides an oligomeric cationic quaternary ammonium salt clay stabilizer having the following structural formula:

[0029]

[0030] Among them, n=3-10.

[0031] A second aspect of the embodiments of the present application provides a method for preparing an oligomeric cationic quaternary ammonium salt clay stabilizer, the preparation method comprising the following steps:

[0032] N-methylaniline and epichlorohydrin react under the first reaction conditions to generate the target monomer;

[0033] Under the second reaction conditions, the target monomer undergoes a self-polymerization reaction to generate a target polymer;

[0034] The target polymer undergoes a hydrolysis reaction to generate a crude product;

[0035] The above steps are expressed as follows using the reaction equation:

[0036] ,

[0037] Where n=3-10;

[0038] Finally, the crude product is subjected to impurity removal treatment to obtain an oligomeric cationic quaternary ammonium salt clay stabilizer.

[0039] In some embodiments, the molar ratio of N-methylaniline to epichlorohydrin is 1:0.95-1.05, and the first reaction conditions include a reaction temperature of 50° C.-60° C. and a reaction time of 1 h-1.5 h.

[0040] In some embodiments, the second reaction conditions include a reaction temperature of 70° C.-90° C. and a reaction time of 1 h-2 h.

[0041] In some embodiments, the hydrolysis reaction of the target polymer includes: reacting the target polymer with potassium hydroxide.

[0042] In some embodiments, the amount of potassium hydroxide used is 1%-2% of the sum of the mass of the N-methylaniline and epichlorohydrin.

[0043] In some embodiments, the crude product is subjected to extraction, comprising:

[0044] A mixed solvent consisting of an organic solvent and water is selected as an extractant, and the crude product is extracted at least three times with the extractant;

[0045] The organic solvent is toluene or methyl isobutyl ketone, and the mass ratio of the organic solvent to water in the extractant is 1-3:1.

[0046] The oligomeric cationic quaternary ammonium salt clay stabilizer and its preparation are described below with reference to specific examples.

[0047] Example 1

[0048] Add reactants N-methylaniline (107 g, 1 mol) and methanol (50 g, i.e., solvent) to a small glass reactor. After heating to 55°C, slowly add epichlorohydrin (95.3 g, 1.03 mol) dropwise. Add the reaction mixture dropwise over a period of 1 hour. Maintain the temperature in the reactor at 55°C during the addition. After the addition is complete, heat the reactor to 70°C and maintain the temperature for 2 hours.

[0049] Then, potassium hydroxide solution (20% concentration, 15 g in total) was added in batches until the pH in the reactor stabilized at 9 and did not decrease any further. It should be noted that the amount of potassium hydroxide used here was 3 g;

[0050] Next, hydrochloric acid is added to maintain the pH at neutral, and then extraction is carried out with an extractant consisting of methyl isobutyl ketone and water (the mass ratio of methyl isobutyl ketone to water is 2:1), and the aqueous phase containing inorganic salts is separated. The organic phase is then rotary evaporated using a rotary evaporator to remove the solvent, and finally a light yellow solid product is obtained, which is an oligomeric cationic quaternary ammonium salt clay stabilizer.

[0051] Example 2

[0052] Add reactants N-methylaniline (107 g, 1 mol) and methanol (50 g, i.e., solvent) to a small glass reactor. After heating to 50°C, slowly add epichlorohydrin (97.1 g, 1.05 mol) dropwise. Add the mixture over 1.2 hours. Maintain the temperature in the reactor at 50°C during the addition. After the addition is complete, heat the reactor to 80°C and keep it there for 1.5 hours.

[0053] Then, potassium hydroxide solution (20% concentration, 20 g in total) was added in batches until the pH in the reactor stabilized at 9 and did not decrease any further. It should be noted that the amount of potassium hydroxide used here was 4 g;

[0054] Next, hydrochloric acid is added to maintain the pH at neutral, and then extraction is carried out with an extractant consisting of methyl isobutyl ketone and water (the mass ratio of toluene to water is 3:1), the aqueous phase containing inorganic salts is separated, and the organic phase is further rotary evaporated using a rotary evaporator to remove the solvent, and finally a light yellow solid product is obtained, which is an oligomeric cationic quaternary ammonium salt clay stabilizer.

[0055] Example 3

[0056] Add reactants N-methylaniline (107 g, 1 mol) and methanol (50 g, i.e., solvent) to a small glass reactor. After heating to 60°C, slowly add epichlorohydrin (90.7 g, 0.98 mol) dropwise. Add the mixture over 1.2 hours. Maintain the temperature in the reactor at 60°C during the addition. After the addition is complete, heat the reactor to 90°C and keep it there for 1.5 hours.

[0057] Then, potassium hydroxide solution (20% concentration, 20 g in total) was added in batches until the pH in the reactor stabilized at 8 and did not decrease any further. It should be noted that the amount of potassium hydroxide used here was 2 g;

[0058] Next, hydrochloric acid is added to maintain the pH at neutral, and then extraction is carried out with an extractant consisting of methyl isobutyl ketone and water (the mass ratio of toluene to water is 4:1), the aqueous phase containing inorganic salts is separated, and the organic phase is further rotary evaporated using a rotary evaporator to remove the solvent, and finally a light yellow solid product is obtained, which is an oligomeric cationic quaternary ammonium salt clay stabilizer.

[0059] Example 4

[0060] Add reactants N-methylaniline (107g, 1mol) and methanol (50g, i.e. solvent) to a small glass reactor. After heating to 60°C, slowly add epichlorohydrin (92.5g, 1mol) dropwise. Add the mixture over 1.2 hours. Maintain the temperature in the reactor at 60°C during the addition. After the addition is complete, heat the reactor to 90°C and keep it there for 1.5 hours.

[0061] Then, potassium hydroxide solution (15% concentration, 27 g in total) was added in batches until the pH in the reactor stabilized at 9 and did not decrease any further. It should be noted that the amount of potassium hydroxide used here was 4 g;

[0062] Next, hydrochloric acid is added to maintain the pH at neutral, and then extraction is carried out with an extractant consisting of methyl isobutyl ketone and water (the mass ratio of methyl isobutyl ketone to water is 2:1), and the aqueous phase containing inorganic salts is separated. The organic phase is then rotary evaporated using a rotary evaporator to remove the solvent, and finally a light yellow solid product is obtained, which is an oligomeric cationic quaternary ammonium salt clay stabilizer.

[0063] Anti-swelling performance and water washability test

[0064] The clay stabilizers provided in the above examples, along with the saturated potassium chloride aqueous solution in Comparative Example 1 and the 50% choline chloride clay stabilizer in Comparative Example 2, were tested for anti-swelling performance and water washability according to SY / T5971-2016, "Performance Evaluation Method for Clay Stabilizers for Oil and Gas Field Fracturing, Acidification, and Water Flooding." The specific performance test results are shown in Table 1.

[0065] It should be noted that the formula and proportion of the choline chloride clay stabilizer in the comparative example 2-50% are as follows: the mass ratio of choline chloride, potassium chloride and water is 40:10:50.

[0066] Table 1 Performance test results

[0067]

[0068] As can be seen from Table 1, compared with the small molecule potassium chloride clay stabilizer, the clay stabilizer of the present application has a significantly improved anti-swelling rate and a significantly improved water washing resistance. Compared with the choline chloride clay stabilizer with a shorter chain segment, the anti-swelling performance of the clay stabilizer of the present application is slightly improved. At the same time, the water washing resistance of the clay stabilizer of the present application is even better. This is because: the quaternary ammonium salt positive charge of the oligomeric cationic quaternary ammonium salt clay stabilizer can be closely adsorbed with the negative charge on the surface of the clay mineral, thereby improving the water washing resistance. Moreover, the oligomeric cationic quaternary ammonium salt clay stabilizer contains benzene ring groups and polar hydroxyl groups, and the number of both groups is relatively large. In the formation environment, both can form effective adsorption with the hydrophobic structure or polar structure on the surface of the clay mineral. At the same time, the main chain segment of the oligomeric cationic quaternary ammonium salt clay stabilizer has a high cation density, which can neutralize the negative charge of the clay mineral to a great extent, greatly reducing the negative charge density to achieve the purpose of reducing the swelling effect of the clay mineral. Therefore, the clay stabilizer prepared in the embodiment of the present application has relatively excellent anti-swelling performance and water washing resistance.

[0069] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. An oligomeric cationic quaternary ammonium salt clay stabilizer, characterized in that: It has the following structural formula: ， Among them, n=3-10.

2. A method for preparing the oligomeric cationic quaternary ammonium salt clay stabilizer according to claim 1, characterized in that: The preparation method comprises the following steps: N-methylaniline and epichlorohydrin are reacted under first reaction conditions to produce a target monomer, wherein the molar ratio of the N-methylaniline to the epichlorohydrin is 1:0.95-1.05, and the first reaction conditions include a reaction temperature of 50-60° C. and a reaction time of 1 hour to 1.5 hours; Under the second reaction conditions, the target monomer undergoes a self-polymerization reaction to generate a target polymer, wherein the second reaction conditions include a reaction temperature of 70° C. to 90° C. and a reaction time of 1 h to 2 h; The target polymer undergoes a hydrolysis reaction to generate a crude product, wherein the hydrolysis reaction of the target polymer comprises: reacting the target polymer with potassium hydroxide, wherein the amount of the potassium hydroxide is 1% to 2% of the sum of the mass of the N-methylaniline and epichlorohydrin; The crude product is subjected to impurity removal treatment to obtain an oligomeric cationic quaternary ammonium salt clay stabilizer.

3. The method for preparing an oligomeric cationic quaternary ammonium salt clay stabilizer according to claim 2, wherein: The crude product is subjected to impurity removal treatment to obtain an oligomeric cationic quaternary ammonium salt clay stabilizer, comprising: Adjust pH to neutral; A mixed solvent consisting of an organic solvent and water is selected as an extractant, and the crude product is extracted at least three times with the extractant to separate an organic phase; Rotary evaporation is performed on the organic phase to obtain an oligomeric cationic quaternary ammonium salt clay stabilizer; The organic solvent is toluene or methyl isobutyl ketone, and the mass ratio of the organic solvent to water in the extractant is 1-3:1.

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