A clay maintenance agent and preparation method thereof

Abstract

The present invention relates to the technical field of polymer functional polymer compounds, and in particular to a clay maintenance agent and a preparation method thereof. An embodiment of the present invention provides a method for preparing a clay maintenance agent, comprising: (1) mixing a salt compound and a dispersant with water to obtain a reaction medium solution; (2) adding acrylamide, a functional monomer, and a quaternary ammonium salt monomer to the reaction medium solution to obtain a mixed solution; wherein the functional monomer includes a sulfonate group; (3) introducing nitrogen into the mixed solution, and then adding a first initiator to initiate a polymerization reaction to obtain the clay maintenance agent. An embodiment of the present invention provides a clay maintenance agent and a preparation method thereof, which can provide a clay maintenance agent with excellent fluidity.

Description

Technical Field

[0001] The invention relates to the technical field of polymer functional macromolecular compounds, in particular to a clay maintaining agent and a preparation method thereof. Background Art

[0002] Clay retainer is a chemical reagent used in oil and gas resource exploration. Its main function is to prevent the migration of clay and particles through electrostatic force and prevent clay hydration and expansion.

[0003] In the related art, the clay retaining agent has poor fluidity and is prone to gelation during the preparation process.

[0004] Therefore, in view of the above shortcomings, a clay retaining agent and a preparation method thereof are urgently needed. Summary of the invention

[0005] The embodiment of the present invention provides a clay retaining agent and a preparation method thereof, which can provide a clay retaining agent with excellent fluidity.

[0006] In a first aspect, an embodiment of the present invention provides a method for preparing a clay maintenance agent, comprising:

[0007] (1) mixing a salt compound and a dispersant with water to obtain a reaction medium solution;

[0008] (2) adding acrylamide, functional monomers, and quaternary ammonium salt monomers into the reaction medium solution to obtain a mixed solution; wherein the functional monomers include sulfonate groups;

[0009] (3) nitrogen is introduced into the mixed solution, and then a first initiator is added to initiate a polymerization reaction to obtain the clay retaining agent.

[0010] In a possible design, after step (3), the method further includes:

[0011] (4) Adding a salting-out agent to the reaction solution.

[0012] In a possible design, the dispersant is prepared by the following method:

[0013] Add acrylamide and cationic monomer into water and mix well;

[0014] Raise the temperature to 50-55°C in a nitrogen environment and keep warm for 40-60 minutes;

[0015] A second initiator is added and the temperature is raised to 70-75° C. to carry out a polymerization reaction, and the dispersant is obtained after keeping the temperature for 3-4 hours.

[0016] In a possible design, the solid content of the dispersant is 20-25%, and the viscosity average molecular weight is 800,000-3,000,000;

[0017] In the process of preparing the dispersant, the mass ratio of acrylamide to the cationic monomer is (1-4):(8-9), and the mass ratio of the second initiator to acrylamide is (0.001-0.004):1.

[0018] In a possible design, the cationic monomer includes at least one of methacryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, and diallyl dimethyl ammonium chloride;

[0019] The second initiator includes at least one of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobisisoheptanenitrile, and azobisisobutylonitrile.

[0020] In one possible design, step (2) includes:

[0021] Adding acrylamide, functional monomer, quaternary ammonium salt monomer, structure regulator and chelating agent into the reaction medium solution to obtain a mixed solution;

[0022] The mass fractions of each raw material component for preparing the clay maintenance agent are as follows:

[0023] 120 to 190 parts of the salt compound, 20 to 30 parts of the dispersant, 400 to 600 parts of water, 100 to 150 parts of acrylamide, 20 to 30 parts of the functional monomer, 50 to 80 parts of the quaternary ammonium salt monomer, 1 to 5 parts of the structure regulator, 0.1 to 0.15 parts of the chelating agent, 0.1 to 0.2 parts of the first initiator, and 40 to 60 parts of the salting-out agent.

[0024] In one possible design, the salt compound includes at least one of ammonium sulfate, sodium sulfate and potassium sulfate;

[0025] The functional monomer includes at least one of sodium 2-acrylamido-2-methylpropane sulfonate, sodium allyl sulfonate, and sodium vinyl sulfonate;

[0026] The structural regulator includes at least one of N-vinyl-N-methyl-2-acrylamide and N-allyl methacrylamide;

[0027] The chelating agent includes at least one of disodium ethylenediaminetetraacetate, trisodium N-hydroxyethylethylenediaminetriacetate, and pentasodium diethylenetriaminepenta(methylenephosphonate);

[0028] The salting-out agent is at least one of ammonium sulfate, sodium sulfate, sodium chloride and ammonium chloride;

[0029] The first initiator includes a redox initiator and an azo initiator in a mass ratio of (1 to 1.5):1, the redox initiator includes a combination of potassium persulfate and sodium bisulfite, a combination of ammonium persulfate and sodium bisulfite, or a combination of hydrogen peroxide and sodium bisulfite, and the azo initiator is at least one of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobisisoheptanenitrile, and azobisisobutyronitrile.

[0030] In one possible design, the preparation method of the quaternary ammonium salt monomer is as follows:

[0031] Add hydrochloride organic monomer into water and mix well;

[0032] Add benzyl chloride and control the temperature at 38-40 degrees Celsius;

[0033] Adjusting the pH value to 8-9 to obtain the quaternary ammonium salt monomer;

[0034] The hydrochloride organic monomer includes at least one of diethylamine diphenylbutenoic acid ethyl ester hydrochloride and 4,4-biphenyl crotonic acid 2-(diethylamino)ethyl ester hydrochloride.

[0035] In a possible design, in step (2), the mass ratio of acrylamide, the functional monomer and the quaternary ammonium salt monomer is (10-15):(2-3):(5-8);

[0036] and / or,

[0037] After step (2) and before step (3), the method further includes:

[0038] The Ph value of the mixed solution is adjusted to 4-6.

[0039] In a second aspect, an embodiment of the present invention further provides a clay retaining agent, which is prepared by any of the above-mentioned preparation methods.

[0040] Compared with the prior art, the present invention has at least the following beneficial effects:

[0041] In this embodiment, the functional monomer participates in the polymerization reaction so that the obtained clay maintenance agent has multiple sulfonic acid groups, and the sulfonic acid groups make the clay maintenance agent have excellent temperature resistance. The quaternary ammonium salt monomer participates in the polymerization reaction so that the obtained clay maintenance agent has multiple cationic groups, and the cationic groups make the clay maintenance agent have excellent salt resistance. In step (1) of the present invention, a reaction medium with a dispersing function is first prepared, wherein the salt compound serves as a dispersing medium. Various monomers are added to the reaction medium with a dispersing function, and the dispersant and the dispersing medium effectively prevent the various monomers from agglomerating to form a colloid during the polymerization process, so that the various monomers are evenly distributed, and a milky white liquid with good fluidity is obtained after polymerization, and its apparent viscosity is 80 to 200 mPa·s. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 The present invention provides a flow chart of a method for preparing a clay maintenance agent. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0045] In the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance; unless otherwise specified or explained, the term "multiple" refers to two or more; the terms "connected" and "fixed" should be understood in a broad sense, for example, "connected" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] like Figure 1 As shown, an embodiment of the present invention provides a method for preparing a clay maintenance agent, comprising:

[0047] (1) mixing a salt compound and a dispersant with water to obtain a reaction medium solution;

[0048] (2) adding acrylamide, functional monomers, and quaternary ammonium salt monomers into a reaction medium solution to obtain a mixed solution; wherein the functional monomers include sulfonate groups;

[0049] (3) nitrogen is introduced into the mixed solution, and then a first initiator is added to initiate a polymerization reaction to obtain a clay retaining agent.

[0050] In this embodiment, the functional monomer participates in the polymerization reaction so that the obtained clay maintenance agent has multiple sulfonic acid groups, and the sulfonic acid groups make the clay maintenance agent have excellent temperature resistance. The quaternary ammonium salt monomer participates in the polymerization reaction so that the obtained clay maintenance agent has multiple cationic groups, and the cationic groups make the clay maintenance agent have excellent salt resistance. In step (1) of the present invention, a reaction medium with a dispersing function is first prepared, wherein the salt compound serves as a dispersing medium. Various monomers are added to the reaction medium with a dispersing function, and the dispersant and the dispersing medium effectively prevent the various monomers from agglomerating to form a colloid during the polymerization process, so that the various monomers are evenly distributed, and a milky white liquid with good fluidity is obtained after polymerization, and its apparent viscosity is 80 to 200 mPa·s (for example, it can be 80 mPa·s, 90 mPa·s, 100 mPa·s, 120 mPa·s, 140 mPa·s, 160 mPa·s, 180 mPa·s or 200 mPa·s).

[0051] In the present invention, since oxygen, as an inhibitor, will affect the polymerization reaction of polyacrylamide, nitrogen needs to be introduced to remove oxygen to ensure that the polymerization reaction proceeds normally.

[0052] It should be noted that the water in the present application is preferably deionized water. When multiple solutes are dissolved or dispersed in a solvent, the solutes are preferably added sequentially, that is, as long as the previous substance is completely dissolved or dispersed in the mixed solution, the next substance is added sequentially.

[0053] In this embodiment, in step (2), the obtained mixed solution is heated to 25-30°C (for example, 25°C, 26°C, 28°C or 30°C), and then nitrogen is introduced for 30-40 minutes (for example, 30 minutes, 35 minutes, 40 minutes), and then the first initiator is added to initiate the polymerization reaction, and the reaction is carried out at 50-60°C (for example, 50°C, 55°C or 60°C) for 3-4 hours (for example, 3 hours, 3.5 hours, 4 hours), and then the mixture is kept at 60-65°C for 3-4 hours to obtain the reaction product solution. It should be noted that the 3-4 hours of keeping warm is to ensure that the monomers are fully reacted to improve the monomer conversion rate.

[0054] In some embodiments of the present invention, after step (3), the method further includes:

[0055] (4) Add a salting-out agent to the reaction solution.

[0056] In this embodiment, a salting-out agent is added to the reaction product solution and stirred for 1-1.5 hours. The ions ionized by the salting-out agent in water can not only shield the electrostatic repulsion between the polymers (i.e., clay retaining agents) obtained by the polymerization reaction, but also meet the requirements of the electrical neutrality of the two phases of the dispersion, balance the osmotic pressure between the two phases, reduce the entropy loss generated during the separation of the polymer phases, promote the phase separation of the amphoteric polymer in the aqueous solution, and make the apparent viscosity of the obtained polymer clay retaining agent for drilling fluid the lowest.

[0057] It should be noted that the two phases are a continuous phase and a dispersed phase, the continuous phase is a reaction solvent, the dispersed phase is a reaction polymer phase, and a salting-out agent is added to separate the dispersed phase, i.e., small polymer particles, from the continuous phase.

[0058] In some embodiments of the present invention, the dispersant is prepared by the following method:

[0059] Add acrylamide and cationic monomer into water and mix well;

[0060] Raise the temperature to 50-55°C in a nitrogen environment and keep warm for 40-60 minutes;

[0061] Add the second initiator and raise the temperature to 70-75°C to carry out polymerization reaction. Keep the temperature for 3-4 hours to obtain the dispersant.

[0062] In this embodiment, acrylamide and cationic monomer are sequentially added into deionized water and stirred for 20-30 min (for example, 20 min, 25 min or 30 min), then the temperature is raised to 50-55° C. (for example, 50° C., 52° C., 54° C. or 55° C.), nitrogen is introduced for 40-60 min (for example, 40 min, 50 min or 60 min), and then an azo initiator is added to initiate the polymerization reaction, and the reaction is carried out at 70-75° C. (for example, 70° C., 71° C., 72° C., 73° C., 74° C., 75° C.) for 3-4 h (for example, 3 h, 3.5 h, 4 h) to obtain a dispersant.

[0063] The present invention adopts cationic polyacrylamide oligomer as dispersant, which has fast dissolution speed and enables polymer chains formed by free radical polymerization to be precipitated in time to form stable latex particles, and can effectively control the viscosity of the system during the polymerization reaction to avoid gelation caused by sudden increase of system viscosity.

[0064] It should be noted that the present polymer system is a cationic polymerization system, and the corresponding dispersant should also be a cationic dispersant, and there are also requirements for the viscosity of the dispersant. Therefore, it is preferred to make a dispersant of a type and year suitable for the needs.

[0065] In some embodiments of the present invention, the solid content of the dispersant is 20-25% (for example, it can be 20%, 21%, 22%, 23%, 24, 25%), and the viscosity average molecular weight is 800,000-3 million (for example, it can be 800,000, 1 million, 1.2 million, 1.4 million, 1.6 million, 1.8 million, 2 million, 2.2 million, 2.4 million, 2.6 million, 2.8 million, 3 million, 2 million);

[0066] In the process of preparing the dispersant, the mass ratio of acrylamide to the cationic monomer is (1-4):(8-9) (for example, it can be 1:8, 1:9, 2:8, 2:9, 3:8, 3:9, 4:8, 4:9), and the mass ratio of the second initiator to acrylamide is (0.001-0.004):1 (for example, it can be 0.002:1, 0.0025:1, 0.003:1 or 0.004:1).

[0067] In the present invention, the viscosity average molecular weight of the dispersant is 800,000 to 3,000,000, which can ensure that the dispersant is completely dissolved in the reaction medium.

[0068] In some embodiments of the present invention, the cationic monomer includes at least one of methacryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, and diallyl dimethyl ammonium chloride;

[0069] The second initiator includes at least one of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobisisoheptanenitrile, and azobisisobutylonitrile.

[0070] In some embodiments of the present invention, step (2) comprises:

[0071] Adding acrylamide, functional monomer, quaternary ammonium salt monomer, structure regulator and chelating agent into the reaction medium solution to obtain a mixed solution;

[0072] The mass fractions of each raw material component for preparing the clay maintenance agent are as follows:

[0073] 120-190 parts of salt compounds, 20-30 parts of dispersants, 400-600 parts of water, 100-150 parts of acrylamide, 20-30 parts of functional monomers, 50-80 parts of quaternary ammonium salt monomers, 1-5 parts of structural regulators, 0.1-0.15 parts of chelating agents, 0.1-0.2 parts of first initiators, and 40-60 parts of salting-out agents.

[0074] In some embodiments of the present invention, the salt compound includes at least one of ammonium sulfate, sodium sulfate and potassium sulfate;

[0075] The functional monomer includes at least one of sodium 2-acrylamido-2-methylpropane sulfonate, sodium allyl sulfonate, and sodium vinyl sulfonate;

[0076] The structural regulator includes at least one of N-vinyl-N-methyl-2-acrylamide and N-allyl methacrylamide;

[0077] The chelating agent includes at least one of disodium ethylenediaminetetraacetate, trisodium N-hydroxyethylethylenediaminetriacetate, and pentasodium diethylenetriaminepenta(methylenephosphonate);

[0078] The salting-out agent is at least one of ammonium sulfate, sodium sulfate, sodium chloride and ammonium chloride;

[0079] The first initiator includes a redox initiator and an azo initiator in a mass ratio of (1 to 1.5):1, the redox initiator includes a combination of potassium persulfate and sodium bisulfite, a combination of ammonium persulfate and sodium bisulfite, or a combination of hydrogen peroxide and sodium bisulfite, and the azo initiator is at least one of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobisisoheptanenitrile, and azobisisobutyronitrile.

[0080] In this embodiment, the salt compound is preferably sulfate, which is a very good dispersion medium. If other inorganic salts are used, the dispersion effect of the system is poor and the apparent viscosity is relatively high.

[0081] In the present invention, the first initiator can initiate the polymerization reaction at low temperature with the help of the redox initiator. The heat released by the reaction causes the temperature of the reaction system to rise, so that the azo initiator decomposes to generate free radicals to continuously initiate the polymerization reaction, thereby reducing energy consumption and improving the polymerization reaction conversion rate and the molecular weight of the polymer.

[0082] In some embodiments of the present invention, the preparation method of the quaternary ammonium salt monomer is as follows:

[0083] Add hydrochloride organic monomer into water and mix well;

[0084] Add benzyl chloride and control the temperature at 38-40 degrees Celsius;

[0085] Adjusting the pH value to 8-9 to obtain a quaternary ammonium salt monomer;

[0086] The hydrochloride organic monomer includes at least one of diethylamine diphenylbutenoic acid ethyl ester hydrochloride (CAS No.: 63992-55-2) and 4,4-biphenylcrotonic acid 2-(diethylamino)ethyl ester hydrochloride (CAS No.: 69928-42-3).

[0087] In this embodiment, the synthetic quaternary ammonium salt monomer is a laboratory synthetic monomer, and the specific synthesis method is as follows:

[0088] ① Weigh 100-150g of hydrochloride organic monomer and 20-30g of deionized water into a 250mL three-necked flask. Stir for 0.5h to fully dissolve, then drop 70-80g of benzyl chloride into the three-necked flask for 1-1.5h. During the dropwise addition, the temperature of the water bath rises to 40℃, and the temperature in the three-necked flask is kept at no more than 40℃. After the dropwise addition is completed, keep the temperature constant for 1h to ensure full reaction.

[0089] ② After keeping the temperature constant for 1 hour, add 7-8 grams of acetic acid and 30-40 grams of deionized water, stir thoroughly for 0.5 hours to make the pH between 8.0 and 9.0, and the preparation of the synthetic quaternary ammonium salt monomer is completed.

[0090] In this embodiment, hydrochloride and benzyl chloride undergo quaternization reaction, and the reaction product is a cationic monomer, which carries cationic charge, is beneficial to the charge stability balance of the system, and makes the clay retaining agent more stable.

[0091] The reaction equation of diethylamine diphenyl crotonate hydrochloride and benzyl chloride is:

[0092]

[0093] The reaction equation of 4,4-biphenyl crotonic acid 2-(diethylamino)ethyl ester hydrochloride and benzyl chloride is:

[0094]

[0095] In the present invention, the laboratory-made quaternary ammonium salt monomer has multiple heterocyclic structures, which improves the rigidity of the molecular chain, has good shear resistance, good viscosity recovery ability and good clay anti-swelling rate. In addition, the heterocyclic structure can also make the molecular chain segment more stable, and the clay maintenance agent has good stability, making it difficult to hydrolyze under high temperature and humid storage conditions, maintaining pH stability, and improving the viscosity value of the clay maintenance agent in water.

[0096] In some embodiments of the present invention, in step (2), the mass ratio of acrylamide, functional monomer and quaternary ammonium salt monomer is (10-15):(2-3):(5-8);

[0097] and / or,

[0098] After step (2) and before step (3), the method further includes:

[0099] The Ph value of the mixed solution is adjusted to 4-6 (for example, 4.0, 4.5, 5.0, 5.5, 6.0). Specifically, the adjustment may include but is not limited to using acetic acid and sodium hydroxide aqueous solution.

[0100] In this embodiment, when the pH is too high, the system does not react; when the pH is too low, the system reacts quickly and the dilution viscosity is low.

[0101] It has been experimentally confirmed that with the increase of the amount of acrylamide, the molecular weight of the obtained clay maintenance agent gradually increases, but when the amount is too large, the viscosity of the synthesized clay maintenance agent will be too high and even gel will be generated, thereby affecting the polymerization process; when the functional monomer is excessive, it is easy to cause the molecular weight of the obtained clay maintenance agent to be low and the solubility is poor; when the synthetic quaternary ammonium salt monomer is excessive, the molecular weight of the obtained clay maintenance agent will be low; and when the amount of cationic monomer is too small, the cationic groups in the synthetic polymer process are less, which is unfavorable for the anti-swelling effect. In this way, through the preparation method of the present invention, it is also possible to control the clay maintenance agent to have an excellent anti-swelling effect by controlling the mass fractions of the added acrylamide, functional monomer, and synthetic quaternary ammonium salt monomer.

[0102] It should be noted that at least one is any one or a mixture of any several in any proportion.

[0103] The embodiment of the present invention further provides a clay retaining agent, which is prepared by any preparation method in the above embodiments.

[0104] In order to more clearly illustrate the technical solution and advantages of the present invention, a method for preparing a clay retaining agent is described in detail below through several embodiments.

[0105] Example 1

[0106] (1) 130 parts of ammonium sulfate and 25 parts of a dispersant were sequentially added to 528 parts of deionized water and stirred to obtain a reaction medium solution;

[0107] (2) 100 parts of acrylamide, 30 parts of sodium 2-acrylamido-2-methylpropane sulfonate, 50 parts of a synthetic quaternary ammonium salt monomer, 2 parts of N-allyl methacrylamide and 0.13 parts of disodium ethylenediaminetetraacetate are sequentially added to the reaction medium and mixed evenly, and the pH of the solution is adjusted to 5.0 using acetic acid and a 50% by mass NaOH aqueous solution to obtain a mixed solution;

[0108] (3) the mixed solution was heated to 27° C., nitrogen was introduced for 30 min, and then 0.15 parts of the first initiator (0.05 parts of potassium persulfate, 0.025 parts of sodium bisulfite and 0.075 parts of azobisisobutylamidine hydrochloride) were added to initiate the polymerization reaction, and the reaction was continued at 72° C. for 3.5 h to obtain a reaction product solution;

[0109] (4) adding 45 parts of sodium sulfate to the reaction product solution and stirring for 1 hour to obtain a precipitated drilling clay retaining agent;

[0110] The preparation method of the dispersant is as follows: 30 parts of acrylamide and 240 parts of acryloyloxyethyltrimethylammonium chloride are sequentially added to 730 parts of deionized water and stirred for 30 minutes, then the temperature is raised to 55°C, nitrogen is introduced for 40 minutes, and then 0.03 parts of azobisisobutyramidine hydrochloride is added to initiate polymerization reaction, and the reaction is carried out at 73°C for 4 hours to obtain the dispersant.

[0111] Wherein, the synthetic quaternary ammonium salt monomer is a laboratory synthetic monomer, and the synthetic method is as follows:

[0112] (1) Weigh 100 g of diethylamine diphenylbutyl ester hydrochloride and 20 g of deionized water and add them to a 250 mL three-necked flask. Stir for 0.5 h to fully dissolve it, then drop 75 g of benzyl chloride into the three-necked flask for 1.5 h. During the dropwise addition, the temperature of the water bath rises to 40°C and the temperature in the three-necked flask is kept at no more than 40°C. After the dropwise addition is completed, the temperature is kept constant for 1 h to ensure full reaction.

[0113] (2) After maintaining the temperature for 1 hour, 7 g of acetic acid and 30 g of deionized water were added, and the mixture was stirred for 0.5 hour to adjust the pH value to between 8.0 and 9.0. The preparation of the synthetic quaternary ammonium salt monomer was completed.

[0114] Example 2

[0115] (1) 150 parts of ammonium sulfate and 26 parts of a dispersant were sequentially added to 556 parts of deionized water and stirred to obtain a reaction medium;

[0116] (2) 120 parts of acrylamide, 25 parts of sodium 2-acrylamido-2-methylpropane sulfonate, 60 parts of a synthetic quaternary ammonium salt monomer, 2 parts of N-allyl methacrylamide and 0.13 parts of disodium ethylenediaminetetraacetate are sequentially added to the reaction medium and mixed evenly, and the pH of the solution is adjusted to 5.0 using acetic acid and a 50% by mass NaOH aqueous solution to obtain a mixed solution;

[0117] (3) the mixed solution was heated to 27° C., nitrogen was introduced for 30 min, and then 0.15 parts of the first initiator (0.05 parts of potassium persulfate, 0.025 parts of sodium bisulfite and 0.075 parts of azobisisobutylamidine hydrochloride) were added to initiate the polymerization reaction, and the reaction was continued at 72° C. for 3.5 h to obtain a reaction product solution;

[0118] (4) adding 45 parts of sodium sulfate to the reaction product solution and stirring for 1 hour to obtain a precipitated drilling clay retaining agent;

[0119] The preparation method of the dispersant is as follows: 30 parts of acrylamide and 240 parts of acryloyloxyethyltrimethylammonium chloride are sequentially added to 730 parts of deionized water and stirred for 30 minutes, then the temperature is raised to 55°C, nitrogen is introduced for 40 minutes, and then 0.03 parts of azobisisobutyramidine hydrochloride is added to initiate polymerization reaction, and the reaction is carried out at 73°C for 4 hours to obtain the dispersant.

[0120] Wherein, the synthetic quaternary ammonium salt monomer is a laboratory synthetic monomer, and the synthetic method is as follows:

[0121] (1) Weigh 100 g of diethylamine diphenylbutyl ester hydrochloride and 20 g of deionized water and add them to a 250 mL three-necked flask. Stir for 0.5 h to fully dissolve it, then drop 75 g of benzyl chloride into the three-necked flask for 1.5 h. During the dropwise addition, the temperature of the water bath rises to 40°C and the temperature in the three-necked flask is kept at no more than 40°C. After the dropwise addition is completed, the temperature is kept constant for 1 h to ensure full reaction.

[0122] (2) After maintaining the temperature for 1 hour, 7 g of acetic acid and 30 g of deionized water were added, and the mixture was stirred for 0.5 hour to adjust the pH value to between 8.0 and 9.0. The preparation of the synthetic quaternary ammonium salt monomer was completed.

[0123] Example 3

[0124] (1) 150 parts of ammonium sulfate and 30 parts of a dispersant were sequentially added to 510 parts of deionized water and stirred to obtain a reaction medium;

[0125] (2) 130 parts of acrylamide, 23 parts of sodium 2-acrylamido-2-methylpropane sulfonate, 50 parts of a synthetic quaternary ammonium salt monomer, 2 parts of N-allyl methacrylamide and 0.13 parts of disodium ethylenediaminetetraacetate are sequentially added to the reaction medium and mixed evenly, and the pH of the solution is adjusted to 5.0 using acetic acid and a 50% by mass NaOH aqueous solution to obtain a mixed solution;

[0126] (3) the mixed solution was heated to 27° C., nitrogen was introduced for 30 min, and then 0.15 parts of the first initiator (0.05 parts of potassium persulfate, 0.025 parts of sodium bisulfite and 0.075 parts of azobisisobutylamidine hydrochloride) were added to initiate the polymerization reaction, and the reaction was continued at 72° C. for 3.5 h to obtain a reaction product solution;

[0127] (4) adding 45 parts of sodium sulfate to the reaction product solution and stirring for 1 hour to obtain a precipitated drilling clay retaining agent;

[0128] The preparation method of the dispersant is as follows: 30 parts of acrylamide and 240 parts of acryloyloxyethyltrimethylammonium chloride are sequentially added to 730 parts of deionized water and stirred for 30 minutes, then the temperature is raised to 55°C, nitrogen is introduced for 40 minutes, and then 0.03 parts of azobisisobutyramidine hydrochloride is added to initiate polymerization reaction, and the reaction is carried out at 73°C for 4 hours to obtain the dispersant.

[0129] Wherein, the synthetic quaternary ammonium salt monomer is a laboratory synthetic monomer, and the synthetic method is as follows:

[0130] (1) Weigh 100 g of diethylamine diphenylbutyl ester hydrochloride and 20 g of deionized water and add them to a 250 mL three-necked flask. Stir for 0.5 h to fully dissolve it, then drop 75 g of benzyl chloride into the three-necked flask for 1.5 h. During the dropwise addition, the temperature of the water bath rises to 40°C and the temperature in the three-necked flask is kept at no more than 40°C. After the dropwise addition is completed, the temperature is kept constant for 1 h to ensure full reaction.

[0131] (2) After maintaining the temperature for 1 hour, 7 g of acetic acid and 30 g of deionized water were added, and the mixture was stirred for 0.5 hour to adjust the pH value to between 8.0 and 9.0. The preparation of the synthetic quaternary ammonium salt monomer was completed.

[0132] Example 4

[0133] Embodiment 4 is substantially the same as Embodiment 1, except that:

[0134] The weight proportions of the components are different, including 170 parts of salt compounds, 28 parts of dispersants, 582 parts of deionized water, 110 parts of acrylamide, 20 parts of functional monomers, 65 parts of synthetic quaternary ammonium salt monomers, 4 parts of structural regulators, 0.13 parts of chelating agents, 0.2 parts of first initiators (0.067 parts of potassium persulfate, 0.033 parts of sodium bisulfite and 0.01 parts of azobisisobutylamidine hydrochloride), and 50 parts of salting-out agents.

[0135] Example 5

[0136] Embodiment 5 is substantially the same as Embodiment 1, except that:

[0137] The weight proportions of the components are different, including 180 parts of salt compounds, 22 parts of dispersants, 489 parts of deionized water, 105 parts of acrylamide, 27 parts of functional monomers, 80 parts of synthetic quaternary ammonium salt monomers, 1 part of structural regulators, 0.13 parts of chelating agents, 0.17 parts of first initiators (0.057 parts of potassium persulfate, 0.028 parts of sodium bisulfite and 0.085 parts of azobisisobutylamidine hydrochloride), and 58 parts of salting-out agents.

[0138] Comparative Example 1

[0139] Comparative Example 1 is substantially the same as Example 1, except that diethylamine diphenylbutyl ester hydrochloride is replaced by dimethylaminoethyl acrylate.

[0140] Comparative Example 2

[0141] Comparative Example 2 is substantially the same as Example 1, except that the functional monomer is replaced with deionized water, that is, no functional monomer is added.

[0142] Comparative Example 3

[0143] Comparative Example 3 is basically the same as Example 1, except that the reaction medium solution is not prepared according to step (1), and the raw material components in step (2) are directly added to deionized water. After the polymerization reaction, a gel product is obtained, which cannot be used.

[0144] The following tests were performed on Examples 1-5 and Comparative Examples 1-2:

[0145] (1) Determination of viscosity-average molecular weight

[0146] The intrinsic viscosity of the synthesized copolymer was measured with reference to GB12005.1-89 "Determination method of intrinsic viscosity of polyacrylamide", the intrinsic viscosity was measured using an Ubbelohde viscometer, and the viscosity-average molecular weight was calculated according to the formula (as shown in Table 1).

[0147] (2) Determination of montmorillonite anti-swelling rate

[0148] The anti-swelling rate of montmorillonite was measured with reference to SY / T 5971-94 "Evaluation Method of Clay Maintaining Agent for Water Injection" (as shown in Table 1). 0.5 g of montmorillonite baked at high temperature was added to 10 mL of the clay maintaining agent solution to be tested, mixed evenly and placed in a centrifuge tube. After standing for 2 hours, centrifuged at 1500 r / min for 15 minutes.

[0149] B=[(V2-V1) / (V2-V0)]×100%

[0150] Wherein: B-anti-swelling rate, %; V1-swelling volume of montmorillonite in clay retainer solution, mL; V2-swelling volume of montmorillonite in water solution, mL; V0-swelling volume of montmorillonite in kerosene, mL.

[0151] (3) Determination of dilution viscosity

[0152] 348 g of deionized water was poured into a 500 ml glass beaker, and 12 g of polymer was quickly added under magnetic stirring at 500 r / min. After stirring for 10 min, a Brookfield viscometer with a 62# rotor at 30 r / min was used to test for 30 seconds to read the viscosity value (as shown in Table 1).

[0153] Table 1

[0154]

[0155]

[0156] It can be seen from the data in Table 1 that the polymer clay retainer for drilling fluid prepared in the embodiment of the present invention is a white emulsion; compared with the polymers prepared in Comparative Examples 1 and 2, the clay retainer obtained in the embodiment of the present invention has a higher viscosity-average molecular weight and a certain concentration of polymer aqueous solution can more effectively inhibit the hydration expansion of montmorillonite and a higher dilution viscosity.

[0157] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a clay maintenance agent, characterized in that: include: (1) mixing a salt compound and a dispersant with water to obtain a reaction medium solution; (2) adding acrylamide, functional monomer, quaternary ammonium salt monomer, structure regulator and chelating agent to the reaction medium solution to obtain a mixed solution; (3) introducing nitrogen into the mixed solution, and then adding a first initiator to initiate a polymerization reaction; After step (3), the method further includes: (4) adding a salting-out agent to the mixed solution; The dispersant is prepared by the following method: Add acrylamide and cationic monomer into water and mix well; Raise the temperature to 50-55°C in a nitrogen environment and keep warm for 40-60 minutes; Add the second initiator and raise the temperature to 70-75° C. to carry out polymerization reaction, and keep the temperature for 3-4 hours to obtain the dispersant; The solid content of the dispersant is 20-25%, and the viscosity average molecular weight is 800,000-3,000,000; In the process of preparing the dispersant, the mass ratio of acrylamide to the cationic monomer is (1-4):(8-9), and the mass ratio of the second initiator to acrylamide is (0.001-0.004):1; The cationic monomer includes at least one of methacryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, and diallyl dimethyl ammonium chloride; The second initiator includes at least one of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobisisoheptanenitrile, and azobisisobutyronitrile; The mass fractions of each raw material component for preparing the clay maintenance agent are as follows: 120-190 parts of the salt compound, 20-30 parts of the dispersant, 400-600 parts of water, 100-150 parts of acrylamide, 20-30 parts of the functional monomer, 50-80 parts of the quaternary ammonium salt monomer, 1-5 parts of the structure regulator, 0.1-0.15 parts of the chelating agent, 0.1-0.2 parts of the first initiator, and 40-60 parts of the salting-out agent; The salt compound includes at least one of ammonium sulfate, sodium sulfate and potassium sulfate; The functional monomer includes at least one of sodium 2-acrylamido-2-methylpropane sulfonate, sodium allyl sulfonate, and sodium vinyl sulfonate; The structural regulator includes at least one of N-vinyl-N-methyl-2-acrylamide and N-allyl methacrylamide; The chelating agent includes at least one of disodium ethylenediaminetetraacetate, trisodium N-hydroxyethylethylenediaminetriacetate, and pentasodium diethylenetriaminepenta(methylenephosphonate); The salting-out agent is at least one of ammonium sulfate, sodium sulfate, sodium chloride and ammonium chloride; The first initiator comprises a redox initiator and an azo initiator in a mass ratio of (1-1.5):1, wherein the redox initiator comprises a combination of potassium persulfate and sodium bisulfite, a combination of ammonium persulfate and sodium bisulfite, or a combination of hydrogen peroxide and sodium bisulfite, and the azo initiator is at least one of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobisisoheptanenitrile, and azobisisobutyronitrile; The preparation method of the quaternary ammonium salt monomer is as follows: Add hydrochloride organic monomer into water and mix well; Add benzyl chloride and control the temperature at 38-40 degrees Celsius; Adjusting the pH value to 8-9 to obtain the quaternary ammonium salt monomer; The hydrochloride organic monomer includes at least one of diethylamine diphenyl crotonate ethyl ester hydrochloride and 4,4-biphenyl crotonate 2-(diethylamino) ethyl ester hydrochloride; In step (2), the mass ratio of acrylamide, the functional monomer and the quaternary ammonium salt monomer is (10-15): (2-3): (5-8); and / or, After step (2) and before step (3), the method further includes: The pH value of the mixed solution is adjusted to 4-6.

2. A clay retaining agent, characterized in that The preparation method according to claim 1 is used for preparation.

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