A clay stabilizer and its preparation method

Abstract

This invention provides a clay stabilizer and its preparation method. First, a low molecular weight polymer is obtained by polymerizing acrylate, acrylamide, and dimethyl diallyl ammonium chloride in an aqueous solution. Then, an amidation reaction is carried out with enamine or alkyl diamine to obtain the clay stabilizer. This clay stabilizer has the advantages of good anti-swelling effect and long-lasting effect, effectively preventing clay particle migration, good temperature resistance, not increasing formation water salinity, and increasing formation permeability. The anti-swelling rate is ≥95%, the anti-swelling rate after aging at 350℃ is ≥90%, the water washing resistance rate is ≥97%, the core permeability recovery rate is ≥85%, and the core permeability retention rate is ≥90%.

Description

Technical Field

[0001] This invention belongs to the field of oilfield engineering technology. Specifically, this invention relates to a clay stabilizer and its preparation method. Background Technology

[0002] Clay is a common mineral found in geological formations. Because clay swells when exposed to water, during reservoir development processes such as water injection, acidizing, or fracturing in oilfields, the porosity in clay-rich reservoirs decreases due to clay expansion, leading to significant pore blockage and water-sensitive damage. To mitigate this reservoir damage, clay anti-swelling agents are widely used. These agents effectively adsorb onto the clay surface, preventing the hydration, expansion, and dispersion of water-sensitive minerals within the reservoir, thus preventing damage to the oil and gas layer and impacting oilfield development.

[0003] With the advancement of oilfield extraction technology, the application of clay anti-swelling agents has become more and more widespread, and the types are increasing. Based on the different chemical compositions and mechanisms of action, there are three main stages: (1) the early stage of inorganic salt clay anti-swelling agents, which mainly utilize inorganic salt ions such as K+. ＋ (1) Embedded in the clay crystal structure to neutralize electronegativity; (2) In the 1970s, inorganic polynuclear polymers and cationic surfactants were used to stabilize clay and form a hydrophobic layer on the surface of clay particles to prevent further hydration of clay; (3) Since the 1980s, research and experiments have been mainly carried out on stabilizing clay with cationic organic polymers. Representative products include cationic polyacrylamide with a certain molecular weight, polyamine compounds and hyperbranched molecules.

[0004] CN105198757B discloses a small cationic bisquaternary ammonium salt clay stabilizer and its preparation method. Using epichlorohydrin, small molecule tertiary amine and hydrochloric acid as raw materials, the clay stabilizer achieves high positive charge density by forming small molecule tertiary amine hydrochloride and epichlorohydrin, thus giving it good stability and clay expansion inhibition ability.

[0005] CN106279661B discloses a quaternary ammonium salt-type cationic polymer, which is obtained by chemical reaction of aliphatic amines, acids, epichlorohydrin, and terminal diamines. This polymer can adsorb onto the surface of clay particles, significantly improving the anti-swelling effect of clay anti-swelling agents at low dosages. This clay anti-swelling agent can be used in drilling, cementing, water injection, fracturing, acidizing, and well workover operations to effectively prevent the hydration swelling and dispersion migration of clay.

[0006] CN107312507B discloses a method for preparing a clay stabilizer for low-permeability formations, comprising the following steps: adding epichlorohydrin to an aqueous solution of a monohydric aliphatic amine and reacting for a certain time; adding more epichlorohydrin and heating to allow the reaction to proceed; adding a polyamine and then adding more epichlorohydrin and reacting again; drying to obtain the clay stabilizer. This clay stabilizer can act on negatively charged clay particles at multiple points, exhibiting high adsorption and thus achieving a high anti-swelling rate at low dosages.

[0007] CN101921366A discloses a three-branched cationic polymer synthesized from diallyl ammonium chloride and triallyl ammonium chloride for stabilizing clay during oil extraction. However, studies have shown that high molecular weight cationic polymers are unsuitable for low-permeability formations, easily forming plugs in formation pore channels and thus clogging the formation. Furthermore, due to their long molecular chains and numerous cationic groups, these polymers readily react with treatment agents containing anionic groups, significantly impacting the effectiveness of the treatment agents. Therefore, there is a need to develop clay stabilizers with relatively low molecular weight, that protect the formation from damage, and exhibit good compatibility with other treatment agents.

[0008] CN106947440A discloses a temperature- and salt-resistant anti-swelling clay stabilizer and its preparation method. The anti-swelling clay stabilizer is composed of soybean oil-modified surfactant, aminocarboxylic acid resin, ammonium sulfate, and water. Among them, the soybean oil-modified surfactant is a quaternary ammonium salt surfactant with long-chain alkyl groups and quaternary ammonium cations. The anti-swelling clay stabilizer has the characteristics of wide availability of raw materials, simple synthesis process, low dosage, and strong adaptability to oil reservoirs. At the same time, it has good temperature and salt resistance, can withstand temperatures up to 280℃, and has a salinity resistance up to 230,000 mg / L. It also has good compatibility with formation water and a high anti-swelling rate of over 98.0%.

[0009] While the above-mentioned clay anti-swelling agents have a good inhibitory effect, they also have some problems: (1) Inorganic salts are used. On the one hand, inorganic salts will increase the mineralization of formation water, which is not conducive to subsequent profile adjustment. On the other hand, inorganic salts only use their positive charge to neutralize the negative charge on the surface of clay, compress and diffuse the double electric layer, and compact the clay particles. They do not combine the clay with the formation, and cannot prevent clay migration and fix sand. (2) Small molecule quaternary ammonium salts, due to their small molecular weight, can enter the clay lamellae, but cannot effectively pull the adjacent clay particles together to keep them in a larger particle state. (3) Polymer-type large cations, due to their large molecular weight, are not suitable for low permeability formations and are prone to forming plugs in the formation pore channels, thereby blocking the formation. Therefore, by controlling the molecular weight, charge density, and functional groups contained in the molecular structure of clay stabilizers, on the one hand, the electronegativity of clay particles is reduced through their own charge density, and on the other hand, through their own molecular structure characteristics, the clay anti-swelling agent can not only enter the clay interlayer to achieve interlayer sealing, but also cover the surface of clay particles to prevent water molecules from contacting the surface of clay particles. Thus, it can prevent clay swelling and clay migration at the same time. Summary of the Invention

[0010] This invention aims to overcome the problems of existing clay stabilizers in the background art, such as small molecular weight which cannot coat clay, large molecular weight which is unsuitable for low-permeability formations, and significant impact on formation water salinity. It provides a clay stabilizer and its preparation method to solve problems such as blockage of water injection channels, reduced formation permeability, and increased water injection pressure caused by clay hydration and dispersion. The clay stabilizer provided by this invention has advantages such as moderate molecular weight, good and long-lasting anti-swelling effect, effective prevention of clay particle migration, good temperature resistance, no increase in formation water salinity, and increased formation permeability.

[0011] The present invention achieves the above objectives through the following technical solutions.

[0012] The clay stabilizer of the present invention is characterized in that the clay stabilizer has the structure shown in formula (1) or formula (2);

[0013] Formula 1;

[0014] Equation 2,

[0015] Among them, R1, R2, and R3 may be the same or different, and each is independently H, CH3, or C2H. 5、 C3H7 or NH2; n1=m1=0-3, n2=1~4; m2=1~6; a, b, c are the molar numbers of structural units of olefinic acid, acrylamide and dimethyl diallyl ammonium chloride, respectively, a:b:c=(1-3):(2-4):(5-7).

[0016] The clay stabilizer of the present invention, wherein R1, R2, and R3 are the same or different, and each is independently H, CH3, or NH2; n1=m1=0-2, n2=1~3; m2=1~5; a, b, and c are the molar numbers of structural units of olefinic acid, acrylamide, and dimethyldiallylammonium chloride, respectively, and a:b:c=(1-2):(2-3.5):(5-7).

[0017] The clay stabilizer of the present invention has a viscosity-average molecular weight of 5,000-100,000; and the content of dimethyl diallyl ammonium chloride in the clay stabilizer is 50-70 (mol%) based on the total amount of the clay stabilizer.

[0018] The method for preparing the clay stabilizer of the present invention is characterized by comprising: polymerizing an acrylate monomer, acrylamide, and dimethyl diallyl ammonium chloride in the presence of water and an initiator to obtain a low molecular weight polymer; then, using o-dichlorobenzene as a solvent, subjecting the low molecular weight polymer to an amidation reaction with ethyleneamine or alkyl diamine; and finally, separating and drying to obtain the clay stabilizer.

[0019] The method for preparing the clay stabilizer according to the present invention, wherein the acrylate monomer is selected from at least one of acrylic acid, 2-methacrylic acid, 3-amino-2-butenoic acid and 2-amino-3-butenoic acid, 4-pentenoic acid, 2-pentenoic acid, 2-hexenoic acid, 3-hexenoic acid, 4-hexenoic acid, and 5-hexenoic acid, preferably at least one of acrylic acid, 2-methacrylic acid, 3-amino-2-butenoic acid and 2-amino-3-butenoic acid, 2-pentenoic acid, and 2-hexenoic acid;

[0020] The method for preparing the clay stabilizer according to the present invention includes an initiator comprising an oxidant and a reducing agent; wherein the oxidant is selected from at least one of ammonium persulfate, potassium persulfate, and sodium persulfate, and the reducing agent is selected from at least one of sodium bisulfite, potassium sulfite, sodium thiosulfate, and potassium thiosulfate; preferably, the weight ratio of the oxidant to the reducing agent is (1.5-3.5):(1.2-1.4).

[0021] The method for preparing the clay stabilizer of the present invention, wherein in the reaction system composed of olefin monomer, acrylamide, dimethyl diallyl ammonium chloride, water and initiator, the total monomer concentration of the olefin monomer, acrylamide and dimethyl diallyl ammonium chloride is 35-45 wt%; preferably, the molar ratio of olefin monomer: acrylamide: dimethyl diallyl ammonium chloride is (1-2):(2-3.5):(5:7); preferably, the weight ratio of initiator:(olefin monomer + acrylamide + dimethyl diallyl ammonium chloride) is (3-4):100.

[0022] The method for preparing the clay stabilizer according to the present invention includes the following conditions for the polymerization reaction: temperature of 30-40℃ and time of 3-4h.

[0023] The method for preparing the clay stabilizer according to the present invention, wherein the ethyleneamine is selected from at least one of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine, preferably at least one of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine, and the alkyl diamine is selected from at least one of ethylenediamine, propylenediamine, butanediamine, pentanediamine, and hexamethylenediamine, preferably at least one of propylenediamine and hexamethylenediamine.

[0024] The preparation method of the clay stabilizer of the present invention includes the following conditions for the amidation reaction: temperature of 120-180℃ and time of 3-5h.

[0025] The benefits and features of this invention are as follows:

[0026] (1) The clay stabilizer of the present invention has a wide range of raw material sources, a simple synthesis process, and low cost;

[0027] (2) The clay stabilizer of the present invention has a moderate molecular weight and will not cause blockage in low-permeability formations;

[0028] (3) The clay stabilizer of the present invention has a large number of cationic functional groups and amine groups in its molecular structure, and has a high charge density. It can enter the clay sheet structure and can also form multi-point adsorption with clay particles. It forms an adsorption film on the surface of clay particles to prevent the expansion and migration of clay particles. It has a long effective period, high anti-swelling rate, and an anti-swelling rate of over 98% and a water washability of over 97%.

[0029] (4) The clay stabilizer of the present invention has good temperature resistance and can withstand temperatures up to 350°C. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0031] Example 1:

[0032] A four-necked flask equipped with a stirrer, thermometer, constant-pressure dropping funnel, and vent tube was placed in a constant-temperature water bath. 14.2 g of acrylamide, 173.38 g of 65% dimethyl diallyl ammonium chloride, 7.2 g of acrylic acid, 2.235 g of ammonium persulfate, and 301 g of deionized water were added and stirred until completely dissolved. The reaction system was cooled to 5°C using an ice-water bath and nitrogen gas was purged for 30 min. Then, 10 g of an aqueous solution of sodium bisulfite (containing 1.788 g of sodium bisulfite) was slowly added. After the addition was complete, nitrogen gas was purged for another 30 min. The temperature was slowly raised to 30°C, and the polymerization reaction was carried out for 5 h. After the reaction was completed and cooled, the product was dried and pulverized to obtain a low molecular weight polymer.

[0033] A four-necked flask equipped with a stirrer, thermometer, water separator, condenser, and vent pipe was placed in a constant-temperature oil bath. 200g of o-dichlorobenzene, 50g of low molecular weight polymer, 10.3g of diethylenetriamine, and 1.5g of solid acid catalyst were added. The mixture was reacted at 120℃ for 3 hours. After cooling and filtration, the filter cake was washed with ethanol and dried to obtain clay stabilizer, denoted as S1.

[0034] In S1, the molar ratio of acrylamide, dimethyl diallyl ammonium chloride, and acrylic acid is 2:7:1; based on the total amount of S1, the content of cationic groups provided by dimethyl diallyl ammonium chloride is 70 mol%; the viscosity-average molecular weight of S1 is 80,000.

[0035] Example 2:

[0036] A four-necked flask equipped with a stirrer, thermometer, constant pressure dropping funnel, and venting tube was placed in a constant temperature water bath. 14.2 g of acrylamide, 148.61 g of 65% dimethyl diallyl ammonium chloride, 17.2 g of 2-methacrylic acid, 3.65 g of ammonium persulfate, and 282 g of deionized water were added and stirred until completely dissolved. The reaction system was cooled to 5°C using an ice-water bath and nitrogen gas was purged for 30 min. Then, 10 g of an aqueous solution of potassium sulfite (containing 1.46 g of sodium bisulfite) was slowly added. After the addition was complete, nitrogen gas was purged for another 30 min. The temperature was slowly raised to 30°C, and the polymerization reaction was carried out for 3 h. After the reaction was completed and cooled, the product was dried and pulverized to obtain a low molecular weight polymer.

[0037] A four-necked flask equipped with a stirrer, thermometer, water separator, condenser, and vent pipe was placed in a constant-temperature oil bath. 200g of o-dichlorobenzene, 50g of low molecular weight polymer, 14.6g of triethylenetetramine, and 0.8g of solid acid catalyst were added. The mixture was reacted at 130℃ for 4.5h. After cooling and filtration, the filter cake was washed with ethanol and dried to obtain clay stabilizer, denoted as S2.

[0038] In S2, the molar ratio of acrylamide, dimethyl diallyl ammonium chloride, and acrylic acid is 2:6:2; based on the total amount of S2, the content of cationic groups provided by dimethyl diallyl ammonium chloride is 60 mol%; the viscosity-average molecular weight of S2 is 10000.

[0039] Example 3:

[0040] A four-necked flask equipped with a stirrer, thermometer, constant pressure dropping funnel, and venting tube was placed in a constant temperature water bath. 24.85 g of acrylamide, 111.46 g of 65% dimethyl diallyl ammonium chloride, 20.2 g of 3-amino-2-butenoic acid, 2.0 g of potassium persulfate, and 251 g of deionized water were added and stirred until completely dissolved. The reaction system was cooled to 5°C using an ice-water bath and nitrogen gas was purged for 30 min. Then, 10 g of an aqueous solution of sodium bisulfite (containing 1.5 g of sodium bisulfite) was slowly added. After the addition was complete, nitrogen gas was purged for another 30 min. The temperature was slowly raised to 30°C, and the polymerization reaction was carried out for 3 h. After the reaction was completed and cooled, the product was dried and pulverized to obtain a low molecular weight polymer.

[0041] A four-necked flask equipped with a stirrer, thermometer, water separator, condenser, and vent pipe was placed in a constant-temperature oil bath. 200g of o-dichlorobenzene, 50g of low molecular weight polymer, 18.9g of tetraethylenepentamine, and 0.5g of solid acid catalyst were added. The mixture was reacted at 180℃ for 5 hours. After cooling and filtration, the filter cake was washed with ethanol and dried to obtain clay stabilizer, denoted as S3.

[0042] In S3, the molar ratio of acrylamide 37.5g, dimethyl diallyl ammonium chloride 7.5g, and acrylic acid 5g is 3.5:4.5:2; based on the total amount of S3, the content of cationic groups provided by dimethyl diallyl ammonium chloride is 45 mol%; the viscosity-average molecular weight of S3 is 50,000.

[0043] Example 4:

[0044] A four-necked flask equipped with a stirrer, thermometer, constant pressure dropping funnel, and vent tube was placed in a constant temperature water bath. 21.3 g of acrylamide, 123.85 g of 65% dimethyl diallyl ammonium chloride, 20.2 g of 2-amino-3-butenoic acid, 2 g of sodium persulfate, and 263 g of deionized water were added and stirred until completely dissolved. The reaction system was cooled to 5°C using an ice-water bath and nitrogen gas was purged for 30 min. Then, 10 g of an aqueous solution of sodium thiosulfate (containing 1.52 g of sodium bisulfite) was slowly added. After the addition was complete, nitrogen gas was purged for another 30 min. The temperature was slowly raised to 30°C, and the polymerization reaction was carried out for 3 h. After the reaction was completed and cooled, the product was dried and pulverized to obtain a low molecular weight polymer.

[0045] A four-necked flask equipped with a stirrer, thermometer, water separator, condenser, and vent pipe was placed in a constant-temperature oil bath. 200g of o-dichlorobenzene, 50g of low molecular weight polymer, 7.4g of propylenediamine, and 1.0g of solid acid catalyst were added. The mixture was reacted at 160℃ for 4.5h. After cooling and filtration, the filter cake was washed with ethanol and dried to obtain clay stabilizer, denoted as S4.

[0046] In S4, the molar ratio of acrylamide 37.5g, dimethyl diallyl ammonium chloride 7.5g, and acrylic acid 5g is 3:5:2; based on the total amount of S4, the content of cationic groups provided by dimethyl diallyl ammonium chloride is 50 mol%; the viscosity-average molecular weight of S4 is 100,000.

[0047] Example 5:

[0048] A four-necked flask equipped with a stirrer, thermometer, constant pressure dropping funnel, and venting tube was placed in a constant temperature water bath. 24.85 g of acrylamide, 123.85 g of 65% dimethyl diallyl ammonium chloride, 15 g of 2-pentenoic acid, 3.34 g of ammonium persulfate, and 260 g of deionized water were added and stirred until completely dissolved. The reaction system was cooled to 5°C using an ice-water bath and nitrogen gas was purged for 30 min. Then, 10 g of an aqueous solution of potassium thiosulfate (containing 1.37 g of sodium bisulfite) was slowly added. After the addition was complete, nitrogen gas was purged for another 30 min. The temperature was slowly raised to 30°C, and the polymerization reaction was carried out for 3 h. After the reaction was completed and cooled, the product was dried and pulverized to obtain a low molecular weight polymer.

[0049] A four-necked flask equipped with a stirrer, thermometer, water separator, condenser, and vent pipe was placed in a constant-temperature oil bath. 200g of o-dichlorobenzene, 50g of low molecular weight polymer, 11.6g of hexamethylenediamine, and 1.0g of solid acid catalyst were added. The mixture was reacted at 150℃ for 5 hours. After cooling and filtration, the filter cake was washed with ethanol and dried to obtain clay stabilizer, denoted as S5.

[0050] In S5, the molar ratio of acrylamide 37.5g, dimethyl diallyl ammonium chloride 7.5g, and acrylic acid 5g is 3.5:5:1.5; based on the total amount of S5, the content of cationic groups provided by dimethyl diallyl ammonium chloride is 50 mol%; the viscosity-average molecular weight of S5 is 60,000.

[0051] Example 6:

[0052] A four-necked flask equipped with a stirrer, thermometer, constant-pressure dropping funnel, and venting tube was placed in a constant-temperature water bath. 14.2 g of acrylamide, 161 g of 65% dimethyl diallyl ammonium chloride, 15 g of 2-pentenoic acid, 2.41 g of ammonium persulfate, and 176 g of deionized water were added and stirred until completely dissolved. The reaction system was cooled to 5°C using an ice-water bath and nitrogen gas was purged for 30 min. Then, 10 g of an aqueous solution of sodium bisulfite (containing 1.65 g of sodium bisulfite) was slowly added. After the addition was complete, nitrogen gas was purged for another 30 min. The temperature was slowly raised to 30°C, and the polymerization reaction was carried out for 3 h. After the reaction was completed and cooled, the product was dried and pulverized to obtain a low molecular weight polymer.

[0053] A four-necked flask equipped with a stirrer, thermometer, water separator, condenser, and vent pipe was placed in a constant-temperature oil bath. 200g of o-dichlorobenzene, 50g of low molecular weight polymer, 11.6g of hexamethylenediamine, and 1.5g of solid acid catalyst were added. The mixture was reacted at 165℃ for 4 hours. After cooling and filtration, the filter cake was washed with ethanol and dried to obtain clay stabilizer, denoted as S6.

[0054] In S6, the molar ratio of acrylamide 37.5g, dimethyl diallyl ammonium chloride 7.5g, and acrylic acid 5g is 2:6.5:1.5; based on the total amount of S6, the content of cationic groups provided by dimethyl diallyl ammonium chloride is 65 mol%; the viscosity-average molecular weight of S6 is 5000.

[0055] Example 7:

[0056] A four-necked flask equipped with a stirrer, thermometer, constant pressure dropping funnel, and venting tube was placed in a constant temperature water bath. 24.85 g of acrylamide, 136.23 g of 65% dimethyl diallyl ammonium chloride, 11.4 g of 2-hexenoic acid, 3.56 g of potassium persulfate, and 272 g of deionized water were added and stirred until completely dissolved. The reaction system was cooled to 5°C using an ice-water bath and nitrogen gas was purged for 30 min. Then, 10 g of an aqueous solution of sodium bisulfite (containing 1.42 g of sodium bisulfite) was slowly added. After the addition was complete, nitrogen gas was purged for another 30 min. The temperature was slowly raised to 30°C, and the polymerization reaction was carried out for 3 h. After the reaction was completed and cooled, the product was dried and pulverized to obtain a low molecular weight polymer.

[0057] A four-necked flask equipped with a stirrer, thermometer, water separator, condenser, and vent pipe was placed in a constant-temperature oil bath. 200g of o-dichlorobenzene, 50g of low molecular weight polymer, 10.3g of diethylenetriamine, and 1.8g of solid acid catalyst were added. The mixture was reacted at 140℃ for 3.5h. After cooling and filtration, the filter cake was washed with ethanol and dried to obtain clay stabilizer, denoted as S7.

[0058] In S7, the molar ratio of acrylamide 37.5g, dimethyl diallyl ammonium chloride 7.5g, and acrylic acid 5g is 3.5:5.5:1; based on the total amount of S7, the content of cationic groups provided by dimethyl diallyl ammonium chloride is 55 mol%; the viscosity-average molecular weight of S7 is 30,000.

[0059] Example 8:

[0060] A four-necked flask equipped with a stirrer, thermometer, constant pressure dropping funnel, and vent tube was placed in a constant temperature water bath. 14.2 g of acrylamide, 173.38 g of 65% dimethyl diallyl ammonium chloride, 10.1 g of 2-amino-3-butenoic acid, 3.5 g of ammonium persulfate, and 180 g of deionized water were added and stirred until completely dissolved. The reaction system was cooled to 5°C using an ice-water bath and nitrogen gas was purged for 30 min. Then, 10 g of an aqueous solution of sodium bisulfite (containing 1.6 g of sodium bisulfite) was slowly added. After the addition was complete, nitrogen gas was purged for another 30 min. The temperature was slowly raised to 30°C, and the polymerization reaction was carried out for 3 h. After the reaction was completed and cooled, the product was dried and pulverized to obtain a low molecular weight polymer.

[0061] A four-necked flask equipped with a stirrer, thermometer, water separator, condenser, and vent pipe was placed in a constant-temperature oil bath. 200g of o-dichlorobenzene, 50g of low molecular weight polymer, 14.6g of triethylenetetramine, and g of solid acid catalyst were added. The mixture was reacted at 150℃ for 3h. After cooling and filtration, the filter cake was washed with ethanol and dried to obtain clay stabilizer, denoted as S8.

[0062] In S8, the molar ratio of acrylamide 37.5g, dimethyl diallyl ammonium chloride 7.5g, and acrylic acid 5g is 2:7:1; based on the total amount of S8, the content of cationic groups provided by dimethyl diallyl ammonium chloride is 70 mol%; the viscosity-average molecular weight of S8 is 20000.

[0063] Example 9:

[0064] A four-necked flask equipped with a stirrer, thermometer, constant pressure dropping funnel, and venting tube was placed in a constant temperature water bath. 14.2 g of acrylamide, 148.62 g of 65% dimethyl diallyl ammonium chloride, 14.4 g of acrylic acid, 3.42 g of ammonium persulfate, and 213 g of deionized water were added and stirred until completely dissolved. The reaction system was cooled to 5°C using an ice-water bath and nitrogen gas was purged for 30 min. Then, 10 g of an aqueous solution of sodium bisulfite (containing 1.51 g of sodium bisulfite) was slowly added. After the addition was complete, nitrogen gas was purged for another 30 min. The temperature was slowly raised to 30°C, and the polymerization reaction was carried out for 3 h. After the reaction was completed and cooled, the product was dried and pulverized to obtain a low molecular weight polymer.

[0065] A four-necked flask equipped with a stirrer, thermometer, water separator, condenser, and vent pipe was placed in a constant-temperature oil bath. 200g of o-dichlorobenzene, 50g of low molecular weight polymer, 7.4g of propylenediamine, and 0.5g of solid acid catalyst were added. The mixture was reacted at 180℃ for 3 hours. After cooling and filtration, the filter cake was washed with ethanol and dried to obtain clay stabilizer, denoted as S9.

[0066] In S9, the molar ratio of acrylamide 37.5g, dimethyl diallyl ammonium chloride 7.5g, and acrylic acid 5g is 2:6:2; based on the total amount of S9, the content of cationic groups provided by dimethyl diallyl ammonium chloride is 60 mol%; the viscosity-average molecular weight of S9 is 10000.

[0067] Example 10:

[0068] A four-necked flask equipped with a stirrer, thermometer, constant pressure dropping funnel, and vent tube was placed in a constant temperature water bath. 14.2 g of acrylamide, 173.38 g of 65% dimethyl diallyl ammonium chloride, 11.4 g of 2-hexenoic acid, 2.35 g of ammonium persulfate, and 237 g of deionized water were added and stirred until completely dissolved. The reaction system was cooled to 5°C using an ice-water bath and nitrogen gas was purged for 30 min. Then, 10 g of an aqueous solution of sodium bisulfite (containing 1.62 g of sodium bisulfite) was slowly added. After the addition was complete, nitrogen gas was purged for another 30 min. The temperature was slowly raised to 30°C, and the polymerization reaction was carried out for 3 h. After the reaction was completed and cooled, the product was dried and pulverized to obtain a low molecular weight polymer.

[0069] A four-necked flask equipped with a stirrer, thermometer, water separator, condenser, and vent pipe was placed in a constant-temperature oil bath. 200g of o-dichlorobenzene, 50g of low molecular weight polymer, 18.9g of tetraethylenepentamine, and 1.0g of solid acid catalyst were added. The mixture was reacted at 170℃ for 3.5h. After cooling and filtration, the filter cake was washed with ethanol and dried to obtain clay stabilizer, denoted as S10.

[0070] In S10, the molar ratio of acrylamide 37.5g, dimethyl diallyl ammonium chloride 7.5g, and acrylic acid 5g is 2:7:1; based on the total amount of S10, the content of cationic groups provided by dimethyl diallyl ammonium chloride is 70 mol%; the viscosity-average molecular weight of S10 is 40,000.

[0071] Comparative Example 1

[0072] The method of Example 1 was followed, except that the amounts of acrylamide, 65% dimethyl diallyl ammonium chloride, and acrylic acid added were 28.4 g, 74.3 g, and 21.6 g, respectively. All other conditions were the same as in Example 1. Polymer D1 was obtained.

[0073] Comparative Example 2

[0074] The method of Example 1 was followed, except that acrylamide was replaced with N,N-dimethylpropyleneamine. All other conditions were the same as in Example 1. Polymer D2 was obtained.

[0075] Comparative Example 3

[0076] The method of Example 1 was followed, except that dimethyl diallyl ammonium chloride was replaced with acryloyloxyethyl trimethyl ammonium chloride. All other conditions were the same as in Example 1. Polymer D3 was obtained.

[0077] Test case

[0078] The polymers S1-S10 and D1-D3 prepared in Examples 1-10 and Comparative Examples 1-3, as well as commercially available clay stabilizers, were tested to evaluate the anti-swelling properties, temperature resistance, erosion resistance, and impact on formation permeability of the above products.

[0079] The anti-swelling properties and temperature resistance of the clay anti-swelling agent were evaluated by room temperature anti-swelling rate and high temperature anti-swelling rate tests. The erosion resistance of the clay anti-swelling agent was evaluated by water washing resistance test. The specific test steps are as follows, and the results are shown in Table 1.

[0080] The anti-swelling rate was tested according to "SY / T5971-2016 Performance Evaluation Method of Clay Stabilizer for Water Injection". The steps were as follows: Weigh 0.5g of sodium bentonite, add it to a 10mL centrifuge tube, add deionized water to the 10mL mark, shake thoroughly, let stand at room temperature for 2 hours, put it into a centrifuge, and centrifuge at 1500r / min for 15 minutes. Read the volume V2 of sodium bentonite in water. Use the same steps, but replace water with a 2% clay anti-swelling agent aqueous solution, and measure the volume V1 of the soil after centrifugation. Use kerosene instead of water to measure the volume V0 of the soil. The calculation formula is shown in Equation 3.

[0081] (Equation 3)

[0082] In the formula: η—anti-swelling rate, %

[0083] V0—Volume of sodium bentonite in kerosene, mL;

[0084] V1—Volume of sodium bentonite in clay anti-swelling agent, mL;

[0085] V2—Volume of sodium bentonite in pure water, mL;

[0086] The steps for testing the anti-swelling rate after aging at 350℃ are as follows: Add 3.00g of sodium bentonite to 60mL of a 3% (w / v) clay anti-swelling agent solution, shake thoroughly to mix, and then place in an aging vessel; then place in a high-temperature aging furnace and age at 350±2℃ for 24h; after cooling to room temperature, transfer all the clay anti-swelling agent solution in the aging vessel to a 100mL beaker, shake thoroughly, quickly remove 10mL and add it to a centrifuge tube, place it in a centrifuge with an automatic balancing function, centrifuge at 1500r / min for 15min, and read the swelling volume V1 of the bentonite. The formula for calculating the high-temperature anti-swelling rate is shown in Equation 4.

[0087] (Equation 4)

[0088] Where: F—high temperature anti-swelling rate, %

[0089] V0—Volume of sodium bentonite in kerosene, mL;

[0090] V1—Volume of sodium bentonite in clay anti-swelling agent, mL;

[0091] V2—Volume of sodium bentonite in pure water, mL;

[0092] The test procedure for water washability is as follows: Pour out the supernatant from the centrifuge tube after the anti-swelling rate test, add deionized water to 10 mL, stir thoroughly, let stand for 2 hours, and then centrifuge at 1500 r / min for 15 min. Read the final volume V1′ of sodium bentonite in the centrifuge tube. The formula for calculating the water washability rate is shown in Equation 5.

[0093] (Equation 5)

[0094] Where: V1—the swelling volume of sodium bentonite in the aqueous solution of clay anti-swelling agent, mL;

[0095] V1′—The swelling volume of sodium bentonite after washing with water, in mL;

[0096] V2—The volume of sodium bentonite that expands in pure water, in mL.

[0097] Table 1 Performance Evaluation Results

[0098]

[0099] Using a core displacement device, the performance of clay anti-swelling agent in restoring and maintaining formation permeability was evaluated through expansion treatment and expansion prevention experiments. The evaluation methods are as follows, and the results are shown in Table 2.

[0100] Swelling control experiment: Distilled water (300℃ high-temperature steam), clay anti-swelling agent, and distilled water (300℃ high-temperature steam) were sequentially injected into the core tube after saturation with simulated formation water. The initial permeability Ko, the permeability Ki after distilled water (300℃ high-temperature steam), and the permeability K after injecting distilled water (300℃ high-temperature steam) again with anti-swelling agent were measured. The formation permeability recovery rate K / Ko was calculated.

[0101] Swelling prevention experiment: Clay anti-swelling agent and distilled water (300℃ high-temperature steam) were sequentially injected into the core tube after saturation with simulated formation water. The initial permeability Ko and the permeability Ki after injecting the anti-swelling agent and then distilled water (300℃ high-temperature steam) were measured. The formation permeability retention rate Ki / Ko was calculated.

[0102] Table 2. Effect of clay stabilizer on core permeability

[0103]

[0104] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0105] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A clay stabilizer, characterized in that, The clay stabilizer has the structure shown in formula (1) or formula (2); Equation (1); Equation (2), Wherein, R1, R2, and R3 may be the same or different, and each is independently H, CH3, C2H5, C3H7, or NH2; n1=m1=0-3, n2=1~4; m2=1~6; a, b, and c are the molar numbers of structural units of olefinic acid, dimethyl diallyl ammonium chloride, and acrylamide, respectively, and a:b:c=(1-3):(5-7):(2-4); The clay stabilizer has a viscosity-average molecular weight of 5,000-100,000; based on the total amount of the clay stabilizer, the content of dimethyl diallyl ammonium chloride is 50-70 mol.

2. The clay stabilizer according to claim 1, characterized in that... in, R1, R2, and R3 may be the same or different, and each is independently H, CH3, or NH2; n1 = m1 = 0-2, n2 = 1~3; m2 = 1~5; a, b, and c are the molar numbers of structural units of olefinic acid, dimethyl diallyl ammonium chloride, and acrylamide, respectively, and a:b:c = (1-2):(5-7):(2-3.5).

3. A method for preparing the clay stabilizer according to any one of claims 1-2, characterized in that, In the presence of water and an initiator, an olefinic monomer, acrylamide, and dimethyl diallyl ammonium chloride are polymerized to obtain a low molecular weight polymer. Then, using o-dichlorobenzene as a solvent, the low molecular weight polymer is amidated with ethyleneamine or alkyl diamine. Finally, the mixture is separated and dried to obtain a clay stabilizer.

4. The preparation method according to claim 3, characterized in that, The enoic acid monomer is selected from at least one of acrylic acid, 2-methacrylic acid, 3-amino-2-butenoic acid, 2-amino-3-butenoic acid, 4-pentenoic acid, 2-pentenoic acid, 2-hexenoic acid, 3-hexenoic acid, 4-hexenoic acid, and 5-hexenoic acid.

5. The preparation method according to claim 4, characterized in that, The acrylate monomer is selected from at least one of acrylic acid, 2-methacrylic acid, 3-amino-2-butenoic acid, 2-amino-3-butenoic acid, 2-pentenoic acid, and 2-hexenoic acid.

6. The preparation method according to claim 3, characterized in that, The initiator comprises an oxidant and a reducing agent; wherein the oxidant is selected from at least one of ammonium persulfate, potassium persulfate, and sodium persulfate, and the reducing agent is selected from at least one of sodium bisulfite, potassium sulfite, sodium thiosulfate, and potassium thiosulfate; the weight ratio of the oxidant to the reducing agent is (1.5-3.5):(1.2-1.4).

7. The preparation method according to claim 3, characterized in that, In the reaction system composed of olefin monomer, acrylamide, dimethyl diallyl ammonium chloride, water and initiator, the total monomer concentration of olefin monomer, acrylamide and dimethyl diallyl ammonium chloride is 35-45 wt%; the molar ratio of olefin monomer:acrylamide:dimethyl diallyl ammonium chloride is (1-2):(2-3.5):(5-7); the weight ratio of initiator:(olefin monomer + acrylamide + dimethyl diallyl ammonium chloride) is (3-4):

100.

8. The preparation method according to claim 3, characterized in that, The polymerization reaction conditions are: temperature 30-40℃, time 3-4h.

9. The preparation method according to claim 3, characterized in that, The ethyleneamine is selected from at least one of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine; the alkyldiamine is selected from at least one of ethylenediamine, propylenediamine, butanediamine, pentanediamine, and hexamethylenediamine.

10. The preparation method according to claim 9, characterized in that, The ethyleneamine is selected from at least one of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine; the alkyldiamine is selected from at least one of propylenediamine and hexamethylenediamine.

11. The preparation method according to claim 3, characterized in that, The conditions for the amidation reaction are: temperature 120-180℃, time 3-5h.

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