A polyionic polymer inhibitor for water-based drilling fluid and its preparation method

Abstract

The present invention provides a polymer as described in formula (II) and a preparation method thereof. The polymer provided by the present invention reduces the hydration tendency of illite, weakens the surface hydration of illite, has high strength and salt resistance, can improve the thermal stability and shear resistance of polymer molecules, improve the fluidity of polymer molecules, and weaken the self-adsorption effect of shale.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil drilling engineering, and particularly relates to an oil-based drilling fluid. More specifically, it relates to a polyionic polymer inhibitor for water-based drilling fluid and a preparation method thereof. Background Technique

[0002] As a key formation for oil and gas exploration and development, the physical and chemical properties of shale determine the complexity and technical difficulties of drilling engineering. Shale contains a large amount of clay minerals and is prone to water-sensitive changes under the action of liquid phase, resulting in unstable wellbore. The hydration of shale formation is one of the main reasons for wellbore instability during drilling. Therefore, studying the water-sensitive mechanism and control methods of shale is a core key in the field of oil and gas exploration and development. At present, although multifunctional oil-based drilling fluid can effectively inhibit the water sensitivity of shale and has advantages such as good thermal stability and lubricity, due to environmental protection restrictions, low-cost and environmentally friendly water-based drilling fluids have gradually attracted attention. Under the action of the liquid phase in the water-based working fluid, the clay minerals in shale will undergo hydration reactions, causing changes in the formation structure and strength. Under the action of water-based drilling fluid, the water-sensitive changes in shale cannot be eliminated. At present, there have been many research results on the mechanism, classification and evaluation methods of shale water-sensitive changes. Therefore, the development and design of inhibitors are the key to controlling shale water-sensitive changes. The outstanding performance of inorganic salts, organic salts, surfactants, natural product modifications and polymers in inhibiting shale hydration has been confirmed by a large number of experiments. With the continuous development of polymer drilling fluid systems, the research on polymer inhibitors has become an important topic. Among polymer shale hydration inhibitors, researchers are increasingly concerned about polyionic polymers. This strong inhibitory water-based drilling fluid system with polyionic polymers as the core treatment agent has been widely used in oilfields at home and abroad, and its performance is comparable to that of oil-based drilling fluid. With the in-depth study of related research, the structure of shale hydration inhibitors is no longer limited to linear structures. Crosslinked polymers and hyperbranched polymers play an important role in inhibiting shale hydration swelling and dispersion due to their special spatial structures. Therefore, the design and research of inhibitors must be closely combined with actual engineering needs. Having the ability to inhibit surface hydration and certain salt and temperature resistance has gradually become the current research trend of polymer inhibitors.

[0003] The excellent performance of the inhibitor is closely related to its structural characteristics. To improve the inhibition efficiency of polymer inhibitors, the inhibitor molecules can be endowed with multifunctionality during the synthesis design stage. Based on the clear understanding of the shale hydration behavior characteristics and its hydration mechanism, combined with the current situation and characteristics of existing polymer shale inhibitors, this patent starts from the perspective of configuration and monomer design to improve the structural utilization rate of polymer inhibitors. The inhibitor should have multifunctionality, so as to effectively inhibit the hydration behavior of illite according to its hydration characteristics, and at the same time should also meet the temperature resistance. Based on the research hotspots in the field of polyionic polymer materials, this patent has successfully developed a brand-new polyionic polymer inhibitor. This inhibitor combines inhibition and multifunctionality, which not only enriches the types of inhibitors, but also expands the application scope of polymers and polyionic materials in oilfield chemistry. In addition, from a chemical perspective, the structural optimization, physical and chemical property determination methods and action principles of the inhibitor provide reference and guidance for the development of other inhibitors with strong inhibition and multifunctionality. Summary of the Invention

[0004] 1 Structural Design of Polyionic Polymer Inhibitor

[0005] 1.1 Structural Advantages of the Inhibitor

[0006] Shale polymer inhibitor is an important treatment agent used in water-based drilling fluids to inhibit reactive clays and sensitive shales. It can improve wellbore stability, reduce the risk of mud packing, and improve the fluidity and salt and calcium resistance of drilling fluids. However, currently, conventional shale polymer inhibitor molecules have poor stability and fluidity, cannot effectively inhibit shale hydration and swelling, and at the same time, the energy density and reactivity of reaction monomers during the reaction process are insufficient, resulting in inefficient polymerization reactions and difficulty in meeting the drilling requirements under complex formation conditions such as high temperature, high pressure, and high salinity. To solve these problems, this patent has optimized the design of the inhibitor from the following aspects:

[0007] (1) The process of introducing cationic groups onto the polymer molecular chain is called cationization. Cationized polymers have strong cation exchange capabilities, can undergo electrostatic adsorption with the negative charges on the surface of illite, and can also neutralize some of the negative charges on the surface of illite, reducing the hydration tendency of illite.

[0008] (2) The process of introducing strongly hydrated groups onto the polymer molecular chain is called hydration modification. Hydration-modified polymers have strong water solubility and water affinity. When the polymer strongly adsorbs on the surface of illite, since the polymer molecules' ability to bind water is stronger than that of illite to bind water, it can, to a certain extent, prevent water molecules from contacting the surface of illite, thereby weakening the surface hydration of illite.

[0009] (3) The process of introducing cyclic groups or long-chain groups into the side chains of polymer molecules is called structural modification. Structurally modified polymers have higher strength and salt resistance, can improve the thermal stability and shear resistance of polymer molecules, enhance the fluidity of polymer molecules, and weaken the self-adsorption effect of shale.

[0010] (4) In addition, the reaction monomers should have high energy density and high reactivity to ensure the smooth progress of the polymerization reaction; at the same time, the monomer viscosity should not be too high, stable at room temperature and not polymerize spontaneously to ensure a controllable and stable processing window in the process. Among them, the energy density of acrylamide is 71.08 kJ / mol, which is higher than that of ethylene (52.4 kJ / mol) and acrylonitrile (59.2 kJ / mol). The reactivity of acrylamide is mainly manifested in its two reaction centers, the double bond and the amide group, and it can undergo various reactions such as addition, reduction, hydrolysis, and polymerization. The viscosity of acrylamide is not high, about 0.5 mPa·s at room temperature. In addition, after acrylamide participates in the polymerization reaction, it can increase the polarity and hydrophilicity of the copolymer, as well as increase the crosslinking points and branching degree of the copolymer, thereby enhancing its network structure and endowing it with certain shear resistance and stability.

[0011] 1.2 Monomer Structure Advantages

[0012] This patent selects free radical solution polymerization as the polymerization method, and the structural design of its monomers is very important. In order to carry out the chain growth reaction of free radical solution polymerization, primary radicals need to be formed by initiators, so the monomers contain double bonds that are easily added by primary radicals to provide the reactants required for chain growth. In addition, in order to meet the requirements of the polymer for inhibitory functional groups, the monomers should contain inhibitory functional groups and also have an appropriate number of chemical groups, so as to endow the monomers with multifunctionality to achieve more chemical reactions. Based on the above principles, 1-vinylimidazole is finally selected as the reaction raw material and reacted with N-(2-bromoethyl)-1,3-propanediamine dihydrobromide to prepare a multifunctional monomer YX-NH2. YX-NH2 is an ionic liquid monomer, and its structure contains a double bond, a cationic imidazole ring and a primary amine group. Its chemical formula is as Figure 1As shown in the figure. Among them, the cationic imidazole ring has a conjugated structure and a cationic group. The conjugated structure, like the benzene ring, has high chemical stability and thermal stability. To enhance the polarity and solubility of the YX-NH2 monomer, a cationic group is introduced, making it soluble in water and capable of exerting an inhibitory effect. In addition, the primary amino group is also beneficial to improving the inhibition of the YX-NH2 monomer and is usually used as an inhibitory functional group in water-based drilling fluid inhibitors. Therefore, this patent designs a multifunctional monomer YX-NH2, which combines two inhibitory functional groups, the cationic group and the primary amino group, to ensure its water solubility, chemical stability, and temperature resistance. The free radical polymerization monomer containing dual inhibitory functional groups designed in this patent is not common in the existing polymer inhibitors prepared by homopolymerization or copolymerization. Different from the monomers in the copolymerization system that are only responsible for a certain functionality, the structural characteristics of the YX-NH2 monomer enable it to provide strong inhibition and multifunctionality to the polymer through its own copolymerization.

[0013]

[0014] 1.3 Selection of initiator

[0015] In free radical polymerization, initiators are a class of compounds that are easily decomposed into primary free radicals by factors such as heat. They can initiate the polymerization reaction, causing monomer molecules containing double bonds to undergo addition with the primary free radicals to form monomer free radicals, and then continue to add with other monomer molecules to form polymer chains. The molecular weight of the polymer increases as the chain grows. Therefore, to control the molecular weight and molecular weight distribution of the polymer, a suitable initiator should usually be selected. Free radical initiators are a commonly used type, and their types include azo initiators, peroxide initiators, and redox systems. When selecting an initiator, it is necessary to consider the differences in monomers, solvents, and polymerization methods.

[0016] Azo initiators are a class of compounds containing N=N bonds. They can homolytically cleave into two free radicals at a certain temperature. For example, azobisisobutyronitrile (AIBN) is the most commonly used azo initiator. It decomposes at 45°C - 80°C to produce 2-cyanopropyl free radicals. Its initiation reaction belongs to a first-order reaction, has no induction period, and has a high initiation efficiency. However, its decomposition products contain cyanide and have certain toxicity. While azobis(2-methylpropionamidine) dihydrochloride (V-50) does not produce cyanide after decomposition, is safe and environmentally friendly, and is suitable for the polymerization of water-soluble monomers.

[0017] Peroxide initiators are a class of compounds containing O-O bonds. They can homolytically cleave into two free radicals at a certain temperature. Among water-soluble peroxide initiators, persulfates are a commonly used initiator, suitable for emulsion polymerization and aqueous solution polymerization. During the decomposition process, free ions or ion free radicals are generated, and usually a temperature higher than 60°C is required to initiate the decomposition reaction.

[0018] The redox system is a free radical initiation system composed of an oxidizing agent and a reducing agent. They have a low decomposition activation energy and can induce the polymerization reaction of vinyl monomers under low-temperature conditions. The components of such systems can be inorganic or organic substances, and can be in the aqueous phase or the oil phase, depending on the specific situation. Common water-soluble redox initiation systems use peroxides, persulfates, hydrogen peroxide, etc. as the oxidizing agent components and inorganic or organic substances as the reducing agent components. After being combined with ferrous ions, their decomposition activation energy is greatly reduced, and they can still have a high initiation ability when inducing the polymerization reaction at 5°C.

[0019] Based on the monomer structure, YX-NH2 has hydrophilic side groups of cations and anions, namely amino groups, with relatively strong polarity. To ensure the solubility of the monomer during solution polymerization, deionized water should be selected as the solvent during solution polymerization, as its polarity is relatively weak. In addition, azobisisobutyramidine hydrochloride can be used as an initiator compatible with YX-NH2. The V-50 initiator has a more stable, steady and controllable decomposition reaction compared with water-soluble initiators, can initiate the reaction more efficiently and reduce the generation of residues. Compared with oil-soluble azobisisobutyronitrile, the V-50 initiator has greater advantages. Due to its water solubility, it can be used for the polymerization of water-soluble monomers. In addition, the decomposition products generated by the V-50 initiator do not contain toxic cyano groups, so it has the characteristics of safety, greenness and environmental protection.

[0020]

[0021] Specific invention content:

[0022] On the one hand, the present invention provides a compound of formula (I):

[0023]

[0024] On the other hand, the present invention provides a polymer of formula (II), wherein the polymer:

[0025]

[0026] wherein, the mass percentage of x is 55% - 73%, and the mass percentage of y is 30% - 45%.

[0027] Furthermore, for the polymer of formula (II) provided by the present invention, the mass percentage of x is 62.5%, and the mass percentage of y is 37.5%.

[0028] The present invention also provides a method for synthesizing the polymer of formula (II), which is characterized in that it is obtained by reacting the compound of formula (I) with acrylamide and an initiator in water:

[0029]

[0030] Further, the synthesis method of the polymer of formula (II) of the present invention is characterized in that the initiator is an azo initiator, a peroxide initiator or a redox system, wherein the azo initiator is selected from azodiisobutyronitrile; the peroxide initiator is selected from persulfates; the redox system is selected from hydrogen peroxide, potassium persulfate, cumene hydroperoxide; preferably, the initiator is azodiamidinopropane hydrochloride.

[0031] Further, the method of the present invention is characterized in that the reaction temperature is 45-70 °C, preferably 60 °C.

[0032] Further, the method of the present invention is characterized in that the molar ratio of the compound of formula (I) to acrylamide is 10-15:35-40, preferably 13:38.

[0033] The present invention also provides a synthesis method of formula (I), which is characterized in that 1-vinylimidazole reacts with N-(2-bromoethyl)-1,3-propanediamine dihydrobromide in an organic solvent to obtain formula (I).

[0034] Further, the synthesis method of the compound of formula (I) provided by the present invention is characterized in that the organic solvent is acetonitrile, the reaction temperature is 70-90 °C, preferably 80 °C; the molar ratio of 1-vinylimidazole to N-(2-bromoethyl)-1,3-propanediamine dihydrobromide is between 1.5:1 and 0.5:1; preferably 1:1.

[0035] The present invention also provides a synthesis method of the polymer of formula (II), and the synthesis step of the compound of formula (I) described above is further included.

[0036] The present invention also provides the use of the polymer of formula (II) in water-based drilling fluids.

[0037] The present invention also provides an inhibitor solution composition containing the polymer of formula (II).

[0038] Further, the composition provided by the present invention is characterized in that it contains 1.2% of the polymer.

[0039] Description of the drawings:

[0040] Figure 1 : 3D structure of YX-NH2

[0041] Figure 2 : Infrared spectra of YX-NH2 and TIL-NH2

[0042] Figure 3 : of TIL-NH2 1 1H-NMR spectrum

[0043] Figure 4: Thermogravimetric curve of TIL-NH2

[0044] Figure 5 : Linear expansion height of shale powder under different inhibitors

[0045] Figure 6 : Variation of thermal rolling recovery rate with the dosage of TIL-NH2 at different temperatures

[0046] Figure 7 : Thermal rolling recovery rate of each inhibitor at 120 °C

[0047] Specific factual manner:

[0048] Example 1: Synthesis and characterization of polyionic polymer inhibitor

[0049] 1. Synthesis of YX-NH2 ionic liquid monomer

[0050] Add 12.3 g (0.15 mol) (the range can be 0.1 - 0.3 mol) of 1-vinylimidazole to 70 mL of acetonitrile solvent, pour the mixed solution into a three-necked flask equipped with a reflux condenser, and wait for standby. Raise the temperature of the system to 80 °C (the temperature range can be 70 - 90 °C), and add 25.6 g (0.15 mol) (the range can be 0.1 - 0.3 mol) of N-(2-bromoethyl)-1,3-propanediamine dihydrobromide. The reaction mixture is stirred and refluxed at 80 °C (the temperature range can be 70 - 90 °C, with a temperature gradient of 2 °C) for 24 hours (the stirring and refluxing range can be 20 - 30 hours, with a time gradient of 1 hour). After the reaction is completed, remove HBr in the reactant with triethylamine to make the two react to form triethylamine hydrochloride, then perform suction filtration. Wash the obtained precipitate with anhydrous ethanol multiple times, and finally dry the precipitate in a vacuum drying oven at 45 °C for 24 hours to obtain a light orange solid product, which is the prepared monomer (YX-NH2), with a yield of 84.2%.

[0051] 2. Synthesis of polyionic polymer TIL-NH2

[0052] Dissolve 6.5 g of YX-NH2 monomer and 5.5 g of acrylamide in deionized water, and place them in a three-necked flask equipped with a reflux condenser. Then adjust the pH to 5 (the pH range can be 4.8 - 6, and the pH gradient is 0.1), and heat it to 60 °C under reflux condensation. Add 7 g (0.75% of the total addition amount of YX-NH2 monomer and acrylamide, the addition amount range is 0.5% - 1%, and the addition amount gradient is 0.05%) of V-50 initiator under a nitrogen protection environment. Subsequently, carry out the polymerization reaction under stirring conditions of 200 r / min (the stirring speed range can be 100 - 300 r / min, and the stirring speed gradient is 50 r / min) and maintain a constant temperature for several hours. After the reaction is completed, transfer the mixture to a rotary evaporator for vacuum distillation for 2.5 hours (the vacuum distillation time range can be 2 - 3 hours, and the time gradient is 0.1 hour). Subsequently, an orange-red viscous solid product, namely polyionic polymer TIL-NH2, can be obtained.

[0053] Synthesis route of TIL-NH2.

[0054]

[0055] Among them where the mass percentage of x is 55% - 73% and the mass percentage of y is 30% - 45%.

[0056] 3. Structural characterization of polyionic polymer inhibitor

[0057] 3.1 Fourier transform infrared spectroscopy analysis

[0058] Among them, the broad band at 3424 cm -1 is the fundamental frequency peak of the stretching vibration of the N-H bond of the primary amine functional group, and the peak at 3075 cm -1 is the fundamental frequency peak of the stretching vibration of the C-H bond of the imidazole ring. The peaks at 2995 cm -1 and 2940 cm -1 are the fundamental frequency peaks of the stretching vibrations of the C-H bonds of the methyl and methylene groups in the side chain. The peak at 1640 cm -1 is the fundamental frequency peak of the stretching vibration of the C = C bond of the vinyl group. The peak at 1558 cm -1 is the fundamental frequency peak of the stretching vibration of the N = C bond of the cationic imidazole ring. The peak at 1319 cm -1 is the fundamental frequency peak of the skeletal vibration of the imidazole ring. The peak at 1142 cm -1 is the fundamental frequency peak of the in-plane bending vibration of the C-H bond of the imidazole ring. The peak at 958 cm -1 is the fundamental frequency peak of the stretching vibration of the imidazole ring, and the peak at 934 cm -1The peak at [[]] is the fundamental frequency peak of the in-plane rocking vibration of the C-H bond of the propenyl group. These spectral characteristics indicate that the YX-NH2 monomer has a primary amine functional group, a cationic imidazole five-membered ring structure, and a vinyl structure. In the infrared spectrum of the TIL-NH2 polymer, in addition to the spectral characteristics of the primary amine functional group and the cationic imidazole five-membered ring remaining unchanged, a new peak appears at 1678 cm -1 The peak at [[]] is the fundamental frequency peak of the stretching vibration of the carbonyl C=O in the amide group -CONH2, and the spectral characteristics of the C=C bond of the vinyl group at 1640 cm -1 and the C-H bond at 934 cm -1 disappear, indicating that the double bond of the vinyl group opens to form a long-chain polymer structure. Figure 2 Infrared spectra of YX-NH2 and TIL-NH2

[0059] 3.2 Nuclear magnetic resonance spectroscopy analysis

[0060] In the 1 1H-NMR spectrum of TIL-NH2, the chemical shift of the hydrogen atoms of -CH2- on the main chain of the polymer molecule is 1.57 - 1.68 (a) ppm; the chemical shift of the hydrogen atoms of -CH- in the acrylamide structural unit on the main chain of the polymer molecule is 2.24 (b) ppm, and the chemical shift of the atoms of -CH- on the imidazole ring of the polymer side chain is attributed to 6.87 - 6.91 (c, d, e) ppm. The chemical shift at 2.48 - 2.57 (f) ppm comes from the hydrogen atoms in the secondary amine, and the chemical shift at 1.80 - 1.84 (g) ppm comes from the hydrogen atoms in the primary amine. The 1 1H-NMR spectrum of TIL-NH2 is as Figure 3 shown.

[0061] 3.3 Thermal stability analysis

[0062] According to Figure 4 the experimental data, the thermal analysis curve of TIL-NH2 can be divided into three temperature ranges for discussion, namely 45°C - 165°C, 165°C - 300°C, and 300°C - 500°C.

[0063] (1) Temperature range: 45°C - 165°C

[0064] The sample begins to show mass loss at about 45°C until the mass loss curve flattens at 165°C. In this region, the mass loss rate of TIL-NH2 is about 27.11%. The DTG curve shows that the mass loss rate of the sample TIL-NH2 reaches a peak at about 100°C, which is consistent with the boiling point of water.

[0065] (2) Temperature region: 165°C - 300°C

[0066] Starting from 165°C, the TG curve of the polymer TIL-NH2 remains basically unchanged until almost no mass change occurs before 300°C. In this region, the DTG curve is also an approximately horizontal straight line, and the mass change rate is always lower than -0.001 mg / s. This indicates that there is no structural breakage phenomenon in the polymer TIL-NH2 in this temperature region, and it can maintain chemical structure stability.

[0067] (3) Temperature region: 300°C to 500°C

[0068] After being affected by high temperature, the molecular chains of TIL-NH2 begin to undergo thermal dissociation, resulting in a sharp decrease in its mass and a rapid increase in the mass loss rate. When the temperature reaches 365°C, the mass loss rate of the TIL-NH2 molecular chains reaches the maximum value, approximately -0.026 mg / s, indicating that its thermal dissociation is the most severe. As the temperature continues to rise, the thermal dissociation of TIL-NH2 tends to end. When the temperature rises to 500°C, only 12.76% of the residual mass of TIL-NH2 remains.

[0069] Example 2: Performance evaluation of polyionic polymer inhibitors

[0070] 1. Linear expansion experiment

[0071] The linear expansion rate of shale powder was tested using different types of inhibitor solutions (5% KCl, 2% NW-1, 2% polyetheramine solution, and 1.2% TIL-NH2). As Figure 5 shown.

[0072] Compared with the clear water group, all inhibitor aqueous solutions can effectively reduce the hydration expansion height of shale powder. Compared with the 16-hour expansion height of 4.43 mm in the clear water group, the 16-hour expansion heights of the KCl and NW-1 groups are 2.44 mm and 2.68 mm respectively, indicating that they have similar inhibitory effects. In the early expansion stage, the expansion height of the 2% polyetheramine group is slightly lower than that of the 2% polyamine DEM group, but after 16 hours, the expansion height difference between these two groups is not obvious. In the linear expansion experiment, the best inhibitor is

[0073] the 1.2% TIL-NH2 group, whose expansion rate within 16 hours is lower than that of other inhibitor groups, and the expansion height at 16 hours is only 1.52 mm, showing an obvious inhibitory effect.

[0074] 2. Cuttings rolling recovery experiment

[0075] Under laboratory-simulated high-temperature conditions, the inhibition performance of TIL-NH2 was evaluated using the thermal rolling recovery rate.

[0076] Compared with the fresh water group, the addition of TIL-NH2 significantly inhibited the hydration dispersion of shale, thus improving the hot-rolling recovery rate. TIL-NH2 can achieve a high recovery rate at a relatively low concentration. When the concentration exceeds 0.9%, the recovery rates at various temperatures are all above 75%; when the concentration is 1.2%, the hot-rolling recovery rates within the range of 120-180 °C all exceed 82%. This may be because TIL-NH2 contains two inhibitory functional groups, and the double inhibitory functional groups enhance the adsorption and coating ability of TIL-NH2 and prevent the hydration dispersion of shale. The side chain of TIL-NH2 contains an imidazole cationic structure. Even at a temperature as high as 300 °C, this compound does not decompose significantly, so it can maintain the structural stability and play an inhibitory role, resulting in a slow decrease in the hot-rolling recovery rate. Even under the condition of the highest temperature of 200 °C, the 0.9% concentration of TIL-NH2 compound still has a good performance in terms of the hot-rolling recovery rate, which is 75.26%. The good high-temperature resistance of TIL-NH2 endows it with certain application potential. Figure 6 The results shown.

[0077] Figure 7 The hot-rolling recovery rates of shale at 120 °C with different inhibitors were compared, where the concentration of TIL-NH2 was 1.2%. Compared with the fresh water group, the inhibitory effects of various inhibitors on the hydration dispersion of cuttings were different. Compared with the small molecule salt KCl and NW-1, polyamine inhibitors DEM, polyetheramine and TIL-NH2 can effectively prevent the dispersion of cuttings due to the coating and adsorption effects of their molecular chains. Among them, 2% polyetheramine can increase the hot-rolling recovery rate of shale from 60.37% in fresh water to 76.80%. The polyamine inhibitor DEM can effectively adsorb and coat cuttings and inhibit their hydration dispersion due to its hyperbranched structure and the content of polyamine functional groups, thus achieving a high hot-rolling recovery rate. Compared with polyamine inhibitors such as DEM and polyetheramine, TIL-NH2 has a higher molecular weight and double inhibitory functional groups, which enhances its adsorption and coating ability and makes the recovery rate at a concentration of 1.2% reach 88.12%.

[0078] 3 Influence of inhibitors on the acoustic time difference of shale core

[0079] Taking the Longmaxi Formation shale in the Weiyuan area as an example, the effects of soaking standard shale core samples with different types and concentrations of inorganic salts, different types and concentrations of inhibitors and distilled water were experimentally studied. The types of inorganic salts were KCl, NaCl, and CaCl2 solutions, and the inhibitors were polyamine DEM, polyetheramine and TIL-NH2, with concentrations of 0.3 mol / L, 0.6 mol / L and 1.2 mol / L respectively. The test results are shown in Table 1. The mass fractions of 1.2 mol / L NaCl, KCl and CaCl2 solutions are 8.05%, 10.23% and 13.25% respectively.

[0080] Table 1 Acoustic travel time of Longmaxi shale core samples before and after soaking

[0081]

[0082] By horizontally comparing the data in the table, it is found that with the increase in the concentration of the added liquid phase, the increment of acoustic travel time △tc shows a decreasing trend; by vertically comparing the data changes in the table, it can be found that the △tc value of the core samples added with inhibitor solution is generally smaller than that after adding inorganic salt solution. Among the inorganic salts, the data of KCl and CaCl2 are smaller than that of NaCl, indicating that the inhibitory effect of KCl and CaCl2 solutions is better. In the inhibitor solution, the △tc value after adding TIL-NH2 is smaller than that of polyamine DEM and polyetheramine. The order of the ability to inhibit shale hydration is TIL-NH2 > polyetheramine > DEM. This is because the imidazole cation structure in the TIL-NH2 itself and the primary amine functional group at the end of the side chain are strongly adsorbed on the clay particles, hindering the adsorption of water molecules to the clay particles, thus having an efficient inhibitory effect on shale.

Claims

1. A compound of formula (I):

2. A polymer of formula (II), the polymer: Among them, The mass percentage of x is 62.5%, and the mass percentage of y is 37.5%.

3. A method for synthesizing the polymer of formula (II) according to claim 2, characterized in that Obtained by reacting the compound of formula (I) with acrylamide and an initiator in water, the initiator being azobisisobutyramidine hydrochloride; wherein the reaction temperature is 45 - 70 °C; the molar ratio of the compound of formula (I) to acrylamide is 10 - 15:35 - 40, 4. The synthesis method according to claim 3, characterized in that The molar ratio of the compound of formula (I) to acrylamide is 13:

38.

5. A method for synthesizing the compound of formula (I) according to claim 1, characterized in that Formula (I) is obtained by reacting 1-vinylimidazole with N-(2-bromoethyl)-1,3-propanediamine dihydrobromide in an organic solvent, the organic solvent being acetonitrile, the reaction temperature being 70 - 90 °C, and the molar ratio of 1-vinylimidazole to N-(2-bromoethyl)-1,3-propanediamine dihydrobromide being 1.5:1 - 0.5:

1.

6. The method according to claim 5, wherein The molar ratio of 1-vinylimidazole to N-(2-bromoethyl)-1,3-propanediamine dihydrobromide is 1:

1.

7. The method for synthesizing the polymer of formula (II) according to claim 3, the steps of which further include the steps of any one of claims 5 - 6.

8. Use of the polymer of formula (II) according to claim 2 in a water-based drilling fluid.

9. An inhibitor solution composition containing the polymer of formula (II) according to claim 2.

10. The solution composition according to claim 9, characterized in that Contains 1.2% of the polymer.

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