Clay mineral surface hydration inhibitor and method of making same

Abstract

The present application relates to the technical field of drilling fluid for oil drilling, and particularly relates to a clay mineral surface hydration inhibitor and a preparation method thereof, and a structural formula of the clay mineral surface hydration inhibitor is shown as follows: The present application provides a preparation method of a clay mineral surface hydration inhibitor, and the method comprises the following steps: A, Boc-beta-alanine solution is prepared, and an activating agent, a condensing agent and a catalyst are added under ice water bath condition, stirring reaction is carried out, then diethylenetriamine is added, the obtained solid after reaction is filtered, purification is carried out, and the obtained solid is filtered and dried again to obtain a solid intermediate product; B, the solid intermediate product obtained in step A is ground into powder; C, hydrochloric acid / 1,4 dioxane and an organic solvent are mixed to prepare a solution, then the solution is mixed with the powder ground in step B, and stirring reaction is carried out in a sealed state, and the obtained filter residue after treatment of the reaction solution is filtered, and the filter residue is the clay mineral surface hydration inhibitor, which can effectively inhibit the hydration of the surface of the clay mineral.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of drilling fluid for oil drilling, and particularly relates to a clay mineral surface hydration inhibitor and a preparation method thereof. BACKGROUND

[0002] In recent years, unconventional oil and gas resources are widely used in the world, and unconventional oil and gas resources including shale gas have become a current research hotspot.

[0003] Shale gas has advantages of wide distribution, large reserves, stable yield, clean and low carbon, and is a kind of unconventional oil and gas resource discovered first in the world. In the process of shale gas exploration and development, clay minerals in the formation will be hydrated and dispersed. According to the hydration mechanism, the hydration of clay minerals can be divided into surface hydration and penetration hydration. The existing inhibitor can well inhibit the penetration hydration, but it is difficult to inhibit the surface hydration. SUMMARY

[0004] In order to solve the above technical problems, the embodiments of the present application provide a clay mineral surface hydration inhibitor and a preparation method thereof.

[0005] To achieve the above object, the embodiments of the present application adopt the following technical solutions:

[0006] On the one hand, the present application provides a clay mineral surface hydration inhibitor, and the structural formula of the clay mineral surface hydration inhibitor is as follows:

[0007]

[0008] On the other hand, the present application provides a preparation method of the clay mineral surface hydration inhibitor, comprising the following steps:

[0009] A, a Boc-beta-alanine solution is prepared, and an activating agent, a condensing agent and a catalyst are added under the condition of ice water bath, and then stirred and reacted, diethylene triamine is added, and after reaction, the obtained solid is filtered, purified, and then filtered and dried to obtain a solid intermediate product;

[0010] B, the solid intermediate product obtained in step A is ground into powder;

[0011] C, hydrochloric acid / 1,4 dioxane and an organic solvent are mixed to form a solution, and then mixed with the powder ground in step B, and then sealed and stirred to react, and after reaction, the treatment liquid is filtered to obtain filter residue, which is the clay mineral surface hydration inhibitor.

[0012] In some embodiments, in step A, the molar concentration of the Boc-beta-alanine solution is 0.15 mol / L.

[0013] In some embodiments, in step A, the temperature of the ice water bath is controlled at 0-5℃, the temperature of the stirring reaction is 25℃, and the reaction time is 0.5h.

[0014] In some embodiments, in step A, the drying temperature is 80℃, and the drying time is 8h.

[0015] In some embodiments, in step A, the molar ratio of Boc-β-alanine, activating agent, condensing agent and catalyst is 3:3:3:5, and the molar ratio of Boc-β-alanine and diethylenetriamine is 2:1.

[0016] In some embodiments, the activating agent is 1-hydroxybenzotriazole, the condensing agent is 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and the catalyst is triethylamine.

[0017] In some embodiments, in step C, the reaction temperature is 25℃, and the reaction time is 12h.

[0018] In some embodiments, in step C, the volume ratio of hydrochloric acid / 1,4 dioxane and organic solvent is 1:2, the volume ratio of hydrochloric acid and 1,4 dioxane is 1:1, and the organic solvent is dichloromethane.

[0019] The present application evaluates the inhibition performance of the inhibitor by using linear expansion experiment, shale rolling recovery experiment, X-ray diffraction method, isothermal adsorption method and thermogravimetric analysis method. The results are as follows: (1) the linear expansion experiment results show that NPT (i.e. clay mineral surface hydration inhibitor) can effectively inhibit the hydration expansion of shale; (2) the shale rolling recovery experiment shows that NPT has the ability to inhibit the hydration dispersion of shale; (3) through the isothermal adsorption experiment, it is obtained that the unit adsorption water amount of sodium montmorillonite after adding NPT is far less than that of pure sodium montmorillonite; (4) the X-ray diffraction experiment results show that when the NPT addition amount is 0.5wt%, the basal spacing of hydrated sodium montmorillonite can be reduced from 1.90nm to 1.30nm, indicating that the synthesized compound can be inserted into the interlayer of clay minerals, and has good inhibition performance; (5) the TG curve in the thermogravimetric analysis curve is ladder-shaped, and the DTG curve only has a single peak, indicating that the synthesized NPT inhibitor can effectively inhibit the interlayer surface hydration and cation hydration of sodium montmorillonite. In summary, the research shows that the synthesized NPT inhibitor can effectively inhibit the hydration of the surface of clay minerals. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is the infrared spectrum analysis diagram of the intermediate product in the present application;

[0021] Figure 2 It is the infrared spectrum analysis diagram of NPT in the present application;

[0022] Figure 3 Mass spectrum of the intermediate product in the application;

[0023] Figure 4 Mass spectrum of the NPT in the application;

[0024] Figure 5 NMR hydrogen spectrum of the NPT in the application;

[0025] Figure 6 Linear expansion test diagram of the inhibitor in the application;

[0026] Figure 7 Shale rolling recovery rate analysis diagram of the application;

[0027] Figure 8 Unit adsorbed water amount analysis diagram of the pure sodium montmorillonite and the sodium montmorillonite after adding the inhibitor in the application;

[0028] Figure 9 Change diagram of the basal spacing of the dry-state sodium montmorillonite substrate after adding the inhibitor in the application;

[0029] Figure 10 Change diagram of the basal spacing of the wet-state sodium montmorillonite substrate after adding the inhibitor in the application;

[0030] Figure 11 TG curve diagram of the sodium montmorillonite after modification of the inhibitor in the application;

[0031] Figure 12 DTG curve diagram of the sodium montmorillonite after modification of the inhibitor in the application;

[0032] Figure 13 D2TG curve diagram of the sodium montmorillonite after modification of the inhibitor in the application. DETAILED DESCRIPTION

[0033] The technical solutions in some embodiments of the present disclosure will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments provided in the present disclosure, all other embodiments obtained by those skilled in the art belong to the scope of protection of the present disclosure.

[0034] EMBODIMENT

[0035] In the embodiment of the present application, Boc-β-alanine and diethylenetriamine are subjected to amidation reaction under the action of condensing agent, activating agent, catalyst and the like, and finally the clay mineral surface hydration inhibitor (NPT) is obtained. Diethylenetriamine is a chain structure, and contains primary amine and secondary amine. The steric hindrance of the secondary amine is greater than that of the primary amine, so the activity of the secondary amine is low in the reaction process, and the carboxylic acid preferentially reacts with the primary amine. The reaction equation is shown as follows:

[0036]

[0037] The main experimental reagents and experimental apparatus required for the synthesis of clay mineral surface hydration inhibitor (NPT) are shown in Table 1 and Table 2:

[0038] Table 1

[0039]

[0040] Table 2

[0041] Instrument equipment Instrument model Manufacturer Electronic balance with one ten-thousandth ME204T / 02 Mettler-toledo instrument co., LTD Heat constant temperature magnetic stirrer DF-101S Yuhua instrument co., LTD Vacuum drying oven DZF-6020A Beijing zhongxingweiye century instrument co., LTD Circulating water type multi-purpose vacuum pump SHB-Ⅲ Changsha Mingjie instrument co., LTD Multiple magnetic stirrer MMS6Pro Qunan experimental instrument co., LTD

[0042] 1. Synthesis of clay mineral surface hydration inhibitor (NPT) intermediate product, comprising the following steps:

[0043] (1) Dissolve Boc-β-alanine (5.7 g, 30 mmol) in dichloromethane (200 mL), and add HOBT (4.05 g, 30 mmol), EDCI (5.73 g, 30 mmol), and triethylamine (3 g, 50 mmol) under ice water bath (temperature controlled at 0°C, 1°C, 2°C, 3°C, 4°C, or 5°C), and stir the reaction for half an hour to allow the reaction to proceed fully;

[0044] (2) Add diethylenetriamine (1.55 g, 15 mmol), and transfer to room temperature (25°C), and react for 12 h;

[0045] (3) Filter and detect whether new substances are generated. Spot the filtrate on a thin layer chromatography (TLC) plate, and observe whether new spots are generated. The operation is as follows: add developing solution (CH2Cl2:CH3OH = 4:1) in a developing tank, and spot EDCI, HOBT, Boc-β-alanine, diethylenetriamine, and the filtrate in order on a silica gel plate using a capillary tube, so that each sample point is parallel to the bottom edge. After spotting is completed, immerse the silica gel plate in developing solution in the developing tank for 3 min, and then use a hair dryer to dry the solvent as much as possible. The appearance of a clean new spot above the sample point of the filtrate on the silica gel chromatography plate indicates the generation of new substances;

[0046] (4) Purification: purify the solid obtained by filtration, as follows: wash the solid with dichloromethane, and then wash with pure water;

[0047] (5) Filter the solid again;

[0048] (6) Drying: place the solid in an 80°C vacuum drying oven for 8 h, take it out, and place it in a centrifuge tube for sampling. The obtained intermediate product weighs 4.32 g.

[0049] The above reaction steps generate an intermediate product bearing a Boc protecting group. The synthesis mechanism is as follows: First, the lone electron pair of the nitrogen atom in EDCI attacks the hydroxyl hydrogen of Boc-β-alanine, resulting in a positive charge for EDCI. Boc-β-alanine then loses its hydrogen to form a carboxyl oxygen anion. This oxygen anion attacks the double-bonded carbon of EDCI, forming an unstable intermediate. This intermediate contains a nitrogen atom with a lone electron pair. This nitrogen atom abstracts a hydrogen atom from the hydroxyl hydrogen of HOBT, converting HOBT into an oxygen anion. Subsequently, the oxygen anion of HOBT attacks the carbonyl carbon of Boc-β-alanine, cleaving the carbonyl oxygen bond and forming a stable active ester. Simultaneously, EDCI binds to the other carboxyl oxygen of Boc-β-alanine to form a ureido derivative. Under alkaline conditions, the amine group in diethylenetriamine is not protonated by the carboxyl group, thus maintaining its affinity. Secondary amines have low activity and large steric hindrance and will not react. The lone electron pair of the nitrogen atom in the primary amine attacks the carbonyl carbon atom on the active ester. After proton transfer, the bond between the carbonyl group and the adjacent oxygen is broken to form an amide compound with a Boc protecting group. The specific mechanism expression is shown below:

[0050]

[0051] 2. The synthesis of clay mineral surface hydration inhibitor (NPT) includes the following steps:

[0052] (1) Grind 2.53 g of the solid intermediate product into powder;

[0053] (2) Prepare a solution of 10 mL of hydrochloric acid / 1,4-dioxane (the volume of hydrochloric acid to 1,4-dioxane is 1:1) with 20 mL of an organic solvent (dichloromethane), then mix it with the ground intermediate product, seal it with plastic wrap, and stir at room temperature (25°C) for 12 h;

[0054] (3) Filter the post-reaction treatment liquid and retain the target product residue to obtain a clay mineral surface hydration inhibitor (NPT), weighing 1.75 g;

[0055] (4) Remove the Boc protecting group using hydrochloric acid method. The reaction mechanism is as follows: + The negatively charged oxygen atom on the Boc reacts to form a hydroxyl group, which changes the activity of the double-bonded carbon and finally generates isobutylene and gaseous carbon dioxide that are easily soluble in dichloromethane. The specific mechanism expression is shown below:

[0056]

[0057] 3. Infrared spectroscopy analysis

[0058] (1) Infrared spectroscopy analysis of intermediate products

[0059] The structure of the intermediate product was characterized by Fourier transform infrared spectroscopy. The test method was KBr tableting method. 2 mg of the intermediate product was mixed with 200 mg of pure KBr, ground to a particle size of less than 2 μm, and pressed into a transparent sheet for measurement on a tablet press. The infrared spectrum of the intermediate product was measured as follows: Figure 1 As shown. Figure 1 It can be seen that the secondary amine NH has only one stretching vibration, at 3360~3310cm -1 There is a sharp absorption peak, so Figure 1 3350cm -1 A secondary amine is generated by replacing one hydrogen atom of the primary amine in diethylenetriamine with a Boc protecting group; 3184 cm -1 It is the stretching vibration absorption peak of -NH in secondary amide; the stretching vibration region of methyl CH is 3000~2800cm -1 , so Figure 1 Medium 2960cm -1 The peak at 1662 cm should be the symmetrical stretching vibration absorption peak of the methyl group in the Boc protecting group; -1 It is the stretching vibration peak of the secondary amide C=O carbonyl group; the secondary amide NH is at 1570~1515cm -1 There is a bending vibration peak at 1557cm -1 The existence of secondary amides is also confirmed; the methyl CH bending vibration region is 1470-1300 cm -1 , 1375cm -1 The absorption band at 1230-1030 cm-1 also proves the presence of Boc protecting group; the secondary amine CN stretching vibration region is approximately 1230-1030 cm-1 -1 , so 1158cm -1 The peak at should be the stretching vibration absorption peak of secondary amine CN.

[0060] From the above infrared spectrum analysis, we can see that the spectrum contains characteristic peaks of secondary amine, secondary amide and Boc protecting group, among which secondary amide is the characteristic peak of the two products of the reaction. The reactant Boc-β-alanine is at 1650 cm -1 The characteristic absorption peaks of carboxylic acids on the left and right did not appear, indicating that the substance was a synthetic product and contained the designed functional groups. It was the desired target product and the synthesis experiment achieved the expected purpose.

[0061] (2) Infrared spectrum analysis of the final product

[0062] The product was characterized by Fourier infrared spectroscopy. The infrared spectrum of the final product was as follows: Figure 2 Theoretically, the symmetric and antisymmetric stretching vibrations of primary amine NH are between 3500 and 3100 cm -1 There are two medium-intensity absorption peaks. From the figure, it can be seen that at 3426cm-1 and 3055cm -1 There is a strong peak at 3500-3100 cm-1, which is due to the NH stretching vibration of the secondary amide. -1 There is a strong peak that overlaps with the stretching vibration of the primary amine NH; the stretching vibration range of the secondary amide C=O is 1680~1630cm -1 There is a strong peak at 1652cm -1 The peak at 1557 cm is the stretching vibration of secondary amide C=O; -1 It should be the in-plane bending vibration of the primary amine, which also proves the existence of the primary amine; the NH bending vibration and CN stretching vibration of the secondary amide are at 1570~1310cm -1 The two peaks overlap within the range, so 1458cm -1 This indicates the presence of secondary amides.

[0063] From the above infrared spectrum analysis of the final product, it can be seen that the spectrum contains characteristic peaks of primary amine and secondary amide at 3000~2800cm -1 No absorption occurred, indicating that the methyl group did not exist, and all the intermediate products reacted to form the final product, which contained the designed functional group. The synthesis experiment achieved the expected purpose.

[0064] 4. Mass spectrometry analysis

[0065] (1) Mass spectrometry analysis of intermediate products

[0066] The molecular formula of the intermediate product is: C 20 H 39 N5O6, accurate molecular weight: 445.29, molar mass: 445.56, mass-to-charge ratio: 2445.29 (100.0%), 446.29 (23.7%), 447.30 (2.4%), 447.29 (1.6%), elemental analysis: C, 53.91; H, 8.82; N, 15.72; O, 21.54. Figure 3 As can be seen, the highest intensity mass-to-nuclear ratio measured by mass spectrometry is 446.3. Since this is a positron scan, this corresponds exactly to the molecular weight of the intermediate product gaining one proton. The mass-to-nuclear ratio of 346.2 corresponds to the molecular weight of the intermediate product after it loses one Boc group. The mass-to-nuclear ratio of 246.2 corresponds to the molecular weight of the intermediate product after it loses two Boc groups. This agrees with the theoretical molecular weight, confirming the successful synthesis of the intermediate product.

[0067] (2) Mass spectrometry analysis of the final product

[0068] The molecular formula of NPT is: C 10 H 23N5O2, exact mass: 245.19, molar mass: 245.33, mass-to-charge ratio: 245.19 (100.0%), 246.19 (11.2%), 246.18 (1.8%), 247.19 (1.2%), elemental analysis: C, 48.96; H, 9.45; N, 28.55; O, 13.04. The data obtained by mass spectrometry were as follows: Figure 4 The highest mass-to-charge ratio detected by mass spectrometry was 246.2. Since it was a positive ion scan, the NPT molecule obtained a proton, and the molecular weight was 245.2. Therefore, the molecular weight obtained by mass spectrometric analysis of the product was consistent with the theoretical exact molecular weight.

[0069] 5. Analysis of nuclear magnetic resonance hydrogen spectrum

[0070] Nuclear magnetic resonance hydrogen spectrum (1H NMR) can reflect the nuclear magnetic resonance effect of hydrogen-1 in the molecule in the spectrum. By analyzing the integral area of different H peaks, the proton ratio of each group can be obtained to determine the molecular structure. Figure 5 The nuclear magnetic resonance hydrogen spectrum of the product was analyzed. No signal was observed for active hydrogen in water, and no signal was observed for hydrogen on primary amine and secondary amide. The 1H NMR spectrum of the compound showed four groups of hydrogen proton signals, and the NPT molecule was a symmetrical structure. The peak with an integral of 4 at 2.77-2.72 ppm was the hydrogen signal of position b, the peak with an integral of 4 at 3.32-3.27 ppm was the hydrogen signal of position d, the peak with an integral of 4 at 3.49-3.44 ppm was the hydrogen signal of position a, and the peak with an integral of 4 at 3.61-3.54 ppm was the hydrogen signal of position b. Based on the above nuclear magnetic hydrogen spectrum information, it was determined that the structure was the target structure.

[0071] Through the above test analysis, it was determined that the inhibitor molecule had C chain as the hydrophobic chain, the two ends of the molecule were primary amine, which could make the molecule have certain water solubility, there was an amide group as a connecting group in the middle, which could effectively reduce the biological toxicity, the molecular structure was linear structure, and the arrangement mode in intercalation was single-layer paving. Under certain conditions, amide reaction was carried out, and finally the linear small molecule inhibitor containing alkane, amide group and amine group was obtained. IR, MS and HNMR were used to characterize the structure of the intermediate and the final product.

[0072] (1) Boc-β-alanine and diethylenetriamine were used as reactants to generate an intermediate product. The characteristic peaks of tertiary butyl, secondary amine and secondary amide were detected in the intermediate product by infrared spectroscopic analysis, indicating that the intermediate product was successfully synthesized. The mass-to-charge ratio of 446.3 was detected in the intermediate product by mass spectrometric analysis, which was exactly the molecular weight corresponding to the removal of one and two Boc groups. The results showed that the intermediate product was successfully synthesized.

[0073] (2) Synthesis and structure characterization of NPT inhibitor molecule:

[0074] The intermediate product was subjected to hydrochloric acid method to remove the Boc protecting group to obtain the product. The final product was detected by infrared spectroscopy, and no absorption peak related to the Boc protecting group appeared in the spectrum, indicating that the Boc protecting group had been successfully removed and the target product NPT molecule was synthesized. Mass spectrometry analysis detected that the mass-to-charge ratio of the synthesized product was 246.2, which was exactly the theoretical exact molecular weight of NPT molecule with one proton. The target product NPT was determined by nuclear magnetic resonance hydrogen spectrum test.

[0075] 6. Evaluation of inhibition performance of clay mineral surface hydration inhibitor

[0076] 6.1. Experimental reagents and instruments

[0077] The main experimental reagents and experimental instruments required for the inhibition performance test analysis of the synthesized NPT are shown in Tables 3 and 4.

[0078] Table 3

[0079] Reagent name Purity Manufacturer Sodium bentonite Industrial Bohai drilling engineering co., LTD Shale rock debris Industrial - Sodium montmorillonite 98％ NANOCOR company NPT inhibitor Higher Experimental synthesis

[0080] Table 4

[0081]

[0082]

[0083] 6.2. Evaluation method of inhibition performance of NPT

[0084] (1) Linear expansion method

[0085] Linear expansion experiment is a method for evaluating the inhibition effect of drilling fluid on clay minerals by measuring the linear expansion rate of bentonite in drilling fluid, so as to help drilling engineers select appropriate drilling fluid formula to prevent shale expansion from causing well wall collapse or hole size change, and thus ensure the safety and efficiency of drilling operation.

[0086] Specific experimental steps: a certain amount of bentonite is dried at 108°C for 4h, 10g of dried bentonite is weighed and put into the test cylinder of the linear dilatometer, the test cylinder is placed on the pressure machine, the pressure is kept at 5MPa, and the pressure is kept for 5min, then the mud cake is taken out, the original height of the core is measured, and is recorded as L0(mm). Prepare the inhibitor solution (i.e. the above obtained inhibitor is added to water to prepare a solution with a concentration of 0.5wt%, 1.0wt%), select pure water as the reference for linear expansion rate evaluation, i.e. the blank group. Install the test cylinder in the NP-01 shale expansion tester at room temperature and atmospheric pressure, and pour the prepared inhibitor solution into the test cylinder to the scale line until it is flush with the upper end face of the test cylinder, ensuring that the dial pointer is 0, start timing, and the computer automatically records the expansion height AL(mm) of the measured mud cake, and records for 8h. The linear expansion rate is calculated as follows:

[0087]

[0088] In the formula: α t Linear expansion rate, %;

[0089] ΔL - the expansion height of the core at a certain time, mm;

[0090] L0 - the original height of the core, mm.

[0091] (2) Shale rolling recovery method

[0092] The shale rolling recovery experiment simulates the state of cuttings in the drilling fluid during the drilling process to qualitatively evaluate the inhibition performance of the drilling fluid, assists the drilling engineer to select an inhibitor treatment agent that can effectively inhibit the expansion and dispersion of shale, prevents the collapse of the well wall and the change of the borehole size during drilling, and thus ensures the safety and efficiency of the drilling operation.

[0093] Specific experimental steps: 350mL of the inhibition solution is prepared and placed in an aging tank, and then 50.0g of cuttings passing through a 6-mesh but not a 10-mesh sieve is weighed and added to the aging tank. After sealing with a cover, the tank is placed in a high-temperature roller oven and heated and rolled at 105°C for 16h. After the heating and rolling is completed, the tank is taken out and cooled to room temperature, the mixture in the tank is poured onto a 40-mesh sieve, the cuttings on the sieve are slowly washed with tap water, and finally the cuttings larger than 40 mesh are dried at 105°C for 24h and weighed, recorded as m, and the rolling recovery rate (P) is calculated as follows:

[0094]

[0095] In the formula: P - rolling recovery rate, %;

[0096] m - the mass of the recovered cuttings, g.

[0097] (3) Isothermal adsorption method

[0098] The isothermal adsorption method was used to determine the unit adsorbed water content of clay minerals under the action of inhibitors. The adsorption amount of gaseous water on sodium montmorillonite samples increased with the extension of adsorption time, and the growth rate showed a decreasing trend. Within a certain time, the adsorption amount no longer increased with the growth of time, but reached a state of balance.

[0099] Specific experimental steps: The sodium montmorillonite was dried at 150°C to constant weight, and NPT aqueous solutions with concentrations of 0.5wt% and 1.0wt% were prepared, respectively. 0.5g of dried sodium montmorillonite was added to the NPT solutions of the two concentrations, respectively, stirred for 24h, and the suspension was poured into a centrifuge tube and centrifuged at 5000rpm for 10min to obtain the solid precipitate. The precipitate was vacuum dried at 105°C and was placed in a weighing bottle with mass m0. The mass was m1. The weighing bottle was placed in a desiccator with a relative humidity of 0.53, the weighing bottle cap was opened and the desiccator cap was covered, and isothermal adsorption was carried out at 25°C until equilibrium. The weighing bottle was taken out and its mass was m2, and the mass of the weighing bottle after isothermal adsorption equilibrium was m3. The calculation method of the unit equilibrium water adsorption of clay minerals is as follows:

[0100]

[0101] In the formula: m a —unit adsorbed water mass percentage;

[0102] m0—mass of the weighing bottle, g;

[0103] m1—total mass of the weighing bottle and sample, g;

[0104] m2—total mass of the weighing bottle and sample after isothermal adsorption equilibrium, g;

[0105] m3—mass of the weighing bottle after isothermal adsorption equilibrium, g.

[0106] (4) X-ray diffraction method

[0107] X-ray diffraction (XRD) method is mainly used to analyze the crystal structure, phase, crystallinity, lattice constant, stress and texture, and particle size of materials, and has wide application and importance in the research of materials in the fields of materials science, chemistry, physics and biology. X-ray diffraction method mainly shows the information of diffraction peak position and intensity of crystal materials, mainly including peak width, diffraction angle (2θ), i.e. the change of interplanar spacing, and diffraction peak intensity, which can reflect the order degree of atomic arrangement in the crystal.

[0108] X-ray diffraction often uses the Bragg equation: 2dsinθ = nλ, where n is the diffraction order (usually 1), d is the interplanar spacing, θ is the Bragg angle (the difference between the incident angle and half the diffraction angle), and λ is the wavelength of the target. This experiment used X-ray diffraction to determine the relationship between interplanar spacing and water content, which can help explain the swelling properties of sodium montmorillonite and study the hydration state of intercalated clay minerals.

[0109] (5) Thermogravimetric analysis method

[0110] Thermogravimetric analysis (TGA) is an experimental method that studies the thermal properties and thermal stability of materials by continuously recording the mass changes of samples at a certain temperature. Through thermogravimetric analysis, the mass change curve of the sample under increasing or constant temperature conditions can be obtained, and the thermal decomposition characteristics and adsorption properties of the material can be understood, which is of great significance for the thermal treatment and thermal stability evaluation of the material. It can measure the increase or decrease of the sample, and can also measure the mass change steps of the sample (usually expressed as a weight percentage of the starting sample). Using thermogravimetric analysis technology, qualitative analysis, component analysis, thermal property determination and kinetic parameter determination of substances can be achieved, and it has broad application prospects in the development of new materials and quality monitoring. According to the number and peak position of the peaks shown on the DTG curve, the TG curve can be divided into weight loss steps to obtain the type and content of bound water, thereby distinguishing the types of bound water.

[0111] The DTG curve can be used to find the temperature inflection point of bound water and free water. The corresponding ordinate value of this temperature on the TG curve is the mass of bound water and montmorillonite. The abscissa value corresponding to the first ordinate value of 0 on the DTG curve is the temperature value, and the corresponding ordinate value of this temperature on the TG curve is the mass of the clay mineral. Therefore, the mass change ladder of the clay mineral can be obtained through thermogravimetric analysis, from which the type of bound water in the clay mineral under the action of the inhibitor can be inferred.

[0112] 6.3. Evaluation results of NPT inhibition performance

[0113] (1) Linear expansion test

[0114] Using clean water as a reference, the linear expansion rates of 0.5wt% and 1.0wt% NPT inhibitors were tested. The experimental results are as follows: Figure 6 .from Figure 6It can be seen that with the increase of time, the linear expansion rate of the sample increases until it reaches equilibrium. The linear expansion rate of pure water is 38%, indicating that it has strong hydration ability. After adding 0.5wt% NPT inhibitor, the linear expansion rate decreases to 20%, indicating that NPT has good inhibition ability. Further increasing the concentration to 1.0wt%, the linear expansion rate is 19%, which is close to the inhibition performance of 0.5% NPT, indicating that 0.5wt% NPT inhibitor can effectively inhibit the hydration expansion of shale.

[0115] (2) Shale rolling recovery experiment

[0116] Figure 7 The rolling recovery rate of NPT inhibitor is shown. The rolling recovery rate of pure water is low, which is 19.5%, indicating that shale debris is easy to hydrate and disperse in pure water. After adding NPT inhibitor, the rolling recovery rate increases significantly, indicating that NPT has the ability to inhibit the hydration and dispersion of shale debris. When the concentration of NPT is 0.5wt%, the rolling recovery rate is 63.7%. Further increasing the concentration to 1.0wt%, the rolling recovery rate only increases by 1.8%, indicating that 0.5wt% NPT has good ability to inhibit the hydration and dispersion of shale debris.

[0117] (3) Isothermal adsorption experiment

[0118] Isothermal adsorption experiments were conducted on sodium montmorillonite with 0.5wt%, 1.0wt% NPT inhibitor and pure sodium montmorillonite without inhibitor. Due to the increase of relative humidity, the adsorbed water content of sodium montmorillonite will increase, and when the relative humidity is 1.0, the adsorbed water content of sodium montmorillonite will reach the maximum, so the experiment is conducted at a relative humidity of 0.53.

[0119] Figure 8 is the isothermal adsorption result of sodium montmorillonite treated with NPT inhibitor. As can be seen from the figure, the unit adsorbed water content of pure sodium montmorillonite is 0.1104g / g, indicating that sodium montmorillonite is easy to absorb water and hydrate and expand. After adding NPT inhibitor, the unit adsorbed water content is significantly lower than that of pure sodium montmorillonite, indicating that NPT can effectively inhibit the adsorption of water molecules by sodium montmorillonite. When the dosage of NPT inhibitor is 0.5wt%, the unit adsorbed water content is reduced by about 62.6% compared with pure sodium montmorillonite, and when the dosage is 1wt%, the unit adsorbed water content is reduced by about 71.3% compared with pure sodium montmorillonite. The results show that NPT inhibitor can effectively prevent the adsorption of water molecules by clay minerals.

[0120] (4) X-ray diffraction experiment

[0121] Figure 9 and Figure 10are basal spacing of NPT-sodium montmorillonite composites with different concentrations of NPT. The basal spacing of pure sodium montmorillonite is 1.01 nm, the diameter of water molecule is 0.25 nm, the basal spacing of single-layer hydrated sodium montmorillonite is 1.25 nm, the basal spacing of double-layer hydrated sodium montmorillonite is 1.50 nm, and the basal spacing of fully hydrated sodium montmorillonite is increased to 1.90 nm. As shown in Figure 9 , by calculation through Bragg equation, the basal spacing of dry-state sodium montmorillonite with 0.5wt% and 1.0wt% of NPT inhibitor is 1.28 nm, which is greater than the basal spacing of sodium montmorillonite 1.01 nm, indicating that the inhibitor is inserted into the interlayer of clay minerals. As shown in Figure 10 , the basal spacing of hydrated sodium montmorillonite is decreased from 1.90 nm (i.e. without inhibitor, not shown in the figure) to 1.30 nm. It can be seen that when the amount of inhibitor is 0.5wt% and 1.0wt%, NPT makes the basal spacing of sodium montmorillonite above 1.25 nm but below 1.50 nm. This indicates that under the action of NPT inhibitor, sodium montmorillonite can only coat one layer of water molecules.

[0122] (5) Thermogravimetric analysis experiment

[0123] The NPT-sodium montmorillonite composites and pure sodium montmorillonite after isothermal adsorption under the condition of relative humidity of 0.53 were subjected to thermogravimetric analysis, and three groups of thermogravimetric analysis curves were obtained. As can be seen from the TG curve of Figure 11 , the pure sodium montmorillonite has two steps, which exactly corresponds to the two peaks of the DTG curve in Figure 12 , indicating that there are two types of adsorbed water in the pure sodium montmorillonite. The water corresponding to the first stage is free water or surface adsorbed water, and the water corresponding to the second stage is interlayer cation adsorbed water. After adding 0.5wt% and 1.0wt% of NPT inhibitor, the TG curve only has two steps, and the DTG curve only has one peak, indicating that the addition of NPT inhibitor makes the sodium montmorillonite contain only one type of adsorbed water, inhibits the interlayer cation adsorbed water reaction, and limits the adsorbed water of NPT-sodium montmorillonite composite system to the outside surface of the particles, i.e. NPT inhibitor can completely inhibit the surface hydration of clay minerals.

[0124] In the D2TG curve of Figure 13 , it is observed that the pure sodium montmorillonite has two peaks, and the NPT-sodium montmorillonite after treatment with NPT inhibitor has one peak, further indicating that NPT inhibitor can completely inhibit surface hydration.

[0125] Based on the above, the linear expansion experiment, shale rolling recovery experiment, isothermal adsorption experiment, X-ray diffraction experiment and thermal gravimetric analysis experiment are carried out on the clay mineral samples before and after intercalation to explore the inhibition performance of the prepared NPT inhibitor on the surface hydration of clay minerals, and the following conclusions are drawn:

[0126] (1) The linear expansion experiment and shale rolling recovery experiment show that the linear expansion rate of NPT is 15%, and the rolling recovery rate is 65.5%, which indicates that the NPT inhibitor can effectively inhibit the hydration expansion of shale.

[0127] (2) The surface hydration inhibition ability of NPT is evaluated by isothermal adsorption, X-ray diffraction and thermal gravimetric analysis, and the results show that the unit adsorbed water amount of sodium montmorillonite after adding the inhibitor NPT is significantly less than that of pure sodium montmorillonite, and the inhibition effect of 1wt% addition is greater than that of 0.5wt% addition. X-ray diffraction experiment shows that NPT can be inserted into the interlayer of clay minerals, reducing the basal spacing of sodium montmorillonite and inhibiting the hydration of clay minerals. Thermal gravimetric analysis shows that the sample with added inhibitor only has a low-temperature peak in the range of 100℃-150℃, and the thermal gravimetric analysis (TG) curve only shows an obvious step, and the derivative thermogravimetric (DTG) curve only shows a peak value. The results show that the addition of NPT has a significant effect on the pyrolysis characteristics of sodium montmorillonite, making sodium montmorillonite contain only one type of adsorbed water. The inhibitor can inhibit the interlayer surface hydration and interlayer cation hydration of sodium montmorillonite, and only has extragranular surface adsorbed water. The results show that NPT effectively inhibits the surface hydration of clay minerals.

[0128] In the description of the present specification, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0129] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A clay mineral surface hydration inhibitor characterized in that, The structural formula of the clay mineral surface hydration inhibitor is shown as follows:

2. A method for producing the clay mineral surface hydration inhibitor as claimed in claim 1, characterized by, The method comprises the following steps: A, preparing a Boc-β-alanine solution, and adding an activating agent, a condensing agent and a catalyst under the condition of an ice water bath, stirring and reacting, then adding diethylenetriamine, filtering the obtained solid after reaction, purifying the solid, and filtering and drying the solid again to obtain a solid intermediate product; B, grinding the solid intermediate product obtained in step A into powder; C, preparing a solution of hydrochloric acid / 1,4-dioxane and an organic solvent, then mixing the solution with the powder ground in step B, stirring and reacting under sealing, and filtering the treatment liquid after reaction to obtain filter residue, which is the clay mineral surface hydration inhibitor.

3. The production method according to claim 2, characterized by, In step A, the molar concentration of the Boc-β-alanine solution is 0.15 mol / L.

4. The preparation method according to claim 2, characterized in that In step A, the temperature of the ice water bath is controlled at 0-5℃, and the stirring and reaction temperature is 25℃, and the reaction time is 0.5 h.

5. The preparation method according to claim 2, characterized in that In step A, the drying temperature is 80℃, and the drying time is 8 h.

6. The preparation method according to claim 2, characterized in that In step A, the molar ratio of the Boc-β-alanine, the activating agent, the condensing agent and the catalyst is 3:3:3:5, and the molar ratio of the Boc-β-alanine and diethylenetriamine is 2:

1.

7. The production method according to claim 6, wherein The activating agent is 1-hydroxybenzotriazole, the condensing agent is 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride, and the catalyst is triethylamine.

8. The preparation method according to claim 2, characterized in that In step C, the reaction temperature is 25℃, and the reaction time is 12 h.

9. The preparation method according to claim 2, characterized in that In step C, the volume ratio of the hydrochloric acid / 1,4-dioxane and the organic solvent is 1:2, the volume ratio of the hydrochloric acid and 1,4-dioxane is 1:1, and the organic solvent is dichloromethane.

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