Preparation method and application of hydration inhibitors for clay mineral surfaces
A non-toxic hydration inhibitor for clay minerals synthesized via a chemical process addresses wellbore stability issues in shale gas drilling, improving drilling fluid performance and reducing costs by effectively inhibiting clay mineral hydration.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-09-11
- Publication Date
- 2026-03-31
AI Technical Summary
The stability of wellbore walls during shale gas drilling is compromised by clay mineral hydration, leading to complex wellbore accidents and high costs, which current aqueous drilling fluids fail to adequately address due to ineffective inhibitors.
A hydration inhibitor for clay mineral surfaces, synthesized through a specific chemical process, effectively inhibits clay mineral hydration in aqueous drilling fluids, reducing basal spacing and replacing exchangeable cations, while being non-toxic and cost-effective.
The inhibitor significantly reduces clay mineral hydration, maintaining wellbore stability with minimal addition, lowering costs and environmental impact, and enhancing drilling fluid performance.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of drilling fluids for oil drilling, and particularly to a preparation method and application of a hydration inhibitor on the surface of clay minerals.
Background Art
[0002] In the "Shale Gas Development Plan (2016 - 2020)" released by the National Energy Administration of China, it aims to achieve a shale gas production of 30 billion cubic meters in 2020 and 80 billion cubic meters in 2030. The development of shale gas has already become a strategic resource for China's national energy development. However, realizing the safety, high quality, and rapid drilling of the long horizontal section (>2000 meters) of horizontal tunnels has become a difficulty in shale gas development, among which the stability of the wellbore wall is an extremely difficult problem to solve.
[0003] When drilling a slate formation containing clay minerals with a drilling fluid, usually, the stability of the wellbore wall is easily lost. In the drilling operation, 75% of the drilled formation is a shale formation, and 90% of the problems of losing the stability of the wellbore wall occur in this area. Once the stability of the wellbore wall is lost, it will cause complex wellbore accidents such as clay adhesion to the drill, collapse of the wellbore wall, high torque, high resistance, the drill not moving, and the drilling diameter being smaller than the drill diameter. Therefore, when the stability of the wellbore wall is lost, it will have a serious impact on the drilling speed and may lead to a significant increase in exploration and production costs. According to research, the losses caused by the unstable wellbore wall exceed 100 million US dollars per year and account for more than 10% of the drilling cost.
[0004] Shale gas has already become a strategic resource for China's national energy development, and currently, most shale gas horizontal tunnel drilling operations, particularly long horizontal stages, primarily utilize oil-based drilling fluids. Oil-based drilling fluids have advantages over water-based drilling fluids, such as the ability to completely suppress the hydration of clay minerals in the formation, resulting in better tunnel wall stability, stable fluid performance, and less damage to oil and gas layers. However, high deployment and application costs, as well as environmental pollution issues, limit the application of oil-based drilling fluids. Therefore, the development of water-based drilling fluids that can match the performance of oil-based drilling fluids is a crucial direction for drilling fluid technology development both domestically and internationally.
[0005] To replace oil-based drilling fluids, the first challenge that must be overcome is the hydration problem of clay mineral surfaces when using aqueous drilling fluids. Currently, inhibitors used in aqueous drilling fluids can suppress clay penetration and hydration, but there are no inhibitors that effectively solve the problem of surface hydration. Currently, when high concentrations of organic salts are used as inhibitors, surface hydration can be suppressed through the law of active equilibrium, but high concentrations are costly, cause environmental pollution, and have serious drawbacks that seriously affect the rheological properties of the drilling fluid. [Overview of the Initiative] [Problems that the invention aims to solve]
[0006] To solve the above technical problems, the present invention provides a hydration inhibitor for clay mineral surfaces, a method for preparing the same, and its applications. [Means for solving the problem]
[0007] To achieve the above objectives, the embodiments of the present invention employ the following technical solutions.
[0008] The present invention provides a hydration inhibitor for clay mineral surfaces, and the structure of the hydration inhibitor for clay mineral surfaces is as follows.
[0009] [ka]
[0010] The present invention further provides a method for preparing a hydration inhibitor for the surface of clay minerals, comprising the following steps.
[0011] 5 g of tert-butyl [2-(2-aminoethoxy group)ethyl]carbamate was added to a 100 mL one-necked flask, and then 80 mL of acetonitrile, 7.8 g of sodium carbonate, and 0.5 g of sodium iodide were added. The mixture was stirred at room temperature for 0.5 hours, then 2.83 g of bis(2-bromoethyl) ether was added, and the mixture was refluxed at 70°C for 48 hours. After removing excess sodium iodide and sodium carbonate by vacuum filtration, the reaction mixture was concentrated in a rotary evaporator, the product was washed with petroleum ether, and the intermediate product was dried.
[0012] 30 mL of saturated ethyl acetate solution was added to the crude product to remove the Boc protecting group, and the mixture was stirred at room temperature for 4 hours. A large amount of white solid precipitated, and after the reaction was complete, the mixture was filtered under reduced pressure. The filtered cake was retained and vacuum-dried to obtain 5.22 g of the clay mineral surface hydration inhibitor.
[0013] In some embodiments, the vacuum drying temperature is 80°C and the drying time is 12 hours.
[0014] The specific composite equation is as follows:
[0015] The present invention further provides applications of the clay mineral surface hydration inhibitor obtained by the above preparation method in aqueous drilling fluids. [Effects of the Invention]
[0016] Compared to the prior art, the present invention has the following advantages.
[0017] The inhibitor of the present invention is used in an aqueous drilling fluid to inhibit the hydration of the clay mineral surface, can effectively inhibit the hydration of the clay mineral surface, has a small addition amount, low cost, and is a non-toxic inhibitor. It can completely inhibit the hydration of the clay mineral surface at an addition amount of 1 wt%, and can reduce the basal spacing of wet montmorillonite from 1.91 nm to 1.43 nm, and has an excellent ability to replace the exchangeable cations between layers. According to the toxicity test results, the 1 wt% aqueous solution of the inhibitor is non-toxic.
Brief Description of the Drawings
[0018] [Figure 1] It is the infrared spectrum of the hydration inhibitor SJ-1 for the clay mineral surface of the present invention. [Figure 2] It is the mass spectrum of the hydration inhibitor SJ-1 for the clay mineral surface of the present invention. [Figure 3] It is a diagram showing the change in the basal spacing of the montmorillonite complex which is the inhibitor. [Figure 4] It is a diagram showing the change in the basal spacing of the montmorillonite complex which is the inhibitor after isothermal adsorption. [Figure 5] It is the TG and DTG curve diagram of the montmorillonite complex which is the inhibitor. [Figure 6] It is an image of the montmorillonite complex which is the inhibitor taken by a scanning electron microscope. [Figure 7] It is the NIS diagram of the montmorillonite complex which is the inhibitor. [Figure 8] It is the Nals diagram of the montmorillonite complex which is the inhibitor.
Modes for Carrying Out the Invention
[0019] Hereinafter, in conjunction with the drawings, the technical solutions of some embodiments of the present invention will be clearly and completely described. Obviously, the embodiments described here are not all embodiments of the present invention, but some embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.
[0020] Examples
[0021] 5 g of tert-butyl [2-(2-aminoethoxy group)ethyl]carbamate (SW1) is added to a 100 mL one-necked flask, and then 80 mL of acetonitrile, 7.8 g of sodium carbonate, and 0.5 g of sodium iodide are added. The mixture is stirred at room temperature for 0.5 hours, then 2.83 g of bis(2-bromoethyl) ether (SW2) is added, and the mixture is refluxed at 70°C for 48 hours. After removing excess sodium iodide and sodium carbonate by vacuum filtration, the reaction mixture is concentrated in a rotary evaporator, the product is washed with petroleum ether, and the mixture is dried to obtain the intermediate product (SW3).
[0022] 30 mL of saturated ethyl acetate solution was added to the crude product to remove the Boc protecting group, and the mixture was stirred at room temperature for 4 hours. A large amount of white solid precipitated, and after the reaction was complete, the mixture was filtered under reduced pressure. The filtered cake was retained and vacuum-dried for 12 hours to obtain 5.22 g of product (SJ-1) (2,2'-oxobis(N-(2-(2-aminoethoxy)ethyl)ethylamine)), which is a hydration inhibitor for clay mineral surfaces.
[0023] The specific composite equation is as follows:
[0024] [ka]
[0025] Examples
[0026] The main experimental reagents and instrumental analyses used in the experiment are shown in Tables 1 and 2.
[0027] Table 1. Main experimental reagents
[0028] [Table 1]
[0029] Table 2 Main experimental equipment
[0030] [Table 2]
[0031] 1. Infrared spectroscopy
[0032] Figure 1 shows the infrared spectrum of SJ-1. As can be seen from Figure 1, 3437 cm⁻¹ ‐1 This corresponds to the N-H stretching vibration peak. 3033cm ‐1 This is the C-H stretching vibration peak, 1132 cm. ‐1 This represents the stretching vibration peak of the ether bond C-O-C. The infrared spectral data is consistent with the molecular structure of SJ-1, indicating that the synthesis of SJ-1 was successful.
[0033] 2. Mass Spectrometry
[0034] The molecular formula for SJ-1 is C 12 H 30 The compound is N4O3, with a molecular accurate mass of 278.23, a molar mass of 278.40, and a mass-to-charge ratio of 278.23 (100.0%), 279.24 (13.0%), and 279.23 (1.5%). Elemental analysis shows C: 51.77, H: 10.86, N: 20.13, and O: 17.24. As can be seen from Figure 2, the mass-to-charge ratio measured by LC-MS is 279.23. Due to positive ion scanning, SJ-1 acquires one proton, and its molecular weight is 278.23, which is consistent with the theoretical molecular accurate mass.
[0035] 3. Isothermal adsorption analysis
[0036] (1) The inorganic salt solution corresponding to a temperature of 25°C and a relative humidity of 0.53 is a saturated magnesium nitrate solution. (2) Add deionized water to the bottom of the drying dish, then slowly add magnesium nitrate until a saturated solution is formed, and maintain at 25°C for 24 hours until equilibrium is reached. (3) Polish the dried montmorillonite composite, sift it through a 200-mesh sieve, and after sieving, dry the montmorillonite composite at 150°C for 24 hours. Add 1 g of the dried montmorillonite composite to a weighing bottle, weigh it, and record the result. (4) Place the weighing bottle in the equilibrium drying dish and leave it for 15 days. After adsorption occurs under isothermal conditions and equilibrium is reached, remove the weighing bottle using airlaid paper, weigh it on a balance with an accuracy of 0.0001 mg, and record the result. Calculate the equilibrium water absorption of the montmorillonite composite using the following formula.
[0037]
number
[0038] Here, m e --This is the amount of water (g) adsorbed by the montmorillonite composite.
[0039] m0 is the mass (g) of the weighing bottle.
[0040] m1 is the mass (g) of the montmorillonite composite and the weighing bottle.
[0041] m2 is the mass (g) of the montmorillonite composite and the weighing bottle after adsorption under isothermal conditions and reaching equilibrium.
[0042] m3 — This is the mass (g) of the weighing bottle after adsorption under isothermal conditions has reached equilibrium.
[0043] Under isothermal conditions of 25°C and a relative humidity of 0.53, the water content of the montmorillonite complex, the inhibitor, after adsorption is 4.2291%.
[0044] 4. X-ray diffraction analysis
[0045] X-ray diffraction analysis was performed on the hydration inhibitors on the clay mineral surfaces prepared in the examples using an X Pert PRO MPD type X-ray diffractometer, targeting Cu. Bragg's law, equation 2dsinθ=nλ, was adopted, where n is the diffraction order, and here n=1. θ is the diffraction angle (i.e., the θ angle corresponding to the diffraction peak), with a diffraction wavelength λ=0.154056nm, an operating voltage of 40kV, a current of 30mA, and a scanning angle 2θ=3~40°. Figure 3 shows the basal spacing of the SJ-1-montmorillonite composite (1wt%SJ-1 + 2wt%montmorillonite, solvent is water). As can be seen from the figure, adding 1 wt% of SJ-1 reduces the basal spacing of the hydrated montmorillonite composite from 1.91 nm to 1.43 nm, and increases the basal spacing of the dry SJ-1-montmorillonite composite from 1.01 nm to 1.31 nm. The product obtained by mixing SJ-1, montmorillonite, and water and centrifuging it is a wet SJ-1-montmorillonite composite, and drying the wet montmorillonite composite yields a dry SJ-1-montmorillonite composite. This indicates that SJ-1 has excellent ability as an inhibitor, inserting between montmorillonite crystal layers, reducing the basal spacing of the montmorillonite composite, and expelling interlayer water molecules.
[0046] Figure 4 shows the basal spacing of the SJ-1-montmorillonite composite after adsorption under isothermal conditions. As can be seen from the figure, the basal spacing of the SJ-1-montmorillonite composite after adsorption under isothermal conditions matches the basal spacing of the dry state shown in Figure 3. This proves that the adsorption energy of SJ-1 between montmorillonite layers is greater than the adsorption energy of water molecules. Furthermore, the basal spacing of dry montmorillonite is 1.01 nm, the diameter of a water molecule is 0.25 nm, the basal spacing of single-layer hydrated montmorillonite is 1.18-1.24 nm, and the basal spacing of double-layer hydrated montmorillonite is 1.45-1.55 nm. The interlayer spacing of the SJ-1-montmorillonite complex after adsorption under isothermal conditions is 0.30 nm. After subtracting the height of the single layer water molecules, the height of the remaining layer space is 0.05 nm, which is less than 0.20 nm. Therefore, the SJ-1-montmorillonite complex after adsorption under isothermal conditions can only accommodate single layer water molecules.
[0047] 5, Thermogravimetric analysis
[0048] Figure 5 shows the TG and DTG curves of the SJ-1-montmorillonite composite after it adsorbed under isothermal conditions at 25°C and a relative humidity of 0.53, reaching equilibrium, and then measured using a thermogravimetric analyzer. As can be seen from the figure, the SJ-1-montmorillonite composite TG curve shows only one step, and the DTG curve shows only one peak. Classification of adsorbed water types by Gates and preliminary laboratory work indicates that SJ-1 can suppress hydration of both the montmorillonite interlayer surface and cation hydration, and that the SJ-1-montmorillonite composite adsorbs water only on the outer surface of the particles.
[0049] Under isothermal conditions of 25°C and a relative humidity of 0.53, the water content of the montmorillonite composite, an adsorption inhibitor, was measured. The DTG curve for montmorillonite (2wt% montmorillonite, solvent is water, and used as a control group) showed two peaks, with the converted water contents of the first and second peaks being 7.67% and 5.36%, respectively. SJ-1-montmorillonite showed one peak, with a converted water content of 3.948%.
[0050] 6. Scanning electron microscopy analysis
[0051] Figure 6 is a scanning electron microscope image of the montmorillonite complex, which is an SJ-1 inhibitor. As can be seen from Figure 6, when the inhibitor (SJ-1) is added, the montmorillonite can be rolled into a ball shape, demonstrating that the inhibitor has excellent inhibitory properties.
[0052] 7. X-ray photoelectron spectrum
[0053] Figure 7 shows the N1s diagram of the montmorillonite composite, which acts as an inhibitor. As can be seen from the figure, compared to pure montmorillonite (control sample), the SJ-1-montmorillonite composite clearly has an N1s type, indicating that SJ-1 is adsorbed on the surface of montmorillonite. Figure 8 shows the Na1s diagram of the montmorillonite composite, which acts as an inhibitor. As can be seen from the figure, compared to pure montmorillonite (control group), SJ-1 can replace the interlayer exchangeable ions (sodium ions) and play a role in suppressing hydration on the clay mineral surface.
[0054] 8. Atomic absorption spectrophotometer analysis
[0055] Table 3 shows the sodium ion content of the montmorillonite composite, which is a non-toxic intercalation inhibitor. As can be seen from Table 3, the sodium ion content of the montmorillonite composite, a non-toxic intercalation inhibitor, is lower than that of pure sodium montmorillonite. This confirms that all non-toxic intercalation inhibitors can effectively replace the sodium ions between the montmorillonite layers, thus demonstrating the conclusions of the X-ray photoelectron spectroscopy studies.
[0056] Table 3. Sodium ion content (mmol / 100g) of the inhibitor montmorillonite complex.
[0057] [Table 3]
[0058] 9.Toxicity research
[0059] Biotoxicity assessment is a means of evaluating the potential contamination and toxic hazards of a specific chemical substance or mixture to the environment. Several methods exist both domestically and internationally for evaluating the biotoxicity of drilling fluid, and among them, bioluminescent bacterial testing is rapid, convenient, highly sensitive, and low-cost.
[0060] When evaluating the biotoxicity of a sample using the bioluminescent bacterial method, first prepare an SJ-1 solution (1 wt%). Based on the "Q / SY China National Petroleum & Gas Group's Corporate Standard for Classification and Measurement of Biotoxicity of Oilfield Treatment Agents and Drilling Fluids: Bioluminescent Bacteria Method," measure the luminescence of the sample group and the control group using a DXY-2 biotoxicity analyzer produced by the Institute of Soil Science, Chinese Academy of Sciences, and calculate the relative luminescence intensity. The mass concentration of the substance being evaluated when the luminescence intensity of the bioluminescent bacteria is reduced by half is recorded as EC50. EC50 is an index for evaluating biotoxicity; the higher the EC50 value, the lower the toxicity of the substance being evaluated. The toxicity grades are shown in Table 4.
[0061] Table 4 List of biotoxicity grades
[0062] [Table 4]
[0063] Table 5 shows the toxicity test results for the inhibitor. As can be seen from Table 5, the toxicity of the inhibitor is very low and it is considered non-toxic.
[0064] Table 5: Results of compound toxicity tests
[0065] [Table 5]
[0066] As can be seen from the above, when 1 wt% of the SJ-1 inhibitor is added, it can completely suppress the hydration of the clay mineral surface, reduce the basal spacing of wet montmorillonite from 1.91 nm to 1.43 nm, and exhibits excellent ability to replace interlayer exchangeable cations. Toxicity tests have demonstrated that a 1 wt% aqueous solution of the inhibitor is non-toxic.
[0067] In this specification, specific features, structures, materials, or properties can be combined in appropriate ways in any one or more embodiments or examples.
[0068] The above describes only specific embodiments of the present invention, and the scope of protection of the present invention is not limited thereto. Those skilled in the art will know that any modifications or substitutions made within the scope of the art disclosed by the present invention are also covered by the present invention. Therefore, the scope of protection of the present invention must be the same as the scope of protection of the claims.
Claims
1. A hydration inhibitor for the surface of clay minerals, wherein the structure of the hydration inhibitor for the surface of clay minerals is 【Transformation 3】 A hydration inhibitor for the surface of a clay mineral, characterized in that it is such.
2. A method for preparing a hydration inhibitor for clay mineral surfaces according to claim 1, comprising the following steps: Add 5 g of tert-butyl [2-(2-aminoethoxy group)ethyl]carbamate to a 100 mL one-necked flask, then add 80 mL of acetonitrile, 7.8 g of sodium carbonate, and 0.5 g of sodium iodide. Stir at room temperature for 0.5 hours, then add 2.83 g of bis(2-bromoethyl) ether. React under reflux at 70°C for 48 hours. Remove excess sodium iodide and sodium carbonate by vacuum filtration, concentrate the reaction mixture in a rotary evaporator, wash the product with petroleum ether, and dry to obtain the intermediate product. A method for preparing a clay mineral surface hydration inhibitor, characterized by adding 30 mL of saturated ethyl acetate HCl solution to the crude product to remove the Boc protecting group, stirring at room temperature for 4 hours to precipitate a large amount of white solid, and after the reaction is complete, performing vacuum filtration, retaining the filtration cake, and vacuum drying to obtain 5.22 g, i.e., the clay mineral surface hydration inhibitor.
3. The method for preparing a hydration inhibitor for the surface of a clay mineral according to claim 2, characterized in that the vacuum drying temperature is 80°C and the drying time is 12 hours.
4. Application of a clay mineral surface hydration inhibitor obtained by the method for preparing a clay mineral surface hydration inhibitor according to claim 2 or 3 in an aqueous drilling fluid.