A new sulfur removal agent for drilling fluid and a synthesis method thereof

Abstract

This invention relates to the field of oil drilling fluid treatment agents, specifically disclosing a novel desulfurizing agent for drilling fluids and its synthesis method. The key technical points are: the desulfurizing agent is a zeolite imidazole ester framework material, prepared by reacting cobalt nitrate hexahydrate and 2-methylimidazole in methanol; its X-ray diffraction pattern shows characteristic diffraction peaks at 2θ of 7.3°, 10.4°, 12.7°, 14.8°, 16.4°, 18.0°, and 24.5°; and the specific surface area of ​​the desulfurizing agent is 1952 m². 2 The pore size distribution is concentrated in the micropore region, with a pore size of less than 2 nm. This invention also provides a method for synthesizing this desulfurizing agent and its application in drilling fluid preparation. Experiments show that drilling fluid containing the desulfurizing agent of this invention achieves a breakthrough time of 842 minutes and a saturation time of 1440 minutes against hydrogen sulfide, significantly superior to existing desulfurizing agents. This invention has advantages such as simple synthesis method, good desulfurization effect, and broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of oil drilling fluid treatment agents, and more specifically, to a novel desulfurizing agent for drilling fluids and its synthesis method. Background Technology

[0002] In oil and gas drilling operations, formation fluids are often accompanied by hydrogen sulfide (H2S) gas. Hydrogen sulfide is a highly toxic and corrosive acidic gas that not only causes severe electrochemical corrosion and hydrogen embrittlement damage to drilling equipment (such as drill pipe, casing, pumps, and valves), but also leads to the deterioration of drilling fluid properties (such as decreased viscosity and increased filtration loss). More seriously, it poses a direct threat to the lives of on-site personnel. Therefore, adding a highly efficient desulfurizing agent to the drilling fluid to promptly remove infiltrated hydrogen sulfide is a key technical means to ensure drilling safety, extend equipment life, and maintain drilling fluid stability.

[0003] Currently, commonly used desulfurizing agents in drilling fluid treatment mainly include metal salt compounds such as basic zinc carbonate and ferrous gluconate. The mechanism of action of these desulfurizing agents is through the reaction of metal ions with sulfur ions to form stable metal sulfide precipitates, thereby reducing the concentration of free hydrogen sulfide in the drilling fluid. However, in practical applications, existing technologies have the following shortcomings: 1. Limited adsorption capacity and short breakthrough time. Existing desulfurizing agents, such as basic zinc carbonate and ferrous gluconate, have their active sites easily consumed during the reaction with hydrogen sulfide, leading to hydrogen sulfide breakthrough in a short period of time. According to experimental data, the hydrogen sulfide breakthrough time of the blank drilling fluid is only 34.5 minutes. Even with the addition of basic zinc carbonate or ferrous gluconate, the breakthrough time is only 150 minutes and 240 minutes, respectively, which is insufficient to meet the long-term desulfurization requirements of deep well and long-cycle drilling operations.

[0004] 2. Short saturation time and low overall desulfurization efficiency. Existing desulfurizing agents, once saturated, cannot continue to remove hydrogen sulfide, causing the drilling fluid to lose its protective capabilities in the later stages. Experimental data shows that the saturation times for basic zinc carbonate and ferrous gluconate are 737.5 minutes and 750 minutes, respectively, indicating limited overall desulfurization lifespan.

[0005] 3. Poor thermal stability and structural adjustability. Traditional metal salt desulfurizers are mostly inorganic compounds, whose microstructure is difficult to control and whose specific surface area is low, limiting their contact efficiency and reaction rate with hydrogen sulfide.

[0006] Therefore, how to develop a novel desulfurizing agent with high specific surface area, rich microporous structure, excellent thermal stability and long-term hydrogen sulfide removal has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to solve the problems of short breakthrough time, limited saturation time and low desulfurization efficiency of existing desulfurizing agents, and to provide a novel desulfurizing agent for drilling fluid with high specific surface area, rich microporous structure and good thermal stability, as well as its synthesis method.

[0008] The above-mentioned objective of the present invention is achieved as follows: One aspect of the present invention provides a novel desulfurizing agent for drilling fluids. The desulfurizing agent is a zeolite imidazole ester framework material, which is prepared by reacting cobalt nitrate hexahydrate and 2-methylimidazole in methanol solvent. The X-ray diffraction pattern has characteristic diffraction peaks at 2θ of 7.3°, 10.4°, 12.7°, 14.8°, 16.4°, 18.0°, and 24.5°.

[0009] Furthermore, the specific surface area of ​​the desulfurizing agent is 1952 m². 2 / g.

[0010] Furthermore, the pore size distribution of the desulfurizing agent is concentrated in the micropore region, with a pore size of less than 2 nm.

[0011] Another aspect of the present invention provides a method for synthesizing a novel desulfurizing agent for drilling fluids, comprising the following steps: S1. Cobalt nitrate hexahydrate and 2-methylimidazole were dissolved in methanol to obtain two solutions. S2. Mix the two solutions and stir the reaction mixture at room temperature for 1 hour. S3. Centrifuge the suspension after the reaction, discard the supernatant, wash the precipitate with methanol and repeat the centrifugation washing three times. S4. Dry and grind the washed solid product to obtain a purple powdery desulfurizer.

[0012] Furthermore, the molar ratio of cobalt nitrate hexahydrate to 2-methylimidazole in step S1 is 1:8.

[0013] Furthermore, the drying temperature in step S4 is 80°C, and the drying time is 3 hours.

[0014] Another aspect of the present invention provides the application of a novel desulfurizing agent for drilling fluids in the preparation of drilling fluids.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The desulfurizing agent provided by this invention significantly extends the breakthrough time and saturation time of hydrogen sulfide, exhibiting excellent desulfurization performance. Experimental results show that, under continuous introduction of 100 ppm hydrogen sulfide, the breakthrough time of drilling fluid containing the desulfurizing agent of this invention reaches 842 minutes, meaning that no hydrogen sulfide escape is detected for up to 14 hours; the saturation time reaches 1440 minutes, meaning that adsorption saturation is reached only after 24 hours. In comparison, the breakthrough time of existing desulfurizing agents, such as basic zinc carbonate, is only 150 minutes, and the saturation time is 737.5 minutes; the breakthrough time of ferrous gluconate is 240 minutes, and the saturation time is 750 minutes. It is evident that the desulfurizing agent of this invention improves both breakthrough time and saturation time by more than 3 times, significantly outperforming existing technologies, and can provide longer-lasting hydrogen sulfide protection for drilling operations in deep wells and complex formations.

[0016] 2. The desulfurizing agent provided by this invention possesses a high specific surface area and abundant microporous structure, providing a large number of adsorption active sites; furthermore, the desulfurizing agent synthesized by this invention is a zeolite imidazole ester framework material with a specific surface area as high as 1952 m². 2 / g, which is much higher than that of traditional metal salt desulfurizers; BET pore size analysis shows that its pore size distribution is concentrated in the micropore region (<2 nm), especially with a significant pore size distribution peak at about 0.5 nm. This microporous structure is conducive to hydrogen sulfide molecules (kinetic diameter about 0.36 nm) entering the pores and being effectively adsorbed, which greatly improves the adsorption capacity and reaction efficiency of the desulfurizer per unit mass.

[0017] 3. The desulfurizing agent provided by this invention possesses excellent thermal stability and is suitable for high-temperature downhole environments. Thermogravimetric analysis (TGA) shows that the desulfurizing agent exhibits almost no significant mass loss below 200℃, and its framework structure remains stable. Within the temperature range of 200℃ to 500℃, the organic ligands gradually decompose, demonstrating excellent thermal stability. This indicates that the desulfurizing agent of this invention can meet the requirements of drilling fluid use in high-temperature downhole environments, avoiding a decline in desulfurization performance due to thermal decomposition.

[0018] 4. The desulfurizing agent provided by the present invention has a uniform morphology and good dispersibility, which is conducive to uniform distribution in drilling fluid. SEM images show that the desulfurizing agent particles of the present invention have a polyhedral morphology, uniform size (submicron level), smooth surface, and no serious agglomeration. This uniform micromorphology helps it to be uniformly dispersed in drilling fluid, increases the probability of contact with hydrogen sulfide, and further improves the desulfurization efficiency.

[0019] 5. The desulfurizing agent provided by this invention has a simple synthesis method that is easy to industrialize. The synthesis method only requires stirring and reacting at room temperature for 1 hour. No high temperature, high pressure or special equipment is required. After centrifugation, washing, drying and grinding, the target product can be obtained. The operation is simple and the cost is low, making it suitable for large-scale industrial production.

[0020] In summary, this invention significantly improves the ability of drilling fluids to remove hydrogen sulfide by synthesizing a zeolite imidazole ester framework material with high specific surface area, microporous structure and good thermal stability. The breakthrough time and saturation time are far superior to existing desulfurizers, showing good prospects for industrial application. Attached Figure Description

[0021] Figure 1 The ingredients in this embodiment are cobalt nitrate hexahydrate and 2-methylimidazole. Figure 2 These are the cobalt nitrate solution and 2-methylimidazole solution in the embodiments of the present invention; Figure 3 In this embodiment of the invention, the solution is mixed and stirred; Figure 4 In this embodiment of the invention, centrifugation and washing are performed. Figure 5 In this embodiment of the invention, the material is dried and ground. Figure 6 This is the XRD pattern of CL-1 prepared in the embodiments of the present invention; Figure 7 This is the BET plot of CL-1 prepared in the embodiments of the present invention; Figure 8 Here is a SEM image of CL-1 prepared in an embodiment of the present invention; Figure 9 This is a TGA image of CL-1 prepared in an embodiment of the present invention; Figure 10 This is a schematic diagram illustrating the reaction between the desulfurizing agent and hydrogen sulfide in the drilling fluid according to an embodiment of the present invention; Figure 11 This is the H2S clearance curve in the embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] The implementation of the present invention will be described in detail below with reference to specific embodiments.

[0024] Example: This invention provides a novel desulfurizing agent for drilling fluids and its synthesis method, aiming to overcome the problems of short desulfurization time, limited saturation time, and low desulfurization efficiency in existing desulfurizing agents. The following are specific experimental implementations of this invention.

[0025] 1. Synthesis and Characterization of Novel Desulfurizing Agent CL-1 1.1 Experimental Materials and Equipment The materials and equipment used in the experiment are shown in Tables 1 and 2.

[0026] Table 1 Experimental Materials Table 2 Experimental Equipment 1.2 Experimental Methods (1) Preparation of solution Weigh out 5.82g of cobalt nitrate hexahydrate and 13.12g of 2-methylimidazole in a molar ratio of 1:8, and place them in two clean beakers respectively. Add an appropriate amount of methanol as a solvent and stir to dissolve them completely.

[0027] (2) Mixing and Reaction After the two solutes have completely dissolved, slowly pour the two solutions into the same container to mix them, and stir continuously with a magnetic stirrer at room temperature for 1 hour to promote a full reaction.

[0028] (3) Separation and washing After the reaction was completed, the resulting suspension was transferred to a centrifuge tube and centrifuged at 4000 rpm to achieve solid-liquid separation. The supernatant was then discarded, and methanol was added to wash the precipitate. The mixture was then centrifuged again and repeated three times to ensure that impurities were completely removed.

[0029] (4) Drying and grinding The washed solid product was transferred to a petri dish and dried in an oven at 80°C. After 3 hours, it was removed and ground with a mortar and pestle to obtain the target product as a purple powder.

[0030] 1.3 Characterization Methods (1) Using X-ray diffraction (XRD) to generate diffraction patterns in crystals, information such as phase composition, internal stress state, lattice parameters and crystal structure of the sample can be obtained. By comparing the experimentally measured XRD patterns with standard patterns, different crystal phases in the sample can be identified, and the presence of specific elements or compounds can be determined based on characteristic diffraction peaks.

[0031] (2) A pore size analyzer (BET) is used to measure the adsorption amount of gas molecules (usually nitrogen) on the surface of solid materials by measuring the adsorption amount under different relative pressures. The specific surface area of ​​the material is calculated according to the Brunauer-Emmett-Teller equation. Furthermore, the nonlocal density functional theory model (NLDFT) is used to analyze the pore size distribution map in order to accurately resolve the pore size distribution of the material and calculate its pore volume.

[0032] (3) The microscopic morphology information of the sample surface or cross section is obtained by detecting the secondary electron signal generated when the sample is bombarded by a high-energy electron beam using a scanning electron microscope (SEM). This technique can clearly present the surface structure, cross-sectional features and morphological details of the micro-regions of the sample, thus providing intuitive and reliable image evidence for analyzing the microstructural features, particle size distribution and surface roughness of the material.

[0033] (4) By obtaining the corresponding thermogravimetric curves through thermogravimetric analysis (TGA) and analyzing the experimental TGA curves, a series of key physical property parameters such as initial decomposition temperature, maximum weight loss rate temperature, and residual mass percentage can be obtained, providing an important basis for the thermal stability assessment of materials.

[0034] 1.4 Experimental Results (1) Synthesis results Methanol was added to beakers containing cobalt nitrate hexahydrate and 2-methylimidazole, respectively, and stirred until completely dissolved. The resulting solutions were pink and clear / colorless, respectively. Figure 1 , Figure 2 As shown; mix the solutions in the two beakers. The solution immediately turns purple. Place it on a magnetic stirrer and stir continuously to ensure a complete reaction. Figure 3 As shown; transfer the suspension to a centrifuge tube, centrifuge, discard the supernatant, add methanol to wash and centrifuge again, repeat 3 times, as shown. Figure 4 As shown; transfer the washed purple filter cake to a petri dish, place it in an oven to dry, and grind it after drying to obtain a uniform CL-1 powder sample, as shown. Figure 5 As shown.

[0035] (2) Characterization results 1) XRD analysis like Figure 6 As shown in the figure, distinct characteristic diffraction peaks appear in the low-angle region (such as around 7-15° for 2θ). The positions and relative intensities of these characteristic peaks are consistent with the characteristics of the standard XRD pattern of CL-1 (7.3°, 10.4°, 12.7°, 14.8°, 16.4°, 18.0°, 24.5°, etc.). The sharpness and high intensity of the characteristic peaks indicate that the prepared CL-1 has good crystallinity, a relatively regular crystal structure, and an ordered spatial arrangement of atoms or molecules. Throughout the entire test angle range, no obvious impurity diffraction peaks were observed besides the characteristic peaks of CL-1, indicating that the prepared CL-1 has high purity and is free from a large number of other crystalline phases or amorphous impurities.

[0036] 2) BET analysis (using the NLDFT method) The synthesized CL-1 had a specific surface area of ​​1952 m² / g. For example... Figure 7As shown in the curves, the pore size of CL-1 is mainly concentrated in a small range, with a very significant peak around 0.5 nm, indicating the presence of a large number of pores of this size. This is consistent with the characteristic of CL-1 as a zeolite imidazole ester framework material, possessing a microporous structure. Besides the main peak around 0.5 nm, there is also a relatively small peak at slightly larger pore sizes (close to 1 nm), indicating the presence of a small number of pores of this size. Overall, the pore size distribution is relatively concentrated in the microporous region (less than 2 nm). As the pore size increases, the pore volume gradually increases. After the pore size reaches a certain value (around 1 nm), the pore volume tends to plateau and no longer increases significantly. This indicates that the pores of CL-1 are mainly concentrated in the microporous region, and the number of pores is very small when the pore size exceeds the microporous range.

[0037] 3) SEM analysis like Figure 8 As shown, CL-1 exhibits a polyhedral particle morphology with relatively uniform particle size and good overall dispersion, without severe agglomeration. This is beneficial for its application in scenarios such as catalysis and gas adsorption, as the uniform morphology and good dispersion help provide more active sites and contact area. Based on the scale bar (2 μm) in the figure, the size of CL-1 particles can be roughly determined to be at the submicron level. The particle surface appears relatively regular and smooth, without obvious defects or porous structures, which is consistent with the relatively ordered crystal structure characteristics of CL-1 as a zeolite imidazole ester framework material.

[0038] like Figure 9 As shown, in the low-temperature stage (30℃~200℃), there is almost no significant mass loss, and the mass remains above 94%. In this temperature range, only the physical water adsorbed on the surface or a small amount of residual solvent is lost, and the framework structure has not yet decomposed. In the medium-temperature stage (200℃~500℃), significant mass loss begins to appear, decreasing from 94% to 71%. The CL-1 organic ligand continues to decompose, and the organic components in the ligand escape in gaseous form, and the framework begins to disintegrate. In the high-temperature stage (500℃~800℃), the mass drops sharply, eventually settling at 27.5%. The organic components are completely removed, leaving only cobalt oxides.

[0039] 2. Evaluation of the desulfurization effect of the new desulfurizing agent CL-1 2.1 Experimental Methods The novel desulfurizing agent CL-1 and commonly used desulfurizing agents were evaluated in the laboratory. The desulfurizing agents were added to the drilling fluid, and their desulfurization effect was tested through pollution experiments. Figure 10As shown, connect the experimental testing apparatus, remove the glass sieve plate from the absorption bottle, pour an appropriate amount of sample into the absorption bottle, insert the glass tube with the glass sieve plate and another glass tube into the rubber stopper, then insert them into the absorption bottle and tighten the rubber stopper. Continuously introduce H2S at a concentration of 100 ppm at the inlet of the experimental apparatus and start timing. Use an H2S detector with a minimum detection limit of 0.1 ppm to measure the concentration of H2S gas escaping from the outlet of the absorption bottle with the glass sieve plate per minute until it reaches or approaches the upper limit of the gas detector's measurement range.

[0040] 2.2 Experimental Results The breakthrough time and saturation time obtained from the experiments are shown in Table 3. The H2S breakthrough curve is shown in Table 3. Figure 11 As shown, the drilling fluid without desulfurizer (blank group) had very low H2S removal capacity, while the drilling fluid containing CL-1 showed the most significant H2S removal capacity. The breakthrough time of the blank group was 34.5 min, and the saturation time was 325 min; the drilling fluid containing basic zinc carbonate had a hydrogen sulfide outlet concentration of 1 ppm at 150 min, and reached saturation at 737.5 min; while the breakthrough time of ferrous gluconate was 240 min, and the time to reach saturation of hydrogen sulfide outlet concentration was 750 min; the drilling fluid containing CL-1 did not detect hydrogen sulfide from the start of the experiment until 842 min, completely absorbing the hydrogen sulfide that had invaded the drilling fluid, after which hydrogen sulfide began to flow out, until the hydrogen sulfide outlet concentration reached 100 ppm at 1440 min.

[0041] Table 3 Desulfurizer Breakthrough Time and Saturation Time Through the above-described experimental implementation of this invention, the synthesis, structural characterization, and desulfurization performance evaluation of CL-1, a desulfurizing agent for drilling fluid, were fully demonstrated. Specifically, CL-1, a purple powder-like zeolite imidazole ester framework material, was successfully prepared by reacting cobalt nitrate hexahydrate with 2-methylimidazole in methanol solvent at room temperature for 1 hour, followed by centrifugation, washing, drying, and grinding. The synthesis method is simple, mild, and easy for industrial production. Furthermore, the product was systematically characterized by XRD, BET, SEM, and TGA, confirming its typical zeolite imidazole ester framework structure. The characteristic XRD diffraction peaks were located at 2θ of 7.3°, 10.4°, 12.7°, 14.8°, 16.4°, 18.0°, and 24.5°, which highly matched the standard spectra. BET testing showed that its specific surface area was as high as 1952 m². 2The pore size distribution is concentrated in the microporous region (<2 nm), with a significant pore size distribution peak at approximately 0.5 nm. SEM shows that the particles exhibit a polyhedral morphology, uniform size, and no obvious agglomeration. TGA confirms its good thermal stability below 200℃. Furthermore, the obtained CL-1 was applied to drilling fluid for hydrogen sulfide removal. The results showed that the drilling fluid containing CL-1 achieved a breakthrough time of 842 minutes and a saturation time of 1440 minutes for 100 ppm hydrogen sulfide, significantly superior to basic zinc carbonate (breakthrough time 150 minutes, saturation time 737.5 minutes) and ferrous gluconate (breakthrough time 240 minutes, saturation time 750 minutes). In summary, this invention successfully synthesized a novel zeolite imidazole ester framework material, CL-1, with a specific crystal structure, high specific surface area, microporous characteristics, and good thermal stability. Its breakthrough and saturation times in drilling fluid desulfurization applications far exceed those of existing technologies. Moreover, the synthesis method is simple and easy to implement, demonstrating multiple innovations and significant advancements in product structure, preparation method, and application effects.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A novel desulfurizing agent for drilling fluids, characterized in that, The desulfurizing agent is a zeolite imidazole ester framework material, which is prepared by reacting cobalt nitrate hexahydrate and 2-methylimidazole in methanol solvent. The X-ray diffraction pattern has characteristic diffraction peaks at 2θ of 7.3°, 10.4°, 12.7°, 14.8°, 16.4°, 18.0°, and 24.5°.

2. The novel desulfurizing agent for drilling fluid according to claim 1, characterized in that, The specific surface area of ​​the desulfurizing agent is 1952 m². 2 / g.

3. The novel desulfurizing agent for drilling fluid according to claim 1, characterized in that, The pore size distribution of the desulfurizing agent is concentrated in the micropore region, with a pore size of less than 2 nm.

4. A method for synthesizing a novel desulfurizing agent for drilling fluid according to claim 1, characterized in that, Includes the following steps: S1. Cobalt nitrate hexahydrate and 2-methylimidazole were dissolved in methanol to obtain two solutions. S2. Mix the two solutions and stir the reaction mixture at room temperature for 1 hour. S3. Centrifuge the suspension after the reaction, discard the supernatant, wash the precipitate with methanol and repeat the centrifugation washing three times. S4. Dry and grind the washed solid product to obtain a purple powdery desulfurizer.

5. The synthesis method according to claim 4, characterized in that, The molar ratio of cobalt nitrate hexahydrate to 2-methylimidazole in step S1 is 1:

8.

6. The synthesis method according to claim 4, characterized in that, The drying temperature in step S4 is 80°C and the drying time is 3 hours.

7. The application of the novel desulfurizing agent for drilling fluid according to claim 1 in the preparation of drilling fluid.

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