Carbon nanotube lubricant for drilling fluid as well as preparation method and application of carbon nanotube lubricant

Abstract

The invention relates to a carbon nanotube lubricant for drilling fluid as well as a preparation method and application of the carbon nanotube lubricant. The carbon nanotube lubricant mainly comprises a nitrogen-doped carbon nanotube and metal nanoparticles compounded at the end part of the nitrogen-doped carbon nanotube, the metal is one of Fe, Co and Ni. The carbon nanotube lubricant provided by the invention has stable adsorbability, can be effectively adsorbed on a drilling tool, a casing pipe and rock, and in addition, the carbon nanotube lubricant contains a large number of carbon nanotubes, so that a boundary film is easily generated on the drilling tool or the casing pipe, and the extreme pressure wear resistance is enhanced; under the condition of low dosage, the extreme pressure lubrication coefficient reduction rate can reach 85%, the mud cake adhesion coefficient reduction rate can reach 62%, and the lubricating oil has good temperature resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of carbon nanotube lubricant for drilling fluid, preparation method and its application, belong to oil exploitation drilling fluid technical field. BACKGROUND

[0002] Pressure differential sticking accident often occurs in the process of oil drilling, the most effective and commonly used process measures to prevent pressure differential sticking is to add excellent performance lubricant in drilling fluid, improve the lubricity of drilling fluid and mud cake surface;At the same time, with the increase of deep well, ultra-deep well, high angle well, directional well and horizontal well and other complex wells, higher requirements are put forward for downhole friction control. For example, the existence of a large number of weighting material leads to poor lubricity of high density drilling fluid, high friction has become one of the core problems restricting the development of water-based drilling fluid under the new situation.

[0003] Lubricant is an important additive in drilling fluid, which can improve the lubricating property of drilling fluid, reduce the downhole friction, and improve the rheological property and filtration property of drilling fluid, and improve the rock breaking efficiency. At present, the drilling fluid lubricant mainly includes two types of liquid lubricant and solid lubricant. The liquid lubricant is the most studied and most widely used lubricant, which mainly includes asphalt lubricant, diesel-based lubricant, mineral oil-based lubricant, vegetable oil-based lubricant, polyhydric alcohol lubricant, synthetic ester lubricant, high polymer material and surfactant type lubricant. The Chinese invention patent with the application publication number CN115057772A discloses a preparation method of drilling fluid lubricant, which specifically discloses that the polyhydric alcohol and the organic acid with a molar ratio of 0.005-0.015:0.02-0.04 are uniformly mixed in a solvent to generate esterification reaction, and then the solvent, small molecule acid and water in the esterification product are removed to obtain a viscous lubricant for drilling fluid. The lubricant has good lubricating effect, but it is an ester lubricant, which is unstable and prone to hydrolysis under high temperature and high salt, thereby restricting its application in salt water drilling fluid and deep well ultra-deep well. The Chinese invention patent with the application publication number CN105567177A discloses a preparation method of drilling lubricant, which specifically discloses that the vegetable oil is poured into a three-necked flask, diethylene glycol and ethanolamine are added, and the temperature is controlled at 110-130 DEG C while stirring and heating, and the reaction time is 2.5 h to generate a light yellow liquid; then sulfur is added, the reaction temperature is adjusted to 150 DEG C, and the reaction is continued for 4.5 h to generate a dark yellow viscous liquid; 15% of oil-soluble resin and 6% of graphite powder are added, and the dark yellow viscous liquid is blackened after mixing, stirring and uniform mixing at 75 DEG C, thereby obtaining the drilling fluid lubricant. The lubricant prepared by the method has low fluorescence level, good lubricating property, no toxicity, biodegradability, reproducibility and environmental friendliness, but the refined mineral oil, poly-alpha-olefin, vegetable oil and modified vegetable oil products generally have the disadvantages of affecting the rheological property of drilling fluid, easy foaming and easy consumption. Therefore, the solid lubricant which is not affected by the external environment in the harsh downhole environment such as high temperature, high salt and extreme pressure is paid more and more attention. The solid lubricant products mainly include synthetic polymer balls, glass balls, ceramic balls and graphite particles with lamellar structure, and the above solid lubricants have certain lubricating effect in the drilling fluid.

[0004] However, the lubricating effect of the nanoscale graphite solid lubricant and the commonly used graphite solid lubricant for drilling fluid in the prior art still needs to be improved. SUMMARY

[0005] The first object of the present application is to provide a carbon nanotube lubricant for drilling fluid, so as to solve the problem of poor lubricating effect of the graphite solid lubricant for drilling fluid in the prior art.

[0006] The second object of the present application is to provide a preparation method of the carbon nanotube lubricant for drilling fluid, so as to solve the problem of poor lubricating effect of the graphite solid lubricant product prepared in the prior art.

[0007] The third object of the present application is to provide an application of the carbon nanotube lubricant for drilling fluid in drilling fluid, so as to solve the problem of poor lubricating effect of the solid lubricant in the drilling fluid in the prior art.

[0008] In order to achieve the above-mentioned objects, the technical scheme of the carbon nanotube lubricant for drilling fluid in the present application is as follows:

[0009] The carbon nanotube lubricant for drilling fluid mainly comprises nitrogen-doped carbon nanotubes and metal nanoparticles compounded at the end of the nitrogen-doped carbon nanotubes; and the metal is one of Fe, Co and Ni.

[0010] The above-mentioned technical scheme has the beneficial effects that the carbon nanotube lubricant for drilling fluid is an opening-up invention, the carbon nanotube lubricant for drilling fluid provided by the present application has rich nitrogen elements and Fe, Co or Ni metal elements, can be effectively adsorbed on drilling tools, casings and rocks, contains a large amount of carbon nanotubes, is easy to generate a boundary film on the surface of the drilling tools and casings, enhances the anti-wear property of the lubricant under a certain pressure, can effectively improve the drilling speed, and can prevent complex conditions such as mud ball from occurring, thereby providing a new and effective material for the solid lubricant for drilling fluid. The transition metal Fe, Co or Ni has a high carbon solubility, acts as a deposition center of graphite carbon, and is beneficial to promoting the growth of the carbon nanotubes; further, the present application proves by experiments that when the metal coated in the carbon nanotubes is Co, the reduction rates of the extreme pressure lubrication coefficient and the mud cake adhesion coefficient are more significant, and the lubricating effect is more excellent.

[0011] As a further improvement, the content of the metal in the carbon nanotube lubricant is 5-10%, and the content of nitrogen is 2-21%.

[0012] The above-mentioned technical scheme has the beneficial effects that the content of the metal and nitrogen is within the above-mentioned range, and the content of the carbon nanotubes in the product is high.

[0013] Further preferably, the content of the metal in the carbon nanotubes is 7%, and the content of nitrogen is 6%.

[0014] In order to achieve the above-mentioned objects, the technical scheme of the preparation method of the carbon nanotube lubricant for drilling fluid in the present application is as follows:

[0015] The preparation method of the carbon nanotube lubricant for drilling fluid comprises the following steps: melamine and a metal salt are subjected to a precipitation reaction in water in the presence of an organic acid precipitant; and the solid obtained by the precipitation reaction is calcined under an inert atmosphere.

[0016] The beneficial effects of the above technical solutions are that the preparation method of the carbon nanotube lubricant for drilling fluid is an opening invention, in the carbonization process, the organic acid provides a carbon source, the melamine provides a nitrogen source, and the transition metal provided by the metal salt has a high carbon solubility, which promotes the growth of nanotubes as a deposition center of graphite carbon, and finally forms nitrogen-doped carbon nanotubes. The preparation method of the carbon nanotube lubricant for drilling fluid has the advantages of simple process and high utilization rate of raw materials.

[0017] As a further improvement, the method comprises the following steps:

[0018] S1, dissolving melamine in an aqueous solution of a metal salt to obtain solution A;

[0019] S2, reacting the organic acid precipitant with the solution A of step S1 at 60-100°C, and obtaining solid B after cooling, centrifugation, washing and drying;

[0020] S3, calcining the solid B of step S2 under an inert atmosphere at a temperature of 600-900°C, and cooling to obtain the product.

[0021] The beneficial effects of the above technical solutions are that the carbon nanotube lubricant for drilling fluid can be efficiently prepared according to the above operation process.

[0022] As a further improvement, the metal salt is one of chloride, nitrate and sulfate.

[0023] The beneficial effects of the above technical solutions are that the water solubility of chloride, nitrate and sulfate is good, and no other by-products are generated after reaction.

[0024] As a further improvement, the mass ratio of melamine, metal salt and water is 1-3:0.4-1:50-100.

[0025] The beneficial effects of the above technical solutions are that the addition of melamine, metal salt and water according to the above mass ratio can ensure that the content of metal and the content of nitrogen doping in the final product are within the preset range.

[0026] As a further improvement, the organic acid precipitant is one of oxalic acid, citric acid, tartaric acid, malic acid, ascorbic acid, benzoic acid, succinic acid and salicylic acid.

[0027] The beneficial effects of the above technical solutions are that the above organic acid precipitant has good compatibility with the system, and the utilization rate of carbon atoms is high in the subsequent carbonization process.

[0028] As a further improvement, the mass ratio of the organic acid precipitant to melamine is 0.6-2:1-3.

[0029] The beneficial effects of the above technical solution are that the mass ratio of the organic acid precipitant to melamine is used in the precipitation reaction, which helps the efficient performance of the precipitation reaction.

[0030] To achieve the above-mentioned purpose, the technical solution of the application is that a carbon nanotube lubricant for drilling fluid is applied in drilling fluid.

[0031] A carbon nanotube lubricant for drilling fluid is applied in drilling fluid.

[0032] The beneficial effects of the above technical solution are that the application of the carbon nanotube lubricant for drilling fluid is an opening invention. The experiment proves that the extreme pressure lubrication coefficient reduction rate of the carbon nanotube lubricant for drilling fluid can reach 85%, the mud cake adhesion coefficient reduction rate can reach 62%, and it has good temperature resistance, which can effectively reduce the friction between the well wall and the drilling tool, prevent sticking and reduce the mud ball bit. At the same time, the particle size of the carbon nanotube lubricant is small, which can effectively fill the micro gap of the friction surface between the well wall and the drilling tool, further increase its lubrication performance, and has no pollution to the environment and little damage to the reservoir.

[0033] As a further improvement, the mass concentration of the carbon nanotube lubricant for drilling fluid in the drilling fluid is 0.5-3%.

[0034] The beneficial effects of the above technical solution are that the carbon nanotube lubricant can achieve good lubrication effect when added to the drilling fluid in the above mass concentration range, which can reduce the production cost. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The flow chart of the preparation method of the carbon nanotube lubricant for drilling fluid of the application is shown.

[0036] Figure 2 The scanning electron microscope image of the carbon nanotube lubricant prepared in Example 2 of the application is shown. DETAILED DESCRIPTION

[0037] The particle size of the existing drilling fluid solid carbon-based lubricant is micron or sub-micron, which is difficult to effectively fill the micro gap of the friction surface, while the nano particles can deposit and effectively fill the micro gap of the rough friction surface of the metal, forming a protective film between the friction surfaces, effectively reducing the friction coefficient of the friction surface and reducing wear. Therefore, the nitrogen-doped carbon nanotube coated with metal particles is added to the drilling fluid as a lubricant, and the experiment proves that the extreme pressure lubrication coefficient reduction rate of the nitrogen-doped carbon nanotube coated with metal particles can reach 85%, the mud cake adhesion coefficient reduction rate can reach 62%, and it has good temperature resistance.

[0038] The preparation method of the carbon nanotube lubricant for drilling fluid of the present application is shown in the following detailed process. Figure 1

[0039] The present application will be further described in conjunction with the specific embodiments. It should be noted that the embodiments described below or the technical features thereof can be combined to form new embodiments without conflict. The equipment and materials used can be purchased from the market or commonly used in the art. The methods described in the following examples are conventional methods in the art unless otherwise specified.

[0040] In the following examples, the experimental operations are conventional operations in the art unless otherwise specified.

[0041] In the following examples, the raw materials used are conventional commercial products in the art unless otherwise specified.

[0042] First, the specific embodiments of the carbon nanotube lubricant for drilling fluid and the preparation method thereof of the present application are described.

[0043] Example 1

[0044] The carbon nanotube lubricant for drilling fluid of this embodiment is composed of nitrogen-doped carbon nanotubes and metal nanoparticles complexed at the end of the nitrogen-doped carbon nanotubes. The content of metal in the carbon nanotube lubricant is 6.3% and the content of nitrogen is 4.3% by scanning electron microscope energy spectrum analysis. The specific preparation method is as follows:

[0045] 0.507g FeCl2 was dissolved in a flask containing 60mL distilled water, 1.0g melamine was added, heated and stirred to 100℃, the sample was completely dissolved, 1.8g tartaric acid precipitant was added, stirred and refluxed at 90℃ for 2h, cooled and centrifuged, the sample was washed with distilled water, and dried at 100℃ for 8h to obtain a solid powder. The solid powder was heated to 800℃ at a rate of 4℃ / min under nitrogen atmosphere and kept for 2h. After the reaction was completed, the sample was taken out of the muffle furnace, which was the final product. The sample was labeled as sample 1.

[0046] Example 2

[0047] The carbon nanotube lubricant for drilling fluid of this embodiment is composed of nitrogen-doped carbon nanotubes and metal nanoparticles complexed at the end of the nitrogen-doped carbon nanotubes. The content of metal in the carbon nanotube lubricant is 6.7% and the content of nitrogen is 5.6% by scanning electron microscope energy spectrum analysis. The specific preparation method is as follows:

[0048] ​Example 1

[0049] The sample 2 was placed under a scanning electron microscope and observed, as shown in Figure 2 From the figure, it can be seen that the prepared sample is a tubular structure, and the metal nanoparticles are at the end of the carbon nanotube.

[0050] Example 3

[0051] The carbon nanotube lubricant for drilling fluid of the present example is composed of nitrogen-doped carbon nanotubes and metal nanoparticles compounded at the end of the nitrogen-doped carbon nanotubes. Through scanning electron microscope energy spectrum analysis, the content of metal in the carbon nanotube lubricant is 9.2%, and the content of nitrogen is 2.3%. The specific preparation method is as follows:

[0052] The sample 2 was placed under a scanning electron microscope and observed, as shown in

[0053] Example 4

[0054] The carbon nanotube lubricant for drilling fluid of the present example is composed of nitrogen-doped carbon nanotubes and metal nanoparticles compounded at the end of the nitrogen-doped carbon nanotubes. Through scanning electron microscope energy spectrum analysis, the content of metal in the carbon nanotube lubricant is 5.1%, and the content of nitrogen is 20.9%. The specific preparation method is as follows:

[0055] Dissolve 0.55g of Ni(NO₃)₂ in a flask containing 100mL of distilled water. Add 0.80g of melamine and heat with stirring to 100°C until the sample is completely dissolved. Add 0.9g of citric acid precipitant and reflux at 100°C with stirring for 2 hours. Cool and centrifuge, wash the sample with distilled water, and dry at 100°C for 8 hours to obtain a solid powder. Under a nitrogen atmosphere, heat the powder to 600°C at a rate of 3°C / min and hold for 5 hours. After the reaction is complete, remove the sample from the muffle furnace to obtain the final product, labeled Sample 4.

[0056] Example 5

[0057] The carbon nanotube lubricant for drilling fluid in this embodiment is composed of nitrogen-doped carbon nanotubes and metal nanoparticles composited at the ends of the nitrogen-doped carbon nanotubes. Scanning electron microscopy (SEM) analysis revealed a metal content of 6.7% and a nitrogen content of 11.9%. The specific preparation method is as follows:

[0058] Dissolve 0.46g of Ni(SO4)2 in a flask containing 50mL of distilled water, add 2.60g of melamine, and heat with stirring to 100°C until the sample is completely dissolved. Add 0.67g of malic acid precipitant, stir and reflux at 80°C for 4 hours, cool and centrifuge, wash the sample with distilled water, and dry at 100°C for 8 hours to obtain a solid powder. Under a nitrogen atmosphere, heat this solid powder at 4°C / min to 800°C and hold for 2 hours. After the reaction is complete, remove the sample from the muffle furnace to obtain the final product, labeled Sample 5.

[0059] Example 6

[0060] The carbon nanotube lubricant for drilling fluid in this embodiment is composed of nitrogen-doped carbon nanotubes and metal nanoparticles composited at the ends of the nitrogen-doped carbon nanotubes. Scanning electron microscopy (SEM) analysis revealed a metal content of 7.2% and a nitrogen content of 6.3%. The specific preparation method is as follows:

[0061] Dissolve 0.60 g of CoCl₂ in 100 mL of distilled water in a flask. Add 2.40 g of melamine and heat with stirring to 100°C until the sample is completely dissolved. Add 1.22 g of benzoic acid precipitant and reflux at 80°C with stirring for 4 hours. Cool and centrifuge, wash the sample with distilled water, and dry at 100°C for 8 hours to obtain a solid powder. Under a nitrogen atmosphere, heat this solid powder at a rate of 3°C / min to 800°C and hold for 2 hours. After the reaction is complete, remove the sample from the muffle furnace to obtain the final product, labeled Sample 6.

[0062] 2. Comparative Example

[0063] Comparative Example 1

[0064] The comparative example is a graphite solid lubricant obtained by grinding, flotation, drying and secondary fine grinding of graphite ore through a ball mill.

[0065] Comparative Example 2

[0066] The comparative example is a commercially available graphite solid lubricant for drilling fluid.

[0067] Comparative Example 3

[0068] The comparative example is a commercially available carbon nanotube with a GMPCC code XW3080685668.

[0069] III. Application of the Carbon Nanotube Lubricant for Drilling Fluid in Drilling Fluid

[0070] Experimental Example 1

[0071] The lubricating effect of the carbon nanotube lubricant for drilling fluid of the present application in the drilling fluid was evaluated.

[0072] The drilling fluid base paste was prepared by adding 0.7 g of anhydrous sodium carbonate and 16 g of bentonite to 400 g of distilled water while stirring, continuing to stir for 30 min, then sealing and hydrating for 16 h, and obtaining the drilling fluid base paste after the end of the standing time.

[0073] The carbon nanotube lubricant for drilling fluid of the above examples 1-6 and the solid lubricant of the above comparative examples 1-2 were mixed with the above base paste, and after high-speed stirring, the performance evaluation at room temperature and after aging was carried out by the extreme pressure lubrication coefficient determination method (reference standard Q / SH CG0176-2023) and the mud cake adhesion coefficient determination method (reference standard Q / SY 17088-2016). The aging condition was that the base paste and the sample mixture were placed at 190℃ for 16 h. The additive amount and the lubricating effect of each lubricant are shown in Table 1.

[0074] Table 1 Lubricating effect evaluation results

[0075]

[0076] As can be seen from the table, compared with the nanoscale graphite solid lubricant, the extreme pressure lubrication coefficient reduction rate and the mud cake adhesion coefficient reduction rate of the carbon nanotube lubricant for drilling fluid of the present application are significantly improved with less additive amount. Compared with the commercially available graphite solid lubricant for drilling fluid, the extreme pressure lubrication coefficient reduction rate of the carbon nanotube lubricant for drilling fluid of the present application is significantly improved, and the mud cake adhesion coefficient reduction rate is slightly improved, with little difference, but the additive amount of the sample is much smaller than that of the commercially available graphite solid lubricant for drilling fluid. The comparative experimental evaluation results show that the carbon nanotube lubricant for drilling fluid provided by the present application has excellent effect.

[0077] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the embodiments of the present application, which should be covered in 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 carbon nanotube lubricant for drilling fluid, characterized in that: The carbon nanotube lubricant mainly comprises nitrogen-doped carbon nanotubes and metal nanoparticles compounded at the ends of the nitrogen-doped carbon nanotubes; the metal is one of Fe, Co and Ni.

2. The carbon nanotube lubricant for drilling fluid according to claim 1, characterized in that: The metal content in the carbon nanotube lubricant is 5-10%, and the nitrogen content is 2-21%.

3. A method for preparing a carbon nanotube lubricant for drilling fluid according to claim 1 or 2, characterized in that: Melamine and a metal salt are subjected to a precipitation reaction in water in the presence of an organic acid precipitant, and a solid obtained by the precipitation reaction is calcined under an inert atmosphere.

4. The method for preparing a carbon nanotube lubricant for drilling fluid according to claim 3, wherein: The steps include: S1. Melamine is dissolved in a metal salt aqueous solution to obtain solution A; S2, reacting the organic acid precipitant with the solution A described in step S1 at 60-100° C., cooling, centrifuging, washing, and drying to obtain solid B; S3. The solid B described in step S2 is heated to 600-900° C. and calcined under an inert atmosphere, and then cooled.

5. The method for preparing a carbon nanotube lubricant for drilling fluid according to claim 3 or 4, characterized in that: The metal salt is one of chloride, nitrate and sulfate.

6. The method for preparing a carbon nanotube lubricant for drilling fluid according to any one of claim 5, wherein: The mass ratio of the melamine, the metal salt and the water is 1-3:0.4-1:50-100.

7. The method for preparing a carbon nanotube lubricant for drilling fluid according to claim 3 or 4, characterized in that: The organic acid precipitant is one of oxalic acid, citric acid, tartaric acid, malic acid, ascorbic acid, benzoic acid, succinic acid and salicylic acid.

8. The method for preparing a carbon nanotube lubricant for drilling fluid according to any one of claim 7, wherein: The mass ratio of the organic acid precipitant to melamine is 0.6-2:1-3.

9. Use of the carbon nanotube lubricant for drilling fluid according to claim 1 or 2 in drilling fluid.

10. Use of the carbon nanotube lubricant for drilling fluid according to claim 9 in drilling fluid, characterized in that: The mass concentration of the carbon nanotube lubricant for drilling fluid in the drilling fluid is 0.5-3%.

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