Lubricant composition and use

Abstract

A lubricant composition, comprising a solid lubricant and a liquid lubricant, wherein the water contact angle of the solid lubricant is greater than 90°; and the extreme-pressure lubrication coefficient of the liquid lubricant is less than 0.15. The solid lubricant is modified graphite, and a modifier comprises at least one of hydroxyl-containing nanoparticles and a silane coupling agent. The lubricant composition has the advantages of high temperature resistance, high pressure resistance, and resistance to saturated salt contamination, and can significantly reduce the extreme-pressure lubrication coefficient of drilling fluid.

Description

Lubricant composition and application

[0001] The present application claims priority to the Chinese patent application No. 2024111329247, filed on August 16, 2024, and entitled "A lubricant composition and application", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application belongs to the field of drilling fluid in the oil drilling industry, and specifically relates to a lubricant composition and application. BACKGROUND

[0003] In the oil drilling industry, horizontal well drilling technology can increase the contact area of the wellbore and the reservoir, which is beneficial to improve the single well production and realize the transformation from multiple wells with low production to fewer wells with high production. However, in the process of drilling a horizontal well, the drilling tool is tightly attached to the well wall under the action of gravity, which increases the contact area between the drilling tool and the formation, resulting in a significant increase in frictional resistance during drilling. At the same time, with the continuous increase in the extension length of the horizontal well and the significant increase in the complexity of the oil and gas burial environment, extremely strict requirements are put forward for the extreme pressure lubrication performance of the drilling fluid under the conditions of high temperature, high density, and high salinity.

[0004] Lubricant is a key treatment agent for improving the lubrication performance of drilling fluid. Existing lubricants are mainly divided into two categories: solid lubricants and liquid lubricants. The solid lubricant converts dry friction between friction pairs into rolling friction or interlayer sliding of lamellar solid to reduce friction, which has the advantages of strong temperature resistance, good pressure resistance, and excellent compatibility in drilling fluid. However, due to the fact that the friction form is still solid-solid friction, the improvement degree of lubrication effect is limited. The liquid lubricant can convert dry friction between friction pairs into lubricating film or friction between nonpolar groups of lubricants, which has excellent friction reduction effect. However, the structure of the lubricating film is destroyed under high temperature and extreme pressure, and the adsorption amount of the lubricant on the surface of barite is too large under high density, which limits the adsorption amount on the friction pair interface, resulting in lubrication failure.

[0005] How to overcome the existing problems of lubricants and develop a lubricant that can improve the extreme pressure lubrication performance of drilling fluid under high temperature, high density, and high salinity is an important research direction at present. SUMMARY

[0006] The present application provides a lubricant composition, which has the advantages of high temperature resistance, high pressure resistance, and saturation salt pollution resistance, and can significantly reduce the extreme pressure lubrication coefficient of drilling fluid.

[0007] The present application also provides a drilling fluid with a low extreme pressure lubrication coefficient.

[0008] The first aspect of the present application provides a lubricant composition, which comprises a solid lubricant and a liquid lubricant, and the water contact angle of the solid lubricant is > 90°.

[0009] The extreme pressure lubrication coefficient of the liquid lubricant is less than 0.15.

[0010] The solid lubricant is modified graphite, and the modifier comprises at least one of hydroxyl-containing nanoparticles and a silane coupling agent.

[0011] The lubricant composition as described above, wherein the solid lubricant has a roughness of 10-400 nm.

[0012] The lubricant composition as described above, wherein the solid lubricant has a surface energy of less than 54.8 mN·m.

[0013] The lubricant composition as described above, wherein the liquid lubricant comprises a fatty acid derivative and a non-ionic surfactant.

[0014] The lubricant composition as described above, wherein the fatty acid derivative comprises at least one of a fatty acid ester, a fatty acid amide, a sulfated fatty acid ester, a sulfated fatty acid amide, a fatty acid amide phosphate, a fatty acid polyoxyethylene ether, and a fatty acid polyoxypropylene ether.

[0015] The lubricant composition as described above, wherein the non-ionic surfactant comprises at least one of a Span and a Tween.

[0016] The lubricant composition as described above, further comprising at least one of a mineral oil and a thickening agent.

[0017] The mineral oil accounts for 10-50% by volume in the lubricant composition.

[0018] The thickening agent accounts for 1-5% by mass in the lubricant composition.

[0019] The lubricant composition as described above, wherein the modified graphite is prepared by a preparation method comprising the following steps:

[0020] Dispersing graphite and a cationic surfactant into a solvent to obtain a graphite dispersion;

[0021] Adjusting the pH of the graphite dispersion to 10-11 and the temperature to 40-60℃, adding hydroxyl-containing nanoparticles and / or a silane coupling agent, and reacting for 4-6 h.

[0022] The lubricant composition as described above, wherein the mass ratio of the graphite, the cationic surfactant, the hydroxyl-containing nanoparticles, and the silane coupling agent is (8-10):(0.1-0.5):(0-2):(0-1).

[0023] The second aspect of the present application provides a drilling fluid, comprising the above lubricant composition and a conventional drilling fluid.

[0024] Further, the ratio of the lubricant composition to the quality of the conventional drilling fluid is 0.5% to 10%.

[0025] The present application provides a lubricant composition comprising a solid lubricant and a liquid lubricant, by controlling the water contact angle of the solid lubricant, the solid lubricant has suitable hydrophobic properties, when combined with the liquid lubricant having a specific extreme pressure lubrication coefficient, the adhesion of the liquid phase lubricant on the surface of the hydrophobic solid lubricant in the water phase environment can be enhanced, so as to play the solid-liquid synergistic lubrication performance. The lubricant composition of the present application has the advantages of high temperature resistance, high pressure resistance, and saturation salt pollution resistance, etc., and can significantly reduce the extreme pressure lubrication coefficient of the drilling fluid. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0027] Fig. 1 is a scanning electron microscope graph of the modified graphite in the embodiment 1 of the present application at 1500 times magnification;

[0028] Fig. 2 is a scanning electron microscope graph of the graphite in the embodiment 1 of the present application at 1500 times magnification. DETAILED DESCRIPTION

[0029] The first aspect of the present application provides a lubricant composition comprising a solid lubricant and a liquid lubricant, the water contact angle of the solid lubricant is > 90°;

[0030] The extreme pressure lubrication coefficient of the liquid lubricant is < 0.15;

[0031] The solid lubricant is modified graphite, and the modifier comprises at least one of a hydroxyl-containing nanoparticle and a silane coupling agent.

[0032] After the solid lubricant is adsorbed on the interface of the friction pair, a dimple structure can be constructed. The dimple structure can store the liquid lubricant on one hand, under extreme pressure conditions, the surface of the drilling tool contacts with the convex body, forming a closed space for the liquid lubricant, the liquid lubricant is stored in the above-mentioned closed space, thereby playing the effect of preventing the liquid lubricant from overflowing from the surface of the friction pair under extreme pressure. By using the above method, the occurrence stability of the lubricant composition between the interfaces of the friction pair under high temperature and extreme pressure conditions can be comprehensively improved, and the friction between the drilling tool and the formation is converted into fluid lubrication between the immersed liquid phase lubricant and the solid lubricant.

[0033] The water contact angle of the solid lubricant is controlled to be > 90°, when the solid lubricant is adsorbed on the interface of the friction pair, the wettability of the interface of the friction pair is regulated to be hydrophobic and lipophilic, and the water phase in the drilling fluid can be prevented from entering the interface of the friction pair. The water phase has poor water lubrication performance, and by inhibiting the water phase from entering the interface of the friction pair, the lubrication performance of the lubricant can be improved; the extreme pressure lubrication coefficient of the liquid lubricant is < 0.15, and the liquid lubricant has good lubricity; when the solid lubricant is combined with the liquid lubricant, the solid phase lubricant can be self-assembled and adsorbed on the interface of the friction pair through hydrophobic effect, a hydrophobic and lipophilic interface is constructed, the adsorption stability of the oil phase lubricant on the interface can be effectively improved, the thickness of the lubricating film is increased, and the lubrication effect can be significantly improved.

[0034] The modified graphite is used as the skeleton of the liquid phase lubricant super-wetting layer, and the rigidity of the layer surface of the modified graphite is strong, so that the pressure resistance of the lubricating layer can be improved; further, when the relative movement between the drilling tool and the formation occurs, the lubricant is stored in the pits to generate dynamic pressure effect, and the external high pressure can be effectively resisted. The liquid lubricant is stored in the pits, and the liquid lubricant is transported from the pit bottom to the pit edge with the movement of the friction pair. In the wedge-shaped structure at the pit edge, the liquid lubricant is compressed to generate a reverse force, that is, micro dynamic pressure. A large amount of micro dynamic pressure is accumulated to generate high dynamic pressure, so that the external high pressure can be effectively resisted, and the interface of the surface texture can withstand extreme pressure, friction and external impact and other extreme environments.

[0035] In some embodiments, the hydroxyl-containing nanoparticles can be formed by hydrolysis of tetraethyl orthosilicate, or metatitanic acid.

[0036] In some embodiments, the silane coupling agent includes at least one of an alkyl silane coupling agent, a fluorocarbon silane coupling agent, and a siloxane silane coupling agent.

[0037] In some embodiments, the hydroxyl-containing nanoparticles are formed by hydrolysis of tetraethyl orthosilicate; and the silane coupling agent is an octadecyl silane coupling agent. In a specific embodiment, the roughness of the solid lubricant is 10-400 nm.

[0038] By limiting the roughness of the solid lubricant, the solid lubricant can have good hydrophobic and lipophilic properties. The modified graphite is adsorbed on the interface of the friction pair, so that the water phase is difficult to be adsorbed on the interface, and has a hydrophobic effect; at the same time, the modified graphite has strong lipophilicity, and the oil phase lubricant can penetrate into the concave pores on the surface of the modified graphite, so that the adsorption stability of the oil phase lubricant on the interface is improved, and the comprehensive lubrication performance of the lubricant composition is improved.

[0039] In a specific embodiment, the surface energy of the solid lubricant is less than 54.8 mN·m.

[0040] When the surface energy of the solid lubricant is less than 54.8 mN·m, the solid lubricant has hydrophobic properties, and the lower the surface energy, the better the hydrophobic and oleophilic effect, which can improve the lubricating performance of the lubricant composition by improving the adsorption stability of the oil phase lubricant on the interface of the friction pair.

[0041] When the modifier is one of the hydroxyl-containing nanoparticles and the silane coupling agent, the modified graphite can be prepared by a preparation method comprising the following processes:

[0042] Disperse the graphite and the cationic surfactant into a solvent to obtain a graphite dispersion liquid;

[0043] Adjust the pH of the graphite dispersion liquid to 10-11 and the temperature to 40-60°C, and add the hydroxyl-containing nanoparticles or the silane coupling agent, and react for 4-6 hours.

[0044] The above solvent is a conventional solvent in the art, for example, water, ethanol, or a mixed solution of the two.

[0045] When the modifier is one of the hydroxyl-containing nanoparticles and the silane coupling agent, the modified graphite can be prepared by a preparation method comprising the following processes:

[0046] Disperse the graphite and the cationic surfactant into a solvent to obtain a graphite dispersion liquid;

[0047] Adjust the pH of the graphite dispersion liquid to 10-11 and the temperature to 40-60°C, and add the hydroxyl-containing nanoparticles, and react for 4-6 hours.

[0048] Adjust the pH of the above solution to 10-11 and the temperature to 40-60°C, and add the silane coupling agent, and react for 4-6 hours.

[0049] The modification of the graphite by the modifier can improve the roughness of the graphite and reduce the surface energy of the graphite.

[0050] In one specific embodiment, the mass ratio of the graphite, the cationic surfactant, the hydroxyl-containing nanoparticles, and the silane coupling agent is (8-10):(0.1-0.5):(0-2):(0-1). By controlling the ratio of the above components, the cost and the performance of the solid lubricant can be considered.

[0051] In one specific embodiment, the liquid lubricant comprises a fatty acid derivative and a non-ionic surfactant.

[0052] The liquid lubricant has certain surface activity, and the solid lubricant can be dispersed in the drilling fluid with the assistance of the liquid lubricant. The solid lubricant spontaneously separates from the water phase and is adsorbed to the interface of the friction pair under the hydrophobic effect due to the increase of the formation temperature, so as to control the wettability of the interface of the underwater friction pair to be super-lipophilic underwater, and then the liquid lubricant containing the fatty acid derivative is captured to construct a super-wetting layer of the liquid lubricant, and the stability of the lubricant composition is improved.

[0053] In a specific embodiment, the mass ratio of the fatty acid derivative to the non-ionic surfactant is (30-80):(20-70).

[0054] Through the above combination and ratio, the liquid lubricant has good lubricating performance.

[0055] Further, in a specific embodiment, the fatty acid derivative includes at least one of a fatty acid ester, a fatty acid amide, a sulfated fatty acid ester, a sulfated fatty acid amide, a fatty acid amide phosphate, a fatty acid polyoxyethylene ether, and a fatty acid polyoxypropylene ether.

[0056] And / or, the non-ionic surfactant includes at least one of Span 80 and Tween 80.

[0057] Specifically, the fatty acid derivative is a mixture of a fatty acid methyl ester and a sulfated fatty acid methyl ester; and the non-ionic surfactant includes Span 80.

[0058] Further, the mass ratio of the fatty acid methyl ester, the sulfated fatty acid methyl ester, and Span 80 is (40-70):(10-30):(20-70).

[0059] Understandably, in a specific embodiment, the above lubricant composition further includes at least one of a mineral oil and a thickening agent.

[0060] The mineral oil accounts for 10% to 50% by volume in the lubricant composition.

[0061] The thickening agent accounts for 1% to 5% by mass in the lubricant composition.

[0062] The mineral oil is not limited in the present application, and conventional substances in the art, such as white oil, can be used. Adding the mineral oil to the lubricant composition can reduce the amount of the liquid lubricant and reduce the cost.

[0063] The thickening agent includes at least one of paraffin and organic clay. Adding the thickening agent can improve the viscosity of the lubricant composition, so that the solid lubricant and the liquid lubricant are uniformly and stably dispersed.

[0064] The second aspect of the present application provides a drilling fluid including the above lubricant composition and a conventional drilling fluid.

[0065] The conventional drilling fluid refers to a drilling fluid without lubricant.

[0066] The method for preparing the drilling fluid comprises the following steps: mixing the above lubricant composition and the conventional drilling fluid.

[0067] Further, the mass ratio of the lubricant composition to the conventional drilling fluid is 0.5% to 10%.

[0068] The scheme provided by the present application is further described below in combination with specific embodiments.

[0069] Embodiment 1

[0070] 1) 10 g of graphite and 0.1 g of hexadecyl trimethyl ammonium chloride were added into 100 mL of a mixed solvent of deionized water / ethanol (1:1) and stirred uniformly. Ammonia water was added to control the pH value to about 10;

[0071] 2) 2 g of tetraethyl orthosilicate was added dropwise into the above solution under stirring at 60°C, and reacted for 6 h;

[0072] 3) 0.5 g of octadecyl trimethoxysilane was added dropwise into the above solution under stirring at 60°C, ammonia water was added to control the pH value to about 10, and the reaction was continued for 6 h;

[0073] 4) the solid-phase suspension in 3) was dried and ground to obtain a solid-phase lubricant;

[0074] 5) methyl oleate, Span 80 and sulfurized methyl oleate were compounded in a ratio of 40:50:10 to form a liquid-phase lubricant;

[0075] 6) the solid-phase lubricant, the liquid-phase lubricant and white oil were mixed in a volume ratio of 20:70:10, 1% paraffin was added, and stirring was carried out at 60°C for 1 h to obtain a lubricant composition.

[0076] The modified graphite (i.e. the solid-phase lubricant) and graphite were subjected to scanning electron microscope analysis, and the results are shown in FIGS. 1 and 2. As can be seen from FIGS. 1-2, the surface of the modified graphite is roughened, and thus has higher hydrophobicity.

[0077] Embodiment 2

[0078] This embodiment is basically the same as Embodiment 1, except that the solid-phase lubricant is graphite.

[0079] Embodiment 3

[0080] This embodiment is basically the same as Embodiment 1, except that Span 80 is replaced by Tween 80.

[0081] Embodiment 4

[0082] This example is basically consistent with Example 1, the difference is that methyl oleate, Span 80 and sulfided methyl oleate are compounded in a ratio of 70:20:10.

[0083] Example 5

[0084] This example is basically consistent with Example 1, the difference is that methyl oleate, Span 80 and sulfided methyl oleate are compounded in a ratio of 20:70:10.

[0085] Example 6

[0086] This example is basically consistent with Example 1, the difference is that the modifier is only tetraethyl orthosilicate, without octadecyl trimethoxysilane, i.e. lacking step 3.

[0087] Example 7

[0088] This example is basically consistent with Example 1, the difference is that the modifier is only octadecyl trimethoxysilane, without tetraethyl orthosilicate, i.e. lacking step 2.

[0089] Comparative Example 1

[0090] The lubricant provided in this comparative example is graphite.

[0091] Comparative Example 2

[0092] The lubricant provided in this comparative example is the solid-phase lubricant prepared in Example 1 through steps 1) to 4).

[0093] Comparative Example 3

[0094] The lubricant provided in this comparative example is a mixture of the liquid-phase lubricant prepared in Example 1 through step 5) and white oil in a volume ratio of 90:10, with 1% paraffin added, stirred at 60°C for 1h, and the obtained product.

[0095] Test Example

[0096] 1. The water contact angle, roughness, and surface energy of the solid lubricant of the lubricant composition in the examples and comparative examples are tested, and the extreme pressure lubrication coefficient of the liquid lubricant is tested.

[0097] Test method of water contact angle: the solid-phase lubricant in the examples and comparative examples is pressed into a sheet shape using a tablet press, and the contact angle measuring instrument is used to test the contact angle of deionized water on the surface of the sheet-shaped solid-phase lubricant.

[0098] Test method of roughness: the surface roughness of the solid-phase lubricant is tested using a profilometer.

[0099] Surface energy test method: The surface energy of the solid lubricant was tested by using the Owens two-liquid method with water and n-hexadecane as the test liquids.

[0100] Extreme pressure lubrication coefficient test method: The extreme pressure lubrication coefficient of the liquid lubricant synthesized in the examples and comparative examples was tested in a 4% bentonite water phase by using an extreme pressure lubrication instrument. The lubricant was added in an amount of 1%. See the extreme pressure lubrication performance evaluation section below.

[0101] The test results are shown in Table 1.

[0102] Table 1. Properties of the lubricant compositions in the examples and comparative examples

[0103] 2. Extreme pressure lubrication performance evaluation

[0104] The extreme pressure lubrication coefficients of the drilling fluids before and after aging at 180°C were tested for the lubricants prepared in the examples and comparative examples.

[0105] The specific operation is as follows: a drilling fluid with a density of 2.0 g / cm 3 was prepared according to the following formulation: 2% bentonite + 3% DSP-1 + 5% SPNH + 10% KCl + 0.3% NaOH + barite. 5% of the lubricant composition in Example 1 was added to the above drilling fluid system, and high-speed stirring was performed for 20 min. Then the drilling fluid with the added lubricant was hot-rolled and aged in a roller oven at 180°C for 16 h.

[0106] The processing steps of the remaining examples and comparative examples refer to the steps of Example 1 described above. In Comparative Example 2, the graphite product is difficult to disperse uniformly in the water phase due to its strong hydrophobicity, and 1% Span 80 needs to be added to assist its dispersion in the water phase.

[0107] Extreme pressure lubrication performance test: The extreme pressure lubrication coefficients of the drilling fluid system before and after aging were tested by using a Fann 21200 type extreme pressure lubrication instrument, the test ring rotation speed was 60 rpm, and the applied torque force was 150 inch-pounds.

[0108] Table 2. Extreme pressure lubrication performance evaluation

[0109] 3. High-density drilling fluid lubrication performance evaluation

[0110] Drilling fluids with different densities were prepared according to the following formulation: 2% bentonite + 3% DSP-1 + 5% SPNH + 10% KCl + 0.3% NaOH + barite. The lubricant composition in Example 1 was added to the drilling fluids with different densities, and the test results are shown in the table below. The aging temperature was 180°C, and the aging time was 16 h.

[0111] Table 3 High pressure resistance evaluation

[0112] 4. High temperature and high salt resistance evaluation

[0113] A drilling fluid base slurry was prepared according to the following formulation: 4% bentonite + 0.3% NaCO3, with a certain amount of salt (NaCl) added, and the lubricant composition in Example 1 was tested at different aging temperatures and salt concentrations, and the test results are shown in the following table. The density of the drilling fluid was 2.0 g / cm 3 .

[0114] Table 4 High temperature and high salt resistance evaluation

[0115] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions described in the foregoing examples can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

A lubricant composition wherein, The solid lubricant has a water contact angle of >90°. The liquid lubricant has a coefficient of extreme pressure lubrication <0.

15. The solid lubricant is modified graphite, and the modifier comprises at least one of a hydroxyl-containing nanoparticle and a silane coupling agent. The lubricant composition according to claim 1, wherein, The solid lubricant has a roughness of 10-400 nm. The lubricant composition according to claim 1 or 2, wherein, The solid lubricant has a surface energy less than 54.8 mN·m. The lubricant composition according to any one of claims 1 to 3, wherein The liquid lubricant comprises a fatty acid derivative and a non-ionic surfactant. The lubricant composition according to claim 4, wherein, The fatty acid derivative comprises at least one of a fatty acid ester, a fatty acid amide, a sulfated fatty acid ester, a sulfated fatty acid amide, a fatty acid amide phosphate, a fatty acid polyoxyethylene ether, and a fatty acid polyoxypropylene ether. The lubricant composition according to claim 4, wherein, The non-ionic surfactant comprises at least one of a Span and a Tween. The lubricant composition according to any one of claims 1 to 6, wherein The lubricant composition further comprises at least one of a mineral oil and a thickening agent. The mineral oil accounts for 10-50% by volume of the lubricant composition. The thickening agent accounts for 1-5% by mass of the lubricant composition. The lubricant composition according to any one of claims 1 to 7, wherein The modified graphite is prepared by a preparation method comprising the following steps: dispersing graphite and a cationic surfactant into a solvent to obtain a graphite dispersion; adjusting the pH of the graphite dispersion to 10-11 and the temperature to 40-60°C, adding a hydroxyl-containing nanoparticle and / or a silane coupling agent, and reacting for 4-6 h. The lubricant composition according to claim 8, wherein, The mass ratio of the graphite, the cationic surfactant, the hydroxyl-containing nanoparticle, and the silane coupling agent is (8-10):(0.1-0.5):(0-2):(0-1). A drilling fluid, wherein, The lubricant composition of any one of claims 1-9 and a conventional drilling fluid.

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