A temperature-resistant microcapsule lubricant and its preparation method and application

Abstract

The present invention provides a temperature-resistant microcapsule lubricant and a preparation method and application thereof, belonging to the technical field of drilling fluid lubricants. The preparation of the lubricant of the present invention comprises the following steps: uniformly mixing lubricating oil, emulsifier and water to obtain an oil-in-water emulsion; sequentially adding methyl methacrylate, ethyl acrylate and butyl acrylate to the oil-in-water emulsion, adding a crosslinking agent and an initiator, and reacting to obtain microcapsules; adding isophorone diisocyanate to an emulsifier aqueous solution, adding microcapsules, nano-silicon dioxide and a catalyst dibutyltin diacetate, and reacting to obtain the microcapsules. The lubricant of the present invention has good thermal stability and lubricating properties; the microcapsules can remain stable and not degraded in a high-temperature environment underground; when encountering high friction resistance during underground circulation drilling, the wall material will only break when subjected to greater friction, extrusion or shearing, thereby achieving targeted release of the core material lubricant, and the local high-concentration lubricant can form an oil film on the high-friction surface to exert an efficient lubricating effect.

Description

Technical Field

[0001] The invention relates to the technical field of drilling fluid lubricants, and in particular to a temperature-resistant microcapsule lubricant and a preparation method and application thereof. Background Art

[0002] The performance of drilling fluid lubricants seriously affects the drilling efficiency of drilling projects. At present, my country's shallow oil and gas reserves are constantly decreasing, and oil and gas exploration and development are gradually turning to deep layers. High temperature, high pressure, high friction and torque will appear in the well, which puts higher requirements on drilling fluid lubricants. Under high temperature conditions, due to the degradation of lubricants, the rheological properties of drilling fluids deteriorate and the filtration loss increases. The current drilling fluid lubricants mainly include solid lubricants and liquid lubricants. Solid lubricants change the friction state by changing the contact mode between the drill string and the casing, thereby reducing the friction coefficient. Liquid lubricants are coated on the surface of the drill bit by adsorption and film formation, thereby reducing the friction coefficient downhole.

[0003] However, conventional lubricants are currently added directly to drilling fluids and work through the circulation of drilling fluids. This method of addition will affect the rheological properties, filtration properties and other properties of the drilling fluids. For example, emulsion lubricants added to drilling fluids will cause foaming, resulting in significant changes in the density of the drilling fluids. After being added to the drilling fluids, lubricants are easily adsorbed on the surface of solid particles and consumed in large quantities, making it impossible to achieve efficient lubrication.

[0004] As a new type of encapsulation material, microcapsules are widely used in medicine, biology, food and other industries. Microcapsules can isolate the core material from the external environment, preventing the core material from reacting with the external environment and losing its original effect. The drilling fluid microcapsule lubricant is coated with microcapsule technology to isolate the external environment, and at the same time has a certain ability to resist high temperature and high pressure downhole. Under certain conditions (temperature or pressure), the microcapsule wall ruptures, releasing the core material, playing a lubricating role, and can effectively reduce the friction coefficient. However, the existing microcapsule wall material has poor thermal stability, and it is easy to degrade and release the core material under high temperature conditions during deep / ultra-deep well drilling, which cannot achieve the purpose of protecting the core material and targeted release and efficient lubrication; therefore, it is urgent to develop a microcapsule lubricant that is stable at high temperature, suitable for deep / ultra-deep well drilling, can achieve targeted release, efficient lubrication, and has excellent lubrication performance. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a temperature-resistant microcapsule lubricant and a preparation method and application thereof. The temperature-resistant microcapsule lubricant of the present invention is a double-wall microcapsule modified with nano-silicon dioxide. The temperature-resistant microcapsule lubricant of the present invention has good thermal stability and lubrication performance; the microcapsules can remain stable and not degraded in a high-temperature environment underground; when high friction resistance is encountered during underground drilling, the wall material will only break when subjected to greater friction, extrusion or shearing, thereby achieving targeted release of the core material lubricant, and the local high-concentration lubricant can form an oil film on the high-friction surface to exert an efficient lubricating effect.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of the present invention provides a method for preparing a temperature-resistant microcapsule lubricant, comprising the steps of:

[0008] (1) mixing lubricating oil, emulsifier and water uniformly to obtain an oil-in-water emulsion;

[0009] (2) adding methyl methacrylate, ethyl acrylate and butyl acrylate to an oil-in-water emulsion in sequence, adding a crosslinking agent and an initiator, reacting, and then standing, filtering, washing and drying to obtain methyl methacrylate microcapsules;

[0010] (3) Add isophorone diisocyanate to an emulsifier aqueous solution, add methyl methacrylate microcapsules, nano-silicon dioxide and a catalyst dibutyltin diacetate, react, and then stand, filter, wash and dry to obtain a temperature-resistant microcapsule lubricant.

[0011] According to the present invention, in step (1), the lubricating oil is a lubricating oil for drilling fluid. Preferably, the lubricating oil is 3# white oil, vegetable oil, liquid paraffin or biodiesel.

[0012] According to the present invention, preferably, in step (1), the emulsifier is selected from one or a combination of two or more of Tween-80, Span-80, OP-10, sodium dodecylbenzene sulfonate, sodium dodecyl sulfonate or sodium dodecyl sulfate. Preferably, the emulsifier is a combination of Tween-80 and Span-80, wherein the mass ratio of Tween-80 to Span-80 is 6-7:1.

[0013] According to the present invention, preferably, in step (1), the mass ratio of the emulsifier, the lubricating oil and the water is 1:4-8:20-40.

[0014] According to the present invention, preferably, in step (1), in order to achieve uniform mixing, the mixing conditions are 30-40°C, 600-1600 r / min emulsification shearing for 5-60 min.

[0015] According to the present invention, preferably, in step (2), the oil-in-water emulsion further comprises a stirring step before use; the stirring temperature is 30-40° C., the stirring time is 1-2 h, and the stirring rate is 600-1600 r / min.

[0016] According to the present invention, preferably, in step (2), the mass ratio of ethyl acrylate, butyl acrylate and methyl methacrylate is 1:1-5:2-15, preferably 1:2-5:10-15; the total mass of ethyl acrylate, butyl acrylate and methyl methacrylate accounts for 20-40% of the mass of the oil-in-water emulsion.

[0017] According to the present invention, preferably, in step (2), the cross-linking agent is one or a combination of two or more of pentaerythritol tetraacrylate, allyl methacrylate, 1,4-butanediol diacrylate or hexanediol dimethacrylate; the mass of the cross-linking agent accounts for 1-5% of the total mass of ethyl acrylate, butyl acrylate and methyl methacrylate.

[0018] According to the present invention, preferably, in step (2), the initiator is one or a combination of two or more of azobisisobutyronitrile, potassium persulfate or azobisisoheptylnitrile; the mass of the initiator accounts for 0.1-0.5% of the total mass of ethyl acrylate, butyl acrylate and methyl methacrylate.

[0019] According to the present invention, preferably, in step (2), the crosslinking agent and the initiator are added to the system in sequence under stirring conditions of 50-80° C. and 400-600 r / min.

[0020] According to the present invention, preferably, in step (2), the reaction temperature is 50-80°C, the reaction time is 4-6h, and the reaction is carried out under stirring conditions of 400-600r / min.

[0021] According to the present invention, preferably, in step (3), the emulsifier is one or a combination of two or more of Tween-80, OP-10, sodium dodecylbenzene sulfonate, sodium dodecyl sulfonate or sodium dodecyl sulfate; and the mass concentration of the emulsifier aqueous solution is 1-10%.

[0022] According to the present invention, preferably, in step (3), the mass ratio of the emulsifier, isophorone diisocyanate, and methyl methacrylate microcapsules is 1:4-8:10-16.

[0023] According to the present invention, preferably, in step (3), the particle size of nano-silicon dioxide is 20-60 nm, and its mass accounts for 1-5% of the total mass of the emulsifier aqueous solution, isophorone diisocyanate, and methyl methacrylate microcapsules.

[0024] According to the present invention, preferably, in step (3), the mass of the catalyst dibutyltin diacetate accounts for 0.1-0.16% of the total mass of the emulsifier aqueous solution, isophorone diisocyanate, and methyl methacrylate microcapsules.

[0025] According to the present invention, preferably, in step (3), the reaction temperature is 50-80° C., the reaction time is 4-6 h, and the reaction is carried out under stirring conditions of 400-600 r / min.

[0026] The second aspect of the present invention provides a temperature-resistant microcapsule lubricant prepared by the above method.

[0027] According to the present invention, preferably, the average particle size of the microcapsule lubricant is 20-40 μm, and the temperature resistance is above 180°C.

[0028] A third aspect of the present invention provides a use of a temperature-resistant microcapsule lubricant in high-temperature drilling.

[0029] The technical features and beneficial effects of the present invention are as follows:

[0030] 1. The present invention first prepares single-wall microcapsules with methyl methacrylate-ethyl acrylate-butyl acrylate cross-linked copolymer as wall material and lubricating oil as core material; and further introduces isophorone diisocyanate as wall material by interfacial polymerization to prepare double-wall microcapsules. The wall material of the microcapsule lubricant of the present invention is obtained by secondary cross-linking to form a capsule wall, and then modified with nano-silicon dioxide. The present invention introduces solid-phase particle nano-silicon dioxide, and obtains double-wall microcapsules through multi-step reactions. The thermal stability of the microcapsules is improved by the synergistic effect of nano-silicon dioxide and double walls; compared with the case without adding nano-silicon dioxide, the temperature resistance of the microcapsule lubricant provided by the method of the present invention is significantly enhanced.

[0031] 2. The present invention designs a double-wall structure so that the obtained microcapsules have good thermal stability and lubrication performance. The microcapsules can remain stable and not degraded in the high-temperature environment underground; when encountering high friction resistance during underground circulation drilling, the wall material will break when subjected to greater friction, extrusion or shearing, achieving targeted release of the core material lubricant, and the local high-concentration lubricant can form an oil film on the high-friction surface to play an efficient lubricating role. The present invention improves the temperature resistance of the microcapsules, reduces the loss rate of the lubricant, prolongs the lubrication time, and effectively reduces the friction coefficient.

[0032] 3. In the preparation of methyl methacrylate microcapsules of the present invention, the reaction monomers are methyl methacrylate, ethyl acrylate and butyl acrylate; the temperature resistance of the microcapsules is increased by introducing a longer carbon chain; the temperature resistance and lubrication properties of the microcapsules will decrease if the reaction monomers are replaced, one or more of them are reduced, or the ratio is inappropriate. The present invention improves the temperature resistance of the microcapsule lubricant by introducing a long carbon chain wall material, a double-wall structure and a modified design of nano-silicon dioxide; and on the basis of improving the temperature resistance, the good lubrication effect of the microcapsule lubricant is still maintained. DETAILED DESCRIPTION

[0033] The present invention will be described below by way of examples.

[0034] In the following examples, the test methods and instruments involved are as follows:

[0035] Particle size test of microcapsule lubricant: 0.1 g of microcapsule lubricant was added to 100 mL of deionized water, stirred at 10000 rpm for 10 min, and then tested using a Bettersize 2000 laser particle size analyzer.

[0036] Example 1

[0037] A method for preparing a temperature-resistant microcapsule lubricant comprises the following steps:

[0038] (1) Weigh 120g of deionized water into a beaker, add 20g of 3# white oil, 0.4g of emulsifier Span-80, and 2.6g of emulsifier Tween-80, and emulsify and shear at 30℃ and 1500r / min for 15min to obtain a stable milky white oil-in-water emulsion.

[0039] (2) Take 120g of milky white oil-in-water emulsion in a three-necked flask, adjust the water bath temperature to 35℃, and the stirrer speed to 800r / min; after 1.5h of water bath, add 2.75g of ethyl acrylate, 8.25g of butyl acrylate and 33g of methyl methacrylate in sequence; adjust the water bath temperature to 60℃; adjust the stirring speed to 500r / min; slowly add 0.88g of pentaerythritol tetraacrylate as a crosslinking agent with a rubber dropper. Slowly add 0.22g of azobisisobutyronitrile; after 6h of reaction time, let it stand, filter, wash it alternately with deionized water and anhydrous ethanol for 3 times, and dry it at 50℃ for 24h to obtain white solid particles, namely methyl methacrylate microcapsules.

[0040] (3) Mix 3g of emulsifier sodium dodecyl sulfonate and 114g of water evenly, with the water bath temperature at 60°C and the stirring speed at 500r / min, and add 18g of isophorone diisocyanate, 45g of methyl methacrylate microcapsules, 0.27g of catalyst dibutyltin diacetate and 3.6g of nano-silicon dioxide (average particle size of 30nm) in sequence. After reacting for 5h, let it stand, filter, wash alternately with deionized water and anhydrous ethanol, and dry at 50°C for 24h. The obtained white particles are microcapsule lubricant with an average particle size of 30.6μm.

[0041] Example 2

[0042] A method for preparing a temperature-resistant microcapsule lubricant comprises the following steps:

[0043] (1) Weigh 120g of deionized water into a beaker, add 12g of 3# white oil, 0.4g of emulsifier Span-80, and 2.6g of emulsifier Tween-80, and emulsify and shear at 30℃ and 1500r / min for 15min to obtain a stable milky white oil-in-water emulsion.

[0044] (2) Take 120g of milky white oil-in-water emulsion in a three-necked flask, adjust the water bath temperature to 30℃, and the stirrer speed to 800r / min; after 1.5h of water bath, add 2.75g of ethyl acrylate, 5.5g of butyl acrylate and 35.75g of methyl methacrylate in sequence; adjust the water bath temperature to 50℃; adjust the stirring speed to 500r / min; slowly add 0.44g of pentaerythritol tetraacrylate as a crosslinking agent with a rubber dropper. Slowly add 0.22g of azobisisobutyronitrile; after reacting for 6h, let it stand, filter, wash it alternately with deionized water and anhydrous ethanol for 3 times, and dry it at 40℃ for 24h to obtain white solid particles, namely methyl methacrylate microcapsules.

[0045] (3) Mix 3g of emulsifier sodium dodecyl sulfonate and 114g of water evenly, with the water bath temperature at 60°C and the stirring speed at 500r / min, and add 18g of isophorone diisocyanate, 45g of methyl methacrylate microcapsules, 0.18g of catalyst dibutyltin diacetate and 1.8g of nano-silicon dioxide (average particle size of 30nm) in sequence. After reacting for 5h, let it stand, filter, wash alternately with deionized water and anhydrous ethanol, and dry at 50°C for 24h. The obtained white particles are microcapsule lubricant with an average particle size of 21.6μm.

[0046] Example 3

[0047] A method for preparing a temperature-resistant microcapsule lubricant comprises the following steps:

[0048] (1) Weigh 120g of deionized water into a beaker, add 24g of 3# white oil, 0.4g of emulsifier Span-80, and 2.6g of emulsifier Tween-80, and emulsify and shear at 30℃ and 1500r / min for 15min to obtain a stable milky white oil-in-water emulsion.

[0049] (2) Take 120g of milky white oil-in-water emulsion in a three-necked flask, adjust the water bath temperature to 40℃, and adjust the stirrer speed to 800r / min; after 2h of water bath, add 2.2g of ethyl acrylate, 11g of butyl acrylate and 30.8g of methyl methacrylate in sequence; adjust the water bath temperature to 80℃; adjust the stirring speed to 500r / min; slowly add 2.2g of pentaerythritol tetraacrylate as a crosslinking agent with a rubber dropper. Slowly add 0.22g of azobisisobutyronitrile; after reacting for 4h, let it stand, filter, wash it alternately with deionized water and anhydrous ethanol for 3 times, and dry it at 60℃ for 24h to obtain white solid particles, namely methyl methacrylate microcapsules.

[0050] (3) Mix 3g of emulsifier sodium dodecyl sulfonate and 120g of water evenly, with the water bath temperature at 80°C and the stirring speed at 600r / min, and add 24g of isophorone diisocyanate, 48g of methyl methacrylate microcapsules, 0.28g of catalyst dibutyltin diacetate and 9.75g of nano-silicon dioxide (average particle size of 30nm) in sequence. After reacting for 6h, let it stand, filter, wash alternately with deionized water and anhydrous ethanol, and dry at 60°C for 24h. The obtained white particles are microcapsule lubricant with an average particle size of 39.6μm.

[0051] Example 4

[0052] A method for preparing a temperature-resistant microcapsule lubricant comprises the following steps:

[0053] (1) Weigh 120g of deionized water into a beaker, add 20g of 3# white oil, 0.4g of emulsifier Span-80, and 2.6g of emulsifier Tween-80, and emulsify and shear at 30℃ and 600r / min for 15min to obtain a stable milky white oil-in-water emulsion.

[0054] (2) Take 120g of milky white oil-in-water emulsion in a three-necked flask, adjust the water bath temperature to 35℃, and the stirrer speed to 800r / min; after 1.5h of water bath, add 2.75g of ethyl acrylate, 8.25g of butyl acrylate and 33g of methyl methacrylate in sequence; adjust the water bath temperature to 60℃; adjust the stirring speed to 500r / min; slowly add 2.2g of pentaerythritol tetraacrylate as a crosslinking agent with a rubber dropper. Slowly add 0.22g of azobisisobutyronitrile; after reacting for 4h, let it stand, filter, wash it alternately with deionized water and anhydrous ethanol for 3 times, and dry it at 50℃ for 24h to obtain white solid particles, namely methyl methacrylate microcapsules.

[0055] (3) Mix 3g of emulsifier sodium dodecyl sulfonate and 114g of water evenly, with the water bath temperature at 60°C and the stirring speed at 500r / min, and add 18g of isophorone diisocyanate, 45g of methyl methacrylate microcapsules, 0.24g of catalyst dibutyltin diacetate and 1.8g of nano-silicon dioxide (average particle size of 30nm) in sequence. After reacting for 5h, let it stand, filter, wash alternately with deionized water and anhydrous ethanol, and dry at 50°C for 24h. The obtained white particles are microcapsule lubricant with an average particle size of 38.8μm.

[0056] Example 5

[0057] A method for preparing a temperature-resistant microcapsule lubricant comprises the following steps:

[0058] (1) Weigh 120g of deionized water into a beaker, add 20g of 3# white oil, 0.4g of emulsifier Span-80, and 2.6g of emulsifier Tween-80, and emulsify and shear at 30℃ and 1500r / min for 15min to obtain a stable milky white oil-in-water emulsion.

[0059] (2) Take 120g of milky white oil-in-water emulsion in a three-necked flask, adjust the water bath temperature to 30℃, and adjust the stirrer speed to 600r / min; after 2h of water bath, add 2.75g of ethyl acrylate, 8.25g of butyl acrylate and 33g of methyl methacrylate in sequence; adjust the water bath temperature to 80℃; adjust the stirring speed to 500r / min; slowly add 2.2g of pentaerythritol tetraacrylate as a crosslinking agent with a rubber dropper. Slowly add 0.22g of azobisisobutyronitrile; after reacting for 4h, let it stand, filter, wash it alternately with deionized water and anhydrous ethanol for 3 times, and dry it at 50℃ for 24h to obtain white solid particles, namely methyl methacrylate microcapsules.

[0060] (3) Mix 3g of emulsifier sodium dodecyl sulfate and 114g of water evenly, with the water bath temperature at 60°C and the stirring speed at 500r / min, and add 18g of isophorone diisocyanate, 45g of methyl methacrylate microcapsules, 0.24g of catalyst dibutyltin diacetate and 1.8g of nano-silicon dioxide (average particle size of 30nm) in sequence. After reacting for 4h, let it stand, filter, wash alternately with deionized water and anhydrous ethanol, and dry at 50°C for 24h. The obtained white particles are microcapsule lubricant with an average particle size of 39.2μm.

[0061] Example 6

[0062] A method for preparing a temperature-resistant microcapsule lubricant comprises the following steps:

[0063] (1) Weigh 120g of deionized water into a beaker, add 20g of 3# white oil, 0.4g of emulsifier Span-80, and 2.6g of emulsifier Tween-80, and emulsify and shear at 30℃ and 1500r / min for 15min to obtain a stable milky white oil-in-water emulsion.

[0064] (2) Take 120g of milky white oil-in-water emulsion in a three-necked flask, adjust the water bath temperature to 40℃, and the stirrer speed to 1600r / min; after water bathing for 1h, add 2.75g of ethyl acrylate, 8.25g of butyl acrylate and 33g of methyl methacrylate in sequence; adjust the water bath temperature to 60℃; adjust the stirring speed to 400r / min; slowly add 0.88g of pentaerythritol tetraacrylate as a crosslinking agent with a rubber dropper. Slowly add 0.22g of azobisisobutyronitrile; after reacting for 4h, let it stand, filter, wash it alternately with deionized water and anhydrous ethanol for 3 times, and dry it at 50℃ for 24h to obtain white solid particles, namely methyl methacrylate microcapsules.

[0065] (3) Mix 3g of emulsifier sodium dodecyl sulfonate and 114g of water evenly, with the water bath temperature at 60°C and the stirring speed at 500r / min, and add 18g of isophorone diisocyanate, 45g of methyl methacrylate microcapsules, 0.22g of catalyst dibutyltin diacetate and 1.8g of nano-silicon dioxide (average particle size of 30nm) in sequence. After reacting for 5h, let it stand, filter, wash alternately with deionized water and anhydrous ethanol, and dry at 50°C for 24h. The obtained white particles are microcapsule lubricant with an average particle size of 38.8μm.

[0066] Example 7

[0067] A method for preparing a temperature-resistant microcapsule lubricant is as described in Example 1, except that in step (2), the amount of ethyl acrylate is 11 g, the amount of butyl acrylate is 11 g, and the amount of methyl methacrylate is 22 g, so that the mass ratio of ethyl acrylate, butyl acrylate and methyl methacrylate is 1:1:2; the other steps and conditions are the same as in Example 1. A microcapsule lubricant is obtained, and its average particle size is 67.3 μm.

[0068] Comparative Example 1

[0069] A method for preparing a microcapsule lubricant is as described in Example 1, except that step (3) is omitted and the other steps and conditions are the same as those in Example 1; methyl methacrylate microcapsules are obtained.

[0070] Comparative Example 2

[0071] A method for preparing a microcapsule lubricant is as described in Example 1, except that in step (3), no nano-silicon dioxide is added; the other steps and conditions are the same as in Example 1; and the microcapsule lubricant is obtained.

[0072] Comparative Example 3

[0073] A method for preparing a microcapsule lubricant is as described in Example 1, except that in step (2), the amount of methyl methacrylate used is 44 g, and the other steps and conditions are the same as in Example 1. A microcapsule lubricant is obtained.

[0074] Comparative Example 4

[0075] A method for preparing a microcapsule lubricant is as described in Example 1, except that in step (2), ethyl acrylate and butyl acrylate are replaced by acrylamide of the same mass, and the other steps and conditions are the same as in Example 1. A microcapsule lubricant is obtained.

[0076] Test Example 1

[0077] High temperature resistance test

[0078] 3 g of the microcapsule lubricant prepared in each embodiment and comparative example was added to 100 mL of deionized water, stirred evenly, and then transferred to an aging tank, and hot rolled at 180°C for 16 hours. After the hot rolling, it was cooled to room temperature, the mixed solution was filtered, and the filter cake was washed 3 times with anhydrous ethanol. After vacuum drying, the remaining solid mass was weighed, and the mass retention rate of the microcapsule was calculated. Table 1 shows the mass retention rate of the microcapsule lubricant after hot rolling at 180°C for 16 hours for each sample.

[0079] Table 1 Mass retention rate of microcapsule lubricant after hot rolling at 180℃ for 16h

[0080]

[0081] From the test results in Table 1, it can be seen that after being hot-rolled at 180°C, the mass retention rates of Examples 1-6 are all above 80%. In Example 7, the ratio of the wall material reaction monomers is changed, which will reduce the temperature resistance. The single-walled microcapsules in Comparative Example 1 have poor temperature resistance. Since nano-silicon dioxide is not added to the wall material of Comparative Example 2, the temperature resistance is very poor, and the mass retention rate is less than 40%, indicating that nano-silicon dioxide can significantly improve the temperature resistance of the microcapsules. In Comparative Example 3, due to the change in the type of wall material monomers, the temperature resistance of the microcapsules is greatly reduced. In Comparative Example 4, due to the replacement of different types of wall material monomers, the temperature resistance of the wall material is reduced.

[0082] Test Example 2

[0083] Lubrication performance test

[0084] Preparation of bentonite-based slurry: Add 16 g of sodium bentonite and 0.8 g of sodium carbonate into 400 mL of clean water, stir at 10,000 rpm for 30 min, and then seal and cure for more than 24 h to obtain bentonite-based slurry.

[0085] 1g of xanthan gum was added to 400mL of bentonite-based slurry, and after stirring at 10000rpm for 15min, 10g of the microcapsule lubricant or 3# white oil prepared in each embodiment and comparative example was added respectively, and after stirring for 10min, the lubricity was tested using a four-ball friction and wear tester (Jinan Times Tester Co., Ltd.). The steel ball used was made of GCr15 material with a diameter of 12.7mm. The test conditions were: load 600N, temperature 25°C, time 1800s, and speed 1000rpm. After the test, the wear spot surface of the steel ball was observed using a metallographic microscope. Table 2 shows the wear spot diameter results of the steel ball wear spot surface of each sample.

[0086] Table 2 Wear spot diameter results of steel ball wear spot surface of each sample

[0087]

[0088] As can be seen from Table 2, compared with 3# white oil, the friction spot diameter of Examples 1-7 is significantly reduced, which is because the microcapsules are squeezed and destroyed under pressure, gradually releasing the core material. The friction reduction effect of Comparative Examples 1-4 is significantly reduced. From the above, the wall material of the present invention combined with the core material can better achieve the effect of reducing friction.

[0089] Test Example 3

[0090] High temperature resistance and lubricity testing

[0091] Preparation of bentonite-based slurry: Add 16 g of sodium bentonite and 0.8 g of sodium carbonate into 400 mL of clean water, stir at 10,000 rpm for 30 min, and then seal and cure for more than 24 h to obtain bentonite-based slurry.

[0092] 10g of the microcapsule lubricant or 3# white oil prepared in each embodiment and comparative example was added to 400mL of bentonite-based slurry, stirred at 10000rpm for 10min, and then transferred to an aging tank. The aging tank was hot rolled at 180°C for 16h. The extreme pressure lubrication coefficient of the above experimental slurry before and after hot rolling was tested using an EP-1 extreme pressure lubrication instrument, and the test results are shown in Tables 3 and 4.

[0093] Table 3 Extreme pressure lubrication coefficient data after hot rolling

[0094]

[0095] Table 4 Extreme pressure lubrication coefficient data after hot rolling

[0096]

[0097] It can be seen from the test results in Table 3 and Table 4 that after adding 3# white oil to the bentonite-based slurry, there is a good lubrication effect before and after hot rolling. Compared with the bentonite-based slurry, the lubrication coefficient reduction rate of Examples 1-6 after hot rolling at 180℃ for 16h can reach more than 50%. The microcapsule lubricant in Example 1 has the best effect. After hot rolling at 180℃ / 16h, the lubrication coefficient reduction rate is still as high as 73.1%. Compared with Example 1, the lubrication coefficient reduction rate of Example 7 and Comparative Example 3 is significantly reduced, and the temperature resistance is significantly reduced. Comparative Example 1 is a single-walled microcapsule. Compared with Example 1, the lubrication coefficient is reduced, and the temperature resistance of the single wall is relatively poor. Comparative Example 2 is a microcapsule without adding nano-silicon dioxide. Compared with Example 1, the temperature resistance of the microcapsule is significantly reduced, which is because nano-silicon dioxide can significantly improve the temperature resistance of the microcapsule. Compared with Example 1, Comparative Example 4 replaces part of the monomers in the wall material, resulting in a significant decrease in the temperature resistance of the microcapsule and a significant decrease in the lubrication performance of the microcapsule.

[0098] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. Application of a temperature-resistant microcapsule lubricant in high-temperature drilling, characterized in that: The method for preparing the temperature-resistant microcapsule lubricant is characterized by comprising the steps of: (1) mixing lubricating oil, emulsifier and water uniformly to obtain an oil-in-water emulsion; The lubricating oil is 3# white oil, vegetable oil, liquid paraffin or biodiesel; the emulsifier is selected from one or a combination of two or more of Tween-80, Span-80, OP-10, sodium dodecylbenzene sulfonate, sodium dodecyl sulfonate or sodium dodecyl sulfate; (2) adding methyl methacrylate, ethyl acrylate and butyl acrylate to an oil-in-water emulsion in sequence, adding a crosslinking agent and an initiator, reacting, and then standing, filtering, washing and drying to obtain methyl methacrylate microcapsules; The crosslinking agent is one or a combination of two or more of pentaerythritol tetraacrylate, allyl methacrylate, 1,4-butanediol diacrylate or hexanediol dimethacrylate; the initiator is one or a combination of two or more of azobisisobutyronitrile, potassium persulfate or azobisisoheptanenitrile; the mass ratio of ethyl acrylate, butyl acrylate and methyl methacrylate is 1:2-5:10-15; (3) adding isophorone diisocyanate to an aqueous emulsifier solution, adding methyl methacrylate microcapsules, nano-silicon dioxide and a catalyst dibutyltin diacetate, reacting, and then standing, filtering, washing and drying to obtain a temperature-resistant microcapsule lubricant; The emulsifier is one or a combination of two or more of Tween-80, OP-10, sodium dodecylbenzene sulfonate, sodium dodecyl sulfonate or sodium dodecyl sulfate.

2. The use according to claim 1, characterized in that: In step (1), one or more of the following conditions are included: i. The mass ratio of emulsifier, lubricating oil and water is 1:4-8:20-40; ii. To achieve uniform mixing, the mixing conditions are 30-40°C, 600-1600r / min emulsification shearing for 5-60min.

3. The use according to claim 1, characterized in that: In step (2), the total mass of ethyl acrylate, butyl acrylate and methyl methacrylate accounts for 20-40% of the mass of the oil-in-water emulsion.

4. The use according to claim 1, characterized in that: In step (2), the mass of the cross-linking agent accounts for 1-5% of the total mass of ethyl acrylate, butyl acrylate and methyl methacrylate.

5. The use according to claim 1, characterized in that: In step (2), the mass of the initiator accounts for 0.1-0.5% of the total mass of ethyl acrylate, butyl acrylate and methyl methacrylate.

6. The use according to claim 1, characterized in that: In step (2), one or more of the following conditions are included: i. The oil-in-water emulsion also includes a stirring step before use; the stirring temperature is 30-40°C, the stirring time is 1-2h, and the stirring rate is 600-1600r / min; ii. The crosslinking agent and initiator are added into the system in sequence under stirring conditions of 50-80°C and 400-600r / min; iii. The reaction temperature is 50-80°C, the reaction time is 4-6h, and the reaction is carried out under stirring conditions of 400-600r / min.

7. The use according to claim 1, characterized in that: In step (3), one or more of the following conditions are included: i. The mass concentration of the emulsifier aqueous solution is 1-10%; ii. The mass ratio of emulsifier, isophorone diisocyanate and methyl methacrylate microcapsules is 1:4-8:10-16; iii. The particle size of nano-silicon dioxide is 20-60 nm, and its mass accounts for 1-5% of the total mass of the emulsifier aqueous solution, isophorone diisocyanate, and methyl methacrylate microcapsules; iv. The mass of the catalyst dibutyltin diacetate accounts for 0.1-0.16% of the total mass of the emulsifier aqueous solution, isophorone diisocyanate, and methyl methacrylate microcapsules; v. The reaction temperature is 50-80°C, the reaction time is 4-6h, and the reaction is carried out under stirring conditions of 400-600r / min.

8. The use according to claim 1, characterized in that: The average particle size of the microcapsule lubricant is 20-40 μm, and the temperature resistance is above 180° C.

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