High temperature heat conducting phase change microcapsules for drilling fluids and methods of making the same

Abstract

The present application relates to the technical field of high-molecular phase change capsule, and is a kind of high-temperature heat-conducting phase change microcapsule for drilling fluid and a preparation method thereof.The raw materials of the former include phase change material, emulsifier, heat-conducting agent, epoxy resin and initiator, and are obtained by the following method: adding phase change material and emulsifier into organic solvent to obtain core material base fluid, and then adding epoxy resin, modified heat-conducting agent and initiator into the core material base fluid to react.The high-temperature heat-conducting phase change microcapsule for drilling fluid has the characteristics of good heat conductivity, good stability and recyclability.Meanwhile, the high-temperature heat-conducting phase change microcapsule for drilling fluid has good compatibility with drilling fluid, can quickly absorb heat in the well, effectively reduces the temperature of drilling fluid, and can be used in the drilling operation of deep well and ultra-deep well.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of high-molecular phase change capsules, and is a high-temperature heat-conducting phase change microcapsule for a drilling fluid and a preparation method thereof. BACKGROUND

[0002] In the process of drilling deep wells and ultra-deep wells, the formation temperature increases with the increase of depth, and the general temperature gradient is 2-3 DEG C per hundred meters. The formation temperature of some deep wells, ultra-deep wells and abnormal high-temperature wells in Tarim Oilfield, Xinjiang Oilfield and Qinghai Oilfield is mostly more than 175 DEG C, and the temperature of the target layer of some wells even reaches more than 200 DEG C. The excessively high formation temperature not only affects the performance of the drilling fluid, but also affects the service life of the measuring instrument and the safety of the drilling operation. However, the traditional drilling fluid cooling method is ground cooling, which cannot effectively solve the problem of high temperature in the wellbore. However, by adding a phase change material (PCM) to the drilling fluid, the PCM can be brought into the wellbore by the circulation of the drilling fluid, so that the temperature of the wellbore can be effectively reduced.

[0003] The PCM is a substance with high heat of fusion, which absorbs heat during phase change to store energy, has the characteristics of large heat storage per unit mass (volume), small temperature fluctuation (heat storage and release process is approximately isothermal), good chemical stability and good safety, etc. Common phase change processes mainly include solid-liquid and solid-solid phase changes. The solid-liquid phase change is to store heat through the melting process of the phase change material, and release heat through the solidification process; while the solid-solid phase change is to reversibly store and release heat through the change of the crystal structure of the phase change material or the order-disorder transition of the solid structure. Among them, the most widely used is the solid-liquid phase change material. This is because it can absorb or release a large amount of latent heat during the solid-liquid phase transition, and the temperature is constant and the heat transfer is stable, which is suitable for application in different actual scenes, and is a very promising heat storage material.

[0004] The PCM circulates with the drilling fluid in the wellbore, and its working principle is as follows: the PCM is in a solid state at low temperature, when the downhole temperature begins to rise, the PCM absorbs heat and keeps the temperature unchanged, when the temperature exceeds the melting point, the PCM begins to melt into a liquid state and stores heat in the liquid medium; during the upward process of the drilling fluid, the temperature begins to decrease, the PCM cools and solidifies, and releases heat.

[0005] The phase change material in the drilling fluid can be coated into a microcapsule by using a high polymer as an encapsulating agent. The reasons are as follows: (1) effectively solving the leakage problem of the phase change material, avoiding the reaction of the phase change material with the surrounding medium, and affecting the performance of the drilling fluid; (2) to avoid the phase change material from condensing into blocks during the phase change conversion process, which cannot pass through the sieve, thereby reducing the efficiency of the phase change material; (3) because it is wrapped in a microcapsule, the structural properties are relatively stable, and it can be used multiple times. However, the ordinary high polymer has poor thermal conductivity, and its thermal conductivity is relatively low, generally in the order of 0.1 W / (m·K), which cannot make the phase change material quickly absorb heat and cool down in the well, resulting in poor cooling efficiency. SUMMARY

[0006] The application provides a high-temperature thermal conductive phase change microcapsule for drilling fluid and a preparation method thereof, which overcomes the shortcomings of the prior art and effectively solves the problem of poor thermal conductivity of the existing high-molecular phase change capsule.

[0007] One of the technical solutions of the application is realized by the following measures: a high-temperature thermal conductive phase change microcapsule for drilling fluid, raw materials include 10-15 parts of phase change material, 3-5 parts of emulsifier, 10-15 parts of thermal conductive agent, 30-45 parts of epoxy resin and 20-30 parts of initiator by weight, and the phase change material is one or more of paraffin, D-sorbitol, xylitol, pentaerythritol and polyvinyl alcohol.

[0008] The following is a further optimization or / and improvement of the above-mentioned one of the technical solutions:

[0009] The phase change material is one of a mixture of paraffin and pentaerythritol, and a mixture of pentaerythritol and xylitol.

[0010] The mass ratio of paraffin to pentaerythritol in the mixture of paraffin and pentaerythritol is 1:(1.9-2.8), and the mass ratio of pentaerythritol to xylitol in the mixture of pentaerythritol and xylitol is (2.0-2.5):1.

[0011] The emulsifier is a surfactant, and the surfactant is castor oil polyoxyethylene ether.

[0012] The thermal conductive agent is one or more of hexagonal boron nitride, aluminum nitride, graphite powder, graphene, iron powder, copper powder, iron oxide and copper oxide.

[0013] The epoxy resin is E-type epoxy resin, and the initiator is bisphenol A.

[0014] The high-temperature thermal conductive phase change microcapsule for drilling fluid is obtained by the following method:

[0015] S1, adding a desired amount of a phase change material to an organic solvent, then adding a desired amount of an emulsifier, stirring uniformly, and obtaining a core material base solution;

[0016] S2, adding a desired amount of a thermal conductive agent to a mixed solution containing sodium hydroxide and propyl trimethoxysilane, and then performing ultrasonic treatment, to obtain a surface-modified thermal conductive agent;

[0017] S3, adding a desired amount of an epoxy resin and the surface-modified thermal conductive agent to the core material base solution, stirring uniformly, then adding a desired amount of an initiator, and performing reaction, to obtain a high-temperature thermal conductive phase change microcapsule for drilling fluid.

[0018] In the above step S1, the organic solvent is a cyclohexane aqueous solution and a cyclopentane aqueous solution with a mass concentration of 60% respectively, and the mass ratio of the phase change material to the organic solvent is 1: (25 to 30).

[0019] In the above step S1, the stirring temperature is 150 to 160 DEG C, the stirring speed is 110 to 130 r / min, and the stirring time is 20 to 25 min.

[0020] In the above step S2, the mass concentration of sodium hydroxide in the mixed solution is 10 to 15%, and the mass concentration of propyl trimethoxysilane in the mixed solution is 30 to 35%.

[0021] In the above step S2, the ultrasonic treatment time is 30 to 35 min.

[0022] In the above step S3, the reaction temperature is 150 to 160 DEG C, and the reaction time is 2.0 to 2.5 h.

[0023] The second technical solution of the present application is realized by the following measures: a preparation method of a high-temperature thermal conductive phase change microcapsule for drilling fluid, which is performed according to the following method:

[0024] S1, adding a desired amount of a phase change material to an organic solvent, then adding a desired amount of an emulsifier, stirring uniformly, and obtaining a core material base solution;

[0025] S2, adding a desired amount of a thermal conductive agent to a mixed solution containing sodium hydroxide and propyl trimethoxysilane, and then performing ultrasonic treatment, to obtain a surface-modified thermal conductive agent;

[0026] S3, adding a desired amount of an epoxy resin and the surface-modified thermal conductive agent to the core material base solution, stirring uniformly, then adding a desired amount of an initiator, and performing reaction, to obtain a high-temperature thermal conductive phase change microcapsule for drilling fluid.

[0027] The high-temperature heat-conducting phase change microcapsule for drilling fluid has the characteristics of good heat conductivity, good stability and recyclability, the heat conductivity of the microcapsule shell is enhanced by modifying the epoxy resin shell with the surface-modified heat conductor, and the heat absorption rate and heat conversion efficiency of the phase change material are significantly improved, meanwhile, the high-temperature heat-conducting phase change microcapsule for drilling fluid has good compatibility with drilling fluid, can quickly absorb heat in the well, effectively reduces the temperature of drilling fluid, and can be used in deep well and ultra-deep well drilling operations. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The SEM image of untreated hexagonal boron nitride.

[0029] Figure 2 The SEM image of the surface-modified hexagonal boron nitride obtained in step S2 of Example 15 of the present application.

[0030] Figure 3 The temperature change curve of the high-temperature water-based drilling fluid prepared by using the high-temperature heat-conducting phase change microcapsule for drilling fluid prepared in Example 15 of the present application as raw material. DETAILED DESCRIPTION

[0031] The present application is not limited by the following examples, and the specific implementation can be determined according to the technical scheme of the present application and the actual situation. The various chemical reagents and chemical products mentioned in the present application are well-known and commonly used chemical reagents and chemical products in the prior art unless otherwise specified; the percentages in the present application are mass percentages unless otherwise specified; the solution in the present application is an aqueous solution with water as the solvent unless otherwise specified, for example, a hydrochloric acid solution is a hydrochloric acid aqueous solution; the normal temperature and room temperature in the present application generally refer to a temperature of 15 to 25℃, and is generally defined as 25℃.

[0032] The present application will be further described below in conjunction with examples:

[0033] Example 1: The high-temperature heat-conducting phase change microcapsule for drilling fluid, the raw materials include 10 to 15 parts of phase change material, 3 to 5 parts of emulsifier, 10 to 15 parts of heat conductor, 30 to 45 parts of epoxy resin and 20 to 30 parts of initiator by weight, the phase change material is one or more of paraffin, D-sorbitol, xylitol, pentaerythritol and polyvinyl alcohol.

[0034] Example 2: As an optimization of the above-mentioned example, the phase change material is one of a mixture of paraffin and pentaerythritol, and a mixture of pentaerythritol and xylitol.

[0035] Example 3: As an optimization of the above examples, the mass ratio of paraffin and pentaerythritol in the mixture of paraffin and pentaerythritol is 1: (1.9 to 2.8), and the mass ratio of pentaerythritol to xylitol in the mixture of pentaerythritol and xylitol is (2.0 to 2.5):1.

[0036] In the phase change material of the present application, the phase change temperature of the mixture of paraffin and pentaerythritol can be controlled in the range of 150℃ to 180℃, which is suitable for high-temperature deep well drilling fluid; the phase change temperature of the mixture of pentaerythritol and xylitol can reach between 180℃ and 240℃; the melting point of pentaerythritol (PER) and polyvinyl alcohol (PVA) can reach 260℃, and the latent heat of phase change can reach 307J / g, i.e. the phase change temperature can reach 260℃, which is suitable for ultra-high-temperature ultra-deep well drilling fluid. Therefore, the appropriate phase change material can be selected according to the required phase change temperature.

[0037] Example 4: As an optimization of the above examples, the emulsifier is a surfactant, and the surfactant is castor oil polyoxyethylene ether.

[0038] Example 5: As an optimization of the above examples, the heat-conducting agent is one or more of hexagonal boron nitride, aluminum nitride, graphite powder, graphene, iron powder, copper powder, iron oxide and copper oxide.

[0039] In the present application, the heat-conducting agent is preferably hexagonal boron nitride, which has high heat resistance, high thermal conductivity and corrosion resistance, and is not easy to chemically react with the drilling fluid.

[0040] Example 6: As an optimization of the above examples, the epoxy resin is E-type epoxy resin, and the initiator is bisphenol A.

[0041] In the present application, the epoxy resin preferably has an epoxy value of 0.4 to 0.6, and the epoxy resin with an epoxy value between 0.4 and 0.6 has high strength and is not easy to be brittle, which is suitable for use in high-temperature deep wells.

[0042] Example 7: As an optimization of the above examples, the high-temperature heat-conducting phase change microcapsule for drilling fluid is obtained by the following method:

[0043] S1, a desired amount of phase change material is added to an organic solvent, and a desired amount of emulsifier is added and stirred uniformly to obtain a core material base solution;

[0044] S2, a desired amount of heat-conducting agent is added to a mixed solution containing sodium hydroxide and propyl trimethoxysilane and ultrasonicated to obtain a surface-modified heat-conducting agent;

[0045] S3, a desired amount of epoxy resin and surface-modified heat-conducting agent is added to the core material base solution and stirred uniformly, and a desired amount of initiator is added and reacted to obtain a high-temperature heat-conducting phase change microcapsule for drilling fluid.

[0046] Embodiment 8: As an optimization of the above embodiment, in step S1, the organic solvent is a 60% mass concentration cyclohexane aqueous solution and a 60% mass concentration cyclopentane aqueous solution, respectively, and the mass ratio of the phase change material to the organic solvent is 1: (25 to 30).

[0047] Embodiment 9: As an optimization of the above embodiment, in step S1, the stirring temperature is 150 to 160°C, the stirring speed is 110 to 130 r / min, and the stirring time is 20 to 25 min.

[0048] Embodiment 10: As an optimization of the above embodiment, in step S2, the mass concentration of sodium hydroxide in the mixed solution is 10 to 15%, and the mass concentration of propyl trimethoxysilane in the mixed solution is 30 to 35%.

[0049] Embodiment 11: As an optimization of the above embodiment, in step S2, the ultrasonic time is 30 to 35 min.

[0050] Embodiment 12: As an optimization of the above embodiment, in step S3, the reaction temperature is 150 to 160°C, and the reaction time is 2.0 to 2.5 h.

[0051] Embodiment 13:

[0052] The high-temperature heat-conducting phase change microcapsule for drilling fluid, raw materials include 10 parts of phase change material (pentaerythritol), 3 parts of emulsifier (castor oil polyoxyethylene ether), 10 parts of heat-conducting agent (hexagonal boron nitride), 30 parts of epoxy resin (E-type epoxy resin), and 20 parts of initiator (bisphenol A) by weight, and are obtained by the following method:

[0053] S1, a required amount of phase change material is added to an organic solvent (a 60% mass concentration cyclohexane aqueous solution), and a required amount of emulsifier is added, and after stirring at a temperature of 150°C and a speed of 110 r / min for 20 min, a core material base solution is obtained; wherein the mass ratio of the phase change material to the organic solvent is 1:25;

[0054] S2, a required amount of heat-conducting agent is added to a mixed solution containing sodium hydroxide and propyl trimethoxysilane and is ultrasonically treated for 30 min, to obtain a surface-modified heat-conducting agent; wherein the mass concentration of sodium hydroxide in the mixed solution is 10%, and the mass concentration of propyl trimethoxysilane in the mixed solution is 30%;

[0055] S3, a required amount of epoxy resin and surface-modified heat-conducting agent is added to the core material base solution and stirred uniformly, and then a required amount of initiator is added, and after reaction at 150°C for 2.0 h, a high-temperature heat-conducting phase change microcapsule for drilling fluid is obtained.

[0056] Embodiment 14:

[0057] The high-temperature heat-conducting phase change microcapsule for drilling fluid, raw materials include 15 parts of phase change material (polyvinyl alcohol), 5 parts of emulsifier (castor oil polyoxyethylene ether), 15 parts of heat conductor (aluminum nitride), 45 parts of epoxy resin (E-type epoxy resin) and 30 parts of initiator (bisphenol A) by weight, and is obtained by the following method:

[0058] S1, a required amount of phase change material is added to an organic solvent (60% cyclopentane aqueous solution by mass concentration), and a required amount of emulsifier is added, and after stirring at a temperature of 160°C and a rotating speed of 130 r / min for 25 min, a core material base solution is obtained; wherein the mass ratio of the phase change material to the organic solvent is 1:30;

[0059] S2, a required amount of heat conductor is added to a mixed solution containing sodium hydroxide and propyl trimethoxysilane, and after ultrasonic treatment for 35 min, the heat conductor after surface modification is obtained; wherein the mass concentration of sodium hydroxide in the mixed solution is 15%, and the mass concentration of propyl trimethoxysilane in the mixed solution is 35%;

[0060] S3, a required amount of epoxy resin and the heat conductor after surface modification is added to the core material base solution and stirred uniformly, and then a required amount of initiator is added, and after reaction at 160°C for 2.5 h, the high-temperature heat-conducting phase change microcapsule for drilling fluid is obtained.

[0061] Example 15:

[0062] The high-temperature heat-conducting phase change microcapsule for drilling fluid, raw materials include 12 parts of phase change material (a mixture of pentaerythritol and xylitol with a mass ratio of 2:1), 4 parts of emulsifier (castor oil polyoxyethylene ether), 15 parts of heat conductor (hexagonal boron nitride), 30 parts of epoxy resin (E-type epoxy resin) and 25 parts of initiator (bisphenol A) by weight, and is obtained by the following method:

[0063] S1, a required amount of phase change material is added to an organic solvent (60% cyclopentane aqueous solution by mass concentration), and a required amount of emulsifier is added, and after stirring at a temperature of 160°C and a rotating speed of 130 r / min for 25 min, a core material base solution is obtained; wherein the mass ratio of the phase change material to the organic solvent is 1:30;

[0064] S2, a required amount of heat conductor is added to a mixed solution containing sodium hydroxide and propyl trimethoxysilane, and after ultrasonic treatment for 35 min, the heat conductor after surface modification is obtained; wherein the mass concentration of sodium hydroxide in the mixed solution is 15%, and the mass concentration of propyl trimethoxysilane in the mixed solution is 35%;

[0065] S3, the required amount of epoxy resin, surface modified heat conductor is added to the core material base solution, stirring is uniform, then the required amount of initiator is added, after reaction at 150 DEG C for 2.0 h, the high temperature heat conducting phase change microcapsule for drilling fluid is obtained.

[0066] Example 16:

[0067] The high temperature heat conducting phase change microcapsule for drilling fluid, raw materials include 10 to 15 parts of phase change material (mass ratio of 1:2.5 mixture of paraffin and pentaerythritol), 4 parts of emulsifier (castor oil polyoxyethylene ether), 15 parts of heat conductor (hexagonal boron nitride), 30 parts of epoxy resin (E type epoxy resin) and 25 parts of initiator (bisphenol A) by weight, and the following method is used to obtain:

[0068] S1, a required amount of phase change material is added to an organic solvent (60% mass concentration of cyclohexane aqueous solution), then a required amount of emulsifier is added, after stirring at a temperature of 155 DEG C and a rotating speed of 120 r / min for 20 min, the core material base solution is obtained; wherein the mass ratio of phase change material to organic solvent is 1:28;

[0069] S2, a required amount of heat conductor is added to a mixed solution containing sodium hydroxide and propyl trimethoxysilane, and ultrasonic treatment is performed for 30 min, so that the surface modified heat conductor is obtained; wherein the mass concentration of sodium hydroxide in the mixed solution is 10%, and the mass concentration of propyl trimethoxysilane in the mixed solution is 30%;

[0070] S3, a required amount of epoxy resin and surface modified heat conductor is added to the core material base solution, stirring is uniform, then a required amount of initiator is added, after reaction at 150 DEG C for 2.0 h, the high temperature heat conducting phase change microcapsule for drilling fluid is obtained.

[0071] Compared with the prior art, the beneficial effects of the present application are that:

[0072] The high temperature heat conducting phase change microcapsule for drilling fluid can be used in deep wells and ultra-deep wells, the "core material" can select appropriate phase change materials according to the required phase change temperature, and the "packaging agent" selects the surface modified heat conductor, so that the heat conductivity is improved by more than ten times, the endothermic peak in the heating process is shifted to the low temperature area, the exothermic peak in the cooling process is shifted to the high temperature area, the supercooling degree of the high temperature heat conducting phase change microcapsule for drilling fluid is reduced, and the thermal cycle efficiency of the high temperature heat conducting phase change microcapsule for drilling fluid is improved.

[0073] The high temperature heat conducting phase change microcapsule for drilling fluid has a shell that is resistant to shearing, high temperature and corrosion, and is not easy to chemically react with substances in oil-based and water-based drilling fluids, so it can be used repeatedly. At the same time, it can be used for rapid cooling of high temperature drilling fluid, protecting downhole instruments and equipment, and ensuring the safe and efficient drilling process.

[0074] Example 17

[0075] The appearance of the surface-modified hexagonal boron nitride obtained in step S2 of Example 15 was observed by using an electron scanning microscope, and untreated hexagonal boron nitride was used as a control. The SEM image of the untreated hexagonal boron nitride is shown in FIG. 1, and the SEM image of the surface-modified hexagonal boron nitride obtained in step S2 of Example 15 is shown in FIG. 2. Figure 1 Figure 2 As can be seen from FIGS. 1 and 2, compared with the untreated hexagonal boron nitride, the surface of the surface-modified hexagonal boron nitride is smoother and more uniform. Figure 1 Figure 2

[0076] Example 18

[0077] Referring to the preparation method of Example 15, in the preparation process, the mass fraction of the epoxy resin was kept at 30 parts, and the addition amount of the heat conductor (hexagonal boron nitride) accounted for 0% (0 parts), 10% (3 parts), 20% (6 parts), 30% (9 parts), 40% (12 parts), and 50% (15 parts) of the mass of the epoxy resin, respectively, to obtain high-temperature heat-conducting phase change microcapsules for drilling fluid with different addition amounts of heat conductors. The heat-conducting properties and the temperature drop after 1 minute (the initial temperature was 200°C) of the high-temperature heat-conducting phase change microcapsules for drilling fluid with different addition amounts of heat conductors were tested.

[0078] The test results are shown in Table 1. As can be seen from Table 1, the addition of boron nitride can significantly improve the heat conductivity and cooling speed of the heat-conducting phase change microcapsules, and the higher the addition amount, the better the effect. When the addition amount accounts for 50% of the mass fraction of the epoxy resin, the temperature drop within 1 minute reaches 14.2°C. This is because a small amount of hexagonal boron nitride particles can only form discrete heat-conducting points in the polymer matrix, and with the increase of the content of hexagonal boron nitride, a three-dimensional heat-conducting network structure can be formed in the polymer matrix, and the heat-conducting heat flow can be smoothly transmitted along the channel, greatly improving the heat-conducting properties.

[0079] Example 19

[0080] ​​​The high-temperature heat-conducting phase change microcapsules for drilling fluid obtained in Embodiment 16 of the present application are formulated into a high-temperature water-based drilling fluid, and the cooling capacity of the high-temperature drilling fluid is investigated. The high-temperature water-based drilling fluid is prepared in the following manner: under stirring, 7 parts of bentonite, 5 parts of a filtration-reducing agent sulfomethyl lignite (SMC), 2 parts of sulfomethyl phenolic resin (SMP-1), 1 part of sulfonated asphalt, 1 part of a surfactant OP-10, 2 to 3 parts of a lubricant, 10 to 15 parts of the high-temperature heat-conducting phase change microcapsules for drilling fluid obtained in Embodiment 15 of the present application, and 0.2 parts of Na2Cr2O7 are added into 100 parts of clean water, and after continuous stirring for 25 minutes, caustic soda is added to control the pH value to be between 9 and 10, to obtain the high-temperature water-based drilling fluid. At the same time, a high-temperature water-based drilling fluid without the high-temperature heat-conducting phase change microcapsules for drilling fluid obtained in Embodiment 15 of the present application is formulated to serve as a control.

[0081] The high-temperature water-based drilling fluid is programmed to be heated to 200℃, and the temperature changes of the high-temperature water-based drilling fluids with and without the high-temperature heat-conducting phase change microcapsules for drilling fluid obtained in the present application are tested every five minutes, and the test results are shown in Figure 3 Figure 3 In the figure, A is the temperature change curve of the high-temperature water-based drilling fluid without the high-temperature heat-conducting phase change microcapsules for drilling fluid obtained in the present application, and B is the temperature change curve of the high-temperature water-based drilling fluid with the high-temperature heat-conducting phase change microcapsules for drilling fluid obtained in the present application, and it can be seen from the figure that the high-temperature water-based drilling fluid with the high-temperature heat-conducting phase change microcapsules for drilling fluid obtained in the present application has a phase change endothermic process at about 168℃, and a phase change platform appears, which effectively delays the temperature rise of the high-temperature water-based drilling fluid, and the actual temperature drop is up to 28℃. Figure 3

[0082] Embodiment 20: The high-temperature water-based drilling fluid prepared in Embodiment 19 of the present application is subjected to a “cyclic heating-natural cooling” test. The test results show that after five cycles, the high-temperature water-based drilling fluid can still be cooled by 25.3℃, indicating that the high-temperature heat-conducting phase change microcapsules for drilling fluid obtained in the present application have good stability and can be recycled.

[0083] In summary, the high-temperature heat-conducting phase change microcapsules for drilling fluid obtained in the present application have the characteristics of good heat conductivity, good stability and recyclability. The heat-conducting agent modified by surface modification is used to modify the epoxy resin shell, which enhances the heat conductivity of the microcapsule shell, significantly improves the heat absorption rate and heat conversion efficiency of the phase change material, and at the same time, the high-temperature heat-conducting phase change microcapsules for drilling fluid obtained in the present application have good compatibility with the drilling fluid, can quickly absorb heat underground, effectively reduce the temperature of the drilling fluid, and can be used in deep well and ultra-deep well drilling operations.

[0084] The above technical features constitute an embodiment of the present application, which has strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet different needs.​​

Claims

1. A high-temperature thermal conductive phase change microcapsule for drilling fluid, characterized in that The raw materials include, by weight, 10 to 15 parts of phase change material, 3 to 5 parts of emulsifier, 10 to 15 parts of thermal conductor, 30 to 45 parts of epoxy resin and 20 to 30 parts of initiator. The high-temperature thermal conductive phase change microcapsules for drilling fluid are obtained by modifying the epoxy resin shell with a thermal conductor surface-modified with propyltrimethoxysilane. The phase change material is one of a mixture of paraffin and pentaerythritol and a mixture of pentaerythritol and xylitol, and the thermal conductor is one or more of hexagonal boron nitride, aluminum nitride, graphite powder, graphene, iron powder, copper powder, iron oxide and copper oxide.

2. The high-temperature thermal conductive phase change microcapsule for drilling fluid according to claim 1, characterized in that The emulsifier is a surfactant, and the surfactant is castor oil polyoxyethylene ether.

3. The high-temperature thermal conductive phase change microcapsule for drilling fluid according to claim 1 or 2, characterized in that The epoxy resin is E-type epoxy resin, and the initiator is bisphenol A.

4. The high-temperature thermal conductive phase change microcapsule for drilling fluid according to claim 1 or 2, characterized in that The mass ratio of paraffin wax to pentaerythritol in the mixture of paraffin wax and pentaerythritol is 1:1.9 to 2.8, and the mass ratio of pentaerythritol to xylitol in the mixture of pentaerythritol and xylitol is 2.0 to 2.5:

1.

5. The high-temperature thermal conductive phase change microcapsule for drilling fluid according to claim 3, characterized in that The mass ratio of paraffin wax to pentaerythritol in the mixture of paraffin wax and pentaerythritol is 1:1.9 to 2.8, and the mass ratio of pentaerythritol to xylitol in the mixture of pentaerythritol and xylitol is 2.0 to 2.5:

1.

6. The high-temperature thermal conductive phase change microcapsule for drilling fluid according to claim 1, 2 or 5, characterized in that Obtained as follows: S1, adding a required amount of phase change material to an organic solvent, and then adding a required amount of emulsifier and stirring evenly to obtain a core material base liquid; S2, adding a required amount of thermal conductive agent to a mixed solution containing sodium hydroxide and propyltrimethoxysilane and performing ultrasonic treatment to obtain a surface-modified thermal conductive agent; S3, adding the required amount of epoxy resin and surface-modified thermal conductor to the core material base liquid and stirring evenly, then adding the required amount of initiator to react to obtain high-temperature thermal conductive phase change microcapsules for drilling fluid.

7. The high-temperature thermal conductive phase change microcapsule for drilling fluid according to claim 6, characterized in that In step S1, the organic solvents are a cyclohexane aqueous solution and a cyclopentane aqueous solution with a mass concentration of 60%, respectively, and the mass ratio of the phase change material to the organic solvent is 1:25 to 30; or / and, in step S1, the stirring temperature is 150°C to 160°C, the stirring speed is 110r / min to 130r / min, and the stirring time is 20min to 25min.

8. The high-temperature thermal conductive phase change microcapsule for drilling fluid according to claim 6, characterized in that In step S2, the mass concentration of sodium hydroxide in the mixed solution is 10% to 15%, and the mass concentration of propyltrimethoxysilane in the mixed solution is 30% to 35%.

9. The high-temperature thermal conductive phase change microcapsule for drilling fluid according to claim 7, characterized in that In step S2, the mass concentration of sodium hydroxide in the mixed solution is 10% to 15%, and the mass concentration of propyltrimethoxysilane in the mixed solution is 30% to 35%.

10. The high-temperature thermal conductive phase change microcapsule for drilling fluid according to claim 7, 8 or 9, characterized in that In step S2, the ultrasonic time is 30 min to 35 min; or / and, in step S3, the reaction temperature is 150° C. to 160° C., and the reaction time is 2.0 h to 2.5 h.

11. A method for preparing high-temperature thermal conductive phase change microcapsules for drilling fluid according to any one of claims 1 to 5 and 7 to 10, characterized in that Proceed as follows: S1, adding a required amount of phase change material to an organic solvent, and then adding a required amount of emulsifier and stirring evenly to obtain a core material base liquid; S2, adding a required amount of thermal conductive agent to a mixed solution containing sodium hydroxide and propyltrimethoxysilane and performing ultrasonic treatment to obtain a surface-modified thermal conductive agent; S3, adding the required amount of epoxy resin and surface-modified thermal conductor to the core material base liquid and stirring evenly, then adding the required amount of initiator to react to obtain high-temperature thermal conductive phase change microcapsules for drilling fluid.

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