High-temperature heat-conducting phase-change microcapsule for drilling fluid and preparation method thereof

Abstract

The invention relates to the technical field of polymer phase-change capsules, in particular to a high-temperature heat-conducting phase-change microcapsule for drilling fluid and a preparation method thereof.The high-temperature heat-conducting phase-change microcapsule comprises a phase-change material, an emulsifier, a heat-conducting agent, epoxy resin and an initiator, and the high-temperature heat-conducting phase-change microcapsule is obtained through the following steps that the phase-change material and the emulsifier are added into an organic solvent, and core material base liquid is obtained; and adding epoxy resin, the modified heat conduction agent and the initiator into the core material base solution, and reacting. The high-temperature heat-conducting phase-change microcapsule for the drilling fluid has the characteristics of good heat conductivity, good stability and recyclability, meanwhile, the high-temperature heat-conducting phase-change microcapsule for the drilling fluid has good compatibility with the drilling fluid, can quickly absorb heat underground and effectively reduce the temperature of the drilling fluid, and can be used in drilling operation of deep wells and ultra-deep wells.

Description

Technical Field

[0001] The invention relates to the technical field of polymer phase change capsules, in particular to high-temperature heat-conducting phase change microcapsules for drilling fluid and a preparation method thereof. Background Art

[0002] During the drilling of deep wells and ultra-deep wells, the formation temperature increases with increasing depth, and the general temperature gradient is 2°C to 3°C / 100 meters. The formation temperatures of some deep wells, ultra-deep wells, and abnormally high-temperature wells in Tarim Oilfield, Xinjiang Oilfield, and Qinghai Oilfield mostly exceed 175°C, and the target layers of some wells even reach above 200°C. Excessive formation temperature will not only affect the performance of the drilling fluid, but also affect the service life of the measuring instruments and the safety of drilling operations. The traditional method of cooling the drilling fluid is to cool the ground, which cannot effectively solve the problem of high temperature underground. However, adding phase change material (PCM) to the drilling fluid and using the circulation process of the drilling fluid to bring the PCM underground can effectively reduce the wellbore temperature.

[0003] PCM is a substance with high melting heat. When it undergoes phase change, it absorbs heat to achieve energy storage. It has the characteristics of large heat storage per unit mass (volume), small temperature fluctuation (storage and release process is approximately isothermal), good chemical stability and good safety. Common phase change processes are mainly of two types: solid-liquid and solid-solid phase change. Solid-liquid phase change stores heat through the melting process of phase change materials and releases heat through the solidification process; while solid-solid phase change reversibly stores and releases heat through changes in the crystal structure of phase change materials or the order-disorder transformation of solid structures. Among them, the most widely used is solid-liquid phase change material. This is because it absorbs or releases a large amount of phase change latent heat during the solid-liquid two-phase conversion process. At the same time, the temperature is constant and the heat transfer is stable. It is suitable for application in different practical scenarios and is a very promising thermal storage material.

[0004] PCM circulates in the wellbore with the drilling fluid. Its working principle is roughly as follows: PCM becomes solid at low temperatures. When the temperature downhole begins to rise, PCM absorbs heat and keeps the temperature constant. As the temperature exceeds the melting point, PCM begins to melt into liquid and stores heat in the liquid medium. As the drilling fluid rises, the temperature begins to drop, PCM cools and solidifies, and releases heat.

[0005] For phase change materials in drilling fluid, high molecular polymers can be used as encapsulants to encapsulate the phase change materials into microcapsules. The reasons are as follows: (1) It effectively solves the leakage problem of phase change materials and prevents them from reacting with the surrounding medium and affecting the performance of drilling fluid; (2) It prevents the phase change materials from condensing into blocks during the phase change conversion process and failing to be sieved, thereby reducing the efficiency of the phase change materials; (3) Because they are encapsulated in microcapsules, their structural properties are relatively stable and can be recycled many times. However, ordinary high molecular polymers have poor thermal conductivity and their thermal conductivity is relatively low, generally at the order of 0.1 W / (m·K). They cannot enable phase change materials to quickly absorb heat and cool down underground, resulting in poor cooling efficiency. Summary of the invention

[0006] The present invention provides a high-temperature heat-conducting phase-change microcapsule for drilling fluid and a preparation method thereof, which overcomes the above-mentioned deficiencies of the prior art and can effectively solve the problem of poor thermal conductivity of the existing polymer phase-change microcapsule.

[0007] One of the technical solutions of the present invention is achieved through the following measures: a high-temperature thermal conductive 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 thermal conductor, 30 to 45 parts of epoxy resin and 20 to 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 and / or improvement of one of the above-mentioned technical solutions: The phase change material is one of a mixture of paraffin and pentaerythritol and a mixture of pentaerythritol and xylitol.

[0009] The mass ratio of paraffin to pentaerythritol in the above-mentioned 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.

[0010] The emulsifier is a surfactant, and the surfactant is castor oil polyoxyethylene ether.

[0011] 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.

[0012] The epoxy resin is an E-type epoxy resin, and the initiator is bisphenol A.

[0013] The high temperature thermal conductive phase change microcapsules for drilling fluid are obtained by the following method: 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 conductor to a mixed solution containing sodium hydroxide and propyltrimethoxysilane and subjecting the mixture to ultrasonic treatment to obtain a surface-modified thermal conductor; S3, adding the required amount of epoxy resin and surface-modified thermal conductor to the core base liquid and stirring evenly, then adding the required amount of initiator to react, and obtaining high-temperature thermal conductive phase change microcapsules for drilling fluid.

[0014] In the above step S1, the organic solvents are cyclohexane aqueous solution and 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).

[0015] In the above step S1, the stirring temperature is 150° C. to 160° C., the stirring speed is 110 r / min to 130 r / min, and the stirring time is 20 min to 25 min.

[0016] In the above 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%.

[0017] In the above step S2, the ultrasonic time is 30 min to 35 min.

[0018] In the above step S3, the reaction temperature is 150° C. to 160° C., and the reaction time is 2.0 h to 2.5 h.

[0019] The second technical solution of the present invention is achieved by the following measures: A method for preparing high-temperature thermal conductive phase change microcapsules for drilling fluid is carried out 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 conductor to a mixed solution containing sodium hydroxide and propyltrimethoxysilane and subjecting the mixture to ultrasonic treatment to obtain a surface-modified thermal conductor; S3, adding the required amount of epoxy resin and surface-modified thermal conductor to the core base liquid and stirring evenly, then adding the required amount of initiator to react, and obtaining high-temperature thermal conductive phase change microcapsules for drilling fluid.

[0020] The high-temperature thermal conductive phase change microcapsules for drilling fluid of the present invention have the characteristics of good thermal conductivity, good stability and recyclability. The epoxy resin shell is modified by using a surface-modified thermal conductive agent, thereby enhancing the thermal conductivity of the microcapsule shell and significantly improving the heat absorption rate and heat conversion efficiency of the phase change material. At the same time, the high-temperature thermal conductive phase change microcapsules for drilling fluid of the present invention 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a SEM image of untreated hexagonal boron nitride.

[0022] Figure 2 This is a SEM image of the surface-modified hexagonal boron nitride obtained in step S2 of Example 15 of the present invention.

[0023] Figure 3 This is a temperature change curve of a high-temperature water-based drilling fluid prepared using the high-temperature thermal conductive phase change microcapsules for drilling fluid prepared in Example 15 of the present invention as raw materials. DETAILED DESCRIPTION

[0024] The present invention is not limited by the following embodiments, and the specific implementation method can be determined according to the technical scheme of the present invention and the actual situation. Unless otherwise specified, the various chemical reagents and chemicals mentioned in the present invention are all chemical reagents and chemicals known and used in the prior art; unless otherwise specified, the percentages in the present invention are all mass percentages; unless otherwise specified, the solutions in the present invention are all aqueous solutions with water as the solvent, for example, hydrochloric acid solution is a hydrochloric acid aqueous solution; the normal temperature and room temperature in the present invention generally refer to a temperature of 15°C to 25°C, and are generally defined as 25°C.

[0025] The present invention will be further described below in conjunction with embodiments: Example 1: The high-temperature thermal conductive phase change microcapsules 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 thermal 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.

[0026] Embodiment 2: As an optimization of the above embodiment, the phase change material is a mixture of paraffin and pentaerythritol, or a mixture of pentaerythritol and xylitol.

[0027] Example 3: As an optimization of the above example, the mass ratio of paraffin to 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.

[0028] In the phase change material of the present invention, the phase change temperature of the mixture of paraffin and pentaerythritol can be controlled within the range of 150°C to 180°C, 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°C and 240°C; the melting point of pentaerythritol (PER) and polyvinyl alcohol (PVA) can reach 260°C, and the phase change latent heat can reach 307J / g, that is, the phase change temperature can reach 260°C, which is suitable for ultra-high temperature and ultra-deep well drilling fluid. Therefore, a suitable phase change material can be selected according to the required phase change temperature.

[0029] Embodiment 4: As an optimization of the above embodiment, the emulsifier is a surfactant, and the surfactant is castor oil polyoxyethylene ether.

[0030] Embodiment 5: As an optimization of the above embodiment, 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.

[0031] In the present invention, the thermal conductor is preferably hexagonal boron nitride, because it has high heat resistance, high thermal conductivity, and corrosion resistance, and is not easy to chemically react with the drilling fluid.

[0032] Example 6: As an optimization of the above example, the epoxy resin is E-type epoxy resin, and the initiator is bisphenol A.

[0033] In the present invention, the epoxy resin preferably has an epoxy value of 0.4 to 0.6. The epoxy resin with an epoxy value between 0.4 and 0.6 has high strength and is not brittle, and is suitable for use in high-temperature deep wells.

[0034] Example 7: As an optimization of the above example, high temperature thermal conductive phase change microcapsules for drilling fluid are obtained according to the following method: 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 conductor to a mixed solution containing sodium hydroxide and propyltrimethoxysilane and subjecting the mixture to ultrasonic treatment to obtain a surface-modified thermal conductor; S3, adding the required amount of epoxy resin and surface-modified thermal conductor to the core base liquid and stirring evenly, then adding the required amount of initiator to react, and obtaining high-temperature thermal conductive phase change microcapsules for drilling fluid.

[0035] Example 8: As an optimization of the above example, in step S1, the organic solvents are cyclohexane aqueous solution and cyclopentane aqueous solution with mass concentrations of 60% respectively, and the mass ratio of the phase change material to the organic solvent is 1:(25 to 30).

[0036] Example 9: As an optimization of the above example, in step S1, the stirring temperature is 150°C to 160°C, the stirring speed is 110 r / min to 130 r / min, and the stirring time is 20 min to 25 min.

[0037] Example 10: As an optimization of the above example, 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%.

[0038] Example 11: As an optimization of the above example, in step S2, the ultrasonic time is 30 min to 35 min.

[0039] Example 12: As an optimization of the above example, in step S3, the reaction temperature is 150°C to 160°C, and the reaction time is 2.0h to 2.5h.

[0040] Embodiment 13: The high-temperature heat-conducting phase-change microcapsules for drilling fluids include, by weight, 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), and are obtained by the following method: S1, adding a required amount of phase change material to an organic solvent (cyclohexane aqueous solution with a mass concentration of 60%), and then adding a required amount of emulsifier, stirring for 20 minutes at a temperature of 150°C and a rotation speed of 110r / min, to obtain a core material base liquid; wherein the mass ratio of the phase change material to the organic solvent is 1:25; S2, adding a required amount of thermal conductor to a mixed solution containing sodium hydroxide and propyltrimethoxysilane and subjecting to ultrasonic treatment for 30 minutes to obtain a surface-modified thermal conductor; wherein the mass concentration of sodium hydroxide in the mixed solution is 10%, and the mass concentration of propyltrimethoxysilane in the mixed solution is 30%; S3, adding the required amount of epoxy resin and surface-modified thermal conductor to the core base liquid and stirring evenly, then adding the required amount of initiator, reacting at 150° C. for 2.0 h, and obtaining high-temperature thermal conductive phase change microcapsules for drilling fluid.

[0041] Embodiment 14: The high-temperature heat-conducting phase-change microcapsules for drilling fluids include, by weight, 15 parts of phase-change material (polyvinyl alcohol), 5 parts of emulsifier (castor oil polyoxyethylene ether), 15 parts of heat-conducting agent (aluminum nitride), 45 parts of epoxy resin (E-type epoxy resin) and 30 parts of initiator (bisphenol A), and are obtained by the following method: S1, adding a required amount of phase change material to an organic solvent (cyclopentane aqueous solution with a mass concentration of 60%), and then adding a required amount of emulsifier, stirring for 25 minutes at a temperature of 160°C and a rotation speed of 130r / min, to obtain a core material base liquid; wherein the mass ratio of the phase change material to the organic solvent is 1:30; S2, adding a required amount of thermal conductor to a mixed solution containing sodium hydroxide and propyltrimethoxysilane and subjecting to ultrasonic treatment for 35 minutes to obtain a surface-modified thermal conductor; wherein the mass concentration of sodium hydroxide in the mixed solution is 15%, and the mass concentration of propyltrimethoxysilane in the mixed solution is 35%; S3, adding the required amount of epoxy resin and surface-modified thermal conductor to the core base liquid and stirring evenly, then adding the required amount of initiator, reacting at 160° C. for 2.5 hours, and obtaining high-temperature thermal conductive phase change microcapsules for drilling fluid.

[0042] Embodiment 15: The high-temperature heat-conducting phase-change microcapsules for drilling fluids include, by weight, 12 parts of phase-change materials (a mixture of pentaerythritol and xylitol in a mass ratio of 2:1), 4 parts of emulsifiers (castor oil polyoxyethylene ether), 15 parts of heat-conducting agents (hexagonal boron nitride), 30 parts of epoxy resins (E-type epoxy resins) and 25 parts of initiators (bisphenol A), and are obtained by the following method: S1, adding a required amount of phase change material to an organic solvent (cyclohexane aqueous solution with a mass concentration of 60%), and then adding a required amount of emulsifier, stirring for 20 minutes at a temperature of 155°C and a rotation speed of 120r / min, to obtain a core material base liquid; wherein the mass ratio of the phase change material to the organic solvent is 1:28; S2, adding a required amount of thermal conductor to a mixed solution containing sodium hydroxide and propyltrimethoxysilane and subjecting to ultrasonic treatment for 30 minutes to obtain a surface-modified thermal conductor; wherein the mass concentration of sodium hydroxide in the mixed solution is 10%, and the mass concentration of propyltrimethoxysilane in the mixed solution is 30%; S3, adding the required amount of epoxy resin and surface-modified thermal conductor to the core base liquid and stirring evenly, then adding the required amount of initiator, reacting at 150° C. for 2.0 h, and obtaining high-temperature thermal conductive phase change microcapsules for drilling fluid.

[0043] Embodiment 16: The high-temperature heat-conducting phase-change microcapsules for drilling fluids include, by weight, 10 to 15 parts of phase-change materials (a mixture of paraffin wax and pentaerythritol in a mass ratio of 1:2.5), 4 parts of emulsifiers (castor oil polyoxyethylene ether), 15 parts of heat-conducting agents (hexagonal boron nitride), 30 parts of epoxy resins (E-type epoxy resins) and 25 parts of initiators (bisphenol A), and are obtained by the following method: S1, adding a required amount of phase change material to an organic solvent (cyclohexane aqueous solution with a mass concentration of 60%), and then adding a required amount of emulsifier, stirring for 20 minutes at a temperature of 155°C and a rotation speed of 120r / min, to obtain a core material base liquid; wherein the mass ratio of the phase change material to the organic solvent is 1:28; S2, adding a required amount of thermal conductor to a mixed solution containing sodium hydroxide and propyltrimethoxysilane and subjecting to ultrasonic treatment for 30 minutes to obtain a surface-modified thermal conductor; wherein the mass concentration of sodium hydroxide in the mixed solution is 10%, and the mass concentration of propyltrimethoxysilane in the mixed solution is 30%; S3, adding the required amount of epoxy resin and surface-modified thermal conductor to the core base liquid and stirring evenly, then adding the required amount of initiator, reacting at 150° C. for 2.0 h, and obtaining high-temperature thermal conductive phase change microcapsules for drilling fluid.

[0044] Compared with the prior art, the present invention has the following beneficial effects: The high-temperature thermal conductive phase change microcapsules for drilling fluid of the present invention can be used in deep wells and ultra-deep wells. The "core material" can select a suitable phase change material according to the required phase change temperature, and the "encapsulant" selects a surface-modified thermal conductive agent, and the thermal conductivity is improved by more than ten times, so that the endothermic peak in the heating process is shifted to the low temperature zone, and the exothermic peak in the cooling process is shifted to the high temperature zone, which reduces the supercooling of the high-temperature thermal conductive phase change microcapsules for drilling fluid of the present invention and improves the thermal cycle efficiency of the high-temperature thermal conductive phase change microcapsules for drilling fluid of the present invention.

[0045] The high-temperature heat-conducting phase-change microcapsules used in the drilling fluid of the present invention have 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, and can be recycled for multiple times. At the same time, it can be used to quickly cool down the high-temperature drilling fluid, protect downhole instruments and equipment, and ensure that the drilling process is carried out safely and efficiently.

[0046] Embodiment 17: The appearance of the surface-modified hexagonal boron nitride obtained in step S2 of Example 15 of the present invention was observed using an electron scanning microscope, and the untreated hexagonal boron nitride was used as a control. The SEM image of the untreated hexagonal boron nitride is as follows: Figure 1 As shown, the SEM image of the surface-modified hexagonal boron nitride obtained in step S2 of Example 15 of the present invention is as follows Figure 2 As shown by Figure 1 and Figure 2 As is known, compared with untreated hexagonal boron nitride, the surface of surface-modified hexagonal boron nitride is smoother and more evenly dispersed.

[0047] Embodiment 18: Referring to the preparation method of Example 15 of the present invention, during the preparation process, the mass fraction of epoxy resin is kept constant at 30 parts, and the addition amount of thermal conductor (hexagonal boron nitride) accounts for 0% (0 part), 10% (3 parts), 20% (6 parts), 30% (9 parts), 40% (12 parts), and 50% (15 parts) of the mass of epoxy resin, respectively, to obtain high-temperature thermal conductive phase change microcapsules for drilling fluid with different addition amounts of thermal conductor. The thermal conductivity and the drop temperature after 1 minute (initial temperature is 200°C) of high-temperature thermal conductive phase change microcapsules for drilling fluid with different addition amounts of thermal conductor are tested.

[0048] The test results are shown in Table 1. It can be seen from Table 1 that the addition of boron nitride can significantly improve the thermal conductivity and cooling rate of the thermally conductive phase change microcapsules, and the higher the amount added, the better the effect. When the addition amount accounts for 50% of the epoxy resin by mass, the temperature drops by 14.2°C within 1 minute. This is because a small amount of hexagonal boron nitride particles can only form discrete conductive hot spots in the polymer matrix, and as the content of hexagonal boron nitride increases, a three-dimensional thermal conductive network structure can be formed in the polymer matrix, and the thermal conductive heat flow can be smoothly transmitted along the channel, greatly improving its thermal conductivity.

[0049] Embodiment 19: The high-temperature thermal conductive phase change microcapsules for drilling fluid obtained in Example 16 of the present invention were formulated into high-temperature water-based drilling fluid to investigate the cooling ability of the high-temperature drilling fluid. The preparation method of the high-temperature water-based drilling fluid is as follows: under stirring, 7 parts of bentonite, 5 parts of sulfomethyl lignite (SMC), 2 parts of sulfomethyl phenolic resin (SMP-1), 1 part of sulfonated asphalt, 1 part of surfactant OP-10, 2 to 3 parts of lubricant, 10 to 15 parts of the high-temperature thermal conductive phase change microcapsules for drilling fluid obtained in Example 15 of the present invention, and 0.2 parts of Na2Cr2O7 were added to 100 parts of clean water. After continuing to stir for 25 minutes, caustic soda was added to control the pH value between 9 and 10 to obtain a high-temperature water-based drilling fluid. At the same time, a high-temperature water-based drilling fluid obtained without adding the high-temperature thermal conductive phase change microcapsules for drilling fluid obtained in Example 15 of the present invention was prepared as a control.

[0050] The high-temperature water-based drilling fluid was heated to 200°C, and the temperature changes of the high-temperature water-based drilling fluid obtained by adding and not adding the high-temperature thermal conductive phase change microcapsules for drilling fluid of the present invention were tested every five minutes. The test results are as follows: Figure 3 As shown, Figure 3 A is the temperature change curve of the high-temperature water-based drilling fluid obtained without adding the high-temperature thermal conductive phase change microcapsules for drilling fluid of the present invention, and B is the temperature change curve of the high-temperature water-based drilling fluid obtained by adding the high-temperature thermal conductive phase change microcapsules for drilling fluid of the present invention. Figure 3It can be seen that the high-temperature water-based drilling fluid obtained by adding the high-temperature thermal conductive phase change microcapsules for drilling fluid of the present invention undergoes phase change absorption at about 168°C, and a phase change platform appears, which effectively delays the temperature rise of the high-temperature water-based drilling fluid and actually reduces the temperature by 28°C.

[0051] Example 20: The high-temperature water-based drilling fluid prepared in Example 19 of the present invention was used to conduct a "cyclic heating-natural cooling" test. The test results showed that after five cycles, the high-temperature water-based drilling fluid could still be cooled by 25.3°C, indicating that the high-temperature thermal conductive phase change microcapsules used for drilling fluid of the present invention have good stability and can be recycled.

[0052] In summary, the high-temperature thermal conductive phase change microcapsules for drilling fluid of the present invention have the characteristics of good thermal conductivity, good stability and recyclability. The epoxy resin shell is modified by using a surface-modified thermal conductive agent, which enhances the thermal conductivity of the microcapsule shell and significantly improves the heat absorption rate and heat conversion efficiency of the phase change material. At the same time, the high-temperature thermal conductive phase change microcapsules for drilling fluid of the present invention 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.

[0053] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

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 phase change material is one or more of paraffin, D-sorbitol, xylitol, pentaerythritol and polyvinyl alcohol.

2. The high temperature thermal conductive phase change microcapsule for drilling fluid according to claim 1, characterized in that The phase change material is one of a mixture of paraffin wax and pentaerythritol and a mixture of pentaerythritol and xylitol.

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

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

5. The high temperature thermal conductive phase change microcapsule for drilling fluid according to claim 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.

6. The high temperature thermal conductive phase change microcapsule for drilling fluid according to any one of claims 1 to 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 conductor to a mixed solution containing sodium hydroxide and propyltrimethoxysilane and subjecting the mixture to ultrasonic treatment to obtain a surface-modified thermal conductor; S3, adding the required amount of epoxy resin and surface-modified thermal conductor to the core base liquid and stirring evenly, then adding the required amount of initiator to react, and obtaining 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 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; 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 or 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%.

9. The high temperature thermal conductive phase change microcapsule for drilling fluid according to claim 6, 7 or 8, 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.

10. 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 9, 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 conductor to a mixed solution containing sodium hydroxide and propyltrimethoxysilane and subjecting the mixture to ultrasonic treatment to obtain a surface-modified thermal conductor; S3, adding the required amount of epoxy resin and surface-modified thermal conductor to the core base liquid and stirring evenly, then adding the required amount of initiator to react, and obtaining high-temperature thermal conductive phase change microcapsules for drilling fluid.

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