Phase change encapsulated microspheres, early-strength low-hydraulic heat cement system and application thereof

Abstract

This invention discloses a phase change encapsulated microsphere, comprising a core carrier, an alkane material, and an epoxy resin; the alkane material is distributed inside the core carrier, and the epoxy resin coats the surface of the core carrier; wherein the alkane material includes tetradecane, pentadecane, and paraffin. The phase change encapsulated microsphere of this invention exhibits excellent heat storage performance and, when applied to cement systems, can significantly reduce the heat of hydration of cement, meeting the requirements of cementing under low-temperature conditions.

Description

Technical Field

[0001] This invention relates to the field of cementing materials for oil and gas wells, specifically to a phase change encapsulated microsphere, an early-strength low-heat hydration cement system and its applications, particularly a hydrophilic phase change encapsulated microsphere and an early-strength low-heat hydration cement system for cementing deep-sea hydrate layers or permafrost hydrate layers. It is a cement system particularly suitable for the low-temperature environment of marine hydrate layers, and also suitable for cementing operations in extremely cold permafrost layers. Background Technology

[0002] Currently, the main cementing systems used in deep-sea and permafrost cementing systems both domestically and internationally include: (1) rapid-setting cement slurry system; (2) particle-graded cement system; (3) high-alumina cement slurry system; (4) low-heat slag-activated cement system; and (5) foamed cement system. Most low-temperature cementing systems only consider the early strength performance of cement and ignore the possibility of hydrates in the cementing formation. The cement system has a high heat release during hydration, which is not conducive to the stability of natural gas hydrates, thus posing a huge safety hazard.

[0003] The depth of shallow hydrate layers in deep water is typically 500-1500m, and the stable ambient temperature range for natural gas hydrates is 7-20℃. Existing research on low-heat hydration cement and admixtures largely neglects the early-strength properties of cement, and the excessively high phase transition temperature ranges of the studied materials often fail to inhibit hydrate decomposition.

[0004] Patent CN105733519A discloses a hydrophilic paraffin microcapsule and an early-strength, low-hydration exothermic cement system. It employs a suspension polymerization method to encapsulate phase change materials within methyl methacrylate microspheres and uses a special dispersant to develop hydrophilic phase change microcapsules. Adding these microcapsules to cement slurry can significantly reduce the exothermic hydration of cement and has minimal impact on the strength properties of cement paste. However, the preparation process of these phase change microcapsules is complex, requiring high-performance materials. Using different batches of materials may lead to microcapsule preparation failure, making industrialization difficult.

[0005] In summary, existing technologies for preparing low-heat-of-hydration cement systems have the problem of failing to balance early strength and low-heat-of-hydration performance. Summary of the Invention

[0006] To address the aforementioned problems in existing technologies, this invention provides a phase change encapsulated microsphere with excellent heat storage performance, capable of reducing the heat of hydration of cement while maintaining its early strength. This invention also provides a method for preparing the aforementioned phase change encapsulated microsphere, an early-strength, low-heat-of-hydration cement system, and its applications.

[0007] The first aspect of the present invention provides a phase change encapsulated microsphere, comprising a core material carrier, an alkane material, and an epoxy resin; wherein the alkane material is distributed inside the core material carrier, and the epoxy resin coats the surface of the core material carrier;

[0008] Among them, alkane materials include tetradecane, pentadecane, and paraffin.

[0009] According to some embodiments of the present invention, the mass ratio of tetradecane:pentadecane:paraffin in the alkane material is 4~6:9~11:24~26.

[0010] According to some embodiments of the present invention, the mass ratio of tetradecane:pentadecane:paraffin in the alkane material is 5:10:25.

[0011] According to some embodiments of the present invention, the mass ratio of core material carrier: alkane material: epoxy resin is 4~5:9~11:2~3.

[0012] According to some embodiments of the present invention, the mass ratio of core material carrier: alkane material: epoxy resin is 4.5:10:2.5.

[0013] According to some embodiments of the present invention, the core material carrier is a hollow microsphere, the hollow microsphere comprising a shell and an internal cavity formed by the shell, the shell being a porous medium material.

[0014] According to some embodiments of the present invention, the outer shell is a high-strength polymer porous medium material, and the high-strength polymer porous medium material has a compressive strength ≥20MPa.

[0015] Specifically, the compressive strength is measured using a nanoindenter.

[0016] According to some embodiments of the present invention, the outer shell is an alkali-activated polymer porous medium material.

[0017] According to some embodiments of the present invention, the average particle size of the core material carrier is 200-300 μm, preferably 240-260 μm, and more preferably 250 μm.

[0018] According to some embodiments of the present invention, the average diameter of the internal cavity of the core material carrier is 100-200 μm, preferably 140-160 μm, and more preferably 150 μm.

[0019] According to some embodiments of the present invention, the phase change encapsulated microspheres comprise nanoscale dispersed particles, which are dispersed on the surface of the epoxy resin.

[0020] According to some embodiments of the present invention, the nanoscale dispersed particles are one or more of nano-silica, nano-alumina, and nano-calcium carbonate.

[0021] According to some embodiments of the present invention, the mass ratio of the core material carrier to the nanoscale dispersed particles is 4~5:2~3.

[0022] According to some embodiments of the present invention, the mass ratio of the core material carrier to the nanoscale dispersed particles is 4.5:2.5.

[0023] A second aspect of the present invention provides a method for preparing the phase change encapsulated microspheres described in the first aspect, comprising the following preparation steps:

[0024] (1) A mixture of tetradecane, pentadecane and paraffin is used to obtain an alkane material;

[0025] (2) Adsorb the alkane material into the core material carrier;

[0026] (3) Epoxy resin is coated on the surface of the core material carrier carrying alkane material to obtain phase change encapsulated microspheres.

[0027] A third aspect of the present invention provides an early-strength, low-heat-of-hydration cement system, comprising the phase-change encapsulated microspheres described in the first aspect.

[0028] According to some embodiments of the present invention, the content of the phase change encapsulated microspheres is 5 to 30 parts per 100 parts by weight of cement.

[0029] According to some embodiments of the present invention, the content of the phase change encapsulated microspheres is 5 to 25 parts per 100 parts by weight of cement.

[0030] According to some embodiments of the present invention, the product comprises the following components in parts by weight:

[0031] 100 parts cement;

[0032] 5-30 parts of phase change encapsulated microspheres;

[0033] 10-20 parts of density-reducing material;

[0034] 1-2 parts of dehydration reducer;

[0035] Early-strength agent: 0.05~0.3 parts;

[0036] 54-62 parts water.

[0037] According to some embodiments of the present invention, the cement is an aluminate-silicate composite cement.

[0038] According to some embodiments of the present invention, the early strength agent is an organic Mannich base early strength agent.

[0039] According to some embodiments of the present invention, the aluminate-silicate composite cement includes aluminate cement and silicate cement, wherein the mass ratio of silicate cement to aluminate cement is 2.5~3.5:6.5~7.5.

[0040] According to some embodiments of the present invention, the aluminate-silicate composite cement includes aluminate cement and silicate cement, wherein the mass ratio of silicate cement to aluminate cement is 3:7.

[0041] A fourth aspect of the present invention provides the application of the phase change encapsulated microspheres described in the first aspect in reducing the exothermic reaction of cement hydration.

[0042] The fifth aspect of the invention provides the application of the cement system described in the third aspect in cryogenic cementing, particularly in cryogenic cementing of deep-sea hydrate formations and permafrost hydrate formations.

[0043] (1) In this invention, phase change encapsulated microspheres are incorporated into the cement system. The alkanes in the phase change encapsulated microspheres absorb heat during the solid-liquid phase change, thereby reducing the hydration heat of the cement system. Multiple alkanes combined can be used in cement systems with water Temperature rise (4~40℃) The cement system continuously absorbs heat of hydration during the cementing process, resulting in a lower heat of hydration and thus preventing or reducing the decomposition of hydrates, ensuring the stability of the hydrate layer during the cementing process.

[0044] (2) Alkane materials also possess low density, which can reduce the density of cement systems. Encapsulating alkane materials... After installation It can effectively solve the problem of incompatibility between alkane materials and cement slurry, and ensure the mechanical strength of cement.

[0045] (3) The aluminate cement used in this invention has excellent early strength characteristics at low temperatures. Unlike conventional silicate cement, aluminate cement also has excellent hydration capacity at 0℃. Adding aluminate cement to G-grade silicate cement can improve the overall low-temperature hydration capacity, and it still has high early strength at low temperatures. At the same time, aluminate cement has low-temperature expansion properties, and micro-expansion will occur during solidification at low temperatures. This characteristic ensures that the cement sheath does not shrink during low-temperature cementing, prevents the appearance of micro-annular gaps in the cement sheath, and effectively ensures the cementing bonding quality.

[0046] (4) The main body of the cement system of the present invention is a mixture of G-grade oil well cement and aluminate cement. Aluminate cement can promote the hydration reaction rate of the overall cement system and improve early strength; the heat of hydration of G-grade silicate cement is much lower than that of aluminate cement, which significantly reduces the heat of hydration of the overall cement system. This makes the cement system provided by the present invention have both high early strength and low heat of hydration.

[0047] (5) The early-strength low-heat hydration cement system provided by the present invention has high strength in the early stage under low temperature (2-10℃) conditions. Attached Figure Description

[0048] Figure 1 This is a micrograph of the phase change encapsulated microsphere 1 of the present invention.

[0049] Figure 2 This is a test result of the phase change encapsulated microsphere 1 of the present invention at 20°C for alkali resistance.

[0050] Figure 3 This is a test result of the phase change encapsulated microsphere 1 of the present invention at 75°C for alkali resistance.

[0051] Figure 4 Temperature curves showing the hydration heat performance of the cement system provided in Examples 5-8 and Comparative Example 1 of the present invention.

[0052] Figure 5 The hydration exothermic test temperature curves of the cement system provided in Examples 9-10 and Comparative Examples 2-3 of the present invention are shown.

[0053] Figure 6 Temperature curves showing the heat of hydration performance of the cement system provided in Embodiment 11 and Comparative Examples 4-6 of the present invention. Detailed Implementation

[0054] To make the present invention easier to understand, the present invention will be described in detail below with reference to embodiments. These embodiments are for illustrative purposes only and are not limited to the scope of application of the present invention.

[0055] According to some embodiments of the present invention, the epoxy resin is a modified waterborne low-temperature curing epoxy resin.

[0056] According to some embodiments of the present invention, the paraffin is an alkane material with 28 carbon atoms, abbreviated as paraffin C. 28 .

[0057] According to some embodiments of the present invention, the preparation method of the core material carrier includes synthesizing an alkali-activated geopolymer using a reverse suspension polymerization method and sintering it at high temperature to form high-strength porous media microspheres.

[0058] According to some embodiments of the present invention, the sintering temperature is 600-700℃, preferably 650℃.

[0059] According to some embodiments of the present invention, the absorption method of step (2) includes immersing the core material carrier in molten alkane material, then evacuating and removing the air to separate the core material carrier carrying the alkane material.

[0060] According to some embodiments of the present invention, the suction pressure is -0.05 to -0.15 MPa.

[0061] According to some embodiments of the present invention, the suction pressure is -0.1 MPa.

[0062] According to some embodiments of the present invention, the suction temperature is 55~65°C.

[0063] According to some embodiments of the present invention, the suction is performed under vacuum conditions.

[0064] According to some embodiments of the present invention, step (3) after coating with epoxy resin further includes adding nanoscale dispersing particles and stirring to separate and obtain phase change encapsulated microspheres.

[0065] According to some embodiments of the present invention, after the epoxy resin solidifies in step (3), the microspheres are sieved away from the excess nano-dispersed particles to obtain phase change encapsulated microspheres.

[0066] According to some embodiments of the present invention, the particle size of the nanoscale dispersed particles is 1-100 nm, preferably 10-50 nm, and more preferably 30 nm.

[0067] According to some embodiments of the present invention, the operating temperature of step (3) is 2~4°C.

[0068] According to some embodiments of the present invention, the silicate cement is grade G silicate cement.

[0069] According to some embodiments of the present invention, the amount of phase change encapsulated microspheres added is 5 to 25 parts, for example, the amount of phase change encapsulated microspheres added can be 10 parts, 15 parts or 20 parts.

[0070] According to some embodiments of the present invention, the density-reducing material is one or both of hollow glass beads and microsilica.

[0071] According to some embodiments of the present invention, the mass ratio of the hollow glass float to the microsilicon is 4.5~5.5:1.5~2.5.

[0072] According to some embodiments of the present invention, the mass ratio of the hollow glass beads to the microsilicon is 5:2;

[0073] According to some embodiments of the present invention, the actual density of the hollow glass float is 0.75~0.85 g / cm³. 3 And / or compressive strength of 82.5~83MPa, and / or average particle size of 34~36μm.

[0074] According to some embodiments of the present invention, the hollow glass float is Y6000 or Y12000.

[0075] According to some embodiments of the present invention, the microsilicon is silicon dioxide.

[0076] According to some embodiments of the present invention, the average particle size of the microsilicon is 0.02~0.5μm.

[0077] According to some embodiments of the present invention, the water loss reducing agent is BXF-200.

[0078] According to some embodiments of the present invention, the organic Mannich base early-strength agent of the present invention uses mono- or multi-component organic aldehydes and alkanolamines as reactants. Under certain temperature and suitable environment, they undergo a Mannich base chemical reaction with mono- or multi-component organic acids to generate an organic polymer. The organic Mannich base early-strength agent can be used in deep-water, low-temperature cementing processes to accelerate the thickening and solidification of cement slurry, forming an effective cement sheath between the casing and the wellbore to support the wellbore and prevent water and gas channeling. The organic Mannich base early-strength agent added to the cement system of the present invention has advantages such as small dosage, significant accelerating and early-strength effect, no pollution, and low cost.

[0079] In this invention, the alkali-activated geopolymer was purchased from Jiaozuo Yukun Mining Co., Ltd., with CAS number 12141-46-7 and molecular weight of 162.

[0080] Tetradecane was purchased from Sinopharm Chemical Reagent Co., Ltd., CAS No. 629-59-4;

[0081] Pentadecane was purchased from Sinopharm Chemical Reagent Co., Ltd., CAS No. 629-62-9;

[0082] Paraffin C 28 Purchased from Zhenjiang Runzhou District Zezhong Special Wax Factory Co., Ltd., CAS No. 8002-74-2;

[0083] The epoxy resin was purchased from Guangzhou Tengfa Chemical Co., Ltd., CAS No. 61788-97-4;

[0084] Nano-silica was purchased from Shouguang Changtai New Materials Co., Ltd.

[0085] Nano-alumina was purchased from Shanghai Chaowei Nanotechnology Co., Ltd.

[0086] Nano-calcium carbonate was purchased from Dongguan Panshi New Materials Co., Ltd.

[0087] Grade G silicate was purchased from Sichuan Jiahua Special Cement Co., Ltd.

[0088] Aluminate cement was purchased from Zhengzhou Hongzheng Refractory Materials Co., Ltd.

[0089] The dehydration reducer was purchased from Tianjin Zhongyou Boxing Engineering Technology Co., Ltd.

[0090] The organic Mannich base early strength agent was prepared in-house, and the preparation method was based on Example 1 of the patent with publication number CN101333171A.

[0091] The microsilicon was purchased from Henan Xinxing Building Materials Co., Ltd., and its main component is silicon dioxide.

[0092] Hollow glass float beads were purchased from Sinosteel Group Maanshan Mining Research Institute New Materials Technology Co., Ltd.

[0093] The dispersant was purchased from Jinan Shunxin Chemical Co., Ltd.

[0094] Example 1

[0095] Preparation of phase change encapsulated microspheres (PCMM) 1.

[0096] Alkali-activated geopolymers were synthesized using reverse-phase suspension polymerization and sintered at high temperature (600℃) to form porous media microspheres (250 μm in diameter and 150 μm in pore size). Then, tetradecane, pentadecane, and paraffin C were added... 28 Porous media microspheres were mixed and melted at a mass ratio of 5:10:25. These microspheres were then immersed in molten alkane material. The alkane material containing the microspheres was then subjected to vacuum extraction at -0.1 MPa and 60°C to remove air. The microspheres were then separated from the alkane material. At 2–4°C, the microspheres were mixed with epoxy resin to uniformly coat the surface of the microspheres. Nanoscale dispersing particles were then added and stirred at 300 r / min for 1 hour to disperse the microspheres. After the epoxy resin solidified, the microspheres and excess nanoscale dispersing particles were sieved to obtain encapsulated energy storage microspheres. The mass ratio of porous media microspheres, epoxy resin, and nanoscale dispersing particles was 4.5:10:2.5. The nanoscale dispersing particles consisted of nano-silica, nano-alumina, and nano-calcium carbonate.

[0097] The prepared phase change encapsulated microspheres were photographed using a microscope, and the resulting micrographs are shown below. Figure 1 As shown. From Figure 1 It can be seen that the phase change encapsulated microspheres prepared in Example 1 have good sphericity and uniform particle size. The surface of the microspheres is covered by dense epoxy resin, and there is no leakage of thermal energy storage agent.

[0098] Example 2

[0099] 2. Preparation of phase change encapsulated microspheres.

[0100] Alkali-activated geopolymers were synthesized using reverse suspension polymerization and sintered at high temperature (650℃) to form porous media microspheres (250 μm in diameter and 150 μm in pore size). Then, tetradecane, pentadecane, and paraffin C were added... 28Porous media microspheres were mixed and melted at a mass ratio of 2.5:2.5:5. The microspheres were then immersed in molten alkane material. The alkane material containing the microspheres was then placed under vacuum at -0.1 MPa and 60°C to remove air. The microspheres were then separated from the alkane material. The microspheres were mixed with epoxy resin at 2–4°C to uniformly coat the surface of the microspheres. Nanoscale dispersing particles were then added and stirred at 300 r / min for 1 hour to disperse the microspheres. After the epoxy resin solidified, the microspheres and excess nanoscale dispersing particles were sieved to obtain encapsulated energy storage microspheres. The mass ratio of porous media microspheres, epoxy resin, and nanoscale dispersing particles was 4:10:3. The nanoscale dispersing particles consisted of nano-silica, nano-alumina, and nano-calcium carbonate.

[0101] Example 3

[0102] 3. Preparation of phase change encapsulated microspheres.

[0103] Alkali-activated geopolymers were synthesized using reverse suspension polymerization and sintered at high temperature (650℃) to form porous media microspheres (250 μm in diameter and 150 μm in pore size). Then, tetradecane, pentadecane, and paraffin C were added... 28 Porous media microspheres were mixed and melted at a mass ratio of 6:9:26. These microspheres were then immersed in molten alkane material. The alkane material containing the microspheres was then subjected to vacuum extraction at -0.1 MPa and 60°C to remove air. The microspheres were then separated from the alkane material. At 2–4°C, the microspheres were mixed with epoxy resin to uniformly coat the surface of the microspheres. Nanoscale dispersing particles were then added and stirred at 300 r / min for 1 hour to disperse the microspheres. After the epoxy resin solidified, the microspheres and excess nanoscale dispersing particles were sieved to obtain encapsulated energy storage microspheres. The mass ratio of porous media microspheres, epoxy resin, and nanoscale dispersing particles was 5:9:2. The nanoscale dispersing particles consisted of nano-silica, nano-alumina, and nano-calcium carbonate.

[0104] Example 4

[0105] 4. Preparation of phase change encapsulated microspheres.

[0106] Alkali-activated geopolymers were synthesized using reverse suspension polymerization and sintered at high temperature (650℃) to form porous media microspheres (250 μm in diameter and 150 μm in pore size). Then, tetradecane, pentadecane, and paraffin C were added... 28Porous media microspheres were mixed and melted at a mass ratio of 25:5:10. These microspheres were then immersed in molten alkane material. The alkane material containing the microspheres was then subjected to vacuum extraction at -0.1 MPa and 60°C to remove air. The microspheres were then separated from the alkane material. At 2–4°C, the microspheres were mixed with epoxy resin to uniformly coat the surface of the microspheres. Nanoscale dispersing particles were then added and stirred at 300 r / min for 1 hour to disperse the microspheres. After the epoxy resin solidified, the microspheres and excess nanoscale dispersing particles were sieved to obtain encapsulated energy storage microspheres. The mass ratio of porous media microspheres, epoxy resin, and nanoscale dispersing particles was 4.5:10:2.5. The nanoscale dispersing particles consisted of nano-silica, nano-alumina, and nano-calcium carbonate.

[0107] Example 5

[0108] Prepare a high-early-strength, low-heat-of-hydration cement system for PCMM5.

[0109] The cement formula consists of 100 parts of Grade G silicate cement, 5 parts of PCMM, 2 parts of water loss reducing agent, 4 parts of microsilica, 10 parts of hollow glass cenospheres, 0.22 parts of organic Mannich alkali accelerator and 54.7 parts of water.

[0110] PCMM stands for Phase Change Encapsulated Microsphere 1.

[0111] Example 6

[0112] Prepare a high-early-strength, low-heat-of-hydration cement system for PCMM10.

[0113] The cement formula consists of 100 parts of Grade G silicate cement, 10 parts of PCMM, 2 parts of water loss reducing agent, 5 parts of microsilica, 9 parts of hollow glass cenospheres, 0.15 parts of organic Mannich alkali accelerator and 58 parts of water.

[0114] PCMM is phase change encapsulated microsphere 2.

[0115] Example 7

[0116] Prepare a high-early-strength, low-heat-of-hydration cement system for PCMM20.

[0117] The cement formula consists of 100 parts of Grade G silicate cement, 20 parts of PCMM, 1 part of water loss reducing agent, 3 parts of microsilica, 11 parts of hollow glass cenospheres, 0.3 parts of organic Mannich alkali accelerator and 62 parts of water.

[0118] PCMM refers to phase change encapsulated microspheres 3.

[0119] Example 8

[0120] Prepare a high-early-strength, low-heat-of-hydration cement system for PCMM30.

[0121] The cement formula consists of 100 parts of Grade G silicate cement, 30 parts of PCMM, 2 parts of water loss reducing agent, 4 parts of microsilica, 10 parts of hollow glass cenospheres, 0.22 parts of organic Mannich alkali accelerator and 54.7 parts of water.

[0122] PCMM stands for Phase Change Encapsulated Microsphere 1.

[0123] Example 9

[0124] Prepare a high-early-strength, low-heat-of-hydration cement system for PCMM25.

[0125] The cement formula consists of 100 parts of Grade G silicate cement, 4 parts of microsilica, 10 parts of hollow glass cenospheres, 2 parts of water loss reducing agent, 0.22 parts of organic Mannich base early strength agent, 0.2 parts of dispersant, 25 parts of PCMM, and 54.7 parts of water.

[0126] PCMM stands for Phase Change Encapsulated Microsphere 1.

[0127] Example 10

[0128] Prepare a high-early-strength, low-heat-of-hydration cement system for PCMM25.

[0129] The cement formula consists of 30 parts of G-grade silicate cement, 70 parts of aluminate cement, 4 parts of microsilica, 10 parts of hollow glass cenospheres, 2 parts of water loss reducing agent, 0.22 parts of organic Mannich base early strength agent, 0.2 parts of dispersant, 25 parts of PCMM, and 54.7 parts of water.

[0130] Wherein: PCMM is phase change encapsulated microsphere 1; the mineral composition and mass percentage of 30 parts of G-grade silicate cement and 70 parts of aluminate cement are: alumina 42.6%, calcium oxide 40.3%, silicon dioxide 9.5%, iron oxide 2.1%, titanium oxide 2%, sulfur trioxide 1.3%, magnesium oxide 1.1%, and the balance is trace elements.

[0131] Example 11

[0132] Prepare a high-early-strength, low-heat-of-hydration cement system for PCMM10.

[0133] The cement formula consists of 100 parts of Grade G silicate cement, 10 parts of PCMM, 2 parts of water loss reducing agent, 4 parts of microsilica, 10 parts of hollow glass cenospheres, 0.05 parts of organic Mannich alkali accelerator and 54.7 parts of water.

[0134] PCMM is phase change encapsulated microsphere 4.

[0135] Comparative Example 1

[0136] Prepare a cement system for PCMM0.

[0137] The cement formula consists of 100 parts of Grade G silicate cement, 2 parts of water loss reducing agent, 4 parts of microsilica, 10 parts of cenospheres, 0.22 parts of organic Mannich base accelerator and 54.7 parts of water.

[0138] Comparative Example 2

[0139] Preparation of cement system.

[0140] The cement formula consists of 100 parts aluminate cement and 44 parts water.

[0141] Comparative Example 3

[0142] Preparation of cement system.

[0143] The cement formula consists of 100 parts of G-grade silicate cement and 44 parts of water.

[0144] Comparative Example 4

[0145] Preparation of cement system.

[0146] The cement formula is the same as in Example 5, except that in the preparation method of PCMM, "tetradecane, pentadecane and paraffin C" are added. 28 Replace "mix and melt according to a mass ratio of 5:10:25" with "mix pentadecane and paraffin C". 28 Mix and melt according to a mass ratio of 2:5.

[0147] Comparative Example 5

[0148] Preparation of cement system.

[0149] The cement formula is the same as in Example 5, except that in the preparation method of PCMM, "tetradecane, pentadecane and paraffin C" are added. 28 Replace "mix and melt according to a mass ratio of 5:10:25" with "mix and melt tetradecane and pentadecane according to a mass ratio of 1:2".

[0150] Comparative Example 6

[0151] Preparation of cement system.

[0152] The cement formula is the same as in Example 5, except that in the preparation method of PCMM, "tetradecane, pentadecane and paraffin C" are added. 28 Replace "mix and melt according to a mass ratio of 5:10:25" with "mix tetradecane and paraffin C". 28 Mix and melt them according to a mass ratio of 1:5.

[0153] Test Example 1

[0154] The phase change encapsulated microsphere 1 was tested for alkali resistance at 20℃ and 75℃.

[0155] The alkali resistance test results are shown below. Figure 2and Figure 3 As shown. By Figure 2 and Figure 3 It can be seen that the mass change rate of phase change encapsulated microsphere 1 did not fluctuate significantly under pH conditions of 7-14, indicating that epoxy resin can play a good encapsulation role in alkaline environments at 20℃ and 75℃ and can resist corrosion from alkaline solutions of different temperatures and concentrations.

[0156] Test Example 2

[0157] Hydration exothermic test.

[0158] Cement slurry was prepared according to API 10B-2-2013 standard using the cement formulations of Examples 5-8 and Comparative Example 1. The exothermic reaction of cement hydration was tested using the direct method, and the hydration exothermic process was characterized using exothermic temperature curves. Figure 4 As shown.

[0159] According to the test results, the hydration heat release temperature of PCMM0 is significantly higher than that of PCMM5 to PCMM30, indicating that the early-strength, low-heat-of-hydration cement system provided by this invention significantly reduces the hydration heat release temperature of the cement after the addition of PCMM, and the low-heat-of-hydration characteristics improve with the increase of PCMM dosage. This demonstrates that the phase change encapsulated microspheres and the early-strength, low-heat-of-hydration cement system of this invention are beneficial to ensuring the stability of deep-water hydrate layers or frozen soil hydrate layers during cementing, and avoiding cementing quality problems caused by hydrates during the cement hydration and setting process.

[0160] Cement slurry was prepared according to API 10B-2-2013 standard using the cement formulations of Examples 11 and Comparative Examples 4-6. The exothermic hydration of cement was tested using the direct method, and the exothermic hydration process was characterized using exothermic temperature curves. Figure 6 As shown.

[0161] According to the test results, the hydration exothermic temperature of Example 11 was significantly lower than that of Comparative Examples 4-6, while the hydration exothermic temperatures of Comparative Examples 4-6 were almost the same. This indicates that the present invention uses tetradecane, pentadecane, and paraffin in a certain proportion, and the mixed alkanes have a better heat absorption effect than using only two or one type of alkanes. However, the hydration exothermic temperature of Example 11 is still higher than that of Examples 5-8, indicating that the alkane ratio of phase change encapsulated microsphere 4 is not within the preferred range, and the heat absorption effect is slightly worse than that of phase change encapsulated microspheres 1-3.

[0162] Test Example 3

[0163] Strength performance evaluation.

[0164] Cement slurry was prepared according to API 10B-2-2013 standard for the cement formulations of Examples 5-11 and Comparative Example 1. The density and compressive strength of the cement slurry were measured, and the test results are shown in Table 1.

[0165] Table 1

[0166]

[0167] As shown in Table 1, taking the 3-day compressive strength as an example, compared with Comparative Example 1 without PCMM, when the PCMM addition is less than 10% of the cement weight, the compressive strength of the cement paste is almost unaffected; when the addition is 20% of the cement weight, the compressive strength decreases but still reaches 6 MPa; when the addition is 30% of the cement weight, the compressive strength decreases further but still reaches 4.7 MPa. The early compressive strength of Examples 5-11 is not significantly different from the test results of Comparative Example 1, indicating that the addition of PCMM to the cement system of this application has little impact on the early strength of the cement and can meet the compressive strength requirements of marine cementing.

[0168] Test Example 4

[0169] Cement slurry was prepared according to API 10B-2-2013 standard using the cement formulations of Examples 9-10 and Comparative Examples 2-3. The exothermic reaction of cement hydration was tested using the direct method, and the hydration exothermic process was characterized using exothermic temperature curves. The test results are as follows: Figure 5 As shown.

[0170] Test results show that the hydration heat release of the early-strength, low-heat-of-hydration cement systems of Examples 9 and 10 is significantly less than that of the conventional aluminate cement of Comparative Example 2 and the conventional G-grade silicate cement of Comparative Example 3, indicating that the cement system of the present invention has a significant effect on reducing the heat of hydration. Furthermore, based on the time of the heat release peak, the cement system of Example 10 reaches strength earlier than that of Comparative Example 2 and Example 9, indicating that the addition of aluminate-silicate composite cement to the cement system of the present invention helps ensure rapid hydration and solidification of the cement in the hydrate layer, while reducing the impact of heat energy on hydrate decomposition, ensuring cementing quality, and avoiding cementing accidents caused by hydrate decomposition.

[0171] Test Example 5

[0172] Cement slurry was prepared according to API 10B-2-2013 standard using the cement formulations of Examples 9-10 and Comparative Examples 2-3. The density and compressive strength were tested, and the test results are shown in Table 2.

[0173] Table 2

[0174]

[0175] Test results show that the compressive strength of the early-strength low-heat hydration cement system of the present invention in Example 10 at low temperature is much higher than that of Grade G silicate cement in Comparative Example 3, and close to that of aluminate cement in Comparative Example 2 at low temperature. This indicates that the addition of aluminate-silicate composite cement to the cement system of the present invention has excellent low-temperature early-strength characteristics compared with conventional silicate cement.

[0176] In summary, the phase change encapsulated microspheres provided by this invention have good encapsulation effect and corrosion resistance. When added to cement systems, they can significantly reduce the heat of hydration. Furthermore, the early strength and low heat of hydration system of this invention also has high early strength, making it suitable for application in low-temperature cementing.

[0177] The above description is merely a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, based on the technical teachings provided by the present invention and as common knowledge in the field, other equivalent modifications and improvements can be made, and these should also be considered within the scope of protection of the present invention.

Claims

1. A phase change encapsulated microsphere, characterized by, The core carrier, the alkane material and the epoxy resin; the alkane material is distributed inside the core carrier, and the epoxy resin at least coats the surface of the core carrier; The alkane material includes tetradecane, pentadecane and paraffin wax; the mass ratio of tetradecane: pentadecane: paraffin wax in the alkane material is 4-6: 9-11: 24-26; the mass ratio of the core carrier: alkane material: epoxy resin is 4-5: 9-11: 2-3.

2. The phase change encapsulated microspheres of claim 1, wherein, The mass ratio of tetradecane: pentadecane: paraffin wax in the alkane material is 5: 10: 25; And / or, the mass ratio of the core carrier: alkane material: epoxy resin is 4.5: 10: 2.

5.

3. The phase change encapsulated microspheres of claim 1 or 2, wherein, The core carrier is a hollow microsphere, and the hollow microsphere includes a shell and an internal cavity formed by the shell, and the shell is a porous medium material.

4. The phase change encapsulated microspheres of claim 3, wherein, The shell is a high-strength polymer porous medium material with a compressive strength of ≥20MPa.

5. The phase change encapsulated microspheres of claim 4, wherein, The shell is an alkali-activated polymer porous medium material.

6. The phase change encapsulated microspheres of claim 1 or 2, wherein, The average particle size of the core carrier is 200-300μm; And / or, the average diameter of the internal cavity of the core carrier is 100-200μm.

7. The phase change encapsulated microspheres of claim 6, wherein, The average particle size of the core carrier is 240-260μm; And / or, the average diameter of the internal cavity of the core carrier is 140-160μm.

8. The phase change encapsulated microspheres of claim 7, wherein, The average particle size of the core carrier is 250μm; And / or, the average diameter of the internal cavity of the core carrier is 150μm.

9. The phase change encapsulated microspheres of claim 1 or 2, wherein, The phase change encapsulation microsphere includes nanoscale dispersed particles dispersed on the surface of the epoxy resin.

10. The phase change encapsulated microspheres of claim 9, wherein, The nanoscale dispersed particles are one or more of nanoscale silicon dioxide, nanoscale aluminum oxide and nanoscale calcium carbonate; And / or, the mass ratio of the core carrier: nanoscale dispersed particles is 4-5: 2-3.

11. The phase change encapsulated microspheres of claim 10, wherein, The mass ratio of the core carrier: nanoscale dispersed particles is 4.5: 2.

5.

12. The method of producing phase change encapsulated microspheres according to any one of claims 1 to 11, wherein The preparation steps include: (1) mixing tetradecane, pentadecane and paraffin wax to obtain an alkane material; (2) adsorbing the alkane material inside the core carrier; (3) coating the epoxy resin on the surface of the core carrier carrying the alkane material to obtain the phase change encapsulation microsphere.

13. An early-strength, low-hydraulic-heat cement system characterized by, The phase change encapsulation microsphere according to any one of claims 1-11.

14. The early-strength, low-hydraulic-heat cement system of claim 13, wherein, The content of the phase change encapsulation microsphere is 5-30 parts by weight based on 100 parts by weight of cement.

15. The early-strength, low-hydraulic-heat cement system of claim 14, wherein, The content of the phase change encapsulation microsphere is 5-25 parts by weight based on 100 parts by weight of cement.

16. The early-strength, low-hydraulic-heat cement system of any one of claims 13-15, wherein, The components include, by weight fraction: Cement 100 parts; Phase change encapsulation microsphere 5-30 parts; Density reduction material 10-20 parts; Fluid loss additive 1-2 parts; Early strength agent 0.05-0.3 parts; Water 54-62 parts.

17. The early-strength, low-hydraulic-heat cement system of claim 16, wherein, The cement is aluminate-silicate composite cement; And / or, the early strength agent is an organic Mannich base early strength agent.

18. The early-strength, low-hydraulic-heat cement system of claim 17, wherein, The aluminate-silicate composite cement includes aluminate cement and silicate cement, and the mass ratio of the silicate cement to the aluminate cement is 2.5-3.5: 6.5-7.

5.

19. The early-strength, low-hydraulic-heat cement system of claim 18, wherein, The mass ratio of the silicate cement to the aluminate cement is 3:

7.

20. Use of the phase change encapsulated microspheres of any one of claims 1-11 to reduce the heat of hydration of cement.

21. Use of the cement system of any one of claims 13-19 in low temperature cementing.

22. The use according to claim 21, characterized in that, Use in low temperature cementing in marine deepwater hydrate zones and permafrost hydrate zones.

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