3d printing method of multilayer functional coated cores for extreme cementing environments

Abstract

The application discloses a 3D printing method of a multi-layer functional coating core suitable for well cementing extreme environment, and comprises the following steps: (1) selecting a natural core sample, performing layered scanning by using a three-dimensional white light scanner, processing the scanning data by using a reverse analysis software, and generating a three-dimensional model file; (2) setting a target core shape and size, reserving a groove for placing a micro sensor in the inside, proportionally dividing the core into an inner layer, a middle layer and an outer layer, and locating the groove in the inner layer, and completing the 3D model of the target core; (3) selecting printing materials for the inner layer, the middle layer and the outer layer; (4) transmitting the core 3D data to a 3D printer data processor, filling the printing materials of each layer in a layer-by-layer printing mode, setting suitable printing parameters according to different printing materials, and printing to form a complete core. The application has excellent stability and durability of the core in a high-temperature, high-pressure and corrosive environment downhole through material optimization and micro-pore structure design.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of artificial core preparation, and particularly relates to a 3D printing method for a multi-layer functional coating core suitable for an extreme environment of well cementing, which can have excellent stability and durability in a high-temperature, high-pressure and corrosive environment downhole. BACKGROUND

[0002] With the deepening of oil and gas well resource development, the temperature, pressure and acid-base conditions faced by oil and gas wells are increasingly severe. In order to improve the quality of well cementing and ensure construction safety, formation core sampling must be carried out to carry out performance evaluation of the well cementing interface and related fluid experiments. However, natural core sampling is costly and difficult, so artificial cores are usually used to replace natural cores for experiments.

[0003] Artificial cores play a key role in oil and gas well cementing operations, but the deficiencies in material performance and processing technology of the existing technology limit its performance in extreme environments, making it difficult to meet the needs of harsh conditions such as high temperature, high pressure and strong acid and alkali. "Method for preparing artificial core based on 3D printing technology and artificial core finished product" (CN109253910A) uses 3D printing technology to prepare core finished products, and then carries out core flow experiment testing; "Rock core preparation device and method based on photocuring 3D printing technology" (CN115464883A) prepares a multifunctional artificial core based on photocuring 3D printing technology; "Method for simulating different levels of high-permeability strip cores in reservoirs by 3D printing" (CN114428001A) first obtains the internal structure of the formation core using CT scanning technology, and then prints the core layer by layer using 3D printing technology. However, these technical solutions mainly focus on the reconstruction of the structure of the core, and fail to fully address the problem of the tolerance performance of the material and the processing details.

[0004] In view of the insufficient tolerance of existing 3D printed cores in extreme environments, it is particularly necessary to develop artificial cores that are suitable for extreme working environments, which not only can further optimize the drilling fluid system and improve the overall quality of well cementing operations, but also have great significance for the effective exploitation and protection of oil and gas resources. SUMMARY

[0005] The purpose of the present application is to provide a 3D printing method for a multi-layer functional coating core suitable for an extreme environment of well cementing, which has reliable principles and is easy to operate. Through material optimization and micro-pore structure design, the core can remain stable in a high-temperature, high-pressure and corrosive environment, and can be used for cementing interface cementing strength and flushing experiments to further evaluate the cementing performance of the cement slurry and the formation interface during well cementing. At the same time, the core can monitor external environmental parameters in real time, and has a broad market application prospect.

[0006] In order to achieve the above technical purposes, the following technical solutions are adopted.

[0007] The application selects high-temperature-resistant, corrosion-resistant and high-strength materials, combines special micropore design and corrosion-resistant and wear-resistant coating, and uses 3D printing technology to manufacture a core meeting actual needs. The core has excellent stability and durability in a high-temperature, high-pressure and corrosive environment, and an embedded sensor system can monitor external environmental parameters in real time, thereby further improving the accuracy of experimental data.

[0008] The 3D printing method of the multi-layer functional coating core suitable for the extreme environment of well cementation comprises the following steps in sequence:

[0009] (1) Select a natural core sample, determine the printing area of the structural surface thereof, use a three-dimensional white light scanner to perform layered scanning on the natural core sample, obtain data of the natural structure surface, process the scanned data by using a reverse analysis software, optimize the surface grid density and edge details, and generate a high-precision three-dimensional model file;

[0010] (2) Open the three-dimensional model file generated in step (1) in a CAD software, set the shape and size of the target core, retain the external geometric shape, remove unnecessary structural data in the interior, and at the same time, reserve a groove for placing a micro sensor in the interior of the core, divide the target core into three areas of an inner layer, a middle layer and an outer layer in a proportional manner, and the groove is located in the inner layer, thereby completing the 3D model of the target core;

[0011] (3) Select the printing materials of the inner layer, the middle layer and the outer layer, the inner layer is a core layer, the printing materials include but are not limited to high-conductive materials such as copper, copper alloy, aluminum nitride, graphite and polyvinylidene fluoride, the middle layer is functional, the printing materials include but are not limited to high-strength and high-temperature-resistant materials such as carbon fiber reinforced nylon, glass-filled nylon and polyether ether ketone, and the outer layer is a protective layer, the printing materials include but are not limited to high-corrosion-resistant and wear-resistant materials such as silicon nitride, silicon carbide, polytetrafluoroethylene and nickel-based alloy;

[0012] (4) Transmit the 3D data of the target core to a data processor of a 3D printer, adopt a layer-by-layer printing manner, fill the printing materials of each layer in sequence, and set suitable printing parameters according to different printing materials, first print the inner layer area of the target core, pause when printing reaches the reserved groove position, embed a micro sensor, then print the middle layer area, and finally complete the printing of the outer layer area to form a complete core.

[0013] Further, in step (2), the target core can be in the shape of a cuboid, a cube or a cylinder. For a cuboid or a cube, the length, width and height can range from 15-200mm, 15-200mm and 15-300mm respectively. For a cylindrical core, the diameter can range from 15-200mm and the height can range from 15-300mm. These dimensions are chosen based on the requirements of different experimental conditions and can be adapted to various experimental environments.

[0014] Further, in step (2), the size of the groove is 7mm x 7mm x 4mm, which is suitable for embedding a standard micro sensor to ensure that the groove can safely accommodate the sensor and maintain its functional integrity.

[0015] Further, in step (4), the surface of the material needs to be treated accordingly to ensure the firm bonding and structural stability between the inner and middle layers, and between the middle and outer layers of the target core.

[0016] Further, the treatment of the surface of the material refers to selecting the appropriate adhesive for the bonding needs of different materials. For the bonding area between metal materials and polymers, epoxy resin or polyurethane adhesive is selected, which has excellent bonding strength and chemical stability, suitable for maintaining long-term bonding force in high temperature and high pressure environments. For the bonding area between polymer and ceramic material or graphite, high-temperature epoxy resin or silicone adhesive is selected to ensure the stability and durability of the bonding in high-temperature environments.

[0017] Further, in the bonding area between metal materials and polymers, the roughness of the metal material surface is increased through mechanical polishing and sandblasting process, thereby enhancing the adhesion of the adhesive.

[0018] Further, in step (4), the micro sensor is NOVOSENSE NSPAS3 micro sensor, which can detect changes in temperature and pressure of the external environment, and its small design is suitable for embedding in the 3D printed core while maintaining stability and accuracy under high temperature and high pressure.

[0019] Further, in step (4), layer-by-layer printing means that the printing material for the inner layer of the core is first added to the material guide port of the 3D printer, and the printing parameters are set. After the inner layer is printed, the inner layer printing material is removed and replaced with the middle layer printing material. The printing parameters are re-set according to the characteristics of the middle layer material, and the middle layer area is printed. After the middle layer is printed, the material is replaced and the printing parameters are adjusted to finally complete the printing of the outer layer area.

[0020] Further, in step (4), the printing parameters are set as follows:

[0021] Laser power: ranging from 10W to 200W, depending on the material's absorption rate and melting point, to ensure uniform melting and reduce material loss.

[0022] Scan speed: the speed of the laser beam moving on the powder bed ranges from 1000mm / s to 7000mm / s. Lower speed is suitable for fine printing of complex structures, while higher speed is used for rapid manufacturing of larger parts.

[0023] Scan spacing: ranging from 0.1mm to 0.5mm, the adjustment of the spacing determines the fineness and surface finish of the printed layers.

[0024] Layer thickness: the thickness of the powder layer ranges from 0.05mm to 0.2mm, thinner layer thickness provides higher printing resolution, suitable for fine structures, while thicker layer is suitable for parts that require high strength and do not require high resolution.

[0025] Bed temperature: the temperature of the printing bed ranges from 80℃ to 200℃, close to the glass transition temperature of the material, reducing the generation of warping and internal stress.

[0026] Ambient temperature: the temperature of the printing environment is set to 60℃-200℃, maintaining a stable temperature can reduce the accumulation of thermal stress and avoid deformation of the part.

[0027] Further, in step (4), after the complete core is formed, the outer surface of the core needs to be treated according to the specific application requirements. When used in a strong acid or strong alkali environment, a layer of epoxy resin paint is sprayed on the outer surface of the core to improve its corrosion resistance. When used in a high-friction or high-flow liquid environment, a layer of polytetrafluoroethylene paint is sprayed on the outer surface of the core to extend the service life of the core and reduce wear.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] (1) The artificial core prepared by the present application has excellent mechanical properties and chemical stability, so that it can be used for various experimental operations in complex and extreme working environments, ensuring that the core can maintain structural integrity and performance consistency under harsh conditions such as high temperature, high pressure, strong acid and strong alkali;

[0030] (2) The artificial core prepared by the present application has a highly free internal structure design, which can truly simulate the porosity and internal network structure of actual underground oil reservoir rocks, making experimental data more close to actual working conditions, and providing a reliable experimental basis for subsequent oil reservoir analysis;

[0031] (3) The sensor system provided by the artificial core can not only monitor environmental changes in real time, but also provide accurate data feedback according to fluctuations in the external environment, greatly improving the real-time and accuracy of the experimental process.

[0032] (4) Through the surface treatment of the material interface, the selection of the adhesive, the heat treatment and the interface design, the application effectively solves the bonding problem between different levels of materials, ensures the structural stability and functional integrity of the core under extreme environment, and greatly improves the long-term use performance of the core under high temperature and high pressure conditions;

[0033] (5) The artificial core preparation process does not need to use soluble support material, reduces the subsequent processing steps, shortens the overall processing time by about 30%, also reduces the complexity of manual operation, and improves the production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 Flow chart of the method for printing a multi-layer functional coating core.

[0035] Figure 2 Schematic diagram of the structure of the printed core.

[0036] Figure 3 Cross-sectional view of the printed core.

[0037] Figure 4 Enlarged view of the bonding between the outer layer and the middle layer region.

[0038] Figure 5 Enlarged view of the bonding between the middle layer and the inner layer region.

[0039] In the figure: 1 - inner layer region of the core; 2 - middle layer region of the core; 3 - outer layer region of the core; 4 - micro wireless sensor; 5 - bonding between the inner and middle layers; 6 - bonding between the middle and outer layers. DETAILED DESCRIPTION

[0040] In order to help those skilled in the art better understand the present application, the embodiments of the present application are further described in conjunction with the drawings. It should be noted that the present application is not limited to the specific embodiments described, and various changes and modifications made by those of ordinary skill in the art without departing from the spirit and scope of the present application shall still be within the scope of protection of the present application.

[0041] Reference Figure 1 , Figure 2 , Figure 3 The core prepared by the method of the present application comprises:

[0042] The inner layer region 1 of the core has high conductivity and sensing function, mainly used for real-time data acquisition and internal temperature management, to ensure that the temperature change under extreme environment can be accurately fed back;

[0043] Core middle layer area 2: with high strength, high temperature resistance, and good structural integrity, providing overall structural support while maintaining excellent thermal performance, capable of handling physical stress in high temperature environments;

[0044] Core outer layer area 3: with excellent corrosion resistance, wear resistance, and protection function, effectively protecting the internal structure from external physical impact and chemical corrosion, prolonging the service life of the core;

[0045] Miniature wireless sensor 4: used to sense changes in pressure and temperature in the external environment and transmit data to external devices through a wireless transmission system, ensuring real-time monitoring of environmental parameters;

[0046] Inner and middle layer bonding 5: through reasonable bonding treatment, ensuring the firm bonding between the inner and middle layer materials, guaranteeing the stability and reliability of the overall structure;

[0047] Middle and outer layer bonding 6: using advanced bonding technology to enhance the bonding force between the middle and outer layer materials, improving the durability of the materials in extreme environments and the integrity of the overall structure.

[0048] I. Preparation of multi-layer functional coated core suitable for extreme environment of cementing

[0049] Example 1

[0050] (1) Core model construction: First, slice the natural rock sample and use a three-dimensional white light scanner to scan it layer by layer to obtain detailed data of the natural structure surface. Then process the scanning data through reverse analysis software to generate an accurate three-dimensional model file. Open the model file in CAD software, set the core shape to a cylindrical shape with a diameter of 60mm and a height of 100mm, and design the inner, middle, and outer three layers. At the same time, reserve a 7mm x 7mm x 4mm groove for embedding the miniature wireless sensor later. Finally, save the model file in STL format for subsequent printing.

[0051] (2) Inner layer printing (copper alloy): Add copper alloy powder to the material guide port of the SLS 3D printer and start setting the printing parameters. The printing parameters are set as follows:

[0052] Laser power: 100-120W

[0053] Scanning speed: 1500-2000mm / s

[0054] Layer thickness: 50-100μm

[0055] Scanning interval: 0.1-0.2mm

[0056] Substrate temperature: 150-200℃

[0057] Laser focus: aligned to the surface of the material or slightly off the surface

[0058] During the inner layer printing process, when printing to the reserved sensor groove, pause the printing, manually place the micro wireless sensor, continue printing until the inner layer printing is completed, and cool for 30 minutes.

[0059] (3) Middle layer printing (carbon fiber reinforced polyether ether ketone, PEEK): The inner layer core surface is treated with epoxy resin spraying to improve the adhesion of the material. Then replace the carbon fiber reinforced polyether ether ketone (PEEK) powder, start the middle layer printing, and the parameters are set as follows:

[0060] Laser power: 60-80W

[0061] Scanning speed: 2000-2500mm / s

[0062] Layer thickness: 50-100μm

[0063] Scanning interval: 0.1-0.2mm

[0064] Substrate temperature: 200-250℃

[0065] Laser focus: aligned to the surface of the material

[0066] After the middle layer printing is completed, cool for 20 minutes, and spray the surface with epoxy resin adhesive to increase the adhesion with the outer layer.

[0067] (4) Outer layer printing (nickel-based alloy Inconel 718): Replace the nickel-based alloy (Inconel 718) powder, and set the outer layer printing parameters as follows:

[0068] Laser power: 80-100W

[0069] Scanning speed: 2500-3000mm / s

[0070] Layer thickness: 50-100μm

[0071] Scanning interval: 0.1-0.15mm

[0072] Substrate temperature: 100-150℃

[0073] Laser focus: aligned to the surface of the material

[0074] After the outer layer printing is completed, cool for 1 hour. Use a soft brush to remove the unsintered powder on the surface of the core, then spray a layer of polytetrafluoroethylene coating on the outer layer surface to enhance the wear resistance and service life of the core, and finally obtain the required core sample.

[0075] Example 1 is a high thermal conductivity, high strength, corrosion resistant combination. The inner layer of the core uses a copper alloy, which has excellent electrical and thermal conductivity, suitable for high heat flow environments; the middle layer material is PEEK (polyether ether ketone), which has high strength and high temperature resistance to ensure the stability of the structure; the outer layer is a nickel-based alloy (Inconel 718), which provides excellent corrosion resistance and high temperature resistance.

[0076] Example 2

[0077] (1) Core model construction: After slicing the natural rock sample, use a three-dimensional white light scanner to scan it layer by layer to obtain detailed data of the natural structure. Then process the scanning data through reverse analysis software to generate accurate three-dimensional model data files. Use CAD software to open the model file, set the core shape to a cube of 100mm x 100mm x 150mm, and design the inner, middle and outer layers. A 7mm x 7mm x 4mm groove is reserved in the core for embedding a miniature wireless sensor. Finally, save the data in STL file format for subsequent printing operations.

[0078] (2) Inner layer printing (aluminum nitride): First, pour aluminum nitride powder into the material guide of the 3D printer and set the printing parameters. The specific parameters are as follows:

[0079] Laser power: 100-120W

[0080] Scan speed: 1500-2000mm / s

[0081] Layer thickness: 50-100pm

[0082] Scan spacing: 0.1-0.15mm

[0083] Substrate temperature: 150-200°C

[0084] Laser focal length: aligned with the material surface or slightly offset from the surface

[0085] When printing to the reserved sensor groove, pause the printing and manually place the miniature wireless sensor. Continue printing the inner layer area until the inner layer printing is complete and cool for 20 minutes.

[0086] (3) Middle layer printing (carbon fiber reinforced nylon, CF-Nylon): Spray silicone adhesive on the inner layer surface to enhance the adhesion between the middle layer and the inner layer. Then replace the carbon fiber reinforced nylon (CF-Nylon) powder and set the middle layer printing parameters as follows:

[0087] Laser power: 50-70W

[0088] Scan speed: 2500-3000mm / s

[0089] Layer thickness: 50-100 pm

[0090] Scan spacing: 0.1-0.2 mm

[0091] Substrate temperature: 80-120 °C

[0092] Laser focal length: aligned to the material surface

[0093] After the middle layer printing is completed, cool for 10 minutes, and spray polyurethane adhesive on the middle layer surface to improve the adhesion with the outer layer.

[0094] (4) Outer layer printing (stainless steel 316L): change to stainless steel (316L) powder, start printing the outer layer area, with the following printing parameters:

[0095] Laser power: 80-100 W

[0096] Scan speed: 2000-2500 mm / s

[0097] Layer thickness: 50-80 pm

[0098] Scan spacing: 0.1-0.15 mm

[0099] Substrate temperature: 100-150 °C

[0100] Laser focal length: aligned to the material surface or slightly offset from the surface

[0101] After the outer layer printing is completed, cool for 1 hour. Use a brush to gently remove the unsintered powder on the surface of the core, and then spray a layer of epoxy resin coating on the outer layer surface to enhance the acid and alkali resistance of the core. Finally, the required core sample is obtained.

[0102] Example 2 is a combination of high temperature resistance, structural stability, and strong protection. The inner layer of the core uses aluminum nitride, which has high thermal conductivity and high temperature resistance, making it perform well in extreme environments. The middle layer uses carbon fiber reinforced nylon, which has both strength and toughness, and can cope with high pressure environments. The outer layer uses stainless steel (316L) to provide better structural strength and corrosion resistance.

[0103] Example 3

[0104] (1) Core model construction: First, slice the natural rock sample and use a three-dimensional white light scanner to scan it layer by layer to obtain data on the natural structure. Then, process the scanning data using reverse analysis software to generate a three-dimensional model file. Open the model file using CAD drawing software, design the core as a cylindrical structure with a diameter of 140 mm and a height of 200 mm, and partition the inner, middle, and outer layers. Reserve a 7 mm x 7 mm x 4 mm groove in the core for embedding a miniature wireless sensor. Finally, save the file in STL format for subsequent printing.

[0105] (2) Inner layer printing (graphite): Pour graphite powder into the material guide of the 3D printer and start setting the printing parameters. The specific parameters are as follows:

[0106] Laser power: 60-80 W

[0107] Scan speed: 2500-3000 mm / s

[0108] Layer thickness: 50-100 μm

[0109] Scan spacing: 0.1-0.2 mm

[0110] Substrate temperature: 80-100 °C

[0111] Laser focal length: aligned with the material surface or slightly offset from the surface

[0112] When printing reaches the sensor groove position, pause the printing and manually embed the miniature sensor. After installation, continue printing until the inner layer area is complete and cool for 10 minutes.

[0113] (3) Middle layer printing (glass-filled nylon): Spray a layer of high-temperature epoxy resin adhesive on the inner layer surface to ensure firm bonding between the middle layer and the inner layer. Replace the glass-filled nylon powder and set the printing parameters for the middle layer area as follows:

[0114] Laser power: 50-70 W

[0115] Scan speed: 2500-3000 mm / s

[0116] Layer thickness: 50-100 μm

[0117] Scan spacing: 0.1-0.2 mm

[0118] Substrate temperature: 80-120 °C

[0119] Laser focal length: aligned with the material surface

[0120] Print the middle layer area, cool for 10 minutes after completion, and spray silicone adhesive on its surface to ensure adhesion between the middle layer and the outer layer.

[0121] (4) Outer layer printing (silicon carbide, SiC): replace with silicon carbide powder, start printing the outer layer area, the parameter settings are as follows:

[0122] Laser power: 100-120W

[0123] Scanning speed: 1500-2000mm / s

[0124] Layer thickness: 50-80μm

[0125] Scanning interval: 0.1-0.15mm

[0126] Substrate temperature: 150-200℃

[0127] Laser focal length: aligned with the material surface or slightly offset from the surface

[0128] After printing is completed, the core is cooled for 2 hours. Use a brush to gently remove the unsintered powder on the surface of the core, and finally obtain a core that meets the requirements.

[0129] Example 3 is an electrically insulating, lightweight high-strength, wear-resistant combination. The inner layer of the core is graphite, which has excellent electrical insulation and high temperature stability; the middle layer material is selected from glass-filled nylon to achieve lightweight and high strength; the outer layer is silicon carbide (SiC), which has high hardness and wear resistance and is suitable for high friction environment.

[0130] II. Performance test of the multi-layer functional coating core suitable for extreme environment of cementing

[0131] The performance test data of the artificial core prepared by Examples 1, 2 and 3 are as follows:

[0132]

[0133] As can be seen from the table, the core prepared by the present application can completely be suitable for core flow experiment and cementing interface performance evaluation experiment under extreme conditions of cementing.

[0134] III. Cementing interface performance evaluation of the multi-layer functional coating core

[0135] Flushing experiment: the flushing experiment is a key step to verify the effect of drilling fluid and flushing fluid on the cementing interface cementation during cementing. The multi-coating structure core prepared by the present application simulates the flushing effect during cementing, detects the effect of flushing fluid on the cementing strength of the interface of cement slurry, especially in acidic environment, to ensure the safety and long-term stability of cementing operation.

[0136] The cementing strength of the second interface is measured in the cementing operation, and the cementing strength of the second interface prepared by the multilayer 3D printing core is measured in the high-temperature and high-pressure environment to simulate the bonding performance between the cement slurry and the formation interface, and the interface strength change data of the cementing system under different working conditions are provided to improve the cementing quality.

[0137] The drilling fluid, cement slurry, water-based flushing fluid, acid flushing fluid (3% HCl solution), and strong alkaline flushing fluid (3% NaOH solution) of a certain oil and gas well in southwest China are selected for core flushing experiments and cementing strength experiments, and the process is as follows:

[0138] The core is weighed as m0, and the core is placed in a high-temperature and high-pressure fluid loss instrument at 3MPa and 90℃ for 30min, and the core with attached drilling fluid is taken out and weighed as m1; the core with attached drilling fluid is flushed with different types of flushing fluid at a speed of 300r / min for 15min, and the mass of the core with attached drilling fluid after flushing is weighed as m2, and the flushing efficiency η is calculated:

[0139] η=(m1-m2) / (m1-m0)

[0140] The flushed core is placed in a cementing mold, and a certain amount of cement slurry is poured between the core and the mold, and then placed in a 90℃ water bath for 1d and 3d, and then taken out to obtain the cementing strength S:

[0141] S=P / (πD h)

[0142] In the formula, S is the cementing strength, MPa; P is the loading pressure when the core is separated, N; D is the diameter of the core, mm; and h is the height of the cement ring, mm.

[0143] The test results are shown in Tables 1-4.

[0144] Table 1 Core flushing efficiency test results of the core prepared in Example 1

[0145]

[0146] Table 2 Core flushing efficiency test results of the core prepared in Example 2

[0147]

[0148] Table 3 Core flushing efficiency test results of the core prepared in Example 3

[0149]

[0150] Table 4 Cementing strength test results of the core prepared in Examples 1, 2 and 3

[0151]

[0152] From the table, it can be seen that the multi-layer functional coating core prepared by the application has similar flushing efficiency and cementing strength to the experimental data measured by using the field core.

[0153] In summary, the multi-layer functional coating core based on 3D printing can completely simulate the actual downhole conditions, and the experimental data is accurate and reliable. Through the evaluation of the interfacial change during the cementing process, a more perfect data basis for the formation of related theories can be provided, and a scientific basis for the smooth progress of the later production operation and cementing operation can also be provided.

Claims

1. A 3D printing method of multi-layer functional coating core suitable for extreme environment of cementing, comprising the following steps in sequence: (1) selecting a natural core sample, determining the printing area of its structural plane, using a three-dimensional white light scanner to perform layered scanning, obtaining data of the natural structural plane, processing the scanned data through reverse analysis software, and generating a three-dimensional model file; (2) opening the three-dimensional model file generated in step (1) in CAD software, setting the shape and size of the target core, reserving a groove for placing a micro sensor in the inside, dividing the target core into three regions of inner layer, middle layer and outer layer in equal proportion, and the groove is located in the inner layer, thereby completing the 3D model of the target core; (3) selecting the printing materials of the inner layer, middle layer and outer layer, the inner layer is the core layer, the printing material is copper, copper alloy, aluminum nitride, graphite or polyvinylidene fluoride, the middle layer is functional, the printing material is carbon fiber reinforced nylon, glass filled nylon or polyether ether ketone, and the outer layer is the protective layer, the printing material is silicon nitride, silicon carbide, polytetrafluoroethylene or nickel-based alloy; (4) transmitting the 3D data of the target core to the data processor of the 3D printer, filling the printing materials of each layer in sequence by using layer-by-layer printing, setting appropriate printing parameters according to different printing materials, printing the inner layer region of the target core first, pausing when printing to the reserved groove position, embedding the micro sensor, then printing the middle layer region, and finally completing the printing of the outer layer region to form a complete core.

2. The 3D printing method of multi-layer functional coated core suitable for well cementing extreme environment as claimed in claim 1, wherein, In step (2), the shape of the target core is a cuboid, a cube or a cylinder, for the cuboid or cube core, the size of length, width and height ranges from 15-200mm, 15-200mm and 15-300mm respectively; for the cylindrical core, the diameter is 15-200mm and the height is 15-300mm.

3. The 3D printing method of multi-layer functional coated core suitable for well cementing extreme environments as claimed in claim 1, wherein, In step (2), the size of the groove is 7mm×7mm×4mm for embedding a standard micro sensor.

4. The 3D printing method of multi-layer functional coated core suitable for well cementing extreme environment as claimed in claim 1 wherein, In step (4), in order to ensure the firm combination and structural stability between the inner layer and the middle layer, and between the middle layer and the outer layer of the target core, the surface of the material needs to be treated accordingly.

5. The 3D printing method of multi-layer functional coated core suitable for well cementing extreme environments as claimed in claim 4 wherein, The treatment of the surface of the material refers to selecting a corresponding adhesive according to the bonding requirements of different materials, for the bonding area between metal materials and polymers, selecting epoxy resin or polyurethane adhesive; for the bonding area between polymer and ceramic material or graphite, selecting high-temperature epoxy resin or silicone adhesive.

6. The 3D printing method of multi-layer functional coated core suitable for well cementing extreme environments as claimed in claim 5 wherein, In the bonding area between metal materials and polymers, the roughness of the surface of the metal material is increased by mechanical polishing and sand blasting process, thereby enhancing the adhesion of the adhesive.

7. The 3D printing method of multi-layer functional coated core suitable for well cementing extreme environments as claimed in claim 1 wherein, In step (4), layer-by-layer printing means that the printing material of the inner layer of the core is first added to the material guide port of the 3D printer, the printing parameters are set, the inner layer is printed, then the inner layer printing material is removed and replaced with the printing material of the middle layer, the printing parameters are re-set according to the characteristics of the middle layer material, the printing of the middle layer region is started, after the middle layer is printed, the material is replaced and the printing parameters are adjusted according to the same process, and finally the printing of the outer layer region is completed.

8. The 3D printing method of multi-layer functional coated core suitable for well cementing extreme environments as claimed in claim 1 wherein, In the step (4), after the complete core is formed, the outer surface of the core needs to be treated according to the specific application requirement of the core, and when the core is used in a strong acid or strong alkali environment, a layer of epoxy resin paint is sprayed on the outer surface of the core; when the core is used in a high-friction or high-flow liquid environment, a layer of polytetrafluoroethylene paint is sprayed on the outer surface of the core.

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