Rock core reconstruction method of 3D printing pore pouring matrix based on digital rock core

Abstract

The invention discloses a rock core reconstruction method of a 3D printing pore pouring matrix based on a digital rock core, and relates to the field of geotechnical engineering.The rock core reconstruction method comprises the following steps that S1, a high-resolution image of an original rock profile is scanned and collected, and pores, cracks and a matrix of the rock are recognized; s2, constructing a three-dimensional digital core model of which the pore and crack characteristics are consistent with those of the original rock; s3, a matrix with pores and cracks is subjected to 3D printing to complete rock core sample manufacturing; or a pore and crack model is printed through 3D, and the following steps are continued to pour the matrix; s4, testing mechanical properties of the protolith to obtain physical property parameters of the protolith; s5, a matrix material is poured on the printed pore and crack model and maintained, and a reconstructed rock core sample with physical property parameters similar to those of the original rock is obtained; s6, carrying out performance test on the reconstructed rock core sample; precise reconstruction of cracks and pore structures of the natural rock core is achieved, and the mechanical property is similar to that of the natural rock core.

Description

Technical Field

[0001] The present application relates to the field of geotechnical engineering technology, and in particular to a core reconstruction method of a 3D printed porous casting matrix based on a digital core. Background Art

[0002] In geotechnical engineering and underground engineering research, the preparation of rock samples is of great significance to the reliability and accuracy of experimental data. In order to study the mechanical and permeability properties of rocks, natural core samples are usually required. However, the acquisition cost of natural cores is high, and their physical properties are significantly discrete, which poses a challenge to the uniformity and comparability of experimental data. At the same time, in actual rock mechanics experiments, the fracture structure has an important influence on the mechanical properties and seepage characteristics of rocks, but the fracture morphology in natural cores varies, making it difficult to conduct precise control and repeatable experiments.

[0003] Existing rock sample preparation methods are often difficult to fully match the properties of natural rocks, and there are many problems as follows:

[0004] (1) Difficulty in obtaining natural cores and the problem of discreteness: Natural core samples are expensive to obtain and their physical properties are highly discrete, resulting in poor consistency and comparability of experimental data, affecting the reliability of experimental conclusions;

[0005] (2) The reproducibility of fracture structure is not high: the fracture morphology in natural cores is complex and uncontrollable, making it difficult to achieve accurate reproduction and multiple repetitive experiments, which limits the systematic study of the impact of fractures on rock mechanics and seepage characteristics;

[0006] (3) The uniformity of sample batch production is insufficient: In multiple groups of experiments, in order to ensure the comparability of data and the stability of conclusions, a large number of core samples with the same structure and physical properties need to be prepared, but traditional methods are difficult to ensure the uniformity of samples;

[0007] (4) Material property matching problem: The parameters such as Young’s modulus and Poisson’s ratio of the existing methods are difficult to fully match with the physical properties of natural rocks, resulting in the inability to accurately simulate the mechanical properties of real rock cores. Summary of the invention

[0008] In order to solve the above problems, the present application provides a core reconstruction method of a 3D printed porous casting matrix based on a digital core, which solves the problem of difficulty in obtaining natural core samples and strong discreteness, and provides a consistent and repeatable specimen for rock mechanics experiments, which is suitable for multiple comparative experiments. The technical solution is as follows:

[0009] The present application provides a core reconstruction method of a 3D printed porous casting matrix based on a digital core, comprising the following steps:

[0010] S1 scans to collect high-resolution images of the original rock profile and identify the pores, fractures and matrix of the rock;

[0011] S2 constructs a three-dimensional digital core model with pore and fracture characteristics consistent with the original rock;

[0012] S3 completes the core sample preparation by 3D printing a matrix with pores and fractures; or by 3D printing a pore and fracture model and continuing the following steps to cast the matrix;

[0013] S4 original rock mechanical property test to obtain original rock physical characteristic parameters;

[0014] S5 pours matrix material on the printed pore and fracture models and maintains them to obtain a reconstructed core sample with physical property parameters similar to those of the original rock;

[0015] S6 performs performance tests on the reconstructed core samples.

[0016] For example, in the core reconstruction method of the 3D printed porous casting matrix based on the digital core provided in one embodiment, in S1, scanning electron microscope SEM and computer tomography CT technology are used to collect high-resolution images of various sections of the original natural rock to reflect the distribution of pores, cracks and matrix inside the rock, which serves as basic data for constructing a three-dimensional digital core model.

[0017] For example, in the core reconstruction method of the 3D printed porous casting matrix based on the digital core provided in one embodiment, in S1, an algorithm is designed using image recognition technology to process the collected high-resolution image of the original rock profile, identify the pores, cracks and matrix of the rock, and generate a binary image.

[0018] For example, in the core reconstruction method of the 3D printing porous casting matrix based on digital core provided in one embodiment, in S2, the binary image is reconstructed into a three-dimensional digital core model with pores and cracks and the pore and crack characteristics are consistent with the original rock using three-dimensional digital core reconstruction software, which serves as the basis for subsequent 3D printing.

[0019] For example, in the core reconstruction method of the 3D printed porous casting matrix based on digital core provided in one embodiment, in S3, when printing the pore and fracture model, the three-dimensional digital core model is first inverted to generate a three-dimensional model of pores and fractures, and then printed.

[0020] For example, in the core reconstruction method of the 3D printed porous casting matrix based on digital core provided in one embodiment, in S4, a uniaxial or triaxial test is performed on the original rock under the original formation stress conditions to measure the Young's modulus and Poisson's ratio parameters of the original rock.

[0021] For example, in the core reconstruction method of the 3D printed porous casting matrix based on the digital core provided in one embodiment, in S5, cement is selected as the cast matrix material, and the cement ratio is adjusted to achieve a Young's modulus and Poisson's ratio similar to those of the original rock. After the casting is completed, the sample is cured until the matrix material is completely solidified to form a complete core structure.

[0022] For example, in the core reconstruction method of the 3D printed porous casting matrix based on the digital core provided in one embodiment, when it is necessary to perform seepage permeation and sealing test experiments, a degradable material is used to print the pore and crack model, and after the matrix is ​​solidified in S5, the degradable material in the cracks and pores is degraded and removed by chemical or physical treatment methods, the pore and crack structure is retained, and the integrity of the sample and the sealing of the cracks and pores are checked.

[0023] For example, in the core reconstruction method of the 3D printed porous casting matrix based on the digital core provided in one embodiment, in S6, the reconstructed core sample is placed on a rock mechanics experimental platform to conduct a mechanical experiment to simulate the mechanical behavior and seepage characteristics of the core under complex stress conditions underground.

[0024] The beneficial effects of a core reconstruction method of a 3D printed porous casting matrix based on a digital core provided in some embodiments of the present application are as follows: the present application solves the problem of difficulty in obtaining natural core samples and high discreteness through the combination of digital core models and 3D printing, and provides consistent and repeatable specimens for rock mechanics experiments, which are suitable for multiple comparative experiments. In addition, the algorithm designed in this application will reversely reconstruct the digital core model of the matrix into a digital core model of the fracture, and propose a core reconstruction method by 3D reverse printing fractures and pores and casting the rock matrix. On the one hand, it can save expensive 3D materials, and accurately print and control microstructures such as fractures and pores, meeting the experimental needs of fracture extension, seepage characteristics, sealing and other aspects in the fields of petroleum engineering and underground engineering; on the other hand, the reconstructed core sample with the same physical properties as the original rock, such as strength and Poisson's ratio, can be obtained through the composition ratio of the casting material, which is more in line with the actual working conditions; at the same time, multiple identical core samples can be reconstructed at the same time, and control tests can be carried out through the control variable method to reduce the large discreteness caused by the different internal structures of the original rock, and ensure the correlation between the experimental results and the variables; this application can not only be used for academic research, but also can be promoted and applied in the fields of oil and gas engineering, geological engineering, etc. to improve the accuracy and economy of the experiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 This is a flow chart of the core reconstruction method of the 3D printed porous casting matrix based on the digital core of the present application. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0028] Unless otherwise defined, the technical terms or scientific terms used in the present disclosure should be understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0029] Basalt contains a large amount of carbon-fixing minerals and has a very high potential for CO2 mineral storage. The CarbFix pilot demonstration project carried out in Iceland in recent years showed that by injecting 73 to 175 tons of CO2 mixed with water into basalt reservoirs, more than 95% of the CO2 can be converted into carbonate minerals within 2 years and permanently stored.

[0030] In view of this, the present application provides a core reconstruction method of 3D printed porous casting matrix based on digital cores to address the high investment cost of artificial cavitation in traditional underground oil and gas reservoirs, as well as the high risk of CO2 leakage and lack of economic benefits in traditional CO2 geological storage technology. The method for constructing a reservoir in the present application is based on mineral carbon fixation, has a low risk of carbon leakage and has good economic benefits, thereby achieving efficient and safe carbon fixation and low-cost underground reservoir construction, such as Figure 1 As shown, the following steps are included:

[0031] S1 scans to collect high-resolution images of the original rock profile and identify the pores, fractures and matrix of the rock;

[0032] Specifically, scanning electron microscope (SEM) and computer tomography (CT) technology are used to collect high-resolution images of each section of the original natural rock to accurately reflect the distribution of pores, cracks and matrix inside the rock, which serves as the basic data for constructing a three-dimensional digital core model;

[0033] S2 constructs a three-dimensional digital core model with pore and fracture characteristics consistent with the original rock;

[0034] Specifically, the collected high-resolution images of the original rock profile are processed using image recognition technology and related algorithms to identify the pores, cracks and matrix of the rock and generate binary images. The binary images are reconstructed into three-dimensional digital core models with pores and cracks and the pore and crack characteristics are consistent with the original rock using three-dimensional digital core reconstruction software such as JHNY-DPM, which serves as the basis for subsequent 3D printing to ensure the true restoration of the cracks.

[0035] In addition, the three-dimensional digital core model can be imported into the software to divide the mesh for numerical simulation and compared with the experimental results;

[0036] S3 When making small samples and samples with low strength requirements and 3D materials that can meet the rock properties, the matrix part is converted into a 3D printing file according to the three-dimensional digital core model, and the core sample is made by 3D printing the matrix with pores and cracks. It is more convenient to directly print the matrix model by 3D printing, and the cracks and voids are smaller, which is conducive to some experiments such as seepage. However, this method is more expensive and has limited mechanical properties such as strength and elastic modulus.

[0037] When making large samples and samples with high strength requirements and 3D materials cannot meet the rock properties, the 3D digital core model is first inverted to generate a 3D model of pores and fractures, and the pores and fractures are partially converted into 3D printing files. The pore and fracture models are printed by 3D printing, and the subsequent steps of casting the matrix are continued;

[0038] To ensure the microstructure of cracks and pores is fine, suitable 3D printing materials such as photosensitive resin and high-precision PLA are selected. If the sample is used for mechanical experiments such as uniaxial compression or triaxial compression, use softer materials to print the pore and crack models; if it is used for seepage experiments, use degradable materials to print the pore and crack models for subsequent removal;

[0039] On the one hand, the present application can directly leave pores and cracks to print the matrix; on the other hand, the pores and cracks can be printed and the matrix can be obtained by pouring other materials;

[0040] S4 original rock mechanical property test to obtain original rock physical characteristic parameters;

[0041] Specifically, the mechanical properties of the original rock are tested to obtain parameters such as Young's modulus and Poisson's ratio, which provide a basis for ensuring that the reconstructed core sample has similar mechanical properties to the original rock when pouring the matrix material.

[0042] S5 pours matrix material on the printed pore and fracture models and maintains them to obtain a reconstructed core sample with physical property parameters similar to those of the original rock;

[0043] Specifically, cement is selected as the matrix material for pouring, and the cement ratio is adjusted to achieve a Young's modulus and Poisson's ratio similar to that of the original rock. After pouring, the sample is cured until the matrix material is completely solidified to form a complete core structure.

[0044] When it is necessary to conduct seepage permeation and sealing test experiments, a pore and crack model is printed with a degradable material, and after the matrix is ​​solidified in S5, the degradable material in the cracks and pores is degraded and removed by a chemical or physical treatment method, and the pore and crack structure is retained to ensure that the pore and crack structure of the reconstructed core sample conforms to the physical form of the natural core. After removing the degradable material, the integrity of the sample and the sealing of the cracks and pores are checked to ensure the reliability of the experimental results;

[0045] When the seepage and sealing test experiments are not carried out, the 3D material strength of the pores and cracks is small and will not affect the strength of the entire sample. In mechanical experiments such as mechanics, the pore and crack models can be printed without degrading the material;

[0046] S6 performs performance tests on the reconstructed core samples;

[0047] Specifically, the reconstructed core samples are placed on a rock mechanics experimental platform to conduct a variety of mechanical experiments (such as uniaxial loading, triaxial loading, seepage experiments, hydraulic fracturing experiments, etc.) to simulate the mechanical behavior and seepage characteristics of the core under complex stress conditions underground. The permeability test can be carried out on the fractures according to the experimental requirements to verify the stability and permeability of the fracture structure.

[0048] In order to study the influence of different factors on the mechanical properties of rocks, the method of this application can be used to mass-produce core samples with the same structure and performance, and conduct multiple repetitive experiments. By controlling the variable method, the interference of the discreteness of the rock sample on the experimental results can be significantly reduced, and the reliability and accuracy of the experimental data can be improved. Through the above-mentioned implementation mode, the present application can not only realize the accurate reconstruction of the fracture and pore structure of natural cores, but also obtain mechanical properties similar to those of natural cores by adjusting the physical properties of the matrix material, providing a convenient, economical and repeatable sample preparation method for rock mechanics experiments.

[0049] Although the implementation scheme of the present application has been disclosed as above, it is not limited to the applications listed in the specification and implementation modes, and it can be fully applicable to various fields suitable for the present application. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present application is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A core reconstruction method for a 3D printed porous casting matrix based on a digital core, characterized in that: The following steps are involved: S1 scans to collect high-resolution images of the original rock profile and identify the pores, fractures and matrix of the rock; S2 constructs a three-dimensional digital core model with pore and fracture characteristics consistent with the original rock; S3 completes the core sample preparation by 3D printing a matrix with pores and fractures; or by 3D printing a pore and fracture model and continuing the following steps to cast the matrix; S4 original rock mechanical property test to obtain original rock physical characteristic parameters; S5 pours matrix material on the printed pore and fracture models and maintains them to obtain a reconstructed core sample with physical property parameters similar to those of the original rock; S6 performs performance tests on the reconstructed core samples.

2. The core reconstruction method of the 3D printed porous casting matrix based on the digital core according to claim 1, characterized in that: In S1, scanning electron microscope (SEM) and computer tomography (CT) technology are used to collect high-resolution images of each section of the original natural rock to reflect the distribution of pores, cracks and matrix inside the rock, which serve as basic data for constructing a three-dimensional digital core model.

3. The core reconstruction method of the 3D printed porous casting matrix based on the digital core according to claim 2, characterized in that: In S1, an algorithm is designed using image recognition technology to process the collected high-resolution image of the original rock profile, identify the pores, cracks and matrix of the rock, and generate a binary image.

4. The core reconstruction method of the 3D printed porous casting matrix based on the digital core according to claim 3, characterized in that: In S2, the binary image is reconstructed into a three-dimensional digital core model with pores and fractures using three-dimensional digital core reconstruction software, and the pore and fracture characteristics are consistent with the original rock, which serves as the basis for subsequent 3D printing.

5. The core reconstruction method of the 3D printed porous casting matrix based on the digital core according to claim 4, characterized in that: In S3, when printing the pore and fracture model, the three-dimensional digital core model is first inverted to generate a three-dimensional model of pores and fractures, and then printed.

6. The core reconstruction method of the 3D printed porous casting matrix based on the digital core according to claim 5, characterized in that: In S4, a uniaxial or triaxial test is performed on the original rock under the original formation stress condition to measure the Young's modulus and Poisson's ratio parameters of the original rock.

7. The core reconstruction method of the 3D printed porous casting matrix based on the digital core according to claim 6, characterized in that: In S5, cement is selected as the matrix material for pouring, and the cement ratio is adjusted to achieve a Young's modulus and Poisson's ratio similar to those of the original rock. After pouring, the sample is cured until the matrix material is completely solidified to form a complete core structure.

8. The core reconstruction method of the 3D printed porous casting matrix based on the digital core according to claim 7, characterized in that: When it is necessary to conduct seepage permeation and sealing test experiments, the pore and crack models are printed with degradable materials, and after the matrix is ​​solidified in S5, the degradable materials in the cracks and pores are degraded and removed by chemical or physical treatment methods, the pore and crack structure is retained, and the integrity of the sample and the sealing of the cracks and pores are checked.

9. The core reconstruction method of the 3D printed porous casting matrix based on the digital core according to claim 8, characterized in that: In S6, the reconstructed core sample is placed on a rock mechanics experimental platform to perform mechanical experiments to simulate the mechanical behavior and seepage characteristics of the core under complex stress conditions underground.

Images