A method and device for reconstructing in-situ damage-stress field of disturbed coal rock in borehole drilling

Abstract

This invention provides a method and apparatus for in-situ reconstruction of the damage-stress field of disturbed coal and rock during borehole drilling. The method includes: constructing a sample model based on a coal and rock sample to be tested; the physical properties of the sample model are consistent with the physical properties of the coal and rock to be tested; performing mechanical tests on the coal and rock sample and the corresponding sample model to obtain the basic mechanical parameters of the coal and rock sample; sequentially drilling into each sample model and performing at least one stress freezing and digital photoelastic test to obtain the damage-stress field evolution process of the coal and rock to be tested during the drilling process; and sequentially drilling into each sample model to conduct a hydraulic fracturing test. This invention effectively elucidates the hydraulic fracturing mechanism of disturbed coal and rock, solving the problem of poor hydraulic fracturing effects in existing related technologies.

Description

Technical Field

[0001] This invention relates to the field of coal and rock detection technology, and in particular to a method and apparatus for in-situ reconstruction of coal and rock damage-stress field caused by borehole drilling disturbance. Background Technology

[0002] Although numerous researchers have conducted fundamental studies on hydraulic fracturing in coal and rock drilling, the main approach is to simulate the damage-stress state induced by drilling by first drilling and then applying in-situ stress, followed by hydraulic fracturing of the coal and rock. This is fundamentally different from actual engineering practice, because deep coal and rock are already under high in-situ stress. When simulating drilling, the approach should be to apply in-situ stress first and then drill.

[0003] There is currently no effective solution to the problem of poor hydraulic fracturing performance in existing related technologies. Summary of the Invention

[0004] This invention provides a method and apparatus for in-situ reconstruction of coal and rock damage-stress field during borehole drilling, which addresses the shortcomings of existing technologies such as poor hydraulic fracturing performance.

[0005] In a first aspect, the present invention provides a method for in-situ reconstruction of the coal and rock damage-stress field caused by borehole drilling, comprising:

[0006] A sample model is constructed based on the coal and rock sample to be tested; the physical properties of the sample model are consistent with the physical properties of the coal and rock sample to be tested.

[0007] Mechanical tests were performed on the coal rock sample to be tested and the corresponding sample model to obtain the basic mechanical parameters of the coal rock sample to be tested.

[0008] Each of the sample models was drilled sequentially, and at least one stress freeze and digital photoelastic test was performed to obtain the damage-stress field evolution process of the coal and rock under test during the drilling process.

[0009] Each of the sample models was drilled sequentially to conduct hydraulic fracturing tests, stress freezing, and digital photoelasticity tests to obtain the three-dimensional damage-stress field evolution process of the coal and rock under test during the hydraulic fracturing process.

[0010] According to the present invention, a method for in-situ reconstruction of coal and rock damage-stress field caused by borehole drilling is provided, wherein obtaining the coal and rock sample to be tested includes:

[0011] The sample structure of the coal and rock specimen is determined; the sample structure includes cubic, cylindrical, and Brazilian disc types.

[0012] According to the sample structure, the coal and rock to be tested are prepared into several coal and rock samples, and the coal and rock samples are screened.

[0013] According to the present invention, a method for in-situ reconstruction of coal and rock damage-stress field caused by borehole drilling is provided, which constructs a sample model based on the coal and rock sample to be tested, including:

[0014] The coal and rock samples to be tested are digitally reconstructed to establish a three-dimensional digital core model of the coal and rock samples to be tested.

[0015] The sample model is generated by printing a three-dimensional digital core model of the coal and rock to be tested.

[0016] According to the present invention, the in-situ reconstruction method of coal and rock damage-stress field caused by drilling is provided, wherein the model matrix of the sample model is made of VeroClear material, the model particles of the sample model are made of RGD525 material, and the model pores and model cracks of the sample model are made of Fullcure705 support material.

[0017] According to the present invention, a method for in-situ reconstruction of coal and rock damage-stress field during borehole drilling disturbance is provided. Mechanical tests are performed on the coal and rock sample to be tested and the corresponding sample model to obtain the basic mechanical parameters of the coal and rock sample to be tested, including:

[0018] Observational experiments were conducted on the coal and rock samples to be tested and the corresponding sample models to determine the microstructure and mineral composition characteristics of the coal and rock samples to be tested.

[0019] A uniaxial compression test was conducted on the cylindrical coal and rock sample, and the average value of the test results was taken to determine the basic mechanical parameters of the cylindrical coal and rock sample.

[0020] The Brazilian disc-shaped coal and rock samples were subjected to Brazilian splitting tests, and the average value of the test results was taken to determine the basic mechanical parameters of the Brazilian disc-shaped coal and rock samples.

[0021] The basic mechanical parameters include the compressive strength, tensile strength, elastic modulus, and Poisson's ratio of the coal and rock sample.

[0022] According to the present invention, a method for in-situ reconstruction of coal and rock damage-stress field during borehole drilling is provided, wherein borehole drilling is performed sequentially on each of the aforementioned sample models, and at least one stress freeze and digital photoelastic test is conducted, including:

[0023] Based on the sampling depth of the coal and rock to be tested, the stress state of the coal and rock to be tested is determined, and the corresponding stress state is applied to the sample model;

[0024] Determine the endpoint depth and several stress-freezing sections. When drilling into each stress-freezing section, stop drilling and perform a stress-freezing and digital photoelastic test until the endpoint depth is reached.

[0025] According to the present invention, a method for in-situ reconstruction of coal and rock damage-stress field during borehole drilling is provided, wherein each of the aforementioned sample models is sequentially subjected to borehole drilling, hydraulic fracturing tests, stress freezing, and digital photoelasticity tests, including:

[0026] Drilling is performed on each of the specimen models to obtain several drilled specimen models;

[0027] A water pressure stress freezing point is set, and water is injected into the borehole sample model according to the water pressure stress freezing point. Stress freezing and digital photoelasticity tests are then performed.

[0028] According to the present invention, a method for in-situ reconstruction of coal and rock damage-stress field during borehole drilling is provided, wherein the stress freezing includes:

[0029] A preset load is applied to the specimen model and kept constant;

[0030] The ambient temperature of the sample model was then lowered at a piecewise gradient rate until the target temperature was reached, after which it was cooled at a constant rate.

[0031] According to the present invention, a method for in-situ reconstruction of coal and rock damage-stress field during borehole drilling is provided, wherein the digital photoelastic test includes:

[0032] The specimen model after stress freezing is sliced ​​to obtain model slices;

[0033] The model slices are subjected to pulsed laser processing, and an arithmetic fringe pattern is captured.

[0034] The differential stress at the crack tip and surrounding area of ​​the specimen model is determined based on the differential fringe pattern.

[0035] Secondly, the present invention also provides an in-situ reconstruction device for coal and rock damage-stress field caused by borehole drilling, comprising:

[0036] A construction module is used to construct a sample model based on the coal and rock sample to be tested; the physical properties of the sample model are consistent with the physical properties of the coal and rock sample to be tested.

[0037] The testing module is used to perform mechanical tests on the coal and rock samples to be tested and the corresponding sample models, and to obtain the basic mechanical parameters of the coal and rock samples to be tested.

[0038] The first processing module is used to sequentially drill holes in each of the sample models and perform at least one stress freezing and digital photoelastic test to obtain the damage-stress field evolution process of the coal and rock under test during the drilling process.

[0039] The second processing module is used to sequentially drill holes for each of the sample models, conduct hydraulic fracturing tests, and perform stress freezing and digital photoelastic tests to obtain the three-dimensional damage-stress field evolution process of the coal and rock under test during the hydraulic fracturing process.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. The in-situ reconstruction method of coal and rock damage-stress field during drilling provided by the present invention, by adopting the process of loading before drilling, can realistically reproduce the damage-stress distribution of coal and rock around the hole during drilling under deep in-situ geostress conditions. It can effectively explore the hydraulic fracturing mechanism of disturbed coal and rock and solve the problem of poor hydraulic fracturing effect in existing related technologies.

[0042] 2. This invention provides an in-situ three-dimensional reconstruction method for the damage-stress field of hydraulic fracturing of coal and rock disturbed by deep drilling, which combines CT scanning and 3D printing technology. The matrix part uses the transparent printing material VeroClear, the particle part uses the non-transparent white material RGD525, and the pore and fracture parts use the support material Fullcure705 to prepare a model consistent with the structural characteristics of natural coal and rock. The mechanical properties are then tested. This method improves the authenticity and effectiveness of the test results.

[0043] 3. The present invention provides a method for in-situ three-dimensional reconstruction of the damage-stress field of hydraulic fracturing of coal and rock in deep boreholes with a target temperature set at 125 ℃ and then reduced to room temperature at a constant rate after reaching the target temperature at a segmented gradient rate. This method can reduce disturbances during the borehole drilling process. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0045] Figure 1 This is a flowchart of the in-situ reconstruction method for coal and rock damage-stress field during borehole drilling provided by the present invention;

[0046] Figure 2 This is a schematic diagram of the process of obtaining the damage-stress evolution during the drilling of coal and rock boreholes in an embodiment of the present invention;

[0047] Figure 3 This is a schematic diagram of the stress-freezing section setting in an embodiment of the present invention;

[0048] Figure 4 This is a schematic diagram of the process of obtaining the three-dimensional damage-stress field evolution during the hydraulic fracturing of coal and rock in an embodiment of the present invention;

[0049] Figure 5 This is a schematic diagram of the water pressure-time curve of the sample model in an embodiment of the present invention;

[0050] Figure 6 This is a schematic diagram of the temperature-time curve for stress freezing in an embodiment of the present invention;

[0051] Figure 7 This is a structural block diagram of the in-situ reconstruction device for coal and rock damage-stress field during drilling provided by the present invention. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0053] This invention provides a method for in-situ reconstruction of the coal and rock damage-stress field caused by borehole drilling. Figure 1 This is a flowchart of the in-situ reconstruction method for coal and rock damage-stress field during borehole drilling provided by the present invention, as shown below. Figure 1 As shown, the method includes the following steps:

[0054] Step S101: Construct a sample model based on the coal and rock sample to be tested; the physical properties of the sample model are consistent with the physical properties of the coal and rock to be tested.

[0055] Step S102: Perform mechanical tests on the coal and rock samples to be tested and the corresponding sample models to obtain the basic mechanical parameters of the coal and rock samples to be tested.

[0056] Step S103: Drilling is carried out on each sample model in sequence, and at least one stress freezing and digital photoelastic test is performed to obtain the damage-stress field evolution process of the coal and rock under test during the drilling process.

[0057] Step S104: Drilling is carried out on each sample model in sequence to conduct hydraulic fracturing tests, stress freezing and digital photoelasticity tests are performed to obtain the three-dimensional damage-stress field evolution process of the coal and rock under test during the hydraulic fracturing process.

[0058] In this method, firstly, a sample model is constructed based on the coal and rock sample to be tested. It is worth noting that, to more realistically represent the structure and parameters of the coal and rock, the physical properties of the sample model are consistent with those of the coal and rock, making the final test results more realistic and effective. Then, mechanical tests are performed on each sample model and coal and rock sample to determine their basic mechanical parameters for subsequent experiments and tests. Next, each sample model is drilled, and stress freezing and digital photoelasticity tests are conducted, combined with hydraulic fracturing tests, to obtain the damage-stress field evolution process of the coal and rock during drilling and the three-dimensional damage-stress field evolution process during hydraulic fracturing. This method adopts a loading-before-drilling process, realistically reproducing the damage-stress distribution of the coal and rock around the borehole under deep in-situ geostress conditions during drilling. This can effectively elucidate the hydraulic fracturing mechanism of disturbed coal and rock, solving the problem of poor hydraulic fracturing effects in existing related technologies. In the above process, the order of steps S103 and S104 can be adjusted as needed.

[0059] In some embodiments, obtaining coal and rock samples for testing includes: determining the sample structure of the coal and rock sample; the sample structure includes cubic, cylindrical and Brazilian disc types; preparing several coal and rock samples according to the sample structure, and screening the coal and rock samples.

[0060] For example, a field survey was conducted on the coal seam to collect relevant engineering test data and samples of the coal and rock to be tested. Using the collected large pieces of coal and rock, several samples of three different sizes were processed: cubic coal and rock samples with an edge length of 100 mm, cylindrical coal and rock samples with a diameter of 50 mm and a height of 100 mm, and Brazilian disc-shaped coal and rock samples with a diameter of 50 mm and a thickness of 25 mm. The coal and rock samples were selected by combining macroscopic surface observation and ultrasonic testing to control experimental errors.

[0061] In some embodiments, step S101, constructing a sample model based on the coal sample to be tested, includes: digitally reconstructing the coal sample to be tested to establish a three-dimensional digital core model of the coal sample to be tested; and printing based on the three-dimensional digital core model of the coal sample to be tested to generate a sample model.

[0062] Based on this, the model matrix of the sample model is made of VeroClear material, the model particles of the sample model are made of RGD525 material, and the model pores and cracks of the sample model are supported by Fullcure705 material.

[0063] For example, an industrial CT scanner with a scanning accuracy of 0.5 μm was used to scan and test the processed cubic coal and rock samples, obtaining 250 CT slices. These slices were imported into AVIZO software, and after noise reduction and segmentation processes, a three-dimensional digital core model of the coal and rock was established. An STL format file representing the three-dimensional structure was then exported. Three different sizes of sample models were prepared using a high-precision layered multi-material stereolithography system, such as the Object Connex 500 3D printer: a cubic sample with an edge length of 100 mm, a cylindrical sample with a diameter of 50 mm and a height of 100 mm, and several Brazilian disc samples with a diameter of 50 mm and a thickness of 25 mm. The model matrix used the transparent printing material VeroClear, the model particles used the opaque white material RGD525, and the pores and fractures used the support material Fullcure 705, thus giving the sample models physical and mechanical properties similar to the actual coal and rock samples.

[0064] In some embodiments, step S102 involves performing mechanical tests on the coal sample and corresponding sample model to obtain the basic mechanical parameters of the coal sample. This includes: conducting observational tests on the coal sample and corresponding sample model to determine the microstructure and mineral composition characteristics of the coal; performing uniaxial compression tests on cylindrical coal samples and averaging the test results to determine the basic mechanical parameters of the cylindrical coal sample; and performing Brazilian splitting tests on Brazilian disc-shaped coal samples and averaging the test results to determine the basic mechanical parameters of the Brazilian disc-shaped coal sample. The basic mechanical parameters include the compressive strength, tensile strength, elastic modulus, and Poisson's ratio of the coal sample.

[0065] For example, scanning electron microscopy was used to observe coal and rock samples and their corresponding sample models, and X-ray diffraction analysis was conducted to analyze their microstructure and mineral composition characteristics. Cylindrical and Brazilian disk-shaped coal and rock samples were subjected to uniaxial compression and Brazilian splitting tests respectively on a triaxial servo multi-field coupled rock testing system. In both tests, loads were applied via vertical displacement, with the displacement rate controlled at 0.05 mm / min. Three or more samples were tested in each group of tests, and the average value was taken to obtain the basic mechanical parameters of the samples, such as compressive strength, tensile strength, elastic modulus, and Poisson's ratio.

[0066] In some embodiments, step S103 involves sequentially drilling into each sample model and performing at least one stress freezing and digital photoelastic test, including: determining the stress state of the coal and rock to be tested based on the sampling depth of the coal and rock to be tested, and applying the corresponding stress state to the sample model; determining the endpoint depth and several stress freezing sections; stopping drilling and performing one stress freezing and digital photoelastic test when drilling into each stress freezing section, until the endpoint depth is reached.

[0067] For example, Figure 2 This is a schematic flowchart illustrating the damage-stress evolution process during coal and rock drilling in an embodiment of the present invention, as shown below. Figure 2 As shown, firstly, based on the sampling depth of the coal and rock sample, the stress state of the coal and rock to be tested is calculated and obtained, and this stress state is applied to a cubic coal and rock model on the testing machine. Subsequently, drilling is carried out using an 8 mm diameter auger bit, while simultaneously collecting its rotational speed and drill bit displacement. The drilling pressure is set to 100 N, and the drilling depth is set to 70 mm. Four stress-freezing sections are set at equal intervals from this depth as the endpoint. Figure 3 As shown, Figure 3 This is a schematic diagram of the stress-freezing section setup in an embodiment of the present invention. In the figure, 11 represents the stress state, 12 represents the auger drill bit, 13 represents the cubic sample model, and 14 represents the stress-freezing section. Drilling is stopped whenever a stress-freezing section is reached, and a stress-freezing and digital photoelastic test are performed. After this stress-freezing and digital photoelastic test, drilling resumes, and this cycle continues until the final depth is reached, at which point drilling ceases. This process yields the damage-stress evolution during coal and rock borehole drilling.

[0068] In some embodiments, step S104, which involves drilling holes in each sample model sequentially, conducting hydraulic fracturing tests, and performing stress freezing and digital photoelastic tests, includes: drilling holes in each sample model to obtain several drilled sample models; setting hydraulic stress freezing points; injecting water into the drilled sample models according to the hydraulic stress freezing points; and performing stress freezing and digital photoelastic tests.

[0069] For example, Figure 4 This is a schematic diagram illustrating the process of obtaining the three-dimensional damage-stress field evolution during hydraulic fracturing of coal and rock in an embodiment of the present invention, as shown below. Figure 4 As shown, drilling was carried out using an 8 mm diameter auger bit, with a drilling pressure set to 100 N and a drilling depth set to 70 mm. Several borehole sample models were prepared, and then a full-process hydraulic fracturing test was conducted on a true triaxial testing machine with a water injection rate set to 60 ml / min to obtain complete water pressure-time curves, as shown. Figure 5 As shown, Figure 5 This is a schematic diagram of the water pressure-time curve of the sample model in this embodiment of the invention. Based on this curve, four stress freezing points are set before the fracturing pressure, corresponding to water pressures of 20%, 40%, 60%, and 80% of the fracturing pressure, respectively. Subsequently, four more borehole sample models are selected, each corresponding to a different water pressure, and water is injected sequentially. When the water pressure reaches the corresponding value, the process stops, and stress freezing and digital photoelasticity testing are performed to obtain the three-dimensional damage-stress field evolution process during hydraulic fracturing of coal and rock.

[0070] Based on the above embodiments, stress freezing includes: applying a preset load to the specimen model and keeping it constant; and lowering the ambient temperature of the specimen model at a piecewise gradient rate until the target temperature is reached, and then cooling it at a constant rate.

[0071] For example, a cubic coal and rock model is placed on a true triaxial testing machine with a temperature chamber, a specified load is applied and kept constant, and then the target temperature of the temperature chamber is set to 125 ℃. After reaching the target temperature at a piecewise gradient rate, the temperature is lowered at a constant rate to reduce disturbance. Figure 6 As shown, Figure 6 This is a schematic diagram of the temperature-time curve for stress freezing in an embodiment of the present invention.

[0072] Based on this, the digital photoelastic test includes: slicing the specimen model after stress freezing to obtain model slices; processing the model slices with pulsed laser and capturing fringe patterns; and determining the fringe patterns of the crack tip and surrounding area of ​​the specimen model based on the fringe patterns.

[0073] For example, the polarization optical path used in digital photoelastic testing includes: a light source, a polarizer, a first quarter-wave plate, a temperature chamber, a mounting bracket, a second quarter-wave plate, an analytical mirror, and a high-speed camera. Specifically, the frozen sample model is cut into model slices with a thickness of 1.5 mm, and then the digital photoelastic test begins. At this time, the light source emits a pulsed laser with a half-width at half-maximum of 220 ns, which passes sequentially through the polarizer and the first quarter-wave plate, causing the sample model made of photosensitive material to exhibit birefringence under stress. After passing through the second quarter-wave plate, interference fringes are formed on the analytical mirror, and the high-speed camera captures the image to obtain an equal-arithmetic fringe pattern.

[0074] When the incident light is perpendicular to x - y When incident on a plane, in the stress components σ x , σ y and The photoelastic effect is generated. Based on the plane stress theory, by capturing images of equal differential fringes in a circularly polarized light field, analyzing the order of the differential fringes in the images, and substituting them into the stress-optics law formula of the three-dimensional photoelastic model, the magnitude of the equal differential stress at the crack tip and in the vicinity can be calculated. The stress-optics law formula of the three-dimensional photoelastic model is as follows:

[0075]

[0076] In the formula, σ1' and σ2' are the principal stresses in the plane perpendicular to the incident light, also known as the secondary principal stresses. f0' represents the stripe value of the material at the stress freezing temperature. t Indicates the thickness of the slice. m This indicates the grade of the gradation line at that point. This represents the normal stress in the x-direction. This represents the normal stress in the y-direction. This represents the shear stress on the plane.

[0077] The present invention also provides an in-situ reconstruction device for the damage and stress field of disturbed coal and rock during drilling. The following describes the in-situ reconstruction device for the damage and stress field of disturbed coal and rock during drilling provided by the present invention. The in-situ reconstruction device for the damage and stress field of disturbed coal and rock during drilling described below can be referred to in correspondence with the in-situ reconstruction method for the damage and stress field of disturbed coal and rock during drilling described above. Figure 7 This is a structural block diagram of the in-situ reconstruction device for coal and rock damage-stress field during borehole drilling provided by the present invention, as shown in the figure. Figure 7 As shown, the device includes:

[0078] Module 701 is used to construct a sample model based on the coal and rock sample to be tested; the physical properties of the sample model are consistent with the physical properties of the coal and rock sample to be tested.

[0079] Test module 702 is used to perform mechanical tests on the coal and rock samples to be tested and the corresponding sample models to obtain the basic mechanical parameters of the coal and rock samples to be tested.

[0080] The first processing module 703 is used to sequentially drill holes for each sample model and perform at least one stress freeze and digital photoelastic test to obtain the damage-stress field evolution process of the coal and rock under test during the drilling process.

[0081] The second processing module 704 is used to sequentially drill holes for each sample model, conduct hydraulic fracturing tests, and perform stress freezing and digital photoelastic tests to obtain the three-dimensional damage-stress field evolution process of the coal and rock under test during the hydraulic fracturing process.

[0082] In operation, this device first constructs a sample model based on the coal and rock sample to be tested, using the construction module 701. Notably, to more realistically represent the structure and parameters of the coal and rock, the physical properties of the sample model are consistent with those of the coal and rock, resulting in more accurate and effective test results. Next, the testing module 702 performs mechanical tests on each sample model and coal and rock sample to determine their basic mechanical parameters for subsequent experiments and tests. The first processing module 703 and the second processing module 704 then drill holes in each sample model, performing stress freezing and digital photoelasticity tests, combined with hydraulic fracturing experiments, to obtain the damage-stress field evolution process of the coal and rock during drilling and the three-dimensional damage-stress field evolution process during hydraulic fracturing. This device employs a pre-loading and post-drilling process, realistically reproducing the damage-stress distribution of the coal and rock around the borehole under deep in-situ geostress conditions. This effectively elucidates the hydraulic fracturing mechanism of disturbed coal and rock, solving the problem of poor hydraulic fracturing effects in existing related technologies.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for in-situ reconstruction of coal and rock damage-stress field caused by borehole drilling, characterized in that, include: Construct a sample model based on the coal and rock samples to be tested; The physical properties of the sample model are consistent with the physical properties of the coal and rock to be tested. Mechanical tests were performed on the coal rock sample to be tested and the corresponding sample model to obtain the basic mechanical parameters of the coal rock sample to be tested. Each of the sample models was drilled sequentially, and at least one stress freeze and digital photoelastic test was performed to obtain the damage-stress field evolution process of the coal and rock under test during the drilling process. Each of the sample models was drilled sequentially to conduct hydraulic fracturing tests, stress freezing, and digital photoelasticity tests to obtain the three-dimensional damage-stress field evolution process of the coal and rock under test during the hydraulic fracturing process. Obtaining the coal and rock samples to be tested includes: The sample structure of the coal and rock specimen is determined; the sample structure includes cubic, cylindrical, and Brazilian disc types. According to the sample structure, the coal and rock to be tested are prepared into several coal and rock samples, and the coal and rock samples are screened. Constructing a sample model based on the coal and rock samples to be tested includes: The coal and rock samples to be tested are digitally reconstructed to establish a three-dimensional digital core model of the coal and rock samples to be tested. The sample model is generated by printing a three-dimensional digital core model of the coal and rock to be tested. Each of the aforementioned specimen models was sequentially drilled, and at least one stress freeze and digital photoelastic test was performed, including: Based on the sampling depth of the coal and rock to be tested, the stress state of the coal and rock to be tested is determined, and the corresponding stress state is applied to the sample model; Determine the endpoint depth and several stress-freezing sections. When drilling into each stress-freezing section, stop drilling and perform a stress-freezing and digital photoelastic test until the endpoint depth is reached. Each of the aforementioned specimen models was sequentially subjected to drilling, hydraulic fracturing tests, stress freezing, and digital photoelasticity tests, including: Drilling is performed on each of the specimen models to obtain several drilled specimen models; A water pressure stress freezing point is set, and water is injected into the borehole sample model according to the water pressure stress freezing point. Stress freezing and digital photoelasticity tests are then performed.

2. The method for in-situ reconstruction of coal and rock damage-stress field during borehole drilling as described in claim 1, characterized in that, The matrix of the sample model is made of VeroClear material, the model particles of the sample model are made of RGD525 material, and the model pores and cracks of the sample model are supported by Fullcure705 material.

3. The in-situ reconstruction method for coal and rock damage-stress field caused by borehole drilling as described in claim 1, characterized in that, Mechanical tests were performed on the coal and rock samples to be tested and the corresponding sample models to obtain the basic mechanical parameters of the coal and rock samples to be tested, including: Observational experiments were conducted on the coal and rock samples to be tested and the corresponding sample models to determine the microstructure and mineral composition characteristics of the coal and rock samples to be tested. A uniaxial compression test was conducted on the cylindrical coal and rock sample, and the average value of the test results was taken to determine the basic mechanical parameters of the cylindrical coal and rock sample. The Brazilian disc-shaped coal and rock samples were subjected to Brazilian splitting tests, and the average value of the test results was taken to determine the basic mechanical parameters of the Brazilian disc-shaped coal and rock samples. The basic mechanical parameters include the compressive strength, tensile strength, elastic modulus, and Poisson's ratio of the coal and rock sample.

4. The method for in-situ reconstruction of coal and rock damage-stress field caused by borehole drilling as described in claim 1, characterized in that, The stress freezing includes: A preset load is applied to the specimen model and kept constant; The ambient temperature of the sample model was then lowered at a piecewise gradient rate until the target temperature was reached, after which it was cooled at a constant rate.

5. The method for in-situ reconstruction of coal and rock damage-stress field during borehole drilling disturbance according to claim 1, characterized in that, The digital photoelasticity test includes: The specimen model after stress freezing is sliced ​​to obtain model slices; The model slices are subjected to pulsed laser processing, and an arithmetic fringe pattern is captured. The differential stress at the crack tip and surrounding area of ​​the specimen model is determined based on the differential fringe pattern.

6. A device for in-situ reconstruction of coal and rock damage-stress field caused by borehole drilling, used to implement the method for in-situ reconstruction of coal and rock damage-stress field caused by borehole drilling as described in any one of claims 1-5, characterized in that, include: The construction module is used to construct a sample model based on the coal and rock sample to be tested; The physical properties of the sample model are consistent with the physical properties of the coal and rock to be tested. The testing module is used to perform mechanical tests on the coal and rock samples to be tested and the corresponding sample models, and to obtain the basic mechanical parameters of the coal and rock samples to be tested. The first processing module is used to sequentially drill holes in each of the sample models and perform at least one stress freezing and digital photoelastic test to obtain the damage-stress field evolution process of the coal and rock under test during the drilling process. The second processing module is used to sequentially drill holes for each of the sample models, conduct hydraulic fracturing tests, and perform stress freezing and digital photoelastic tests to obtain the three-dimensional damage-stress field evolution process of the coal and rock under test during the hydraulic fracturing process.

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