Crack tracking and pressure feedback physical simulation test system and use method

Abstract

The invention provides a crack tracking and pressure feedback physical simulation test system and a test use method. The test system comprises a similar material model used for simulating rock mass in a mining area; a grating and an optical fiber which are used for collecting stress-strain signals are arranged in the horizontal hole, and the grating and the optical fiber are connected with a static stress-strain collector; the test bed is used for placing a similar material model; the hydraulic device is used for applying stress to the similar material model; the hydraulic device comprises a top hydraulic device and a lateral hydraulic device, the top hydraulic device is arranged at the top of the similar material model, and the lateral hydraulic device is arranged on the side face of the similar material model. According to the method, the expansion condition of cracks in the ore body fracturing process can be truly reflected, optimization design is conducted on the range from the in-situ position to the cracks of the ore body, the rock body cracking mode and the fluid pressure according to the test result, disturbance to surrounding rock is reduced to the maximum extent while the stoping efficiency is guaranteed, and safe and stable construction of a project is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of gas fracturing, and in particular to a crack tracking and pressure feedback physical simulation test system and a use method thereof. Background Art

[0002] In recent years, gas fracturing, as another new type of fracturing method without explosives and water, has become a new green, environmentally friendly and efficient way to break rock mass with its unique advantages in flow, transmission, and penetration. However, the existing test equipment and test methods mainly analyze whether the pressure value can fracture the rock mass, and cannot complete the test equipment to track cracking and pressure feedback.

[0003] Traditional mine fracturing monitoring mainly relies on fiber grating sensors, which are usually deployed at or near the location of high-pressure fluid or gas fracturing wells. They can only obtain single-point pressure data and are unable to conduct comprehensive monitoring of the entire process and entire area of ​​ore mining. In addition, it is difficult to monitor and track fracturing cracks in real time, and it is even more difficult to achieve real-time feedback on the fracturing status. There are limitations.

[0004] Patent CN202410016049.X discloses a real-time fracturing monitoring system based on fiber optic distributed sensing. The device receives and analyzes high-pressure fluid or gas feedback optical signals, senses and monitors the flow rate of the return fluid, monitors temperature and pressure parameters, and judges abnormal signals to monitor the pressure parameters in the deployment area. When there are abnormal signals, an alarm is issued, thereby controlling the pressure of the pressurization through the flow rate of the return fluid, thereby realizing the function of automatic control. However, the device does not yet involve crack tracking in the fracturing process, acoustic emission fracture signal monitoring and feedback devices, and post-processing methods for optimizing the in-situ crack range of the ore body, rock cracking mode and fluid pressure based on the monitoring results.

[0005] At present, the research on the mechanism of crack expansion during fracturing is still in its infancy. Especially in engineering fracturing operations, there is no complete theoretical system for the cracking direction and rupture range. It is necessary to provide guidance and data support for engineering based on indoor test data. By regulating the pressure value through the feedback information of injection pressure and rock fracture during indoor tests, it is possible to study the mechanism of rock fracturing induced by high-pressure fluids, and propose various countermeasures for on-site fracturing operations and optimize the fracturing effect. Summary of the invention

[0006] The present invention discloses a crack tracking and pressure feedback physical simulation test system and a method of use. By real-time monitoring of crack opening and expansion in the model and regulating the fracturing technology through the feedback system, the technical problem of accurately controlling the cracking range is solved. The constructed crack tracking and pressure feedback physical simulation test device can achieve scale upgrade from laboratory to field, and the crack extension position and rupture pressure value obtained from indoor similar material tests are combined with numerical analysis simulation results and applied to monitoring the on-site failure stress threshold and rupture risk area division. It provides services for scientific research mechanism and applied research.

[0007] The device of the present invention is as follows:

[0008] A crack tracking and pressure feedback physical simulation test system, comprising:

[0009] A similar material model for simulating the rock mass in the mining area; a simulated borehole is arranged inside the similar material model, the simulated borehole is a horizontal hole, a perforation cluster is connected around the horizontal hole, a sleeve is arranged inside the simulated borehole, a fracturing fluid delivery mechanism is connected to the upper part of the sleeve, and the fracturing fluid delivery mechanism is connected to a gas storage tank; a fiber grating sensor for collecting stress and strain signals is arranged in the horizontal hole, and the fiber grating sensor is connected to a static stress and strain collector; an acoustic emission sensor is arranged on the surface of the similar material model, and the acoustic emission sensor is used to monitor and collect fracture signals;

[0010] A test bench for placing models of similar materials;

[0011] A hydraulic device for applying stress to a similar material model; the hydraulic device comprises a top hydraulic device and a lateral hydraulic device, wherein the top hydraulic device is arranged on the top of the similar material model, and the lateral hydraulic device is arranged on the side of the similar material model.

[0012] The present invention also provides a crack tracking and pressure feedback physical simulation test method, which is implemented based on any one of the above crack tracking and pressure feedback physical simulation test systems and includes the following steps:

[0013] S1. Prepare a rock model of the mining area based on the geological conditions of the mining area, place the model on the stage of the test system, and attach fiber grating sensors and acoustic emission sensors to the model;

[0014] S2, starting the top hydraulic device and the lateral hydraulic device to apply pressure to the model to simulate the stress of the on-site geology;

[0015] S3, start the gas storage tank to inject liquid fracturing gas for pressurization, and transport the liquid gas to the perforation cluster in the capsule in the similar material model through the fracturing fluid transport mechanism. At this time, cracks are generated in the similar material model around the perforation cluster. After the cracks are fully developed, ceramics are added as proppants to prevent the cracks from closing, and fluorescent agents are added to track the cracks. After the loading is completed and the proppants fix the cracks, a complete image of the cracks is obtained by drilling camera;

[0016] S4, the fiber grating sensor attached to the surface of the model collects stress and strain signals, and the fracturing information is collected through the static stress and strain acquisition instrument connected to the fiber grating sensor; the fracturing information includes the tensile strength and uniaxial compression strength of the rock;

[0017] S5. The rupture signal of the model during the fracturing process is collected by an acoustic emission sensor installed on the surface of the model and sent to an acoustic emission instrument, so as to locate and track the rupture during the fracturing process of the model, and locate and monitor the rupture area in the model;

[0018] S6. Deriving damage variables based on the fracturing information monitored in the acoustic emission system, and establishing a rock damage model in a data processing terminal computer based on the damage variables.

[0019] Furthermore, S1 specifically includes the following steps:

[0020] According to the on-site geological conditions, the rock samples in the mining area are tested to obtain the mechanical parameters of the rock samples;

[0021] The mechanical parameters of the rock sample are set as the mechanical parameters of the similar material model, and the cementing material and aggregate of the similar material are selected based on the mechanical parameters of the similar material model;

[0022] Similar material models were prepared using similar materials of binder and aggregate.

[0023] Furthermore, the mechanical parameters include density, compressive strength, Poisson's ratio and elastic modulus.

[0024] Furthermore, the complete image of the crack is used to prepare a deep learning data set and train a model, and the specific steps are as follows:

[0025] In the complete image of the crack, multiple coils are used to locate the edge of the object and obtain a closed boundary. A labeled data set is made, and the data set is randomly divided into a training set and a validation set in a ratio of 8:2. The data set is put into the image segmentation neural network for training and validation to achieve image learning and segmentation.

[0026] The specific steps include:

[0027] Apply rock damage models to actual field work; deduce possible situations in actual fracturing operations based on complete fracture images and fracturing information, and conduct targeted optimization of fracturing operation design;

[0028] Based on the fracturing information, it is determined whether the rock has tensile or shear failure, where the tensile failure variable is F s , the shear failure variable is F t ;

[0029] F s =-σ3-f s0 (1)

[0030]

[0031] Among them, f s0 is the tensile strength of rock, f t0 is the uniaxial compressive strength of the rock, in MPa; σ1 and σ3 are the major and minor principal stresses of the rock, in MPa; the tensile direction is defined as negative;

[0032] The damage variable D of rock is defined by using tensile failure variable and shear failure variable:

[0033]

[0034] Among them, ε s0 is the maximum tensile strain of rock, ε t0 is the maximum compressive strain of rock, in MPa; ε1 and ε3 are the major and minor principal strains of rock, and D is the damage variable of rock;

[0035] Based on the elastic-plastic damage theory, a rock damage model is established:

[0036] E=(1-D)E0 (4)

[0037] Where, E is the real-time elastic modulus of rock, and E0 is the initial modulus of rock;

[0038] The statistical method of rock failure area in similar material model is as follows:

[0039] Import the tensile failure variables, shear failure variables, damage variables and rock damage modulus into the Comsol Multiphysics (version 5.4) numerical analysis program, define the tensile strength and uniaxial compression strength of the rock in the similar material model, input other rock parameters obtained from the indoor test into the Comsol Multiphysics (version 5.4) numerical analysis program, calculate the plastic deformation and failure curve of the similar material model, and obtain the damage factor D;

[0040] The rock area with damage factor D greater than 0 is defined as the destruction area, and the area with damage factor D equal to 0 is defined as the non-destructive safety area;

[0041] The obtained damage factor D is applied to actual field work, and the rock damage area is reflected by updating the rock elastic modulus in real time.

[0042] Compared with the prior art, the present invention has the following advantages:

[0043] The present invention can truly reflect the relationship between crack expansion and injected gas pressure in hard rock during gas pressure fracturing, and can simulate the fracturing phenomenon of hard and brittle rock in engineering fields such as pillar recovery under high stress environment, oil and gas injection and production in areas prone to casing damage, and tunnel excavation under complex geological conditions. The actual fracturing operation can be optimized according to the test results, and the disturbance to the surrounding rock can be minimized while ensuring safe excavation, so as to ensure the safe and stable progress of the project. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0045] Figure 1 This is a diagram of the test system of the present invention.

[0046] Figure 2 for Figure 1 AA section left view.

[0047] Figure 3 for Figure 1 BB section top view.

[0048] Figure 4 This is a main view test diagram of the test bench of the present invention.

[0049] Figure 5 2 is a similar material model diagram of an embodiment of the present invention.

[0050] In the figure: 1. Similar material model; 2. Test bench; 3. Top hydraulic device; 4. Lateral hydraulic device; 5. Horizontal hole; 6. Fiber Bragg grating sensor; 7. Double-sided partition; 8. Encapsulation capsule; 9. Perforation cluster; 10. Acoustic emission sensor; 11. Gas storage tank; 12. Fracturing fluid delivery mechanism; 13. Acoustic emission instrument; 14. Data processing terminal computer; 15. Counterweight; 16. Carrying platform; 17. Ground surface. DETAILED DESCRIPTION

[0051] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0052] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0054] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, the numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0055] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention: the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0056] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below their position devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0057] The present invention develops an indoor physical simulation test system for crack tracking and pressure feedback control in the process of fluid pressure fracturing of hard and brittle rock mass. The system includes a strain sensor, a stress sensor and a computer with a built-in simulation program.

[0058] Firstly, a similar material model was prepared according to similarity theory, and fiber Bragg grating sensors were arranged in the flow pressure fracturing area of ​​the similar material model. Then, a similar material test bench was used to carry out boundary loading including the top and sides. Thirdly, proppant was added to fix the gas diffusion path after fracturing, and fluorescent agent was added to track the cracks. Finally, after the loading was completed, the strain and damage of the overall test model were observed, and the crack morphology was observed by drilling camera.

[0059] A crack tracking and pressure feedback physical simulation test system, such as Figure 1-4 As shown, including:

[0060] A similar material model 1 is used to simulate the rock mass in the mining area; a simulated borehole is arranged inside the similar material model 1, and the simulated borehole is a horizontal hole 5; the double-sided partitions 7 installed on both sides of the similar material model contain an encapsulation capsule 8 in the middle, and the horizontal hole 5 inside the encapsulation capsule 8 is connected with a perforation cluster 9 around it, and a lateral fracturing delivery device is connected to one end of the horizontal hole 5, and a sleeve is arranged in the simulated borehole, and a fracturing fluid delivery mechanism 12 is connected to the upper part of the sleeve, and the fracturing fluid delivery mechanism 12 is connected to a gas storage tank 11; a fiber grating sensor 6 for collecting stress and strain signals is arranged in the horizontal hole 5, and the fiber grating sensor 6 is connected to a static stress and strain collector; the acoustic emission sensors 10 are evenly arranged on the surface of the similar material model, and the acoustic emission sensors 10 are connected to an acoustic emission instrument 13.

[0061] In the perforation cluster 9, perforation refers to gas or liquid at a certain pressure in the oil layer or gas layer, so that radial holes of a certain depth are formed inside the formation, so that the oil and gas in the formation or oil and gas layer can be collected to the ground through the oil pipe or casing. Cluster refers to a group of interconnected perforating guns. These perforating guns are connected together in series or parallel to facilitate multiple perforation operations in the same well section to increase production capacity. Here, the "perforation cluster" is the rows of perforations around the horizontal well for inputting fracturing fluid.

[0062] A test bench 2 for placing a similar material model 1, with counterweights 15 placed on both sides of the test bench;

[0063] The model is placed on the loading platform 16 of the test bench 2, and the test bench 2 is placed on the horizontal surface 17, and a hydraulic device is used to apply stress to the similar material model; the hydraulic device includes a top hydraulic device 3 and a lateral hydraulic device 4, the top hydraulic device 3 is arranged on the top of the similar material model 1, and the lateral hydraulic device 4 is arranged on the side of the similar material model 1.

[0064] The present invention also provides a crack tracking and pressure feedback physical simulation test method, which is implemented based on a crack tracking and pressure feedback physical simulation test system. Figure 2 As shown, the following steps are included:

[0065] S1. According to the on-site geological conditions, the rock samples of the mining area are tested to obtain the mechanical parameters of the rock samples, such as density, compressive strength, Poisson's ratio and elastic modulus. According to the three similar theorems in the similarity principle, the mechanical parameters of the similar material model are set to select the binder and aggregate of the similar material. Common binders include gypsum, cement, rosin, paraffin, lime and water glass. Common aggregates include sand, mica, iron powder, clay, sawdust and barite powder. According to the mechanical properties of the target rock sample, one or more similar material models are selected to prepare. Generally, a variety of model samples are obtained through different proportions. Mechanical tests are carried out on the samples to test the mechanical parameters. Finally, the final proportion of similar materials is determined in the samples with multiple proportions. On the similar material test bench, the similar material model of hard and brittle rock is prepared through the steps of pre-setting mold holes, filling, curing and demolding. In the process of casting the model, horizontal holes and perforation clusters are reserved by pre-embedded molds.

[0066] S2. Simulate the actual wellbore setting method, arrange fiber grating sensors in the horizontal hole to collect stress and strain signals, and collect fracturing information through the connected static stress and strain collector. Determine the fracturing area according to the on-site engineering conditions; start the top hydraulic device and the lateral hydraulic device to apply pressure to the similar material model to simulate the stress of the on-site geology;

[0067] S3, start the gas tank to inject liquid fracturing gas for pressurization, and deliver the liquid gas to the perforation cluster through the fracturing fluid delivery mechanism. At this time, cracks are generated in the similar material model around the perforation cluster. The cracks are generated by the perforation cluster delivering liquid fracturing to the similar material model. Fracturing occurs near the perforation cluster of the similar material model to form cracks. After the cracks are fully developed, ceramics are added as proppants to prevent the cracks from closing, and fluorescent agents are added to track the cracks. After the loading is completed and the proppants fix the cracks, a complete image of the cracks is obtained by drilling photography;

[0068] S4, the fiber Bragg grating sensor collects stress and strain signals, and collects fracturing information through a static stress and strain acquisition instrument connected to the fiber Bragg grating sensor; the fracturing information includes rock tensile strength and uniaxial compression strength;

[0069] S5. Positioning and tracking of ruptures in the fracturing process of similar material models. The rupture signals of the models during the fracturing process are collected by the acoustic emission sensors installed on the surface of the models and sent to the acoustic emission instrument to position and monitor the rupture areas in the models.

[0070] S6. deriving damage variables based on the fracturing information monitored in the acoustic emission system, and establishing a rock damage model in a data processing terminal computer based on the damage variables;

[0071] S7. Apply rock damage models to actual field work;

[0072] S8. Based on the complete image of the fracture and the fracturing information, the possible situations in the actual fracturing operation are deduced, and the fracturing operation design is optimized in a targeted manner.

[0073] S5 and S6 specifically include: combining the tensile criterion and Mohr-Coulomb's law to determine whether the rock has tensile or shear failure, wherein the tensile failure variable and the shear failure variable can be expressed as: F s and F t ;

[0074] F s =-σ3-f s0 (1)

[0075]

[0076] Among them, f s0 is the tensile strength of rock (“rock” in the similar material model), f t0 is the uniaxial compressive strength of rock, in MPa; σ1 and σ3 are the major and minor principal stresses of rock, in MPa; the tensile direction is defined as negative.

[0077] The damage variable D of rock is defined by using tensile failure variable and shear failure variable:

[0078]

[0079] In the formula, ε s0 is the maximum tensile strain of rock, ε t0 is the maximum compressive strain of rock, in MPa; ε1 and ε3 are the major and minor principal strains of rock, and D is the damage variable of rock.

[0080] Based on the elastic-plastic damage theory, a rock damage model is established:

[0081] E=(1-D)E0 (4)

[0082] Where E is the real-time elastic modulus of rock, and E0 is the initial modulus of rock.

[0083] The statistical method of the rock damage area in the similar material model is as follows: first, write formulas 1, 2, 3, and 4 into the large-scale finite element software COMSOL numerical analysis program, define the tensile strength and uniaxial compression strength of the "rock" in the similar material model, and input other rock parameters obtained from indoor tests, such as the internal friction angle, into the COMSOL numerical analysis program, calculate the plastic deformation and failure curve of the similar material model, and obtain the damage factor D. Define the rock area with a damage factor D greater than 0 as the damage zone, and the area with a damage factor D equal to 0 as the non-destructive safety area. Apply the obtained damage factor D to actual on-site work, and reflect the rock damage area by updating the rock elastic modulus in real time.

[0084] The main purpose of similar material testing is to deduce the possible situations in actual projects through the strain of the model, and to optimize and adjust the project accordingly. Through the above four steps, the strain and cracking of the similar material model after loading can be obtained, and the actual cracking conditions that may occur in the project can be deduced. Based on this, the fracturing design can be adjusted and optimized to find the balance between safety and economy, control the deformation range as much as possible, and ensure fracturing under safe conditions.

[0085] Example

[0086] Experiment on the relationship between gas fracturing pressure and crack expansion during the column recovery process in an underground metal mine:

[0087] 1) Based on the actual geological parameters of the inter-plate column and combined with the similarity theorem, a similar material model of the inter-plate column rock mass of the ore body is prepared.

[0088] ① According to the hardness and brittleness characteristics and mechanical parameters of the inter-column rock of an underground metal mine, see Table 1, cement is used as the main material of similar materials to carry out physical simulation tests;

[0089] Table 1 Physical and mechanical parameters of rock mass

[0090]

[0091]

[0092] ② According to the geometric dimensions of the test bench (loading area) (2.4m*1.2m*0.2m) and the structural parameters of the panel area, the geometric similarity ratio C of this test is L =200, bulk density similarity ratio Cγ=2, stress similarity ratio C σ =C L ·C γ =400, the dimensionless similarity ratio is 1 (strain ratio, Poisson's ratio, friction angle ratio), that is, Cε=Cμ=Cφ=1. At the same time, the size of the model, similar test materials and the field prototype are kept geometrically similar, and the initial and boundary conditions are similar. See Appendix Figure 5 .

[0093] ③ On the premise of satisfying the similarity ratio, design the ratio of similar materials and use mechanical tests to determine their mechanical parameters.

[0094] 2) After the similar material model is prepared, the similar material model is placed on the test bench (specific location), and stress, strain, and acoustic emission sensors are installed near the fracturing drilling area on the model.

[0095] 3) Start the hydraulic device on the top and the lateral hydraulic device of the test bench to apply pressure to the prepared similar material model to simulate the stress conditions of the on-site geology of the inter-column column of the mine plate. After loading for 6 hours, when the internal stress field of the similar material is stable, start the subsequent test.

[0096] 4) According to the design plan for panel mining, each stope is mined one by one in the order of mining one by one, and cementation and tailings filling are carried out until the entire panel is mined. The model test is then left stationary for 6 hours to allow the internal stress field of similar materials to rebalance.

[0097] 5) According to the design plan for recovering the plate pillars, fluid fracturing boreholes are arranged, and liquid fracturing gas is injected through the gas tank. After the cracks are fully developed, proppants and fluorescent agents are added to track the crack rupture. After the loading is completed and the proppant fixes the cracks, the complete image of the cracks is obtained by drilling camera, and the model's initiation pressure and the expansion range of microcracks are determined by acoustic emission monitoring equipment, and the plate stress is obtained by the fiber grating stress monitoring system.

[0098] 6) Collect fracturing information of similar material models through fiber Bragg grating stress and strain acquisition instruments and acoustic emission instruments, including parameters such as rock tensile strength, uniaxial compression strength, acoustic emission ring counts and energy release values, as well as fracturing images.

[0099] 7) Based on the obtained similar material model fracturing information, combined with the similar material model damage variables and similarity theory calculated through numerical analysis, the field rock damage model of the mine plate interval column is established;

[0100] 8) Based on the complete fracture image and fracturing information obtained in steps 4 to 6, the possible situations of the columnar rock mass in the mine plate interval during the actual fracturing operation are deduced. The actual mining work on site is guided according to the actual fracturing feedback mechanism obtained; and the fracturing operation design is optimized in a targeted manner.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, ordinary experimenters in the field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A crack tracking and pressure feedback physical simulation test system, characterized in that: include: A similar material model for simulating the rock mass in the mining area; a simulated borehole is arranged inside the similar material model, the simulated borehole is a horizontal hole, a perforation cluster is connected around the horizontal hole, a sleeve is arranged inside the simulated borehole, a fracturing fluid delivery mechanism is connected to the upper part of the sleeve, and the fracturing fluid delivery mechanism is connected to a gas storage tank; a fiber grating sensor for collecting stress and strain signals is arranged in the horizontal hole, and the fiber grating sensor is connected to a static stress and strain acquisition instrument; an acoustic emission sensor for monitoring the model rupture signal is placed on the surface of the similar material model; a bidirectional partition placed on the front and rear sides of the model and an encapsulation capsule in the middle of the bidirectional partition are used to encapsulate the similar material model; A test bench for placing models of similar materials; A hydraulic device for applying stress to the model; the hydraulic device comprises a top hydraulic device and a lateral hydraulic device, the top hydraulic device is arranged on the top of the similar material model, and the lateral hydraulic device is arranged on the side of the similar material model.

2. A crack tracking and pressure feedback physical simulation test method, implemented based on the crack tracking and pressure feedback physical simulation test system described in claim 1, characterized in that: The steps include: S1. Prepare a rock model of the mining area based on the geological conditions of the mining area, place the model on the stage of the test system, and attach fiber grating sensors and acoustic emission sensors to the model; S2, starting the top hydraulic device and the side hydraulic device to apply the intended set pressure to the model; S3, start the gas storage tank to inject liquid fracturing gas for pressurization, and transport the liquid gas to the perforation clusters in the capsule in the similar material model through the fracturing fluid transport mechanism. At this time, cracks are generated in the model around the perforation clusters. After the cracks are fully developed, ceramics are added as proppants to prevent the cracks from closing, and fluorescent agents are added to track the cracks. After the loading is completed and the proppants fix the cracks, a complete image of the cracks is obtained by drilling camera; S4, the fiber Bragg grating sensor attached to the surface of the model collects stress and strain signals, and the fracturing information is collected through the static stress and strain acquisition instrument connected to the fiber Bragg grating sensor; the fracturing information includes the tensile strength and uniaxial compression strength of the rock; S5. The rupture signal of the model during the fracturing process is collected by an acoustic emission sensor installed on the surface of the model and sent to the acoustic emission instrument, so as to locate and track the rupture during the fracturing process of the model, and locate and monitor the rupture area in the model; S6. Deriving damage variables based on the fracturing information monitored in the acoustic emission system, and establishing a rock damage model in a data processing terminal computer based on the damage variables.

3. The crack tracking and pressure feedback physical simulation test method according to claim 1, characterized in that: S1 specifically includes the following steps: According to the on-site geological conditions, the rock samples in the mining area are tested to obtain the mechanical parameters of the rock samples; The mechanical parameters of the rock sample are set as the mechanical parameters of the similar material model, and the cementing material and aggregate of the similar material are selected based on the mechanical parameters of the similar material model; Similar material models were prepared using similar materials of binder and aggregate.

4. The crack tracking and pressure feedback physical simulation test method according to claim 2, characterized in that: The mechanical parameters include density, compressive strength, Poisson's ratio and elastic modulus.

5. The crack tracking and pressure feedback physical simulation test method according to claim 2, characterized in that: The specific steps include: Apply rock damage models to actual field work; deduce possible situations in actual fracturing operations based on complete fracture images and fracturing information, and conduct targeted optimization of fracturing operation design; Based on the fracturing information, it is determined whether the rock has tensile or shear failure, where the tensile failure variable is F s , the shear failure variable is F t ; F s =-σ3-f s0 (1) Among them, f s0 is the tensile strength of rock, f t0 is the uniaxial compressive strength of the rock, in MPa; σ1 and σ3 are the major and minor principal stresses of the rock, in MPa; the tensile direction is defined as negative; The damage variable D of rock is defined by using tensile failure variable and shear failure variable: Among them, ε s0 is the maximum tensile strain of rock, ε t0 is the maximum compressive strain of rock, in MPa; ε1 and ε3 are the major and minor principal strains of rock, and D is the damage variable of rock; Based on the elastic-plastic damage theory, a rock damage model is established: E=(1-D)E0 (4)In the formula, E is the real-time elastic modulus of rock, and E0 is the initial modulus of rock; The statistical method of rock failure area in similar material model is as follows: Import the tensile failure variables, shear failure variables, damage variables and rock damage modulus into the COMSOL numerical analysis program, define the tensile strength and uniaxial compression strength of the rock in the similar material model, input other rock parameters obtained from the indoor test into the COMSOL numerical analysis program, calculate the plastic deformation and failure curve of the similar material model, and obtain the damage factor D; The rock area with damage factor D greater than 0 is defined as the destruction area, and the area with damage factor D equal to 0 is defined as the non-destructive safety area; The obtained damage factor D is applied to actual field work, and the rock damage area is reflected by updating the rock elastic modulus in real time.

Images